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

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, Q(10), and temperature-normalized basal respiration at 10 degrees C, R-10. Volumetric soil water content affects both seasonal and inter-annual variation of R-s by suppressing R-10, 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 Q(10), whereas the spatial heterogeneity in R-s was increased by the increase in the tree PAI through the increase in R-10. 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 degrees C), this may not be the unique case only in our study site and gives us a caution when predicting R-s in future wanner environment.