中文摘要：

深入认识植物功能性状的生态学含义，对于阐明不同自然与人为干扰环境下的群落构建途径，进一步揭示生态系统服务维持机制具有重要的理论意义。该文以内蒙古锡林河流域羊草仨eymuschinensis）草原不同退化演替阶段的群落为研究对象，分析了土壤养分与植物功能性状的变化特征及两者之间的关系。结果表明：（1）退化导致土壤养分含量逐渐减少，全氮和全磷在未退化的羊草＋杂类草群落与严重退化的羊草＋冷蒿翻rtem~iafrigida）群落之间差异显著；（2）随着退化演替的进程，群落最大高度和叶片碳氮比减小，群落最大高度在未退化的羊草＋杂类草群落与轻度退化的羊草＋针茅（Stipasp．）群落之间差异显著，碳氮比在未退化的羊草＋杂类草群落与严重退化的羊草＋冷蒿群落之间差异显著；（3）不同退化演替阶段的群落，其土壤养分对植物功能性状的影响有所差异。在羊草＋针茅群落，速效氮与群落最大高度、叶片木质素含量和叶片碳氮比均呈显著负相关关系。而在羊草＋糙隐子草（Cleistogenessquarrosa）群落中，上述3种植物功能性状则表现为均与全磷含量显著正相关；（4）群落植物功能性状之间的关系也因退化阶段不同而有所不同。在轻度退化的羊草＋针茅群落中，叶片木质素含量与其他4个功能性状显著正相关，叶片碳氮比与群落最大高度、叶干物质含量、木质素含量呈显著正相关关系。在严重退化的羊草＋冷蒿群落中，所有性状均呈极显著正相关关系。表明植物通过功能性状的协调或组合，以适应贫瘠的土壤环境。上述结果深化了对典型草原退化演替的认识，对退化草地的恢复与保护具有一定的指导意义。

英文摘要：

Aims Understanding ecological implications of plant functional traits is helpful in exploring community assem- bly under different environments of nature and human disturbances, and then to reveal the maintenance mecha- nism of the ecosystem services. By analyzing vegetation and soil data derived from field observations in Leymus chinensis steppe of Xilin River Basin in Nei Mongol, we aimed to explore the responses of plant functional traits to changing soil nutrients at different degradation stages. Methods We observed 69 plots for both plant community structure and soil attributes using quadrat and soil-drilling methods. Five plant functional traits, namely the specific leaf area （SLA）, leaf dry matter content （LDMC）, leaf carbon to nitrogen ratio （C：N）, leaf lignin content （LLC）, and maximum height （MH）, were meas- ured for each plot. We also tested soil attributes, such as total nitrogen （TN）, total phosphorus （TP）, available ni- trogen （AN）, available phosphorus （AP）, and organic carbon （OC）. The sixty-nine communities were classified into four groups （undegraded L. chinensis ＋ forbs, slightly degraded L. chinensis ＋ Stipa sp., moderately degraded L. chinensis ＋ Cleistogenes squarrosa, and heavily degraded L. chinensis ＋ Artemisia frigida） using TWINSPANsoftware. The relationships between plant functional traits and soil nutrient variables were analyzed for the four community groups using the Pearson＇s correlation test with SPSS 21.0 software. lmportantfindings （1） The soil nutrients decreased with the grassland degradation process and there were sig- nificant differences in TN and TP between the undegraded L. chinensis ＋ forbs and heavily degraded L. chinensis ＋ A. frigida communities; （2） plant functional traits also showed strong differences between the degradation stages. MH and C：N decreased with degradation. A significant difference was observed in MH between the unde- graded L. chinensis ＋ forbs and slightly degraded L. chinensis