森林草原过渡带持久土壤种子库沿降水梯度的格局

Changes of persistent soil seed bank along a precipitation gradient in forest-steppe ecotone

为了解全球气候变化背景下森林草原过渡带持久土壤种子库对未来降水减少的响应,本研究以呼伦贝尔森林草原过渡带为研究区域,沿降水梯度采集0~10 cm土层的持久土壤种子库样本,研究种子库密度、物种组成、多样性及其与地上植被的关系,并利用结构方程模型研究年降水量对持久土壤种子库的直接影响及其通过地上植被和土壤有效氮、有效磷、土壤pH值产生的间接影响。结果表明:随着降水量的降低,种子库密度和物种丰富度有增加趋势,森林草原过渡带草地土壤种子库物种多样性高于森林。土壤种子库与地上植被相似性整体较低。结构方程模型结果显示,年降水量对种子库的密度和物种丰富度的总效应为负效应,标准路径系数为-0.051和-0.122。年降水量对种子库的密度和物种丰富度的直接效应为正效应,降水量通过土壤全氮对种子库密度和物种丰富度产生显著的间接正效应,通过土壤pH和土壤有效磷对种子库物种丰富度产生显著的间接负效应,通过土壤pH对种子库密度产生显著的间接负效应。气候变化下降水减少会改变植物应对风险的策略,森林草原过渡带的持久土壤种子库对应对未来可能发生的降水减少具有一定的缓冲作用。

This study aimed to examine the responses of persistent soil seed bank to future precipitation reduction of global climate change in the forest-steppe ecotone of Hulunbuir.Samples of soil seed bank were collected from 0-10 cm soil layer along a precipitation gradient.We examined the density,species composition,diversity of seed bank and their relationship with vegetation.Structural equation model was used to explore the direct impact of annual precipitation on soil seed bank and the indirect impact through vegetation,soil nitrogen,soil phosphorus,and soil pH.The results showed that seed bank density and species richness were negatively correlated with annual precipitation.The species diversity of soil seed banks in grasslands was higher than that in forests.The similarity between soil seed bank and vegetation was generally low.The results of structural equation model showed that the effects of annual precipitation on seed bank density and species richness were negative,with the standard path coefficients of-0.051 and-0.122,respectively.The direct effect of annual precipitation on seed bank density and species richness were positive.Precipitation had indirect and positive effect on seed bank density and species richness through soil nitrogen,a significantly indirect negative effect on seed bank species richness through soil pH and soil available phosphorus,and a significantly indirect negative effect on seed bank density through soil pH.The reduction of precipitation under furture climate change might alter the hedging strategies of plants.The persistent soil seed bank in the forest-steppeecotone had a potential buffering effect against future precipitation reduction.