Soil nutrient stoichiometries and enzymatic activities along an elevational gradient in the dry-hot valley region of southwestern China

Changes in vegetation type and climate associated with elevation can strongly affect the soil properties, but their effects on soil nutrient stoichiometry and enzymatic activities have rarely been studied. The contents of soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), available phosphorus (AP) and available potassium (AK) and activities of six soil enzymes involved in C, N and P cycles were measured along an elevational gradient in the dry-hot valley region of China. C:P, N:P ratios first increased and then decreased with elevation, with the highest values of 89.57 and 4.07, respectively. AN:AP and AN:AK ratios increased linearly with elevation. Absolute enzymatic activities (i.e. per unit of oven-dried soil) tended to increase slightly with elevation, and specific enzymatic activities (i.e. per unit of SOC), except for phosphatase, first significantly decreased and then increased with elevation. A redundancy analysis showed that variations of soil nutrient content and stoichiometry were explained 76.1% by absolute and specific enzymatic activities. The elevational gradient was associated with a shift in nutrient limitation for ecosystem functions and processes, and the specific enzymatic activities responded more clearly than the absolute enzymatic activities to the elevational gradient in this dry-hot valley region.