Abstract: In this study,referring to the widely accepted classification for anuual rainfall in China,together with the rainfall data of the study area in the desert steppe in Yanchi,Ning Xia,the annual rainfall types were divided as the wet year and dry year. To explore the response strategies,driving mechanisms and the trade-off of investments to aboveground and belowground biomass of the plant community to annual rainfall changes in different annual rainfall types (wet year and dry year),the natural rainfall (CK),increased 50 % rainfall (CK+50%) and reduced 50 % rainfall (CK-50%) treatments were selected to measure the biomass of the functional groups (leguminosae,gramineae and forb) and entire community in wet and dry years,within the global change experiment plot established in a desert grassland of Ningxia in 2017. The results showed that:In dry year,the total and belowground biomass of the community were significantly increased under CK+50% treatment. In wet and dry years,after CK-50% treatment,significantly reduced with the aboveground biomass of leguminosae and gramineae,whereas significantly increased with the root-shoot ratio of the community. In wet and dry years,CK+50% biomass trade-off ratio was more inclined to the aboveground biomass,while CK-50% biomass trade-off ratio tended to the belowground biomass. The changed rainfall mainly directly affected the aboveground biomass of leguminosae and gramineae,then indirectly the aboveground biomass of plant community,and then impacted the total biomass of the community. The results suggested that the response of plant biomass and its proportion of different functional groups to rainfall changes is different both wet and dry years.

Key words: Precipitation change, Desert grassland, Biomass allocation, Trade-offs analysis

摘要： 本研究依据中国常用的降水年型划分标准，结合研究样地当年降雨量数据，把降水年型划分为丰水年和枯水年。为探讨不同降水年型（丰水年和枯水年）下荒漠草原植物群落地上-地下生物量及其权衡关系对降水变化的响应策略及其驱动机制，本研究依托2017年在宁夏荒漠草原建立的全球变化试验样地，选择自然降水（CK）、增加50%降水（CK+50%）和减少50%降水（CK-50%）处理，在丰水年和枯水年测定不同处理植物群落及功能群生物量。结果表明：在枯水年，CK+50%显著增加植物群落地下和总生物量；在丰水年和枯水年，CK-50%均显著降低豆科和禾本科地上生物量，而显著增加群落根冠比；在丰水年和枯水年，CK+50%生物量权衡比更倾向于地上，而CK-50%生物量权衡比趋向地下；荒漠草原降水变化主要通过直接影响豆科和禾本科地上生物量进而间接影响植物群落地上生物量，进而影响群落总生物量。本研究结果表明，无论是丰水年还是枯水年，不同功能群植物生物量及其比例对降水变化的响应有所不同。

关键词: 降水变化, 荒漠草原, 生物量分配, 权衡分析