Tree manipulation experiment for the short-term effect of tree cutting on N_2O emission: A evaluation using Bayesian hierarchical modeling

摘要

Considerable uncertainty exists with regard to the effects of thinning and harvesting on N2O emissions as a result of changes caused in the belowground environment by tree cutting. To evaluate on the effects of changes in the belowground environment on N2O emissions from soils, we conducted a tree manipulation experiment in a Japanese cedar (Cryptomeria japonica) stand without soil compaction or slash falling near measurement chambers and measured N2O emission at distances of 50 and 150 cm from the tree stem (stump) before and after cutting. In addition, we inferred the effects of logging on the emission using a hierarchical Bayesian (HB) model. Our results showed that tree cutting stimulated N2O emission from soil and that the increase in N2O emission depended on the distance from the stem (stump); increase in N2O emission was greater at 50 than at 150 cm from the stem. Tree cutting caused the estimated N2O emission at 0-40 cm from the stem to double (the % increase in N2O emission by tree cutting was 54%-213%, 95% predictive credible interval) when soil temperature was 25 degrees C and WFPS was 60%. Posterior simulation of the HB model predicted that 30% logging would cause a 57% (47%67%) increase in N2O emission at our study site (2000 trees ha(-1)) considering only the effects of belowground changes by tree cutting during the measurement period.