Historical fire regimes in a poorly understood, fire-prone ecosystem: eastern coastal fynbos

Abstract

We characterised the historical fire regime (1900–2010) in eastern coastal fynbos shrublands, which occur in a poorly studied part of the Cape Floral Kingdom (CFK). Natural (lightning-ignited) fires dominated the fire regime. Fire seasonality decreased from west (Outeniqua region) to east (Tsitsikamma region) within the study area, and between the study area and further west in the CFK. This is consistent with a west–east climatic gradient in the CFK, where rainfall is concentrated in winter in the west, and evenly distributed across months in the east. Median fire return intervals (FRIs) (1980–2010) were broadly comparable to other fynbos areas but estimates varied widely depending on whether or not the data were censored (16–26 years with and 8–13 years without censoring). FRIs appeared to be shorter in the Tsitsikamma, where rainfall and plant growth rates are higher, than in the Outeniqua. The total area burnt annually has increased significantly since 1980, coinciding with an increase in weather conducive to fires, suggesting that fire regimes may be responding to climate change. Frequent recurrence of very large fires and the virtual absence of vegetation in older post-fire age classes are potential causes for concern in achieving fynbos conservation objectives.