Nutrient retention and leaching potential of coarse wood bolts collected from logged and burned upland boreal sites: a greenhouse misting experiment

作者：Morris Dave M^*; Wiebe Scott A; Luckai Nancy J; Reid Douglas E B

来源：Boreal Environment Research, 2015, 20(1): 45-61.

This 16-week, ex situ greenhouse misting trial was designed to isolate and compare the patterns of carbon and nutrient release from coarse woody debris (CWD). Comparisons included: hardwood (aspen) versus conifer (spruce); harvest-versus fire-origin; and among decay classes (DC1 to DC5). In terms of nutrient concentrations in the CWD bolts, with the exception of C and Mn, the aspen logs had significantly higher concentrations than the spruce logs and lower C:N ratios. The spruce logs did, however, contain six times higher levels of Mn as compared with those of aspen. In terms of origin, only Mn was altered (volatilized) as a result of being burned/charred, resulting in significantly lower concentrations levels. As decomposition progressed, there was a general increase in nutrient concentrations, and a reduction in C:N ratios. In all cases, the logs were a source of DOC for both species and decay class. In the case of decay class, DOC leachate was relatively low for the first three decay classes, peaked as a strong source for DC4, then a small, but significant reduction for the DC5 logs. The leachate pattern for N, however, differed in that both DC1 and DC2 logs had negative fluxes, indicating immobilization of N, but thereafter (DC3-5) the CWD leachate was an increasing source of N. For P, K, Ca, Mg, and Mn there was an overwhelming effect on the cumulative flux exerted by species, with significantly higher levels of P, K, Ca, and Mg from the aspen logs, but significantly lower levels of Mn. This pattern corresponds to the weighted concentrations in the logs, with aspen having three to four times higher concentrations of P, K, Ca, Mg, but six times lower levels of Mn. In light of initiatives calling for increased utilization of unmerchantable or low value wood within typical boreal harvesting systems, the current results suggest that careful consideration of the type and amount of CWD (species, decay class) that should be retained on site, as well as consideration for CWD "recruitment" (i.e., green tree retention) should be incorporated into biomass harvesting guidelines.

• 出版日期2015-2-27