Inter-annual variation of soil respiration and its spatial heterogeneity in a cool-temperate young larch plantation in northern Japan

抄録

　To understand the magnitudes of temporal variation in soil respiration (R_s) and its spatial heterogeneity, and the effect of abiotic and biotic factors to cause the variation in a young plantation recovering after the clear-cutting of a mature forest, we analyzed 8 year R_s, microclimate, and vegetation data obtained in a young hybrid larch plantation with dense undergrowth of dwarf bamboo Sasa in northern Japan during snow-free periods from 2004 to 2014. R_s was measured by a multichannel automated chamber system and was resolved into two components, temperature sensitivity of respiration, Q₁₀, and temperature-normalized basal respiration at 10°C, R₁₀. Volumetric soil water content affects both seasonal and inter-annual variation of R_s by suppressing R₁₀, whereas soil temperature affects only its seasonal variation. Vegetation recovery had significant effect on both temporal variation and spatial heterogeneity in R_s, although the tree and undergrowth Sasa had different contribution to these variations. Increase in the undergrowth Sasa PAI (plant area index) recovering after clear-cutting increased the R_s through the increase in Q₁₀, whereas the spatial heterogeneity in R_s was increased by the increase in the tree PAI through the increase in R₁₀. These results reveal that the soil water and vegetation has strong effect on the inter-annual variation of R_s and its spatial heterogeneity in the recovering young plantation, in spite of the strong exponential relationship of R_s with T_s in their seasonal variation. Although our results were obtained under the limited range in the inter-annual variation in seasonal mean T_s ( < 2°C), this may not be the unique case only in our study site and gives us a caution when predicting R_s in future warmer environment.