Effects of grazing on soil nitrogen spatial heterogeneity depend on herbivore assemblage and pre‐grazing plant diversity

Abstract

Summary The spatial heterogeneity of limiting soil resources is an essential factor determining ecosystem processes and function. It has been reported that large herbivores can strongly impact the variation and spatial distribution pattern of soil nitrogen (N). However, it remains unclear how large herbivores affect soil spatial heterogeneity and whether this influence is dependent on plant community diversity. Here we examined effects of different herbivore assemblages [no grazing; cattle grazing (CG); sheep grazing (SG); and mixed grazing (MG) of cattle and sheep] on soil N spatial heterogeneity in grasslands with high and low pre‐grazing plant diversity in an eastern Eurasian steppe. We found that herbivore grazing generated and maintained spatial patterns of soil nutrients, depending on herbivore assemblage and the level of pre‐grazing plant diversity. CG increased the spatial heterogeneity of soil available N in Leymus chinensis‐dominated steppe meadows, which were independent of pre‐grazing plant diversity. However, the effects of SG and MG strongly depended on grassland plant diversity, with an increased spatial heterogeneity of soil available N in the high‐diversity grassland, but not in the low‐diversity grassland. Synthesis and applications. We concluded that in a L. chinensis‐dominated eastern Eurasian steppe, cattle ranching could be considered as an optimal grazing management protocol to improve soil spatial heterogeneity because cattle grazing (CG) consistently increased soil spatial heterogeneity in the context of both low and high plant diversity. Nevertheless, soil spatial heterogeneity could be improved by any herbivore grazing regime [CG and/or sheep grazing (SG)] when high plant diversity is maintained. These findings highlight the importance of conserving plant diversity to maintain grassland structure and ecosystem function. In grassland systems with high plant diversity, herbivore grazing and plant diversity would jointly improve soil spatial heterogeneity, thus feeding back to maintain higher plant diversity. Therefore, high plant diversity could generate a positive feedback loop of herbivore–plant–soil interactions in grazed grassland systems. Our findings indicate the importance of herbivore assemblages in maintaining spatial heterogeneity in low‐ and high‐diversity grassland systems.

Predicting agronomical and ecological effects of shifting from sheep to cattle grazing in highly dynamic Mediterranean dry grasslands

“…The type of livestock showed little importance in the definition of α‐ and γ‐diversity, but some relevance in defining β‐diversity levels which is consistent with other studies (Ribeiro et al, ; Zhu et al, ). However, both Liu et al () and Tóth et al () indicated that sheep grazing produced lower vegetation richness and diversity than cattle grazing in steppic and temperate habitats, respectively. Sheep grazing seems to be a key management option to improve leguminous species richness, particularly in permanent grasslands (see Ribeiro et al, for an analogous trend on legumes cover).…”

Interactions between global change components drive plant species richness patterns within communities in mountain grasslands independently of topography

“…In the Pyrenees, cattle are reported to increase plant diversity at the plot scale by reducing populations of the most competitive species due to their generalist feeding habit, while the preference of sheep for palatable plants can produce a strong vegetation homogenization effect (Sebastià, de Bello, Puig, & Taull, 2008). On the other hand, sheep are described as outstanding seed dispersers by means of epi-and endozoochory (Liu et al, 2016;Will, Maussner, & Tackenberg, 2007), and have been reported to increase plant diversity at landscape scales in the central Pyrenees (Aldezabal, 2001).…”

Spatial Variability and Geostatistical Mapping of Selected Soil Properties in Mt. Wakakusa Grassland of Japan

“…In case of Mt. Wakakusa, the semivariogram range variability among the examined soil properties may occur under the strong influence of intrinsic factors related to the soil formation process such as topography (e.g., Garten et al 2007), and the impact of extrinsic factors such as the prescribed burning practice (e.g., Boerner & Brinkman 2005) and the dense population of sika deer (e.g., Liu et al 2016) were much less pronounced. The preferable distance of sampling can be referred to as that allows the collection of spatially independent (free of spatial autocorrelation) samples (Rossi et al 1992); thus, the distance that exceeds the semivariogram range is considered appropriate, though spatial dependency usually differs with the sampling scale (Cambardella et al 1994).…”