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Logging debris vs. invasives.

Numerous studies describe the impact of logging on the landscape and soil, but very little information exists concerning the impact of either removing or leaving logging debris. Research forester Tim Harrington and Virginia Tech professor Stephen Schoenholtz recently published the results of a five-year study exploring how logging debris can help curb the growth of non-native invasive plants on logging sites. The authors observed the effects of dispersing, piling, and removing logging debris at three Oregon sites where they compared the survival and growth rate of Douglas-fir seedlings. At one site, they found that the invasive Scotch broom plant covered much more terrain following debris piling or removal, and that the survival rate of Douglas-fir seedlings decreased by 30 percent.

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The findings at their Molalla site also confirm the detrimental effect of disturbing logging debris: a 30 percent decrease in growth of the young trees, and an increase to 80 percent of blackberry cover. The study also found that logging debris can limit the growth of other invasive plant species, such as oxeye daisy and velvet grass.

How is it that logging debris suppresses the growth of competing vegetation and promotes that of Douglas-fir? Harrington and Schoenholtz report that as debris decays, it releases nutrients that enhance soil productivity, a vital component of healthy plant growth. Removing debris negatively impacts sites with gravelly or sandy soils, which are in need of the carbon and nitrogen provided by decaying debris.

Furthermore, its removal exposes mineral soil, which gives invasive plants the upper hand over native ones. According to the scientists, the positive effects of on-site, undisturbed logging debris may outweigh the disadvantage of a potential increase in short-term fire risk.

You can read about Harrington and Schoenholtz's study in the Canadian Journal of Forest Research. You can also read more about the subject in a forest service publication: Toward More Diverse Forests: Helping Trees Get Along in a New Organization, which can be seen at: www.fs.fed.us/pnw/sciencef/scifi121.pdf.

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Title Annotation:CLIPPINGS; logging debris and the growth of non-native invasive plants
Publication:American Forests
Geographic Code:1USA
Date:Jun 22, 2010
Words:334
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