Search

Quantitative analysis of the water resources potential is helpful for determining the amount of regional water resources. This in turn is significant for guiding scientific planning and sustainable utilization of regional water resources in the future. In this study, we initially discussed the surface water resources potential of the county units on the northern slope of the Kunlun Mountains by balancing water supply and demand. The analysis considered surface runoff, ecological water demand, and the amount of available surface water to determine the necessity of protecting water resources in this region. The results showed that: (1) The runoff of rivers on the northern slope of the Kunlun Mountains showed a significant increase after 2000, with the average annual runoff increasing by 23.36% from 2001 to 2010 and 42.89% from 2011 to 2020 compared with that before 2000, among which the Qarqan River showed the largest increase and the Hotan River showed the smallest increase. (2) The ecological base flows for the Qarqan River Basin, Keriya River Basin, and Hotan River Basin were 4.67x108 m³, 5.38x 108 m³, and 20.26x108 m³, respectively, and the ecological water demands of natural vegetation were 4.34x108 m³, 4.00x108 m³, and 2.62x108 m³, respectively. (3) The current surface water consumption of each county unit on the northern slope of the Kunlun Mountains ranged from 0.1x108 to 8.73x108 m³, and the potential of surface water resources ranged from -0.07x108 to 3.17x108 m³ ; additionally, the spatial difference was significant. The surface wa- ter resource potential was greater than 2.00x108 m³ in Moyu County, Tiemenguan City 38th Regiment, Qira County, Qiemo County, Hotan County, Minfeng County, and Lop County. The current surface water resources storage capacity of the region is insufficient, and the use of water resources is relatively low. Despite the significant surface water potential of this region, it is difficult to use this water due to regional characteristics; consequently, in the future, the county units on the northern slope of the Kunlun Mountains need to formulate and revise a more appropriate surface water resources usage plan and strengthen the construction of basic surface water conservancy projects to enhance the efficiency of surface water resources allocation and utilization, thus ensuring water resources support for facilitating the region' s development. [ABSTRACT FROM AUTHOR]

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]

Abstract: The photosynthetic characterization of Populus euphratica and its response to the elevated carbon dioxide concentration ([CO2]) were analyzed based on its net photosynthetic rate (P n), stomatal conductance (g s), intercellular CO2 concentration (C i), transpiration rate (T r), and water use efficiency (WUE) at different groundwater depths measured by a portable gas exchange system (LI-6400) in the lower reaches of the Tarim River. The results showed that the elevation of [CO2] decreased the g s, and increased the P n, C i and WUE of P. euphratica. However, the effects of the elevated [CO2] on g s, P n, C i and WUE varied considerably with groundwater depth. The response of photosynthesis to rising [CO2] was stronger at the greater groundwater depth (more than 6m) than that at the shallower groundwater depth (less than 6m). The critical groundwater depth required to maintain the normal survival of P. euphratica was less than 6m. When the groundwater depth increased to more than 6m, P. euphratica encountered moderate water stress, and the plant suffered severe water stress when the groundwater depth increased to more than 7m. [Copyright &y& Elsevier]

Accurate determination of annual leaf litter amount constitutes the basis of scientific leaf litter nutrient release assessment. In this study, we tried to establish an equation between leaf litter amount and relevant tree characteristics of Populus euphratica (P. euphratica) tree on an individual scale, and to find the leaf litter nutrient content variation within 760 d incubation experiment in the main channel of the Tarim River, China. Results showed that there was no proper equation between leaf litter amount and tree height or diameter at breast height. There was great difference in leaf litter amount on an individual scale. The mean annual leaf litter amount per tree was 10.2, 14.83 kg/y obtained by field survey and the equation between annual leaf litter amount and canopy area on an individual scale, respectively. Leaf litter mass changed over incubation time and exhibited three main phases: an initial slow decomposition phase (0–173 d) with mass loss; a rapid mass loss phase (173–290 d); and a second rapid mass loss phase (470–560 d). Overall, carbon (C) and potassium (K) content decreased, and nitrogen (N) and phosphorus (P) content increased in a fluctuating manner over time in the P. euphratica leaf litter. [ABSTRACT FROM AUTHOR]