Pushing the limits of C3 intrinsic water use efficiency in Mediterranean semiarid steppes: Responses of a drought-avoider perennial grass to climate aridification
FUNCTIONAL ECOLOGY（2024）
摘要
- Intrinsic water use efficiency (WUEi) reflects the trade-off between photosynthetic carbon gain and water loss through stomatal conductance and is key for understanding dryland plant responses to climate change. Stipa tenacissima is a perennial tussock C-3 grass with an opportunistic, drought-avoiding water use strategy that dominates arid and semiarid steppes across the western Mediterranean region. However, its ecophysiological responses to aridification and woody shrub encroachment, a major land-use change in drylands worldwide, are not well-understood.
- We investigated the variations in leaf stable isotopes (delta O-18, delta C-13, delta N-15), nutrient concentrations (N, P, K), and culm water content and isotopic composition (delta O-18, delta H-2) of paired pure-grass and shrub-encroached S. tenacissima steppes along a 350 km aridity gradient in Spain (10 sites, 160 individuals).
- Culm water isotopes revealed that S. tenacissima is a shallow-rooted grass that depends heavily on recent rainwater for water uptake, which may render it vulnerable to increasingly irregular rainfall combined with faster topsoil drying under climate warming and aridification. With increasing aridity, S. tenacissima enhanced leaf-level WUEi through more stringent stomatal regulation of plant water flux and carbon assimilation (higher delta C-13 and delta O-18), reaching exceptionally high delta C-13 values (-23 parts per thousand to -21 parts per thousand) at the most arid steppes. Foliar N concentration was remarkably low across sites regardless of woody shrub encroachment, evidencing severe water and N co-limitation of photosynthesis and productivity. Shrub encroachment decreased leaf P and K but did not affect S. tenacissima water status. Perennial grass cover decreased markedly with both declining winter rainfall and shrub encroachment suggesting population-level rather than individual-level responses of S. tenacissima to these changes.
- The fundamental physiological constraints of photosynthetic C-3 metabolism combined with low foliar N content may hamper the ability of S. tenacissima and other drought-avoider species with shallow roots to achieve further adaptive improvements in WUEi under increasing climatic stress. A drought-avoiding water use strategy based on early stomatal closure and photosynthesis suppression during prolonged rainless periods may thus compromise the capacity of semiarid S. tenacissima steppes to maintain perennial grass cover, sustain productivity and cope with ongoing climate aridification at the drier parts of their current distribution.
查看译文
关键词
climate aridification,drought avoidance,drylands,foliar nutrients,intrinsic water use efficiency,Stipa tenacissima,stomatal regulation,water and nitrogen co-limitation
AI 理解论文
溯源树
样例
生成溯源树，研究论文发展脉络
Chat Paper
正在生成论文摘要