Complex vegetation responses to soil disturbances in mountain grassland

Abstract

We studied vegetation responses to disturbances originated by ants and voles in subalpine grasslands in the Eastern Pyrenees. We compared the effects of these small-scale disturbances with those of a large-scale disturbance caused by ploughing. We wanted to know if these soil disturbances promoted species richness through the existence of a specific guild of plants colonizing these areas, and if this guild was the same for all soil disturbances, independently of their extent. In general, grassland vegetation seemed to recover relatively quickly from soil-displacement disturbances, and the effects could be scaled up in time and space in terms of species richness and composition. Vole mound composition was similar to that in the surrounding grassland, suggesting that mounds were rapidly colonized by the neighbouring vegetation. Vegetation composition differed between the grassland and the ant mounds. Grasses and erect dicots coped well with repeated disturbance, while rosette-forming species and sedges were very sensitive to it. Landscape processes could be important to understanding recolonization. Species from xeric grasslands were found in mesic grasslands when disturbed by ploughing and on the tops of active ant mounds. Furrows in mesic grasslands recovered well, but decades after disturbance showed long persistence of some xeric species and increased species richness compared to terraces, while xeric grasslands showed decreased richness. This suggests that, because of those disturbances, within-habitat diversity was increased, although landscape diversity was not. However, specific disturbances showed idiosyncratic effects, which could enhance the species richness globally. In ant-affected areas, the grassland itself showed the highest plant species richness, partially associated to the presence of some species with elaiosomes not, or only rarely, found in adjacent grasslands without ant mounds. Therefore, soil disturbances occurring at different spatial scales contributed to complexity in vegetation patterns in addition to abiotic factors and grazing.

Temperature and Moisture Controls of C Fluxes in Grazed Subalpine Grasslands

“…Similar legume and non-legume forb species (Lotus corniculatus, Trifolium pratense, Myosotis sylvatica, and Ranunculus montanum) were found in both cattle-and sheep-grazed plots, in different proportions, as found by Sebastià et al (2008a). For a detailed description of vegetation, plant diversity, and soil at these grassland sites, see Sebastià (2004) and Sebastià and Puig (2008).…”

Effects of Ant Mounds on the Plant and Soil Microbial Community in an Alpine Meadow of Qinghai–Tibet Plateau

“…The higher nutrient levels in ant mound soil are attributed to the accumulation of leaves, seeds, honeydew, feces, and corpses (Yu et al , ) in ant mound areas during ant mound building. Many studies have shown that nutrient enrichment can positively influence seedling establishment (King, ; Jones & Wagner, ; Sebastià & Puig, ). As a consequence, ant mounds may create nutrient‐rich patches and increase soil heterogeneity that further affects plant community structure and dynamics.…”

Vole disturbances and plant community diversity in a productive hay meadow

“…It is expected that, in less productive sites with a low plant canopy, limitation of light competition by disturbances by montane water voles should be less important. Achillea millefolium was also associated with highly disturbed plant communities, which is not surprising considering the fact that this species is typical of intensively grazed grasslands and well adapted to soil disturbances (Sebastià and Puig 2008).…”

“…Contrary to our expectations and to findings of other studies (Questad and Foster 2007;Yoshihara et al 2009), the relative cover of ruderal species was not significantly higher in highly disturbed plant communities. The fact that earth tumuli might be quickly colonized by the neighbouring vegetation (Sebastià and Puig 2008), not allowing exogenous ruderal species to colonize the study site, could explain these results.…”