半干旱沙地草本植物群落特征对短期降水变化的响应

Response of herbaceous plant community characteristics to short-term precipitation change in semi-arid sandy land

在半干旱地区,降水是制约草本植物群落结构与物种组成最主要的生态因子,而植物群落特征对降水变化的响应研究仍有很多不确定性。针对此现象,于2018年生长季在科尔沁沙地运用野外增减雨装置开展控制试验,通过自然对照、减少30%降水量、减少60%降水量、5月起连续干旱45 d、6月起连续干旱45 d、增加30%降水量、增加60%降水量7种试验处理,以期揭示草本植物群落特征及其物种组成对降水变化的响应,从而为植物生长对降水变化的适应机制研究提供理论依据。研究结果表明:1)减少60%降水量将造成沙地草本群落向单一结构发展,使物种丰富度指数、优势度指数和多样性指数显著减少,其减少率依次为8.57%、1.36%和4.80%,同时降低植物生产力。2)5月起连续干旱45 d对沙地草本植物物种组成、物种多样性和群落生产力无显著影响。3)6月起连续干旱45 d影响沙地草本植物多个物种重要值,导致物种密度减少,但对植物物种多样性和群落生产力影响不显著。半干旱沙地植物群落对长期干旱事件响应较大,对短期极端干旱事件具有一定的抵抗力。

Precipitation is a critically important ecological factor impacting on plant community characteristics and driving the species composition in semi-arid sandy land.However,there is still much that is not known about the response of plant community characteristics to precipitation changes.This study conducted controlled experiments in the 2018 during the growing season using field rain-generation and rain-reduction devices in the Horqin Sandy Land.In order to explore the relationship between community characteristics and precipitation changes.Treatments comprised:the drought commence in May or in June and lasted for 45 days,30%or 60%reduction in natural precipitation,and 30%or 60%increase in natural precipitation.It was found that:1)The rainfall reduction of 60%caused sandy land herb communities to move towards a less complex structure,with species richness index and diversity index showing a significant decline of 8.57%and 4.80%,respectively,and advantage index showing a non-significant decline trend of 1.36%,and an associated reduction in plant productivity.2)Drought of 45 consecutive days from May had no significant effect on the composition,species diversity or community productivity of sandy land herb species.3)Drought of 45 consecutive days from June affected multiple sandy land herb species,resulting in a decrease in species density.However,the effect on plant species diversity and community productivity was not significant.In summary,the plant communities in semi-arid sandy land have some resistance to short-term extreme drought events,but show a greater response to long-term drought events.4)The increase of 30%and 60%precipitation treatments tended to increase community height,community coverage,and above ground biomass,but not significantly so relative to CK.These results help to build a theoretical basis for the understanding of mechanisms of plant community response to precipitation changes.