Variations in microbial carbon metabolic activities in sedge peatlands along an altitudinal gradient in the Changbai Mountain, China

Microbial metabolic activity plays a critical role in the peatland carbon cycle; nevertheless, the mechanisms behind the change in the microbial metabolic activities in peatlands along an altitudinal gradient have not been well elucidated. We measured the stable carbon isotopic composition (delta C-13) of soil microbial phospholipid fatty acids (PLFAs) as well as climate factors and soil properties in several sedge peatlands along an altitudinal gradient from 400 m to 1500 m in the Changbai Mountain, northeast China. The 8 13 C composition of microbial PLFAs was more depleted (-35.1 parts per thousand - -29.8 parts per thousand) than that of bulk peat (-25.8 parts per thousand similar to -27.5 parts per thousand), and the delta C-13 fractionation of microbial PLFAs was larger at lower altitudes (400-1000 m) than at higher altitudes (1000-1500 m). The carbon isotope fractionation in microbial PLFAs was significantly correlated with mean annual precipitation, mean annual temperature, total phosphorus, dissolved organic carbon concentration and pH. The climate factors had greater influences on delta C-13 fractionation than soil environmental factors in sedge peatlands along an altitudinal gradient. The variations in the delta C-13 composition of microbial PLFAs in our study indicated that the microbial carbon metabolic activity decreased with altitude, and microorganisms decomposed more soil organic matter and released more CO2 into the atmosphere at lower altitudes. In a future warming climate, peatland microbial activity in mid- to high-altitude regions could change significantly and affect greenhouse gas emissions.