Spatial upscaling of soil respiration under a complex canopy structure in an old-growth deciduous forest, central Japan

The structural complexity, especially canopy and gap structure, of old-growth forests affects the spatial variation of soil respiration (R_s). Without considering this variation, the upscaling of R_s from field measurements to the forest site will be biased. The present study examined responses of R_s to soil temperature (T_s) and water content (W) in canopy and gap areas, developed the best fit model of R_s and used the unique spatial patterns of R_s and crown closure to upscale chamber measurements to the site scale in an old-growth beech-oak forest. R_s increased with an increase in T_s in both gap and canopy areas, but the effect of W on R_s was different between the two areas. The generalized linear model (GLM) analysis identified that an empirical model of R_s with the coupling of T_s and W was better than an exponential model of R_s with only T_s. Moreover, because of different responses of R_s to W between canopy and gap areas, it was necessary to estimate R_s in these areas separately. Consequently, combining the spatial patterns of R_s and the crown closure could allow upscaling of R_s from chamber-based measurements to the whole site in the present study.