Controls of spatio-temporal patterns of soil respiration in a mixed forest

IntroductionPatterns of soil respiration (Rs) are heterogeneous on temporal and spatial scale. The most important controlling factors of soil respiration are microclimatic conditions such as soil temperature and moisture. However, a strong pronounced seasonality shifts Rs patterns from temperature to moisture-controlled regimes. Rarely investigated patterns are time-lagged effects prior to Rs measurements and influences of trees in mixed forests on large spatio-temporal scales. Material and MethodsWe investigated Rs over two years on a weekly to fortnightly measurement rhythm at an approximately 1 ha area in a mixed forest on 35 predefined locations using the common chamber technique. Analysis was derived using meteorological data and a tree species map. ResultsBy tendency, Rs decreased with increasing distance to the tree and we observed significantly higher Rs in broadleaf patches compared to coniferous and mixed patches during the summer season (+27 %, +18 %, respective). Our data confirmed soil temperature and moisture as important controlling variables. Yet, our results highlight an additional predictor explaining a higher proportion in variability: the vapour pressure in the atmosphere. In contrast to soil temperature and moisture this predictor was able to track a collapse in Rs due to drought and increases following rewetting. ConclusionWe conclude that meteorological conditions might be valuable indicators for CO2 emissions from forest soils. Tree species distribution explained partly the spatial patterns and hot spots of Rs yet additional analysis of local soil properties will enhance our understanding of the soil plant interactions and the resulting Rs.