Influence of patch characteristics on browsing of tree seedlings by mammalian herbivores

Abstract

Summary 1.In south-eastern Australia, browsing of commercial tree seedlings by mammalian herbivores in plantation forestry incurs a large economic cost to the industry, through its effect on tree survival, growth and form. In the absence of lethal methods to control herbivore populations, appropriate manipulation of vegetation through silvicultural management may reduce browsing but it relies on understanding the feeding responses of the herbivores to such changes. 2. We evaluated the extent to which vegetation patch characteristics affected browsing of pine Pinus radiata seedlings by generalist mammalian herbivores, including redbellied pademelons Thylogale billardierii , Bennett's wallaby Macropus rufogriseus rufogriseus and the common brushtail possum Trichosurus vulpecula . 3. In field trials, browsing of pine seedlings was greatest when they were located in patches of high quality, i.e. palatable short vegetation (grass), intermediate in high-quality tall vegetation ( Lomandra longifolia ) and least in low-quality tall vegetation (bracken and shrub). Patch structure also affected browsing: in low-quality patches pine seedlings were browsed more in short vegetation patches (12-24 cm shorter than the seedling) than in tall vegetation patches (at least as tall as the seedling). This difference was at least partly because herbivores took, on average, 2 weeks longer to locate seedlings in tall than in short vegetation. 4. In trials with captive red-bellied pademelons and brushtail possums, pine seedlings were browsed similarly in small short grass and soil patches. However, when these patches were large and spatially separated, they were browsed more in short grass than soil patches. Selection at the patch or individual plant level therefore depended on spatial scale and proximity of the patches. 5. Synthesis and applications . The influence of patch characteristics on browsing has the potential to be exploited for the management of browsing damage to commercially important tree seedlings in forestry plantations. Retention of relatively tall vegetation, particularly if it is unpalatable, in areas at risk of heavy browsing, for example by delaying the use of herbicide, may be a useful management strategy for reducing browsing. This needs to be weighed against the potential detrimental competitive effects of neighbouring vegetation on the seedlings.

Influences de la sylviculture sur le risque de dégâts biotiques et abiotiques dans les peuplements forestiers

“…Several tree diseases (such as H. annosum) spread through root contacts and the presence of non-host trees may limit this process (Linden and Vollbrecht, 2002). Some forest insects (Watt, 1992) and mammalian herbivores (Pietrzykowski et al, 2003) use visual cues to locate their host, and the presence of other tree species can effectively hide the host trees. Conifer-inhabiting bark beetles are able to perceive non-host volatiles released by angiosperm trees and to use them to avoid non-suitable habitats (Zhang and Schlyter, 2004).…”

Evaluating effects of nursery and post-planting nutrient regimes on leaf chemistry and browsing of eucalypt seedlings in plantations

“…It is noteworthy that the high-fertilizer treatment at Cressy sustained enough damage to affect growth (Bulinski and McArthur, 1999), yet the use of low fertilizer in the nursery was an effective method for reducing this to non-problematic levels. Under extreme browsing pressure, this method may contribute towards an overall browsing management strategy when combined with other techniques, such as the use of more resistant genotypes (O' Reilly-Wapstra et al, 2002) in combination with cover crops or other vegetation for reducing browsing (Pietrzykowski et al, 2003) and through effective plantation design (Bulinski and McArthur, 2003).…”

Spatially complex neighboring relationships among grassland plant species as an effective mechanism of defense against herbivory

“…Although such neighborhood effects have been well documented, the studies were limited in that only an individual plant's risk of herbivory was investigated and the consequence of neighbor effects at different patches was studied in isolation. Most previous studies on associational defense focused on how characteristics of neighboring vegetation influence the consumption of a focal plant within a given vegetation patch, or on comparing consumption of the focal plant between different patches with different neighbors (Pietrzykowski et al 2003;Baraza et al 2006;Miller et al 2009). A few studies, however, considered the herbivory risk of the whole plant population and the overall neighborhood effects.…”