Conservation of biodiversity and natural resources in a changing climate requires understanding what controls ecosystem resilience to disturbance. Prolonged periods of extreme heat or drought in the first year after fire affect the resilience and diversity of fire-dependent ecosystems by inhibiting seed germination or increasing mortality of seedlings or resprouting individuals. This interaction between weather and fire is of growing concern as climate changes, particularly in systems subject to stand-replacing crown fires. We used a decade of satellite-derived metrics of vegetation dynamics in a Hierarchical Bayesian modeling framework to understand how climate and soils drive post-fire recovery. We also examine the longest running set of permanent vegetation plots in the Fynbos of South Africa (44 years) and relate observed changes in diversity and composition to fire history, extreme weather in the first summer after fire, and alien plant species invasion.
Results/Conclusions
Analysis of post-fire recovery revealed strong post-fire recovery gradients associated with climate resulting in faster recovery in regions with higher soil fertility, minimum winter temperature, and mean summer precipitation. We found also found significant decline in the diversity of plots, driven by increasingly severe post-fire summer weather events (number of consecutive days with high temperatures and no rain) and alien plant invasion. Perennial herbaceous and graminoid species were particularly affected by post-fire weather, while shrub species were sensitive to invasive alien plants. Observed differences in the response of major growth forms and fire-response types could drive major shifts in ecosystem structure and function such as altered fire behavior, hydrology and carbon storage. An estimated 1◦C increase in maximum temperature tolerance of the species sets unique to each survey further suggests selection for species adapted to hotter conditions. This is the first example of climate change impacts on biodiversity in the hyperdiverse Cape Floristic Region and demonstrates an important interaction between extreme weather and disturbance by fire that may make flammable ecosystems particularly sensitive to climate change.