Population dynamics of Dremomys pernyi and Callosciurus erythraeus in protective and non-protective pine forests at different ages

Abstract

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 7 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 6 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 the 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 sameaged non-protective forests, respectively. Shrubs significantly influenced the populations of the two small mammals. The population of D. pernyi was positively correlated with the density of shrubs; the population of C. allosciurus erythraeus was positively correlated with the coverage of shrubs, and negatively correlated with the coverage of grasses. D. remomys pernyi and C. allosciurus 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 the populations of the two small mammals.