Soil phosphorus composition and phosphatase activities along altitudes of alpine tundra in Changbai Mountains, China

Alpine tundra ecosystems have specific vegetation and environmental conditions that may affect soil phosphorus (P) compo- sition and phosphatase activities. However, these effects are poorly understood. This study used NaOH-EDTA extraction and solution 31 P nuclear magnetic resonance (NMR) spectroscopy to determine soil P composition and phosphatase activities, including acid phos- phomonoesterase (AcP), phosphodiesterase (PD) and inorganic pyrophosphatase (IPP), in the alpine tundra of the Changbai Mountains at seven different altitudinal gradients (i.e., 2000 m, 2100 m, 2200 m, 2300 m, 2400 m, 2500 m, and 2600 m). The results show that total P (TP), organic P (OP), OP/TP, NaOH-EDTA extracted P and AcP, PD, and IPP activities over the altitude range of 2500-2600 m are significantly lower than those below 2400 m. The dominant extracted form of P is OP (73%-83%) with a large proportion of monoesters (65%-72%), whereas inorganic P is present in lower proportions (17%-27%). The activity of AcP is significantly positively correlated with the contents of soil OP, total carbon (TC), total nitrogen (TN), and TP (P < 0.05), indicating that the AcP is a more sensitive index for responding P nutrient storage than PD and IPP. Soil properties, P composition, and phosphatase activities decrease with increased altitude and soil pH. Our results indicate that the distribution of soil P composition and phosphatase activities along altitude and AcP may play an important role in P hydrolysis as well as have the potential to be an indicator of soil quality.