模拟降水变化下黄土丘陵区草地群落特征及其物候期响应

在全球气候变化背景下,黄土高原降水格局呈现出季节波动增强和极端降水事件增加趋势,降水格局变化势必会引起草地群落特征和物候期发生重要改变。为研究黄土丘陵区草地生态系统对降水改变的响应,选取黄土丘陵区退耕草地为研究对象,连续定位观测自然恢复小区不同降雨梯度下(0,±20%,±40%,±60%)物候动态变化,探究了物候期和群落结构对降水变化的响应状况。结果表明:(1)不同降水条件下群落物种组成及丰度存在明显差异,与对照组相比,增雨与减雨均提高了物种的种类。增雨60%群落种类最多,为18种。(2)降水梯度递增处理下,群落盖度呈先增加后降低趋势,地上生物量随呈单峰趋势。增雨20%处理和减雨20%处理均能够显著提高群落植被盖度和地上生物量,地上生物量在增雨处理下明显高于减雨处理。(3)丰富度和Shannon-Wiener指数总体上都呈增加趋势,减雨20%,40%,60%均使Pielou均匀度指数降低。(4)不同降水条件对物种物候期的影响显著(p<0.05),群落返青期、繁殖期和和枯黄期在减雨处理下显著提前,而增雨处理则使其繁殖期和枯黄期发生推迟。综上,群落物种组成、植被盖度和地上生物量在不同降水处理下表现出显著差异,而物种多样性对降水变化响应不敏感。

Characteristics of Grassland Community and Its Ethnological Response in Loess Hilly Regions Under Simulated Precipitation Change

Under the background of global climate change, the precipitation pattern of the Loess Plateau shows a trend of increasing seasonal fluctuations and increasing extreme precipitation events. The change of precipitation patterns are bound to cause important changes in the grassland community characteristics and phenology period. In order to study the response of the grassland ecosystem in the Loess hilly area, the grassland in the hilly area of the Loess Plateau were selected as the research object. the study observed the dynamic change of phenology(0, ±20%, ±40%, ±60%)in the natural recovery community, and explored the response of phenology and precipitation to community structure. The results showed that:(1)Different species composition and abundance under different precipitation conditions, and improved species composition compared with control groups. Species in communities with 60% rain were the largest of 18 species.(2)Precipitation gradient treatment, along with the community cover increased first before decreasing, and the aboveground biomass followed by unimodal trend. Both 20% precipitation treatment and 20% precipitation treatment groups can significantly improve community vegetation cover and aboveground biomass, where aboveground biomass was significantly higher than that under rain reduction treatment.(3)Both the richness and the Shannon-Wiener index showed an overall upward trend, with rain losses of 20%, 40%, and 60% all reducing the Pielou uniformity index.(4)Different precipitation conditions have significant effects on the species phenological period(p<0.001)and the community rejuvenation period. Breeding and dry yellow periods were significantly advanced under rain reduction treatment, while rain increase treatment delayed the breeding and dry yellow periods. The results of this study are expected to provide reference for vegetation restoration and grassland resources development and utilisation in the Loess Plateau. In this paper, the results showed that the community species composition, vegetation cover and aboveground biomass showed significant differences under different precipitation treatments, while species diversity was insensitive to precipitation change responses.