Reducing soil CO2, CH4 and N2O emissions through management of harvest residues in Chinese fir plantation

Abstract

Manipulating harvesting residues during harvesting has been promoted as a plausible option to improve national energy security and to reduce GHG emissions.A logical uncertainty regarding removing residues from harvested sites is whether and how GHG emissions will change as a result. In this study, static chamber-meteorological chromatography was used to quantify the impacts of four residue manipulations on CO2, CH4 and N2O flux and their changes over time, as well as to explore forcing mechanisms on all three GHG species in a Chinese fir plantation. Compared with reference (RF, i.e., retained residues), annual soil CO2 emissions in residue burning (RB) increased by 3% in the first year and decreased by 21% in the second year; annual soil CH4 absorption in RB increased in both the first and the second year; and the annual soil N2O emission in RB increased by 71% in the first year but was lower than that of RF in the second year. Compared with RF, annual CO2 emission in residue harvest (NR) increased slightly (2%) in the first year but decreased by 8% in the second year; annual CH4 absorption in NR in the first year was slightly increased, but it was less than half of RF in the second year;and annual N2O emission in NR increased by one times. Compared with RF, mulching after crushing treatment (MT) increased soil annual CO2 and N2O emissions but had little effect on soil annual CH4 absorption. The peak of soil CO2 emission occurred in MT in summer, which was mainly affected by soil temperature, but the temperature sensitivity of soil CO2 flux was affected by soil moisture; the peak value of soil CH4 absorption appeared in MT in autumn, and the main influencing factor was soil moisture; and the peak value of soil N2O emission occurred in NR in spring, which was mainly the result of the combined effect of soil temperature and moisture. The annual cumulative global warming potentials (GWP) ranged from 2.9 to 3.4 Mg C-CO2 ha−1 yr−1; compared with RF, MT increased by 17%, and RB and NR decreased by 7% and 1%, respectively. These results highlight the significant impact of harvest residue management on soil GHG fluxes and provide a data basis for accurate estimation of soil carbon and nitrogen fluxes in plantations.