凋落物输入对半干旱区沙地灌丛土壤碳氮积累和转化的影响

全球变化通过影响陆地生态系统初级生产力而改变土壤凋落物输入。凋落物输入直接影响陆地生态系统土壤碳氮储量和循环。所以研究土壤碳氮储量和循环对凋落物输入的响应对于预测全球变化对陆地生态系统碳氮循环的影响具有重要作用。灌丛是中国分布较广的植被类型之一，但是目前凋落物输入对灌丛土壤碳氮积累和循环影响的研究相对薄弱。本项目以我国半干旱区科尔沁沙地优势灌丛为研究对象，通过人为去除和添加灌丛地面凋落物、灌丛凋落物交互移置等方法，改变灌丛地面凋落物的输入量和凋落物组成，动态观测灌丛下土壤有机碳含量、全氮含量、可溶性碳氮含量、活性碳氮含量、微生物生物量碳氮含量、土壤呼吸以及氮矿化作用等要素的变化，分析灌丛土壤碳氮积累和转化与凋落物输入之间、以及灌丛土壤碳氮积累动态与碳氮转化过程之间的相互关系，揭示改变灌丛地面凋落物输入量和组成影响灌丛土壤碳氮收支平衡的内在机理，为准确估算灌丛生态系统碳收支平衡提供科学依据。

Global change will affect the primary productivity ofterrestrial ecosystem, and thereby eventually affect litter inputs into the soil.Changes in litter input will eventually affect storage and cycles of carbon and nitrogen in soils. Therefore, understanding the effects of litter input on soil carbon and nitrogen storage and cycles is very important to anticipate the responses of soil carbon and nitrogen storage and cycles to global change, and serve as key content to evaluate the balance of soil carbon and nitrogen budget. Shrubis one of the largest vegetation types in china. However, studies related to the effect of litter input on soil carbon and nitrogen storage and cycles in shrub ecosystems is relatively limited at home and abroad. In this project, we will artificially alter the ground litter quantity and litter composition in shrub ecosystems by the way of litter removal, litter addition, and reciprocal litter transplant experiments in Kerqin Sand Lands, northern China.We will dynamically investigate soil organic carbon, total nitrogen, dissolved organic carbon and nitrogen, active carbon and nitrogen, microorganism biomass carbon and nitrogen, soil respiration, and soil nitrogen mineralization under shrub canopy with litter input manipulations. Thereafter, the correlations will be analyzed between litter input manipulation and soil carbon and nitrogen accumulation and transformation. Also，relations between accumulation and transformation of soil carbon and nitrogen will be detected to reveal the mechanism of budget balances in soil carbon and nitrogen under shrub canopy with litter inputs manipulations.The purpose of this study is to supply some scientific rationales for evaluating budget balances of carbon and nitrogen in shrub ecosystems.