Wednesday, February 17, 2010

PEER REVIEWED RESEARCH: Limited Benefit of Woody Debris on Regeneration

Deer can limit forest regeneration following logging. Foresters use woody debris to limit deer browsing impacts to new seedlings; it is one tool of many. The idea is this: woody debris creates a physical barrier that protects seedlings from browsing. It is not 100% effective, but it is thought to boost seedling survival by a few percent. In reforestation, a few percent can mean the difference between regeneration success and regeneration failure.

Kruger and Peterson (2009) investigated this technique in northwestern Pennsylvania. They carefully quantified the size of woody debris--this is seldom done in other studies. They found no benefit of leaving woody debris. Beneath and adjacent to woody debris, they found lower seedling densities. Instead, a recalcitrant understory of ferns developed. They argue that woody debris limits light, and this is more important than browsing. This study contradicts conventional wisdom and some of the published literature.

Woody debris retention works in some places at some times. It seems to me that the benefit of woody debris retention will be influenced to a great extent by context dependence. Kruger and Peterson have conducted a careful study and produced some counter-intuitive results. It is incumbent upon other researchers to see how well these results hold up in other locations.

Source: Kruger, L.M. and C.J. Peterson. 2009. Effects of woody debris and ferns on herb-layer vegetation and deer herbivory in a Pennsylvania forest blowdown. Ecoscience 16: 461-469.

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