Habitat specificity, dispersal and burning season: Recovery indicators in New Zealand native grassland communities

Abstract

Restoration programs for human-disturbed ecosystems rely on a good understanding of how recovery occurs. This requires elucidating the underlying succession process, which depends on species adaptations, their interactions, and the spatiotemporal characteristics of the disturbance. Using spiders, we aim to identify the drivers of succession after burning, commonly used in New Zealand native tussock grasslands, test the hypothesis of post-burning dominance of generalists over specialists, and test the presumption that managed summer burns are more detrimental than spring burns. We established a 7-year experiment, with spring and summer burn treatments and unburned control plots, and sampled annually before and after the burning. We identified changes in spider assemblages and their drivers using clustering and indicator value analyses, and we analysed the response of spider diversity and taxa through linear mixed-effect models. In both spring and summer burns, functional groups and diversity decreased and the density of individuals of generalist species increased. However, spring and summer burn treatments showed no differences in spider diversity and composition. We found evidence that adaptations, such as habitat specificity and dispersal ability, determine the recovery of spider communities, and we suggest a set of indicators for monitoring programs. Time of burning may interact with factors like flammability and fire intensity, reducing differences in the effects of burning between seasons. We recommend planning burns for wet seasons as they are easier to control. To facilitate recolonisation by rare species of spiders of tussock grasslands, we suggest maintaining unburned areas that represent different vegetation types.