Wang Jing, Wen Xuefa
Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.
Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD), Nanjing University of Information Science & Technology, Nanjing, China.
Front Plant Sci. 2022 Jul 29;13:909603. doi: 10.3389/fpls.2022.909603. eCollection 2022.
Intrinsic water use efficiency (iWUE) is a critical eco-physiological function allowing plants to adapt to water- and nutrient-limited habitats in arid and semi-arid regions. However, the distribution of iWUE in coexisting species along aridity gradients and its controlling factors are unknown. We established two transects along an aridity gradient in the grasslands of Losses Plateau (LP) and Inner Mongolia Plateau (MP) to elucidate the patterns and underlying mechanisms of iWUE distribution in coexisting species along aridity gradient. We determined leaf carbon (δC) and oxygen (δO) stable isotopes, functional traits related to carbon fixation, and limiting resources. Bulk leaf δC and δO were used as proxies for time-integrated iWUE and stomatal conductance (gs) during the growing season. Our results showed that variability in iWUE within transect was primarily controlled by species, sampling sites and an interactive effect between species and sampling sites. Mean values of iWUE (iWUE) increased and coefficient of variation (CV) in iWUE (iWUE) decreased with an increase in aridity, demonstrating that increases in aridity lead to conservative and convergent water use strategies. Patterns of iWUE and iWUE were controlled primarily by the ratio of soil organic carbon to total nitrogen in LP and soil moisture in MP. This revealed that the most limited resource drove the distribution patterns of iWUE along aridity gradients. Interspecific variation in iWUE within transect was positively correlated with ΔO, indicating that interspecific variation in iWUE was primarily regulated by gs. Furthermore, relationship between iWUE and multi-dimensional functional trait spectrum indicated that species evolved species-specific strategies to adapt to a harsh habitat by partitioning limiting resources. Overall, these findings highlighted the interactive effects of limiting resources and leaf functional traits on plant adaptation strategies for iWUE, and emphasized the importance of considering biological processes in dissecting the underlying mechanisms of plant adaptation strategies at large regional scales.
内在水分利用效率（iWUE）是一种关键的生态生理功能，它使植物能够适应干旱和半干旱地区水分和养分有限的栖息地。然而，沿干旱梯度共存物种的iWUE分布及其控制因素尚不清楚。我们在黄土高原（LP）和内蒙古高原（MP）的草原上沿干旱梯度建立了两条样带，以阐明沿干旱梯度共存物种iWUE分布的模式及其潜在机制。我们测定了叶片碳（δC）和氧（δO）稳定同位素、与碳固定相关的功能性状以及限制资源。叶片总δC和δO被用作生长季内时间积分iWUE和气孔导度（gs）的指标。我们的结果表明，样带内iWUE的变异性主要受物种、采样地点以及物种与采样地点之间的交互作用控制。随着干旱程度的增加，iWUE的平均值（iWUE）增加，而iWUE的变异系数（CV）降低，这表明干旱程度的增加导致了保守和趋同的水分利用策略。LP地区iWUE和iWUE的模式主要受土壤有机碳与总氮之比的控制，而MP地区则受土壤湿度的控制。这表明最有限的资源驱动了沿干旱梯度的iWUE分布模式。样带内iWUE的种间变异与ΔO呈正相关，表明iWUE的种间变异主要受gs调控。此外，iWUE与多维功能性状谱之间的关系表明，物种通过分配限制资源，进化出了特定物种的策略来适应恶劣的栖息地。总体而言，这些发现突出了限制资源和叶片功能性状对植物iWUE适应策略的交互作用，并强调了在大区域尺度剖析植物适应策略潜在机制时考虑生物过程的重要性。
