半干旱黄土区不同管理措施下草地群落结构对短期氮、水添加的响应

氮沉降和降水变异显著影响草地群落结构和功能，但缺乏对不同管理措施下草地群落结构对氮沉降和降水变异响应的研究。为模拟不同管理措施下草地群落结构对氮沉降和降水变异的响应特征，以半干旱黄土区云雾山国家自然保护区典型草原为研究对象，系统分析了在封育、刈割和火烧三种管理措施下，氮添加和水添加对群落地上生物量、功能群组成和群落多样性的影响。结果表明，氮添加和水添加对地上生物量、功能群组成和群落多样性指数的影响因管理措施不同有所差异。（1）在封育草地上，氮添加显著降低物种多样性，对地上生物量影响较小；水添加显著增加物种多样性指数，氮添加和水添加的交互作用显著增加地上生物量、禾本科所占比例和莎草科所占比例；物种多样性指数均与地上生物量无显著相关，与不同功能群所占比例显著相关。（2）在刈割草地上，氮添加和水添加显著提高草地群落地上生物量，氮添加和水添加交互作用尤为显著；氮添加和水添加显著增加物种丰富度指数，对物种均匀度影响较小；杂草类所占比例和地上生物量对Shannon-Weiner多样性指数的贡献率较大。（3）在火烧草地上，氮添加和水添加显著提高群落地上生物量，对物种多样性的影响因年份不同有所差异，氮添加和水添加交互作用具有累加效应；Shannon-Weiner多样性指数与地上生物量呈显著负相关，与莎草科所占比例呈显著正相关。研究表明管理措施显著影响群落结构对氮添加和水添加的响应特征，亦改变生产力和物种多样性的关系模式，为更好地应对全球变化进行草地管理提供数据支撑。

Response of grassland community struction to short-term nitrogen addition and water addition with different management practices in the semi-arid loess region

In the context of global climate change, nitrogen (N) deposition and precipitation variation significantly affect grassland community structure and function. Grassland management has become the research focus in the field of ecology in the past decades. However, little research so far has explored the response of grassland community with different management practices to N deposition and precipitation variation. This study was conducted in the typical grassland of Yunwu Mountain National Grassland Nature Reserve, and systematically analyzed the effects of short-term N addition and water addition on aboveground biomass, functional group composition and community diversity in the fenced grassland, cut grassland and burned grassland, in order to simulate the response of grassland community with different management practices to N deposition and precipitation variation. Results showed that effects of N addition and water addition on aboveground biomass, functional group composition and community diversity indices varied with different management practices. 1) In the fenced grasslands, N addition significantly decreased species diversity indices and had no effect on aboveround biomass. Water addition significantly increased species diversity indices. The interaction of N addition and water addition significantly increased aboveground biomass and the proportions of gramineae and cyperaceae. Species diversity indices were not significantly correlated with aboveground biomass, but species diversity indices had significant correlations with the proportion of different functional groups. The proportion of gramineae and weeds contributed the most to Shannon-Weiner diversity index. 2) In the cut gasslands, N addition and water addition (especially for the interaction of N addition and water addition) significantly increased aboveground biomass. N addition and water addition significantly decreased the proportion of gramineae, but significantly increased the proportion of weeds. N addition and water addition significantly increased species richness index, but had little effect on species evenness. The proportion of weeds and aboveground biomass contributed significantly to Shannon-Weiner diversity index. 3) In the burned grasslands, N addition and water addition significantly increased the community above-ground biomass. The effects of N and water addition on functional group composition and community diversity indices varied with different years. The interaction of N addition and water addition had culnulative effect. Shannon-Weiner diversity index was negatively correlated with aboveground biomass, and positively correlated with the proportion of cyperaceae. In all, management practices significantly affected the response of community structure and functions to N addition and water addition. Management practices also altered the relationship between grassland community primary productivity and species diversity. Community functional group contributed significantly to species diversity. This research might provide data support for the grassland management in response to global climate change.