Variability of soil respiration at different spatial scales in temperate forests

To identify the controlling factors of the variability of soil respiration (R (S)) at multiple spatial scales, R (S) was measured along with environmental factors, tree diameter at breast height (DBH), and soil properties for four typical forest types in northeastern China, including the primary mixed broad-leaved Korean pine (Pinus koraiensis) forest (BKPF), spruce-fir valley forest (SVF), selective cutting of mixed broad-leaved Korean pine forest (SCF), and Korean pine plantation (KPP), throughout the growing season (May-October) in 2013. The variability of R (S) was quantified and compared at the following three spatial scales: among collars within a plot, among plots within a specific forest stand, and among forest stands within the landscape. The average coefficients of variations of R (S) within plots (30-52 %) were significantly higher than those of R (S) among plots (20-25 %) in each forest stand (P < 0.05). The water-filled pore space and mean DBH of trees within 8 m of the measurement collars explained 72 % of the variability of R (S) within the BKPF. The variabilities of R (S) within the SVF, SCF, and KPP were explained by the soil organic C content, soil C:N ratio, and mean DBH and total basal area of trees within a few meters of the measurement collars. The variability of R (S) across the four forest stands was best explained by the soil C:N ratio (R (2) = 0.63, P = 0.001).