Introduction
The alpine meadows that occupy more than 35% of the total area of the Qinghai-Tibet Plateau are the main location of alpine livestock husbandry in the area, particularly because of their use as winter and spring pastures (Zhang et al., 2003). The health of such alpine meadows must be measured to enable estimation of the capacity of ecosystem services, such as water and soil conservation and carbon sequestration (Yang, 2002). In recent years, these alpine meadows have undergone succession into multi-steady stages due to disturbances arising from climate change and excessive human activity (Meng et al., 2014). Given the unique household contract system implemented on family ranches on the Qinghai-Tibet Plateau, the landscape has fragmented into multiple succession stages or steady states, resulting in multi-steady stage coexistence within each topographical and climate area (Cao et al., 2007).
Ecosystem succession processes always proceed sequentially, such that the corresponding plant communities organize into a series of hierarchical structures or discrete levels (Jørgensen et al., 2016; Wellemeyer et al., 2019). Livestock grazing is the primary form of disturbance that affects plant community structure, physical and chemical soil properties, and the ability of alpine meadows to maintain ecological and productive stability (Proulx et al., 1998; Yang et al., 2001). In addition, the effects of livestock grazing on plant-soil system organization are complex (Nicola et al., 2010). For example, long-term and high-intensity grazing can affect plant community structure and composition and even trigger the plant community to regime shift (Lin et al., 2022). Such grazing can also alter the accumulation and transformation of nutrients above and below the ground and influence the micro-climate and micro-geomorphology of mini-patches (Gonzalez et al., 2010). Most prior studies have observed that the intensity of livestock grazing and the reaction of a plant community to grazing are coupled to various conditions (Wedin & Tilman, 1996; Klinerová & Dostal, 2020; Lauren, 2018), which means that the examination of mini-patches can be used to evaluate plant communities and predict the trends of plant community succession (Wu et al., 2012).
Compared with other parts of ecosystems, mini-patches are more sensitive and exhibit greater variations in response to disturbance and can thus be considered as indicators of how ecosystems respond to disturbance. Monitoring the characteristics of mini-patches can thus reveal the organizational components of an ecosystem, the survival strategies used by an ecosystem’s plant community to cope with disturbance, and the mechanisms whereby an ecosystem maintains its stability. Mini-patches in alpine meadows can therefore be considered as the basic units of the plant–soil system at fine spatial scales, with their features isolated in function but correlated in space. Consequently, the study of mini-patches in alpine meadows can provide answers to many key questions. For example, are the same types of mini-patches distributed across alpine meadow area of different grazing intensities or only in areas of certain grazing intensities? What factors mainly influence mini-patch distribution and determine the direction of plant community succession in alpine meadows?
In this research, we aimed to improve understanding on the stabilization mechanisms of alpine meadow ecosystems and strengthen theories on restoration management in multi-steady-state coexistence conditions. Therefore, we explored and examined the factors affecting alpine meadow ecosystems under various grazing regimes by studying the characteristics of plant functional groups and topography in mini-patches and grazing intensity in typical alpine meadows on the Qinghai-Tibet Plateau.