Climatic controls on ecosystem resilience: Postfire regeneration in the Cape Floristic Region of South Africa

Abstract

Conservation of biodiversity and natural resources in a changing climate requires understanding what controls ecosystem resilience to disturbance. This understanding is especially important in the fire-prone Mediterranean systems of the world. The fire frequency in these systems is sensitive to climate, and recent climate change has resulted in more frequent fires over the last few decades. However, the sensitivity of postfire recovery and biomass/fuel load accumulation to climate is less well understood than fire frequency despite its importance in driving the fire regime. In this study, we develop a hierarchical statistical framework to model postfire ecosystem recovery using satellite-derived observations of vegetation as a function of stand age, topography, and climate. In the Cape Floristic Region (CFR) of South Africa, a fire-prone biodiversity hotspot, we found strong postfire recovery gradients associated with climate resulting in faster recovery in regions with higher soil fertility, minimum July (winter) temperature, and mean January (summer) precipitation. Projections using an ensemble of 11 downscaled Coupled Model Intercomparison Project Phase 5 (CMIP5) general circulation models (GCMs) suggest that warmer winter temperatures in 2080-2100 will encourage faster postfire recovery across the region, which could further increase fire frequency due to faster fuel accumulation. However, some models project decreasing precipitation in the western CFR, which would slow recovery rates there, likely reducing fire frequency through lack of fuel and potentially driving local biome shifts from fynbos shrubland to nonburning semidesert vegetation. This simple yet powerful approach to making inferences from large, remotely sensed datasets has potential for wide application to modeling ecosystem resilience in disturbance-prone ecosystems globally.hierarchical Bayesian | ecology | fire | climate | remote sensing I n many ecosystems, climate change will exert its most powerful impacts via disturbance, such as outbreaks of forest pests (1), species invasions (2), and fire (3). A key feature of ecosystems' response to disturbance is the recovery time, the time required for the ecosystem to return to a state similar to its state before disturbance [called "engineering resilience" by Peterson et al. (4)]. Rapid recovery from disturbance is associated with high resilience-that is, the ability of the system to return reliably to its previous state (5). Slow recovery can signal an approaching catastrophic jump to an alternative state (6) or, given frequent disturbance, chronically lower function (7).Fire is one of the most widespread and important forms of disturbance globally, occurring as an important feature in more than 50% of the world's terrestrial ecosystems (8). However, the risk of climate change is difficult to assess because fires are not well represented in global ecosystem models (9). There is growing evidence of increased fire frequency, severity, and/or size in many regions, due in large part to warming and i...

Environmental drivers of demographic variation across the global geographical range of 26 plant species

“…). A predicted further decrease of fire return intervals (Wilson, Latimer & Silander ) will almost certainly reduce fecundity of our study species. Enright et al .…”

Functional traits explain the Hutchinsonian niches of plant species

“…In particular, the CFR biodiversity hotspot is experiencing shorter fire intervals, in addition to hotter and drier conditions (Wilson, Latimer, & Silander, 2015) known to cause local species loss (Slingsby et al, 2017). In particular, the CFR biodiversity hotspot is experiencing shorter fire intervals, in addition to hotter and drier conditions (Wilson, Latimer, & Silander, 2015) known to cause local species loss (Slingsby et al, 2017).…”

Intensifying postfire weather and biological invasion drive species loss in a Mediterranean-type biodiversity hotspot

“…Cape Floristic Region | Fynbos | South Africa | biodiversity | climate change A mid mounting evidence of climate change impacts on living systems (1)(2)(3), there is increasing concern about changing disturbance-climate interactions and their potential impacts on biodiversity and ecosystem function (4)(5)(6)(7)(8)(9). Fire is a ubiquitous driver of disturbance across the globe and is essential for the healthy functioning and maintenance of many ecosystems (10,11), but changes in fire regime or postfire weather may drive major shifts in the composition, structure, and function of ecosystems (12).…”

“…Fire is a ubiquitous driver of disturbance across the globe and is essential for the healthy functioning and maintenance of many ecosystems (10,11), but changes in fire regime or postfire weather may drive major shifts in the composition, structure, and function of ecosystems (12). Changes in climate and weather can alter fire regimes (7,8), whereas increasingly extreme or prolonged periods of heat or drought in the years immediately after fire may affect ecosystem resilience and diversity by inhibiting seed germination or increasing mortality of seedlings or sprouting individuals (13)(14)(15). Where these impacts alter the functional composition of communities, this change can drive major changes in ecosystem structure and function (16)(17)(18).…”