Carbon Balance Of Terrestrial Ecosystems Research Articles

Effects of 21st-century climate, land use, and disturbances on ecosystem carbon balance in California.

Terrestrial ecosystems are an important sink for atmospheric carbon dioxide (CO2), sequestering ~30% of annual anthropogenic emissions and slowing the rise of atmospheric CO2. However, the future direction and magnitude of the land sink is highly uncertain. We examined how historical and projected changes in climate, land use, and ecosystem disturbances affect the carbon balance of terrestrial ecosystems in California over the period 2001–2100. We modeled 32 unique scenarios, spanning 4 land use and 2 radiative forcing scenarios as simulated by four global climate models. Between 2001 and 2015, carbon storage in California's terrestrial ecosystems declined by −188.4 Tg C, with a mean annual flux ranging from a source of −89.8 Tg C/year to a sink of 60.1 Tg C/year. The large variability in the magnitude of the state's carbon source/sink was primarily attributable to interannual variability in weather and climate, which affected the rate of carbon uptake in vegetation and the rate of ecosystem respiration. Under nearly all future scenarios, carbon storage in terrestrial ecosystems was projected to decline, with an average loss of −9.4% (−432.3 Tg C) by the year 2100 from current stocks. However, uncertainty in the magnitude of carbon loss was high, with individual scenario projections ranging from −916.2 to 121.2 Tg C and was largely driven by differences in future climate conditions projected by climate models. Moving from a high to a low radiative forcing scenario reduced net ecosystem carbon loss by 21% and when combined with reductions in land‐use change (i.e., moving from a high to a low land‐use scenario), net carbon losses were reduced by 55% on average. However, reconciling large uncertainties associated with the effect of increasing atmospheric CO2 is needed to better constrain models used to establish baseline conditions from which ecosystem‐based climate mitigation strategies can be evaluated.

Research progress on the responses of soil respiration components to climatic warming.

Global carbon cycle is being profoundly altered by climate change. As an important component of the global carbon cycle, soil respiration is tightly linked to the carbon transfer among plants-soil-microbes. Soil respiration can be divided into the heterotrophic respiration and root-derived respiration (i.e., actual root respiration and rhizomicrobial respiration). Responses of soil respiration to climate warming may be different, since its components differ in occurrence sites and sources of soil organic carbon. However, the current literatures can not fully clarify the precise partition and quantification of soil respiration components. The influences of climate warming on soil respiration and related mechanisms are still unclear, which greatly limits our understanding of the accurate assessments of soil carbon cycle as well as the changes in the carbon balance of terrestrial ecosystems under climate change. We systematically summarized the progress of partitioning techniques of soil respiration components, and compared the results of partitioning of soil respiration components using different techniques. We further discussed the progress on the responses of soil respiration components to climate warming. To exactly distinguish and quantify soil respiration components, we proposed that the present techniques should be modified. Furthermore, future studies should focus on how to accurately partitioning root-derived respiration in the field for comprehensively understand soil carbon cycle and the changes of carbon budget in terrestrial ecosystems under global change. Moreover, more attention should be paid on the responses of soil respiration components to various environmental factors.

Effects of contemporary land-use and land-cover change on the carbon balance of terrestrial ecosystems in the United States

Changes in land use and land cover (LULC) can have profound effects on terrestrial carbon dynamics, yet their effects on the global carbon budget remain uncertain. While land change impacts on ecosystem carbon dynamics have been the focus of numerous studies, few efforts have been based on observational data incorporating multiple ecosystem types spanning large geographic areas over long time horizons. In this study we use a variety of synoptic-scale remote sensing data to estimate the effect of LULC changes associated with urbanization, agricultural expansion and contraction, forest harvest, and wildfire on the carbon balance of terrestrial ecosystems (forest, grasslands, shrublands, and agriculture) in the conterminous United States (i.e. excluding Alaska and Hawaii) between 1973 and 2010. We estimate large net declines in the area of agriculture and forest, along with relatively small increases in grasslands and shrublands. The largest net change in any class was an estimated gain of 114 865 km2 of developed lands, an average rate of 3282 km2 yr−1. On average, US ecosystems sequestered carbon at an annual rate of 254 Tg C yr−1. In forest lands, the net sink declined by 35% over the study period, largely a result of land-use legacy, increasing disturbances, and reductions in forest area due to land use conversion. Uncertainty in LULC change data contributed to a ~16% margin of error in the annual carbon sink estimate prior to 1985 (approximately ±40 Tg C yr−1). Improvements in LULC and disturbance mapping starting in the mid-1980s reduced this uncertainty by ~50% after 1985. We conclude that changes in LULC are a critical component to understanding ecosystem carbon dynamics, and continued improvements in detection, quantification, and attribution of change have the potential to significantly reduce current uncertainties.

Effect of rainfall events on soil carbon flux in mountain pastures

BackgroundLarge-scale land-use change is being caused by various socioeconomic problems. Land-use change is necessarily accompanied by changes in the regional carbon balance in terrestrial ecosystems and affects climate change. Therefore, it is crucial to understand the correlation between environmental factors altered by land-use change and the carbon balance. To address this issue, we studied the characteristics of soil carbon flux and soil moisture content related to rainfall events in mountain pastures converted from deciduous forest in Korea.ResultsThe average soil moisture contents (SMC) during the study period were 23.1% in the soil respiration (SR) plot and 25.2% in the heterotrophic respiration (HR) plot. The average SMC was increased to 2.1 and 1.1% in the SR and HR plots after rainfall events, respectively. In addition, saturated water content was 29.36% in this grassland. The soil water content was saturated under the consistent rainfall of more than 5 mm h−1 rather than short-term heavy rainfall event. The average SR was increased to 28.4% after a rainfall event, but the average HR was decreased to 70.1%. The correlation between soil carbon flux rates and rainfall was lower than other environmental factors. The correlation between SMC and soil carbon flux rates was low. However, HR exhibited a tendency to be decreased when SMC was 24.5%. In addition, the correlation between soil temperature and respiration rate was significant.ConclusionsIn a mountain pasture ecosystem, rainfall induced the important change of soil moisture content related to respiration in soil. SR and HR were very sensitive to change of SMC in soil surface layer about 0–10-cm depth. SR was increased by elevation of SMC due to a rainfall event, and the result was assumed from maintaining moderate soil moisture content for respiration in microorganism and plant root. However, HR was decreased in long-time saturated condition of soil moisture content. Root has obviously contributed to high respiration in heavy rainfall, but it was affected to quick depression in respiration under low rainfall. The difference of SMC due to rainfall event was causative of a highly fluctuated soil respiration rate in the same soil temperature condition. Therefore, rainfall factor or SMC are to be considered in predicting the soil carbon flux of grassland ecosystems for future climate change.

Contributions of wildland fire to terrestrial ecosystem carbon dynamics in North America from 1990 to 2012

AbstractBurn area and the frequency of extreme fire events have been increasing during recent decades in North America, and this trend is expected to continue over the 21st century. While many aspects of the North American carbon budget have been intensively studied, the net contribution of fire disturbance to the overall net carbon flux at the continental scale remains uncertain. Based on national scale, spatially explicit and long‐term fire data, along with the improved model parameterization in a process‐based ecosystem model, we simulated the impact of fire disturbance on both direct carbon emissions and net terrestrial ecosystem carbon balance in North America. Fire‐caused direct carbon emissions were 106.55 ± 15.98 Tg C/yr during 1990–2012; however, the net ecosystem carbon balance associated with fire was −26.09 ± 5.22 Tg C/yr, indicating that most of the emitted carbon was resequestered by the terrestrial ecosystem. Direct carbon emissions showed an increase in Alaska and Canada during 1990–2012 as compared to prior periods due to more extreme fire events, resulting in a large carbon source from these two regions. Among biomes, the largest carbon source was found to be from the boreal forest, primarily due to large reductions in soil organic matter during, and with slower recovery after, fire events. The interactions between fire and environmental factors reduced the fire‐caused ecosystem carbon source. Fire disturbance only caused a weak carbon source as compared to the best estimate terrestrial carbon sink in North America owing to the long‐term legacy effects of historical burn area coupled with fast ecosystem recovery during 1990–2012.

氮输入对东北土壤碳蓄积氮素利用效率的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 氮输入对东北土壤碳蓄积氮素利用效率的影响 DOI: 10.5846/stxb201509251968 作者: 作者单位: 中国农业科学院农业环境与可持续发展研究所,中国科学院地理科学与资源研究所,中国林业科学研究院森林生态环境与保护研究所,中国农业科学院农业环境与可持续发展研究所,中国农业科学院农业环境与可持续发展研究所,中国农业科学院农业环境与可持续发展研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31370463，41271118，31070398）；中国农业科学院科技创新工程项目 Effects of nitrogen input on nitrogen use efficiency of soil carbon storage in Northeast China Author: Affiliation: Institute of Environment and Sustainable Development in Agriculture,Chinese Academy of Agricultural Sciences,,Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry,,, 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:由于人类活动影响，通过沉降和施肥方式进入生态系统的活性氮显著增加，其对土壤有机碳库产生重要影响。氮素利用效率（NUE）作为深入理解陆地生态系统碳氮耦合关系的重要参数，对NUE时空规律的研究不仅可以评估目前氮输入对陆地生态系统碳汇增加的贡献，同时也有助于预测未来氮输入情况下陆地生态系统的碳平衡。利用生态系统过程模型——CEVSA2模型的模拟结果，分析了东北地区氮输入情况下，土壤碳的氮素利用效率（SNUE）的时空变化规律及其影响因素，结果表明：（1）1961-2010年，氮输入的显著增加促进了土壤碳的蓄积，但SNUE显著下降；（2）森林的平均SNUE最高，农田最低；灌丛的下降速率最大，森林的SNUE变化趋势最不显著；（3）三江平原和长白山地区以及大小兴安岭的部分地区SNUE最大，其次是辽河平原、松嫩平原地区；内蒙古高原、呼伦贝尔高原地区以及大、小兴安岭的部分地区SNUE出现负值，说明在这些地区，外援氮输入抑制了土壤碳的蓄积；（4）氮输入的空间分异和不同生态系统响应氮输入的差异共同决定了SNUE及其变化的空间格局。该研究结果可为进一步分析不同区域氮促汇潜力和预测未来氮输入情景下的区域碳平衡提供参考。 Abstract:Anthropogenic activities have altered the global nitrogen (N) cycle, leading to increased N input into the ecosystem through N deposition and the use of N fertilizers. Nitrogen is considered to be the limiting factor of plant growth in many ecosystems; therefore, the increased N input into ecosystems has an important impact on the carbon cycle and carbon accumulation. N use efficiency (NUE) can be an important indicator for the coupling relationship between ecosystem carbon and nitrogen cycles. Studies on the temporal and spatial patterns of NUE will aid in assessing the contribution of N input to increases in the terrestrial ecosystem carbon sink, and to predict the carbon balance of terrestrial ecosystems under different N input increase scenarios. We use a newly developed process-based ecosystem model, CEVSA2, to study the spatial and temporal variation in N use efficiency of soil carbon storage (SNUE) in Northeast China during 1961-2010, and to examine the effects of N input and vegetation types on SNUE. Our model simulations show that: (1) enhanced N input induced more soil carbon storage in the Northeast, but it decreased SNUE greatly. (2) Different vegetation types led to different SNUEs; forest had the highest SNUE and cropland had the lowest SNUE. The SNUEs of all vegetation types decreased with an increase in N input; however, the forest had the most stable SNUE compared to other vegetation types. The SNUE of shrubland decreased significantly during the early period of the past 50 years. (3) SNUE was the highest in the Sanjiang Plain, the Changbai Mountains, and parts of the Daxinganling and Xiaoxinganling regions. SNUE was negative in the Inner Mongolia Plateau, Hunlun Buir Plateau, and parts of the Daxinganling and Xiaoxinganling regions. This indicates that exogenous N input decreased the storage of soil carbon. (4) The variations in N input and the different responses of different vegetation type to N input impacted the spatial pattern of SNUE. The effects of N input on soil carbon accumulation are also affected by complex ecological processes. The complex responses and adaptation of soil processes to N addition will result in uncertain predictions for long-term changes if the model is based on short term observation results. Further efforts are required on the mechanisms of responses of soil processes to all environmental changes in order to accurately predict the effects that continued N addition will have on soil carbon storage in the future. 参考文献 相似文献 引证文献

The large influence of climate model bias on terrestrial carbon cycle simulations

Global vegetation models and terrestrial carbon cycle models are widely used for projecting the carbon balance of terrestrial ecosystems. Ensembles of such models show a large spread in carbon balance predictions, ranging from a large uptake to a release of carbon by the terrestrial biosphere, constituting a large uncertainty in the associated feedback to atmospheric CO2 concentrations under global climate change. Errors and biases that may contribute to such uncertainty include ecosystem model structure, parameters and forcing by climate output from general circulation models (GCMs) or the atmospheric components of Earth system models (ESMs), e.g. as prepared for use in IPCC climate change assessments. The relative importance of these contributing factors to the overall uncertainty in carbon cycle projections is not well characterised. Here we investigate the role of climate model-derived biases by forcing a single global ecosystem-carbon cycle model, with original climate outputs from 15 ESMs and GCMs from the CMIP5 ensemble. We show that variation among the resulting ensemble of present and future carbon cycle simulations propagates from biases in annual means of temperature, precipitation and incoming shortwave radiation. Future changes in carbon pools, and thus land carbon sink trends, are also affected by climate biases, although to a smaller extent than the absolute size of carbon pools. Our results suggest that climate biases could be responsible for a considerable fraction of the large uncertainties in ESM simulations of land carbon fluxes and pools, amounting to about 40% of the range reported for ESMs. We conclude that climate bias-induced uncertainties must be decreased to make accurate coupled atmosphere-carbon cycle projections.

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

Strong regional atmospheric 14C signature of respired CO2 observed from a tall tower over the midwestern United States

AbstractRadiocarbon in CO2 (14CO2) measurements can aid in discriminating between fast (<1 year) and slower (>5–10 years) cycling of C between the atmosphere and the terrestrial biosphere due to the 14C disequilibrium between atmospheric and terrestrial C. However, 14CO2 in the atmosphere is typically much more strongly impacted by fossil fuel emissions of CO2, and, thus, observations often provide little additional constraints on respiratory flux estimates at regional scales. Here we describe a data set of 14CO2 observations from a tall tower in northern Wisconsin (USA) where fossil fuel influence is far enough removed that during the summer months, the biospheric component of the 14CO2 budget dominates. We find that the terrestrial biosphere is responsible for a significant contribution to 14CO2 that is 2–3 times higher than predicted by the Carnegie‐Ames‐Stanford approach terrestrial ecosystem model for observations made in 2010. This likely includes a substantial contribution from the North American boreal ecoregion, but transported biospheric emissions from outside the model domain cannot be ruled out. The 14CO2 enhancement also appears somewhat decreased in observations made over subsequent years, suggesting that 2010 may be anomalous. With these caveats acknowledged, we discuss the implications of the observation/model comparison in terms of possible systematic biases in the model versus short‐term anomalies in the observations. Going forward, this isotopic signal could be exploited as an important indicator to better constrain both the long‐term carbon balance of terrestrial ecosystems and the short‐term impact of disturbance‐based loss of carbon to the atmosphere.

Photodegradation alleviates the lignin bottleneck for carbon turnover in terrestrial ecosystems

A mechanistic understanding of the controls on carbon storage and losses is essential for our capacity to predict and mitigate human impacts on the global carbon cycle. Plant litter decomposition is an important first step for carbon and nutrient turnover, and litter inputs and losses are essential in determining soil organic matter pools and the carbon balance in terrestrial ecosystems. Photodegradation, the photochemical mineralization of organic matter, has been recently identified as a mechanism for previously unexplained high rates of litter mass loss in arid lands; however, the global significance of this process as a control on carbon cycling in terrestrial ecosystems is not known. Here we show that, across a wide range of plant species, photodegradation enhanced subsequent biotic degradation of leaf litter. Moreover, we demonstrate that the mechanism for this enhancement involves increased accessibility to plant litter carbohydrates for microbial enzymes. Photodegradation of plant litter, driven by UV radiation, and especially visible (blue-green) light, reduced the structural and chemical bottleneck imposed by lignin in secondary cell walls. In leaf litter from woody species, specific interactions with UV radiation obscured facilitative effects of solar radiation on biotic decomposition. The generalized effect of sunlight exposure on subsequent microbial activity, mediated by increased accessibility to cell wall polysaccharides, suggests that photodegradation is quantitatively important in determining rates of mass loss, nutrient release, and the carbon balance in a broad range of terrestrial ecosystems.

Development of the BIOME-BGC model for the simulation of managed Moso bamboo forest ecosystems

Numerical models are the most appropriate instrument for the analysis of the carbon balance of terrestrial ecosystems and their interactions with changing environmental conditions. The process-based model BIOME-BGC is widely used in simulation of carbon balance within vegetation, litter and soil of unmanaged ecosystems. For Moso bamboo forests, however, simulations with BIOME-BGC are inaccurate in terms of the growing season and the carbon allocation, due to the oversimplified representation of phenology. Our aim was to improve the applicability of BIOME-BGC for managed Moso bamboo forest ecosystem by implementing several new modules, including phenology, carbon allocation, and management. Instead of the simple phenology and carbon allocation representations in the original version, a periodic Moso bamboo phenology and carbon allocation module was implemented, which can handle the processes of Moso bamboo shooting and high growth during “on-year” and “off-year”. Four management modules (digging bamboo shoots, selective cutting, obtruncation, fertilization) were integrated in order to quantify the functioning of managed ecosystems. The improved model was calibrated and validated using eddy covariance measurement data collected at a managed Moso bamboo forest site (Anji) during 2011–2013 years. As a result of these developments and calibrations, the performance of the model was substantially improved. Regarding the measured and modeled fluxes (gross primary production, total ecosystem respiration, net ecosystem exchange), relative errors were decreased by 42.23%, 103.02% and 18.67%, respectively.

Forests synchronize their growth in contrasting Eurasian regions in response to climate warming

Forests play a key role in the carbon balance of terrestrial ecosystems. One of the main uncertainties in global change predictions lies in how the spatiotemporal dynamics of forest productivity will be affected by climate warming. Here we show an increasing influence of climate on the spatial variability of tree growth during the last 120 y, ultimately leading to unprecedented temporal coherence in ring-width records over wide geographical scales (spatial synchrony). Synchrony in growth patterns across cold-constrained (central Siberia) and drought-constrained (Spain) Eurasian conifer forests have peaked in the early 21st century at subcontinental scales (∼ 1,000 km). Such enhanced synchrony is similar to that observed in trees co-occurring within a stand. In boreal forests, the combined effects of recent warming and increasing intensity of climate extremes are enhancing synchrony through an earlier start of wood formation and a stronger impact of year-to-year fluctuations of growing-season temperatures on growth. In Mediterranean forests, the impact of warming on synchrony is related mainly to an advanced onset of growth and the strengthening of drought-induced growth limitations. Spatial patterns of enhanced synchrony represent early warning signals of climate change impacts on forest ecosystems at subcontinental scales.

大气气溶胶增加对作物的影响研究进展

PDF HTML阅读 XML下载 导出引用 引用提醒 大气气溶胶增加对作物的影响研究进展 DOI: 10.5846/stxb201409031751 作者: 作者单位: 中国科学院遗传与发育生物学研究所农业资源研究中心,中国科学院遗传与发育生物学研究所农业资源研究中心,中国科学院遗传与发育生物学研究所农业资源研究中心 作者简介: 通讯作者: 中图分类号: 基金项目: 国家科技支撑计划项目(2013BAD051302); 公益性行业科研专项(201203077) A review of the research on crop responses to the increase in aerial aerosol Author: Affiliation: Center for Agricultural Resources Ｒesearch,Institute of Genetics and Developmental Biology,Chinese Academy of Sciences,Center for Agricultural Resources Ｒesearch,Institute of Genetics and Developmental Biology,Chinese Academy of Sciences,Center for Agricultural Resources Ｒesearch,Institute of Genetics and Developmental Biology,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:大气气溶胶是指悬浮在大气中的固态和液态颗粒物总称。近年来空气污染带来了一些区域大气气溶胶浓度上升明显,一定程度上对作物生长环境带来影响。国内外关于大气气溶胶增加可能对作物产生的影响表现在:(1)大气气溶胶增加会导致直接辐射减少,而散射辐射可能会有一定程度增加;散射辐射增加有利于一些作物整个冠层光合能力的提高。(2)大气气溶胶带来辐射的改变也会影响近地面小气候环境,尤其是大气昼夜温度变化,从而影响作物干物质积累;而辐射与温度的改变同时也会影响农田蒸散和最终水分利用效率。(3)大气气溶胶形成的干沉降会停留在叶片表面,减少光合有效辐射到达叶片的量,同时对作物叶片结构和功能产生直接影响。在总结国内外研究进展基础上,提出未来关于大气气溶胶增加对作物影响需要进一步明确大气气溶胶带来的作物生长环境改变对作物碳同化、积累和消耗的影响以及直接和散射辐射比例改变如何影响作物光合和蒸腾的相互关系,通过全面系统的研究大气气溶胶对作物产量形成的影响机制,提出有针对性的田间应对技术。 Abstract:Aerial aerosol is defined as a colloid of fine solid particles or liquid droplets in the atmosphere. With the improvements in economic and social development, aerosol emissions are rapidly increasing in some Chinese regions. Consequently, haze and fog frequently occur and there are widespread concerns about the possible harmful effects of the haze on human beings. Its possible effects on agricultural production have also been studied and some results, based on related studies carried out globally, have shown that (1) Anthropogenic fossil fuel and biomass combustion have released aerosols into the atmosphere that have affected the quantity and optical properties of aerosols (known as aerosol optical depth). Changes in aerosol optical depth modify the solar radiation reaching the ground, which directly affects the carbon balance of terrestrial ecosystems. The change in crop yield due to the influence of aerosols was found to be extremely dependent on the magnitude of the reduction in direct radiation and the increase in the diffuse fraction. These particles can directly scatter and/or absorb surface solar radiation in different ways because of differences in the composition and density of air pollutants. The accepted view is that the increase in the aerosol optical depth will reduce direct radiation, and that diffuse radiation will increase to some extent. Furthermore, the increased diffuse radiation should benefit crop canopy photosynthesis and have a larger effect on gross primary production than the latent radiation. (2) The change in radiation also affects air temperature near the surface. The daytime temperature will decrease, but the nighttime temperature might increase, which may lead to a reduced diurnal temperature difference. As a result, crop production and crop water use might fall. (3) The direct effects of aerosol on crops have also been measured, along with the indirect effects of air pollution on crop growth and yield production. The deposition of dry particles on the leaf surface may block the radiation reaching the leaf surface and negatively affect leaf structure and function, which could reduce the photosynthetic capacity of crops. The above-mentioned results showed that there were possible positive and negative effects of air pollution on crop growth. However, the overall effects of the aerosol on crop production are still not clear in regions with serious air pollution problems. Therefore, it is necessary to further quantify the influence of aerosols on radiation partitioning, and their interactions with carbon processes, crop-water relations, crop leaf properties, and photosynthetic functions, to determine the magnitude of the air pollution effects on crop performance and provide possible counter-measures to mitigate the negative effects of air pollution on crop growth. 参考文献 相似文献 引证文献

Coincidences of climate extremes and anomalous vegetation responses: comparing tree ring patterns to simulated productivity

Abstract. Climate extremes can trigger exceptional responses in terrestrial ecosystems, for instance by altering growth or mortality rates. Such effects are often manifested in reductions in net primary productivity (NPP). Investigating a Europe-wide network of annual radial tree growth records confirms this pattern: we find that 28% of tree ring width (TRW) indices are below two standard deviations in years in which extremely low precipitation, high temperatures or the combination of both noticeably affect tree growth. Based on these findings, we investigate possibilities for detecting climate-driven patterns in long-term TRW data to evaluate state-of-the-art dynamic vegetation models such as the Lund-Potsdam-Jena dynamic global vegetation model for managed land (LPJmL). The major problem in this context is that LPJmL simulates NPP but not explicitly the radial tree growth, and we need to develop a generic method to allow for a comparison between simulated and observed response patterns. We propose an analysis scheme that quantifies the coincidence rate of climate extremes with some biotic responses (here TRW or simulated NPP). We find a relative reduction of 34% in simulated NPP during precipitation, temperature and combined extremes. This reduction is comparable to the TRW response patterns, but the model responds much more sensitively to drought stress. We identify 10 extreme years during the 20th century during which both model and measurements indicate high coincidence rates across Europe. However, we detect substantial regional differences in simulated and observed responses to climatic extreme events. One explanation for this discrepancy could be the tendency of tree ring data to originate from climatically stressed sites. The difference between model and observed data is amplified by the fact that dynamic vegetation models are designed to simulate mean ecosystem responses on landscape or regional scales. We find that both simulation results and measurements display carry-over effects from climate anomalies during the previous year. We conclude that radial tree growth chronologies provide a suitable basis for generic model benchmarks. The broad application of coincidence analysis in generic model benchmarks along with an increased availability of representative long-term measurements and improved process-based models will refine projections of the long-term carbon balance in terrestrial ecosystems.

Airborne Lidar-derived volume metrics for aboveground biomass estimation: A comparative assessment for conifer stands

Estimating aboveground biomass (AGB) is essential to quantify the carbon balance of terrestrial ecosystems, and becomes increasingly important under changing global climate. Volume metrics of individual trees, for example stem volume, have been proven to be strongly correlated to AGB. In this paper, we compared a range of airborne Lidar-derived volume metrics (i.e. stem volume, crown volume under convex hull, and crown volume under Canopy Height Model (CHM)) to estimate AGB. In addition, we evaluated the effect of horizontal crown overlap (which is often neglected in Lidar literature) on the accuracy of AGB estimation by using a hybrid method that combined marker-controlled watershed segmentation and point cloud segmentation algorithms. Our results show that: (1) when the horizontal crown overlap issue was not addressed, models based on point cloud segmentation outperformed models based on marker-controlled watershed segmentation; models using stem volume estimated AGB more accurately than models using crown volume under convex hull and crown volume under CHM. (2) Once the horizontal crown overlap issue was taken into consideration, the model using crown volume under CHM yielded a more accurate estimation of AGB. Our study provides a comprehensive evaluation of the use of airborne Lidar-derived volume metrics for AGB estimation and could help researchers choose the appropriate airborne Lidar-derived volume metric. Moreover, the results also indicate that horizontal crown overlap should be addressed when the airborne Lidar-derived forest crown volume is used for estimating AGB.

Soil inorganic carbon stock under different soil types and land uses on the Loess Plateau region of China

The soil carbon reservoir is the largest carbon reservoir in terrestrial ecosystems and consists of soil organic and inorganic carbon stocks. Previous studies have mainly focused on the soil organic carbon (SOC) stock, and limited information is available about the soil inorganic carbon (SIC) stock. The Chinese Loess Plateau (CLP), which is located in the arid and semi-arid region of China, is an important inorganic carbon reservoir, with a thick soil layer that is rich in calcium carbonate. However, there are few reports on the SIC stock and its spatial distribution in this region. In the current study, the SIC densities and stocks for various soil types and land use patterns were evaluated based on 495 profiles with 2470 soil samples across the CLP, which were collected from the Chinese Second National Soil Survey. The results showed that in the top 1m of soil across the CLP, the average SIC density is 17.04kg/m2, and the total SIC stock is approximately 10.20 Pg C (1 Pg=1015g). The SIC stock of the CLP accounts for approximately 18.4% of the total SIC stock throughout China. The average values of the SIC stock in the 0–20, 20–50 and 50–100cm depths of the CLP are 2.39, 2.92 and 4.89 Pg, respectively. Under different land use patterns, the order of the average SIC density is farmland≈grassland>forest in all soil layers. For the various soil types, the SIC density in the 0–100cm layer is the highest in alkaline soil and lowest in subalpine meadow soil, whereas the SIC stock is highest in loessial soil, eolian sandy soil and sierozem, and the lowest in subalpine meadow soil. These differences are largely a result of the area occupied by each soil type and the climate conditions. The results of this study provide basic information about carbon reservoir in China and contribute to our understanding of the SIC stock on the CLP as it relates to the carbon balance of terrestrial ecosystems.

Quantifying the role of fire in the Earth system – Part 2: Impact on the net carbon balance of global terrestrial ecosystems for the 20th century

Abstract. Fire is the primary form of terrestrial ecosystem disturbance on a global scale. It affects the net carbon balance of terrestrial ecosystems by emitting carbon directly and immediately into the atmosphere from biomass burning (the fire direct effect), and by changing net ecosystem productivity and land-use carbon loss in post-fire regions due to biomass burning and fire-induced vegetation mortality (the fire indirect effect). Here, we provide the first quantitative assessment of the impact of fire on the net carbon balance of global terrestrial ecosystems during the 20th century, and investigate the roles of fire's direct and indirect effects. This is done by quantifying the difference between the 20th century fire-on and fire-off simulations with the NCAR Community Land Model CLM4.5 (prescribed vegetation cover and uncoupled from the atmospheric model) as a model platform. Results show that fire decreases the net carbon gain of global terrestrial ecosystems by 1.0 Pg C yr−1 averaged across the 20th century, as a result of the fire direct effect (1.9 Pg C yr−1) partly offset by the indirect effect (−0.9 Pg C yr−1). Post-fire regions generally experience decreased carbon gains, which is significant over tropical savannas and some North American and East Asian forests. This decrease is due to the direct effect usually exceeding the indirect effect, while they have similar spatial patterns and opposite sign. The effect of fire on the net carbon balance significantly declines until ∼1970 with a trend of 8 Tg C yr−1 due to an increasing indirect effect, and increases subsequently with a trend of 18 Tg C yr−1 due to an increasing direct effect. These results help constrain the global-scale dynamics of fire and the terrestrial carbon cycle.

施肥方式对紫色土土壤异养呼吸的影响

Recent studies have shown that soil respiration is the critical importance in determining the carbon balance of terrestrial ecosystems. Respiration from soils is comprised of both the heterotrophic respiration of microorganisms( soil bacteria,fungi,and fauna) and autotrophic respiration from roots and mycorrhizae. Precise assessment of these components is important for calculating the carbon budgets of vegetation and the turnover rate of soil organic matter,as well as for understanding sources and sinks of carbon in terrestrial ecosystems in the face of global climate change. Although soil heterotrophic respirations have received considerable attention in recent decades,much less is known about the effects of various natural or artificial factors such as temperature,precipitation or fertilization etc. on it. The field study was conducted at a sloping cropland in Yanting Agro-ecological Station of Purple Soil,Chinese Academy of Science under Chinese Ecosystem Research Network( CERN),situated at N31°16°,E105°28',with the altitude of 400 to 600 meters in the middle of Sichuan Basin,where a set of long-term research plots is located. Three plots were randomly assigned to oneof the following treatments: conventional chemical fertilizer( NPK),organic manure( pig slurry,OM) and crop residue with chemical fertilizer( RSDNPK). Total nitrogen for each fertilization treatment was applied at the same rate with 130 and150 kgN /hm2 for wheat and maize seasons,respectively. The results showed that soil heterotrophic respiration exhibited pronounced seasonal variations that clearly reflected those of soil temperature,with minimum values in winter and maximum values in summer. There was a pulse of soil heterotrophic respiration induced by fertilization at the 5th day after fertilization. The peak rate for OM treatment was 2356. 8 mgCO2m-2h-1and it was significantly higher than that for both RSDNPK and NPK treatments( P0. 01). Meanwhile,the respiration rate and the annual cumulative CO2 emission in OM and RSDNPK treatments were higher than those in NPK treatment. During wheat growing season,average respiration rate for NPK,OM and RSDNPK treatments were 212. 9,285. 8 and 305. 8 mgCO2m-2h-1,respectively,which were all lower than that in maize growing season. The cumulative soil CO2 emissions from NPK,OM and RSDNPK were 255. 1,342. 3and 369. 5 gC /m2 for wheat season,and 344. 7,542. 8 and 376. 9 gC /m2 for maize season,while 599. 8,885. 1 and 746. 4gCm-2for the whole year,respectively. The results implied that lower C /N ratio organic material was the primary driving force for increasing soil heterotrophic rate and cumulative soil CO2 emissions. The values of temperature sensitivity( Q10)for soil heterotrophic respiration in wheat season and maize season were also measured. The results showed that Q10 values in wheat season always higher than that in maize season at all plots. During the whole experiment time,the magnitudes of Q10 both followed the order of OM NPK RSDNPK,which was clearly reflected that Q10 was sensitive to lower C /N organic materials. Q10 values obtained from soil temperature at soil surface( 0 cm) and soil 5 cm depth in OM and RSDNPK were2. 64,2. 77 and 1. 88,1. 99,respectively. It indicated that the Q10 values for soil heterotrophic respiration rates were higher at lower temperatures and lower at higher temperature.

Spatio-temporal variation of vegetation carbon storage and density in karst areas of Northwest Guangxi based on remote sensing images

本研究基于1990年、2000年和2005年遥感影像数据, 结合高程、气象与样地调查等数据, 运用地理信息系统技术, 对桂西北喀斯特区植被碳储量及密度进行了分析。研究结果表明: 从1990年到2005年, 研究区域植被碳储量与密度呈增加趋势, 1990年、2000年和2005年植被碳储量分别为1.03×10⁸ t、1.41×10⁸ t和1.63×10⁸ t, 植被碳密度分别为14.82 t·hm^-2、20.38 t·hm^-2和23.49 t·hm^-2, 基本与四川省(18.47 t·hm^-2)、江西省(25.38 t·hm^-2)植被碳密度值一致; 在空间分布上, 区域植被储量与碳密度大致呈现西高东低、中低山(海拔>500 m)高而峰丛洼地(海拔<500 m)低的分布格局, 1990年西部大部分县市的植被碳密度为15~22 t·hm^-2, 而中东部大部分县市的植被碳密度为8~15 t·hm^-2; 而时间上的变化在空间上表现为, 植被碳储量与密度不同程度地表现为低值区的东部增加, 高值区的西部减少或轻微增加, 典型喀斯特区植被碳密度增加明显(1990年和2005年植被碳储量比例分别为45.54%和51.99%)。研究结果表明, 峰丛洼地植被碳储量与密度显著增加, 生态环境移民、退耕还林等石漠化治理措施效果显著, 有利于增强区域植被碳汇。

Dynamics of CO2 fluxes and environmental responses in the rain-fed winter wheat ecosystem of the Loess Plateau, China

Chinese Loess Plateau plays an important role in carbon balance of terrestrial ecosystems. Continuous measurement of CO2 fluxes in cropland ecosystem is of great significance to accurately evaluate the carbon sequestration potential and to better explain the carbon cycle process in this region. By using the eddy covariance system we conducted a long-term (from Sep 2009 to Jun 2010) CO2 fluxes measurement in the rain-fed winter wheat field of the Chinese Loess Plateau and elaborated the responses of CO2 fluxes to environmental factors. The results show that the winter wheat ecosystem has distinct seasonal dynamics of CO2 fluxes. The total net ecosystem CO2 exchange (NEE) of −218.9±11.5gCm−2 in the growing season, however, after considering the harvested grain, the agro-ecosystem turned into a weak carbon sink (−36.2gCm−2). On the other hand, the responses of CO2 fluxes to environmental factors depended on different growth stages of winter wheat and different ranges of environmental variables, suggesting that the variations in CO2 exchange were sensitive to the changes in controlling factors. Particularly, we found the pulse response of ecosystem respiration (Reco) to a large rainfall event, and the strong fluctuations of CO2 fluxes usually appeared after effective rainfall events (daily precipitation>5mm) during middle growing season. Such phenomenon also occurred in the case of the drastic changes in air temperature and within 5days after field management (e.g. tillage and plough).