Forest Ecosystems In China Research Articles

Spatial size diversity in natural and planted forest ecosystems: Revisiting and extending the concept of spatial size inequality

Plant size diversity or plant size inequality is a much neglected aspect of plant diversity and biodiversity. And yet size diversity plays an important role in understanding the dynamics of plant diversity and natural mechanisms of maintaining plant diversity, which is of great significance in a time of ongoing global changes. In this study, we introduced and investigated a new measure of spatial size inequality, namely the size segregation function. The new characteristic depends on distance and turned out to be a meaningful and more general extension of the traditional size differentiation index, because it describes local size inequality more extensively. To test the size segregation function we analysed and modelled thirteen large, fully mapped plots from temperate and subtropical forest ecosystems in China. We tested and validated the new function through cluster analysis and a special variant of partial spatial reconstruction. Our results showed that the size segregation function discriminated well between different patterns of spatial size diversity in the complex, mostly natural forests of China. Two random-labelling tests used in the study also highlighted how closely linked spatial species and size diversity are in such species-rich forest ecosystems: Often each species represents a distinctive size range and then spatial size inequality can be interpreted as being a consequence of spatial species mingling. This close relationship between species and size should also be taken into account in analyses of species-rich plant populations. For practical conservation this implies that high size inequality can often be found where there is high species mingling and vice versa.

Variations of belowground C and N cycling between arbuscular mycorrhizal and ectomycorrhizal forests across China

Forests associating with arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi may have distinct belowground carbon (C) and nitrogen (N) cycle processes. However, there are little available data providing evidence for the effects of trees associating with mycorrhizal type on belowground C and N cycling in forest ecosystems in China. Here, we collected a database of 26 variables related to belowground C and N cycling from 207 studies covering 209 sampling sites in China, to better understand the variations in belowground C and N cycling between the two mycorrhizal types in forest ecosystems along a climatic gradient. The AM forests had significantly lower soil total C and N contents, and soil microbial biomass C and N, than ECM forests, probably due to differences in litter quality (N and C/N) between AM and ECM forest types. In contrast, AM forests had significantly higher litter input, litter decomposition and soil respiration than ECM forests. Temperature and precipitation had significant positive effects on litter input and decomposition, soil total C and N contents, and soil respiration in AM and ECM forests. Overall, our results indicated that mycorrhizal type strongly affected belowground C and N cycle processes in forest ecosystems. Moreover, AM forests are likely more sensitive and ECM forests have a greater ability to adapt to global climate change.

Comparative analysis of spatial variation in forest fire drivers between boreal and subtropical ecosystems in China

Drivers of forest fire are complex and may spatially vary between different ecosystems; thus their identification is critical for the development of effective fire management strategies. Here we identified the spatial distribution trend and drivers of forest fire over the period of 2000–2016 in the boreal and subtropical forest ecosystems in China using trend analysis and the geographically weighted negative binomial regression model (GWNBR). The results reveal that forest fires were generally shifting from the boreal to sub-tropical region and that there were significant (p < 0.05) spatial differences in fire drivers between boreal and subtropical forest ecosystems. Forest fires in the boreal ecosystem were driven by meteorological, topographic and human factors that had clear spatial variation. In contrast, forest fire occurrence in subtropical forest ecosystem was spatially stationary; i.e., constant throughout the area. Our results suggest that as socio-economy continues developing, the influence of human factors on forest fires in different ecosystems will be more complex. Future national forest fire management policies should consider local condition to establish region-specific management strategies due to significant spatial differences in major forest fire drivers between different ecosystems.

Mercury fluxes, budgets, and pools in forest ecosystems of China: A review

Mercury (Hg) retention in forest ecosystem plays a key role in global biogeochemical cycling. We present a comprehensive review of the research status of forest Hg in China to characterize the Hg budgets and pools. Averaged total Hg (THg) inputs at remote forests and rural and suburban forests in China are about 2–4-fold and 2.5–5-fold higher than the observed values in Europe and North America, respectively. The highly elevated THg inputs are mainly derived from the elevated atmospheric Hg concentrations and litterfall biomass. THg outputs from the forest ecosystems are much lower than the atmospheric depositions. The annual THg retentions range from 26.1 to 60.4 µg m−2 at subtropical forests and from 12.4 to 26.2 µg m−2 at temperate forests. Given the large areal coverage, THg retention in forest is ∼69 t year−1 in China and is much high than that in global scale estimated by models. The much higher THg retention has elevated the THg pools in Chinese subtropical forests. This study has implication for the role of China forests in the global Hg biogeochemical cycle and the optimization of atmospheric Hg transport and deposition models.

Conservative allocation strategy of multiple nutrients among major plant organs: From species to community

Abstract Nutrient allocation is an important aspect of plant resource uptake and use, which is related to life‐history strategies. Although to date considerable attention has focused on plant allocation of nitrogen and phosphorus, comparatively little information is available on the allocation of various other nutrients and their up‐scaling from the species to community level. We measured 10 nutrient elements in the leaves, branches and fine roots of 551 plant species growing in eight forest ecosystems in China, ranging from cold temperate to subtropical forests. We estimated the scaling relationship of multiple nutrients among plant organs at the species level and scaled‐up the relationship to the community level by combining this information with that of community structure. Nutrient allocation among plant organs was conserved in different functional groups and biomes across broad environmental gradients. Nutrient partitioning between organs with similar function tended to be isometric, whereas partitioning between organs with distinct functions tended to be allometric. The scaling relationship between above‐ and below‐ground organs remained consistent, whereas the scaling relationship within above‐ground organs changed after scaling up from the species to the community level, with the relative change in nutrients being consistently smaller in the more active organs. Synthesis. The pattern of multiple nutrient allocation among organs showed a degree of conservatism across plant functional groups and biomes, with disproportional changes in nutrient content between functionally distinct organs and a lower relative change in more active organs. This conservative strategy implies the existence of general rules that constrain plant nutrient allocation.

Widespread asymmetric response of soil heterotrophic respiration to warming and cooling

Soil is the largest organic carbon (C) pool in terrestrial ecosystems. Periodic changes in environmental temperature occur diurnally and seasonally; yet, the response of soil organic matter (SOM) decomposition to varying temperatures remains unclear. In this study, we conducted a modified incubation experiment using soils from 16 forest ecosystems in China with periodically and continuously varying incubation temperature to investigate how heterotrophic respiration (Rh) responds to different temperature patterns (both warming and cooling temperature ranging between 5 and 30°C). Our results showed a pronounced asymmetric response of Rh to temperature warming and cooling among the soils of all forest ecosystems, with Rh increasing more rapidly during the warming phase compared to the cooling phase. This asymmetric response of Rh to warming and cooling temperatures was widespread in all soils. In addition, the amplitude of this asymmetric response differed among different forest ecosystems, with subtropical and warm-temperate forest ecosystems exhibiting greater asymmetric responses. Path analyses showed that soil pH and the microbial community explained most of the variation in this asymmetric response. Furthermore, the widespread asymmetric response of Rh to warming and cooling temperatures suggests that accumulated SOM decomposition might be overestimated on average by 20% for warming alone when compared with admix warming and cooling. These findings provide new insights on the responses of Rh to natural shifts in temperature, emphasizing the need to consider this widespread asymmetric response of Rh to warming and cooling phases to predict C-climate feedback with great accuracy, especially under future non-uniform warming scenarios.

A Review on Impact of Coupling System and Forest Ecosystem from the Prospect of China

This review paper focused on coupling system and forest ecosystem in China with emphasis on opportunities and challenges about coupling system concepts, forest ecosystem services, and climate change. The logistics, information, and energy flows are the key factors of the coupling system. Climate change is a sensitive issue for forest ecosystems which lead to global warming. It is evident from the literature that mechanisms of forest ecosystems, interactions and regional climatic system impact on climate change which lead for uncertainties. Theoretical studies can improve the scaling issues, experimental technology, as well as forest vegetation, mountain timberline which will positively impact on human activities.

A Review on Impact of Coupling System and Forest Ecosystem from the Prospect of China

This review paper focused on coupling system and forest ecosystem in China with emphasis on opportunities and challenges about coupling system concepts, forest ecosystem services, and climate change. The logistics, information, and energy flows are the key factors of the coupling system. Climate change is a sensitive issue for forest ecosystems which lead to global warming. It is evident from the literature that mechanisms of forest ecosystems, interactions and regional climatic system impact on climate change which lead for uncertainties. Theoretical studies can improve the scaling issues, experimental technology, as well as forest vegetation, mountain timberline which will positively impact on human activities.

退化森林生态系统评价指标体系研究进展

PDF HTML阅读 XML下载 导出引用 引用提醒 退化森林生态系统评价指标体系研究进展 DOI: 10.5846/stxb201805301196 作者: 作者单位: 中国科学院生态环境研究中心 城市与区域生态国家重点实验室,中国科学院生态环境研究中心,中国科学院生态环境研究中心 城市与区域生态国家重点实验室,中国科学院生态环境研究中心 城市与区域生态国家重点实验室,中国科学院生态环境研究中心 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2016YFC0502102）；中国科学院战略性先导科技专项课题（XDA20020402）；中国科学院科技服务网络计划项目（KFJ-STS-ZDTP-036） Review of the evaluation index system for degraded forest ecosystems Author: Affiliation: State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-Environmental Science,Chinese Academy of Sciences,,,,State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-Environmental Science,Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:森林是陆地生态系统的主要组成部分，而森林退化是全球面临的主要环境问题之一，准确评价退化森林生态系统是进行森林生态系统恢复与重建的重要前提，建立合理的评价指标体系目前已成为生态学研究的热点问题。在研究国内外提出的关于退化森林生态系统评价理论的基础上，综述了森林退化的定义、特征和一般过程，梳理了退化森林生态系统评价指标筛选的一般原则和指标体系构建的主要方法，分析比较了不同学者所提出的主要评价指标。并在此基础上，重新筛选、构建了一套退化森林生态系统评价指标体系，即从生态系统的组成结构、功能和生境这3个方面选取了32个能够较全面反映退化生态系统主要特征的评价指标，以期为构建我国区域尺度上的退化森林生态系统评价指标体系提供参考，为退化森林生态系统的恢复和重建提供科学依据。总结分析了退化森林生态系统评价指标体系在构建过程中产生的一些问题和不足，提出了今后开展研究和探索应该深入的方向，以提高评价指标体系的科学性、准确性和合理性。 Abstract:Forests are the major components of terrestrial ecosystems, and degradation of forests has become a major environmental problem worldwide. Accurate evaluation of degraded forest ecosystems is the primary prerequisite for forest restoration and reconstruction. Recently, establishment of a rational evaluation index system for degraded forest ecosystems has received much attention. On the basis of numerous studies on degraded forest ecosystems, we reviewed the definition, characteristics, and general processes of forest degradation in this paper. We also summarized the general principles of indicator selection and main methods for establishing the evaluation index system. In addition, we analyzed and compared several types of indicators suggested by previous researchers. On this basis, we re-screened and established an evaluation index system for the assessment of degraded forest ecosystems. We selected 32 key evaluation indicators based on the composition, function, and habitat aspects of the ecosystem, that could synthetically reflect the degraded forest ecosystem. This may provide references for the establishment of an evaluation index system for degraded forest ecosystems at regional and national scales and a scientific basis for the restoration and reconstruction of degraded forest ecosystems in China. Moreover, some limitations during the establishment of the evaluation index system for degraded forest ecosystems were discussed, and the main issues were suggested to improve the scientific accuracy and rationality of the evaluation index system. 参考文献 相似文献 引证文献

Dynamics of Coarse Woody Debris Characteristics in the Qinling Mountain Forests in China

Coarse woody debris (CWD) is an essential component in defining the structure and function of forest ecosystems. Long-term dynamics of CWD characteristics not only affect the release rates of chemical elements from CWD, but also the species diversity of inhabiting plants, animals, insects, and microorganisms as well as the overall health of ecosystems. However, few quantitative studies have been done on the long-term dynamics of CWD characteristics in forest ecosystems in China. In this study, we conducted nine tree censuses between 1996 and 2016 at the Huoditang Experimental Forest in the Qinling Mountains of China. We quantified forest biomass including CWD and CWD characteristics such as decay states and diameter classes during this period and correlated with stand, site, and climatic variables. The forest biomass was dominated by live tree biomass (88%); followed by CWD mass (6%–10%). Understory biomass contributed only a small portion (1%–4%) of the overall biomass. Significant differences in average annual increment of CWD mass were found among forest stands of different species (p &lt; 0.0001). Forest biomass, stand age, forest type, aspect, slope, stand density, annual average temperature, and precipitation were all significantly correlated with CWD mass (p &lt; 0.05), with forest type exhibiting the strongest correlation (r2 = 0.8256). Over time, the annual mass of different CWD characteristics increased linearly from 1996–2016 across all forest types. Our study revealed that forest biomass, including CWD characteristics, varied by forest type. Stand and site characteristics (forest biomass, forest type, aspect, slope and stand density) along with temperature and precipitation played a major role in the dynamics of CWD in the studied forest ecosystems.

Understanding fire drivers and relative impacts in different Chinese forest ecosystems

In this study, spatial patterns and driving factors of fires were identified from 2000 to 2010 using Ripley's K (d) function and logistic regression (LR) model in two different forest ecosystems of China: the boreal forest (Daxing'an Mountains) and sub-tropical forest (Fujian province). Relative effects of each driving factor on fire occurrence were identified based on standardized coefficients in the LR model. Results revealed that fires were spatially clustered and that fire drivers vary amongst differing forest ecosystems in China. Fires in the Daxing'an Mountains respond primarily to human factors, of which infrastructure is recognized as the most influential. In contrast, climate factors played a critical role in fire occurrence in Fujian, of which the temperature of fire season was found to be of greater importance than other climate factors. Selected factors can predict nearly 80% of the total fire occurrence in the Daxing'an Mountains and 66% in Fujian, wherein human and climate factors contributed the greatest impact in the two study areas, respectively. This study suggests that different fire prevention and management strategies are required in the areas of study, as significant variations of the main fire-driving exist. Rapid socio-economic development has produced similar effects in different forest ecosystems within China, implying a strong correlation between socio-economic development and fire regimes. It can be concluded that the influence of human factors will increase in the future as China's economy continues to grow - an issue of concern that should be further addressed in future national fire management.

Regional variation in carbon sequestration potential of forest ecosystems in China

Enhancing forest carbon (C) storage is recognized as one of the most economic and green approaches to offsetting anthropogenic CO2 emissions. However, experimental evidence for C sequestration potential (C sp) in China’s forest ecosystems and its spatial patterns remain unclear, although a deep understanding is essential for policy-makers making decisions on reforestation. Here, we surveyed the literature from 2004 to 2014 to obtain C density data on forest ecosystems in China and used mature forests as a reference to explore C sp. The results showed that the C densities of vegetation and soil (0–100 cm) in China’s forest ecosystems were about 69.23 Mg C/ha and 116.52 Mg C/ha, respectively. In mature forests, the C sp of vegetation and soil are expected to increase to 129.26 Mg C/ha (87.1%) and 154.39 Mg C/ha (32.4%) in the coming decades, respectively. Moreover, the potential increase of C storage in vegetation (10.81 Pg C) is estimated at approximately twice that of soil (5.01 Pg C). Higher C sp may occur in the subtropical humid regions and policy-makers should pay particular attention to the development of new reforestation strategies for these areas. In addition to soil nutrients and environment, climate was an important factor influencing the spatial patterns of C density in forest ecosystems in China. Interestingly, climate influenced the spatial patterns of vegetation and soil C density via different routes, having a positive effect on vegetation C density and a negative effect on soil C density. This estimation of the potential for increasing forest C storage provided new insights into the vital roles of China’s forest ecosystems in future C sequestration. More importantly, our findings emphasize that climate constraints on forest C sequestration should be considered in reforestation strategies in China because the effects of climate were the opposite for spatial patterns of C density in vegetation and soil.

Driving forces and their effects on water conservation services in forest ecosystems in China

Identifying the driving forces that cause changes in forest ecosystem services related to water conservation is essential for the design of interventions that could enhance positive impacts as well as minimizing negative impacts. In this study, we propose an assessment concept framework model for indirect-direct-ecosystem service (IN-DI-ESS) driving forces within this context and method for index construction that considers the selection of a robust and parsimonious variable set. Factor analysis was integrated into two-stage data envelopment analysis (TS-DEA) to determine the driving forces and their effects on water conservation services in forest ecosystems at the provincial scale in China. The results showed the following. 1) Ten indicators with factor scores more than 0.8 were selected as the minimum data set. Four indicators comprising population density, per capita gross domestic product, irrigation efficiency, and per capita food consumption were the indirect driving factors, and six indicators comprising precipitation, farmland into forestry or pasture, forest cover, habitat area, water footprint, and wood extraction were the direct driving forces. 2) Spearman’s rank correlation test was performed to compare the overall effectiveness in two periods: stage 1 and stage 2. The calculated coefficients were 0.245, 0.136, and 0.579, respectively, whereas the tabulated value was 0.562. This indicates that the driving forces obviously differed in terms of their contribution to the overall effectiveness and they caused changes in water conservation services in different stages. In terms of the variations in different driving force effects in the years 2000 and 2010, the overall, stage 1, and stage 2 variances were 0.020, 0.065, and 0.079 in 2000, respectively, and 0.018, 0.063, and 0.071 in 2010. This also indicates that heterogeneous driving force effects were obvious in the process during the same period. Identifying the driving forces that affect service changes and evaluating their efficiency have significant policy implications for the management of forest ecosystem services. Advanced effectiveness measures for weak regions could be improved in an appropriate manner. In this study, we showed that factor analysis coupled with TS-DEA based on the IN-DI-ESS framework can increase the parsimony of driving force indicators, as well as interpreting the interactions among indirect and direct driving forces with forest ecosystem water conservation services, and reducing the uncertainty related to the internal consistency during data selection.

基于模型数据融合的中国温带和亚热带典型森林生态系统碳通量模拟

PDF HTML阅读 XML下载 导出引用 引用提醒 基于模型数据融合的中国温带和亚热带典型森林生态系统碳通量模拟 DOI: 10.5846/stxb201510132066 作者: 作者单位: 中国科学院地理科学与资源研究所,中国科学院地理科学与资源研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 中国科学院战略性先导科技专项（XDA05050600）；国家科技支撑计划（2013BAC03B00）；中国科学院科研信息化“科技领域云”项目（XXH12503-05-03） Carbon flux simulation of typical temperate and subtropical forest ecosystems in China based on model-data fusion approach Author: Affiliation: Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Science,Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Science Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:生态系统碳循环过程对水分响应的研究已成为全球变化关注的焦点问题之一。基于长白山温带针阔混交林与千烟洲亚热带人工针叶林观测站2003-2009年生长季的碳通量（NEE）和气象观测数据，综合考虑水分对光合、呼吸作用的影响，构建不同的NEE模型，并应用模型数据融合方法优化模型参数、遴选最适模型，系统分析了水分因子对不同森林生态系统碳循环的影响。结果表明：（1）优化后的模型参数均能被NEE实测数据较好约束。长白山生长季的光合、呼吸参数值均高于千烟洲，未考虑空气饱和水汽压差（VPD）的模型高估了千烟洲温度敏感性参数（Q10）值、低估了千烟洲基础呼吸速率参数（BR）值；（2）仅考虑VPD对光合作用影响的模型是长白山生长季碳通量模拟的最优模型，但模拟精度提高不显著。不同模型间碳通量组分模拟结果差异较小；（3）考虑VPD和土壤含水量对光合、呼吸作用共同影响的模型是千烟洲生长季碳通量模拟的最优模型，并且显著提高了模拟精度。未考虑水分的模型在生长季高估了总生态系统生产力（GEP）总量2.0%（21.85 g C/m2），同时更大幅度地高估了生态系统呼吸（RE）总量4.4%（38.02 g C/m2），从而导致NEE总量低估于实测值7.8%（18.55 g C/m2）。 Abstract:Moisture effect on the carbon balance of terrestrial ecosystems is a key issue in global change research. It is crucial to accurately analyze the response of terrestrial ecosystem carbon cycle to moisture. However, the carbon flux models responding to environmental factors rarely consider the moisture effects on photosynthesis and respiration simultaneously; meanwhile there are still large uncertainties in model structures and parameters. Thus, this study was designed to (1) choose the optimal carbon flux model with accurate parameters for different ecosystems through model-data fusion approach, reducing the uncertainties of modeled results; (2) systematically analyze the influence of water factors on carbon flux simulation, including gross ecosystem productivity (GEP), ecosystem respiration (RE) and net ecosystem exchange (NEE). To consider the effects of moisture on both GEP and RE, we developed four different NEE models. Then, based on carbon flux and meteorological data during growing season from 2003 to 2009 in Changbaishan temperate mixed forest (CBS) and Qianyanzhou subtropical coniferous plantation (QYZ), Markov Chain Monte Carlo was employed to estimate model parameters, and Bayesian Information Criterion was applied to choose the optimal model for two forest ecosystems. The results showed that (1) the posterior values of model parameters were normally distributed, indicating that the parameters were well constrained by NEE. Photosynthetic and respiratory parameter values of CBS were higher than those of QYZ during the growing season. The model without vapor pressure deficit (VPD) overestimated the value of temperature sensitivity (Q10) and underestimated the value of basal respiration rate (BR) in QYZ; (2) the model considering VPD only was the optimal model for CBS,but its performance was not improved much. The modeled flux components were similar among the four models; (3) the model considering both VPD and soil water content (Sw) was the optimal model for QYZ, and its performance was improved significantly. The model ignored water factors overestimated 2% (21.85 g C/m2) of the total GEP, and 4.4% (38.02 g C/m2) of the total RE, and therefore, underestimated 7.8% (18.55 g C/m2) of the total measured NEE during the growing season. 参考文献 相似文献 引证文献

Spatial pattern and environmental controls of annual litterfall production in natural forest ecosystems in China

Spatial pattern and environmental controls of annual litterfall production in natural forest ecosystems in China

Atmospheric wet and litterfall mercury deposition at urban and rural sites in China

Abstract. Mercury (Hg) concentrations and deposition fluxes in precipitation and litterfall were measured at multiple sites (six rural sites and an urban site) across a broad geographic area in China. The annual deposition fluxes of Hg in precipitation at rural sites and an urban site were 2.0 to 7.2 and 12.6 ± 6.5 µg m−2 yr−1, respectively. Wet deposition fluxes of Hg at rural sites showed a clear regional difference with elevated deposition fluxes in the subtropical zone, followed by the temporal zone and arid/semi-arid zone. Precipitation depth is the primary influencing factor causing the variation of wet deposition. Hg fluxes through litterfall ranged from 22.8 to 62.8 µg m−2 yr−1, higher than the wet deposition fluxes by a factor of 3.9 to 8.7 and representing approximately 75 % of the total Hg deposition at the forest sites in China. This suggests that uptake of atmospheric Hg by foliage is the dominant pathway to remove atmospheric Hg in forest ecosystems in China. Wet deposition fluxes of Hg at rural sites of China were generally lower compared to those in North America and Europe, possibly due to a combination of lower precipitation depth, lower GOM concentrations in the troposphere and the generally lower cloud base heights at most sites that wash out a smaller amount of GOM and PBM during precipitation events.

Emission-dominated gas exchange of elemental mercury vapor over natural surfaces in China

Abstract. Mercury (Hg) emission from natural surfaces plays an important role in global Hg cycling. The present estimate of global natural emission has large uncertainty and remains unverified against field data, particularly for terrestrial surfaces. In this study, a mechanistic model is developed for estimating the emission of elemental mercury vapor (Hg0) from natural surfaces in China. The development implements recent advancements in the understanding of air–soil and air–foliage exchange of Hg0 and redox chemistry in soil and on surfaces, incorporates the effects of soil characteristics and land use changes by agricultural activities, and is examined through a systematic set of sensitivity simulations. Using the model, the net exchange of Hg0 between the atmosphere and natural surfaces of mainland China is estimated to be 465.1 Mg yr−1, including 565.5 Mg yr−1 from soil surfaces, 9.0 Mg yr−1 from water bodies, and −100.4 Mg yr−1 from vegetation. The air–surface exchange is strongly dependent on the land use and meteorology, with 9 % of net emission from forest ecosystems; 50 % from shrubland, savanna, and grassland; 33 % from cropland; and 8 % from other land uses. Given the large agricultural land area in China, farming activities play an important role on the air–surface exchange over farmland. Particularly, rice field shift from a net sink (3.3 Mg uptake) during April–October (rice planting) to a net source when the farmland is not flooded (November–March). Summing up the emission from each land use, more than half of the total emission occurs in summer (51 %), followed by spring (28 %), autumn (13 %), and winter (8 %). Model verification is accomplished using observational data of air–soil/air–water fluxes and Hg deposition through litterfall for forest ecosystems in China and Monte Carlo simulations. In contrast to the earlier estimate by Shetty et al. (2008) that reported large emission from vegetative surfaces using an evapotranspiration approach, the estimate in this study shows natural emissions are primarily from grassland and dry cropland. Such an emission pattern may alter the current understanding of Hg emission outflow from China as reported by Lin et al. (2010b) because a substantial natural Hg emission occurs in West China.

Case-based evaluation of forest ecosystem service function in China.

The data of valuation of forest ecosystem service function (FESF) in 101 primary case studies of China were collected and obtained based on Specifications for Assessment of Forest Ecosystem Services in China (LY/T 1721-2008). FESF was then analyzed synthetically in terms of value coefficient. The results showed that the average value per unit area (VPUA) of FESF in China was 6.11×104 yuan·hm-2, and the order of VPUA of each service function was: water conservation (2.44×104 yuan·hm-2)> soil conservation (1.15×104 yuan·hm-2)> biodiversity conservation (1.00×104 yuan·hm-2)> carbon fixation and oxygen release (0.98×104 yuan·hm-2)> atmosphere environmental purification (0.28×104 yuan·hm-2)> forest recreation (0.23×104 yuan·hm-2)> action of forest against natural calamities (0.19×104 yuan·hm-2)> nutrient accumulation(0.16×104 yuan·hm-2). Water conservation, soil conservation, biodiversity conservation, carbon fixation and oxygen release were the four dominant service functions of forest ecosystem in China. The VPUA of FESF of the reserve level was higher than that of county level. The establishment of reserves played positive roles in biodiversity conservation and enhancement of service function, but the service function of forest recreation still existed with some insufficiency, and it needed to be further improved. Dominant service functions of forest ecosystem varied in different physicographic regions, and each type of service function presented different differentiation characteristics in space. The VPUA of FESF in South China was the highest up to 11.36×104 yuan·hm-2. The power regression correlation coefficients (R2) of the total value of FESF with forest area and forest stock volume were 0.905 (P<0.01) and 0.860 (P<0.01), respectively, indicating that forest area and forest stock volume were the two key factors affecting FESF and its total value. Moreover, latitude and mean annual precipitation also had significant effect on the VPUA of FESF.

Forest litterfall and its composition: a new data set of observational data from China

AbstractKnowledge of litterfall production and its allocation is important for understanding nutrient cycling and assessing productivity in forest ecosystems; however, available litterfall datasets are rare in China. Consequently, in the present study, data from published studies (1970–2014) on litterfall and its composition in forest ecosystems in China (excluding Hong Kong, Macao, and Taiwan) were collected, critically reviewed, and incorporated in a comprehensive forest litterfall data set for China. The data set included the following litterfall data: leaves, branches, reproductive parts (flowers and fruits), and miscellaneous. Moreover, associated information was also included, i.e., geographical location (latitude, longitude, altitude, aspect, and slope), climate [mean annual temperature (MAT) and mean annual precipitation (MAP)], stand description (forest type, dominant tree species, stand origin, stand age, mean DBH, mean tree height and stand density), and data collection regime (sample frequency and date, trap size, and number). The data set included 904 entries for 168 study sites, that were distributed in various climate zones with latitudes 18.26°–51.50° N, longitudes 82.25°–129.53° E and altitudes 0–4115 m above sea level (a.s.l.), covering broad climatic gradients (−5.4 to 25.4°C in MAT and 370 to 2800 mm in MAP). The data can be used to analyze spatio‐temporal dynamics of China's forest litterfall and its allocation, understand nutrient cycling and assess productivity in forest ecosystems. Finally, the data set is freely available for noncommercial scientific applications.

Soil respiration and carbon balance in a Moso bamboo (Phyllostachys heterocycla (Carr.) Mitford cv. Pubescens) forest in subtropical China

Abstract: Understanding spatial and temporal variation in soil respiration (RS) in different forest ecosystems is crucial to estimate the global carbon balance. Bamboo forest is a special forest type in southern China covering an area of 5.38 million ha, 70% of which are Moso bamboo (Phyllostachys heterocycla (Carr.) Mitford cv. Pubescens) forests. Bamboo forests contribute more than 10% to the whole carbon stock of forest ecosystems in China, and therefore play a critical role in the regional and national carbon balance. However, little information on the seasonal dynamic of RS and the carbon balance of Moso bamboo forests is available. In this study, litter removal and trenching methods were applied to partition RS into root respiration (RR), litter respiration (RL) and soil organic matter derived respiration (RM), and to study their seasonal dynamics and carbon balance in a pure Moso bamboo forest. Monthly RS, its source components and combined monthly environmental factors were measured. RS and its source components showed a significant seasonal variability with higher values from June to August and lower values from December to February driven by soil temperature and moisture (P < 0.001). Annual average RS, RR, RL and RM were 2.37, 0.69, 0.58 and 1.10 μmol m-2 s-1 with Q10 values of 1.25, 1.15, 1.19 and 1.26, respectively. Annual RS was 8.97 t C ha-1, and RR, RL and RM contributed 29%, 22% and 49%, respectively. Annual NEP was 4.72 t C ha-1 y-1, indicating that the Moso bamboo forest studied is a significant carbon sink.