土壤呼吸(R s ) 是在陆上的生态系统加重我们碳周期的理解的关键过程之一。在有在最高、最低的估计之间的 70 Pg C a1 的差别的以前的全球 R s 估计的大无常遗体。因此，现在的学习试图估计全球年度 R s 并且用包括了气候的因素(温度和降水) 和表层土(020 厘米) 的一个半机械学的、以经验为主地基于的模型在全球年度 R s 调查 interannual 和空间可变性器官的碳存储。从 147 个测量地点的年度 R s 的大约 657 出版研究在这元分析被包括。气候，表面空气温度，和土壤性质上的从 1970 ～ 2008 的全球数据集合是镇定的。蒙特卡罗方法被用来宣传模拟错误到全球 R s。结果显示吝啬的年度全球 R s 是 94.4 Pg C a1，增加在粗略地从 1970 ～ 2008 的 0.04 Pg C a1 (0.04% a1 ) 。R s 率增加了从更冷，更干燥并且少些玷污充满碳的区域到更温暖、更潮湿、更充满碳的区域。最高的 R s 率出现在热带森林里，当最低的在极、荒芜的区域时。年度 R s 与全球温度异例直接相关，建议在温度的 interannual 可变性为在预言的全球 R s 的 interannual 变化负责。全球 R s 从高纬度的地区增加了到低纬度的地区。进一步的研究被建议探索在土壤呼吸和植被人物之间的关系。
Improving management of soil organic carbon(SOC)has been considered as a substantial mitigation strategy to climate change.Management such as stubble retention(SR),conservation tillage(ZT),and fertilization are recommended for both promoting production and accumulating SOC.However,whether such management practices can cause net increase in SOC or just a slow-down of SOC decline largely depends on the current status of SOC for a given region.This paper synthesized the available SOC data in the croplands of China,and analysed the change of SOC in the top 20 cm soil as a result of management change.The results showed that,on average,SOC increased by 18.3%through SR,by 9.1%through ZT,and by 12.4%,36.9%and 41.5%through application of inorganic(IF),organic(OF)and combined inorganic and organic fertilizers(IOF),respectively,compared to those under stubble removal,conventional tillage and no fertilization.Under SR,ZT,IF,OF and IOF,SOC increased by 16.0%,10.2%,8.2%,32.2%and41.3%,respectively,at the end of the trials compared with the initial values at the start of the trials.Our analysis also showed that in Northeast and Northwest China,SOC in agricultural soils is still decreasing due to cultivation.In North and South China,however,SOC appears to have reached a new equilibrium of low SOC state after a long cultivation history,and soils have greater potential to sequester C.Our analysis highlights the need of taking account of the baseline status to assess the net soil C balance over time and space.
Soil respiration is an important process in terrestrial carbon cycle.Concerning terrestrial ecosystems in China, quantifying the spatiotemporal pattern of soil respiration at the regional scale is critical in providing a theoretical basis for evaluating carbon budget.In this study, we used an empirically based, semi-mechanistic model including climate and soil properties to estimate annual soil respiration from terrestrial ecosystems in China from 1970 to 2009.We further analyzed the relationship between interannual variability in soil respiration and climatic factors (air temperature and precipitation).Results indicated that the distribution of annual soil respiration showed clear spatial patterns.The highest and lowest annual soil respiration rates appeared in southeastern China and northwestern China, respectively, which was in accordance with the spatial patterns of mean annual air temperature and annual precipitation.Although the mean annual air temperature in northwestern China was higher than that in some regions of northeastern china, a greater topsoil organic carbon storage in northeastern China might result in the higher annual soil respiration in this region.By contrast, lower temperature, less precipitation and smaller topsoil organic carbon pool incurred the lowest annual soil respiration in northwestern China.Annual soil respiration from terrestrial ecosystems in China varied from 4.58 to 5.19 PgCa-1 between 1970 and 2009.During this time period, on average, annual soil respiration was estimated to be 4.83 PgCa-1 .Annual soil respiration in China accounted for 4.93%-6.01% of the global annual soil CO2 emission.The interannual variability in soil respiration depended on the interannual variability in precipitation and mean air temperature.In order to reduce the uncertainty in estimating annual soil respiration at regional scale, more in situ measurements of soil respiration and relevant factors (e.g.climate, soil and vegetation) should be made simultaneously and historical soil property data sets sho
Aims Although many studies have reported net gains of soil organic carbon(SOC)after afforestation on croplands,this is uncertain for Chinese paddy rice croplands.Here,we aimed to evaluate the effects of affores-tation of paddy rice croplands on SOC sequestration and soil respiration(R).Such knowledge would improve our understanding of the efctive-ness of various land use options on greenhouse gas mitigation in China.Methods The investigation was conducted on the Chongming Island,north subtropical China.Field sites were reclaimed from coastal salt marshes in the 1960s,and soils were homogeneous with simple land use:histories.SOC stocks and R,levels were monitored over one year in a paddy rice cropland,an evergreen and a deciduous broad-leaved plantation established on previous paddy fields and a reference fal-low land site never cultivated.Laboratory incubation of soil under fast-changing temperatures was used to compare the temperature sensitivity(Q10)of SOC decomposition across land uses.Important Findings After 15-20 years of afforestation on paddy fields,SOC concentra-tion only slightly increased at the depth of 0--5 cm but decreased in deeper layers,which resulted in a net loss of SOC stock in the top 40cm.Seasonal increase of sOC was observed during the rice-growing period in croplands but not in afforested soils,suggest-ing a stronger SOC sequestration by paddy rice cropping.However,SOC sequestered under cropping was more labile,as indicated by its higher contents of dissolved organic carbon and microbial bio-mass.Also,paddy soils had higher annual R,than afforested soils;R,abruptly increased after paddy fields were drained and plowed and remained distinctively high throughout the dry farming period.Laboratory incubation revealed that paddy soils had a much higher Q10 of SOC decomposition than afforested soils.Given that tem-perature was the primary controller of R,in this region,it was con-cluded that despite the stronger SOC sequestration by paddy rice cropping,its SOC was less stable than in afforested s
Jun CuiRongjuan ZhangNaishun BuHuabin ZhangBoping TangZhaolei LiLifeng JiangJiakuan ChenChangming Fang
