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Allometries for Widely Spaced Populus ssp. and Betula ssp. in Nurse Crop Systems
Chair of Silviculture, Faculty of Environment and Natural Resources, University of Freiburg, Tennenbacherstr. 4, Freiburg 79085, Germany
Department of Biometrics and Informatics, Forest Research Institute Baden-Württemberg, Wonnhaldestr. 4, Freiburg 79100, Germany
* Author to whom correspondence should be addressed.
Received: 8 September 2013; in revised form: 6 November 2013 / Accepted: 6 November 2013 / Published: 22 November 2013
Abstract: Nurse crops of widely spaced pioneer trees are a silvicultural approach to protect the regeneration of frost sensitive target tree species. If overstorey nurse crops are harvested, they can provide additional short-term benefits through increased biomass production, e.g., for bioenergy. However, the intensification of biomass exports from forests might impact negatively on ecosystem nutrient pools. Thus, precise allometric biomass equations are required to quantify biomass and nutrient removals. Since an analysis of published allometric equations developed for typical, dense aspen or birch forests showed that the tree height-to-diameter ratio correlated positively and the proportion of branch biomass negatively with stand density, we developed new allometric biomass equations for widely spaced aspen and birch growing at 4 x 4 m spacing. These equations yielded a root mean squared error of 13% when predicting total aboveground woody biomass for our sample trees. In contrast, the corresponding root mean squared error produced by allometric biomass equations from the literature ranged between 17% to 106% of actual dry biomass. Our results show that specific allometric biomass equations are needed for widely spaced pioneer trees both for accurate estimates of biomass and the nutrients contained within.
Keywords: allometric biomass equation; nurse crop; Populus ssp.; Betula ssp.; wide tree spacing; h/d ratio; branch biomass allocation
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Stark, H.; Nothdurft, A.; Bauhus, J. Allometries for Widely Spaced Populus ssp. and Betula ssp. in Nurse Crop Systems. Forests 2013, 4, 1003-1031.
Stark H, Nothdurft A, Bauhus J. Allometries for Widely Spaced Populus ssp. and Betula ssp. in Nurse Crop Systems. Forests. 2013; 4(4):1003-1031.
Stark, Hendrik; Nothdurft, Arne; Bauhus, Jürgen. 2013. "Allometries for Widely Spaced Populus ssp. and Betula ssp. in Nurse Crop Systems." Forests 4, no. 4: 1003-1031.