Natural Broadleaf Forests Research Articles

Douglas fir and Norway spruce have similar effects on small mammal density, but not survival, in Central European managed forests

In an effort to ameliorate the impacts of climate change, forest managers in Central Europe increasingly turn to conifer species that produce higher yields and are better adapted to projected future climatic conditions. Though small mammals are an important component of the forest ecosystem, the impacts of enriching native broadleaf forests with conifers on small mammal communities are not well understood. We conducted mark–recapture surveys of small mammals to ascertain differences in their community structure among stands of two conifers (native Norway spruce Picea abies and non-native Douglas fir Pseudotsuga menziesii) and the dominant broadleaf in the region, European beech (Fagus sylvatica). After estimating the density of two common species, the yellow-necked mouse Apodemus flavicollis and bank vole Clethrionomys glareolus, we found that the population density of each is positively related to the proportion of beech and negatively to the proportion of conifers in each stand, though these effects of stand composition are smaller than the positive effect of herb cover. Increasing Norway spruce proportion reduced monthly survival of small mammals, while Douglas fir proportion had a positive effect on survival. We conclude that the two conifer species have similar impacts on small mammal density, though overall small mammal survival was significantly lower on plots with Norway spruce. This suggests that increasing the proportion of Douglas fir at the expense of Norway spruce may be possible without significantly changing local patterns of small mammal population density, but further research is necessary to elucidate the exact impacts of these two conifer species on small mammal demography and behavior.

Litterfall quality modulates soil ammonium and nitrate supply through altering microbial function in bamboo encroachment of broadleaf forests

Plant invasion can change soil microbial function and nitrogen (N) supply through the input of litter with different qualities and quantities, among other factors. However, the underlying mechanism for litter quality to regulate soil N mineralization via microbial function with plant invasion remains unclear. We examined the effect of litterfall with contrasting chemical properties on soil net ammonification and nitrification rates, enzyme activity, and associated microbial function using reciprocal litterfall transplanting between a natural broadleaf forest and a Moso bamboo forest formed after the encroachment of a natural broadleaf forest. Our results showed that, on average, litterfall removal decreased ammonification rates by 33.6% but increased nitrification rates by 137.8%, while litterfall replacement increased nitrification rates by 55.9% in the natural broadleaf forest. Litterfall removal increased ammonification rates by 33.9%, while litterfall replacement increased ammonification rates by 42.1% at the end of the experiment in the bamboo forest. Structural equation modeling revealed that higher quality litterfall (higher cellulose content and lower lignin/N ratio) from the broadleaf forest enhanced net ammonification by altering fungal composition and increasing their ligninolytic capacity. However, the lower quality litterfall from the bamboo forest increased net nitrification rates through altering bacterial community and increasing urease activity. Our results indicate that the increased N supply resulting from litterfall replacement could counteract the low NH4+ availability in the bamboo forest soil, but not in the broadleaf forest soil. The contrasting modulation effects of litterfall quality on soil mineral N production would have cascading effects on bamboo encroachment and forest succession with implications for ecosystem management.

Estimation of forest above‐ground biomass in Guangxi, China, by integrating forest age and stack learning

AbstractWith the implementation of large‐scale ecological restoration projects, Southwest China has become one of the fastest forest growth areas in the world in terms of vegetation cover and above‐ground biomass (AGB). It is expected to be a potential area for achieving the carbon neutrality target in China. Accurate estimation of forest AGB is becoming an increasingly urgent necessity for carbon neutrality and forest management. However, due to the complex geological background, there is significant uncertainty in estimating forest AGB in the southwestern region, which generally results in underestimating carbon sinks from forest restoration. To address the issue, we propose a method by incorporating forest age information and stack learning technique to estimate forest AGB. Based on remote sensing, forest inventory and in situ forest biomass data, three fundamental methods (Multiple regression, Random forest and Support vector machine) are employed and compared to build the AGB estimation model with vegetation indices, texture feature factors and forest age. Optimal basic models are further enhanced by integration learning to improve the estimation performance and then applied to the study area Guangxi to obtain regional AGB information of different forest types. The results show that: (1) forest age plays a vital role in reducing the uncertainty of AGB estimation. By incorporating forest age information, R2 of AGB estimation is improved by 0.07–0.27 and RMSE is decreased by 16.35%–47.47% for different forest types; (2) with R2 value >0.78, random forest model outperforms support vector machine and multiple linear regression models. Compared with the single optimal model, integration model by stack learning further enhances R2 of estimation by 0.02–0.03 and decreases RMSE by 5.20%–14.89%. (3) The total forest AGB in Guangxi is 988.17 Tg and the average forest AGB level is 73.30 t/ha. Natural broadleaf forest has the highest AGB level (86.75 t/ha), followed by natural coniferous forest (81.19 t/ha), planted coniferous forest (63.23 t/ha) and planted eucalyptus forest (49.71 t/ha). AGB level in karst areas is lower than that in non‐karst areas due to soil and water constraints. The majority of plantation forests in Guangxi is in the early and middle stages of forest succession, with the rapid growth of forest AGB, and has hence significant potential as carbon sinks. This study indicates that stack learning and incorporation of forest age could significantly decrease the uncertainty of forest AGB estimation. Our study helps to provide more accurate AGB information for karst ecological project management and regional carbon neutrality assessment.

Landscapes

The essay discusses the theoretical implications of ecological restoration in landscape architecture. The study presents a management plan for highly damaged peatlands in the Isle of Skye in Scotland, where the habitat is threatened by a radical forestation process. Being a natural carbon stock, damaged peatlands are a major source of greenhouse gas emissions. The project suggests gradually turning the case-study area's economy from tree farming to tourism, making the most out of the unique biodiversity of peatlands. The proposal traces a chronological activation plan of a touristic network that will run in parallel with the restoration of peats, native broadleaf forests, heather and cotton-grass meadows. Depending on the ability to recover of different soils, the restoration plan intends to gradually activate new dynamics in the landscape. The result is a stable “novel ecosystem” whose key interactions and processes are induced by new biotic and abiotic conditions. The article investigates and discusses possible strategies to develop a new kind of wilderness that differs from any previous condition and emerges from an alternative land use.

Dynamic of labile, recalcitrant carbon and nitrogen during the litter decomposition in a subtropical natural broadleaf forest

Dynamic of labile, recalcitrant carbon and nitrogen during the litter decomposition in a subtropical natural broadleaf forest

Tropical Cyclone Disturbances Induce Contrasting Impacts on Forest Structure, Plant Composition, and Soil Properties in Temperate Broadleaf and Coniferous Forests

Knowledge of forest recovery processes after severe disturbances, such as tropical cyclones, is essential for understanding the mechanisms maintaining forest diversity and ecosystem functioning. However, studies examining the impact of tropical cyclones on forest dynamics are still rare, especially in Northeast Asia. Here, we explore the complex responses of vegetation and soil chemistry to severe tropical cyclone disturbances in Hallasan National Park in South Korea. Vegetation and soil were examined five years before and five years after passages of tropical cyclones in 2012 in natural broadleaf and coniferous forests along an elevation gradient from 950 to 1770 m a.s.l., including the largest population of endemic Abies koreana. Tropical cyclones caused abundant tree mortality, resulting in a 46% decrease in stem basal area. Tropical cyclone disturbances triggered the spread of pioneer trees and shrubs and intense clonal propagation of graminoids, including dwarf bamboo, resulting in less diverse understory vegetation, especially in coniferous forests. In contrast, broadleaf forests at lower elevations experienced only minor disturbance. Opening of canopies after tropical cyclone disturbance led to the decrease in soil cations and doubling of available soil phosphorus stock, which likely contributed to the increased coverage of clonal graminoids, especially in coniferous forests (from 36 to 66%). Hence, increased competition of graminoids and reduction in seed fall and seedling recruitment prevented A. koreana regeneration. The subalpine forest dominated by A. koreana is forecasted to gradual loss due to the fact of temperature increases, intensified tropical cyclones and, particularly, due to the altered competition between dwarf bamboo and fir seedlings.

Recolonization by Indigenous broadleaved species of a conifer plantation (Cupressus spp.) in Northern Iran after 25 years

Key messageA vegetation analysis revealed the extent of recolonization by native vegetation of a 25-year-old Cupressus spp. plantation in northern Iran. A young indigenous Quercus-Carpinus community replaced the conifers in the low-slope areas with deeper, heavier, and more fertile soils.ContextReforestation of degraded or clear-cut-harvested lands can modify site conditions, facilitating succession and reestablishing native forests. It is critical to investigate the plantation in terms of vegetation, natural regeneration, and environmental variables to better understand ecological restoration.AimsThis study examines the recolonization of a Cypress plantation by native vegetation in the deforested Hyrcanian broadleaf forests and determines which edaphic, topographic, and structural variables are correlated to the degree of reconstitution.MethodsA systematic random sampling method was used to establish 55 plots in a 25-year-old Cupressus plantation, followed by plot classification using TWINSPAN and environment-vegetation analysis using CCA. The classification groups were compared using an analysis of variance. Tested variables included floristic composition, stand structure, regeneration, topography, and soil parameters.ResultsFour vegetation groups were identified based on an analysis of floristic composition. The first group demonstrated the least degree of native forest reconstitution, as planted conifers (Cupressus spp.) were established alongside pioneer broadleaf shrubs, enhancing Zelkova carpinifolia (Pall.) K.Koch regeneration. While most conifers disappeared in the third group, Carpinus betulus L., Zelkova carpinifolia, and Quercus castaneifolia C.A. Mey became dominant. The most influential environmental factors in reestablishing indigenous communities were a low-slope, heavier soil with a higher organic carbon and potassium content.ConclusionOn low-slope lands with fertile soils, the Hyrcanian native broadleaf forest can recolonize the coniferous plantation; however, on steep lands with poor sandy soils, planted Cupressus trees as well as relatively xerophytic shrubs in the understory may establish.

Changes in the composition of soil microbial communities and their carbon‐cycle genes following the conversion of primary broadleaf forests to plantations and secondary forests

AbstractThe soil organic carbon (C) cycle is primarily mediated by soil microorganisms and their genes that function in the C cycle (C‐cycle genes), both of which are strongly affected by land cover disturbance. However, the mechanism underlying microbially mediated soil C loss after conversion of primary natural broadleaf forests (BF) to plantation forests (PF) and secondary forests (SF) remains unknown. Here, we measured soil physicochemical properties and soil microbial community properties, and examined their linkages with microbial C‐cycle genes. Forest conversion dramatically decreased the richness of the soil fungal community but not of the bacterial community, and altered the composition of both communities. Analysis of C‐cycle genes revealed that the abundance of genes associated with C fixation, methane metabolism, and C degradation decreased by 51.3%, 57.9%, and 67.0%, respectively with the conversion of BF to PF; and by 6.3%, 4.1%, and 15.6%, respectively, with the conversion of BF to SF. The reductions in the abundance of C‐cycle genes, especially the reduction of hemicellulose‐ and lignin‐degradation genes, were primarily associated with the declines in the abundance of forest conversion‐sensitive microbes indexed by operational taxonomic units (fsOTUs, = 0.41). fsOTUs were taxonomically diverse and included members frequently co‐occurring with numerous other microbes in the microbial communities, indicating that the manipulation of fsOTUs by forest management could improve soil fertility and soil C sequestration. Forest conversion‐induced shifts in fsOTUs abundance were associated with changes in soil potassium permanganate oxidizable organic carbon (PXC) concentration, dissolved organic carbon (DOC) concentration, and soil pH. Our results indicate that alterations in soil substrate supply (e.g., DOC and PXC) and soil pH induced by forest conversion may strongly shape fsOTUs structure and decrease the abundance of hemicellulose and lignin degradation genes, and consequently increase C loss.

How Do Ground Litter and Canopy Regulate Surface Runoff?—A Paired-Plot Investigation after 80 Years of Broadleaf Forest Regeneration

Relatively minimal attention has been given to the hydrology of natural broadleaf forests compared to conifer plantations in Japan. We investigated the impacts of ground litter removal and forest clearing on surface runoff using the paired runoff plot approach. Plot A (7.4 m2) was maintained as a control while plot B (8.1 m2) was manipulated. Surface runoff was measured by a tipping-bucket recorder, and rainfall by a tipping-bucket rain gauge. From May 2016 to July 2019, 20, 54, and 42 runoff events were recorded in the no-treatment (NT), litter removed before clearcutting (LRBC), and after clearcutting (AC) phases, respectively. Surface runoff increased 4× when moving from the NT to LRBC phase, and 4.4× when moving from the LRBC to AC phase. Antecedent precipitation index (API11) had a significant influence on surface runoff in the LRBC phase but not in the NT and AC phases. Surface runoff in the AC phase was high regardless of API11. The rainfall required for initiating surface runoff is 38% and 56% less when moving from the NT to LRBC, and LRBC to AC phases, respectively. Ground litter and canopy function to reduce surface runoff in regenerated broadleaf forests.

Tree species composition and nutrient availability affect soil microbial diversity and composition across forest types in subtropical China

Soil microorganisms represent a significant component of terrestrial biodiversity and play a critical role in myriad ecological processes. The conversion of native forests to tree plantations is a major contributor to biodiversity loss on a global scale; however, our understanding of the influences of forest type conversion on soil microbial diversity and community composition remains unclear. Here we sampled twelve spatially interspersed stands of native mixed broadleaf forests, broadleaf-dominated (50–70% broadleaf trees), bamboo-dominated (20–40% broadleaf trees), and pure bamboo forests in subtropical China, to examine the effects of forest type conversion on soil bacterial and fungal diversity and composition. We found that the tree species richness, stand basal area, and soil carbon to nitrogen ratio decreased, while the total soil phosphorus increased from the native broadleaf forests to pure bamboo forests. Bacterial and fungal operational taxonomic units (OTUs) across the three soil depths increased significantly from 760 and 243 in native broadleaf to 795 and 336 in pure bamboo forests, respectively. However, neither bacterial nor fungal richness differed significantly among forest types at the phylum level. Across forest types, both bacterial and fungal OTU richness increased with the bamboo proportion and decreased with the soil carbon and nitrogen ratio. The fungal OTU richness also increased with the soil phosphorus content; however, neither bacterial nor fungal richness was affected by the tree species richness or stand basal area. Both bacterial and fungal community compositions changed with forest type and soil depth, with their compositional overlap from native broadleaf forests decreasing consistently with the bamboo proportion and soil phosphorus. Overall, our results provide insights into the importance of overstory tree composition and the availability of soil nutrients in affecting soil microbial diversity and composition, while providing management guidance for the inclusion of soil microbial diversity in forest conservation and management.

A comparison of hydrological characteristics between a cypress and mixed-broadleaf forest: Implication on water resource and floods

Broadleaf or conifer forest? – an ongoing dilemma as regards water resource and flood prevention. Although conifer trees use less water and are hydrophobic, existing studies at the watershed scale have shown varying results due to variability in meteorological conditions and forestry practices. In this study, two adjacent headwater catchments [2.42 ha cypress (CF); 2.08 ha mixed-broadleaf (MB)] were gauged. The study area in central Japan has a warm temperate climate with high annual rainfall and typhoons. Daily discharge (n = 1398) and storm event hydrographs (n = 242) were compared between CF and MB and discussed in light of water availability and storm event runoff characteristics. Overall water yield in CF was 6.4% lower than in MB but this was caused by lower streamflow on high discharge periods (30% frequency); thus, may not adversely affect municipal/agricultural water supply. For 70% of the time including during dry periods, water yield was higher in CF. This agrees with the principle that conifers use less water than broadleaf trees – even at the forested catchment scale. Discharge in the CF stream is also less variable than that in the MB stream. During storm events, the CF stream has higher flashiness (shorter response time to rainfall and higher peak discharge) than the MB stream; but in larger storms (≳70 mm), the MB stream may have higher peak discharge. Our data demonstrates that a well-managed plantation forest does not necessarily have inferior hydrological function compared to a natural broadleaf forest, which differs from the stereotype. Frequencies of high and low flows as well as runoff characteristics were also presented in hopes of promoting better forestry decisions when considering water demand and existing stormwater drainage infrastructures.

Carabid beetles (Coleoptera: Carabidae) in several types of forests on Hokkaido, Japan, with implications for forest management practices and beetle preservation

This study of the role the environment in the composition of the communities of carabid beetles was carried out in several types of forests at Obihiro and Furano, Hokkaido, Japan. In addition, we analysed the altitudinal distributions of two forest specialists, Damaster gehinii (Faimaire) and Procrustes kolbei Roeschke, which occur in six mountain forests on Hokkaido. At Obihiro, the forest specialist, P. kolbei was found at only one site in a large area of broadleaf forest. A redundancy analysis indicated that the carabid assemblages were significantly different in the different types of forest, and that two species, Leptocarabus arboreus arboreus (Lewis) and Leptocarabus opaculus opaculus (Putzeys), were associated with broadleaf forests. At Furano, a forest specialist D. gehinii and a forest generalist Cychrus morawitzi Gehin were mainly collected in natural broadleaf and mixed forests, whereas the percentage made up of L. o. opaculus was very high (80.8%) in natural broadleaf forest. Pterostichus thunbergii Morawitz made up the highest percentage of the species in the conifer plantations. In the six mountain forests, D. gehinii was scarce and mainly occurred at low altitudes; however, P. kolbei was relatively abundant and mainly recorded at middle to high altitudes. The management of the forests on Hokkaido needed to maintain the diversity and abundance of carabid beetles is discussed.

Thinned northern German Scots pine forests have a low carbon storage and uptake potential in comparison to naturally developing beech forests

In Europe, production forests with conifers widely replace native broadleaf trees. In the Pleistocene lowlands of northern Germany, > 1.7 million hectares of pine forests (Pinus spp., mostly P. sylvestris) have replaced natural broadleaf forests. We compared aboveground biomass carbon (C) pools and net primary productivity (ANPP) of broadleaf forests with natural development (ND; mostly Fagus sylvatica or Quercus petraea forests; 146 years old on average) to nearby young pine forests (YP; 65 years old on average) and old pine forests (OP; > 90 years) in northern Germany. Study aims where (i) to estimate the aboveground biomass C loss resulting from forest transformation, (ii) to compare the ANPP of broadleaf and pine forests, and (iii) to identify the main factors causing differences in biomass C storage and ANPP between forest types. YP forests stored only half of the biomass C of the ND forests (means: 72 vs. 147 MgCha−1); OP stands exceeded YP stands only by ~20% (87 vs. 72 MgCha−1). The main factor driving the biomass C pool differences was tree species identity, while stand age was not influential. Mean ANPP was 1.1 MgCha−1year−1 higher in ND forests than in YP stands due to higher litter production, while wood production was similar. We conclude that large-scale forest conversion to Scots pine forests has decreased the aboveground biomass carbon storage by half and the C sequestration potential with aboveground productivity by ~25%; this effect must be assessed together with changes in soil organic carbon stocks.

Improvements in Soil C and N Compositions After 40 and 80 Years of Reforestation in Subtropical Low Mountain Forests

AbstractReforestation is an important step toward recovering soil quality and wildlife habitats that are degraded due to deforestation. However, little is known about how soil C and N compositions in subtropical forests evolve after decades of reforestation. This study comprehensively evaluated the differences in soil C and N fractions in 40‐ and 80‐year‐old secondary (reforested) coniferous forests and a natural broadleaf forest. Although reforestation with coniferous plants appeared to increase soil organic matter and labile C levels, the ratio of soil labile C to total organic C was lower in the reforested coniferous forests than the natural broadleaf one. The trend in the labile N to total N ratio as coniferous reforestation progresses follows that of C. Furthermore, the percentage of recalcitrant C as total soil organic C was higher in the reforested coniferous forests than the natural broadleaf one. This feature of C composition in reforested coniferous forest causes environmental stress to microbes (as indicated by a high metabolic quotient) in the forest, even several decades after reforestation of a former broadleaf forest site. Results from this study demonstrate that it takes a very long time for reforestation with coniferous vegetation to restore the soil chemical properties of the previous natural forest.

Soil carbon dynamics in different types of subtropical forests as determined by density fractionation and stable isotope analysis

Quantifying carbon (C) dynamics with forest land-use change is essential for predicting C sequestration and stabilization. Here, we combined density fractionation and stable isotope analysis to examine soil C dynamics after primary native broadleaf forests (BF) were converted to secondary forests (SF) and plantation forests (PF). The results showed that soil C stock at 0–30 cm depth decreased significantly from BF (70.8 Mg ha−1) to SF (60 Mg ha−1) and PF (53.9 Mg ha−1). Both soil C concentration and stock decreased, but soil δ13C of the light and heavy fractions increased, and these increases were more evident in the topsoil (0–10 cm) than in the subsoil (10–30 cm). The decrease of the heavy fraction C stocks accounted for 52.7% and 69.7% of the reduction of bulk soil C stocks with conversion of BF to SF and PF, respectively. Analysis of δ13C revealed that the input of new C into the light fraction of soil at 0–10 cm depth decreased by 13.1% with conversion of BF to SF, and by 34.0% with conversion of BF to PF. The decreases of soil C stocks in density fractions were primarily explained by soil properties (β = 0.70) but also by vegetation biomass C (β = 0.26), and were closely correlated with soil moisture content (0.69, the highest eigenvalue among soil properties) and floor litter biomass C (0.75, the highest eigenvalue among biomass C categories). Our findings help clarify the contrasting mechanisms explaining the dynamics of light and heavy fraction of soil C, and highlight the importance of both vegetation and soil in controlling changes in soil C dynamics in response to forest conversion. Accordingly, we recommend that management policies and actions should maximize biomass C inputs of degraded forests and minimize C losses. It follows that the preservation of primary forests might increase ecosystem C sequestration and thereby mitigate climate change.

Effects of Simulated Acid Rain on Soil Fungi Diversity in the Transition Zone of Moso Bamboo and Broadleaf Forest

Acid rain is an important phenomenon in the context of global climate change, and can strongly influence forest ecology. There have been many studies on the response of plants to acid rain. However, the effect of acid rain on soil microbial communities is still largely unknown. Studying the effects of acid rain on soil microbial community structure is of great significance for predicting the interactive effects of multiple climate factors on forest ecosystems in the future. Moso bamboo (Phyllostachys edulis) is often cultivated not only for its delicious shoots and versatile culms, but also as an important biomass resource in southern China. However, with its robust growth and strong rhizomes, Moso bamboo populations have been expanding rapidly into adjacent forests. Different perturbation regimes, including disturbance caused by simulated acid rain, can have significant effects on a soil fungal community in response to Moso bamboo invasion into native broadleaf forest. To explore the effect of acid rain on a mixed forest of Moso bamboo and broadleaf soil fungi diversity, and to understand the relationship between fungal community structure and acid rain stress, a mixed forest of Moso bamboo and broadleaf (transition forest) in Zhejiang Tianmu Mountain Nature Reserve was taken as the study site, and simulated acid rain was set at different acidity according to the acid rain component of Linan in recent years. The experiment consisted of three different treatments. Three gradients of simulated acid rain treatment[pH 2.5, 4.0, and CK (lake water)] were designed to determine the effects of simulated acid rain on soil bacterial community diversity in transition forest. Soil DNA was extracted from the soils for polymerase chain reaction amplification and high-throughput sequencing to study the effects of acid rain on the fungal communities of the mixed forest of Moso bamboo and broadleaf soil. We obtained 601 287 sequences across the three types of sampling sites. Sequences were affiliated to 13 different phyla throughout the dataset. The dominant fungal groups were Ascomycota, Basidiomycota, Mortierellomycota, and Mucoromycota. Simulated acid significantly increased the number of operational taxonomic units, Ace index, and Chao1 index of fungal communities (P<0.05). The results of principal coordinates analysis (PCoA) also revealed that acid rain significantly modified the structure. The changes in soil fungal community structure were mainly related to the abundance of genera Bifiguratu, Geminibasidium, Purpureocillium, and Oidiodendron, which could be utilized as indicator species to determine changes in soil fungal community structure. Redundancy and correlation analysis showed that changes in basic physicochemical factors in the soil, such as soil pH and total nitrogen, can significantly influence the composition of the fungal community (P<0.05).

Dynamics of carbon, nitrogen, and phosphorus stocks and stoichiometry resulting from conversion of primary broadleaf forest to plantation and secondary forest in subtropical China

Large-scale primary native broadleaf forests (BF) have been converted to secondary forests (SF) and plantation forests (PF) in subtropical China over the past decades. However, how and what magnitude of plant and soil carbon (C), nitrogen (N), and phosphorus (P) stocks and stoichiometry are affected by forest conversion is still vague. Here, we addressed this issue by systematically measuring tree biomass and the C, N, and P concentrations in tree organs and soils (0–100 cm) collected from 300 plots in Fujian province. With forest conversion of BF to PF, the tree C, N, and P stocks declined by 43.8, 47.9, and 63.1%, respectively, and the soil C and N stocks across whole soil depth decreased by 19.1% and 13.0%, respectively, and these decreases were more evident after conversion of BF to PF than SF. However, soil P stock showed a tendency of decreasing at 0–20 cm soil depth but increasing at 20–100 cm soil depth following conversion of BF to SF and PF. This unconformity of the vertical pattern of P stock in contrast to C and N stocks, was perhaps due to higher C and N inputs and greater P uptake from the subsoil and its redistribution to the topsoil in BF than in SF and PF. The tree and soil C, N, and P stoichiometry was strongly related to tree biomass, indicating that tree biomass was a vital factor driving soil inputs and retention of nutrients, and thus affecting their stoichiometry. The leaf N:P ratios ranging from 16.7 to 17.2 at our study sites suggested that co-limitations of N and P for forest growth could occur in the studied region. Our results provided insights into the C, N, and P linkages between soils and trees as affected by forest conversion, and advised that predicting these linkages could be an effective approach to identify the impacts of forest conversion, thereby implementing targeted conservation and rehabilitation actions.

Effects of forest conversion on carbon-degrading enzyme activities in subtropical China

The mineralization of soil organic carbon (SOC) is primarily mediated by carbon (C) degrading enzyme. In the current study, we determined how the activities of four soil C-degrading enzymes, the hydrolases β-glucosidase (BG) and cellobiohydrolase (CBH) and the oxidases polyphenol oxidase (PPO) and peroxidase (POD), responded to forest conversion of natural broadleaf forests (BF) to secondary forests (SF) and plantation forests (PF) in subtropical China. We also quantified SOC, dissolved organic C (DOC), permanganate oxidase organic C (PXC), recalcitrant C (RC), microbial biomass C (MBC), mineral-associated C (MOC), soil particle-sizes distribution, pH, and moisture content, and C: nitrogen (N) ratio. Results showed that, the activities of all four C-degrading enzymes (BG, CBH, PPO and POD) decreased by 23.1, 9.5, 6.9 and 1.8%, respectively by forest conversion of BF to SF and 30.5, 15.3, 28.1 and 27.8%, respectively by conversion of BF to PF and were higher in the topsoil than in the subsoil. Relative to SF and PF, BF had higher hydrolase activities, which were related to its higher concentrations of MBC, DOC, and PXC, and to its lower C:N ratio. The BF also had higher oxidase activities, which were related to its higher concentrations of MBC, RC, and MOC, and to its lower C:N ratio. PF had higher specific enzyme activities (i.e., enzyme activities per unit of SOC) than BF and SF, indicating faster C turnover rates in PF. In addition to being affected by the concentrations of SOC and SOC components, forest conversion-induced changes in soil enzyme activities were affected by clay content and soil moisture content. These results revealed the different underlying mechanisms between soil hydrolases and oxidases in their responses to forest conversion.

Finite element analysis of trees in the wind based on terrestrial laser scanning data

Wind damage is an important driver of forest structure and dynamics, but it is poorly understood in natural broadleaf forests. This paper presents a new approach in the study of wind damage: combining terrestrial laser scanning (TLS) data and finite element analysis. Recent advances in tree reconstruction from TLS data allowed us to accurately represent the 3D geometry of a tree in a mechanical simulation, without the need for arduous manual mapping or simplifying assumptions about tree shape. We used this simulation to predict the mechanical strains produced on the trunks of 21 trees in Wytham Woods, UK, and validated it using strain data measured on these same trees.For a subset of five trees near the anemometer, the model predicted a five-minute time-series of strain with a mean cross-correlation coefficient of 0.71, when forced by the locally measured wind speed data. Additionally, the maximum strain associated with a 5 ms−1 or 15 ms-1 wind speed was well predicted by the model (N = 17, R2 = 0.81 and R2 = 0.79, respectively). We also predicted the critical wind speed at which the trees will break from both the field data and models and find a good overall agreement (N = 17, R2 = 0.40). Finally, the model predicted the correct trend in the fundamental frequencies of the trees (N = 20, R2 = 0.38) although there was a systematic underprediction, possibly due to the simplified treatment of material properties in the model. The current approach relies on local wind data, so must be combined with wind flow modelling to be applicable at the landscape-scale or over complex terrain. This approach is applicable at the plot level and could also be applied to open-grown trees, such as in cities or parks.

Effects of conversion from a natural evergreen broadleaf forest to a Moso bamboo plantation on the soil nutrient pools, microbial biomass and enzyme activities in a subtropical area

Converting natural forests to plantations would markedly change soil physiochemical and biological properties, as a consequence of changing plant vegetative coverage and management practices. However, the effects of such land-use change on the soil nutrient pools and related enzymes activities still remain unclear. The aim of this study was to explore the effects of conversion from natural evergreen broadleaf forests to Moso bamboo plantations on the pool sizes and forms of soil N, P and K, microbial biomass, and nutrient cycling related enzyme activities. Soil samples from four adjacent evergreen broadleaf forest-Moso bamboo plantation pairs were collected from a subtropical region in Zhejiang Province, China. The soil organic C (SOC), total N (TN), total P (TP) and total K (TK) concentrations and stocks and different N, P and K forms were measured, and the microbial biomass C (MBC), microbial biomass N (MBN), microbial biomass P (MBP) and four soil enzymes (protease, urease, acid phosphatase and catalase) were determined. The results showed that converting broadleaf forests to Moso bamboo plantations decreased the concentration and stock of SOC but increased those of TK in both soil layers (0–20 and 20–40 cm), and such land-use change increased the concentration and stock of TN and TP only in the 0–20 cm soil layer (P < 0.05). This land-use conversion increased the concentrations of NH4+-N, NO3−-N, resin-Pi, NaHCO3-Pi, NaOH-Pi, HCl-Pi, available K and slowly available K, but decreased the concentrations of water-soluble organic nitrogen (WSON), NaHCO3-Po and NaOH-Po (P < 0.05). Further, this land-use change decreased the microbial biomass and activities of protease, urease, acid phosphatase and catalase (P < 0.05). In addition, the acid phosphatase activity correlated positively with the concentrations of MBP and NaHCO3-Po, and the activities of urease and protease correlated positively with the concentrations of MBN and WSON (P < 0.01). To conclude, converting natural broadleaf forests to Moso bamboo plantations had positive effects on soil inorganic N, P and K pools, and negative effects on soil organic N and P pools, and on N- and P-cycling related enzyme activities. Therefore, management practices that increase organic nutrient pools and microbial activity are needed to be developed to mitigate the depletion of organic nutrient pools after the land-use conversion.