珀氏长吻松鼠和赤腹松鼠在保护区与非保护区各年龄松林内的种群动态

2004年6~7月,在云南省大理白族自治州苍山和洱海国家自然保护区选取4种年龄段(6~10、11~15、16~20、31~40年)的松林和保护区周围的非保护区选取7种年龄段(1~5、6~10、11~15、16~20、21~30、31~40、50年以上)的松林,每种松林设3个重复,共33个样地,在样地内随机选取3个5m×5m的样方,调查并记录样方内草本植物和灌木的种类、数量、覆盖度。在每个样地按5条样线布笼100个捕捉小兽,每天检查捕获的种类和数量。计算珀氏长吻松鼠和赤腹松鼠在小兽群落中物种优势度、时间生态位宽度、两种小兽的时间生态位重叠度;用逐步回归分析两种松鼠与松林栖境因子的关系。上述结果表明,在保护区珀氏长吻松鼠出现的时间早于(6~10年的松林开始捕获到)赤腹松鼠(16~20年的松林内开始捕获到);在非保护区,分别在31~40年和21~30年的松林内才捕到珀氏长吻松鼠和赤腹松鼠。保护区31~40年的松林内珀氏长吻松鼠和赤腹松鼠种群数量分别是同年龄段非保护区松林的3倍和3·75倍。松林底层的灌木对两种小兽的种群数量有重要影响。珀氏长吻松鼠种群数量与灌木密度呈正相关;赤腹松鼠种群数量与灌木覆盖度呈正相关,而与草本植物覆盖度呈负相关。非保护区树底植被的异质性降低,延迟了两种松鼠在松林里建立种群的时间。

Population Dynamics of Dremomys pernyi and Callosciurus erythraeus in the Protective and Non-protective Pine Forests at Different Ages

Four pine forests (6-10, 11-15, 16-20 and 31-40 year-old) located in the Cangshan Mountain and Erhai Lake National Reserve and seven pine forests (1-5, 6-10, 11-15, 16-20, 21-30, 31-40 and more than 50 year-old) located in the non-protective area near the national reserve were selected. Three replications of each forest was set and a total of 33 sites were investigated. At each site, we quantified six habitat variables (species richness, abundance and percentage of grasses and shrubs coverage respectively at the bottom layer of forests) within randomly determined 5 m×5 m areas. One hundred cages were set in five lines at each site to trap small mammals, whose species and numbers were recorded. Dominance of Dremomys pernyi and Callosciurus erythraeus in small mammal communities, time niche breadth and time niche overlap between the two small mammals were calculated respectively. Step-wise regression was used to analyze relationship between small mammals and habitat factors. Our results indicated that D. pernyi occurred earlier than C. erythraeus in protective pine forests. D. pernyi was captured in 6-10 year-old forest initially, and C. erythraeus was captured in 16-20 year-old forest initially. D. pernyi and C. erythraeus were captured in the 31-40 and 21-30 year-old forests initially in the non-protective area, respectively. Populations of D. pernyi and C. erythraeus in the 31-40 year-old protective forests were 3 and 3.75 times of those in the same-aged non-protective forests, respectively. Shrubs significantly influenced populations of the two small mammals. Populations of Dremomys pernyi was positively correlated with density of shrubs; populations of C. erythraeus was positively correlated with coverage of shrubs, and negatively correlated with coverage of grasses. D. pernyi and C. erythraeus were important for pine forests to scatter pine seeds. Human activities in the non-protective pine forests decreased the vegetation heterogeneity at the bottom layer of pine forests, postponed the occurrence of D. pernyi and C. erythraeus, and decreased populations of the two small mammals.