Biodiversity responses to variation in fire regimes in the coal-seam gas region of south-eastern Queensland

[摘要] Highly fire-prone grassy woodlands dominate the coal-seam gas (CSG) development region of south-eastern Queensland, and the CSG industry has identified potential changes to fire regimesas a priority issue for managing impacts of CSG development on biodiversity. This project addresses the question: How sensitive is the biota of these woodlands to variation in fire regimes? It uses results from a controlled fire experiment to model the population dynamics of the dominant eucalypt trees, and examines associations between historical fire regimes and patterns of faunal diversity. Eucalypt populations appear to be limited primarily by water availability, with fire not being a major driver. Changes in tree populations are principally driven by the dynamics of the fire-sensitive native cypress pine (Callitris columellaris), which invades the grassy woodlands in the absence of fire.Patterns of vertebrate diversity in relation to historical fire regimes were examined using 42 survey sites dominated by Poplar box (Eucalyptus populneus), located throughout the southern half of the Brigalow Belt bioregion. Information on fire history was obtained from interviews with local land managers, combined with analysis of Landsat imagery over a 25-year period (1987 - 2012). Totals of 48 reptile species, 63 bird species and 6 small mammal species were recorded. Patterns of ant diversity in relation to historical fire regimes were examined using 45 Poplar box/Silver-leaf ironbark (E. melanophloia) sites in the Maranoa region, with information on firehistory provided by the local land managers. In total, 265 ant species from 50 genera were recorded.Very frequent fire (≥3 fires over 15 yrs) was associated with reduced richness of reptiles generally, and of birds in woodland fragments. The latter appeared to be driven primarily by enhanced abundances of highly aggressive and predatory birds, which have been shown in previous studies to drive out many smaller woodland bird species. For small mammals and ants, richness was lowest in long-unburnt habitat with high cover of native cypress pine. These components of the fauna are adapted to open, grassy habitats, and so habitat favourability for them is reduced by increased canopy cover. We were unable to find any faunal species that was associated with long-unburnt habitat dominated by native cypress pine.Taken together, our results show that the biota of grassy woodlands in the region is highly resilient to a range of moderate fire frequencies (fires occurring approximately every 10-20 yrs), and that it takes either very high fire frequency (i.e. every few years) or a long-term (several decades) absence of fire to cause substantial change in biodiversity. This situation is very different for fire-sensitive brigalow vegetation, where changed fire regimes due to invasion by buffel grass has been identified as a priority conservation threat. Our findings indicate that any modest change in regional fire regimes is unlikely to have a significant impact on biodiversity in eucalypt-dominated grassy woodlands. However, it is recommended that an ongoing fire monitoring programme be established to ensure that marked changes in regional fire regimes are not occurring as a result of CSG development.

[发布日期] 2016-03-31 [发布机构] CSIRO

[学科分类] 地球科学(综合)