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Impacts of post-harvest slash and live-tree retention on biomass and nutrient stocks in Populus tremuloides Michx.-dominated forests, northern Minnesota, USA

Forest Ecology and Management

By:
, ,
DOI: 10.1016/j.foreco.2012.11.001

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Abstract

Globally, there is widespread interest in using forest-derived biomass as a source of bioenergy. While conventional timber harvesting generally removes only merchantable tree boles, harvesting biomass feedstock can remove all forms of woody biomass (i.e., live and dead standing woody vegetation, downed woody debris, and stumps) resulting in a greater loss of biomass and nutrients as well as more severe habitat alteration. To investigate the potential impacts of this practice, this study examined the initial impacts (pre- and post-harvest) of various levels of slash and live-tree retention on biomass and nutrient stocks, including carbon (C), nitrogen (N), calcium (Ca), potassium (K), and phosphorus (P), in Populus tremuloides Michx.-dominated forests of northern Minnesota, USA. Treatments examined included three levels of slash retention, whole-tree harvest (WTH), 20% slash retention (20SR), and stem-only harvest (SOH), factored with three levels of green-tree retention, no trees retained (NONE), dispersed retention (DISP), and aggregate retention (AGR). Slash retention was the primary factor affecting post-harvest biomass and nutrient stocks, including woody debris pools. Compared to the unharvested control, stocks of biomass, carbon, and nutrients, including N, Ca, K, and P, in woody debris were higher in all treatments. Stem-only harvests typically contained greater biomass and nutrient stocks than WTH, although biomass and nutrients within 20SR, a level recommended by biomass harvesting guidelines in the US and worldwide, generally did not differ from WTH or SOH. Biomass in smaller-diameter slash material (typically 2.5-22.5 cm in diameter) dominated the woody debris pool following harvest regardless of slash retention level. Trends among treatments in this diameter range were generally similar to those in the total woody debris pool. Specifically, SOH contained significantly greater amounts of biomass than WTH while 20SR was not different from either WTH or SOH. Within P. tremuloides systems, we observed high stocks of smaller diameter slash material for all prescribed slash retention treatments. Most notably, WTH retains much more material than anticipated, up to 50% of available slash. These results reflect the high levels of breakage during winter harvest operations in these stands and, consequently, warrant consideration when anticipating the impacts of biomass harvesting on woody debris pools. Further investigation is necessary to understand how deliberate slash retention levels and season-of-harvest impact woody debris in other forest systems.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Impacts of post-harvest slash and live-tree retention on biomass and nutrient stocks in Populus tremuloides Michx.-dominated forests, northern Minnesota, USA
Series title:
Forest Ecology and Management
DOI:
10.1016/j.foreco.2012.11.001
Volume
291
Year Published:
2013
Language:
English
Publisher:
Elsevier
Publisher location:
Amsterdam, Netherlands
Contributing office(s):
Southwest Biological Science Center
Description:
11 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
278
Last page:
288
Number of Pages:
11
Country:
United States
State:
Minnesota
County:
St. Louis