Atmospheric nitrogen （N） deposition caused by anthropogenic activities may alter litter decomposition and species composition, and then affect N cycling and carbon （C） sequestration in an ecosystem. Using the litt...
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Atmospheric nitrogen （N） deposition caused by anthropogenic activities may alter litter decomposition and species composition, and then affect N cycling and carbon （C） sequestration in an ecosystem. Using the litterbag method, we studied the effects of N addition （CK： no N addition; low-N： 1 g N m-2 y-l; high-N： 2 g N m-2 y-l） on changes in mass remaining of shoot litter decomposition of three grasses （Stipa baicalensis, Carex pediformis and Leymus chinensis） over 28 months in the Hulun Buir meadow steppe of Inner Mongolia. The results showed that the addition of high and low N had no significant effect on the decomposition of single-species litter, but low N addition slightly inhibited the decomposition of litter mixtures. In addition, litter decomposition was strongly species dependent. Our results suggest that species type is likely the main determinant of litter decomposition, and low N deposition in natural ecosystems does not influence single-species litter decomposition.
土壤氮矿化(Nitrogen mineralization)是土壤氮循环的重要环节,对土壤氮素供应以及植物生产力的维持具有十分重要的意义.沿中国东北草地样带(Northeastern China Transect,NECT)分别在典型草地、过渡草地及荒漠草地设置了3个实验样地,...
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土壤氮矿化(Nitrogen mineralization)是土壤氮循环的重要环节,对土壤氮素供应以及植物生产力的维持具有十分重要的意义.沿中国东北草地样带(Northeastern China Transect,NECT)分别在典型草地、过渡草地及荒漠草地设置了3个实验样地,利用不同温度(5、10、15、20℃和25℃)和不同水分(30％、60％和90％土壤饱和含水量,Saturated soil moisture,SSM)的室内培养途径,探讨了不同类型草地的土壤氮矿化速率、土壤氮矿化的温度敏感性(Q10)及其主要影响因素.实验结果表明:从典型草地至荒漠草地,土壤全碳、全氮、全磷、微生物生物量碳氮含量均表现为逐渐下降的趋势;类似地,土壤净氮矿化速率、硝化速率也逐渐降低.在20℃和60％ SSM时,土壤净氮矿化速率表现为典型草地(0.715 mg N kg-1 d-1)＞过渡草地(0.507 mg N kg-1d-1)＞荒漠草地(0.134 mg N kg-1 d-1);相反,温度敏感性却逐渐升高,温度敏感性与基质质量指数呈负相关.草地类型和水分对于土壤净氮矿化速率、硝化速率具有显著影响,且二者间具有显著的交互效应.包含温度和水分的双因素模型可很好地拟合土壤氮矿化速率的变化趋势(P ＜0.0001),二者可共同解释土壤硝化速率92％-96％的变异.土壤氮矿化沿着草地演替呈现出很好的空间格局、并与温度和水分具有密切关系,为解释内蒙古草地空间分布格局提供了理论基础.
Afforestation projects were applied in the Poyang Lake Basin of China at the beginning of 1980s. The large-scale plantation may dramatically influence the changes in carbon storage of forests in this basin. Therefore,...
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Afforestation projects were applied in the Poyang Lake Basin of China at the beginning of 1980s. The large-scale plantation may dramatically influence the changes in carbon storage of forests in this basin. Therefore, climate-induced variations in the carbon balance of the Poyang Lake Basin＇s forests may play an important role in the carbon cycle of China. However, we have little understanding of their long-term behavior, especially the future trend of carbon sink/source patterns under climate change and rising atmospheric CQ. The annual carbon budget of the Poyang Lake Basin＇s forests during 1981-2050 was estimated by using the Integrated Terrestrial Ecosystem Carbon-budget model （InTEC） coupled with projected climate change simulated by Regional Integrated Environmental Model System （RIEMS 2.0）. During 1981-2000, the rapid increment of annual NPP in this basin was possible due to large plantation. Soil organic carbon storage （0-30cm） of forests generally decreased by 1.0% per year at the beginning of plantation. Moreover, forests in this basin converted from carbon source in 1980s to carbon sink in 1990s. By 2040-2050, total carbon stocks of forest ecosystems will increase by 0.78Pg C, compared to recent years （2001-2010）. Under future climate and CQ concentration in AIB scenario, NEP of forests in Poyang Lake Basin lean to keep relative stable （20-30Tg C y-i） because of old forests except for some years induced by extreme droughts. Our results also showed that prediction of NEP of forests in Poyang Lake Basin was controlled by water limitation; in contrast, temperature was the main factor on inter- annual variability of NPP.
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