氮添加对内蒙古温带草原优势物种凋落物分解的影响

Effects of nitrogen addition on litter decomposition of two dominant species in temperate steppe,Inner Mongolia

利用原位分解袋法,研究了不同氮沉降水平对内蒙古温带草原优势物种克氏针茅(Stipa krylovii)和冷蒿(Artemisia frigida)凋落物分解过程的影响.实验共设5个氮添加梯度,分别是N0 (0g·m^(-2)·a^(-1))、N2 (2g·m^(-2)·a^(-1))、N5(5g·m^(-2)·a^(-1))、N10(10g·m^(-2)·a^(-1))和N25(25g·m^(-2)·a^(-1)).结果表明,分解1年后,克氏针茅凋落物的质量残留率在氮添加处理间差异显著,冷蒿凋落物则无显著差异,物种和氮添加处理均会对凋落物分解速度产生影响.凋落物最终残留率与其初始性质呈显著相关关系.不同氮添加水平下凋落物分解过程中碳元素质量分数变化趋势一致,而氮元素质量分数的变化在物种和氮添加水平间差异明显.不同氮沉降水平会改变凋落物的分解速度和养分释放模式,且不同物种的凋落物分解对氮添加的响应并不一致.

Effect of nitrogen deposition on litter decomposition of two dominant species（Stipa krylovii and Artemisia frigida）in Inner Mongolia steppe was examined in an attempt to reveal how litter decomposition responds to nitrogen deposition rates and species.The experimental plots contained five N addition treatments：N0（0 g·m^-2·a^-1）,N2（2 g·m^-2·a^-1）,N5（5 g·m^-2·a^-1）,N10（10 g·m^-2·a^-1）and N25（25 g·m^-2·a^-1）.After one year of decomposition,the remaining litter mass of S.krylovii differed significantly among varied nitrogen additions,but A.frigida showed no difference.Both species and N addition rates therefore affected litter decomposition rate.The remaining mass correlated with initial nutrient content of litter.Litter carbon content of both species showed identical tendency across N addition treatments.Significant differences of changes in litter nitrogen content were found between species and N addition treatments.These data suggest that rates of nitrogen addition had effect on litter decomposition rates and nutrient release pattern,the two dominant species had varied response to nitrogen addition treatments.