Fig. 2

Rs, Rh, and Ra for differently aged stands and stand density levels. Values are the mean ± standard deviation (SD). Different lowercase letters (a, b, and c) indicate significant differences (P < 0.05) between different stand density levels. Rs, soil respiration; Rh, heterotrophic respiration; Ra, autotrophic respiration. 27a, 27-year-old stand; 36a, 36-year-old stand; 48a, 48-year-old stand