Plant and soil responses to defoliation: a comparative study of grass species with contrasting life history strategies

The overall aim of this study was to test for inter-species variation in plant and soil responses to defoliation among a broad range of temperate grass species and life-history strategies. We used a microcosm experiment where a range of grass species differing in life history traits were subjected to different intensities of defoliation, and a range of aboveground and belowground plant and soil responses were measured. All plant attributes, including accumulated shoot biomass, root biomass and root length, showed a strong negative response to defoliation, although plant species exhibited subtle differences in the way that they responded to increased severity of defoliation. Defoliation also exerted a strong influence on soil properties, decreasing soil microbial carbon (C) and the soil microbial C:nitrogen (N) ratio, and increasing inorganic N availability and potential N mineralisation across all species. Despite the wide range in life history strategies, plant species did not differ in their influence on most of the soil variables, except for the rate of nitrate mineralisation, which was lowest under plant species that displayed the least relative detrimental responses to defoliation. Collectively, our results suggest that plant and soil responses to defoliation are reasonably consistent across a broad range of grass species, with only subtle inter-specific differences among species.