RESPONSES OF DIVERSITY AND INVASIBILITY TO BURNING IN A NORTHERN OAK SAVANNA

摘要: The role of diversity in buffering environmental change remains poorly tested natural systems. Diversity might enhance stability if different species have disturbance susceptibilities (i.e., functional complementarity). Alternatively, decrease because, at high diversity, populations are predicted to be more temporally variable and therefore vulnerable extinction following perturbation. There is the- oretical support for both hypotheses but limited empirical evidence. I examine these issues with experimental burning along a gradient savanna where fire has been suppressed 150 years. examined how two components stability, resistance (invasion by added naturally recruiting species) resilience (recovery the pre- light levels, primary limiting resource this system), varied diversity. also abundance dominant soil depth affected as negatively correlated could hidden impacts (e.g., invasion on shallow soils caused moisture stress). Species- rich communities were stable because they contained fire-tolerant that, despite their rarity, significantly increased cover after fire, reduced availability, seedling survival. Species-poor rapidly invaded, apparently due combined effects (1) trade-offs between competitive ability tolerance (dominants species-poor areas sensitive), (2) low complementarity. Colonization woody plants was higher low-di- versity plots; known form new state that excludes all taxa. dominants appear determine its spatial variation absence alone accounted stability. Without burning, most subordinates confined shallower play minor controlling flows production. Diversity, therefore, important than ecosystem function under undisturbed conditions. If applicable other systems, results indicate loss will compound negative ecosystems respond.