关键词: ¹⁵N分配, 光合特性, 谷氨酸脱氢酶, 谷氨酰胺合酶, 谷氨酸合酶, 硝酸还原酶,  ,  ,  

Abstract: The stoichiometric characteristics and spatial patterns of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) are useful indicators for understanding their responses to global climate change in semiarid areas. In this study, we collected 0-15 cm and 15-30 cm soil samples from seven plots at five altitudes in Maxian Mountain, which is located in the semiarid area, to determine the physicochemical properties of SOC, TN, TP, pH and soil moisture content. The relationships among soil SOC, TN, TP stoichiometry and soil physical and chemical factors were examined. The results showed that: (1) The contents of SOC, TN, TP in the 0-15 cm soil layer were higher than those in 15-30 cm layer. The SOC and TN contents in the top soils increased with elevation, while the TP content did not change. (2) The C∶N ratios first increased and then decreased, while C∶P and N∶P ratios increased with elevation. (3) Soil pH was significantly negatively correlated with SOC, TN content and C∶P ratio in the 0-15 cm soil layer. In the 15-30 cm soil layer, soil pH had no relationship with SOC, TN, TP contents and their stoichiometric characteristics. Soil moisture content was significantly positively correlated with SOC and TN contents both in 0-15 cm and 15-30 cm soil layers. Soil moisture increased with elevation, coinciding with the increases of SOC, TN contents and C∶P, N∶P ratios. Taken together, our results indicated that soil nutrient contents and stoichiometry in the study area were mainly influenced by soil moisture.

Key words: nitrate reductase, glutamate dehydrogenase, glutamine synthetase, ¹⁵N distribution, photosynthetic characteristics, glutamate synthase.