Water, land, fire, and forest: Multi‐scale determinants of rainforests in the Australian monsoon tropics. Issue 5 (9th February 2017)

• Record Type: Journal Article
• Authors: Ondei, Stefania; Prior, Lynda D.; Williamson, Grant J.; Vigilante, Tom; Bowman, David M. J. S.
• Is Part Of: Ecology and evolution. Volume 7:Issue 5(2017:Mar.)
• Page Start: 1592
• Page End: 1604
• Publication Date: 2017-02-09
• Subjects: Australian monsoon tropics -- fire -- geologic substrates -- rainfall gradients -- rainforests -- topographic fire protection; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.2734
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: The small rainforest fragments found in savanna landscapes are powerful, yet often overlooked, model systems to understand the controls of these contrasting ecosystems. We analyzed the relative effect of climatic variables on rainforest density at a subcontinental level, and employed high‐resolution, regional‐level analyses to assess the importance of landscape settings and fire activity in determining rainforest density in a frequently burnt Australian savanna landscape. Estimates of rainforest density (ha/km 2 ) across the Northern Territory and Western Australia, derived from preexisting maps, were used to calculate the correlations between rainforest density and climatic variables. A detailed map of the northern Kimberley (Western Australia) rainforests was generated and analyzed to determine the importance of geology and topography in controlling rainforests, and to contrast rainforest density on frequently burnt mainland and nearby islands. In the northwestern Australian, tropics rainforest density was positively correlated with rainfall and moisture index, and negatively correlated with potential evapotranspiration. At a regional scale, rainforests showed preference for complex topographic positions and more fertile geology. Compared with mainland areas, islands had significantly lower fire activity, with no differences between terrain types. They also displayed substantially higher rainforest density, even on level terrain where geomorphological processes do not concentrate nutrients or water. Our multi‐scale approach corroborates previous studies that suggest moist climate, infrequent fires, and geology are important stabilizing factors that allow rainforest fragments to persist in savanna landscapes. These factors need to be incorporated in models to predict the future extent of savannas and rainforests under climate change. Abstract : Studies of the distribution of rainforest patches in vast savanna landscapes usually rely on coarse satellite tree cover estimates, which overlook the small rainforest fragments typical of the dry monsoon tropics. We analyzed the influence of climatic variables on rainforest density in the northwestern Australian monsoon tropics and employed high‐resolution regional‐scale analyses to assess the importance of landscape settings and fire activity in determining rainforest density in the northern Kimberley (Western Australia). Our results suggest that moist climate, infrequent fires, topography, and geology are all important stabilizing feedbacks that allow rainforest fragments to persist in frequently burnt savanna landscapes.