Effect of spatial variation of soil respiration rates following disturbance by timber harvesting in a larch plantation in northern Japan

Abstract

Harvesting of trees or the loss of trees due to strong winds may lead to large variations at the ground surface that, in turn, causes spatial and temporal variability of soil respiration. We performed thinning (partial harvest) on a mature larch plantation (ca. 50 yr‐old) in Tomakomai National Forest (Japan) with the purpose of studying the effects of thinning on soil respiration (Rs). We conducted field measurements to determine how soil temperature (Ts), mineral soil water content (MSWC), litter water content (LWC), fine root density, litter density, and carbon to nitrogen ratio (C/N) individually influence soil respiration. Soil respiration values did not differ significantly at the disturbed site. Soil temperature was significantly greater at the disturbed site than at the control site (t‐test= ‐12.7, P<0.05), and the MSWC and LWC did not differ between sites. Despite these observations we found no proof that Ts or MSWC influences Rs. At the disturbed site, LWC appeared to be a primary microclimatic factor driving spatial variations in Rs (r= ‐0.41, P<0.05). Thinning led to large variations in Rs, Ts, fine root density, and litter density. Root and litter densities were 18% (insignificant value) and 15% (t‐test=2.86, P<0.05) lower in the disturbed site, respectively. In fact, variations in soil respiration can be explained on the basis of litter density and C/N.