Forests

496 KiB

Open AccessArticle

Nonlinear Simultaneous Equations for Individual-Tree Diameter Growth and Mortality Model of Natural Mongolian Oak Forests in Northeast China

by Wu Ma and Xiangdong Lei

Forests 2015, 6(6), 2261-2280; https://doi.org/10.3390/f6062261 - 23 Jun 2015

Cited by 17 | Viewed by 5021

Abstract

A nonlinear equation system for individual tree diameter growth and mortality of natural Mongolian oak forests was developed based on 13,360 observations from 195 permanent sample plots in Northeast China. Weighted regression was used in a distance-independent diameter growth equation for dealing with [...] Read more.

A nonlinear equation system for individual tree diameter growth and mortality of natural Mongolian oak forests was developed based on 13,360 observations from 195 permanent sample plots in Northeast China. Weighted regression was used in a distance-independent diameter growth equation for dealing with heterocedasticity. Since diameter growth and mortality models have common predictors including the diameter at breast height (DBH), stand basal area (BA), basal-area-in-larger trees (BAL), and site index (SI), parameters were estimated using nonlinear three-stage least squares (N3SLS) and seemingly unrelated regression (SUR) which accounts for correlations of errors across models. The system equation provided better projection than individual fitting of the equation based on maximum likelihood estimation. Compared with the separate tree growth model, the simultaneous equations using N3SLS and SUR produced more efficient parameter estimation and smaller bias. Furthermore, N3SLS had more accurate projection. Overall, the simultaneous model will facilitate the growth and yield projection for better management of Mongolian oak forests in the region. Full article

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1461 KiB

Open AccessArticle

Regulation of Water Use in the Southernmost European Fir (Abies pinsapo Boiss.): Drought Avoidance Matters

by Raúl Sánchez-Salguero, Cristina Ortíz, Felisa Covelo, Victoria Ochoa, Roberto García-Ruíz, José Ignacio Seco, José Antonio Carreira, José Ángel Merino and Juan Carlos Linares

Forests 2015, 6(6), 2241-2260; https://doi.org/10.3390/f6062241 - 19 Jun 2015

Cited by 19 | Viewed by 6588

Abstract

The current scenario of global warming has resulted in considerable uncertainty regarding the capacity of forest trees to adapt to increasing drought. Detailed ecophysiological knowledge would provide a basis to forecast expected species dynamics in response to climate change. Here, we compare the [...] Read more.

The current scenario of global warming has resulted in considerable uncertainty regarding the capacity of forest trees to adapt to increasing drought. Detailed ecophysiological knowledge would provide a basis to forecast expected species dynamics in response to climate change. Here, we compare the water balance (stomatal conductance, xylem water potential, needle osmotic adjustment) of Abies pinsapo, a relict drought-sensitive Mediterranean fir, along an altitudinal gradient. We related these variables to soil water and nutrient availability, air temperature, atmospheric water potential, and vapour pressure deficit during two consecutive years. Our results indicate that A. pinsapo closed stomata rapidly over a very narrow range of soil water availability and atmospheric dryness. This isohydric response during water stress suggests that this relict conifer relied on the plant hormone abscisic acid to maintain closed stomata during sustained drought, instead of needle desiccation to passively drive stomatal closure, needle osmotic adjustment or a plastic response of the xylem to different levels of water availability. Both the soil and foliar nutrient contents suggest that the studied populations are not limited by nutrient deficiencies, and drought was stronger in the warmer low-elevation areas. Full article

(This article belongs to the Special Issue Responses of Forest Trees to Drought)

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12517 KiB

Open AccessArticle

Effect of Climate Change Projections on Forest Fire Behavior and Values-at-Risk in Southwestern Greece

by Kostas Kalabokidis, Palaiologos Palaiologou, Evangelos Gerasopoulos, Christos Giannakopoulos, Effie Kostopoulou and Christos Zerefos

Forests 2015, 6(6), 2214-2240; https://doi.org/10.3390/f6062214 - 19 Jun 2015

Cited by 49 | Viewed by 9982

Abstract

Climate change has the potential to influence many aspects of wildfire behavior and risk. During the last decade, Greece has experienced large-scale wildfire phenomena with unprecedented fire behavior and impacts. In this study, thousands of wildfire events were simulated with the Minimum Travel [...] Read more.

Climate change has the potential to influence many aspects of wildfire behavior and risk. During the last decade, Greece has experienced large-scale wildfire phenomena with unprecedented fire behavior and impacts. In this study, thousands of wildfire events were simulated with the Minimum Travel Time (MTT) fire growth algorithm (called Randig) and resulted in spatial data that describe conditional burn probabilities, potential fire spread and intensity in Messinia, Greece. Present (1961–1990) and future (2071–2100) climate projections were derived from simulations of the KNMI regional climate model RACMO2, under the SRES A1B emission scenario. Data regarding fuel moisture content, wind speed and direction were modified for the different projection time periods to be used as inputs in Randig. Results were used to assess the vulnerability changes for certain values-at-risk of the natural and human-made environment. Differences in wildfire risk were calculated and results revealed that larger wildfires that resist initial control are to be expected in the future, with higher conditional burn probabilities and intensities for extensive parts of the study area. The degree of change in the modeled Canadian Forest Fire Weather Index for the two time periods also revealed an increasing trend in frequencies of higher values for the future. Full article

(This article belongs to the Special Issue Climate Change and Forest Fire)

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809 KiB

Open AccessArticle

Growth and Nutrient Status of Foliage as Affected by Tree Species and Fertilization in a Fire-Disturbed Urban Forest

by Choonsig Kim, Jaeyeob Jeong, Jae-Hyun Park and Ho-Seop Ma

Forests 2015, 6(6), 2199-2213; https://doi.org/10.3390/f6062199 - 19 Jun 2015

Cited by 11 | Viewed by 4840

Abstract

The aim of the present study was to evaluate the growth and macronutrient (C, N, P, K) status in the foliage of four tree species (LT: Liriodendron tulipifera L.; PY: Prunus yedoensis Matsumura; QA: Quercus acutissima Carruth; PT: Pinus thunbergii Parl.) in response [...] Read more.

The aim of the present study was to evaluate the growth and macronutrient (C, N, P, K) status in the foliage of four tree species (LT: Liriodendron tulipifera L.; PY: Prunus yedoensis Matsumura; QA: Quercus acutissima Carruth; PT: Pinus thunbergii Parl.) in response to fertilization with different nutrient ratios in a fire-disturbed urban forest located in BongDaesan (Mt.), Korea. Two fertilizers (N₃P₈K₁ = 113:300:37 kg·ha⁻¹·year⁻¹; N₆P₄K₁ = 226:150:37 ha⁻¹·year⁻¹) in four planting sites were applied in April 2013 and March 2014. The growth and nutrient responses of the foliage were monitored six times for two years. Foliar growth and nutrient concentrations were not significantly different (p > 0.05) in response to different doses of N or P fertilizer, but the foliage showed increased N and P concentrations and content after fertilization compared with the control (N₀P₀K₀). Foliar C and K concentrations were little affected by fertilization. Foliar nutrient concentrations and contents were significantly higher in PY and LT than in PT. The results suggest that the foliar N and P concentration could be used as a parameter to assess the nutrient environments of tree species restored in a fire-disturbed urban forest. Full article

(This article belongs to the Special Issue Nitrogen and Phosphorus Nutrition of Trees and Forests)

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2130 KiB

Open AccessArticle

Modelling Facilitates Silvicultural Decision-Making for Improving the Mitigating Effect of Beech (Fagus Sylvatica L.) Dominated Alpine Forest against Rockfall

by Petra Kajdiž, Jurij Diaci and Jernej Rebernik

Forests 2015, 6(6), 2178-2198; https://doi.org/10.3390/f6062178 - 19 Jun 2015

Cited by 9 | Viewed by 4980

Abstract

In southeast Europe, silvicultural measures for improving forest protective effects against rockfall are often based on unsystematic observation and experience. We compared formalised expert assessment of forest protective effects and silvicultural decision-making with an approach supported by modelling (Rockyfor3D, Rockfor.NET, shadow angle method). [...] Read more.

In southeast Europe, silvicultural measures for improving forest protective effects against rockfall are often based on unsystematic observation and experience. We compared formalised expert assessment of forest protective effects and silvicultural decision-making with an approach supported by modelling (Rockyfor3D, Rockfor.NET, shadow angle method). The case study was conducted in Fagus sylvatica dominated Alpine forests above the regional road leading to the Ljubelj pass, in Slovenia. We analysed rock sources, silent witnesses, forest structure and regeneration. Expert assessment indicated acceptable protection effects of the forest and their decline in the future. Modelling revealed several road sections endangered by rockfalls. It also indicated subtle differences between silvicultural alternatives: current forest, current forest with cable crane lines, selection forest and non-forested slope. This outcome may be due to short transition zones, small rock sizes, low rock source heights and low resolution of the digital elevation model. Modelling requires more initial input than formalised expert assessment but gives spatially explicit results that enable comparison of silvicultural alternatives, coordination of silviculture and forest operations, and delineation of protection forests. Modelling also supported prioritising of silvicultural measures, where the necessity of silvicultural measures increases with increasing rockfall susceptibility and decreasing long-term stability of stands. Full article

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19504 KiB

Open AccessArticle

Natural Regeneration after Long-Term Bracken Fern Control with Balsa (Ochroma pyramidale) in the Neotropics

by Samuel I. Levy-Tacher, Ivar Vleut, Francisco Román-Dañobeytia and James Aronson

Forests 2015, 6(6), 2163-2177; https://doi.org/10.3390/f6062163 - 16 Jun 2015

Cited by 11 | Viewed by 6387

Abstract

In many parts of the Neotropics, deforested areas are often colonized by the highly competitive invasive bracken fern (Pteridium aquilinum), which inhabits naturally regenerated forests and successional forests on abandoned farmland. Within the tropical forest region of Chiapas in southern Mexico, [...] Read more.

In many parts of the Neotropics, deforested areas are often colonized by the highly competitive invasive bracken fern (Pteridium aquilinum), which inhabits naturally regenerated forests and successional forests on abandoned farmland. Within the tropical forest region of Chiapas in southern Mexico, we implemented an experiment in 2005 to out-compete bracken fern infestation and reduce or eliminate live bracken rhizomes using several treatments: Direct sowing of balsa seeds (Ochroma pyramidale; Malvaceae), a traditional Lacandon treatment of scattering balsa seeds, transplanting balsa seedlings, and a control treatment (without balsa). For each treatment, we applied three different bracken weeding frequencies: No weeding, biweekly weeding, and monthly weeding. In this study, we present data gathered four years after establishing the experiment regarding: Bracken fern rhizome biomass, balsa density, basal area, height, density, species richness of naturally regenerating vegetation for all treatments, and bracken weeding frequencies. We also evaluated the importance of balsa and its regenerative attributes in controlling bracken fern by correlating it with remaining belowground live rhizome biomass. Living rhizome biomass was completely eradicated in all treatments with biweekly and monthly weeding. Density and species richness of a naturally regenerated species were negatively correlated with bracken fern rhizome biomass, and the density of this species was highest in areas with no rhizome biomass. Although balsa tree stands are effective short-term solutions for controlling rhizome biomass, the success of natural regeneration following balsa establishment can be critical to long-term elimination of bracken fern. Full article

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13669 KiB

Open AccessArticle

A Stochastic Programming Model for Fuel Treatment Management

by Mohannad Kabli, Jianbang Gan and Lewis Ntaimo

Forests 2015, 6(6), 2148-2162; https://doi.org/10.3390/f6062148 - 15 Jun 2015

Cited by 11 | Viewed by 4882

Abstract

This work considers a two-stage stochastic integer programming (SIP) approach for optimizing fuel treatment planning under uncertainty in weather and fire occurrence for rural forests. Given a set of areas for potentially performing fuel treatment, the problem is to decide the best treatment [...] Read more.

This work considers a two-stage stochastic integer programming (SIP) approach for optimizing fuel treatment planning under uncertainty in weather and fire occurrence for rural forests. Given a set of areas for potentially performing fuel treatment, the problem is to decide the best treatment option for each area under uncertainty in future weather and fire occurrence. A two-stage SIP model is devised whose objective is to minimize the here-and-now cost of fuel treatment in the first-stage, plus the expected future costs due to uncertain impact from potential fires in the second-stage calculated as ecosystem services losses. The model considers four fuel treatment options: no treatment, mechanical thinning, prescribed fire, and grazing. Several constraints such as budgetary and labor constraints are included in the model and a standard fire behavior model is used to estimate some of the parameters of the model such as fuel levels at the beginning of the fire season. The SIP model was applied to data for a study area in East Texas with 15 treatment areas under different weather scenarios. The results of the study show, for example, that unless the expected ecosystem services values for an area outweigh fuel treatment costs, no treatment is the best choice for the area. Thus the valuation of the area together with the probability of fire occurrence and behavior strongly drive fuel treatment choices. Full article

(This article belongs to the Special Issue Climate Change and Forest Fire)

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Open AccessArticle

Modeling of Two Different Water Uptake Approaches for Mono- and Mixed-Species Forest Stands

by Martin Gutsch, Petra Lasch-Born, Felicitas Suckow and Christopher P.O. Reyer

Forests 2015, 6(6), 2125-2147; https://doi.org/10.3390/f6062125 - 12 Jun 2015

Cited by 7 | Viewed by 5866

Abstract

To assess how the effects of drought could be better captured in process-based models, this study simulated and contrasted two water uptake approaches in Scots pine and Scots pine-Sessile oak stands. The first approach consisted of an empirical function for root water uptake [...] Read more.

To assess how the effects of drought could be better captured in process-based models, this study simulated and contrasted two water uptake approaches in Scots pine and Scots pine-Sessile oak stands. The first approach consisted of an empirical function for root water uptake (WU1). The second approach was based on differences of soil water potential along a soil-plant-atmosphere continuum (WU2) with total root resistance varying at low, medium and high total root resistance levels. Three data sets on different time scales relevant for tree growth were used for model evaluation: Two short-term datasets on daily transpiration and soil water content as well as a long-term dataset on annual tree ring increments. Except WU2 with high total root resistance, all transpiration outputs exceeded observed values. The strongest correlation between simulated and observed annual tree ring width occurred with WU2 and high total root resistance. The findings highlighted the importance of severe drought as a main reason for small diameter increment. However, if all three data sets were taken into account, no approach was superior to the other. We conclude that accurate projections of future forest productivity depend largely on the realistic representation of root water uptake in forest model simulations. Full article

(This article belongs to the Special Issue Responses of Forest Trees to Drought)

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257 KiB

Open AccessArticle

Temporal Trends of Ecosystem Development on Different Site Types in Reclaimed Boreal Forests

by Bradley D. Pinno and Virgil C. Hawkes

Forests 2015, 6(6), 2109-2124; https://doi.org/10.3390/f6062109 - 12 Jun 2015

Cited by 40 | Viewed by 5372

Abstract

Forest development after land reclamation in the oil sands mining region of northern Alberta, Canada was assessed using long-term monitoring plots from both reclaimed and natural forests. The metrics of ecosystem development analyzed included measures of plant community structure and composition and soil [...] Read more.

Forest development after land reclamation in the oil sands mining region of northern Alberta, Canada was assessed using long-term monitoring plots from both reclaimed and natural forests. The metrics of ecosystem development analyzed included measures of plant community structure and composition and soil nutrient availability. Early seral reclamation plots were grouped by site type (dry and moist-rich) and age categories, and these were compared with mature natural forests. There were few significant differences in ecosystem metrics between reclamation site types, but natural stands showed numerous significant differences between site types. Over time, there were significant changes in most plant community metrics such as species richness and cover of plant community groups (e.g., forbs, shrubs, and non-native species), but these were still substantially different from mature forests 20 years after reclamation. Available soil nitrogen did not change over time or by reclamation site type but available soil phosphorus did, suggesting that phosphorus may be a more suitable indicator of ecosystem development. The significant temporal changes in these reclaimed ecosystems indicate that studies of ecosystem establishment and development on reclaimed areas should be conducted over the long-term, emphasizing the utility of monitoring using long-term plot networks. Full article

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Open AccessArticle

Simulating the Effect of Climate Change on Vegetation Zone Distribution on the Loess Plateau, Northwest China

by Guoqing Li, Zhongming Wen, Ke Guo and Sheng Du

Forests 2015, 6(6), 2092-2108; https://doi.org/10.3390/f6062092 - 11 Jun 2015

Cited by 13 | Viewed by 7409

Abstract

A risk assessment of vegetation zone responses to climate change was conducted using the classical Holdridge life zone model on the Loess Plateau of Northwest China. The results show that there are currently ten vegetation zones occurring on the Loess Plateau (1950–2000), including [...] Read more.

A risk assessment of vegetation zone responses to climate change was conducted using the classical Holdridge life zone model on the Loess Plateau of Northwest China. The results show that there are currently ten vegetation zones occurring on the Loess Plateau (1950–2000), including alvar desert, alpine wet tundra, alpine rain tundra, boreal moist forest, boreal wet forest, cool temperate desert, cool temperate desert scrub, cool temperate steppe, cool temperate moist forest, warm temperate desert scrub, warm temperate thorn steppe, and warm temperate dry forest. Seventy years later (2070S), the alvar desert, the alpine wet tundra and the cool temperate desert will disappear, while warm temperate desert scrub and warm temperate thorn steppe will emerge. The area proportion of warm temperate dry forest will expand from 12.2% to 22.8%–37.2%, while that of cool temperate moist forest will decrease from 18.5% to 6.9%–9.5%. The area proportion of cool temperate steppe will decrease from 51.8% to 34.5%–51.6%. Our results suggest that future climate change will be conducive to the growth and expansion of forest zones on the Loess Plateau, which can provide valuable reference information for regional vegetation restoration planning and adaptive strategies in this region. Full article

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Open AccessCommunication

Early Differential Responses of Co-dominant Canopy Species to Sudden and Severe Drought in a Mediterranean-climate Type Forest

by Katinka X. Ruthrof, George Matusick and Giles E. St. J. Hardy

Forests 2015, 6(6), 2082-2091; https://doi.org/10.3390/f6062082 - 09 Jun 2015

Cited by 27 | Viewed by 5987

Abstract

Globally, drought and heat-induced forest disturbance is garnering increasing concern. Species from Mediterranean forests have resistance and resilience mechanisms to cope with drought and differences in these ecological strategies will profoundly influence vegetation composition in response to drought. Our aim was to contrast [...] Read more.

Globally, drought and heat-induced forest disturbance is garnering increasing concern. Species from Mediterranean forests have resistance and resilience mechanisms to cope with drought and differences in these ecological strategies will profoundly influence vegetation composition in response to drought. Our aim was to contrast the early response of two co-occurring forest species, Eucalyptus marginata and Corymbia calophylla, in the Northern Jarrah Forest of southwestern Australia, following a sudden and severe drought event. Forest plots were monitored for health and response, three and 16 months following the drought. Eucalyptus marginata was more susceptible to partial and complete crown dieback compared to C. calophylla, three months after the drought. However, resprouting among trees exhibiting complete crown dieback was similar between species. Overall, E. marginata trees were more likely to die from the impacts of drought, assessed at 16 months. These short-term differential responses to drought may lead to compositional shifts with increases in frequency of drought events in the future. Full article

(This article belongs to the Special Issue Responses of Forest Trees to Drought)

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Open AccessArticle

Comparison of Suspended Branch and Direct Infestation Techniques for Artificially Infesting Hemlock Seedlings with the Hemlock Woolly Adelgid for Resistance Screening

by Zaidee L. Powers, Albert E. Mayfield III, John Frampton and Robert M. Jetton

Forests 2015, 6(6), 2066-2081; https://doi.org/10.3390/f6062066 - 08 Jun 2015

Cited by 2 | Viewed by 3871

Abstract

The hemlock woolly adelgid (Adelges tsugae Annand) is an invasive forest pest in eastern North America that has caused significant decline and mortality in populations of eastern hemlock (Tsuga canadensis (L.) Carr.) and Carolina hemlock (T. caroliniana Engelm.). The breeding [...] Read more.

The hemlock woolly adelgid (Adelges tsugae Annand) is an invasive forest pest in eastern North America that has caused significant decline and mortality in populations of eastern hemlock (Tsuga canadensis (L.) Carr.) and Carolina hemlock (T. caroliniana Engelm.). The breeding of adelgid-resistant genotypes for reforestation activities is still in the early development phases, and most resistance screening programs have depended on labor-intensive direct artificial infestation techniques for introducing adelgids to target seedlings. We investigated the timing and effectiveness of a potentially less labor-intense suspended branch infestation technique compared to two levels of a direct infestation method. Results indicated that peak crawler emergence from adelgid infested hemlock branches occurred within a 10 to 14 day period and that crawler emergence was higher from non-hydrated compared to hydrated branches. Greater infestation pressure was achieved when using progrediens crawlers compared to sistens crawlers. In 2013, when the infestation attempts were most successful, the suspended branch technique induced the same or higher adelgid densities on target seedlings as the direct infestation techniques. Assuming an initial investment in infrastructure, the suspended branch approach could be a more time and cost effective method for inducing adelgid infestations for resistance screening of large numbers of candidate trees. Full article

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Open AccessArticle

How do Light and Water Acquisition Strategies Affect Species Selection during Secondary Succession in Moist Tropical Forests?

by Leonie Schönbeck, Madelon Lohbeck, Frans Bongers, Miguel Martínez Ramos and Frank Sterck

Forests 2015, 6(6), 2047-2065; https://doi.org/10.3390/f6062047 - 08 Jun 2015

Cited by 19 | Viewed by 6363

Abstract

Pioneer tree species have acquisitive leaf characteristics associated with high demand of light and water, and are expected to be shade and drought intolerant. Using leaf functional traits (specific leaf area, photosynthetic rate, relative water content and stomatal conductance) and tree performance (mortality [...] Read more.

Pioneer tree species have acquisitive leaf characteristics associated with high demand of light and water, and are expected to be shade and drought intolerant. Using leaf functional traits (specific leaf area, photosynthetic rate, relative water content and stomatal conductance) and tree performance (mortality rate) in the field, we assessed how shade and drought tolerance of leaves are related to the species’ positions along a successional gradient in moist tropical forest in Chiapas, Mexico. We quantified morphological and physiological leaf shade and drought tolerance indicators for 25 dominant species that characterize different successional stages. We found that light demand decreases with succession, confirming the importance of light availability for species filtering during early stages of succession. In addition, water transport levels in the leaves decreased with succession, but high water transport did not increase the leaf’s vulnerability to drought. In fact, late successional species showed higher mortality in dry years than early successional ones, against suggestions from leaf drought tolerance traits. It is likely that pioneer species have other drought-avoiding strategies, like deep rooting systems and water storage in roots and stems. More research on belowground plant physiology is needed to understand how plants adapt to changing environments, which is crucial to anticipate the effects of climate change on secondary forests. Full article

(This article belongs to the Special Issue Responses of Forest Trees to Drought)

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9258 KiB

Open AccessReview

Are Mixed Tropical Tree Plantations More Resistant to Drought than Monocultures?

by Norbert Kunert and Alida Mercado Cárdenas

Forests 2015, 6(6), 2029-2046; https://doi.org/10.3390/f6062029 - 05 Jun 2015

Cited by 29 | Viewed by 9957

Abstract

Tropical tree plantations usually consist of a single exotic fast growing species, but recent research describes positive effects on ecosystem functions from mixed tropical tree plantations. In this review, we present the current knowledge of drought resistance of tropical mixed species plantations and [...] Read more.

Tropical tree plantations usually consist of a single exotic fast growing species, but recent research describes positive effects on ecosystem functions from mixed tropical tree plantations. In this review, we present the current knowledge of drought resistance of tropical mixed species plantations and summarize preliminary evidence from a tree biodiversity experiment in Panama. Converting mono-specific stands into mixed ones may improve stand stability and might reduce increasing abiotic and biotic disturbances due to climate change. However, little is known about the extent to which tropical tree species or tropical tree communities can resist increasing disturbances in the short term, e.g., water limitations due to increasing dry season intensity or length, or about their resilience after such disturbances and their capacity to adapt to changing conditions in the long term. Studies relating drought resistance and resilience to community diversity are missing. Further, we highlight the urgent need for a multifactorial manipulative throughfall reduction experiment in tropical environments. The outcome of such studies would greatly assist the forestry sector in tropical regions to maintain highly productive and ecologically sound forest plantations in a changing climate. Full article

(This article belongs to the Special Issue Responses of Forest Trees to Drought)

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Open AccessCommunication

A Range-Wide Experiment to Investigate Nutrient and Soil Moisture Interactions in Loblolly Pine Plantations

by Rodney E. Will, Thomas Fox, Madison Akers, Jean-Christophe Domec, Carlos González-Benecke, Eric J. Jokela, Michael Kane, Marshall A. Laviner, Geoffrey Lokuta, Daniel Markewitz, Mary Anne McGuire, Cassandra Meek, Asko Noormets, Lisa Samuelson, John Seiler, Brian Strahm, Robert Teskey, Jason Vogel, Eric Ward, Jason West, Duncan Wilson and Timothy A. Martin Show full author list Hide full author list

Forests 2015, 6(6), 2014-2028; https://doi.org/10.3390/f6062014 - 03 Jun 2015

Cited by 30 | Viewed by 9095

Abstract

The future climate of the southeastern USA is predicted to be warmer, drier and more variable in rainfall, which may increase drought frequency and intensity. Loblolly pine (Pinus taeda) is the most important commercial tree species in the world and is [...] Read more.

The future climate of the southeastern USA is predicted to be warmer, drier and more variable in rainfall, which may increase drought frequency and intensity. Loblolly pine (Pinus taeda) is the most important commercial tree species in the world and is planted on ~11 million ha within its native range in the southeastern USA. A regional study was installed to evaluate effects of decreased rainfall and nutrient additions on loblolly pine plantation productivity and physiology. Four locations were established to capture the range-wide variability of soil and climate. Treatments were initiated in 2012 and consisted of a factorial combination of throughfall reduction (approximate 30% reduction) and fertilization (complete suite of nutrients). Tree and stand growth were measured at each site. Results after two growing seasons indicate a positive but variable response of fertilization on stand volume increment at all four sites and a negative effect of throughfall reduction at two sites. Data will be used to produce robust process model parameterizations useful for simulating loblolly pine growth and function under future, novel climate and management scenarios. The resulting improved models will provide support for developing management strategies to increase pine plantation productivity and carbon sequestration under a changing climate. Full article

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Open AccessArticle

Satellite-Based Derivation of High-Resolution Forest Information Layers for Operational Forest Management

by Johannes Stoffels, Joachim Hill, Thomas Sachtleber, Sebastian Mader, Henning Buddenbaum, Oksana Stern, Joachim Langshausen, Jürgen Dietz and Godehard Ontrup

Forests 2015, 6(6), 1982-2013; https://doi.org/10.3390/f6061982 - 03 Jun 2015

Cited by 31 | Viewed by 10065

Abstract

A key factor for operational forest management and forest monitoring is the availability of up-to-date spatial information on the state of forest resources. Earth observation can provide valuable contributions to these information needs. The German federal state of Rhineland-Palatinate transferred its inherited forest [...] Read more.

A key factor for operational forest management and forest monitoring is the availability of up-to-date spatial information on the state of forest resources. Earth observation can provide valuable contributions to these information needs. The German federal state of Rhineland-Palatinate transferred its inherited forest information system to a new architecture that is better able to serve the needs of centralized inventory and planning services, down to the level of forest districts. During this process, a spatially adaptive classification approach was developed to derive high-resolution forest information layers (e.g., forest type, tree species distribution, development stages) based on multi-temporal satellite data. This study covers the application of the developed approach to a regional scale (federal state level) and the further adaptation of the design to meet the information needs of the state forest service. The results confirm that the operational requirements for mapping accuracy can, in principle, be fulfilled. However, the state-wide mapping experiment also revealed that the ability to meet the required level of accuracy is largely dependent on the availability of satellite observations within the optimum phenological time-windows. Full article

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Open AccessArticle

Spatial Variation of Biomass Carbon Density in a Subtropical Region of Southeastern China

by Weijun Fu, Zhuojing Fu, Hongli Ge, Biyong Ji, Peikun Jiang, Yongfu Li, Jiasen Wu and Keli Zhao

Forests 2015, 6(6), 1966-1981; https://doi.org/10.3390/f6061966 - 03 Jun 2015

Cited by 31 | Viewed by 5715

Abstract

Spatial pattern information of forest biomass carbon (FBC) density in forest ecosystems plays an important role in evaluating carbon sequestration potentials and forest management. The spatial variation of FBC density in a subtropical region of southeastern China was studied using geostatistics combined with [...] Read more.

Spatial pattern information of forest biomass carbon (FBC) density in forest ecosystems plays an important role in evaluating carbon sequestration potentials and forest management. The spatial variation of FBC density in a subtropical region of southeastern China was studied using geostatistics combined with Moran’s I and geographical information systems (GIS). Forest biomass carbon density values were variable, ranging from 0.12 Mg ha⁻¹ to 182.12 Mg ha⁻¹, with an average of 27.33 Mg ha⁻¹. The FBC density had the strongest positive correlation with forest age, followed by forest litter and elevation. The FBC density had significant positive spatial autocorrelation revealed by global Moran’s I. Clear spatial patterns were observed based on local Moran’s I. High FBC density values were mainly distributed in the northwestern and southwestern parts of Zhejiang province, which were related to adopting long-term policy of forest conservation in these areas, while low FBC density values located in the middle part and southeastern coastal area of the study area due to low forest coverage and intensive management of economic forests. The Moran’s I combined with geostatistical interpolation proved to be a useful tool for studying spatial variation of FBC density. Full article

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Open AccessArticle

Soil Chemical and Microbial Properties in a Mixed Stand of Spruce and Birch in the Ore Mountains (Germany)—A Case Study

by Karoline Schua, Stefan Wende, Sven Wagner and Karl-Heinz Feger

Forests 2015, 6(6), 1949-1965; https://doi.org/10.3390/f6061949 - 01 Jun 2015

Cited by 15 | Viewed by 5953

Abstract

A major argument for incorporating deciduous tree species in coniferous forest stands is their role in the amelioration and stabilisation of biogeochemical cycles. Current forest management strategies in central Europe aim to increase the area of mixed stands. In order to formulate statements [...] Read more.

A major argument for incorporating deciduous tree species in coniferous forest stands is their role in the amelioration and stabilisation of biogeochemical cycles. Current forest management strategies in central Europe aim to increase the area of mixed stands. In order to formulate statements about the ecological effects of mixtures, studies at the stand level are necessary. In a mixed stand of Norway spruce (Picea abies (L.) Karst.) and silver birch (Betula pendula Roth) in the Ore Mountains (Saxony, Germany), the effects of these two tree species on chemical and microbial parameters in the topsoil were studied at one site in the form of a case study. Samples were taken from the O layer and A horizon in areas of the stand influenced by either birch, spruce or a mixture of birch and spruce. The microbial biomass, basal respiration, metabolic quotient, pH-value and the C and N contents and stocks were analysed in the horizons Of, Oh and A. Significantly higher contents of microbial N were observed in the Of and Oh horizons in the birch and in the spruce-birch strata than in the stratum containing only spruce. The same was found with respect to pH-values in the Of horizon and basal respiration in the Oh horizon. Compared to the spruce stratum, in the birch and spruce-birch strata, significantly lower values were found for the contents of organic C and total N in the A horizon. The findings of the case study indicated that single birch trees have significant effects on the chemical and microbial topsoil properties in spruce-dominated stands. Therefore, the admixture of birch in spruce stands may distinctly affect nutrient cycling and may also be relevant for soil carbon sequestration. Further studies of these functional aspects are recommended. Full article

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Open AccessArticle

Evaluating the Scenic Beauty of Individual Trees: A Case Study Using a Nonlinear Model for a Pinus Tabulaeformis Scenic Forest in Beijing, China

by Bin Mao, Lan Gong and Chengyang Xu

Forests 2015, 6(6), 1933-1948; https://doi.org/10.3390/f6061933 - 01 Jun 2015

Cited by 14 | Viewed by 4912

Abstract

The relationship between scenic beauty grade and measured tree indicators was studied through evaluation of 427 photos of individual Pinus tabulaeformis trees by using the scenic beauty estimation (SBE) method. Thirteen indices to reflect trunk, crown and stem-to-canopy ratios of individual trees were [...] Read more.

The relationship between scenic beauty grade and measured tree indicators was studied through evaluation of 427 photos of individual Pinus tabulaeformis trees by using the scenic beauty estimation (SBE) method. Thirteen indices to reflect trunk, crown and stem-to-canopy ratios of individual trees were evaluated by invited students. Results showed that students preferred large diameters at breast height, full canopies and straight stems or some trees with minor crook stems. Tree height had a minor contribution to individual tree quality. Correlation analysis and factor analysis were employed to select indices and to integrate them into a comprehensive index. The stepwise method of nonlinear model incorporation of four comprehensive indices—tree crown form, stem-crown coordination, tree growth and stem for—were proven valuable in order to evaluate the scenic beauty of individual trees. Full article

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Open AccessArticle

Nitrogen Transfer to Forage Crops from a Caragana Shelterbelt

by Gazali Issah, Anthony A. Kimaro, John Kort and J. Diane Knight

Forests 2015, 6(6), 1922-1932; https://doi.org/10.3390/f6061922 - 29 May 2015

Cited by 5 | Viewed by 4869

Abstract

Caragana shelterbelts are a common feature of farms in the Northern Great Plains of North America. We investigated if nitrogen (N) from this leguminous shrub contributed to the N nutrition of triticale and oat forage crops growing adjacent to the shelterbelt row. Nitrogen [...] Read more.

Caragana shelterbelts are a common feature of farms in the Northern Great Plains of North America. We investigated if nitrogen (N) from this leguminous shrub contributed to the N nutrition of triticale and oat forage crops growing adjacent to the shelterbelt row. Nitrogen transfer was measured using ¹⁵N isotope dilution at distances of 2 m, 4 m, 6 m, 15 m and 20 m from the shelterbelt. At 2 m caragana negatively impacted the growth of triticale and oat. At 4 m from the shelterbelt productivity was maximum for both forage crops and corresponded to the highest amount of N originating from caragana. The amount of N transferred from caragana decreased linearly with distance away from the shelterbelt, but even at 20 m from the shelterbelt row measureable amounts of N originating from caragana were detectable in the forage biomass. At 4 m from the shelterbelt approximately 40% of the N in both oat and triticale was from caragana, and at 20 m from the shelterbelt approximately 20% of the N in oat and 8% of the N in triticale was from caragana. Full article

(This article belongs to the Special Issue Nitrogen and Phosphorus Nutrition of Trees and Forests)

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19870 KiB

Open AccessArticle

Impact of Nitrogen Fertilization on Forest Carbon Sequestration and Water Loss in a Chronosequence of Three Douglas-Fir Stands in the Pacific Northwest

by Xianming Dou, Baozhang Chen, T. Andrew Black, Rachhpal S. Jassal and Mingliang Che

Forests 2015, 6(6), 1897-1921; https://doi.org/10.3390/f6061897 - 29 May 2015

Cited by 20 | Viewed by 6119

Abstract

To examine the effect of nitrogen (N) fertilization on forest carbon (C) sequestration and water loss, we used an artiﬁcial neural network model to estimate C fluxes and evapotranspiration (ET) in response to N fertilization during four post-fertilization years in a Pacific Northwest [...] Read more.

To examine the effect of nitrogen (N) fertilization on forest carbon (C) sequestration and water loss, we used an artiﬁcial neural network model to estimate C fluxes and evapotranspiration (ET) in response to N fertilization during four post-fertilization years in a Pacific Northwest chronosequence of three Douglas-fir stands aged 61, 22 and 10 years old in 2010 (DF49, HDF88 and HDF00, respectively). Results showed that N fertilization increased gross primary productivity (GPP) for all three sites in all four years with the largest absolute increase at HDF00 followed by HDF88. Ecosystem respiration increased in all four years at HDF00, but decreased over the last three years at HDF88 and over all four years at DF49. As a result, fertilization increased the net ecosystem productivity of all three stands with the largest increase at HDF88, followed by DF49. Fertilization had no discernible effect on ET in any of the stands. Consequently, fertilization increased water use efficiency (WUE) in all four post-fertilization years at all three sites and also increased light use efficiency (LUE) of all the stands, especially HDF00. Our results suggest that the effects of fertilization on forest C sequestration and water loss may be associated with stand age and fertilization; the two younger stands appeared to be more efficient than the older stand with respect to GPP, WUE and LUE. Full article

(This article belongs to the Special Issue Nitrogen and Phosphorus Nutrition of Trees and Forests)

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18937 KiB

Open AccessArticle

Short-Term Response of Native Flora to the Removal of Non-Native Shrubs in Mixed-Hardwood Forests of Indiana, USA

by Joshua M. Shields, Michael R. Saunders, Kevin D. Gibson, Patrick A. Zollner, John B. Dunning, Jr. and Michael A. Jenkins

Forests 2015, 6(6), 1878-1896; https://doi.org/10.3390/f6061878 - 29 May 2015

Cited by 14 | Viewed by 5641

Abstract

While negative impacts of invasive species on native communities are well documented, less is known about how these communities respond to the removal of established populations of invasive species. With regard to invasive shrubs, studies examining native community response to removal at scales [...] Read more.

While negative impacts of invasive species on native communities are well documented, less is known about how these communities respond to the removal of established populations of invasive species. With regard to invasive shrubs, studies examining native community response to removal at scales greater than experimental plots are lacking. We examined short-term effects of removing Lonicera maackii (Amur honeysuckle) and other non-native shrubs on native plant taxa in six mixed-hardwood forests. Each study site contained two 0.64 ha sample areas—an area where all non-native shrubs were removed and a reference area where no treatment was implemented. We sampled vegetation in the spring and summer before and after non-native shrubs were removed. Cover and diversity of native species, and densities of native woody seedlings, increased after shrub removal. However, we also observed significant increases in L. maackii seedling densities and Alliaria petiolata (garlic mustard) cover in removal areas. Changes in reference areas were less pronounced and mostly non-significant. Our results suggest that removing non-native shrubs allows short-term recovery of native communities across a range of invasion intensities. However, successful restoration will likely depend on renewed competition with invasive species that re-colonize treatment areas, the influence of herbivores, and subsequent control efforts. Full article

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Open AccessArticle

Post-Fire Seedling Recruitment and Morpho-Ecophysiological Responses to Induced Drought and Salvage Logging in Pinus halepensis Mill. Stands

by Daniel Moya, Jorge De las Heras, Francisco R. López-Serrano and Pablo Ferrandis

Forests 2015, 6(6), 1858-1877; https://doi.org/10.3390/f6061858 - 29 May 2015

Cited by 22 | Viewed by 5721

Abstract

Salvage logging is the commonest post-fire emergency action, but has unclear ecological effects. In the Mediterranean Basin, drought periods and fire regimes are changing and forest management should be adapted. In summer 2009, a mid-high severity fire burned 968 ha of Aleppo pine [...] Read more.

Salvage logging is the commonest post-fire emergency action, but has unclear ecological effects. In the Mediterranean Basin, drought periods and fire regimes are changing and forest management should be adapted. In summer 2009, a mid-high severity fire burned 968 ha of Aleppo pine (Pinus halepensis Mill.) forest in southeast Spain, which was submitted to salvage logging six months later. In spring 2010, plots were set in untreated and logged areas to monitor the recruitment and survival of the main tree species and three companion species: Stipa tenacissima L. (resprouter), Cistus clusii Dunal and Rosmarinus officinalis L. (obligate seeders). We evaluated responses to different scenarios in relation to intensification of summer droughts and forest management to obtain differences in water stress, growth, and gas exchange to cope with summer drought. Drought was induced by using rain-exclusion shelters and recorded ecophysiological characteristics were obtained with a portable gas exchange system. The main tree species recruitment was poor, but companion species showed a high survival ratio. Lower water stress was found for obligate seeder seedlings, which was higher in logged areas with induced drought. The initial post-fire stage was similar for the studied areas. However, after two drought periods (2010 and 2011), significant differences were found in the morphological and ecophysiological responses. In the unmanaged area, the biggest size of individuals due to the most marked increases in height and coverage were observed mainly in resprouter S. tenacissima. In the area submitted to salvage logging, the growth ratios in plots with induced drought were lower, mainly for seeders. Greater productivity was related to higher transpiration, stomatal conductance, and net photosynthetic ratio, but lower water use efficiency was found in obligate seeders with no drought induction, and S. tenacissima obtained higher values in untreated areas. Our results confirm that both forest management and intensification of summer droughts influenced the resilience and productivity of the ecosystems in the short term. Adaptive forest management after fire can imply successful survival and recovery of plant communities in the mid to long term. This study provide a scientific basis to develop tools for the post-fire restoration of serotinous pine forests occurring in low-altitudinal areas of the Mediterranean Basin, prone to summer droughts and fire events. Full article

(This article belongs to the Special Issue Climate Change and Forest Fire)

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Open AccessArticle

Sparse Density, Leaf-Off Airborne Laser Scanning Data in Aboveground Biomass Component Prediction

by Ville Kankare, Jari Vauhkonen, Markus Holopainen, Mikko Vastaranta, Juha Hyyppä, Hannu Hyyppä and Petteri Alho

Forests 2015, 6(6), 1839-1857; https://doi.org/10.3390/f6061839 - 28 May 2015

Cited by 15 | Viewed by 6214

Abstract

The demand for cost-efficient forest aboveground biomass (AGB) prediction methods is growing worldwide. The National Land Survey of Finland (NLS) began collecting airborne laser scanning (ALS) data throughout Finland in 2008 to provide a new high-detailed terrain elevation model. Similar data sets are [...] Read more.

The demand for cost-efficient forest aboveground biomass (AGB) prediction methods is growing worldwide. The National Land Survey of Finland (NLS) began collecting airborne laser scanning (ALS) data throughout Finland in 2008 to provide a new high-detailed terrain elevation model. Similar data sets are being collected in an increasing number of countries worldwide. These data sets offer great potential in forest mapping related applications. The objectives of our study were (i) to evaluate the AGB component prediction accuracy at a resolution of 300 m² using sparse density, leaf-off ALS data (collected by NLS) derived metrics as predictor variables; (ii) to compare prediction accuracies with existing large-scale forest mapping techniques (Multi-source National Forest Inventory, MS-NFI) based on Landsat TM satellite imagery; and (iii) to evaluate the accuracy and effect of canopy height model (CHM) derived metrics on AGB component prediction when ALS data were acquired with multiple sensors and varying scanning parameters. Results showed that ALS point metrics can be used to predict component AGBs with an accuracy of 29.7%–48.3%. AGB prediction accuracy was slightly improved using CHM-derived metrics but CHM metrics had a more clear effect on the estimated bias. Compared to the MS-NFI, the prediction accuracy was considerably higher, which was caused by differences in the remote sensing data utilized. Full article

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Open AccessArticle

Forest Ecosystem Services: Issues and Challenges for Biodiversity, Conservation, and Management in Italy

by Matteo Vizzarri, Roberto Tognetti and Marco Marchetti

Forests 2015, 6(6), 1810-1838; https://doi.org/10.3390/f6061810 - 28 May 2015

Cited by 23 | Viewed by 9054

Abstract

Although forest ecosystems are fundamental sources of services and global biodiversity, their capacity to maintain these benefits in the future is potentially threatened by anthropogenic impacts such as climate change, land use, and unsustainable management practices. Thus far, studies focusing on forests and [...] Read more.

Although forest ecosystems are fundamental sources of services and global biodiversity, their capacity to maintain these benefits in the future is potentially threatened by anthropogenic impacts such as climate change, land use, and unsustainable management practices. Thus far, studies focusing on forests and their services have gained less attention compared with studies on other biomes. Additionally, management practices may potentially undermine the capacity of forests to sustain biodiversity conservation and services in the future, especially outside protected areas. This study linked the concepts of biodiversity and forest ecosystem services at the national level in Italy. Through a downscaled review, we first analyzed management issues, challenges, and needs within the context of forest ecosystem services. We then carried out a survey on protected areas. The results show that forest biodiversity supports the provision of other services and, hence, needs to be preserved and supported by adaptive management practices. Current research on forest ecosystem services must extend policy trajectories to protected areas (i.e., National Parks) as centers of biodiversity and models of the sustainable use of resources. Full article

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Open AccessArticle

Simulation of CO₂ Fluxes in European Forest Ecosystems with the Coupled Soil-Vegetation Process Model “LandscapeDNDC”

by Saúl Molina-Herrera, Rüdiger Grote, Ignacio Santabárbara-Ruiz, David Kraus, Steffen Klatt, Edwin Haas, Ralf Kiese and Klaus Butterbach-Bahl

Forests 2015, 6(6), 1779-1809; https://doi.org/10.3390/f6061779 - 28 May 2015

Cited by 16 | Viewed by 6706

Abstract

CO₂ exchange processes in forest ecosystems are of profound ecological and economic importance, meaning there is a need for generally applicable simulation tools. However, process-based ecosystem models, which are in principal suitable for the task, are commonly evaluated at only a few [...] Read more.

CO₂ exchange processes in forest ecosystems are of profound ecological and economic importance, meaning there is a need for generally applicable simulation tools. However, process-based ecosystem models, which are in principal suitable for the task, are commonly evaluated at only a few sites and for a limited number of plant species. It is thus often unclear if the processes and parameters involved are suitable for model application at a regional scale. We tested the LandscapeDNDC forest growth module PnET (derived from the Photosynthetic / EvapoTranspiration model) with site-specific as well as multi-site calibrated parameters using independent data sets of eddy covariance measurements across a European transect. Although site-specific parametrization is superior (r² for pooled Gross Primary Production (GPP) during calibration period: site-specific = 0.93, multi-site = 0.88; r² for pooled Net Ecosystem Exchange (NEE) during calibration period: site-specific = 0.81, multi-site = 0.73), we show that general parameters are able to represent carbon uptake over periods of several years. The procedure has been applied for the three most dominant European tree species i.e., Scots pine, Norway spruce and European beech. In addition, we discuss potential model improvements with regard to the sensitivity of parameters to site conditions differentiated into climate, nutrient and drought influences. Full article

(This article belongs to the Special Issue Greenhouse Gas Fluxes from Below and Aboveground Forest Deadwood)

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Open AccessArticle

Carbon Storage in a Eucalyptus Plantation Chronosequence in Southern China

by Hu Du, Fuping Zeng, Wanxia Peng, Kelin Wang, Hao Zhang, Lu Liu and Tongqing Song

Forests 2015, 6(6), 1763-1778; https://doi.org/10.3390/f6061763 - 26 May 2015

Cited by 54 | Viewed by 9654

Abstract

Patterns of carbon (C) allocation across different stages of stand development in Eucalyptus urophylla × E. grandis plantations are not well understood. In this study, we examined biomass and mineral soil C content in five development stages (1, 2, 3, 4–5, and 6–8 [...] Read more.

Patterns of carbon (C) allocation across different stages of stand development in Eucalyptus urophylla × E. grandis plantations are not well understood. In this study, we examined biomass and mineral soil C content in five development stages (1, 2, 3, 4–5, and 6–8 years old) of a Eucalyptus stand in southern China. The tree biomass C pool increased with stand age and showed a high annual rate of accumulation. Stems accounted for the highest proportion of biomass C sequestered. The C pool in mineral soil increased initially after afforestation and then declined gradually, with C density decreasing with soil depth. The upper 50 cm of soil contained the majority (57%–68%) of sequestered C. The other biomass components (shrubs, herbaceous plants, litter, and fine roots) accounted for <5% of the total ecosystem C pool. Total C pools in the Eucalyptus plantation ecosystem were 112.9, 172.5, 203.8, 161.1, and 162.7 Mg ha⁻¹ in the five developmental stages, respectively, with most of the C sequestered below ground. We conclude that Eucalyptus plantations have considerable biomass C sequestration potential during stand development. Full article

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Open AccessArticle

Aerial Seeding: An Effective Forest Restoration Method in Highly Degraded Forest Landscapes of Sub-Tropic Regions

by Xin Xiao, Xiaohua Wei, Yuanqiu Liu, Xunzhi Ouyang, Qinglin Li and Jinkui Ning

Forests 2015, 6(6), 1748-1762; https://doi.org/10.3390/f6061748 - 25 May 2015

Cited by 21 | Viewed by 7152

Abstract

Carbon stock is an important indicator of cumulative ecosystem productivity. Using this indicator, and based on field sampling data, this paper compared the long-term difference in carbon stocks between aerial seeding (AS) and natural regeneration (NR) forests of Pinus massoniana in sub-tropic forests, [...] Read more.

Carbon stock is an important indicator of cumulative ecosystem productivity. Using this indicator, and based on field sampling data, this paper compared the long-term difference in carbon stocks between aerial seeding (AS) and natural regeneration (NR) forests of Pinus massoniana in sub-tropic forests, China, in order to assess the effectiveness of AS in a highly degraded forest landscape. The results showed that the carbon stocks of stems, branches, roots, and trees (including stems, branches, leaves, and roots) were 140%, 85%, 110%, and 110%, significantly higher (p < 0.05) in the NR forests than those in the AS forests at the ages of 11–20 years, respectively. In addition, the carbon stocks of understory, litter and soil were also 176%, 151%, and 77%, significantly higher (p < 0.05) in the NR forests than those in the AS forests at the same age range, respectively. However, with increasing age (i.e., >21 years), those differences became statistically insignificant (p > 0.05). The total carbon stocks of the two forest types also showed a similar pattern. Those results clearly demonstrate that AS was an effective mean for restoring carbon stocks in highly degraded areas, even though their early growth was lower than the NR forests, and thus can be applied in the regions where the areas with limited seed sources and road accessibility. Full article

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Forests, Volume 6, Issue 6 (June 2015) – 28 articles , Pages 1748-2280

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