Responses of soil enzymes to long-term CO_2 enrichment in forest ecosystems of Changbai Mountains

摘要

A study was conducted to determine the responses of soil enzymes (invertase, polyphenol oxidase, catalase, and dehydrogenase) to long-term CO_2 enrichment at the Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences (42°24′N, 128°28′E; 738 m in elevation) in the northeast China during 1999-2006. Three treatments of the CO_2 enrichment, designed as 500 μmol·mol~(-1) CO_2 open-top chamber (OTC), ambient control chamber and unchambered field (approx. 370 μmol·mol~(-1)CO_2), were conducted with Pinus koraiensis and Pinus sylvestriformis tree species. Soil sampling was made and analyzed separately in spring, summer and autumn in 2006 after the soil enzymes were exposed to elevated CO_2 concentration (500 μmol·mol~(-1)) for eight growing seasons. Results showed that, at elevated CO_2 concentration (500 μmol·mol~(-1)), the activities of invertase (except for the summer samples of P. koraiensis) presented a remarkable decline in all growing seasons, while the activities of dehydrogenase had an increase but only part of the results was remarkable; the activities of polyphenol oxidase in P. sylvestriformis rhizosphere showed a remarkable decrease; the catalase activities increased in spring, while in turn were decline in other seasons. This study also revealed that the soil enzyme activities are significantly correlated with the tree species under the CO_2 enhancement.