Mammalian browsing impact on regenerating Eucalyptus seedlings in a large commercially managed native forest estate
2009
Di Stefano, Julian | Butler, Kym | Sebire, Ian | Fagg, Peter
Excessive browsing by herbivorous mammals can adversely effect both forestry operations and ecosystem structure and function, and effective management of the problem across large forest estates requires the spatial extent of browsing impact to be determined. We conducted a browsing impact survey within 1.3 million ha of commercially managed Eucalyptus forest, and hypothesised that browsing impact would be related to variables reflecting habitat suitability for a major browsing species, the swamp wallaby (Wallabia bicolor Desmarest), at both large and small spatial scales. A simple spatial analysis showed that browsing severity varied across the landscape, but was high in a number of districts (30,000-100,000 ha land management units) grouped in a similar part of the surveyed area, identifying this region as a focus for management and research. Ordinal logistic regression showed that browsing impact was related to (a) the location of districts and (b) the number of times post-harvest regeneration had been attempted, with browsing impact generally worse in areas where regeneration had occurred twice. The latter result was consistent with our original hypothesis, as multiple regeneration attempts promote high quality habitat patches for wallabies. In most heavily browsed districts browsing severity varied substantially between harvested sites, suggesting that processes operating at the site scale were important. Our results describe the spatial extent of browsing within the surveyed area, and identify high risk localities and states, but additional data are required to understand the processes regulating browsing impact.
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