Soil Organic Carbon Related Enzyme Activities And The Kinetics At Different Altitudes In The Northern Temperate Forest, China

In this paper, we selected a different location along an altitudinal transect (500-1306 m) on the southern slope of Laotuding Mountain. The main objectives here were to investigate soil enzyme activity, soil carbon mineralization rate, soil enzyme kinetic and the temperature sensitivity of enzyme kinetic parameters at different elevations. Correlation analysis, principal component analysis (PCA), and redundancy analysis (RDA) were used to explore the relationship between soil enzymes and soil properties, and to reveal indirectly the response of soil organic matter decomposition at different elevations, The main conclusions were as following:(1) Soil enzymes are produced by soil microbes, which degrade carbon -containing polymers in soil organic matter, and have been widespread concern of scholars. The aim of this research was to better understand the distribution of soil hydrolase and oxidoreductase, and the drivers factors along the southern slope of Laotuding Mountain in temperate forest soils across seven elevations. The results show that:Except for N-acetyl-β-D-glucosaminidase (NAG), the four soil hydrolase activity, including α-glucosidase (αG), β-glucosidase (βG), β-xylosidase (βX), Cellobiohydrolase (CBH), generally increase with the increasing elevations. Soil oxidoreductase activity with the elevation are inconsistent with the soil hydrolase. The five hydrolytic enzymes showed a significant positive relationship with the soil organic carbon (SOC), particulate organic carbon (POC) (p<0.05), and showed a markedly significant positive correlation with soil dissolved organic carbon (DOC) (p<0.01). Expect for NAG, the four hydrolytic enzymes showed a significant positive relationship with soil water content (SWC), total nitrogen (TN). Soil peroxidase (PER) activity showed a significant positive relationship with SOC, TN, SWC and POC (p<0.05). Soil pH has a positive significant influence on soil polyphenol oxidase (PPO) (p<0.05). The results indicated that soil hydrolase activities were closely related to different forms of soil organic matter content.(2) Enzyme kinetic parameters can describe the process of enzymatic reaction. We studied the changes in the soil organic carbon mineralization, β-glucosidase (βG) kinetics, and their temperature sensitivity, as well as their driving factors along the southern slope of Laotuding Mountain in temperate forest soils. The three vertical sites of vegetation selected in this study were as follows:(1) Ermans birch forest located at 1233 m; (2) dark coniferous mixed broad-leaved forest located at 1060 m; (3) Korean pine forest located at 825 m. The results showed that:the rates of soil organic carbon mineralization (Cmin) of the there forests increased with temperature increase, and showed significant relationships with location and temperature (p<0.05). The rates of soil organic carbon mineralization was the highest at the Birch forest (1233 m). The temperature sensitivity of soil organic carbon mineralization rate (Q10(Cmin)) varied as Birch forest (1233 m)> Korean pine forest (825 m)> dark coniferous mixed broad-leaved forest (1060 m), but the differences were not significant (p>0.05). The maximum activity (Vmax) and Michaelis constant (Km) of βG responded positively to temperature for the three forest soils, and Q10(Vmax/Q10(Km) was significantly greater at Birch forest (1233 m) soil than the other two forests soils, suggesting that the impacts of the global warming on soil carbon dynamics will be sensitive at the higher altitude forest soils.