Abstract:

In order to explore spatiotemporal dynamics of soil extracellular enzyme activity (EEA) and its influence on potential mineralization rate of soil organic carbon (SOC) of the Daxing’an Mountain range, soil samples of three forests (Pinus sylvestris forest; Birch forest; Larch pine forest) and three ground cover plants in Larch forest (Grass; Ledum; Moss) were collected from Daxing’an Mountain range in summer and winter. Activities of six enzymes including carbon- (C) (β-1,4-glucosidase, β-1,4-xylosidase, β-D-cellobiohydrolase), nitrogen- (N) (N-acetyl-β-glucosaminidase, leucine aminopeptidase) and phosphorus- (P) (acid phosphatase) acquisition, potential mineralization rate of SOC and main environmental factors were analyzed and potential driving mechanisms were explored. Results showed that Both Pinus sylvestris forest and Birch forest exhibited significant higher activities of enzyme C, N and P in summer, however, Larch forest showed contrary seasonal dynamic with soil EEA of moss soil significantly higher in winter. From summer to winter, soils of three forests and three ground cover plants all experienced reduced P vs. N limitation. Besides, soils of Pinus sylvestris forest and Birch forest both experienced increased C vs. nutrient limitation, however, Larch forest showed contrary seasonal dynamics with the existence of moss. In Pinus sylvestris forest and Larch forest, potential mineralization rate of SOC exhibited higher in winter while Birch forest showed contrary trend. Analysis showed that potential mineralization rate of SOC was influenced by enzyme C and enzyme N significantly, whereas little influenced by enzyme P. C vs. nutrient limitation had little correlation while P vs. N limitation had significant negative correlation with potential carbon mineralization rate.

Key words: soil extracellular enzyme, potential carbon mineralization rate, seasonal dynamics, forest types, ground cover plants

摘要：

为探索寒温带土壤胞外酶活力的时空动态, 并分析胞外酶对土壤潜在碳矿化速率的影响, 于夏季和冬季在大兴安岭采集3种植被(樟子松、白桦和落叶松)的森林土壤和落叶松林中3种地被层(草本、杜香和苔藓)的土壤, 分别测定与碳(β-葡萄糖苷酶、β-木糖苷酶和纤维二糖水解酶)、氮(N-乙酰-β-D-葡萄糖苷酶和亮氨酸氨基肽酶)、磷(酸性磷酸酶)代谢相关的6种胞外酶活力、潜在碳矿化速率和主要的环境因子。结果表明, 樟子松林和白桦林土壤冬季胞外酶活力均显著低于夏季, 而落叶松林则由于林下苔藓层土壤冬季显著增加胞外酶活力, 呈现不一致的规律。从夏季到冬季, 3种森林类型及3种地被层植物土壤一致地表现为磷限制减弱, 氮限制增强; 樟子松林和白桦林土壤均表现为能量限制增强, 养分限制减弱, 落叶松林土壤则由于苔藓层的相反趋势表现为夏季具有较强的能量限制, 冬季具有较强的养分限制。樟子松林和落叶松林土壤在冬季具有较强的潜在碳矿化速率, 而白桦林则相反, 夏季大于冬季。土壤潜在碳矿化速率受碳代谢酶和氮代谢酶的影响较大, 几乎不受磷酸酶的影响, 但土壤中氮磷元素的相对限制情况对有机碳分解的影响较大, 表现为磷比氮的限制增强, 土壤碳矿化速率减弱。

关键词: 土壤胞外酶, 潜在碳矿化速率, 季节动态, 森林类型, 地被植物