Extreme drought stress shifts net facilitation to neutral interactions between shrubs and sub-canopy plants in an arid desert

The stress gradient hypothesis (SGH) predicts that the importance or intensity of competition and facilitation will change inversely along abiotic stress gradients. It was originally postulated that increasing environmental stress can induce a monotonic increase in facilitation. However, more recent models predicted that the relationship between severity and interaction exhibits a hump-shaped pattern, in which positive interactions prevail under moderate stress but decline at the extreme ends of stress gradients. In the present study, we conducted a field experiment along a temporal rainfall gradient for five consecutive years, in order to investigate interactions in a shrub-herbaceous plant community at the southern edge of the Badain Jaran Desert, and, more specifically, investigated the effects of Calligonum mongolicum, a dominant shrub species, on both abiotic environmental variables and the performance of sub-canopy plant species. We found that shrubs can improve sub-canopy water r...

胁迫梯度假说（stress gradient hypothesis, SGH）预测，竞争与促进作用的重要性或强度会沿非生物胁迫梯度呈反向变化。该假说最初提出，环境胁迫的加剧可诱导促进作用呈单调递增趋势。然而，近年的多项模型研究表明，胁迫强度与种间相互作用的关系呈现驼峰型模式：正相互作用在中度胁迫下占主导地位，但在胁迫梯度的两端会逐渐减弱。本研究连续五年沿时间降雨梯度开展野外试验，以探究巴丹吉林沙漠（Badain Jaran Desert）南缘灌草植物群落的种间相互作用，并进一步聚焦优势灌木物种沙拐枣（Calligonum mongolicum）对非生物环境变量及冠层下（sub-canopy）植物物种生长表现的影响。研究发现，灌木可改善冠层下水分……