Forests

18 pages, 3438 KiB

Open AccessArticle

Tree Biomass Equations from Terrestrial LiDAR: A Case Study in Guyana

by Alvaro Lau, Kim Calders, Harm Bartholomeus, Christopher Martius, Pasi Raumonen, Martin Herold, Matheus Vicari, Hansrajie Sukhdeo, Jeremy Singh and Rosa C. Goodman

Forests 2019, 10(6), 527; https://doi.org/10.3390/f10060527 - 25 Jun 2019

Cited by 47 | Viewed by 8541

Abstract

Large uncertainties in tree and forest carbon estimates weaken national efforts to accurately estimate aboveground biomass (AGB) for their national monitoring, measurement, reporting and verification system. Allometric equations to estimate biomass have improved, but remain limited. They rely on destructive sampling; large trees [...] Read more.

Large uncertainties in tree and forest carbon estimates weaken national efforts to accurately estimate aboveground biomass (AGB) for their national monitoring, measurement, reporting and verification system. Allometric equations to estimate biomass have improved, but remain limited. They rely on destructive sampling; large trees are under-represented in the data used to create them; and they cannot always be applied to different regions. These factors lead to uncertainties and systematic errors in biomass estimations. We developed allometric models to estimate tree AGB in Guyana. These models were based on tree attributes (diameter, height, crown diameter) obtained from terrestrial laser scanning (TLS) point clouds from 72 tropical trees and wood density. We validated our methods and models with data from 26 additional destructively harvested trees. We found that our best TLS-derived allometric models included crown diameter, provided more accurate AGB estimates (

R^{2}

= 0.92–0.93) than traditional pantropical models (

R^{2}

= 0.85–0.89), and were especially accurate for large trees (diameter > 70 cm). The assessed pantropical models underestimated AGB by 4 to 13%. Nevertheless, one pantropical model (Chave et al. 2005 without height) consistently performed best among the pantropical models tested (

R^{2}

= 0.89) and predicted AGB accurately across all size classes—which but for this could not be known without destructive or TLS-derived validation data. Our methods also demonstrate that tree height is difficult to measure in situ, and the inclusion of height in allometric models consistently worsened AGB estimates. We determined that TLS-derived AGB estimates were unbiased. Our approach advances methods to be able to develop, test, and choose allometric models without the need to harvest trees. Full article

(This article belongs to the Special Issue Remote Sensing Technology Applications in Forestry and REDD+)

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15 pages, 2063 KiB

Open AccessArticle

Reasons for the Extremely Small Population of putative hybrid Sonneratia × hainanensis W.C. Ko (Lythraceae)

by Mengwen Zhang, Xiaobo Yang, Wenxing Long, Donghai Li and Xiaobo Lv

Forests 2019, 10(6), 526; https://doi.org/10.3390/f10060526 - 25 Jun 2019

Cited by 4 | Viewed by 2975

Abstract

Sonneratia × hainanensis, a species once endemic to Hainan Island in China, is now endangered. China’s State Forestry Administration lists this species as a wild plant species with an extremely small population. Field fixed-point investigations, artificial pollination, and laboratory experiments, as well [...] Read more.

Sonneratia × hainanensis, a species once endemic to Hainan Island in China, is now endangered. China’s State Forestry Administration lists this species as a wild plant species with an extremely small population. Field fixed-point investigations, artificial pollination, and laboratory experiments, as well as other methods, were applied to study the reproductive system and seed germination of S. × hainanensis to elucidate the reasons for the endangerment of this species. The results are as follows: (1) Outcrossing index, pollen-ovule ratio, and artificial pollination showed S. × hainanensis has a mixed mating system and mainly focuses on outcrossing with some self-compatibility. (2) Fruit and seed placement tests showed that the fruit predators on the ground were mainly Fiddler crab and squirrel, with the predation rates being 100%. The artificially spread seeds do not germinate under natural conditions. The mean seed destruction rate and remaining rate of were 82.5% and 17.5%. (3) Seeds need to germinate under ambient light conditions, with an optimal photoperiod of 12 h. Seed germination is extremely sensitive to low temperatures because of optimum temperatures from 30 °C to 40 °C. At an optimal temperature of 35 °C, the seeds germinate under salinities ranging from 0‰ to 7.5‰, with an optimal salinity of 2.5‰, which shows the sensitivity of seed germination to salinity, with low salinity promoting germination, whereas high salinity inhibits germination. These findings indicate that the limited regeneration of S. × hainanensis is caused by the following: (1) Pollen limitation and inbreeding recession caused by the extremely small population of S. × hainanensis. (2) Seeds near parent trees are susceptible not only to high fruit drop rate, but to high predation beneath the parent trees′ canopy as well. (3) Seed germination has weak adaptability to light, temperature, and salinity. Full article

(This article belongs to the Special Issue Relationship between Forest Ecophysiology and Environment)

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16 pages, 2557 KiB

Open AccessArticle

Construction of Wood-Based Lamella for Increased Load on Seating Furniture

by Nadežda Langová, Roman Réh, Rastislav Igaz, Ľuboš Krišťák, Miloš Hitka and Pavol Joščák

Forests 2019, 10(6), 525; https://doi.org/10.3390/f10060525 - 25 Jun 2019

Cited by 28 | Viewed by 5216

Abstract

The research on population shows that the count of overweight people has been constantly growing. Therefore, designing and modifying utility items, e.g., furniture should be brought into focus. Indeed, furniture function and safety is associated with the weight of a user. Current processes [...] Read more.

The research on population shows that the count of overweight people has been constantly growing. Therefore, designing and modifying utility items, e.g., furniture should be brought into focus. Indeed, furniture function and safety is associated with the weight of a user. Current processes and standards dealing with the design of seating furniture do not meet the requirements of overweight users. The research is aimed at designing flexible chairs consisting of lamellae using the finite element method (FEM). Three types of glued lamellae based on wood with different number of layers and thickness were made and subsequently, their mechanical properties were tested. Values for modulus of elasticity and modulus of rupture were used to determine stress and deformation applying the FEM method for modelling flexible chairs. In this research, the methodology for evaluating the ultimate state of flexible chairs used to analyse deformation and stability was defined. The analysis confirms that several designed constructions meet the requirements of actual standards (valid for the weight of a user up to 110 kg) but fail to meet the requirements for weight gain of a population. Full article

(This article belongs to the Special Issue Wood Properties and Processing)

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17 pages, 3614 KiB

Open AccessArticle

Drivers of Wildfire Occurrence Patterns in the Inland Riverine Environment of New South Wales, Australia

by Yang Zhang and Samsung Lim

Forests 2019, 10(6), 524; https://doi.org/10.3390/f10060524 - 24 Jun 2019

Cited by 5 | Viewed by 3862

Abstract

In the inland riverine environment of Australia, wildfires not only threaten human life and cause economic loss but also make distinctive impacts on the ecosystem (e.g., injuring or killing fire-sensitive wetland species such as the river red gum). Understanding the drivers of wildfire [...] Read more.

In the inland riverine environment of Australia, wildfires not only threaten human life and cause economic loss but also make distinctive impacts on the ecosystem (e.g., injuring or killing fire-sensitive wetland species such as the river red gum). Understanding the drivers of wildfire occurrence patterns in this particular environment is vital for fire-risk reduction and ecologically sustainable management. This study investigated patterns and driving factors of wildfire occurrence over the years from 2001 to 2016 and across the New South Wales side of the Riverina bioregion. Descriptive analyses were conducted for fires of different causes and that burned different vegetation types. Logistic regression models were developed by incorporating factors that provide information on weather, climate, fuel, topography and ignition sources. Analyses revealed that most fires occurred in summer, with human-caused fires primarily in spring and summer, and natural fires in summer. Summer was the most fire-prone season in forested wetlands, whereas fires in drylands mostly occurred during spring and summer. Fire probabilities were higher under severe weather conditions, in areas with higher annual rainfall, in forested wetlands and in areas with intermediate inundation frequencies. Special attention needs to be paid to the effects of vegetation type and inundation frequency on fire occurrence. Weather, climate&fuel and ignition sources were comparably important in explaining human-caused fire occurrence, whereas weather was more important than climate&fuel in explaining natural fire occurrence. Understandings obtained from this study can potentially support the planning of fire and forest management, as well as to supplement the relatively scarce knowledge on riverine wildfire occurrence. Full article

(This article belongs to the Special Issue Fire Effects and Management in Forests)

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17 pages, 2944 KiB

Open AccessArticle

Assessing Forest Ecosystems across the Vertical Edge of the Mid-Latitude Ecotone Using the BioGeoChemistry Management Model (BGC-MAN)

by Cholho Song, Stephan A. Pietsch, Moonil Kim, Sungeun Cha, Eunbeen Park, Anatoly Shvidenko, Dmitry Schepaschenko, Florian Kraxner and Woo-Kyun Lee

Forests 2019, 10(6), 523; https://doi.org/10.3390/f10060523 - 23 Jun 2019

Cited by 8 | Viewed by 3295

Abstract

The mid-latitude ecotone (MLE)—a transition zone between boreal and temperate forests, which includes the regions of Northeast Asia around 30°–60° N latitudes—delivers different ecosystem functions depending on different management activities. In this study, we assessed forest volume and net primary productivity changes in [...] Read more.

The mid-latitude ecotone (MLE)—a transition zone between boreal and temperate forests, which includes the regions of Northeast Asia around 30°–60° N latitudes—delivers different ecosystem functions depending on different management activities. In this study, we assessed forest volume and net primary productivity changes in the MLE of Northeast Asia under different ecological characteristics, as well as various current management activities, using the BioGeoChemistry Management Model (BGC-MAN). We selected five pilot sites for pine (Scots pine and Korean red pine; Pinus sylvestris and P. densiflora), oak (Quercus spp.), and larch forests (Dahurian larch and Siberian larch; Larix gmelinii and L. sibirica), respectively, which covered the transition zone across the MLE from Lake Baikal, Russia to Kyushu, Japan, including Mongolia, Northeast China, and the Korean Peninsula. With site-specific information, soil characteristics, and management descriptions by forest species, we established their management characteristics as natural preserved forests, degraded forests, sandy and cold forest stands, and forests exposed to fires. We simulated forest volume (m³) and net primary productivity (Mg C ha⁻¹) during 1960–2005 and compared the results with published literature. They were in the range of those specified in previous studies, with some site-levels under or over estimation, but unbiased estimates in their mean values for pine, oak, and larch forests. Annual rates of change in volume and net primary productivity differed by latitude, site conditions, and climatic characteristics. For larch forests, we identified a high mountain ecotype which warrants a separate model parameterization. We detected changes in forest ecosystems, explaining ecological transition in the Northeast Asian MLE. Under the transition, we need to resolve expected problems through appropriate forest management and social efforts. Full article

(This article belongs to the Special Issue Cool Forests at risk? The Critical Role of Boreal and Mountain Ecosystems for People, Bioeconomy, and Climate)

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22 pages, 920 KiB

Open AccessReview

The Importance of Moisture for Brown Rot Degradation of Modified Wood: A Critical Discussion

by Rebecka Ringman, Greeley Beck and Annica Pilgård

Forests 2019, 10(6), 522; https://doi.org/10.3390/f10060522 - 23 Jun 2019

Cited by 44 | Viewed by 5176

Abstract

The effect of wood modification on wood-water interactions in modified wood is poorly understood, even though water is a critical factor in fungal wood degradation. A previous review suggested that decay resistance in modified wood is caused by a reduced wood moisture content [...] Read more.

The effect of wood modification on wood-water interactions in modified wood is poorly understood, even though water is a critical factor in fungal wood degradation. A previous review suggested that decay resistance in modified wood is caused by a reduced wood moisture content (MC) that inhibits the diffusion of oxidative fungal metabolites. It has been reported that a MC below 23%–25% will protect wood from decay, which correlates with the weight percent gain (WPG) level seen to inhibit decay in modified wood for several different kinds of wood modifications. In this review, the focus is on the role of water in brown rot decay of chemically and thermally modified wood. The study synthesizes recent advances in the inhibition of decay and the effects of wood modification on the MC and moisture relationships in modified wood. We discuss three potential mechanisms for diffusion inhibition in modified wood: (i) nanopore blocking; (ii) capillary condensation in nanopores; and (iii) plasticization of hemicelluloses. The nanopore blocking theory works well with cell wall bulking and crosslinking modifications, but it seems less applicable to thermal modification, which may increase nanoporosity. Preventing the formation of capillary water in nanopores also explains cell wall bulking modification well. However, the possibility of increased nanoporosity in thermally modified wood and increased wood-water surface tension for 1.3-dimethylol-4.5-dihydroxyethyleneurea (DMDHEU) modification complicate the interpretation of this theory for these modifications. Inhibition of hemicellulose plasticization fits well with diffusion prevention in acetylated, DMDHEU and thermally modified wood, but plasticity in furfurylated wood may be increased. We also point out that the different mechanisms are not mutually exclusive, and it may be the case that they all play some role to varying degrees for each modification. Furthermore, we highlight recent work which shows that brown rot fungi will eventually degrade modified wood materials, even at high treatment levels. The herein reviewed literature suggests that the modification itself may initially be degraded, followed by an increase in wood cell wall MC to a level where chemical transport is possible. Full article

(This article belongs to the Special Issue Wood-Moisture Relations)

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10 pages, 1092 KiB

Open AccessArticle

Susceptibility of Small-Diameter Norway Spruce Understory Stumps to Heterobasidion Spore Infection

by Tālis Gaitnieks, Astra Zaļuma, Kristīne Kenigsvalde, Dārta Kļaviņa, Indulis Brauners and Tuula Piri

Forests 2019, 10(6), 521; https://doi.org/10.3390/f10060521 - 22 Jun 2019

Cited by 5 | Viewed by 2791

Abstract

Heterobasidion spp. cause economically important losses in conifer forests in the Northern Hemisphere, especially in Norway spruce stands. Freshly cut stumps are the main route for Heterobasidion spp. infection. Even small stumps of spruce seedlings are known to be susceptible to spore infection, [...] Read more.

Heterobasidion spp. cause economically important losses in conifer forests in the Northern Hemisphere, especially in Norway spruce stands. Freshly cut stumps are the main route for Heterobasidion spp. infection. Even small stumps of spruce seedlings are known to be susceptible to spore infection, however, very little is currently known about the susceptibility of small stumps of understory spruce to Heterobasidion spore infection. To determine the frequency of spore infections among stumps of understory trees, we analyzed 756 Norway spruce stumps in eight sample plots in eastern Latvia. Understory trees 35–68 years of age, with a stump diameter of 2–10 cm, were felled 33–48 weeks before sampling. In total, 514 (68%) of the spruce stumps were infected by Heterobasidion spores. The infection frequency among the plots varied from 56% to 86%. Both infection frequency and stump surface area occupied by Heterobasidion positively correlated with stump diameter, but neither correlated with the time span elapsed between felling and sampling. Colonization of trees by a competitor fungus, Phlebiopsis gigantea (Fr.) Jülich, was observed in 30 (4%) of investigated stumps, but did not have any effect on the frequency of Heterobasidion infections. Our data show that Norway spruce stumps can be highly susceptible to Heterobasidion spore infection. In order to control airborne Heterobasidion infections, stump treatment should be considered during the sporulation period of Heterobasidion spp. Full article

(This article belongs to the Section Forest Ecophysiology and Biology)

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18 pages, 21405 KiB

Open AccessArticle

Exploring the Concept of Lineage Diversity across North American Forests

by Kyle G. Dexter, Ricardo A. Segovia and Andy R. Griffiths

Forests 2019, 10(6), 520; https://doi.org/10.3390/f10060520 - 22 Jun 2019

Cited by 3 | Viewed by 3679

Abstract

Lineage diversity can refer to the number of genetic lineages within species or to the number of deeper evolutionary lineages, such as genera or families, within a community or assemblage of species. Here, we study the latter, which we refer to as assemblage [...] Read more.

Lineage diversity can refer to the number of genetic lineages within species or to the number of deeper evolutionary lineages, such as genera or families, within a community or assemblage of species. Here, we study the latter, which we refer to as assemblage lineage diversity (ALD), focusing in particular on its richness dimension. ALD is of interest to ecologists, evolutionary biologists, biogeographers, and those setting conservation priorities, but despite its relevance, it is not clear how to best quantify it. With North American tree assemblages as an example, we explore and compare different metrics that can quantify ALD. We show that both taxonomic measures (e.g., family richness) and Faith’s phylogenetic diversity (PD) are strongly correlated with the number of lineages in recent evolutionary time, but have weaker correlations with the number of lineages deeper in the evolutionary history of an assemblage. We develop a new metric, time integrated lineage diversity (TILD), which serves as a useful complement to PD, by giving equal weight to old and recent lineage diversity. In mapping different ALD metrics across the contiguous United States, both PD and TILD reveal high ALD across large areas of the eastern United States, but TILD gives greater value to the southeast Coastal Plain, southern Rocky Mountains and Pacific Northwest, while PD gives relatively greater value to the southern Appalachians and Midwest. Our results demonstrate the value of using multiple metrics to quantify ALD, in order to highlight areas of both recent and older evolutionary diversity. Full article

(This article belongs to the Special Issue Causes and Consequences of Species Diversity in Forest Ecosystems)

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13 pages, 1651 KiB

Open AccessArticle

Eucalyptus Short-Rotation Management Effects on Nutrient and Sediments in Subtropical Streams

by Carolina Bozetti Rodrigues, Ricardo Hideo Taniwaki, Patrick Lane, Walter de Paula Lima and Silvio Frosini de Barros Ferraz

Forests 2019, 10(6), 519; https://doi.org/10.3390/f10060519 - 20 Jun 2019

Cited by 16 | Viewed by 2541

Abstract

Forested catchments generally present conserved aquatic ecosystems without anthropogenic disturbances; however, forest management operations can degrade these environments, including their water quality. Despite the potential degradation, few studies have analyzed the effects of forest management in subtropical regions, especially in forest plantations with [...] Read more.

Forested catchments generally present conserved aquatic ecosystems without anthropogenic disturbances; however, forest management operations can degrade these environments, including their water quality. Despite the potential degradation, few studies have analyzed the effects of forest management in subtropical regions, especially in forest plantations with intensive management, such as Eucalyptus plantations in Brazil. The intensive management of those plantations is characterized by fast-growing, short rotation cycles, and high productivity. This study aimed to assess the effects of Eucalyptus plantations harvesting on the concentration and exportation of nutrients and suspended solids in subtropical streams. Results showed that clear-cut harvesting and subsequent forest management operations do not alter most of the concentration of nitrate, potassium, calcium, and magnesium. The concentration of suspended solids increased during the first year after timber harvesting in all studied catchments, however, the increases were statistically significant in only two catchments. In the first year after harvest, it was observed an increment of water yield/precipitation ratio at three catchments, which also increased export of nutrients and suspended solids. Our results showed that harvesting of fast-growing Eucalyptus forest plantations partially affected sediment exports and did not compromise water quality in the studied catchments. However, the catchment land-use design, especially related to road density and land-use composition, showed significant relationship with sediment exportation. Full article

(This article belongs to the Special Issue Managing Forests and Water for People under a Changing Environment)

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30 pages, 10033 KiB

Open AccessArticle

Assessing Landscape Fire Hazard by Multitemporal Automatic Classification of Landsat Time Series Using the Google Earth Engine in West-Central Spain

by Natalia Quintero, Olga Viedma, Itziar R. Urbieta and José M. Moreno

Forests 2019, 10(6), 518; https://doi.org/10.3390/f10060518 - 20 Jun 2019

Cited by 24 | Viewed by 5341

Abstract

Annual Land Use and Land Cover (LULC) maps are needed to identify the interaction between landscape changes and wildland fires. Objectives: In this work, we determined fire hazard changes in a representative Mediterranean landscape through the classification of annual LULC types and fire [...] Read more.

Annual Land Use and Land Cover (LULC) maps are needed to identify the interaction between landscape changes and wildland fires. Objectives: In this work, we determined fire hazard changes in a representative Mediterranean landscape through the classification of annual LULC types and fire perimeters, using a dense Landsat Time Series (LTS) during the 1984–2017 period, and MODIS images. Methods: We implemented a semiautomatic process in the Google Earth Engine (GEE) platform to generate annual imagery free of clouds, cloud shadows, and gaps. We compared LandTrendr (LT) and FormaTrend (FT) algorithms that are widely used in LTS analysis to extract the pixel tendencies and, consequently, assess LULC changes and disturbances such as forest fires. These algorithms allowed us to generate the following change metrics: type, magnitude, direction, and duration of change, as well as the prechange spectral values. Results and conclusions: Our results showed that the FT algorithm was better than the LT algorithm at detecting low-severity changes caused by fires. Likewise, the use of the change metrics’ type, magnitude, and direction of change increased the accuracy of the LULC maps by 4% relative to the ones obtained using only spectral and topographic variables. The most significant hazardous LULC change processes observed were: deforestation and degradation (mainly by fires), encroachment (i.e., invasion by shrublands) due to agriculture abandonment and forest fires, and hazardous densification (from open forests and agroforestry areas). Although the total burned area has decreased significantly since 1985, the landscape fire hazard has increased since the second half of the twentieth century. Therefore, it is necessary to implement fire management plans focused on the sustainable use of shrublands and conifer forests; this is because the stability in these hazardous vegetation types is translated into increasing fuel loads, and thus an elevated landscape fire hazard. Full article

(This article belongs to the Special Issue Application of Remote Sensing on Fire Ecology)

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12 pages, 1829 KiB

Open AccessArticle

Tree Willow Root Growth in Sediments Varying in Texture

by Ian McIvor and Valérie Desrochers

Forests 2019, 10(6), 517; https://doi.org/10.3390/f10060517 - 19 Jun 2019

Cited by 2 | Viewed by 3049

Abstract

We investigated the early root development of Salix nigra L. willow grown from cuttings in the different riverbank sediments; silt, sand and stones. Cuttings were grown for 10 weeks in layered sediment types in five large planter boxes, each box having three separate [...] Read more.

We investigated the early root development of Salix nigra L. willow grown from cuttings in the different riverbank sediments; silt, sand and stones. Cuttings were grown for 10 weeks in layered sediment types in five large planter boxes, each box having three separate compartments. The boxes differed in the proportion of silt, sand and stones. At 10 weeks, the roots were extracted and sorted into diameter classes (≥2 mm; 1 < 2 mm; <1 mm) according to sediment type and depth. Root length and dry mass were measured and root length density (RLD) and root mass density (RMD) calculated. Root development of S. nigra cuttings varied with the substrate, either silt, sand or stones. Roots initiated from the entire length of the cutting in the substrate but with a concentration of initials located at the bottom and close to the bottom of the cutting. There was substantial root extension into all three substrates and at all depths. Generally, RMD was higher in the stones, influenced by having the bottom of the cuttings in stones for four of the five treatments. RMD was highest for roots <1 mm diameter. RMD of roots <1 mm diameter was least for those roots growing in sand. Whereas RLD for roots >0.5 mm diameter was highest in the sand, RLD of roots with diameter <0.5 mm was lowest in sand. Roots of S. nigra cuttings were least effective in binding sand, primarily because of low RLD of roots <0.5 mm diameter. It is surmised that sand lacks water and nutrients sufficient to sustain growth of fine roots compared with silt and even stones. RLD for roots >0.5 mm diameter was lowest in silt likely due to the greater resistance of the substrate to root penetration, or possibly the greater investment into smaller roots with absorption capability. Full article

(This article belongs to the Special Issue Short Rotation Woody Crop Production Systems for Ecosystem Services and Phytotechnologies)

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10 pages, 2026 KiB

Open AccessArticle

Orthotropic Tension Behavior of Two Typical Chinese Plantation Woods at Wide Relative Humidity Range

by Bingbin Kuai, Xuan Wang, Chao Lv, Kang Xu, Yaoli Zhang and Tianyi Zhan

Forests 2019, 10(6), 516; https://doi.org/10.3390/f10060516 - 19 Jun 2019

Cited by 7 | Viewed by 2386

Abstract

Research Highlights: Orthotropic tension behaviors of poplar and Chinese fir were investigated at a wide relative humidity (RH) range. Background and Objectives: Poplar and Chinese fir are typical plantation tree species in China. Mechanical properties of plantation-grown wood varies from naturally-grown one. To [...] Read more.

Research Highlights: Orthotropic tension behaviors of poplar and Chinese fir were investigated at a wide relative humidity (RH) range. Background and Objectives: Poplar and Chinese fir are typical plantation tree species in China. Mechanical properties of plantation-grown wood varies from naturally-grown one. To utilize poplar and Chinese fir woods efficiently, fully understanding their moisture content (MC) and orthotropic dependency on tension abilities is necessary. Materials and Methods: Plantation poplar and Chinese fir wood specimens were prepared and conditioned in series RH levels (0–100%). Tensile modulus (E) and strength (σ) were tested in longitudinal (L), radial (R), and tangential (T) directions. Results: The E and σ results in transverse directions confirmed the general influence of the MC that decreased with increasing MC. However, both E and σ in L direction showed a trend that increased at first, and then decreased when MC increased. The local maximums of stiffness and strength may be associated with straightened non-crystalline cellulose, induced by the penetration of water into the wood cell wall. Using the visualization method for compliance, the tension abilities of poplar and Chinese fir exhibited clear moisture and orthotropic dependency. Conclusion: Both poplar and Chinese fir showed a significantly higher degree of anisotropy in the L, R, and T directions. The results in this study provided first-hand data for wooden construction and wood drying. Full article

(This article belongs to the Special Issue Wood Properties and Processing)

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15 pages, 2765 KiB

Open AccessArticle

Growth Response of Sessile Oak and European Hornbeam to Traditional Coppice-with-Standards Management

by Jan Kadavý, Zdeněk Adamec, Barbora Uherková, Michal Kneifl, Robert Knott, Aleš Kučera, Michal Friedl, Eva Dařenová, Jiří Skládanka and Karel Drápela

Forests 2019, 10(6), 515; https://doi.org/10.3390/f10060515 - 19 Jun 2019

Cited by 4 | Viewed by 3010

Abstract

Research Highlights: The influence of litter raking and livestock grazing on the development of juvenile sessile oak and European hornbeam sprouts as well as on sessile oak standards were studied. Such experiments are very rare, especially in central Europe where these activities have [...] Read more.

Research Highlights: The influence of litter raking and livestock grazing on the development of juvenile sessile oak and European hornbeam sprouts as well as on sessile oak standards were studied. Such experiments are very rare, especially in central Europe where these activities have been prohibited for several decades. Little is known on how these ancient management activities affect tree growth. Background and Objectives: Traditional management practices in coppice forests such as grazing and litter raking have been abandoned, but have recently been studied as to whether these practices can substantially contribute to an increase in the species diversity of coppices. The important question is, however, how these practices influence the growth of coppice-with-standards. Therefore, this study focused on the effect of grazing, litter raking, and their combination on both sprouts and adult trees in a coppice-with-standards system one year after harvest. Materials and Methods: The experiment was carried out in the area of the Training Forest Enterprise Masaryk Forest Křtiny, Czech Republic, in a forest stand dominated by sessile oak and European hornbeam. We analyzed 132 oak polycormons, 132 hornbeam polycormons, and 163 oak standards. Results: The number of sprouts per stump was affected by the stump size and management practice: (A) coppice-with-standards, litter raking, and sheep grazing; (B) coppice-with-standards and sheep grazing; (C) coppice-with-standards and litter raking; and (D) coppice-with-standards), but not by tree species. The number of the sprouts as well as their height increased with the stump size. In contrast, grazing resulted in a smaller height of the sprouts while thinner sprouts were found under a combination of grazing and raking. When comparing the species, the oak sprouts were higher and thicker when compared to the hornbeam sprouts. The increment of standards increased after stand harvest. This, however, was not the result of grazing or raking, but the response to the reduction of tree number and thus of competition between neighboring trees. Conclusions: The results showed that there were rather negative impacts from the implemented traditional management practices on the growth of sprouts. This may lead to the question of whether ecological diversity resulting from the traditional practices may prevail their negative effect on the growth of the coppices. Full article

(This article belongs to the Section Forest Ecology and Management)

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17 pages, 5515 KiB

Open AccessArticle

Physiological and Growth Responses to Increasing Drought of an Endangered Tree Species in Southwest China

by Wuji Zheng, Xiaohua Gou, Jiajia Su, Haowen Fan, Ailing Yu, Wenhuo Liu, Yang Deng, Rubén D. Manzanedo and Patrick Fonti

Forests 2019, 10(6), 514; https://doi.org/10.3390/f10060514 - 17 Jun 2019

Cited by 10 | Viewed by 3195

Abstract

Research Highlights: We compared annually resolved records of tree-ring width and stable isotope of dead and surviving Fokienia hodginsii (Dunn) Henry et Thomas trees. We provide new insights into the relationships and sensitivity of tree growth to past and current climate, and explored [...] Read more.

Research Highlights: We compared annually resolved records of tree-ring width and stable isotope of dead and surviving Fokienia hodginsii (Dunn) Henry et Thomas trees. We provide new insights into the relationships and sensitivity of tree growth to past and current climate, and explored the underlying mechanism of drought-induced mortality in F. hodginsii. Background and Objectives: Drought-induced tree decline and mortality are increasing in many regions around the world. Despite the high number of studies that have explored drought-induced decline, species-specific responses to drought still makes it difficult to apply general responses to specific species. The endangered conifer species, Fokienia hodginsii, has experienced multiple drought-induced mortality events in recent years. Our objective was to investigate the historical and current responses to drought of this species. Materials and Methods: We used annually resolved ring-width and δ¹³C chronologies to investigate tree growth and stand physiological responses to climate change and elevated CO₂ concentration (C_a) in both dead and living trees between 1960 and 2015. Leaf intercellular CO₂ concentration (C_i), C_i/C_a and intrinsic water-use efficiency (iWUE) were derived from δ¹³C. Results: δ¹³C were positively correlated with mean vapor pressure deficit and PDSI from previous October to current May, while ring widths were more sensitive to climatic conditions from previous June to September. Moreover, the relationships between iWUE, basal area increment (BAI), and C_i/C_a changed over time. From 1960s to early 1980s, BAI and iWUE maintained a constant relationship with increasing atmospheric CO₂ concentration. After the mid-1980s, we observed a decrease in tree growth, increase in the frequency of missing rings, and an unprecedented increase in sensitivity of ¹³C and radial growth to drought, likely related to increasingly dry conditions. Conclusions: We show that the recent increase in water stress is likely the main trigger for the unprecedented decline in radial growth and spike in mortality of F. hodginsii, which may have resulted from diminished carbon fixation and water availability. Given that the drought severity and frequency in the region is expected to increase in the future, our results call for effective mitigation strategies to maintain this endangered tree species. Full article

(This article belongs to the Special Issue Influence of Climate Change on Tree Growth and Forest Ecosystems)

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15 pages, 3030 KiB

Open AccessArticle

Diurnal and Seasonal Variations in Soil Respiration of Four Plantation Forests in an Urban Park

by Mengxun Zhu, Wanlai Xue, Hang Xu, Yuan Gao, Shengnan Chen, Bin Li and Zhiqiang Zhang

Forests 2019, 10(6), 513; https://doi.org/10.3390/f10060513 - 17 Jun 2019

Cited by 9 | Viewed by 2943

Abstract

Understanding the carbon dynamics of urban trees and forests is one of the key components for developing mitigation strategies for climate change in a fast-paced urbanized world. This study selected four plantation forests composed of poplar, black locust, Chinese pine and mixture of [...] Read more.

Understanding the carbon dynamics of urban trees and forests is one of the key components for developing mitigation strategies for climate change in a fast-paced urbanized world. This study selected four plantation forests composed of poplar, black locust, Chinese pine and mixture of poplar and black locust, located in an urban forest park on a well-drained fluvial plain with same land-use history. The diurnal and seasonal changes in soil respiration (Rs) and biophysical factors were measured from April 2015 to March 2016. At the diurnal scale, Rs varied out of phase with soil temperature (Ts) and the time-lag occurred in May and July when Ts was relatively high and soil moisture (Ms) was low. Strong seasonal variations in Rs were mainly determined by Ts, while the growing-season mean Rs positively correlated with the fine root biomass (FRB), soil organic carbon content (SOC), and total nitrogen content (TN) for all the forests. FRB alone could explain 75% of the among-stand variability. This study concluded that urban forest plantations have similar soil respiration dynamics to forest ecosystems in non-urban settings. Full article

(This article belongs to the Section Forest Ecology and Management)

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15 pages, 3230 KiB

Open AccessArticle

What (De)Motivates Forest Users’ Participation in Co-Management? Evidence from Nepal

by Jude Ndzifon Kimengsi, Prabin Bhusal, Anisha Aryal, Maria Vio Bianca Coronel Fernandez, Raphael Owusu, Anand Chaudhary and Wicki Nielsen

Forests 2019, 10(6), 512; https://doi.org/10.3390/f10060512 - 16 Jun 2019

Cited by 25 | Viewed by 5531

Abstract

The co-management concept has been echoed in scientific literature for over two decades. Emphasis has been tailored towards an understanding of structural and functional issues linked to its application and the outcomes thereof. However, a crucial aspect which still begs for scientific and [...] Read more.

The co-management concept has been echoed in scientific literature for over two decades. Emphasis has been tailored towards an understanding of structural and functional issues linked to its application and the outcomes thereof. However, a crucial aspect which still begs for scientific and policy edification, concerns the motivational drivers of actors’ participation in co-management arrangements. Studies contend that actors are motivated to participate in co-management based on their perceived benefits (e.g., income). Conclusions from these lines of argument further raise a theoretical quagmire, requiring further grounding, with regards to context-specific (de)motivators of users’ participation in co-management. The case of Nepal is pertinent. Although Nepal has a rich community-based forest management history, scientific investigations have virtually ignored the motivational drivers of participation in the co-management of natural resources (forests). Against this background, this paper seeks to explore the following: (i) the decision-making and monitoring structure of rules regulating the co-management of forests, (ii) the implications of this system on users’ motivation to participate, and (iii) the motivational drivers of users’ participation in co-management. To achieve this, five focus group discussions and 10 key informant interviews were conducted in five villages (Kunjo, Titi, Parshyang, Cchayo, and Taglung) within the Annapurna Conservation Area (ACA). We further employed narratives, framework, and thematic analyses to discuss the decision-making structure and motivational aspects of co-management. The results point to the following conclusions: (1) Despite the rather top-down decision-making setting, users remain motivated to participate in co-management. (2) Interestingly, the motivation by actors to participate is not largely driven by users’ perceived benefits. The results present another twist, a deviation from the previously understood rationale, which should be factored into co-management theory development. However, the paper equally makes a succinct request for further studies, including quantitative investigations, to ground this assertion. Full article

(This article belongs to the Special Issue Protected Areas in Forest Conservation: Challenges and Opportunities)

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22 pages, 5392 KiB

Open AccessArticle

Responses to Drought in Seedlings of European Larch (Larix decidua Mill.) from Several Carpathian Provenances

by Ioana M. Plesa, Mohamad Al Hassan, Sara González-Orenga, Adriana F. Sestras, Oscar Vicente, Jaime Prohens, Monica Boscaiu and Radu E. Sestras

Forests 2019, 10(6), 511; https://doi.org/10.3390/f10060511 - 16 Jun 2019

Cited by 5 | Viewed by 3381

Abstract

European larch (Larix decidua Mill.) has been reported either as more tolerant or as more sensitive to drought than conifers with perennial leaves. Previous studies have revealed that Carpathian populations of European larch display a high genetic variability. A comparative study of [...] Read more.

European larch (Larix decidua Mill.) has been reported either as more tolerant or as more sensitive to drought than conifers with perennial leaves. Previous studies have revealed that Carpathian populations of European larch display a high genetic variability. A comparative study of the responses of these populations to drought stress at the seedling stage might allow the identification of drought tolerant genotypes and reliable drought stress biomarkers, which could be eventually used for the early detection of drought effects in larch, not only under control greenhouse conditions, but also in their natural stands. Growth responses were analyzed in larch seedlings from six Romanian Carpathian populations, submitted to one month of mild drought stress under controlled conditions. Levels of photosynthetic pigments (chlorophylls a and b, and carotenoids), osmolytes (proline and total soluble sugars), monovalent cations (Na⁺ and K⁺), and malondialdehyde (MDA) and non-enzymatic antioxidants (total phenolics and flavonoids) were compared with control treatments and between populations. Growth and the pattern of the biochemical responses were very similar in the six populations. Drought stress lead to stem length decrease in all population, whereas reduction of fresh weight of needles was significant only in one population (BVVC), and reduction of water content of needles in two populations (BVVC and GuHo). The optimal biochemical traits for an early detection of drought symptoms in this species is the increase—in most populations—of total soluble sugars, MDA, and total phenolic compounds, whereas K⁺ reduction was significant in all populations. Photosynthetic pigments remained unchanged, except for the Anin population where they were reduced under stress. Multivariate principal component and hierarchical clustering analyses confirmed the impact of drought in the growth and physiology of European larch, and revealed that the humidity of the substrate was positively correlated with the growth parameters and the levels of K⁺ in needles, and negatively correlated with the levels of MDA, total soluble sugars, total phenolic compounds, and flavonoids in needles. Full article

(This article belongs to the Section Forest Ecophysiology and Biology)

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17 pages, 1951 KiB

Open AccessArticle

Land Restoration in Latin America and the Caribbean: An Overview of Recent, Ongoing and Planned Restoration Initiatives and Their Potential for Climate Change Mitigation

by Erika Romijn, Ruben Coppus, Veronique De Sy, Martin Herold, Rosa Maria Roman-Cuesta and Louis Verchot

Forests 2019, 10(6), 510; https://doi.org/10.3390/f10060510 - 15 Jun 2019

Cited by 31 | Viewed by 9992

Abstract

Land degradation is a globally recognized problem and restoration of degraded land is currently high on the international agenda. Forest landscape restoration and other restorative ecosystem management activities are important measures that contribute towards reaching the objectives of the Bonn Challenge, which aims [...] Read more.

Land degradation is a globally recognized problem and restoration of degraded land is currently high on the international agenda. Forest landscape restoration and other restorative ecosystem management activities are important measures that contribute towards reaching the objectives of the Bonn Challenge, which aims to restore 350 million hectares by 2030. In this context, many restoration projects are being planned and implemented in Latin America and the Caribbean (LAC). We present an overview of the location, goals and activities, and an estimated climate change mitigation potential of 154 recent, ongoing and planned restoration projects in LAC. Our analysis suggests that most projects are located in the humid tropics and less attention is paid to drylands. Increasing vegetation cover, biodiversity recovery and recovery of ecological processes are the most common goals. Restorative activities to fulfil these goals were diverse and were related to the type and source of funding that projects receive. For example, projects implemented through the Forest Investment Program (FIP) and the Global Environment Facility (GEF) generally rely on natural or assisted regeneration over large areas (>20,000 ha), whereas Clean Development Mechanism (CDM) projects establish forest plantations, often including exotic monocultures, in smaller project areas (<5000 ha). Projects that are specifically implemented within the scope of Initiative 20 × 20 and other local initiatives that target the local environmental problems, are more varied and rely on a wider portfolio of restorative activities, such as erosion control, exclusion of grazing and mixed plantations. These projects are usually implemented in smaller project areas (<5000 ha). All projects had the potential to contribute to climate change mitigation by storing additional forest aboveground biomass through natural regeneration, assisted regeneration or establishing a plantation. Further analysis of the implemented activities is an important next step to investigate their effectiveness in terms of goals achieved under Initiative 20 × 20 and the Bonn Challenge. This would provide information for future restoration projects and upscaling of restorative activities in a wider area. Full article

(This article belongs to the Special Issue Forest Landscape Restoration)

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15 pages, 7392 KiB

Open AccessArticle

Influence of Canopy Interception and Rainfall Kinetic Energy on Soil Erosion under Forests

by Guijing Li, Long Wan, Ming Cui, Bin Wu and Jinxing Zhou

Forests 2019, 10(6), 509; https://doi.org/10.3390/f10060509 - 15 Jun 2019

Cited by 48 | Viewed by 4494

Abstract

Afforestation is a widely accepted measure to control soil erosion around the world. A large area of forest has been built to prevent slope soil erosion in the red soil region of southern China since the 1980s. The vegetation coverage has significantly increased; [...] Read more.

Afforestation is a widely accepted measure to control soil erosion around the world. A large area of forest has been built to prevent slope soil erosion in the red soil region of southern China since the 1980s. The vegetation coverage has significantly increased; however, there is still moderate or severe soil erosion under the forest. In order to improve the situation, it is necessary to study the effects of canopy on soil erosion under the forest. Standard runoff plots were established on two typical sites, which represented pure Pinus massoniana Lamb. forest and bare land, respectively. Precipitation redistribution and throughfall indices including raindrop size, raindrop velocity, and the kinetic energy (KE) of raindrops were quantified. The results showed that 29.3% of the precipitation was directly prevented from reaching the forest land surface. The canopy interception effect was better under low rainfall intensity than high rainfall intensity. Compared with open rainfall, throughfall raindrops were 16.3% fewer in number, larger in size, and the range of throughfall drop size distribution (DSD) was enlarged. The volume ratio of large drops was larger with higher rainfall intensity. When the rainfall intensity was less than 14 mm h⁻¹, throughfall kinetic energy (TKE) was higher than open rainfall kinetic energy (OKE) owing to the higher volume ratio of large raindrops. When the rainfall intensity was more than 14 mm h⁻¹, TKE was smaller owing to the large raindrops failing to reach their final velocities: their mean velocity was 80% of their final velocity. The sediment yield was the largest under high rainfall intensity and the effect of sediment reduction was the largest under moderate rainfall intensity. Therefore, the largest KE did not lead to the maximum sediment yield; canopy interception was also an important factor affecting sediment yield. Full article

(This article belongs to the Section Forest Ecology and Management)

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16 pages, 2368 KiB

Open AccessReview

Effects of Climate Change at Treeline: Lessons from Space-for-Time Studies, Manipulative Experiments, and Long-Term Observational Records in the Central Austrian Alps

by Gerhard Wieser, Walter Oberhuber and Andreas Gruber

Forests 2019, 10(6), 508; https://doi.org/10.3390/f10060508 - 14 Jun 2019

Cited by 25 | Viewed by 4324

Abstract

This review summarizes the present knowledge about effects of climate change on conifers within the treeline ecotone of the Central Austrian Alps. After examining the treeline environment and the tree growth with respect to elevation, possible effects of climate change on carbon gain [...] Read more.

This review summarizes the present knowledge about effects of climate change on conifers within the treeline ecotone of the Central Austrian Alps. After examining the treeline environment and the tree growth with respect to elevation, possible effects of climate change on carbon gain and water relations derived from space-for-time studies and manipulative experiments are outlined. Finally, long-term observational records are discussed, working towards conclusions on tree growth in a future, warmer environment. Increases in CO₂ levels along with climate warming interact in complex ways on trees at the treeline. Because treeline trees are not carbon limited, climate warming (rather than the rising atmospheric CO₂ level) causes alterations in the ecological functioning of the treeline ecotone in the Central Austrian Alps. Although the water uptake from soils is improved by further climate warming due to an increased permeability of root membranes and aquaporin-mediated changes in root conductivity, tree survival at the treeline also depends on competitiveness for belowground resources. The currently observed seedling re-establishment at the treeline in the Central European Alps is an invasion into potential habitats due to decreasing grazing pressure rather than an upward-migration due to climate warming, suggesting that the treeline in the Central Austrian Alps behaves in a conservative way. Nevertheless, to understand the altitude of the treeline, one must also consider seedling establishment. As there is a lack of knowledge on this particular topic within the treeline ecotone in the Central Austrian Alps, we conclude further research has to focus on the importance of this life stage for evaluating treeline shifts and limits in a changing environment. Full article

(This article belongs to the Special Issue Alpine and Polar Treelines in a Changing Environment)

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13 pages, 2367 KiB

Open AccessArticle

Hydrochemical Fluxes in Bulk Precipitation, Throughfall, and Stemflow in a Mixed Evergreen and Deciduous Broadleaved Forest

by Lei Su, Changming Zhao, Wenting Xu and Zongqiang Xie

Forests 2019, 10(6), 507; https://doi.org/10.3390/f10060507 - 14 Jun 2019

Cited by 40 | Viewed by 5660

Abstract

Rainfall is one of the primary sources of chemical inputs in forest ecosystems, and the basis of forest nutrient cycling. Mixed evergreen and deciduous broadleaved forests are currently one of the most threatened ecosystems due to their sensitivity to anthropogenic climate change. As [...] Read more.

Rainfall is one of the primary sources of chemical inputs in forest ecosystems, and the basis of forest nutrient cycling. Mixed evergreen and deciduous broadleaved forests are currently one of the most threatened ecosystems due to their sensitivity to anthropogenic climate change. As such, understanding the hydrochemical fluxes of these systems is critical for managing their dynamics in the future. We investigate the chemistry of bulk precipitation, stemflow and throughfall in a mixed evergreen and deciduous broadleaved forest in the Shennongjia region of Central China. Mean nutrient concentrations in throughfall and stemflow were higher than in bulk precipitation. Stemflow ion fluxes from deciduous tree species were greater than those for evergreen tree species because of the differences in bark morphology and branch architecture. Throughfall and stemflow chemistry fluctuated dramatically over the growing season. Nitrate nitrogen and ammonium nitrogen were retained, while other elements and compounds were washed off or leached via throughfall and stemflow pathways. Our findings will facilitate a greater understanding of nutrient balance in canopy water fluxes. Full article

(This article belongs to the Section Forest Ecophysiology and Biology)

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23 pages, 4631 KiB

Open AccessArticle

Modeling Dynamics of Structural Components of Forest Stands Based on Trivariate Stochastic Differential Equation

by Petras Rupšys

Forests 2019, 10(6), 506; https://doi.org/10.3390/f10060506 - 14 Jun 2019

Cited by 14 | Viewed by 3423

Abstract

Research Highlights: Today’s approaches to modeling of forest stands are in most cases based on that the regression models and they are constructed as static sub-models describing individual stands variables. The disadvantages of this method; it is laborious because too many different equations [...] Read more.

Research Highlights: Today’s approaches to modeling of forest stands are in most cases based on that the regression models and they are constructed as static sub-models describing individual stands variables. The disadvantages of this method; it is laborious because too many different equations need to be assessed and empirical choices of candidate equations make the results subjective; it does not relate to the stand variables dynamics against the age dimension (time); and does not consider the underlying covariance structure driving changes in the stand variables. In this study, the dynamical model defined by a fixed-and mixed effect parameters trivariate stochastic differential equation (SDE) is introduced and described how such a model can be used to model quadratic mean diameter, mean height, number of trees per hectare, self-thinning line, stand basal area, stand volume per hectare and much more. Background and Objectives: New developed marginal and conditional trivariate probability density functions, combining information generated from an age-dependent variance-covariance matrix of quadratic mean diameter, mean height and number of trees per hectare, improve stand growth prediction, and forecast (in forecast the future is completely unavailable and must only be estimated from historical patterns) accuracies. Materials and Methods: Fixed-and mixed effect parameters SDE models were harmonized to predict and forecast the dynamics of quadratic mean diameter, mean height, number of trees per hectare, basal area, stand volume per hectare, and their current and mean increments. The results and experience from applying the SDE concepts and techniques in an extensive whole stand growth and yield analysis are described using a Scots pine (Pinus sylvestris L.) experimental dataset in Lithuania. Results: The mixed effects scenario SDE model showed high accuracy, the percentage root mean square error values for quadratic mean diameter, mean height, number of trees per hectare, stand basal area and stand volume per hectare predictions (forecasts) were 3.37% (10.44%), 1.82% (2.07%), 1.76% (2.93%), 6.65% (10.41%) and 6.50% (8.93%), respectively. In the same way, the quadratic mean diameter, mean height, number of trees per hectare, stand basal area and stand volume per hectare prediction (forecast) relationships had high values of the coefficient of determination, R², 0.998 (0.987), 0.997 (0.992), 0.997 (0.988), 0.968 (0.984) and 0.966 (0.980), respectively. Conclusions: The approach presented in this paper can be used for developing a new generation stand growth and yield models. Full article

(This article belongs to the Special Issue Modeling of Forest Structure and Dynamics)

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16 pages, 7784 KiB

Open AccessArticle

Juniper Tree-Ring Data from the Kuramin Range (Northern Tajikistan) Reveals Changing Summer Drought Signals in Western Central Asia

by Feng Chen, Tongwen Zhang, Andrea Seim, Shulong Yu, Ruibo Zhang, Hans W. Linderholm, Zainalobudin V. Kobuliev, Ahsan Ahmadov and Anvar Kodirov

Forests 2019, 10(6), 505; https://doi.org/10.3390/f10060505 - 14 Jun 2019

Cited by 17 | Viewed by 3529

Abstract

Coniferous forests cover the mountains in many parts of Central Asia and provide large potentials for dendroclimatic studies of past climate variability. However, to date, only a few tree-ring based climate reconstructions exist from this region. Here, we present a regional tree-ring chronology [...] Read more.

Coniferous forests cover the mountains in many parts of Central Asia and provide large potentials for dendroclimatic studies of past climate variability. However, to date, only a few tree-ring based climate reconstructions exist from this region. Here, we present a regional tree-ring chronology from the moisture-sensitive Zeravshan juniper (Juniperus seravschanica Kom.) from the Kuramin Range (Tajikistan) in western Central Asia, which is used to reveal past summer drought variability from 1650 to 2015 Common Era (CE). The chronology accounts for 40.5% of the variance of the June–July self-calibrating Palmer Drought Severity Index (scPDSI) during the instrumental period (1901 to 2012). Seven dry periods, including 1659–1696, 1705–1722, 1731–1741, 1758–1790, 1800–1842, 1860–1875, and 1931–1987, and five wet periods, including 1742–1752, 1843–1859, 1876–1913, 1921–1930, and 1988–2015, were identified. Good agreements between drought records from western and eastern Central Asia suggest that the PDSI records retain common drought signals and capture the regional dry/wet periods of Central Asia. Moreover, the spectral analysis indicates the existence of centennial (128 years), decadal (24.3 and 11.4 years), and interannual (8.0, 3.6, 2.9, and 2.0 years) cycles, which may be linked with climate forces, such as solar activity and El Niño-Southern Oscillation (ENSO). The analysis between the scPDSI reconstruction and large-scale atmospheric circulations during the reconstructed extreme dry and wet years can provide information about the linkages of extremes in our scPDSI record with the large-scale ocean–atmosphere–land circulation systems. Full article

(This article belongs to the Section Forest Ecophysiology and Biology)

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31 pages, 2641 KiB

Open AccessArticle

Coarse Woody Debris Management with Ambiguous Chance Constrained Robust Optimization

by Fabian Härtl and Thomas Knoke

Forests 2019, 10(6), 504; https://doi.org/10.3390/f10060504 - 13 Jun 2019

Cited by 8 | Viewed by 2796

Abstract

Coarse woody debris (deadwood) serves as a dwelling space for many rare species, and is therefore a most important factor to ensure diversity in forest ecosystems. However, wood from forest ecosystems is also needed for construction and heating. Therefore, a forest enterprise has [...] Read more.

Coarse woody debris (deadwood) serves as a dwelling space for many rare species, and is therefore a most important factor to ensure diversity in forest ecosystems. However, wood from forest ecosystems is also needed for construction and heating. Therefore, a forest enterprise has to simultaneously incorporate the provision of suitable habitats, as well as the production of wood into their long-term management plans. If the owner wants to fulfil such multiple objectives in an effective way, the providing of ecosystem services can be included in economic planning. Applying computer aided robust optimization techniques, we optimized the provision of deadwood for two exemplary enterprises in East Bavaria, Germany. The results show that high amounts of deadwood provision can cause severe opportunity costs for the forest owner. These costs highly depend on the tree species, the sorting strategy and the time horizon, in which the deadwood objective is reached. Low deadwood targets up to 5

m^{3} h a^{- 1}

can be provided most cost-effectively with crown material, while higher targets (20

m^{3} h a^{- 1}

and more) are better achieved with heavy timber grades or the provision of total trees. The novelty of our research is the inclusion of deadwood targets in a risk-considering optimization tool on enterprise level. Instead of calculating the economic loss of commercially not-used timber assortments we show a way of deriving the impact of such decisions at stand level on the economic performance of the whole forest enterprise. We were able to derive optimized opportunity costs. These costs can be used as guidelines for necessary incentives to encourage forest owners to incorporate the provision of deadwood into their management. Full article

(This article belongs to the Section Forest Economics, Policy, and Social Science)

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8 pages, 1183 KiB

Open AccessArticle

Influence of a Foliar Endophyte and Budburst Phenology on Survival of Wild and Laboratory-Reared Eastern Spruce Budworm, Choristoneura fumiferana on White Spruce (Picea glauca)

by Dan Quiring, Greg Adams, Leah Flaherty, Andrew McCartney, J. David Miller and Sara Edwards

Forests 2019, 10(6), 503; https://doi.org/10.3390/f10060503 - 13 Jun 2019

Cited by 5 | Viewed by 2429

Abstract

A manipulative field study was carried out to determine whether the foliar endophyte fungus, Phialocephala scopiformis DAOM 229536, decreased the performance of eastern spruce budworm, Choristoneura fumiferana larvae developing on white spruce trees. Overwintered second-instar budworm larvae from a laboratory colony or from [...] Read more.

A manipulative field study was carried out to determine whether the foliar endophyte fungus, Phialocephala scopiformis DAOM 229536, decreased the performance of eastern spruce budworm, Choristoneura fumiferana larvae developing on white spruce trees. Overwintered second-instar budworm larvae from a laboratory colony or from a wild population were placed on endophyte positive or negative trees one or two weeks before budburst. The presence of the endophyte in the needles reduced the survival of C. fumiferana from both a wild population and a laboratory colony. Survival for budworm juveniles up to pupation and to adult emergence was 13% and 17% lower, respectively, on endophyte positive trees. The endophyte did not influence the size or sex of survivors and budworm survival was not influenced by any two- or three-way interactions. Budworm survival was higher for wild than for laboratory-reared budworm and for budworm placed on trees a week before budburst. This may be the first field study to demonstrate the efficacy of an endophytic fungus against wild individuals of a major forest insect pest. The efficacy of the endophyte at low larval densities suggests that it could be a useful tactic to limit spruce budworm population growth in the context of an early intervention strategy. Full article

(This article belongs to the Special Issue Protection Strategy against Spruce Budworm)

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15 pages, 2195 KiB

Open AccessArticle

Presence of Mycorrhizal Fungal Hyphae Rather than Living Roots Retards Root Litter Decomposition

by Guigang Lin, Zhengxia Chen and De-Hui Zeng

Forests 2019, 10(6), 502; https://doi.org/10.3390/f10060502 - 13 Jun 2019

Cited by 9 | Viewed by 3910

Abstract

Although both living roots and mycorrhizal fungi are well known to interact with saprotrophic microbes to affect litter decomposition, their relative importance is largely unclear. Here, a two-year pot experiment was conducted with two ectomycorrhizal (Pinus elliottii and Pinus massoniana) and [...] Read more.

Although both living roots and mycorrhizal fungi are well known to interact with saprotrophic microbes to affect litter decomposition, their relative importance is largely unclear. Here, a two-year pot experiment was conducted with two ectomycorrhizal (Pinus elliottii and Pinus massoniana) and four arbuscular mycorrhizal (Cinnamomum camphora, Cunninghamia lanceolata, Michelia maudiae and Schima superba) subtropical tree species to evaluate the relative effects of living roots and mycorrhizal fungal hyphae on their own root litter decomposition and to test whether these effects differed between ectomycorrhizal and arbuscular mycorrhizal trees. To achieve these objectives, litterbags with 50-µm and 1-mm mesh sizes filled with root litter of a given tree species were simultaneously installed in pots planted with the same species and unplanted pots filled with composite soil for all species. Effects of living roots alone were calculated as differences in root litter decomposition between 50-µm and 1-mm mesh litterbags installed in planted pots. Mycorrhizal hyphal effects were calculated as differences in root litter decomposition between 50-µm litterbags installed in planted and unplanted pots. The presence of mycorrhizal fungal hyphae significantly reduced root litter mass loss and inhibited the activities of β-glucosidase and phenol oxidase, while effects of living roots alone were non-significant when all tree species were pooled and inconsistent at the tree species level. Mycorrhizal fungal hyphae induced decreases in root litter mass loss that were markedly related to their inhibitory effects on β-glucosidase and phenol oxidase activities. When tree species were grouped by their mycorrhizal types, non-significant differences were observed between ectomycorrhizal and arbuscular mycorrhizal trees in their living root or mycorrhizal fungal effects on root litter decomposition. These findings highlight the important roles of mycorrhizal fungi in mediating litter decomposition via interacting with saprotrophic microbes and suggest that changes in tree carbon allocation to mycorrhizal fungi owing to global change may affect soil carbon storage. Full article

(This article belongs to the Special Issue Forest Litter Decomposition: An Integrative Approach)

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15 pages, 3632 KiB

Open AccessArticle

The Northern White-Cedar Recruitment Bottleneck: Understanding the Effects of Substrate, Competition, and Deer Browsing

by Laura F. Reuling, Christel C. Kern, Laura S. Kenefic and Dustin R. Bronson

Forests 2019, 10(6), 501; https://doi.org/10.3390/f10060501 - 12 Jun 2019

Cited by 10 | Viewed by 2630

Abstract

Research Highlights: Regenerating northern white-cedar (Thuja occidentalis L.) is challenging throughout much of its range. This study attempts to relate differences in natural regeneration to stand- and seedbed-level factors. Background and Objectives: Lack of regeneration of northern white-cedar is often attributed to [...] Read more.

Research Highlights: Regenerating northern white-cedar (Thuja occidentalis L.) is challenging throughout much of its range. This study attempts to relate differences in natural regeneration to stand- and seedbed-level factors. Background and Objectives: Lack of regeneration of northern white-cedar is often attributed to overbrowsing by white-tailed deer (Odocoileus virginianus Zimmerman) because white-cedar is a preferred winter browse species. However, there are many other factors that may contribute to regeneration failure for white-cedar including its specific seedbed requirements and competition from other, often faster-growing trees and shrubs. Materials and Methods: We surveyed five mature white-cedar stands in Wisconsin, USA that have had little to no management in the past 50+ years to find stem densities of natural white-cedar regeneration in three height classes. We also collected data at each stand on potential predictor variables including overstory attributes, competitive environment, seedbed, and browsing by deer. We used model selection to create separate models to predict stem density of each white-cedar regeneration height class. Results: None of the measures of deer browsing used in this study were found to be associated with white-cedar regeneration. Soil pH, competition from other seedlings and saplings, and stem density of white-cedar in the overstory were found to be potentially associated with white-cedar regeneration. Conclusions: While browsing by deer is likely a factor affecting white-cedar regeneration in many areas, this study highlights the challenge of quantifying deer browse effects, as well as showing that other factors likely contribute to the difficulty of regenerating white-cedar. Full article

(This article belongs to the Section Forest Ecology and Management)

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16 pages, 3525 KiB

Open AccessArticle

Primary and Secondary Branch Growth in Black Spruce and Balsam Fir after Careful Logging around Small Merchantable Stems (CLASS)

by Audrey Lemay, Cornelia Krause and Alexis Achim

Forests 2019, 10(6), 500; https://doi.org/10.3390/f10060500 - 12 Jun 2019

Cited by 2 | Viewed by 2753

Abstract

Careful logging around small merchantable stems (CLASS) is a partial cutting treatment that consists of the harvest of 70%–90% of the merchantable volume of an irregular coniferous stand. In this treatment, regeneration, saplings and small merchantable stems (DBH < 15 cm) are preserved [...] Read more.

Careful logging around small merchantable stems (CLASS) is a partial cutting treatment that consists of the harvest of 70%–90% of the merchantable volume of an irregular coniferous stand. In this treatment, regeneration, saplings and small merchantable stems (DBH < 15 cm) are preserved and can continue to grow and develop into the dominant layer of the new stand. The aim of this project was to examine the effects of CLASS on the primary and secondary growth of branches, as well as on branch diameter in black spruce and balsam fir trees in the boreal forest of Quebec, Canada. Primary and secondary growth were measured on five branches per tree while branch diameter was analysed from 15 whorls distributed within the crown of the 48 black spruce and 48 balsam fir trees sampled. Branch primary and secondary growth significantly increased after CLASS in the lower part of the crown in both species, and both types of growth increased proportionally. These findings suggest that CLASS may delay crown recession as the lower branches tend to survive and grow for a longer period. However, although radial growth increased in the years post-CLASS, this did not significantly influence the final branch diameter and should not lead to lumber downgrade. Full article

(This article belongs to the Section Forest Ecology and Management)

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14 pages, 1806 KiB

Open AccessArticle

Early Successional Forest Management on Private Lands as a Coupled Human and Natural System

by Seth H. Lutter, Ashley A. Dayer, Amanda D. Rodewald, Darin J. McNeil and Jeffery L. Larkin

Forests 2019, 10(6), 499; https://doi.org/10.3390/f10060499 - 11 Jun 2019

Cited by 7 | Viewed by 3245

Abstract

Facilitating voluntary conservation on private lands is a crucial element of policies that seek to mitigate forest habitat loss and fragmentation around the world. Previous research emphasizes the role of social factors (e.g., landowner characteristics, economics) in forest management, but environmental outcomes of [...] Read more.

Facilitating voluntary conservation on private lands is a crucial element of policies that seek to mitigate forest habitat loss and fragmentation around the world. Previous research emphasizes the role of social factors (e.g., landowner characteristics, economics) in forest management, but environmental outcomes of past management can also affect landowner decisions. Our objective was to evaluate how positive outcomes for wildlife and habitat might reinforce or amplify landowner efforts to manage forest habitats. We applied the lens of coupled human and natural systems to investigate private lands management for early successional forests, which are declining along with associated wildlife in rural areas of the eastern U.S. Efforts to restore early successional forest in this region involve active forest management to create patches of successional forest in native, mature mixed hardwood stands. By integrating field-based monitoring of wildlife with surveys of landowner perceptions, we examined how landowners observed, interpreted, and responded to property-scale ecological outcomes of forest management. We recorded presence of Golden-winged Warbler (Vermivora chrysoptera) and American Woodcock (Scolopax minor) and estimated bird species richness in spring 2015 and/or 2016 on private properties located in the Appalachians (Maryland, New Jersey, Pennsylvania) and Upper Great Lakes (Minnesota, Wisconsin). These properties were enrolled in early successional forest management programs administered through the Natural Resources Conservation Service. Bird surveys were paired with landowner responses to a telephone survey conducted from January to May 2017 (n = 102). Most (71.6–81.6%) landowners’ perceptions of avian presence on their properties matched monitoring results. These perceptions were informed by personal observations and by outreach from agency partners and field technicians. Landowners who already completed their conservation program contracts (n = 85) continued managing early successional forests. Continued management for early successional habitat was positively associated with perceived benefits to birds, forest health, and scenery. Our findings give insight into how private landowners respond to environmental effects of forest management. We conclude that positive environmental outcomes of these conservation programs are related to continued early successional forest conservation by private landowners. Full article

(This article belongs to the Section Forest Economics, Policy, and Social Science)

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15 pages, 3392 KiB

Open AccessArticle

Potential Distribution Shifts of Plant Species under Climate Change in Changbai Mountains, China

by Lei Wang, Wen J. Wang, Zhengfang Wu, Haibo Du, Shengwei Zong and Shuang Ma

Forests 2019, 10(6), 498; https://doi.org/10.3390/f10060498 - 11 Jun 2019

Cited by 20 | Viewed by 3369

Abstract

Shifts in alpine tundra plant species have important consequences for biodiversity and ecosystem services. However, recent research on upward species shifts have focused mainly on polar and high-latitude regions and it therefore remains unclear whether such vegetation change trends also are applicable to [...] Read more.

Shifts in alpine tundra plant species have important consequences for biodiversity and ecosystem services. However, recent research on upward species shifts have focused mainly on polar and high-latitude regions and it therefore remains unclear whether such vegetation change trends also are applicable to the alpine tundra at the southern edges of alpine tundra species distribution. This study evaluated an alpine tundra region within the Changbai Mountains, China, that is part of the southernmost alpine tundra in eastern Eurasia. We investigated plant species shifts in alpine tundra within the Changbai Mountains over the last three decades (1984–2015) by comparing contemporary survey results with historical ones and evaluated potential changes in the distribution of dwarf shrub and herbaceous species over the next three decades (2016–2045) using a combination of observations and simulations. The results of this study revealed that the encroachment of herbaceous plants had altered tundra vegetation to a significant extent over the last three decades, especially within low and middle alpine tundra regions in Changbai Mountains, China. The herbaceous species would continue shifting upward and expanding while their dwarf shrub counterparts would continue shifting upward and shrinking over the next three decades under the RCP 4.5 and RCP 8.5 scenarios. The upward shifts of plant species would not keep up with the rate of climate warming under the RCP 8.5 scenarios. The dominant plant tundra species may transform from dwarf shrubs to herbaceous varieties. The results of this study provide a scientific basis for biodiversity protection under climate change and a reference data set for additional research on alpine vegetation dynamics. Full article

(This article belongs to the Special Issue New Technical Advances: Explore Forest Landscape Ecology and Biodiversity Using Geographic Information Science)

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Forests, Volume 10, Issue 6 (June 2019) – 67 articles

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