Abstract
AbstractSlope aspect can affect soil temperature and soil type distribution, which, in turn, is likely to influence plant community composition. Three Qilian mountains, located in the northeastern part of the Qinghai–Tibetan Plateau, China, with four distinct slope aspects including south‐facing (SF), southwest‐facing (SW), northwest‐facing (NW), and north‐facing (NF) slope aspects, were studied to investigate the impact of slope aspect on plant assemblages. The results indicated that the environmental conditions were favorable under the NF and NW slope aspects as the soil water, soil organic carbon (SOC), and soil total nitrogen (STN) contents were significantly higher, and soil temperature (ST) and soil bulk density (SBD) were significantly lower than under the SF and SW aspects. Under all slope aspects, however, SOC, STN, and soil total phosphate in the top 0.2 m of topsoil accounted for about 60% of its total quantity, to a soil depth of 0.6 m. The plant communities on the SF and SW slopes were found to be primarily composed of Poa pratensis, Potentilla anrisena, and Carex aridula. In contrast, the plant community on the NW slope was mainly composed of Kobresia humilis, Carex crebra, and Potentilla bifurca, while on the NF slope it was mainly composed of Picea crassifolia, Carex scabrirostris, and Polygonum macrophyllum. The order of the influence of environmental factors on species distributions was ST > SBD > sand > STN. Results suggest that the slope aspect has an important role in the regulation of the soil environment and plant assemblages and that ST and SBD were the main factors influencing plant community composition. Furthermore, evidence from this study suggests that these mountains will become increasingly vulnerable to global warming. Thus, the plant community composition on these mountains must be monitored continuously in order to allow for strategic adaptive management.
Highlights
Plant community composition, a key topic in ecological studies (Zhang et al 2015), is the result of abiotic and biotic filters that successively constrain which species are likely to persist at a specific site (Lavorel and Garnier 2002)
The lowest soil temperature (ST) was on the NF slope aspect, and it was significantly different from that of the other three aspects
The soil bulk density (SBD) was significantly lower for the NW aspect, at 0.93 g/cm3, than it was for the SF (1.14 g/cm3) and SW (1.03 g/cm3) aspects (Fig. 2D)
Summary
A key topic in ecological studies (Zhang et al 2015), is the result of abiotic (e.g., climate, resource availability, and disturbances) and biotic (e.g., competition, predation, and mutualisms) filters that successively constrain which species are likely to persist at a specific site (Lavorel and Garnier 2002). Plant community composition has complex responses to environmental conditions (Kichenin and Freschet 2013, Kumordzi et al 2015). This can lead to significant uncertainties in the projection of plant assemblages under changing climate and land-use scenarios (Lu€ et al 2015). Sternberg and Shoshany (2001) found that the vegetation structure within a specific site had changed significantly in the short distance separating the north and south-facing slope aspects, which corresponded to the patterns observed in two other sites with respect to the rainfall gradient. Changes in plant community composition are thought to affect the processes of soil respiration (Johnson et al 2008), ecosystem structure and function (Hollingsworth et al 2008), an ecosystem’s response to climate change (Shi et al 2015), and net primary productivity at the ecosystem level due to interactions between plant community composition and environmental drivers (e.g., global warming; Weltzin et al 2003, Cowles et al 2016)
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