| Abstrakt: |
Simple Summary: Dioecious plants hold an important position in maintaining species diversity and the structural and functional stability of terrestrial plant ecosystems. Populus euphratica (P. euphratica), a prototypical dioecious tree with a global distribution across desert and arid regions, is a notable model plant for investigating mechanisms of environmental stress resistance. In this study, we studied the responses of the sex ratio, age structure, survival curve, growth rate, and WUEi exhibited by male and female P. euphratica in the lower Tarim River to change groundwater depth. We found that the drought tolerance range of males was narrower than that of females; moreover, male P. euphratica were more competitive under mild drought stress, while female P. euphratica demonstrated greater endurance under severe drought stress. These findings elucidated the reason behind gender-based spatial differentiation in P. euphratica from the perspective of specialized water use between males and females and shed new light on the implications of ecological water conveyance management for the restoration, conservation, and rejuvenation of the natural P. euphratica forest. P. euphratica stands as the pioneering and dominant tree within desert riparian forests in arid and semi-arid regions. The aim of our work was to reveal why dioecious P. euphratica in natural desert riparian forests in the lower Tarim River exhibits sexual spatial distribution differences combined with field investigation, tree ring techniques, isotope analysis techniques, and statistical analyses. The results showed that P. euphratica was a male-biased population, with the operational sex ratio (OSR) exhibiting spatial distribution differences to variations in drought stress resulting from groundwater depth change. The highest OSR was observed under mild drought stress (groundwater depth of 6–7 m), and it was reduced under non-drought stress (groundwater depth below 6 m) or severe drought stress (groundwater depth exceeding 7 m). As drought stress escalated, the degradation and aging of the P. euphratica forest became more pronounced. Males exhibited significantly higher growth rates and WUEi than females under mild drought stress. However, under severe drought stress, males' growth rates significantly slowed down, accompanied by significantly lower WUEi than in females. This divergence determined the sexual spatial segregation of P. euphratica in the natural desert riparian forests of the lower Tarim River. Furthermore, the current ecological water conveyance project (EWCP) in the lower Tarim River was hard to fundamentally reverse the degradation and aging of the P. euphratica forest due to inadequate population regeneration. Consequently, we advocated for an optimized ecological water conveyance mode to restore, conserve, and rejuvenate natural P. euphratica forests. [ABSTRACT FROM AUTHOR] |
