Shrub patch configuration at the landscape scale is related to diversity of adjacent herbaceous vegetation

Abstract

Background: Patterns of shrub patches reflect the long-term effects of several environmental drivers; the same drivers may also affect adjacent herbaceous vegetation. The identity of such drivers may be indicated by associating patterns of shrubs and adjacent vegetation. However, such associations have rarely been examined. Aim: Assess the hypothesis that configuration of shrub patches is related to the diversity of adjacent herbaceous vegetation, through the impact of variation in herbivory and/or growing conditions. Methods: Multivariate analyses of the relationship between patch configuration of tall shrubs and diversity of adjacent herbaceous vegetation, across two tundra river catchments in Norway. Results: Configuration of shrub patches was clearly related to α and β diversity of adjacent herbaceous vegetation, independent of concurrent herbivore abundance (estimated from faeces during the study), or growing conditions. Highly-shredded shrub patches (i.e. fragmented patches with high edge density) were associated with grazing-tolerant species and low species richness. Conversely, little-shredded tall shrub patches were associated with grazing-sensitive shrub saplings. This indicates change in herbivory on a timescale longer than that covered by our faeces data. Conclusions: Consistent co-variation of shrub and herbaceous patches in tall shrub tundra supports the hypothesis of impacts of a shared driver. Interpretation of this co-variation points to long-term influence of herbivory as the shared driver.