Effect of cushion plants on the soil seed bank in overgrazed semiarid regions

Abstract

Evaluation of soil seed bank (SSB) in relation to biotic environmental factors could be important in degraded areas, since SSB is one of the major sources that facilitates the recovery of degraded plant communities after disturbances such as grazing, flooding and drought. The aim of this study was to investigate the role of Astragalus myriacanthus and Acantholimon spinosum on SSB characteristics. Soil sampling was carried out in four different positions (upslope edge, downslope edge, center and outside) of each cushion in semiarid mountainous regions in Iran. Then, SSB composition and density, species diversity and richness of SSB in each position were estimated using the germination method. The results of the nonmetric multidimensional scaling showed that the separation of species composition of SSB in four different positions was not possible in any of the cushion species. Nevertheless, the results indicated that the lowest of SSB density, species diversity and richness were observed in the outside of the two cushions. In both cushions, A. myriacanthus and A. spinosum, the mean SSB density (1,606.4 and 646.5 seeds/m2, respectively) was significantly higher in the upslope edge. Totally, the mean density of SSBs in A. myriacanthus (903.6 seeds/m2) was significantly higher than that of A. spinosum (360.6 seeds/m2). We concluded that the cushion plants can act as seed traps and therefore could facilitate recovery of degraded sites in the steep‐hilly areas, while, the possibility of seed penetration into the soil of different directions of cushion might be significant.

Cushion plants as critical pioneers and engineers in alpine ecosystems across the Tibetan Plateau

“…Cushion plants are extremely sensitive to global change (e.g., climate, nitrogen deposition, species invasion, and land use) and thus may indicate ecosystem health and resilience (Gorsuch et al., 2001 ). Specifically, in the context of alpine grassland ecosystem degradation, cushion plants play an important role in improving abiotic and biotic environments and maintaining the stability of the alpine ecosystem (Erfanzadeh et al., 2020 ; Luo et al., 2018 ) (Figure 4 ). Furthermore, cushion plants act as a safe island for settled plants, which can reduce species competition and improve adaptability among species (Meng et al., 2013 ).…”

Cushion plants as critical pioneers and engineers in alpine ecosystems across the Tibetan Plateau

“…Thus, cushion plants exhibit interspecific facilitation, which may be beneficial to maintain species diversity (Fig. 2) (Erfanzadeh et al, 2020). The main effects of cushion plants on the below-ground community are the promotion of the activity of soil microorganism and the enhancement fungal communities to increase the absorption area of roots and maintain microbial community diversity (Fig.…”

“…Cushion plants have high sensitivity to global change (e.g., climate, nitrogen deposition, species invasion and land use), such as their response to freezing-thawing and stress gradients, which may indicate ecosystem health and resilience (Gorsuch et al, 2001). Besides, cushion plants may be indicators of whether the ecosystem is healthy or degradation succession occurs (Erfanzadeh et al, 2020;Luo et al, 2018). Specifically, in the context of alpine grassland ecosystem degradation, the cushion plants play an important role in improving abiotic and biotic environments and the maintenance of alpine ecosystem stability (Fig.…”

Effect of different shrub species on their sub‐canopy soil and vegetation properties in semiarid regions

“…Thus, nurse plants have been mainly considered for restoring vegetation in terrestrial ecosystems that suffer harsh natural conditions such as semiarid areas (Ren et al, 2008). Shrubs, as nurse plants, alter vegetation properties under their canopies with seed trapping, facilitating seed production by understory plants, increasing soil seed bank, increasing soil moisture, protecting the surface soil from erosion, and adding litter into the soil (Erfanzadeh, Hazhir, & Jafari, 2019; Erfanzadeh, Shahbazian, & Zali, 2014; García Sánchez et al, 2012; Mussa, Ebro, & Nigatu, 2016). Although the functions of shrubs have been studied in different ecosystems around the world, the effect of their nursing role in sub‐canopy plants has been hardly compared between different species of shrubs in the semiarid regions.…”