Short-term effects of thinning on soil respiration in a pine (Pinus tabulaeformis) plantation

Respiration was measured at daytime during the growing seasons (May–October) of 2011 and 2012 in a young Pinus tabulaeformis plantation with heavy, medium and light intensity thinning and unthinned control plots in Shanxi province in northern China. Soil temperature, moisture, fine root biomass, amounts of soil organic C and litterfall biomass were also measured. We found that immediately following thinning treatments, soil respiration increased by 8 %–21 % compared with the unthinned control plots during both growing seasons. Thinning significantly affected soil respiration and soil temperature with different thinning intensities, while there were no significant differences in soil moisture among the various treatments. During the growing seasons, the soil respiration rates were positively correlated with the soil moisture: the 19.4 %–54.0 % variation in soil respiration rates in the four thinning regimes are explained by the changes in soil moisture. Meanwhile, a positive correlation was found between soil temperature and soil respiration rates at all sites. The best fitting model with temperature and moisture explained 44.3 % of the variation in soil respiration in the high thinning treatment, 27.6 % in the light thinning treatment, 18.6 % in medium thinning and in the control sites during the measuring periods. Overall, soil respiration is better predicted by soil moisture, soil organic C, live fine root biomass and soil temperature when data are pooled for all thinning treatments over the two growing seasons. The best regression model explained 74.7 % of the total variation in soil respiration over the different thinning intensities for the two sampling periods.