Spatial Upscaling of Soil Respiration under a Complex Canopy Structure in an Old‐Growth Deciduous Forest, Central Japan

Abstract

Abstract: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.

Temporal Variation and Hysteresis of Soil Respiration and Sap Flow of Pinus densiflora in a Cool Temperate Forest, Japan

“…Spatial variation in R s was high, the coefficient of variation of daily summed R s varied from 25% to 28%, and its variation was similar to that of soil water content at 121 points in a 1-ha site in a mature beech forest [8]. The response of R s to environmental factors differs under the canopy and in the gap in a deciduous forest [26]. Continuous measurements of R s in the present study were conducted within 1 m 2 ; the seasonal response of R s could differ at each point.…”

“…R s was measured in three chambers (25 cm diameter, 25 cm height) by using an automatic opening and closing chamber (AOCC) system [26] with a CO 2 probe (GMP343, Vaisala, Helsinki, Finland). After the chamber lid was closed for 5 min, CO 2 concentration data were recorded every 10 s by a data logger (LR8431, Hioki, Nagano, Japan).…”