Spatial variation in soil respiration is determined by forest canopy structure through soil water content in a mature beech forest

For accurate estimation of soil respiration (SR) in forest ecosystems, temporal and spatial variation in SR and the factors that control these variations must be considered. Although some of the factors underlying temporal variation in SR have been elucidated in recent decades, a large part of spatial variation in SR remains unexplained especially in forest ecosystems with complex structures. Our objectives were to demonstrate spatial variation in daily summed SR (SRdaily) and to examine if spatial variation in SRdaily can be explained by canopy openness which is one of the indexes of forest structure. We conducted simultaneous measurements of SRdaily, soil temperature (ST), and soil water content (SWC) at 121 points. We also measured canopy openness and some forest stand structure indexes in different seasons in 2012 and 2013. The coefficient of variation (CV) of SRdaily ranged from 25 % to 28 %, which was similar to that of SWC (21 % to 28 %). We also found that the spatial variation in SR in other forest ecosystems ranged widely (CV = 14 % to 62 %), and that in our site fell within the range. There was no significant relationship between ST and spatial variation in SRdaily; however, a significant relationship was observed between SWC and spatial variation in SRdaily (P < 0.01) excepted for the measurement conducted in June 2013. Multiple linear regression analysis indicated that canopy openness showed significant positive correlations with SWC during the growing season. And there was no significant relationships between SWC and forest stand structure indexes. In this study, we found that canopy structure influenced SWC, which in turn determined the spatial variation in SR in this mature beech forest. The possible connections could give us new insight for adequate forest carbon management.

Automated summary

This study demonstrated significant positive correlations between canopy openness and soil water content, which influenced the spatial variation in soil respiration in a mature beech forest. The findings suggest that canopy structure plays a role in determining soil respiration patterns, providing new insights for forest carbon management.