Shrub cover regulates population dynamics of herbaceous plants at individual shrub scale on the Mongolian steppe

Abstract

Questions Do shrubs regulate herbaceous plant community by modifying seed and plant distributions at the individual shrub scale? Do the magnitude and extent of effects at this scale change with shrub cover? Location A desert steppe, Mandalgobi, Mongolia. Methods We compared soil properties, seed accumulation and the establishment of plants of three functional types (annual forb, perennial forb and perennial graminoid) between shrub microsites (on mounds vs mound interspace) at sites differing in shrub coverage (high and low). Results Shrub patches (a legume Caragana microphylla) promoted seed accumulation but inhibited plant establishment on mounds, relative to the mound interspace, for all functional types. However, the effects varied with shrub cover, particularly in the mound interspace, with responses specific to each functional type. The accumulation of soil and annual forb seeds increased with shrub cover at both microsites. Additionally, the density of annual forbs was positively related to shrub cover in the mound interspace. In contrast, the density of perennial forbs and graminoids decreased with increasing shrub cover at both microsites, possibly because of enhanced sand accumulation. Conclusion Shrubs shape herbaceous plant community by causing differences at the individual shrub scale in seed and plant distributions. Additionally, we showed that individual shrub effects are shrub cover‐dependent: dense shrub stands enhanced the dominance of annual forbs in spite of the negative effect found at the individual shrub scale, whereas perennial forbs and graminoids were less abundant in denser shrub stands. Shrubs can play an important role in structuring plant communities via shrub cover‐dependent variation at microsites.

The effects of woody plant encroachment and wildfire on plant species richness and composition: Temporal changes in a forest–steppe mosaic

“…Similar to our results, Maestre et al (2009) found more vascular plant species in the shrub‐dominated than in uninvaded plots in a regenerating Mediterranean woodland. In agreement with the findings of Koyama et al (2015), our results also suggest that juniper shrubs increase microhabitat diversity and thus provide favourable conditions for different species. According to Soliveres et al (2014a) species richness peaks at intermediate WPE in arid climatic conditions, and this might be the case in more humid ecosystems as well (Tölgyesi et al, 2018).…”

Shrub patch configuration in relation to precipitation and soil properties in Northwest China

“…Root competition for water in xeric regions might also affect patch size and spacing between them (King & Woodell, ). Positive relationship between species diversity of interspace grass (H′) and shrub cover ( r = 0.557 * ) was consistent with previous studies (Chen et al, ; Gaitán et al, ; Hao et al, ; Koyama, Sasaki, Jamsran, & Okuro, ; Ravolainen et al, ). In tundra, shrubs with highly broken forms are usually accompanied by low grass diversity and richness (Ravolainen et al, ).…”

Shrub‐encroached grassland as an alternative stable state in semiarid steppe regions: Evidence from community stability and assembly

“…The existence of shrub canopy could directly alleviate wind and water erosion (Cai et al, 2020), avoid high radiation (Molina‐Montenegro et al, 2016), and moderate temperature (Thompson, Zinnert, & Young, 2017), thereby reducing severe environmental fluctuations in the community and enhancing community stability through a direct effect. Although only a few studies have focused on the effect of shrub cover on the vegetation cover, several researchers have indicated that abiotic environment (such as soil nutrients and abiotic stress) ameliorated by shrub cover promote the growth of neighbouring species, enhance plant diversity, and increase vegetation cover (Koyama et al, 2015; Maestre et al, 2009). In the present study, shrub cover had only a marginal (0.05 < p < 0.10) effect on vegetation cover but a significant ( p < 0.05) effect on species richness and Simpson's diversity (Figure 4a), and there were significant differences in species composition between treatments of low vs. high shrub cover and medium vs. high shrub cover (Figure 2b).…”

“…Second, microclimatic conditions affected by shrubs might act as environmental filters for plant communities (Soliveres, Torices, & Maestre, 2012; Zhou et al, 2018). Previous studies pointed‐out that shrubs could facilitate the establishment of surrounding herbaceous communities by reducing abiotic stress or trapping windblown seeds and propagules (Koyama, Sasaki, Jamsran, & Okuro, 2015; Maestre et al, 2009; Soliveres & Eldridge, 2014), while some other studies showed that shrub encroachment could cause fragmentation (e.g., vegetation patchiness) or desertification by regulating matter cycling such as carbon, surface water, and energy flow (Peng et al, 2013; Xiong, Han, Chen, & Mi, 2004; Zhou et al, 2018). In addition, shrubs either in the landscape or in the individual level could affect the heterogeneity of soil nutrients and light availability, provide different niches for plants and alter interspecific relationships (Koyama et al, 2015; Soliveres & Eldridge, 2014).…”