物种和低剂量氮添加对呼伦贝尔草甸草原三种主要优势种凋落物分解的影响

人类活动导致的大气氮沉降也许已经改变了凋落物分解速率和物种组成，从而影响生态系统氮循环和碳储量。本文在呼伦贝尔草甸草原，采用凋落物袋的方法，结合低剂量氮添加处理实验（对照：无氮添加；低氮处理：1gNm^-2y^-1；高氮处理：2gNm^-2Y^-1），研究了在28个月的分解实验期间，氮沉降对三种优势种地上部凋落物分解剩余重量变化的影响。结果表明：在我们的研究中，无论高氮还是低氮添加均对单物种凋落物分解没有影响，但是低氮添加轻微地抑制了混合凋落物分解。凋落物分解明显地受到物种类型的影响。我们的结果说明，初始凋落物质量可能是凋落物分解的主要决定因素，自然生态系统中低剂量的氮沉降并不会影响单物种凋落物的分解。

Effects of Species and Low Dose Nitrogen Addition on Litter Decomposition of Three Dominant Grasses in Hulun Buir Meadow Steppe

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.