Low resistance of montane and alpine grasslands to abrupt changes in temperature and precipitation regimes

High-elevation ecosystems will experience increasing periods of above-average warmth and altered precipitation changes because of climate change. This causes uncertainties for community properties such as productivity and biodiversity. Increasing temperature may increase productivity by increasing growing season length and metabolic rate or decrease productivity by causing drought stress. Competitive outcomes between species may change with altered climatic conditions, causing shifts in community composition. This study investigates the resistance of aboveground biomass and plant community composition of montane and alpine grassland ecosystems to abruptly altered temperature and precipitation conditions. Intact plant-soil communities were translocated downslope spanning an elevational gradient of 2,090 m in the European Alps. We hypothesize that increasing temperature leads to (1) increased aboveground biomass in the absence of precipitation deficits, (2) decreased species richness, and (3) shifts in plant community composition. After one year of exposure to their new environment, aboveground biomass changes appeared to be dependent on precipitation regimes, whereas species richness declined consistently with changed climatic conditions. No deterministic shift in community composition was found. Abrupt changes in climatic conditions can lead to rapid responses of community properties, indicating that these high-elevation communities may have low initial resistance to future heat waves and droughts.

受气候变化影响，高海拔生态系统将经历愈发频繁的高于平均水平的暖期，以及降水格局的改变。这给群落生产力、生物多样性等群落属性带来了诸多不确定性。气温升高既可能通过延长生长季长度、提升代谢速率来提高群落生产力，也可能通过引发干旱胁迫降低生产力。物种间的竞争关系会随气候条件改变发生变化，进而驱动群落组成发生更替。本研究聚焦山地与高寒草原生态系统的地上生物量和植物群落组成对温度、降水突变的抗性。研究将完整的植物-土壤群落沿海拔梯度向下迁移，跨越欧洲阿尔卑斯山脉2090米的海拔范围。我们提出如下假说：气温升高将导致（1）在无降水亏缺的情况下地上生物量增加；（2）物种丰富度下降；（3）植物群落组成发生改变。经过一年的新环境暴露后，地上生物量的变化似乎取决于降水格局，而物种丰富度则随气候条件改变持续下降。未观测到群落组成出现确定性的更替。气候条件的突变可引发群落属性的快速响应，这表明此类高海拔生态系统对未来热浪与干旱的初始抗性较低。