Post-harvest patterns of carbon dioxide production, methane uptake and nitrous oxide production in a Pinus radiata D. Don plantation [An article from: Forest Ecology and Management]

This digital document is a journal article from Forest Ecology and Management, published by Elsevier in 2006. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
Forest harvest results in the removal of a large reservoir of terrestrial carbon with potential significant effects on net CO"2 emissions, but concomitant effects on other atmospheric trace gas fluxes are poorly understood. We measured CO"2, CH"4 and N"2O fluxes between soils and the atmosphere over 3 years at a recently harvested site under Pinus radiata on a volcanic soil of high-fertility status using replicated, large, in situ chambers to enclose three harvest residue treatments. Temporal changes in CO"2 and N"2O emissions were also measured over a wider harvested area using small chambers. The residue (slash) treatments were a control ('no-slash'), 'normal-slash' typical of the site and 'high-slash' (three times normal-slash). Mass loss was inversely related to all size categories of slash, and averaged 98% for litter and 34% for large wood (76-120mm diameter). C:N ratios generally declined as a result of increased N concentrations. Overall, CO"2-C production was significantly higher (P=0.02) in the 'normal-slash' (by 27%) and 'high-slash' (by 72%) than in the 'no-slash' treatments. An interaction between treatment and time explained (P=0.05) the CO"2-C flux data better than did the interaction between treatment and soil moisture (P=0.07). Evidence from small-chamber CO"2-C flux data collected over a wider area before and after harvest suggested little apparent effect of soil disturbance during harvest. Averaged over 3 years, the annual CO"2-C efflux from the large chambers was 8.3+/-1.1Mgha^-^1. Methane uptake was apparently depressed by surface soil disturbance during harvest, because it increased after harvest by 70% in the 'normal-slash' and 'high-slash' treatments to average 12+/-1kg CH"4 ha^-^1year^-^1. Neither NH"4^+ nor NO"3^--N concentrations had any measurable effect on CH"4 uptake. Despite the high N fertility of the harvest site, N"2O emissions were low overall (0.56+/-0.17kg N"2O-N ha^-^1year^-^1) and differed little between treatments, apart from a spike shortly after harvest. Overall, during the time frame of the first commitment period under the Kyoto Protocol, the three greenhouse gases (CO"2, CH"4 and N"2O) contributed 87, -1 and 14%, respectively, to combined emissions on a CO"2-equivalent basis from this fertile harvest site.