Carbon Budget Of Forest Ecosystems Research Articles

Spatiotemporal variation and response of gross primary productivity to climate factors in forests in Qiannan state from 2000 to 2020

Accurate estimation of terrestrial gross primary productivity (GPP) is essential for quantifying the carbon exchange between the atmosphere and biosphere. Light use efficiency (LUE) models are widely used to estimate GPP at different spatial scales. However, difficulties in properly determining the maximum LUE (LUEmax) and downregulation of LUEmax into actual LUE result in uncertainties in the LUE-estimated GPP. The recently developed P model, a new LUE model, captures the adaptability of vegetation to the environment and simplifies parameterization. Site-level studies have proven the superior performance of the P model over LUE models. As a representative karst region with significant changes in forest cover in Southwest China, Qiannan is useful for exploring the spatiotemporal variation in forest GPP and its response to climate change for formulating forest management policies to address climate changes, e.g., global warming. Based on remote sensing and meteorological data, this study estimated the forest ecosystem GPP in Qiannan from 2000–2020 via the P model. This study explored the spatiotemporal changes in GPP in the study region over the past 20 years, used the Hurst index to predict future development trends from a time series perspective, and used partial correlation analysis to analyse the spatiotemporal GPP changes over the past 20 years in response to three factors: temperature, precipitation, and vapor pressure deficit (VPD). Our results showed that (1) the total amount of GPP and average GPP in Qiannan over the past 21 years (2000–2020) were 1.9 × 104 ± 2.0 × 103 MgC ha−1 year−1 and 1238.9 ± 107.9 gC m−2 year−1, respectively. The forest GPP generally increased at a rate of 6.1 gC m−2 year−1 from 2000 to 2020 in Qiannan, and this increase mainly occurred in the nongrowing season. (2) From 2000 to 2020, the forest GPP in Qiannan was higher in the southeast and lower in the northwest, indicating significant spatial heterogeneity. In the future, more than 70% of regional forest GPP will experience a weak increase in nonsustainability. (3) In Qiannan, forest GPP was positively correlated with both temperature and precipitation, with partial correlation coefficients of 0.10 and 0.11, respectively. However, the positive response of GPP to precipitation was approximately 70.47%, while that to temperature was 64.05%. Precipitation had a stronger restrictive effect on GPP than did temperature in this region, and GPP exhibited a negative correlation with VPD. The results showed that an increase in VPD inhibits GPP to some extent. Under rapid global change, the P model GPP provides new GPP data for global ecology studies, and the comparison of various stress factors allows for improvement of the GPP model in the future. The results of this study will aid in understanding the dynamic processes of terrestrial carbon. These findings are helpful for estimating and predicting the carbon budget of forest ecosystems in karst regions, clarifying the regional carbon absorption capacity, clarifying the main factors limiting vegetation growth in these regions, promoting sustainable regional forestry development and serving the “dual carbon goal.” This work has important guiding significance for policy formulation to mitigate climate change.

A High-Resolution Simulation of Forest Ecosystem Carbon Budget Change with Complex Terrain

Forest ecosystems represent important carbon sinks within terrestrial ecosystems. Simulating carbon budgets in forest ecosystems located within complex terrains forms the foundation for understanding global carbon cycle dynamics. In this study, employing the FORCCHN model and utilizing mountain climate data as forcing parameters, the impact of the terrain factors of the Changbai Mountain Nature Reserve on carbon budget change in 1998–2017 was studied. The dynamics and distribution patterns of carbon fluxes at different slope aspects and elevations were discussed. Findings demonstrated that between 1998 and 2017, the per-unit area gross primary production (GPP), net primary production (NPP), and net ecosystem production (NEP) for the Changbai Mountain Reserve were 839.35, 462.03, and 192.72 gC m −2 a −1 , respectively. The carbon fluxes varied significantly with elevation: the GPP of the north, south, and west and the NPP of the east, south, and west decreased, and the NEP of the south and west increased. The total amount in GPP and NPP of the Changbai Mountain Nature Reserve fluctuated slightly year by year, but the carbon sequestration capacity decreased from year to year. The reserve had an average annual total GPP, NPP, and NEP of 1.62, 0.89, and 0.37 TgC a −1 , respectively. The north was the strongest carbon sink in the study area, contributing 35.98%, 35.88%, and 36.80% to the total amount of GPP, NPP, and NEP, respectively. This study emphasized the significance of precise mountain meteorological data to accurately quantify the carbon fluxes of mountain forest ecosystems.

Evaluating Carbon Sink Potential of Forest Ecosystems under Different Climate Change Scenarios in Yunnan, Southwest China

Nature-based Solutions (NbS) can undoubtedly play a significant role in carbon neutrality strategy. Forests are a major part of the carbon budget in terrestrial ecosystems. The possible response of the carbon balance of southwestern forests to different climate change scenarios was investigated through a series of simulations using the forest ecosystem carbon budget model for China (FORCCHN), which clearly represents the influence of climate factors on forest carbon sequestration. Driven by downscaled global climate model (GCM) data, the FORCCHN evaluates the carbon sink potential of southwestern forest ecosystems under different shared socioeconomic pathways (SSPs). The results indicate that, first, gross primary productivity (GPP), ecosystem respiration (ER) and net primary productivity (NPP) of forest ecosystems are expected to increase from 2020 to 2060. Forest ecosystems will maintain a carbon sink, but net ecosystem productivity (NEP) will peak and begin to decline in the 2030s. Second, not only is the NEP in the SSP1-2.6 scenario higher than in the other climate change scenarios for 2025–2035 and 2043–2058, but the coefficient of variation of the NEP is also narrower than in the other scenarios. Third, in terms of spatial distribution, the carbon sequestration potential of northwest and central Yunnan is significantly higher than that of other regions, with a slight upward trend in NEP in the future. Finally, GPP and ER are significantly positively correlated with temperature and insignificantly correlated with precipitation, and the increasing temperature will have a negative and unstable impact on forest carbon sinks. This study provides a scientific reference for implementing forest management strategies and achieving sustainable development.

Net Primary Productivity of Forest Ecosystems in the Southwest Karst Region from the Perspective of Carbon Neutralization

The net primary productivity (NPP) of forest ecosystems is an important factor for understanding the carbon budget of forest ecosystems. There have been many studies on the spatialtemporal characteristics and change trends of the NPP in southwest areas based on observation and remote sensing models. A comprehensive view of the overall state of the research on the carbon budget and a deeper exploration of its laws and effects are needed to reach a clear conclusion and accurately assess the NPP of forests in southwest China. Therefore, in this paper, we aim to highlight the relevant achievements in the study of the NPP of forest ecosystems, to summarize the research progress and spatial–temporal distribution law of the estimation of the NPPs of forest ecosystems, to analyse the relationship between the NPP and climate factors (such as temperature, precipitation and VPD), and to identify the main unsolved issues and suggest directions for future research. Our summary is expected to serve as a reference for forest ecosystem carbon budget management in the southwest and as a starting place for further research, and to promote the realization of the “double carbon” goal.

Prediction of carbon distribution in the leaves of birch stands using normative tables

The intensity of anthropogenic impact on forests, according to many researchers, will increase in the next twenty years. In this regard, the area of deciduous plantings in the taiga zone will increase. Knowledge of carbon stocks in green biomass will allow the necessary calculations of the carbon budget of forest ecosystems to be made. Birch in the taiga zone is one of the most significant wood carbon sinks, especially in the initial period of growth. The article used a normative approach to assessing the carbon stock in the leaf fraction of birch plantations. As a result, a number of conclusions were drawn. The use of two series of distributions compiled for birch forests of the forest-steppe and taiga zones showed their insignificant difference in relation to the determination of leaf biomass. The disadvantage of using distribution series when estimating the carbon budget is the inherent linear nature of the dynamics, which does not correspond to the real conditions of the age development of the assimilation apparatus. When determining carbon stocks for the leaf fraction, a high percentage of uncertainty is observed, this is noted by many researchers. To improve the accuracy of estimates of the biological productivity of birch plantations, it is necessary to use local standards and local research data to the maximum.

Stock of standing dead trees in boreal forests of Central Siberia

A significant part of carbon assimilated by forest is deposited in tree trunks. Growth and development of tree stands is accompanied by accumulation of standing dead trees (snags) due to natural tree mortality and as a result of the impact of exogenous factors. Carbon accumulated in these dead trunks is excluded from the fast turnover due to low rate of wood decomposition, so that snags can be considered as a pool of organic carbon with a slow rate of its return to the atmosphere. We estimated stock of snags on 54 sample plots, which represent the main types of forest ecosystems in the northern and middle taiga of Central Siberia. In the middle taiga, stock of snags varied from up to 7 m3 ha-1 in Siberian spruce forests to 20-42 m3 ha-1 in Scots pine forests. Larch forests in the northern taiga had the similar stock of snags as larch forests in the middle taiga despite significantly higher growing stock in the later. Snags contributed from 4 to 19% to the total stock of woody biomass in studied forests. This study indicated the significance of snags and can be used to estimate carbon budget of forest ecosystems of the region.

Effect of thinning intensity on the stem CO2 efflux of Larix principis-rupprechtii Mayr

BackgroundStem CO2 efflux (ES) plays a critical role in the carbon budget of forest ecosystems. Thinning is a core practice for sustainable management of plantations. It is therefore necessary and urgent to study the effect and mechanism of thinning intensity (TI) on ES.MethodsIn this study, five TIs were applied in Larix principis-rupprechtii Mayr 21-, 25-, and 41-year-old stands in North China in 2010. Portable infrared gas analyzer (Li-8100 A) was used to measure ES and its association with environmental factors at monthly intervals from May to October in 2013 to 2015. In addition, nutrients, wood structure and nonstructural carbon (NSC) data were measured in August 2016.ResultsThe results show that ES increased with increasing TI. The maximum ES values occurred at a TI of 35 % (3.29, 4.57 and 2.98 µmol∙m-2∙s-1) and were 1.54-, 1.94- and 2.89-fold greater than the minimum ES value in the CK stands (2.14, 2.35 and 1.03 µmol∙m-2∙s-1) in July for the 21-, 25- and 41-year-old forests, respectively. The ES of the trees in low-density stands was more sensitive to temperature than that of the trees in high-density stands. Soluble sugars (SS) and temperature are the main factors affecting ES. When the stand density is low enough as 41-year-old L. principis-rupprechtii forests with TI 35 %, bark thickness (BT) and humidity should be considered in addition to air temperature (Ta), wood temperature (Tw), sapwood width (SW), nitrogen concentration (N) and SS in the evaluation of ES. If a change in stand density is ignored, the CO2 released from individual 21-, 25- and 41-year-old trees could be underestimated by 168.89 %, 101.94 % and 200.49 %, respectively. CO2 release was estimated based on the stem equation in combination with the factors influencing ES for reference.ConclusionsWe suggest that it is not sufficient to conventional models which quantify ES only by temperature and that incorporating the associated drivers (e.g. density, SS, SW and N) based on stand density into conventional models can improve the accuracy of ES estimates.

Integrated remote sensing and model approach for impact assessment of future climate change on the carbon budget of global forest ecosystems

At present, global warming is an indisputable fact, and more and more attention has been paid to the impacts of climate warming on global ecological environments. Forests play increasing significant roles in regulating global carbon balance and mitigating climate change. Therefore, to understand the response mechanisms of the carbon budget of global forest ecosystems to future climate change, an improved version of the FORest ecosystem Carbon budget model for CHiNa (FORCCHN) and future Representative Concentration Pathway (RCP) scenario RCP4.5 and RCP8.5 were applied in this study. The results demonstrated that the global forest ecosystems will play a major role in the carbon sink under the future two climate change scenarios. In particular, the average carbon budget of global forest ecosystems under RCP4.5 scenario was estimated to be 0.017 kg(C)·m−2·yr−1 from 2007 to 2100. The future carbon sink areas of global forest ecosystems will increase significantly. Under RCP4.5 and RCP8.5 climate scenarios, the carbon sink areas of global forest ecosystems during 2026–2100 would be significantly been expanded than those in 2007–2025, with increases of 83.16–87.26% and 23.53–29.70%, respectively. The impacts of future climate change on carbon budget of global forest ecosystems will significantly vary between different regions. The carbon budget of forests will be enhanced in the northern hemisphere and significantly weakened in the southern hemisphere under the future two climate change scenarios. The carbon sink regions of global forests will be mainly distributed in the middle and high latitudes of the northern hemisphere. In particular, the forests' carbon budget in northeastern and central Asia, northern Europe and western North America will increase by 40% ~ 80%. However, the carbon budget of forests will decrease by 20% ~ 40% in the most regions of the southern hemisphere. In northern South America and central Africa, the forests' carbon budget will be reduced by more than 40%. In the future, in some areas of southern hemisphere, where the forests' carbon budget was predicted to be reduced, some measures for improving forest carbon sink, such as strengthening forest tending, enforcing prohibiting deforestation laws and scientific forest management, and so on, should be implemented to ensure immediate mitigation and adaptation to climate change.

Modified photochemical reflectance index to estimate leaf maximum rate of carboxylation based on spectral analysis.

The maximum rate of carboxylation in leaves (Vcmax) is an important parameter used to determine the photosynthetic rate. An accurate estimation of Vcmax is important for evaluating the photosynthetic capacity of vegetation productivity and the carbon budget of forest ecosystems. In this study, we measured the light use efficiency (LUE) and Vcmax of leaves and their corresponding spectral characteristics. Spectral analysis was used to find a modified photochemical reflectance index (PRI) of leaves to estimate LUE and thereby estimate leaf Vcmax. The results showed that the precision with which the modified ratio PRI index estimated LUE was significantly increased. The R2 of the estimation model was 0.69, and the root mean square error (RMSE) was 0.0024. The R2 of the model for estimating leaf Vcmax based on the LUE was 0.72, and the RMSE was 8.439 μmol/m2/s. The Vcmax values of conifer trees (Scots pine, Korean pine, and larch) were higher than those of broadleaf trees (white birch, Manchurian walnut, Siberian elm, Manchurian ash, Mongolian oak, Korean aspen, and Amur linden). This method avoids problem that conventional PRI is not sensitive to high leaf LUE values and provides important parameter data for the quantitative estimation of the gross primary productivity of forest ecosystems.

Application of Mathematical Models ROMUL and Romul_Hum for Estimating CO2 Emission and Dynamics of Organic Matter in Albic Luvisol under Deciduous Forest in the South of Moscow Oblast

The aim of this study was to validate the ROMUL and Romul_Hum simulation models based on the data of long-term measurements of soil respiration performed by the Institute of Physicochemical and Biological Problems in Soil Sciences of the Russian Academy of Sciences in the south of Moscow oblast (54°50′ N, 37°34′ E). We estimated the dynamics of carbon stocks and soil CO2 emission for three scenarios of plant litterfall compiled with the account of experimental data on the composition and mass of litterfall entering the gray forest soil (Albic Luvisol) under secondary deciduous forest. The calculations of long-term series of temperature and moisture content in the forest litter and upper organo-mineral soil horizons in simulation experiments are based on the real data on air temperature and precipitation for 1973–2016. The correspondence of simulation results to the data of field measurements was better for the Romul_Hum model, which comprises a description of the effects related to the vital activity of soil fauna, leading to the formation of different fractions of soil organic matter. The best correspondence of simulated values of CO2 emission, carbon stocks, and the C : N ratios in gray forest soil horizons to field data was for the litter scenarios, which excluded the fraction of small branches. The revealed differences between the simulated and real values of soil parameters are explained by specific features of the input and transformation of different litterfall fractions, which are not always taken into account during soil sampling. The results of the study attract the attention to the uncertainties of estimates of carbon budget in forest ecosystems due to the difficulties of accounting both large wood residues (dead tree and coarse branches debris) and smaller wood fractions in the litterfall.

PROJECT-ORIENTED MANAGEMENT OF ENVIRONMENTAL ENTREPRENEURSHIP IN THE REGIONS

Materials on the development of a modular project for the management and organization of an agricultural cooperative with systematic implementation of tasks and the achievement of commercial and environmental goals have been outlined. The carbon budget of forest ecosystems has been calculated and analyzed, the increase of which is aimed at increasing the yield of “clean” agricultural products with high benefit while reproducing natural systems that affect the improvement of its quality. The methodology and features of the project approach as an instrument for managing the complex economic, environmental and social problems posed by the environmental entrepreneurship of the regions have been analyzed. The economic and environmental performance indicators of the ecopreneur in the production of eco-products in the course of the project have been estimated. The results obtained are intended for associations of agricultural producers, local and regional executive authorities, interested in the development of environmental entrepreneurship and the reproduction of natural ecosystems.

Dissolved Organic Matter Characteristics and Important Site Factors in a Subtropical Mountain Forest in Central China

Abstract Dissolved organic matter is important in the vertical and lateral translocation of nutrients in forest ecosystems. However, little is known about the changes in dissolved organic matter concentration and chemical components in ecosystem sources in humid mountain forests. Here, we measured the concentration and chemical components of dissolved organic matter at throughfall, stemflow, litter leachate, runoff, and soil pore water (at depths of 10 cm, 30 cm, and 60 cm) in a subtropical humid mountain forest during two growing seasons. The concentration of dissolved organic carbon and dissolved nitrogen showed a clear monthly trend. The dissolved organic carbon concentration and the proportion of hydrophobic organic acid in the surficial water were higher than those in the soil pore water, and this difference was accompanied by a decrease in the hydrophobic organic acid concentration from the surficial water to the soil pore water. We also found that dissolved organic matter properties in surficial water were related to canopy cover, tree species, litter carbon content, and slope, whereas dissolved organic matter in soil pore water was associated with soil C, N, and P content and pH. In addition, the rainfall pattern is important to the dissolved organic matter concentration and partitioning within the seven sources. These findings showed that the dissolved organic carbon movement from surficial water into soil pore water is a significant component of carbon cycling in forest ecosystems, and this is important in estimating the carbon budget in forest ecosystems.

Evaluating impacts of climate change on net ecosystem productivity (NEP) of global different forest types based on an individual tree-based model FORCCHN and remote sensing

Abstract Accurately assessing the NEP of global forest ecosystem is indispensable to adjusting the global carbon balance for climate change. In this study, an improved individual-based forest ecosystem carbon budget model (FORCCHN) and remote sensing outputs were applied to investigate the impacts of climate change on the NEP of global different forest types from 1982 to 2011. The contributions of carbon sinks in different forest types to carbon sinks in global forest ecosystems were explored. The global forests were categorized into five ecological types according to their habitats and generic characteristics: deciduous coniferous forest (DCF), evergreen coniferous forest (ECF), evergreen coniferous deciduous broad-leaved mixed forest (ECDBMF), deciduous broad-leaved forest (DBF) and evergreen broad-leaved forest (EBF). The results showed that globally, the forest ecosystems represented a huge carbon sink and that the total carbon uptakes per unit area per year for EBF, ECF, DBF, DCF and ECDBMF forests from 1982 to 2011 were 0.388 kgC m−2·yr−1, 0.116 kgC m−2·yr−1, 0.082 kgC m−2·yr−1, 0.048 kgC m−2·yr−1 and 0.044 kgC m−2·yr−1, respectively. Inter-annual variability in global NEP per unit area per year among different forest types clearly existed. From 1982 to 2011, especially, the NEP increased in the EBF and ECF forests globally, but decreased in DBF forests. Moreover, there were no significant changes in the NEP of DCF and ECDBMF forests. The carbon sink areas varied among the 5 global forest types. For the DCF forest, central Asia, northern Europe and central North America were the main carbon sink regions. Central Asia, northern Europe and central North America were the main carbon sink regions for the ECF forest. For the ECDBMF forest, the carbon sink regions were mainly concentrated in northern and central Asia. The carbon sink regions for the DBF forest were mainly concentrated in southern Asia, southern Europe and mid-eastern North America. The carbon sink regions for the EBF forest were mainly concentrated in northern and central South America, southern Africa and southern Asia. Finally, the individual contributions of the NEP of each of forest type to global forest's NEP were calculated. The contributions of NEP for the EBF, ECF, DBF, DCF and ECDBMF forests to the total NEP of global forests were 57.19%, 17.07%, 12.17%, 7.10% and 6.47%, respectively. Our findings highlight that, over the past three decades, the EBF, ECF and DBF forests have been the main contributors to the increases in net ecosystem productivity of global forests.

Spatial–temporal variations of carbon storage of the global forest ecosystem under future climate change

Forests play an important role in sequestrating atmospheric carbon dioxide (CO2). Therefore, in order to understand the spatial–temporal variations and controlling mechanisms of global forest carbon (C) storage under future climate change, an improved individual-based forest ecosystem carbon budget model and remote sensing outputs in this study were applied to investigate the spatial–temporal dynamics of global forest (vegetation+soil) C storage in the future climate change scenario. The results showed that in the future RCP4.5 (representative concentration pathways) climate scenario, the total C storage per unit area per year in vegetation and soil of the global forest ecosystem showed a trend of first decreasing and then increasing from 2006 to 2100, with an average of 22.77 kg C m−2 year−1. However, the evolution trends of C storage changes in vegetation and soil were different. Moreover, the average soil C storage per unit area per year was 2.87 times higher than the average vegetation C storage. The impact of climate change on total C storage in vegetation and soil of the global forest ecosystems was positive, showing an obvious increase during 2006–2100. The total C storage varied significantly in spatial distribution. Spatially, the vegetation C storage and the soil organic C storage were projected to decrease significantly in most parts of South America and southern Africa in the Southern Hemisphere and increase in eastern North America, western Asia, and most areas of Europe in the Northern Hemisphere. Especially in the middle and high latitude regions of the Northern Hemisphere, the total forest C stock was projected to increase by 30–90% from 2046 to 2100. In the future, in these areas where forest C reserves were predicted to be reduced, it was suggested to increase afforestation, prohibit deforestation, and develop projects to increase forest C. Sustainable forest managements also offered opportunities for immediate mitigation and adaptation to climate change. Our findings provided not only a projection of C storage of global forest ecosystem responses to future climate change but also a useful methodology for estimating forest C storage at global levels.

Soil respiration and its temperature sensitivity among different vegetation types in Beijing mountain area, China.

As an important component of terrestrial ecosystem carbon cycle, soil respiration is a hot topic in the studies of carbon cycle. The temperature sensitivity (Q10) of soil respiration is a critical index to estimate the effects of global warming on soil respiration. Understanding Q10 of different vegetation types is of important significance for assessing the carbon budget of forest ecosystems. We examined soil respiration and its temperature sensitivity in three typical forests (Pinus tabuliformis, Platycladus orientalis, and Quercus variabilis) in the Beijing mountainous area by measuring the soil physical and chemical properties, soil temperature, soil moisture, and soil respiration rate (Rs) during the growing season. The results showed that Rs of three typical vegetation types showed a similar trend with changes of soil temperature and humidity, which showed a unimodal pattern, with minimum value (0.45 μmol·m-2·s-1) in early April and maximum value (3.95 μmol·m-2·s-1) in early July. There were significant differences in Rs and Q10 values among the three vegetation types. Soil temperature and humidity were the important factors affecting soil respiration, together they could explain the seasonal variation of soil respiration rate from 48.1% to 56.7%. The range of Q10 value was between 2.05 and 3.19. There was a significant negative correlation between soil organic carbon content and Q10 under each vegetation type (R2>0.9). Vegetation type, elevation, and soil organic carbon content were important drivers for the variation of Q10.

间伐和改变凋落物输入对华北落叶松人工林土壤呼吸的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 间伐和改变凋落物输入对华北落叶松人工林土壤呼吸的影响 DOI: 10.5846/stxb201703160449 作者: 作者单位: 北京林业大学林学院 北京 100083,北京林业大学林学院 北京 100083,北京林业大学林学院 北京 100083,北京林业大学林学院 北京 100083,北京林业大学林学院 北京 100083,北京林业大学林学院 北京 100083 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（2016YFD0600205） Thinning treatment and litterfall changes influence soil respiration in a Larix principis-rupprechtii plantation Author: Affiliation: Forestry College of Beijing Forestry University,Forestry College of Beijing Forestry University,Forestry College of Beijing Forestry University,Forestry College of Beijing Forestry University,Forestry College of Beijing Forestry University,Forestry College of Beijing Forestry University Fund Project: National Key R&D Plan 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:作为森林生态系统的第二大碳通量，土壤呼吸在全球碳循环和气候变化中发挥着重要作用。通过探究土壤呼吸对间伐和改变凋落物的响应规律以及响应之间的联系，能够为准确评价森林碳循环提供依据。针对不同强度（对照、轻度、中度、重度）间伐后的华北落叶松人工林，2016年5月至10月采用LI-8100土壤碳通量测量系统对其原状、凋落物去除、凋落物加倍的土壤呼吸进行观测。结果表明：土壤呼吸在生长季的8月份达到最高值，呈现出明显的季节动态。不同林分间伐处理下，中度间伐显著促进了土壤呼吸，使平均土壤呼吸速率升高了15.66%，轻度间伐和重度间伐对土壤呼吸的影响不显著；不同凋落物处理下，去除凋落物使平均土壤呼吸速率降低了40.16%，加倍凋落物使平均土壤呼吸速率升高了16.06%。中度间伐使土壤呼吸生长季通量增加了55.06 g C/m2；去除凋落物使土壤呼吸生长季通量减少了153.48 g C/m2，加倍凋落物使土壤呼吸生长季通量增加了79.87 g C/m2。土壤呼吸速率与土壤温度呈显著指数相关，而与土壤湿度无显著相关。不同林分间伐处理下，土壤呼吸的温度敏感性指数（Q10）为2.36-3.46，轻度间伐下Q10值最高；凋落物去除和加倍均降低了土壤呼吸的温度敏感性。土壤温湿度对土壤呼吸存在着显著影响，能够解释土壤呼吸28.7%-62.3%的季节变化。研究结果表明间伐和凋落物处理对华北落叶松人工林土壤CO2释放的影响表现出一定的交互作用，中度间伐和加倍凋落物的交互作用对土壤呼吸的促进作用显著大于单一因子。可见，间伐作业通过改变土壤微环境和凋落物量，对土壤呼吸以及森林生态系统碳循环产生着重要影响。 Abstract:Soil respiration (Rs), the second largest site of carbon flow in the forest ecosystem carbon budget, plays an important role in the global carbon (C) cycle and climate change. Understanding the effects of forest management practices (e.g. thinning) on Rs is crucial for the accurate estimation of forest carbon cycling. Simultaneously, aboveground litter management practices (removal, addition, and so on) can also influence Rs. However, little is known about the response of Rs to thinning and its relationship with the changes in litter production induced by thinning. We aimed to quantify the response of Rs rate to different thinning intensities and to explore the relationships between Rs and soil temperature and moisture as a result of different litter management practices. A thinning manipulation experiment was conducted in a Larix principis-rupprechtii plantation in Shanxi province, China, with the following treatments:heavy thinning, moderate thinning, low thinning and no thinning. In addition, three treatments-litterfall removal, litter addition and normal litterfall-were applied to analyze the relationship between differences in litter input and Rs. Rates of soil respiration were measured twice a month using the LI-8100 Automated Soil CO2 Flux System from May to October 2016, while soil temperature and moisture at a depth of 5 cm were measured using temperature and moisture probes and data loggers. A significant difference was noted in Rs among the different thinning treatments (P < 0.05). Clear monthly variations in Rs were noted in the growing season, and Rs reached its peak value in August. Overall, moderate thinning increased Rs rate during the growing season by 15.7% from that of the no-thinning treatment. During the growing season, the Rs rate was lower by 40.16% with litterfall removal than that of normal litterfall; however, Rs rate was higher by 16.06% with litter addition than that of normal litterfall. Moderate thinning increased accumulative Rs by 55.06 g C/m2 during the growing season. Under litter removal conditions, accumulative Rs decreased by 153.48 g C/m2 during the growing season, while accumulative Rs increased with litter addition by 79.87 g C/m2. During the growing season, Rs exhibited significant exponential relationships with soil temperature, while there were no significant differences in soil moisture among the various treatments. Temperature sensitivity (Q10) values of Rs ranged from 2.36 to 3.46 in the various thinning intensities, with the highest Q10 value in the low thinning stand. The Q10 value were lower with the litter removal and litter addition treatments than those of normal litterfall. The interaction of soil temperature and moisture had a significant effect on Rs. The best fitting model with temperature and moisture explained 28%-62% of the variation in Rs. The results indicated that the interaction between thinning treatments and litter changes has a significant effect on the Rs in L. principis-rupprechtii plantations. The compound effect of moderate thinning and litter addition on Rs is significantly greater than that of any single factor. In conclusion, thinning played a considerable role in altering Rs and carbon cycle in forest ecosystems by influencing the soil micro-environment and litter production rates. 参考文献 相似文献 引证文献

Life cycle research on the carbon budget of the Larix principis-rupprechtii plantation forest ecosystem in North China

Plantation forests play an important role in global carbon cycle. However, life cycle analysis on carbon budget of plantation forests was still poorly documented, especially regarding how forest management influence its carbon dynamics. Therefore, this study aims to bridge this gaps, taking Larix principis-rupprechtii plantation forest in North China for example. Based on established tree growth models and carbon stock models, we firstly discussed carbon dynamics of living trees; besides, carbon budgets of forest litter and soil were estimated by balancing its carbon inputs and carbon emissions (using the YASSO model). Forest management (including seedlings, site preparation and logging) can lead to carbon emissions due to material and energy consumption. Our findings were as follows: carbon sequestration by plantation forest amounted to 164.56 t C/ha during one 41-year rotation period in our study, most of which flowed into forest litter and soil. During one whole rotation period, forest litter and soil released out 100.21 tC/ha of sequestered carbon, while forest management resulted in about 1.59 tC/ha of carbon emissions. With forest plantation renewal, forest carbon storage increased due to more carbon stored in forest litter and soil, mainly existing in humus 1 and humus 2. Considering forest natural carbon dynamics, plantation forest functioned as the “carbon sink” during the first 5 rotation periods in our study, but the net carbon sink decreased from 35.95 tC/ha to 0.98 tC/ha. The increase of temperature and precipitation could result in more carbon emissions, and forest ecosystem carbon budget was more sensitive to precipitation changes than that to temperature changes.

Evaluating carbon fluxes of global forest ecosystems by using an individual tree-based model FORCCHN

The carbon budget of forest ecosystems, an important component of the terrestrial carbon cycle, needs to be accurately quantified and predicted by ecological models. As a preamble to apply the model to estimate global carbon uptake by forest ecosystems, we used the CO2 flux measurements from 37 forest eddy-covariance sites to examine the individual tree-based FORCCHN model's performance globally. In these initial tests, the FORCCHN model simulated gross primary production (GPP), ecosystem respiration (ER) and net ecosystem production (NEP) with correlations of 0.72, 0.70 and 0.53, respectively, across all forest biomes. The model underestimated GPP and slightly overestimated ER across most of the eddy-covariance sites. An underestimation of NEP arose primarily from the lower GPP estimates. Model performance was better in capturing both the temporal changes and magnitude of carbon fluxes in deciduous broadleaf forest than in evergreen broadleaf forest, and it performed less well for sites in Mediterranean climate. We then applied the model to estimate the carbon fluxes of forest ecosystems on global scale over 1982–2011. This application of FORCCHN gave a total GPP of 59.41±5.67 and an ER of 57.21±5.32PgCyr−1 for global forest ecosystems during 1982–2011. The forest ecosystems over this same period contributed a large carbon storage, with total NEP being 2.20±0.64PgCyr−1. These values are comparable to and reinforce estimates reported in other studies. This analysis highlights individual tree-based model FORCCHN could be used to evaluate carbon fluxes of forest ecosystems on global scale.

Current and future carbon budget at Takayama site, Japan, evaluated by a regional climate model and a process-based terrestrial ecosystem model.

Accurate projection of carbon budget in forest ecosystems under future climate and atmospheric carbon dioxide (CO2) concentration is important to evaluate the function of terrestrial ecosystems, which serve as a major sink of atmospheric CO2. In this study, we examined the effects of spatial resolution of meteorological data on the accuracies of ecosystem model simulation for canopy phenology and carbon budget such as gross primary production (GPP), ecosystem respiration (ER), and net ecosystem production (NEP) of a deciduous forest in Japan. Then, we simulated the future (around 2085) changes in canopy phenology and carbon budget of the forest by incorporating high-resolution meteorological data downscaled by a regional climate model. The ecosystem model overestimated GPP and ER when we inputted low-resolution data, which have warming biases over mountainous landscape. But, it reproduced canopy phenology and carbon budget well, when we inputted high-resolution data. Under the future climate, earlier leaf expansion and delayed leaf fall by about 10 days compared with the present state was simulated, and also, GPP, ER and NEP were estimated to increase by 25.2%, 23.7% and 35.4%, respectively. Sensitivity analysis showed that the increase of NEP in June and October would be mainly caused by rising temperature, whereas that in July and August would be largely attributable to CO2 fertilization. This study suggests that the downscaling of future climate data enable us to project more reliable carbon budget of forest ecosystem in mountainous landscape than the low-resolution simulation due to the better predictions of leaf expansion and shedding.

Effect of understory on a natural secondary forest ecosystem carbon budget

Lacking of detail data, forest carbon stock estimation with forest inventory data usually excludes or underestimates understory carbon storage. To quantify the effects of understory on carbon sequestration in a natural secondary Pinus tabulaeformis forest, organ biomass models for arbor, shrub to their growth indices were regressed. Biomass of herbage was estimated in a stratified sampling method. Soil respiration in forest land was measured. Based on above data, carbon budget of Pinus tabulaeformis forest was assessed as 1.882 CO2 Mghm−2year−1, 37.04% of the entire vegetation’s yearly net carbon storage belonging to understory.