Vegetation is a key component of ecosystems and plays an important role in ecological protection and control of desertification (Cédric et al. 2013). In recent decades, the economy has developed rapidly and the overall living standards of the human population have improved. However, some problems, such as ecological destruction, environmental degradation, and loss of biodiversity, have followed, posing a serious threat to the sustainable development of society (Barbier et al. 1996; Baranova et al. 2016). Arid areas, where water resources are limited, vegetation is sparse, and the environment is harsh, have become an area where a poor quality of life remains (Irajpoor and Latif. 2011). In recent years, poverty alleviation has been carried out in many regions, especially in China, which is the largest developing country (Qian 2019). General Secretary Jinping Xi proposed that “Lucid waters and lush mountains are invaluable assets,” providing support for ecological protection and restoration, which can promote the development of the economy (Hasan et al. 2017). In view of the harsh natural environment and limited economic development in arid areas, it is necessary to conduct ecological protection and restoration projects in order to achieve a sustainable, stable, and coordinated development of the economy, society, and environment.
Research and application of plant ecological theory is an important part of ecology (Illian et al. 2009). Whether in plains, plateaus, mountains, deserts, or river basins (Lortie and Turkington. 2002; Kirkman et al. 2012; Folega et al. 2014; Guo et al. 2018), composition of vegetation in these areas is closely related to the environmental factors (Espinar et al. 2011; Bayly et al. 2015; Noto and Shurin. 2017). However, structural characteristics of vegetation are affected by many factors and the processes by which vegetation changes is complex (Bertrand et al. 2011; Jacynthe et al. 2017; Estruch et al. 2018). As a result, it is necessary to study of vegetation structure. The characteristics of biodiversity is essential to understanding the relationships between biodiversity and ecological factors (Mahi et al. 2019). Vegetative species diversity is directly related to ecosystem function (Evans et al. 2017; Attarchi and Gloaguen 2018; Little and Altermatt 2018; Ricardo et al. 2019). However, it is unknown whether richness of species can improve the ecosystem function or if a certain number of key species can maintain the function (MacArthur 1955; Elton 1958; Lawton and Brown 1993), Therefore, studies on the change of species diversity can provide a theoretical basis for the evaluation of ecosystem functions, providing basic data for protection and restoration of biodiversity.
Community stability refers to the community's ability to maintain normal dynamics, including resistance stability and resilience stability (Gao et al. 2019). Stability of the plant community, which is one of the most important characteristics of the ecosystem, is a comprehensive feature of the structure and function of plant communities (Tomiolo et al. 2020). Different from simple mathematical or physical systems, ecosystems are complex and many problems require further study (Howeth and Leibold 2010). Studies of ecosystem stability generally require field investigations and data collection or the use of mathematical models to conduct a simulation (Schwartz et al. 2000; Neutel et al. 2014; Uroš et al., 2015; Zhang et al., 2017). However, these different approaches may lead to different conclusions and a more effective method is required. Zheng et al. (2000) proposed a new method where prediction results of community succession were with a comparative analysis.
In arid regions, water, which is the most important natural resource, has a great influence on characteristics of the plant community (Armas and Pugnaire. 2005; Wu et al. 2014; Wang et al. 2017). The lower reaches of the Tarim River is a typical arid region, and vegetation had been seriously degraded due to the river discontinuity before 2000. In this region, an ecological water conveyance project began in 2000. As a result, groundwater depth has increased, vegetative growth has improved, and plant diversity has increased (Aishan et al. 2015). With the implementation of the ecological water conveyance project, the density and coverage of species increased (Hao and Li. 2014). In addition, plant growth improved, the amount of water absorption increased, and transpiration increased (Ye et al. 2010), which led to an increase in the amount of ecological water needed for the growth of vegetation (Liu et al. 2014). However, previous research has only been conducted over short periods of time; the changes in the characteristics of vegetation in response to the ecological water conveyance project over the past 20 years have not been reported. In particular, studies on community stability are rare. We aimed to solve these problems in this study. The following hypothesises were made in this study:
(1) Herbaceous species, which are the most sensitive to water conveyance, increased significantly. (2) Spatial pattern of species tended to be uniform. (3) Ecological water conveyance promoted an increase in community stability, which is currently stable.
Based on these hypothesises, we collected 20 years of monitoring data, including plant names, quantities, ecological characteristics (height, coverage, density), and distribution characteristics, to conduct calculations. The innovation of this study is to clarify the variations in plant community structure, species diversity, and community stability receiving ecological water conveyance, and to propose corresponding coping strategies. With the findings from this study, we can provide a theoretical basis for vegetation protection and restoration for ecological management projects conducted in the lower reaches of the Tarim River. We can also conduct a preliminary evaluation of the benefits of ecological water conveyance. In addition, the results of this study can provide a methodological reference for similar areas and theoretical guidance for the management of water resources in arid areas.