Spatial patterns of plant life-forms along elevation and aridity gradients in temperate deserts of northern Xinjiang, China

Located in the arid hinterland of Central Asia, the mountain temperate deserts in Xinjiang are jointly shaped by elevational geographic constraints and the east-west-oriented drought stress gradient. Nevertheless, the joint coupling relationships between these two gradient factors and community-level vegetation structural attributes across woody and herbaceous plant functional groups remain unclarified quantitatively at present. In this study, we investigated four community structural attributes (plant height, vegetation coverage, population density, and aboveground biomass) across four plant life forms, namely shrubs, semi-shrubs, perennial herbs, and annual herbs, along elevational, latitudinal, and longitudinal gradients in five major desert sub-regions of northern Xinjiang: Altay (n = 159), Tacheng–Yili (n = 164), Bortala and Changji–Urumqi(n = 110) and Eastern Tianshan (n = 94).In total, 527 sampling plots were surveyed during the plant growing season from May to mid-September(Desert field surveys conducted each year from May to September for a total of 3 years); plot numbers were unevenly distributed across subregions according to landscape accessibility and habitat representativeness. No temporal repeated measurements on identical permanent plots were conducted, and all analyses were based on one-off spatial snapshot observations from each plot. Trend-fitting, Single-gradient pattern analysis were applied to examine the correlational relationships between geographic gradients and community structural attributes. The results of this study are as follows: (1) Community structural attributes exhibited pronounced spatial heterogeneity and mostly showed unimodal or parabolic trends along the elevational gradient, with relatively high community performance concentrated in the mid-elevation range of 700–1100 m. This observed elevational unimodal pattern is consistent with the expectation of the mid-domain effect, yet such hump-shaped distributions can also arise from climatic, edaphic or topographic filtering and cannot serve as definitive direct empirical evidence for geometric mid-domain constraints. (2) Community-level vegetation performance tended to decline from the relatively humid western subregions (Tacheng-Yili-Bortala) toward the hyper-arid eastern subregions (Changji-Urumqi, Eastern Tianshan), corresponding to the west-to-east decreasing precipitation gradient driven by westerly circulation. (3) Different plant life-forms displayed distinct correlational adaptive patterns along these combined geographic gradients: shrubs and semi-shrubs maintained relatively stable community dominance under drought and low-temperature conditions; perennial herbs tended to occur in relatively mesic mid-elevation habitats; annual herbs showed high responsiveness to water-related environmental variation. (4) Among surveyed subregions, Eastern Tianshan presented the lowest observed community-attribute values, while the Tacheng-Yili subregion exhibited the highest and most stable community structural status. Collectively, our findings demonstrate correlational associations of elevational constraints and the west-east drought gradient with community structural variation in mountain temperate desert plant assemblages. These observational results provide observational reference for developing region-targeted conservation, grazing management and ecological restoration strategies for Xinjiang’s desert grassland ecosystems.