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(1-5,6-10,11-15,1620,21-30,31-40,and more than 50 year-old)located in the non-pr...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(1-5,6-10,11-15,1620,21-30,31-40,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 mx5 m areas.One hundred cages were set in five lines at each site to trap small mammals,whose species and numbers were recorded.Domi-nance of Dremomys pernyi and Callosciurus erythraeus in small mammal communities,time niche breadth,and time niche overlap between the two small mammals were calcu-lated,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 same-aged 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.展开更多
Seed dispersal by exotic mammals exemplifies mutualistic interactions that can modify the habitat by facilitating the establishment of certain species. We examined the potential for endozoochoric dispersal of exotic p...Seed dispersal by exotic mammals exemplifies mutualistic interactions that can modify the habitat by facilitating the establishment of certain species. We examined the potential for endozoochoric dispersal of exotic plants by Callosciurus erythraeus introduced in the Pampas Region of Argentina. We identified and characterized entire and damaged seeds found in squirrel faeces and evaluated the germination capacity and viability of entire seeds in laboratory assays. We collected 120 samples of squirrel faeces that contained 883 pellets in seasonal surveys conducted between July 2011 and June 2012 at 3 study sites within the main invasion focus of C. erythraeus in Argentina. We found 226 entire seeds in 21% of the samples belonging to 4 species of exotic trees and shrubs. Germination in laboratory assays was recorded for Morus alba and Casuarina sp.; however, germination percentage and rate was higher for seeds obtained from the fruits than for seeds obtained from the faeces. The largest size of entire seeds found in the faeces was 4.2 ~ 4.0 ram, whereas the damaged seeds had at least 1 dimension ≥ 4.7 ram. Our results indi- cated that C. erythraeus can disperse viable seeds of at least 2 species of exotic trees. C. erythraeus predated seeds of other naturalized species in the region. The morphometric description suggested a restriction on the maximum size for the passage of entire seeds through the digestive tract of squirrels, which provides useful information to predict its role as a potential disperser or predator of other species in other invaded communities.展开更多
文摘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(1-5,6-10,11-15,1620,21-30,31-40,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 mx5 m areas.One hundred cages were set in five lines at each site to trap small mammals,whose species and numbers were recorded.Domi-nance of Dremomys pernyi and Callosciurus erythraeus in small mammal communities,time niche breadth,and time niche overlap between the two small mammals were calcu-lated,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 same-aged 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.
文摘Seed dispersal by exotic mammals exemplifies mutualistic interactions that can modify the habitat by facilitating the establishment of certain species. We examined the potential for endozoochoric dispersal of exotic plants by Callosciurus erythraeus introduced in the Pampas Region of Argentina. We identified and characterized entire and damaged seeds found in squirrel faeces and evaluated the germination capacity and viability of entire seeds in laboratory assays. We collected 120 samples of squirrel faeces that contained 883 pellets in seasonal surveys conducted between July 2011 and June 2012 at 3 study sites within the main invasion focus of C. erythraeus in Argentina. We found 226 entire seeds in 21% of the samples belonging to 4 species of exotic trees and shrubs. Germination in laboratory assays was recorded for Morus alba and Casuarina sp.; however, germination percentage and rate was higher for seeds obtained from the fruits than for seeds obtained from the faeces. The largest size of entire seeds found in the faeces was 4.2 ~ 4.0 ram, whereas the damaged seeds had at least 1 dimension ≥ 4.7 ram. Our results indi- cated that C. erythraeus can disperse viable seeds of at least 2 species of exotic trees. C. erythraeus predated seeds of other naturalized species in the region. The morphometric description suggested a restriction on the maximum size for the passage of entire seeds through the digestive tract of squirrels, which provides useful information to predict its role as a potential disperser or predator of other species in other invaded communities.
