Temperature sensitivity of soil organic carbon mineralization and beta-glucosidase enzyme kinetics in the northern temperate forests at different altitudes,China
Soil samples,which were collected from three typical forests,i. e.,Betula ermanii forest,coniferous mixed broad-leaved forest,and Pinus koraiensis forest,at different altitudes along the southern slope of Laotuding Mountain of Changbai Mountain range in Liaoning Province of China,were incubated over a temperature gradient in laboratory. Soil organic carbon mineralization rates (C_(min)),soil beta-1,4-glucosidase (betaG) kinetics and their temperature sensitivity (Q_(10)) were measured. The results showed that both altitude and temperature had significant effects on C_(min). C_(min) increased with temperature and was highest in the B. ermanii forest. The temperature sensitivity of C_(min) [Q_(10(C_(min))) ]ranked in order of B. ermanii forest > P. koraiensis forest > coniferous mixed broadleaved forest,but did not differ significantly among the three forests. Both the maximum activity(V_(max)) and the Michaelis constant (K_m) of the betaG responded positively to temperature for all the forests. The temperature sensitivity of V_(max) [Q_(10(V_(max)) ]ranged from 1.78 to 1.90,and the temperature sensitivity of K_m [Q_(10(K_m)) ]ranged from 1.79 to 2.00. The Q_(10(V_(max)) /Q_(10(K_m)) ratios were significantly greater in the B. ermanii soil than in the other two forest soils,suggesting that the betaG kinetics-dependent impacts of the global warming or temperature increase on the decomposition of soil organic carbon were temperature sensitive for the forests at the higher altitudes.