The southern pine beetle (SPB),Dendroctonus frontalis, is increasing its ecological range by moving northwards as minimal winter temperatures increase. Over the past decade, SPB has been seen to be increasing in abundance in south and central New Jersey, where it causes tree death. In 2010, NJDEP aerial detection surveys documented over 14,000 acres of mortality in that year alone. With its northward movement, SPB transitions from its usual hosts--loblolly and shortleaf pine--to pitch pine, the dominant conifer species in New Jersey. So, although SPB is a native insect, its movement into New Jersey is not unlike that of an invader. With potentially 'naïve' host trees, limited scientific knowledge, and management policies and practices unused to dealing with large outbreaks, this beetle has the potential to cause significant damage to large tracts of the NJ pine barrens. Established beetle suppression tactics involve the felling of adjacent, healthy trees to provide a treeless buffer around infected trees in order to disrupt pheromone dispersal and the subsequent dispersal of reproductive adults. Both the beetle-induced death of trees and the management strategy of tree felling results in a greater than normal accumulation of both standing dead and felled timber of a variety of size classes that add to the potential fuel load of the forest floor, increasing the chance of wildfire ignition and the severity of wildfires once ignited. This coarse and fine woody debris decomposes slowly and its rate of decomposition is largely dictated by the community of fungi that effect the decomposition. On felling, previously healthy wood will undergo decomposition by a succession of fungal species as the physico-chemical composition of the wood is altered by each successional group of fungi. In contrast, beetle-damaged wood is always inoculated by the beetle with up to three different fungal species. Beetle-damaged wood can contain high concentrations of pitch (oleoresin, a mix of monoterpenes and resin acids), whose production within the tree is rapidly induced as a defense mechanism against the beetles. It is hypothesized that this community of beetle-enhanced fungi, in combination with the increased pitch content, will compete with the natural succession of decomposer fungi to reduce the rate of wood decomposition and, thus, extend the duration of this woody ignition source in the forest. Alternatively, trees killed by SPB might tend to have reduced pitch content, because, depending on the intensity of beetle attacks and the physiological condition of trees, beetle attacks can exceed tree capacity for synthesis of new resin and drain the preformed resin. In this case, wood rotting fungi are likely to invade more rapidly and, hence increase the rate of woody residue decomposition. Our proposed study will investigate interactions between the beetle-derived fungi and the natural wood decomposing fungi in the forest in relation to the decomposition rates of contrasting size classes of standing dead and wood on the forest floor. Our results will feed into the fire prediction models of the Forest Service, which are based on mass of fuel of different classes and their rate of drying; a factor that is significantly affected during decomposition as bulk density of wood is reduced.
|Effective start/end date||7/15/13 → 6/30/16|
- National Institute of Food and Agriculture (National Institute of Food and Agriculture (NIFA))
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