基于374个高寒草原和温带草原土壤样品的测试结果,运用多元逐步回归分析模型定量评估了土壤环境因子对土壤有机碳(SOC)含量的影响。结果表明:高寒草原土壤有机碳含量(20.18 kg C/m2)高于温带草原(9.23 kg C/m2)。土壤理化生物学因子对高寒草原和温带草原SOC含量(10 cm)变化的贡献分别是87.84%和75.00%。其中,土壤总氮含量和根系对高寒草原SOC含量变化的贡献均大于对温带草原SOC含量变化的相应贡献。土壤水分是温带草原SOC含量变化的主要限制性因素,其对SOC含量变化的贡献达33.27%。高寒草原土壤C/N比显著高于温带草原土壤的相应值,揭示了青藏高原高寒草原较高的SOC含量是由于较低的土壤微生物活性所导致。
The fluvial geochemistry of the mainstream and tributaries of the Zengjiang River was investigated,and the mass balance approach and deduction methods were used to estimate the uptake of atmospheric CO2 through rock chemical weathering.The results showed that the chemical runoff mainly consisted of HCO3-,Ca2+,Na+,and dissolved Si,and that silicate mineral weathering was significant,but carbonate mineral weathering was a minor source of dissolved loads in the Zengjiang River basin because of the low amount of interlayered carbonate rock strata in the catchment.The ion composition indicated that atmospheric CO2 was the primary erosive agent for rock chemical weathering in the Zengjiang River basin.The CO2 consumption fluxes caused by rock chemical weathering were(3.50-3.81) × 105 mol km-2 a-1,which is just lower than that in tropical and subtropical basalt and carbonate regions,and is much higher than that in temperate and cold-temperate regions,indicating that surficial chemical weathering processes in the humid and hot monsoon current influencing the low-middle latitude zone of the Northern Hemisphere constitutes a significant carbon sink in the global biogeochemical cycle.
TAO ZhenGAO QuanZhouWANG ZhenGangZHANG ShengHuaXIE ChenJiLIN PeiSongRUAN XiaoBingLI ShuHongMAO HaiRuo
A whole year analysis of riverine dissolved organic carbon (DOC) concentrations in the Xijiang River (XJR), South China, showed that the mean riverine DOC concentration (1.24 mg L-1) in the XJR was notably lower than the averaged value (5.75 mg L-1) of the global riverine DOC concentration in several major rivers. There is an inconspicuous monthly fluctuation of the DOC signal in the XJR, but on a semi-yearly time scale, however, the riverine DOC concentration had significant difference between hydrological seasons. The DOC level during the flood season (1.18 mg L-1) was less than that during the non-flood season (1.40 mg L-1). Owing to the concomitance of the flushing and dilution effects of the runoff during the high-water period, the variation of riverine DOC concentration with discharge in the XJR differed from that reported in many other major rivers. The DOC export flux above the city of Wuzhou was about 0.62× 106 g C km-2 yr-1. The DOC transported during the "056" Massive Flood period comprised 30.35% of the annual total, while the discharge accounted for 36.32% of the total annual flow. The characteristics in riverine DOC concentration in the XJR were attributed to the combined effect of the geomorphologic, monsoon climatic and hydrological processes as well as land-use within the drainage basin.
TAO ZhenGAO QuanzhouGUO WenpingWANG ZhengangZHANG YonglingXIE ChenjiHUANG XiakunZHONG Hongwei
