【作者】 余胜；

【导师】 杨万勤； 吴福忠；

【作者基本信息】 四川农业大学 ， 森林培育， 2010， 硕士

【摘要】 季节性冻融是全球中高纬度和高海拔地区普遍存在的自然现象。受季节性雪被和冻融循环影响明显的区域生态系统过程明显存在四个关键时期(土壤冻融期、土壤冻结期、土壤融冻期和生长季节),但已有的研究更加关注生长季节内发生的生态学过程。作为土壤生物化学过程的积极参与者和生态系统的重要组成部分,土壤酶在很大程度上控制着森林生态系统的生物元素循环,但已有的研究更加关注生长季节矿质土壤层的酶活性动态,而有关非生长季节内3个关键时期的土壤酶活性动态以及土壤有机层的酶活性动态研究还相当少见,这制约了我们对高寒生态系统过程的理解。地处青藏高原东缘和长江上游地区的川西亚高山和高山森林在生物多样性保育、水源涵养、水土保持、指示全球气候变化等方面具有十分重要且不可替代的作用和地位,也是受季节性雪被和冻融循环影响十分明显的中纬度高海拔地区。因此,本研究以川西亚高山和高山地区分布面积最大和范围最广的原始冷杉林(Abies faxoniana)、针阔混交林(A. faxoniana, Betula albosinensis)和次生冷杉林为研究对象,通过动态取样、室内实验测试和分析相结合,同步研究了四个关键时期,土壤有机层和矿质土壤层中与C、N、P循环相关的转化酶、脲酶、酸性磷酸酶、中性磷酸酶、碱性磷酸酶、过氧化物酶、过氧化氢酶和脱氢酶活性动态。研究结果表明：3个森林群落土壤有机层水解酶和氧化还原酶活性均显著高于矿质土壤层相应的酶活性。在受冻融循环影响频繁的初冻期和融冻期,各种水解酶和氧化还原酶活性均发生显著变化,并且土壤有机层比矿质土壤层更加敏感,而在土壤深冻期,均无显著变化。3个森林群落土壤有机层中转化酶活性在初冻期、融冻期后期、生长季节初期和生长季节末期均显著降低,在融冻初期和生长季节中期均显著升高,在冻结期变化不显著。矿质土壤层中转化酶活性在融冻初期和生长季节均显著升高,在融冻期后期均显著降低,在冻结期无显著变化。3个森林群落土壤有机层中脲酶活性在初冻期、融冻初期和融冻后期均显著升高,在融冻中期均显著降低,在冻结期均无显著变化。矿质土壤层中脲酶活性在融冻初期和融冻末期均显著升高,在融冻中期和生长季节初期均显著降低,在冻结期均无显著变化。3个森林群落土壤有机层中酸性磷酸酶活性在初冻期、融冻初期、融冻末期和生长季节初期均显著升高,在融冻中期和生长季节后期均显著降低,在冻结期无显著变化。矿质土壤层中酸性磷酸酶活性在初冻期、融冻初期和生长季节初期均显著升高,在融冻中期均显著降低,在冻结期均无显著变化。3个森林群落土壤有机层中中性磷酸酶活性在初冻期、融冻中期和融冻末期均显著升高,在融冻初期和融冻后期均显著降低,在冻结期均无显著变化。矿质土壤层中中性磷酸酶活性在初冻期显著升高,在融冻初期和融冻中期均显著降低,在冻结期均无显著变化。3个森林群落土壤有机层和矿质土壤层中碱性磷酸酶活性在融冻初期和生长季节初期均显著升高,在融冻中期和生长季节后期均显著降低,在冻结期均无显著变化。3个森林群落土壤有机层中过氧化物酶活性在初冻期和生长季节期均显著降低,在融冻初期和融冻后期均显著升高,在冻结期无显著变化。矿质土壤层中氧化物酶活性在初冻期、融冻中期和生长季节期均显著降低,在融冻初期和融冻末期均显著升高,在冻结期无显著变化。3个森林群落土壤有机层中过氧化氢酶活性在初冻期、融冻初期、融冻后期和生长季节前期均显著升高,在融冻中期和生长季节后期均显著降低,在冻结期无显著变化。矿质土壤层中氧化氢酶活性在初冻期和融冻初期均显著升高,在融冻中期显著降低,在冻结期无显著变化。3个森林群落土壤有机层中脱氢酶活性在初冻期、融冻中期、融冻末期和生长季节后期均显著降低,在融冻初期和生长季节初期均显著升高,在冻结期无显著变化。矿质土壤层中脱氢酶活性在初冻期均显著降低,在融冻初期均显著升高,在冻结期无显著变化。更多还原

【Abstract】 Seasonal freezing and thawing event is a common natural phenomenon in the middle-high latitudes and high elevation area. The ecosystem process has four critical periods including early freezing period, freezing period, soil thawing period, and growing period in these regions which are strongly subjected to seasonal snow cover and freeze-thaw cycles. However, more attentions have been given to the ecological process in the growing season. As an active participant in soil biochemical process and important component in soil ecosystem, soil enzymes play an important role in regulating ecosystem bioelement cycles to an extent. As yet, more attentions have concerned about the dynamics of the activities of enzymes in mineral soil during the growing season, and little information are. available on the changes in enzyme activities in both mineral soil layer and soil organic layer during other critical periods, which limits our understanding of the process in the high-frigid ecosystem. The subalpine and alpine forest in western Sichuan located in the eastern Tibet plateau and the upper reaches of Yangtze River is a middle-latitude and high-elevation region subjected to clear snow cover and frequent freeze-thaw cycles, and plays important and irreplaceable roles in nursing biodiversity, holding water, conserving soil, and indicating global climate change. In order to deeply understand the effects of season freezing and thawing on soil biochemical process in the high-frigid forest ecosystem, therefore, the activities of invertase, urease, acid phosphatase, neutral phosphatase, alkaline phosphatase, peroxidase, catalase and dehydrogenase, which are related with the cycles of carbon, nitrogen and phosphorus in both mineral soil layer and soil organic layer were simultaneously measured in primary fir (Abies faxoniana) forest, fir and birch (Betula albosinensis) mixed forest and secondary fir forest which are three representative forests in the study region, employing the method of field sampling in combination with laboratory analysis in four critical periods.The activities of the studied enzymes in soil organic layer were significantly higher than those in mineral soil layer regardless of the forest and sampling time. The changes of enzyme activities in both organic layer and mineral soil were more significant during early freezing period and soil thawing period which were frequently subject to freeze-thaw cycles in comparison with other periods. The activities of enzymes in soil organic layer were more sensitive to environmental change than those in mineral soil layer. However, little changes were found in deep soil freezing period.The invertase activity in the three sampling forests of soil organic layer shown significant decreased during early freezing period, late soil thawing period, early growing period and late growing period, and shown significant increased during early soil thawing period and middle growing period. Which of mineral soil layer shown significant decreased during late soil thawing period, and shown significant increased during early soil thawing and growing period. However, which shown little change during freezing period of both soil organic layer and mineral soil layer.The urease activity in the three sampling forests of soil organic layer shown significant increased during early freezing period, early soil thawing period and late soil thawing period, and shown significant decreased during middle soil thawing period. Which of mineral soil layer shown significant increased during early soil thawing period and late soil thawing period, and shown significant decreased during middle soil thawing and early growing period. However, which shown little change during freezing period of both soil organic layer and mineral soil layer.The acid phosphatase activity in the three sampling forests of soil organic layer shown significant increased during early freezing period, early soil thawing period, late soil thawing period and early growing period, and shown significant decreased during middle soil thawing period and late growing period. Which of mineral soil layer shown significant increased during early freezing period, early soil thawing period and early growing period, and shown significant decreased during middle soil thawing period. However, which shown little change during freezing period of both soil organic layer and mineral soil layer.The neutral phosphatase activity in the three sampling forests of soil organic layer shown significant increased during early freezing period, middle soil thawing period and late soil thawing period, and shown significant decreased during early soil thawing period and late soil thawing period. Which of mineral soil layer shown significant increased during early freezing period, and shown significant decreased during early soil thawing period and middle soil thawing period. However, which shown little change during freezing period of both soil organic layer and mineral soil layer.The alkaline phosphatase in the three sampling forests of both soil organic layer and mineral soil layer shown significant increased during early soil thawing period and early growing period, and shown significant decreased during middle soil thawing period and late growing period. However, which shown little change during freezing period.The peroxidase activity in the three sampling forests of soil organic layer shown significant decreased during early freezing period and growing period, and shown significant increased during early soil thawing period and late soil thawing period. Which of mineral soil layer shown significant decreased during early freezing period, middle soil thawing period and growing period, and shown significant increased during early soil thawing period and late soil thawing. However, which shown little change during freezing period of both soil organic layer and mineral soil layer.The catalase activity in the three sampling forests of soil organic layer shown significant increased during early freezing period, early growing period, late growing period and early growing period, and shown significant decreased during middle soil thawing period and late growing period. Which of mineral soil layer shown significant increased during early freezing period and early soil thawing period, and shown significant decreased during middle soil thawing period. However, which shown little change during freezing period of both soil organic layer and mineral soil layer.The dehydrogenase activity in the three sampling forests of soil organic layer shown significant decreased during early freezing period, middle soil thawing period, late soil thawing period and late growing period, and shown significant increased during early soil thawing period and early growing period. Which of mineral soil layer shown significant decreased during early freezing period, and shown significant increased during early soil thawing period. However, which shown little change during freezing period of both soil organic layer and mineral soil layer.更多还原