Abstract: The change of global precipitation pattern will affect the aboveground and underground biomass of grassland ecosystem plant communities. In order to explore the effect of precipitation change on the biomass of grassland community,in this study,four simulated precipitation gradient treatments were set up in the desert steppe of Siziwang Banner,namely:50% reduction of natural precipitation,natural precipitation,50% increase of natural precipitation and 100% increase of natural precipitation. The aboveground and belowground biomass and their allocation ratios of plant communities under different precipitation treatments were measured for three consecutive years from 2018 to 2020. The results showed that the aboveground,belowground and total biomass of plant communities increased with the increase of precipitation from 2018 to 2020. The aboveground,belowground and total biomass of plant communities displayed interannual differences due to the enclosure of plots and different annual precipitation. The belowground biomass of plant communities in 0~10 cm and 20~30 cm soil layer were significantly different between different precipitation treatments. In the 20~30 cm soil layer,the belowground biomass of the plant community under the increased water treatment showed a significant increase in that three consecutive years. The proportion of plant biomass allocated belowground was higher in the precipitation reduction treatment (P<0.05). This experiment would provide a theoretical basis for maintaining grassland productivity to cope with future precipitation change under the climate change.

Key words: Precipitation gradient, Aboveground biomass, Belowground biomass, Biomass allocation, Desert steppe

摘要： 全球降水格局变化会对草地生态系统植物群落地上、地下生物量产生影响。为探求降水变化对草地群落生物量的影响，本研究在四子王旗荒漠草原设置了4种模拟降水梯度试验，分别为减少自然降水50%、自然降水处理、增加自然降水50%和增加自然降水100%。2018—2020年连续三年测算不同降水梯度处理下植物群落地上、地下生物量及其分配比例，发现2018年到2020年，植物群落地上、地下和总生物量均随降水梯度增加而增加；模拟降水变化对植物群落地上、地下以及总生物量因为样地被围封和降水量不同而产生年际差异。不同降水处理对0～10 cm和20～30 cm中的植物群落地下生物量影响差异显著，20～30 cm土层中，增水处理下的植物群落地下生物量则表现为三年间均为显著递增。减水处理的植物群落生物量向地下分配比例更高(P＜0.05)。本试验为维持草地生产力应对未来气候变化提供了理论依据。

关键词: 降水梯度, 地上生物量, 地下生物量, 生物量分配, 荒漠草原