Roads, fire and aggressive competitors: Determinants of bird distribution in subtropical production forests
Introduction
Most remaining large areas of native forest are managed primarily for human land uses such as livestock grazing and forestry rather than biodiversity conservation (Norton and Kirkpatrick, 1995, Norton, 1996). However, as more species become threatened due to the effects of habitat fragmentation in heavily cleared regions, the conservation importance of these large forest areas is increasing. It is of critical importance to investigate ways of managing these areas that improve their conservation value, particularly to species threatened by habitat loss and fragmentation.
The impacts of forestry on wildlife include not only those stemming directly from harvesting activity, but also from other forest management and maintenance activities. Forestry-related management practices that can impact wildlife include fuel-reduction burning, vegetation thinning, grazing for fuel reduction, maintenance of particular tree species composition and creation and maintenance of a logging road network (Norton and May, 1994). Prescribed fire to reduce fuel loads is one of the most widespread of forestry practices, and in many cases, little is known of its impact on biodiversity (Granström, 2001). Prescribed fire changes stand structure and understorey characteristics, and reduces the amount of dead wood on the forest floor, resulting in substantial changes to habitat structure for forest-dwelling wildlife species (Abbott, 1999, Date et al., 2002, Stuart-Smith et al., 2006).
While edge effects on fauna are well known from studies of fragmentation, internal edges such as those caused by roads bisecting otherwise continuous forest areas have less frequently been the focus of research. Edges can affect species directly due to altered habitat characteristics (Watson et al., 2004), but can also have indirect impacts by facilitating movement of or creating habitat for competitors, predators and parasites (Forman, 1995, Chace et al., 2003, Batáry and Báldi, 2004). Insectivorous understorey birds in particular have been found to be negatively affected by forest edges. Even narrow unpaved roads can reduce abundance of understorey birds in the vicinity of the road edge (Ortega and Capen, 2002, Laurance, 2004) and decrease movement across roads (Laurance et al., 2004).
In Australia, a suite of small passerines has been undergoing widespread population declines (Barrett et al., 1994, SAC, 2000). These declines have typically been attributed to habitat loss and fragmentation in agricultural areas, the effects of which are often exacerbated by subsequent increases in the aggressive native honeyeater, the noisy miner Manorina melanocephala, which severely impacts avian assemblages through interference competition (Barrett et al., 1994, Major et al., 2001, Piper and Catterall, 2003). The Brigalow Belt of southern Queensland is one of the only regions in temperate and subtropical Australia where large continuous areas of forest remain. These areas present a potential opportunity to conserve large populations of small passerines which are declining elsewhere in the continent. However, the majority of the forests of Queensland's Brigalow Belt Bioregion are currently subject to extensive selective logging of both hardwood (mainly spotted gum Corymbia citriodora) and softwood (white cypress pine Callitris glaucophylla) timber species, and most are under extensive cattle grazing licenses. In order to protect the fire-sensitive softwood resources, fuel-reduction burning occurs in adjacent hardwood areas, and an extensive unpaved road network is maintained. Following from the Queensland Government's introduction of the South-East Forests Agreement, which more than doubled the area of native forest under National Park tenure in the South-East Queensland Bioregion (McAlpine et al., 2005), the Western Hardwoods Agreement is currently being negotiated to reduce native forest logging in the west of the state. In part, this agreement proposes to transfer over 1 million ha of public hardwood forest reserves in subtropical inland Queensland, including the Brigalow Belt, to conservation reserves.
However, tenure change alone is insufficient to achieve improved biodiversity outcomes. Ongoing management is required to deal with the legacy of past land uses and ongoing public concerns such as wildfires, as well as to maintain ecological processes and appropriate disturbance regimes. Furthermore, as timber harvesting of softwood species will continue under the proposal, fuel reduction in adjacent hardwood areas will continue to be a consideration. Continuing forest management is likely to necessitate maintenance of at least some roads. Although the proposed tenure changes will mean a change in focus to managing forests for biodiversity, it is difficult to assess the likely influence of this change as the impacts of current management practices on avian assemblages are largely unknown. Furthermore, the relative value of the hardwood and softwood forest areas for small insectivorous birds has not been documented. This information is required in order for informed recommendations to be made regarding future management of the forests, both those that continue to be managed for timber production and those that are moved to a conservation tenure.
A particular challenge faced by conservation managers in the Brigalow Belt forests is that there is a high abundance of noisy miners even throughout large continuous forest areas (Hando and Hando, 1997). This observation is unexpected given research findings from other parts of Australia which suggest that the noisy miner is primarily an edge species, most abundant in fragmented agricultural landscapes (Loyn, 1987, Piper and Catterall, 2003, Chan, 2004). However, the Brigalow Belt forests are impacted by an extensive logging road network, and the responses of birds to internal edges such as those created by roads are not known in the region. It is possible that the creation of internal edges has facilitated noisy miner invasion into the forest interior. Furthermore, the more open habitat structure promoted by prescribed burning regimes could also favor the noisy miner (Grey et al., 1998, Major et al., 2001, Catterall et al., 2002). This study aimed to: (1) determine whether current forest management practices, namely, prescribed burning and creation and maintenance of road edges, are affecting the distribution of noisy miners and forest bird assemblages, and (2) compare the avifaunas of hardwood and softwood forest in order to assess whether conservation of hardwood forests alone is likely to be sufficient to improve conservation outcomes for avian biodiversity in the Brigalow Belt.
Section snippets
Study area
The study was conducted in the 255 000 ha Barakula State Forest, located north of Chinchilla and Miles in southern Queensland, Australia (Fig. 1). Barakula is the largest working forest in Queensland. The forest is contiguous with Allies Creek and Jarrah State Forests and the areas together cover approximately 356 000 ha. The region has a subtropical climate, with average temperatures at Miles ranging from 19.5 to 33.1 °C in summer and 3.6 to 19.3 °C in winter. The majority of rain falls in summer.
Bird assemblages
Habitat type had a significant effect on the bird assemblages of transects (Global R = 0.455, P < 0.001) with cypress pine sites differing markedly from both regenerating (R = 0.500) and open (R = 0.868) spotted gum sites (Fig. 2). The two categories of spotted gum sites did not differ significantly in their overall avifaunas (R = 0.083). Noisy miners were the greatest contributor to differences between cypress pine and spotted gum sites, accounting for 11.9–14.5% of the difference. In all but three
Discussion
Habitat type, rather than proximity to road edge, appears to be the critical factor influencing bird distribution in Barakula forest, with noisy miners the likely proximate cause of the marked differences in avifauna among habitat types. Noisy miners were almost completely absent from cypress pine sites, and were most abundant in open spotted gum sites, while abundance and species richness of small passerines showed the inverse pattern by being highest in cypress pine sites and lowest in open
Acknowledgements
We would like to thank Barry Traill for suggesting aspects of this research and Stuart Collard for helpful comments on an earlier version of the manuscript. Mark Cant, Gary Alsemgeest and Rosemary Jeremy of DPI Forestry provided valuable support and advice. Gloria Glass and Andrea Kennedy assisted with surveys. Peter Dunn and Andrew Le Brocque provided statistical advice. This research was supported by a USQ ECRP grant to M. Maron.
References (45)
- et al.
Spatial and temporal activity patterns of the brood parasitic brown-headed cowbird at an urban/wildland interface
Landscape Urban Plan.
(2003) - et al.
Influence of remnant and landscape attributes on Australian woodland bird communities
Biol. Conserv.
(2001) Threshold effect of eucalypt density on an aggressive avian competitor
Biol. Conserv.
(2007)Conservation of biological diversity in temperate and boreal forest ecosystems
For. Ecol. Manage.
(1996)- et al.
The influence of wildfire, logging and residual tree density on bird communities in the northern Rocky Mountains
For. Ecol. Manage.
(2006) - et al.
Habitat structure and proximity to forest edge affect the abundance and distribution of forest-dependent birds in tropical coastal forests of southeastern Madagascar
Biol. Conserv.
(2004) The avifauna of the forests of south-west Western Australia: changes in species composition, distribution, and abundance following anthropogenic disturbance
CALMScience
(1999)- et al.
Conservation of woodland birds in a fragmented rural landscape
Pacific Conserv. Biol.
(1994) - et al.
Evidence of an edge effect on avian nest success
Conserv. Biol.
(2004) - et al.
Effects of undergrowth clearing on the bird communities of the Northwestern Meditteranean Coppice Holm oak forests
For. Ecol. Manage.
(2006)
Loss of insectivorous birds along a gradient of human impact in Amazonia
Biol. Conserv.
Noisy Miner irruptions associated with land use by humans in south-east Queensland: causes, effects and management implications
Effect of patch size and bird aggression on bird species richness: a community-based project in tropical/subtropical eucalypt woodland
Proc. R. Soc. Queensland
PRIMER v5: User Manual/Tutorial
Reptile diversity at risk in the Brigalow Belt, Queensland
Mem. Queensland Museum
Impacts of logging, fire and grazing regimes on bird species assemblages of the Pilliga woodlands of New South Wales
Pacific Conserv. Biol.
Variation in local-scale edge effects: mechanisms and landscape context
Ecology
Land Mosaics: The Ecology of Landscapes and Regions
Fire management for biodiversity in the European boreal forest
Scand. J. For. Res. Suppl.
Influence of the Noisy Miner Manorina melanocephala on avian diversity and abundance in remnant Grey Box woodland
Pacific Conserv. Biol.
Evaluation of spatial models to predict vulnerability of forest birds to brood parasitism by cowbirds
Ecol. Appl.
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