Wetland soils contain some of the highest stores of soil carbon in the biosphere. However, there is little understanding of the quantity and distribution of carbon stored in our remaining wetlands or of the potential effects of human disturbance on these stocks. Here we use field data from the 2011 National Wetland Condition Assessment to provide unbiased estimates of soil carbon stocks for wetlands at regional and national scales. We find that wetlands in the conterminous United States store a total of 11.52 PgC, much of which is within soils deeper than 30 cm. Freshwater inland wetlands, in part due to their substantial areal extent, hold nearly ten-fold more carbon than tidal saltwater sites-indicating their importance in regional carbon storage. Our data suggest a possible relationship between carbon stocks and anthropogenic disturbance. These data highlight the need to protect wetlands to mitigate the risk of avoidable contributions to climate change.

定量分析了青藏高原各类草地0～0.65m深度范围内有机碳储量,结果表明:青藏高原总面积为1.6027×10hm²的草地有机碳量达到335.1973×10⁸tC,其中以高原草甸土和高原草原土有机碳积累量为主,两者之和达到232.36×10⁸tC,占全国土壤有机碳量的23.44%,是全球土壤碳库的2.4%.在有机碳储量分析的基础上,按土壤碳释放的两种主要途径:土壤呼吸作用和土地利用方式变化与草地退化,对草地土壤碳排放进行了估算,揭示出青藏高原草地土壤通过呼吸每年排放的CO₂达到11.7×10⁸tC·a^-1,约占中国土壤呼吸总量的2.3%,明显高于全国乃至全球平均值;近30a来,青藏高原草地土壤由于土地利用变化和草地退化所释放的CO₂估计约有30.23×10⁸tC.保护青藏高原草地对于全球变化意义重大.定量分析了青藏高原各类草地0～0.65m深度范围内有机碳储量,结果表明:青藏高原总面积为1.6027×10hm²的草地有机碳量达到335.1973×10⁸tC,其中以高原草甸土和高原草原土有机碳积累量为主,两者之和达到232.36×10⁸tC,占全国土壤有机碳量的23.44%,是全球土壤碳库的2.4%.在有机碳储量分析的基础上,按土壤碳释放的两种主要途径:土壤呼吸作用和土地利用方式变化与草地退化,对草地土壤碳排放进行了估算,揭示出青藏高原草地土壤通过呼吸每年排放的CO₂达到11.7×10⁸tC·a^-1,约占中国土壤呼吸总量的2.3%,明显高于全国乃至全球平均值;近30a来,青藏高原草地土壤由于土地利用变化和草地退化所释放的CO₂估计约有30.23×10⁸tC.保护青藏高原草地对于全球变化意义重大.

本研究以黄河源区玛沁县大武滩不同退化高寒湿地为研究对象，分层采集冻融丘和丘间土层样品，分析土壤有机碳组分的变化及其与土壤因子的关系。结果表明：冻融丘和丘间各层轻组分有机碳、重组分有机碳、可溶性有机碳、微生物碳含量随着退化程度的加剧下降，且在未退化与轻度退化、重度退化样地冻融丘0~10 cm土层间差异显著（PP<0.05），对高寒湿地退化的响应敏感；土壤含水量与有机碳、轻组分有机碳、重组分有机碳、可溶性有机碳和微生物碳含量呈正相关关系。综上所述，高寒湿地退化导致有机碳组分减少，重组分有机碳含量和占比可作为反映土壤有机碳库变化的关键指标，微生物碳含量和占比可作为反映高寒湿地退化的关键指标，均可为高寒湿地生态系统碳库和恢复机理的研究提供数据支撑。

Different layers of soil were taken from frozen-thawing mounds as well as among them in alpine wetland with different degrees of degradation in Maqin Dawutan,the source of Yellow River. The soil organic carbon component and its relationship with soil factors were determined. Results in this study showed that the organic carbon component (light fraction organic carbon,heavy fraction organic carbon,dissolved organic carbon,microbial biomass carbon) of frozen-thawing mounds as well as among mounds decreased with the aggravation of degradation degree,and was significantly different (<i>P<</i>0.05) in 0~10 cm soil layer between undegraded,mildly degraded and severely degraded sample plots. The soil organic carbon components of frozen-thawing mounds were more sensitive than that among mounds. The content of heavy soil organic carbon accounted for more than 94.00% of the total organic carbon,which was the most important component of organic carbon. With the aggravation of degradation degree,the proportion of microbial biomass carbon in frozen-thawing mounds as well as among mounds decreased significantly (<i>P</i><0.05),and the proportion of soil microbial biomass carbon was sensitive to the degradation of alpine wetland. Soil water content positively correlated with soil organic carbon,light fraction organic carbon,heavy fraction organic carbon,dissolved organic carbon and microbial biomass carbon. In conclusion,the degradation of alpine wetlands leads to a decrease in organic carbon components. The content and proportion of heavy fraction organic carbon can be used as key indicators to reflect changes of soil organic carbon pools,and the content and proportion of microbial biomass carbon can be used as key indicators to reflect the degradation of alpine wetlands. This can provide data support for research on the carbon storage and restoration mechanism of alpine wetland ecosystem.

Recent climatic changes have enhanced plant growth in northern mid-latitudes and high latitudes. However, a comprehensive analysis of the impact of global climatic changes on vegetation productivity has not before been expressed in the context of variable limiting factors to plant growth. We present a global investigation of vegetation responses to climatic changes by analyzing 18 years (1982 to 1999) of both climatic data and satellite observations of vegetation activity. Our results indicate that global changes in climate have eased several critical climatic constraints to plant growth, such that net primary production increased 6% (3.4 petagrams of carbon over 18 years) globally. The largest increase was in tropical ecosystems. Amazon rain forests accounted for 42% of the global increase in net primary production, owing mainly to decreased cloud cover and the resulting increase in solar radiation.

Soil is the largest organic carbon (C) pool of terrestrial ecosystems, and C loss from soil accounts for a large proportion of land-atmosphere C exchange. Therefore, a small change in soil organic C (SOC) can affect atmospheric carbon dioxide (CO) concentration and climate change. In the past decades, a wide variety of studies have been conducted to quantify global SOC stocks and soil C exchange with the atmosphere through site measurements, inventories, and empirical/process-based modeling. However, these estimates are highly uncertain, and identifying major driving forces controlling soil C dynamics remains a key research challenge. This study has compiled century-long (1901-2010) estimates of SOC storage and heterotrophic respiration (Rh) from 10 terrestrial biosphere models (TBMs) in the Multi-scale Synthesis and Terrestrial Model Intercomparison Project and two observation-based data sets. The 10 TBM ensemble shows that global SOC estimate ranges from 425 to 2111 Pg C (1 Pg = 10 g) with a median value of 1158 Pg C in 2010. The models estimate a broad range of Rh from 35 to 69 Pg C yr with a median value of 51 Pg C yr during 2001-2010. The largest uncertainty in SOC stocks exists in the 40-65°N latitude whereas the largest cross-model divergence in Rh are in the tropics. The modeled SOC change during 1901-2010 ranges from -70 Pg C to 86 Pg C, but in some models the SOC change has a different sign from the change of total C stock, implying very different contribution of vegetation and soil pools in determining the terrestrial C budget among models. The model ensemble-estimated mean residence time of SOC shows a reduction of 3.4 years over the past century, which accelerate C cycling through the land biosphere. All the models agreed that climate and land use changes decreased SOC stocks, while elevated atmospheric CO and nitrogen deposition over intact ecosystems increased SOC stocks-even though the responses varied significantly among models. Model representations of temperature and moisture sensitivity, nutrient limitation, and land use partially explain the divergent estimates of global SOC stocks and soil C fluxes in this study. In addition, a major source of systematic error in model estimations relates to nonmodeled SOC storage in wetlands and peatlands, as well as to old C storage in deep soil layers.

Changes of environmental conditions can affect carbon sink function of wetlands. Understanding the effects of environmental conditions on soil organic carbon and its components in wetlands can provide scientific guidance for soil carbon regulation in wetlands. Here, we investigated the effects of water levels (high and low water level) and vegetation types (<em>Triarrhena lutarioriparia</em>&nbsp;and <em>Polygonum hydropiper</em>) on soil organic carbon and its components in Poyang Lake wetland. We analyzed the relationships between soil physicochemical properties and soil organic carbon components. Results showed that heavy fraction organic carbon was the main component of soil organic carbon, accounting for more than 70% of the total. Water level had significantly stronger effects on soil organic carbon components than the vegetation type. Soil organic carbon, heavy fraction organic carbon, particulate organic, soluble organic carbon and microbial biomass carbon of <em>P. hydropiper</em>&nbsp;community in high water level were 109.2%, 115.5%, 175.8%, 239.4%, and 61.7% higher than those in low water level, respectively. Soil pH was significantly negatively correlated with soil total carbon, heavy fraction organic carbon, and particulate organic carbon. Soil water content and total nitrogen content were significantly positively correlated with organic carbon components. Therefore, increasing water level is beneficial to soil carbon accumulation in wetlands.<br><div> <br></div>

There are several publications related to the soil organic carbon (SOC) on the Qinghai-Tibetan Plateau (QTP). However, most of these reports were from different parts of the plateau with various sampling depth. Here, we present the results from a systematic sampling and analysis of 200 soil pits. Most of the pits were deeper than 2 m from an east-west transect across the plateau. The SOC and total nitrogen (TN) pools of the 148 x 10(4) km(2), the area of the permafrost zone, for the upper 2 m soils calculated from the vegetation map were estimated to be 17.07 Pg (interquartile range: 11.34-25.33 Pg) and 1.72 Pg (interquartile range: 1.08-2.06 Pg), respectively. We also predicted the distribution of land cover types in 2050 and 2070 using decision tree rules and climate scenarios, and then predicted SOC and TN pools of this region. The results suggested that the SOC and TN pools will decrease in the future. The results not only contribute to the carbon and nitrogen storage and stocks in the permafrost regions as a whole but most importantly, to our knowledge of the possible changes of C and N storage on the QTP in the future.