Effects of Disturbances on Forest Soil Biochemistry

A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Forest Soil".

Deadline for manuscript submissions: closed (25 October 2023) | Viewed by 16866

Special Issue Editors

State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
Interests: global change; carbon cycle; microbial ecology; loess plateau; pedology
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Research Institute of Ecology and Natural Resource Management, Tyumen State University, 625003 Tyumen, Russia
Interests: soil function and nutrient cycling

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Guest Editor
State Key Laboratory of Soil Erosion and Dryland Agriculture on the Loess Plateau, Northwest A&F University, Yangling 712100, China
Interests: soil animals; forest carbon cycle; climate change; loess plateau; soil ecology
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
State Key Laboratory of Soil Erosion and Dryland Agriculture on the Loess Plateau, Northwest A&F University, Yangling, Xiangyang 712100, China
Interests: forests carbon cycle; soil water cycle; arid area; loess plateau; soil hydrology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Forest soil is a habitat of numerous organisms, including viruses, bacteria, archaea, fungi, and protozoa, which fulfill key processes in the soil, such as decomposition and nutrient mineralization, and play crucial roles in soil biochemistry processes (such as soil health, water and air flows, and energy fluxes). However, forest ecosystems around the world face tremendous challenges from human disturbances and climate changes, especially in dry forest ecosystems.

Today, characterizations of soil organisms have been largely accessed using sequencing approaches. Despite the recent progress in soil biology and biochemistry over the last few decades, various important questions remain unanswered—for instance, what the environment-controlling factors of the spatial distribution of the soil organisms in forest soil in the dry forest ecosystems are, how human disturbances control the soil organism community and biochemical processes in various climate conditions, how to distinguish the contribution of human disturbances and climate changes to soil functions (such as carbon sequestration function, hydrologic conservation function, water and soil conservation function) in forest ecosystems, and how biotic and abiotic drivers control these biochemical processes in forest ecosystems.

Thus, this Special Issue will include different types of contributions: perspectives, reviews, methodology, meta-analyses, and original research articles that focus on the soil biochemical processes under human disturbances and climate changes in forest ecosystems. Moreover, we welcome papers dealing with the importance of soil biodiversity, machine learning in soil biochemistry, spatial modeling of soil fauna, soil and soil food web, soil hydrological function, and the interaction between soil biology with soil physicochemical properties and processes to regulate belowground functions.

Dr. Yang Yang
Dr. Andrey Soromotin
Dr. Tongchuan Li
Dr. Jiangbo Qiao
Guest Editors

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Keywords

  • soil microbe
  • soil fauna
  • soil biological network
  • human disturbances
  • climate changes
  • soil function
  • soil biochemistry
  • soil hydrologic function

Published Papers (11 papers)

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Research

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12 pages, 1279 KiB  
Article
Impacts of Different Types of Vegetation Restoration on the Physicochemical Properties of Sandy Soil
by Du Lyu, Qiuman Liu, Tao Xie and Yahui Yang
Forests 2023, 14(9), 1740; https://doi.org/10.3390/f14091740 - 28 Aug 2023
Cited by 1 | Viewed by 801
Abstract
Understanding the integrated effects of vegetation types on the physicochemical properties and quality of sandy soils is crucial for guiding vegetation reconstruction and ecological restoration in desertified areas. This study selected three vegetation types at the southern edge of the Mu Us sandy [...] Read more.
Understanding the integrated effects of vegetation types on the physicochemical properties and quality of sandy soils is crucial for guiding vegetation reconstruction and ecological restoration in desertified areas. This study selected three vegetation types at the southern edge of the Mu Us sandy land, including fenced Leymus secalinus Tzvel. grassland (LS), natural Hedysarum mongolicum Turcz (HM) forest land, and Salix cheilophila Schneid. (SC) forest land, as well as sandy land as a control (SD). The differences in the soil physicochemical properties were investigated by collecting soils from three layers within 0–60 cm. The soil quality index (SQI) was calculated using principal component analysis to comprehensively evaluate the soil quality. This study found that the soil physicochemical properties differed significantly among the plots and layers, and the soil properties exhibited a vertical distribution, with chemical indicators concentrated in the surface layer. As depth increased, differences in soil properties between the vegetation and control plots diminished, with vegetation influence mainly in the 0–20 cm layer. Among all the sample sites, the 0–20 cm layer of LS had the highest organic matter content (5.98 g/kg), which was 2.25, 2.28, and 4.71 times that of HM, SC, and SD, respectively. Moreover, LS had the lowest bulk density (1.35 g/cm3), which was 0.89, 0.91, and 0.86 times lower than that of HM, SC, and SD, respectively. The effects of different vegetation restoration types on the comprehensive quality of soil were different, as shown in LS (0.15) > HM (0.11) > SC (0.10) > SD (0.08). In conclusion, all three vegetation restoration types significantly affected the soil physicochemical properties and led to different degrees of variability of soil indexes in the vertical profile, and the fenced grassland restoration type may be preferable for ecological restoration and reconstruction in this region. Full article
(This article belongs to the Special Issue Effects of Disturbances on Forest Soil Biochemistry)
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16 pages, 5200 KiB  
Article
Mycorrhizal Fungi Reclamation Promotes Stoichiometric Homeostasis of Re-Vegetation Types and Affects Soil Bacterial Function in Mining Subsidence of Northern Loess Plateau
by Li Xiao, Yinli Bi and Dongdong Wang
Forests 2023, 14(9), 1720; https://doi.org/10.3390/f14091720 - 26 Aug 2023
Viewed by 771
Abstract
Re-vegetation types and mycorrhizal fungi reclamation play a vital role in the improvement of soil quality in the mining subsidence of the northern Loess Plateau. However, the effects of re-vegetation types and mycorrhizal fungi reclamation on plant stoichiometric homeostasis, soil bacterial communities and [...] Read more.
Re-vegetation types and mycorrhizal fungi reclamation play a vital role in the improvement of soil quality in the mining subsidence of the northern Loess Plateau. However, the effects of re-vegetation types and mycorrhizal fungi reclamation on plant stoichiometric homeostasis, soil bacterial communities and functional characteristics are still not understood well but are vital for mining green construction. Based on the fact that mycorrhizal fungi reclamation has been implemented for more than 10 years (inoculation with arbuscular mycorrhizal fungi (AMF) and control), we examined five re-vegetation types with different C:N:P stoichiometry in the roots, leaves and calculated homeostasis. Meanwhile, second-generation sequencing technology was used to measure soil bacterial communities and functional characteristics to further reveal the relationships between soil factors and bacteria that drive plant stoichiometry and homeostasis in the biological reclamation area of coal mining subsidence. Our results indicated that plant N:P ratio in the leaves of all re-vegetation types was less than 14, with the highest ratio observed in A. fruticosa (nitrogen-fixing plants), showing that re-vegetation growth was limited by the availability of nitrogen. Only leaves in AMF-inoculated plants were categorized as ‘homeostatic’, while inoculation with AMF in both leaves and roots could alleviate nitrogen restriction and improve ecological stoichiometric homeostasis. The dominant phylum was Proteobacteria, followed by Actinobacteria, Acidobacteria, accounting for 69.92%–73.22% of all bacterial species and 82% with Chloroflexi. Soil copiotrophic community (Proteobacteria) in the AMF inoculation area was higher than those in the control area under all re-vegetation types, while the oligotrophic community (Acidobacteria) was lower than the control. Further analysis showed that soil TP, SOC, C:N and HD played vital roles in shifting the soil bacteria community. Soil stoichiometry and AMF affect microbial composition. These results indicated that the re-vegetation types and mycorrhizal fungi reclamation could shift bacterial homogeneity. Hence, our results expound that mycorrhizal fungi reclamation could optimize the ecological strategies of reclaimed vegetation, alleviate N-limitations in plants, improve endogenous stability and promote the ecological function of soil bacteria, which provided theoretical bases for further understanding and application of green restoration and sustainable development in the mining subsidence of the northern Loess Plateau. Full article
(This article belongs to the Special Issue Effects of Disturbances on Forest Soil Biochemistry)
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15 pages, 2177 KiB  
Article
Post-Fire Evolution of Soil Nitrogen in a Dahurian Larch (Larix gmelinii) Forest, Northeast China
by Jiaqi Wang, Yun Zhang, Jia Kang and Xiaoyang Cui
Forests 2023, 14(6), 1178; https://doi.org/10.3390/f14061178 - 07 Jun 2023
Cited by 1 | Viewed by 805
Abstract
This study investigates the evolution of soil nitrogen (N) contents and forms along a 17-year wildfire chronosequence in the Daxing’an Mountains. Surface soil and subsoil samples were collected during different recovery periods after wildfires. Then, the mineral N (i.e., NH4+-N [...] Read more.
This study investigates the evolution of soil nitrogen (N) contents and forms along a 17-year wildfire chronosequence in the Daxing’an Mountains. Surface soil and subsoil samples were collected during different recovery periods after wildfires. Then, the mineral N (i.e., NH4+-N and NO3-N) and amino acid-N (AAN) contents in the soil extracts were measured and used to calculate the different ratios as indicators of the N forms. The results showed that the NH4+-N, NO3-N, and AAN contents increased immediately after the wildfire. With vegetation restoration, the NH4+-N and NO3-N contents became similar to those of unburned forests nine years and two months after the wildfire, respectively. The AAN content was mostly recovered one year post-fire. The wildfire did not lead to substantial changes in the mineral N form, but the ratio significantly increased and recovered after nine years. The soil available N form was altered by wildfires. After the wildfire, the dominant available N form changed from equivalent AAN and mineral N to a predominance of AAN in the growing season, and the predominance of AAN decreased to varying degrees in the non-growing season. With the recovery of the white birch and Dahurian larch, AAN again became the dominant N form, but the predominance of AAN was low before the freeze-up. Our study demonstrates that wildfires directly affect the soil N contents and forms, and such effects could be diminished by the restoration of the soil environment and vegetation over time. Full article
(This article belongs to the Special Issue Effects of Disturbances on Forest Soil Biochemistry)
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15 pages, 4708 KiB  
Article
Dissolved Organic Matter as Affected by Forms and Doses of Nitrogen Applied to Soils of Temperate Deciduous Forests in China
by Peng Wang, Minghua Song and Chunmei Wang
Forests 2023, 14(4), 775; https://doi.org/10.3390/f14040775 - 09 Apr 2023
Cited by 3 | Viewed by 1155
Abstract
Dissolved organic matter (DOM) is an important component in the biogeochemical cycles of elements like nitrogen (N) and carbon. The aim of this study was to elucidate the effect of long-term inorganic N addition on the quantity and quality of DOM in forest [...] Read more.
Dissolved organic matter (DOM) is an important component in the biogeochemical cycles of elements like nitrogen (N) and carbon. The aim of this study was to elucidate the effect of long-term inorganic N addition on the quantity and quality of DOM in forest soils. A field study was conducted on three forms of inorganic N, namely (NH4)2SO4, NH4NO3, and NaNO3, applied at low (50 kg N ha−1) or high (150 kg N ha−1) annual doses from 2011 to 2019. The total dose was split into eight equal monthly doses applied during the growing season (from March to October). Both the form and the dose increased the content of dissolved organic carbon (DOC) in soil, the strongest effect being that of NaNO3. However, the higher dose had a weaker effect because of N enrichment. UV-visible (UV-vis) and excitation-emission matrix (EEM) spectroscopy showed that the addition of N made DOM more aromatic and increased the degree of humification. EEM-parallel factor analysis (PARAFAC) modelling suggested that DOM in the forest soils mainly contained a fulvic-like constituent (C1), humic-like substances (C2), and aromatic protein-like components (C3). The addition did not change the position of the DOM fluorophore in the soil but affected the proportions of the three PARAFAC-derived components (increasing those of C1 and C2 but decreasing that of C3), indicating that long-term addition of N may amplify the decrease in protein-like constituents of surface soil. Hence, N addition increased the complexity of the DOM structure. Full article
(This article belongs to the Special Issue Effects of Disturbances on Forest Soil Biochemistry)
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17 pages, 6314 KiB  
Article
The Effect of Human Trampling Activity on a Soil Microbial Community at the Urban Forest Park
by Qianqian Liu, Wensui Li, Hui Nie, Xiaorui Sun, Lina Dong, Liu Xiang, Jinchi Zhang and Xin Liu
Forests 2023, 14(4), 692; https://doi.org/10.3390/f14040692 - 28 Mar 2023
Cited by 2 | Viewed by 3209
Abstract
Soil degradation resulting from human trampling in urban forest parks can negatively impact the taxonomic diversity and function of soil microbial communities. In this study, we established long-term, fixed large plots in Zijin Mountain Urban Forest Park in Nanjing, China, to assess the [...] Read more.
Soil degradation resulting from human trampling in urban forest parks can negatively impact the taxonomic diversity and function of soil microbial communities. In this study, we established long-term, fixed large plots in Zijin Mountain Urban Forest Park in Nanjing, China, to assess the level of trampling pressure. Soil samples were collected from depths of 0–10 cm, 10–20 cm, and 20–30 cm for light trampling (LD), moderate trampling (MD), severe trampling (SD), extreme trampling (ED), and a no-trampling control (CK). The effects of different trampling pressures on soil were studied, including soil nutrient indices, microbial biomass, and the taxonomic diversity of fungi and bacteria. ANOVA and structural equation modeling (SEM) were employed to investigate the impacts of human trampling on the microbial community structure and function. The results indicated that soil organic carbon, ammonium, and acid phosphatase activity were the primary driving factors of microbial community change. Soil microbial diversity initially increased and then decreased with increasing trampling intensity. The changes in soil microbial function and classification were found to be associated with the intensity of trampling. Moderate trampling could enhance the diversity of the soil microbial community. The succession pattern of the fungi and bacteria communities was distinct, and the composition of the bacteria community remained relatively stable. Trampling impacts vegetation and soil structure, which then affects the structure and function of the microbial community. This study provides an essential foundation for the restoration of compacted soil in urban forest parks through targeted monitoring and management efforts. Full article
(This article belongs to the Special Issue Effects of Disturbances on Forest Soil Biochemistry)
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19 pages, 4134 KiB  
Article
Soil C, N, P, K and Enzymes Stoichiometry of an Endangered Tree Species, Parashorea chinensis of Different Stand Ages Unveiled Soil Nutrient Limitation Factors
by Wannian Li, Izhar Ali, Xiaomei Han, Saif Ullah and Mei Yang
Forests 2023, 14(3), 624; https://doi.org/10.3390/f14030624 - 20 Mar 2023
Cited by 3 | Viewed by 1447
Abstract
Parashorea chinensis is an endemic tree species in China and an endangered species of the Dipterocarpaceae family. This study contributes to the understanding of soil fertility management during the relocation and conservation of P. chinensis and the restoration of its natural communities by [...] Read more.
Parashorea chinensis is an endemic tree species in China and an endangered species of the Dipterocarpaceae family. This study contributes to the understanding of soil fertility management during the relocation and conservation of P. chinensis and the restoration of its natural communities by doing an ecological chemometric investigation of the factors limiting soil nutrients in P. chinensis plantations. To investigate the variation in rhizosphere and non-rhizosphere soil nutrients, microbial biomass, and extracellular enzyme activities, we chose pure plantation stands of 6 ages in the subtropics and calculated stoichiometric ratios. The results show that (1) soil pH is strongly acidic (pH < 4.6) and is less influenced by the stand age, and the soil carbon (C), nitrogen (N), and phosphorus (P) content limit soil microorganisms at all stand ages; (2) the availability of soil N, P, and K elements is an essential factor driving P limitation in the growth of P. chinensis and its soil microbes; (3) stand age has a significant effect on the soil C/N, C/P, N/P, C/K, N/K, and P/K, the stoichiometry of microbial biomass C, N, and P, and the stoichiometry of C, N, and P acquisition enzyme activity. Soil microbial biomass C, N, and P stoichiometry are more sensitive indicators of nutrient limitations than the stoichiometry of enzyme activity and nutrient content; and (4) there was a significant correlation between microbial biomass C, N, and P stoichiometry and soil C/P and N/P, as well as a highly significant (p < 0.01) correlation between the stoichiometry of the enzyme activity and Vector L and Vector A. In conclusion, the plantations of P. chinensis in this study area were established on acidic phosphorus-poor soil, and the ecological stoichiometry of the soil reveals nutrient limitations and its variation with the stand age. P availability plays a key role in the growth of P. chinensis and in improving the rhizosphere microbial community. Therefore, soil effectiveness should be dynamically assessed during the cultivation and relocation conservation of P. chinensis, and a soluble P fertilizer should be supplemental over time in the trees’ root distribution area. Full article
(This article belongs to the Special Issue Effects of Disturbances on Forest Soil Biochemistry)
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15 pages, 2332 KiB  
Article
Soil-Available Nutrients Associated with Soil Chemical and Aggregate Properties following Vegetation Restoration in Western Sichuan, China
by Huan Cheng, Mingxuan Che, Wangyang Hu, Qiang Wu, Yilun Cheng, Xu Hu, Shichen Xiong, Jiangkun Zheng and Yuanbo Gong
Forests 2023, 14(2), 259; https://doi.org/10.3390/f14020259 - 30 Jan 2023
Cited by 3 | Viewed by 1627
Abstract
The status and drivers of soil-available nutrients in plant-recovered soils are not fully understood, limiting our ability to explore the role of soil-available nutrients in soil geochemical cycling and ecosystem sustainability. Here, we combined the spatial distribution of soil-available nutrients and chemical and [...] Read more.
The status and drivers of soil-available nutrients in plant-recovered soils are not fully understood, limiting our ability to explore the role of soil-available nutrients in soil geochemical cycling and ecosystem sustainability. Here, we combined the spatial distribution of soil-available nutrients and chemical and aggregate properties from six soil types (subalpine meadow soil, meadow soil, dark brown soil, brown soil, yellow-brown soil, and cinnamon soil) and three horizons (a leaching horizon, sediment horizon, and parent material horizon) to study the status and drivers of soil-available nutrients. Our findings reveal that the soil-available nitrogen (AN) ranged from 72.33 to 169.67 mg/kg, the soil-available phosphorus (AP) ranged from 1.77 to 75.90 mg/kg, and the soil-available potassium (AK) ranged from 46.43 to 88.55 mg/kg in the six soil types. The subalpine meadow soil and the dark brown soil had the highest soil AN, with means of 169.67 and 139.35 mg/kg, respectively. The brown soil had the highest soil AP, with a mean of 75.9 mg/kg, and the dark brown soil and the brown soil had the highest soil AK, with means of 83.49 and 88.55 mg/kg, respectively. The results show that the soil types and soil depths had a significant impact on the status of AN, AP, and AK (p < 0.05). Moreover, a higher cation exchange capacity (CEC), the macro-aggregate contents (with 2–1 mm and 1–0.5 mm particle sizes) of the non-water-stable aggregates, and the macro-aggregate content and stability (2–1 mm particle size and geometric mean diameter (GMD) of the water-stable aggregates were deemed to facilitate soil-available nitrogen because of the positive correlations (p < 0.05). Lower exchangeable cations (ECs) and the micro-aggregate content (≤0.1 mm particle size) of the water-stable aggregates and higher soil cations helped in the accumulation of soil-available phosphorus and soil-available potassium, respectively. Moreover, the regulation of the soil chemical and aggregate properties was found to vary with soil type and horizon in a correlation analysis. Together, our results provide insights into the importance of chemical and aggregate properties in regulating soil nutrient availability across soil types, as well as providing strong support for the inclusion of soil resource utilization in regional forest restoration and management. Full article
(This article belongs to the Special Issue Effects of Disturbances on Forest Soil Biochemistry)
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15 pages, 2741 KiB  
Article
Stability of C:N:P Stoichiometry in the Plant–Soil Continuum along Age Classes in Natural Pinus tabuliformis Carr. Forests of the Eastern Loess Plateau, China
by Haoning Chen, Yun Xiang, Zhixia Yao, Qiang Zhang, Hua Li and Man Cheng
Forests 2023, 14(1), 44; https://doi.org/10.3390/f14010044 - 26 Dec 2022
Cited by 4 | Viewed by 1419
Abstract
Ecological stoichiometry is useful for revealing the biogeochemical characteristics of flows of nutrients and energy between plant and soil, as well as the important implications behind these ecological phenomena. However, the ecological stoichiometric linkages among leaf, litter, soil, and enzymes in the natural [...] Read more.
Ecological stoichiometry is useful for revealing the biogeochemical characteristics of flows of nutrients and energy between plant and soil, as well as the important implications behind these ecological phenomena. However, the ecological stoichiometric linkages among leaf, litter, soil, and enzymes in the natural forests of the Loess Plateau remain largely unknown. Here, leaf, litter, and soil samples were collected from four age classes of natural Pinus tabuliformis Carr. (P. tabuliformis) to explore the deep linkages among these components. We measured the total carbon (C), total nitrogen (N), and total phosphorus (P) concentrations of leaf and litter, as well as the concentrations of soil organic C, total N, total P, nitrate N, ammonium N, available P, and the activities of β-1,4-glucosidase (a C-acquiring enzyme), β-1,4-N-acetylglucosidase (an N-acquiring enzyme), and alkaline phosphatase (a P-acquiring enzyme) in the topsoil (0–20 cm). The average leaf N:P was 6.9 indicated the growth of P. tabuliformis was constrained by N according to the relative resorption theory of nutrient limitation. The C:N, C:P, and N:P ratios in leaf, litter, and soil and the enzyme activity were not significantly different among age classes (p > 0.05). Litter C:N (43.3) was closer to the ratio of leaf C:N (48.8), whereas the litter C:P (257.7) was obviously lower than the ratio of leaf C:P (338.15). We calculated the stoichiometric homeostasis index (1/H) of leaf responses to soil elements and enzyme activities and found that the relationship between leaf C:P and soil C:P was homeostatic (p < 0.05), whereas the remaining indices showed the leaf stoichiometries were strictly homeostatic (p > 0.05). Correlation analysis showed both litter C:P and N:P were positively correlated with leaf and soil C:P, while the stoichiometric ratios of soil elements and enzymes were obviously irrelevant with leaf stoichiometries (p > 0.05). Partial least squares path modeling indicated that litter significantly changed soil element and enzyme characteristics through direct and indirect effects, respectively. However, soil elements and enzymes impacted leaf stoichiometries barely, which was further confirmed by an overall redundancy analysis. In summary, C:N:P stoichiometry within the plant–soil continuum revealed that natural P. tabuliformis is a relatively stable ecosystem in the Loess Plateau, where the element exchanges between plant and soil maintain dynamic balance with forest development. Further studies are needed to capture the critical factors that regulate leaf stoichiometry in the soil system. Full article
(This article belongs to the Special Issue Effects of Disturbances on Forest Soil Biochemistry)
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17 pages, 6234 KiB  
Article
Extracellular Enzyme Activity and Stoichiometry Reveal Nutrient Dynamics during Microbially-Mediated Plant Residue Transformation
by Chunhui Liu, Jingyi Ma, Tingting Qu, Zhijing Xue, Xiaoyun Li, Qin Chen, Ning Wang, Zhengchao Zhou and Shaoshan An
Forests 2023, 14(1), 34; https://doi.org/10.3390/f14010034 - 24 Dec 2022
Cited by 4 | Viewed by 2033
Abstract
Extracellular enzymes are the major mediators of plant residue and organic matter decomposition in soil, frequently associated with microbial metabolic processes and the biochemical cycling of nutrients in soil ecosystems. However, the dynamic trends and driving factors of extracellular enzymes and their stoichiometry [...] Read more.
Extracellular enzymes are the major mediators of plant residue and organic matter decomposition in soil, frequently associated with microbial metabolic processes and the biochemical cycling of nutrients in soil ecosystems. However, the dynamic trends and driving factors of extracellular enzymes and their stoichiometry during plant residue transformation remain to be further studied. Here, we investigated the dynamics of extracellular enzymes and enzymatic stoichiometry in the “litter-soil” transformation interface soil (TIS) layer, an essential occurrence layer for microbially-mediated C transformation. The results indicated an unbalanced relationship between substrate resource supply and microbial metabolic demand. Microbial metabolism was limited by C (C/N-acquiring enzymes > 1) and P (N/P-acquiring enzymes < 1) throughout the observed stages of plant residue transformation. The initially higher extracellular enzyme activity reflected the availability of the active components (dissolved carbon (DC), nitrogen (DN), microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP)) in the substrate and the higher intensity of microbial metabolism. With the transformation of plant residues, the active fraction ceased to be the predominant microbial C source, forcing the secretion of C-acquiring enzymes and N-acquiring enzymes to obtain C sources and N nutrients from refractory substrates. Moreover, C/N-acquiring enzymes decreased, while C/P-acquiring enzymes and N/P-acquiring enzymes subsequently increased, which suggested that the microbial demand for N gradually increased and for P relatively decreased. Soil microorganisms can be forced into dormancy or intracellular mineralization due to the lack of substrate resources, so microbial biomass and extracellular enzyme activities decreased significantly compared to initial values. In summary, the results indicated that soil nutrients indirectly contribute to extracellular enzymes and their stoichiometry by affecting microbial activities. Furthermore, extracellular enzymes and their stoichiometry were more sensitive to the response of soil microbial biomass carbon. Full article
(This article belongs to the Special Issue Effects of Disturbances on Forest Soil Biochemistry)
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25 pages, 5682 KiB  
Article
Effects of Herbaceous Plant Roots on the Soil Shear Strength of the Collapsing Walls of Benggang in Southeast China
by Fang Shuai, Mengyuan Huang, Yuanyuan Zhan, Qin Zhu, Xiaolin Li, Yue Zhang, Jinshi Lin, Yanhe Huang and Fangshi Jiang
Forests 2022, 13(11), 1843; https://doi.org/10.3390/f13111843 - 04 Nov 2022
Cited by 3 | Viewed by 1594
Abstract
Failure of collapsing walls is an important process affecting the development of Benggang and is closely related to the soil shear strength. Plant roots can increase the soil shear strength. However, the effects and mechanisms of root reinforcement on the soil shear strength [...] Read more.
Failure of collapsing walls is an important process affecting the development of Benggang and is closely related to the soil shear strength. Plant roots can increase the soil shear strength. However, the effects and mechanisms of root reinforcement on the soil shear strength of collapsing walls remain unclear. To explore the shear strength characteristics of collapsing walls and their influencing factors under different vegetation conditions, Pennisetum sinese, Dicranopteris dichotoma, Odontosoria chinensis, and Neyraudia reynaudiana were adopted as experimental objects in the Benggang district of Anxi County, Southeast China. We measured the root characteristics and in situ shear strength of root–soil complexes by dividing soil with the four vegetation conditions into five soil layers: 0–5 cm, 5–10 cm, 10–15 cm, 15–20 cm, and 20–25 cm. The average shear strength of the root–soil complexes of the various plants ranked as follows: Pennisetum sinese (30.95 kPa) > Odontosoria chinensis (28.08 kPa) > Dicranopteris dichotoma (21.24 kPa) > Neyraudia reynaudiana (14.99 kPa) > bare soil (11.93 kPa). The enhancement effect of the root system on the soil shear strength was mainly manifested in the 0–5 cm soil surface layer. The soil shear strength attained an extremely significant positive correlation with the root length density, root surface area density, root volume density, root biomass density, for root diameters (L) less than or equal to 0.5 mm and between 0.5 and 1 mm, the soil shear strength could be simulated by using root volume density. The shear strength of undisturbed root–soil complexes measured with a 14.10 pocket vane tester was higher than the value obtained with the Wu–Waldron model (WWM). The correction coefficient k′ varied between 0.20 and 20.25, mostly exceeding 1, and the average correction coefficient k′ value was 4.94. The average correction coefficient determined in this test can be considered to modify the WWM model when conducting experiments under similar conditions. Full article
(This article belongs to the Special Issue Effects of Disturbances on Forest Soil Biochemistry)
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Review

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16 pages, 3299 KiB  
Review
Review of Managing Soil Organic C Sequestration from Vegetation Restoration on the Loess Plateau
by Yang Yang, Hui Sun, Pingping Zhang, Fan Wu, Jiangbo Qiao, Tongchuan Li, Yunqiang Wang and Shaoshan An
Forests 2023, 14(10), 1964; https://doi.org/10.3390/f14101964 - 28 Sep 2023
Cited by 1 | Viewed by 1080
Abstract
China’s Loess Plateau is both the largest and deepest loess deposit in the world, and it has long been one of the most severely eroded areas on Earth. With the implementation of the Grain-for-Green Project in 1999, the Loess Plateau has become the [...] Read more.
China’s Loess Plateau is both the largest and deepest loess deposit in the world, and it has long been one of the most severely eroded areas on Earth. With the implementation of the Grain-for-Green Project in 1999, the Loess Plateau has become the most successful ecological restoration zone, and soil organic carbon (SOC) sequestration has greatly increased. However, little is known about the balance of SOC sequestration and vegetation restoration on the Loess Plateau. Thus, this review focused on the SOC sequestration from vegetation restoration in this region. Firstly, the current situations and principal aspects of vegetation restoration processes were reviewed, and the effects of vegetation restoration on SOC sequestration were summarized. Secondly, based on the new technologies and methods for soil carbon (C) sequestration, the mechanism of soil microbial C sequestration was described from the molecular level of genes, and some management measures for SOC sequestration were summarized. Finally, we pointed out the main directions in C sequestration mechanisms for vegetation restoration depending on the basic process of the C cycle, which should integrate into physics, chemistry, and biology. Overall, this review will help us understand the SOC sequestration function and the ecological benefits of vegetation restoration on the Loess Plateau. Full article
(This article belongs to the Special Issue Effects of Disturbances on Forest Soil Biochemistry)
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