| The squirrels Sciurus vulgaris have a relatively large size,diurnal nature,long life expectancy and entirely counting on the storage of Korean pine seeds through the harsh winter.They are better suited to detailed ecological research than other rodents.Korean pine Pinus koraiensis,because of the seeds trait,its natural spread and renewal have almost absolutely dependent on animals,Korean pine and squirrel formed a closely coevolutionary relationship.In the recent years,the Korean pine is gradually reduced due to reasons such as the cutting,artificial afforestation has not affect on the forest recovery.Together,the study of squirrel population is of great significance to the recovery and rational utilization of Korean pine forest.Changbai Mountain national nature reserve is one of the earliest and the most important nature reserve in our country.Broad-leaved Korean pine mixed forest in this reserve is one of the most extensive original Broad-leaved Korean pine mixed forest remain in the world.Compared with Europe and America region in the same latitude,it is famous for complex structure,special composition,and plentiful biological diversity.However,the particular study on squirrel population in the national nature reserve of Changbai Mountain has not been reported yet.In this study,we studied the seasonal and annual changes and habitat differences of squirrel populations in the North Slope of Changbai Mountain national reserve.(1)The Improvement of traps for Capture-mark-recapture on squirrelInfrared camera and hidden observation found that chipmunk Tamias sibiricus interference(squirrel because of small volume,can freely in and out of the traps)and squirrels tentatively for(before entering the traps,outside the traps looking for bait channels,climbing every capture metal mesh cage grab bait)was led to the capture failure.According to the characteristics of feeding behavior of squirrel and chipmunk(rats are usually on the ground,climbing up to obtain food;Squirrel canopy activities,from top to bottom near the traps),the barriers and bait protection were used to improve the squirrel capture rate in our study.Compared the traditional method and the improved method,the results found that in 6 days,each grouping test total layout traps 180 times in the compared experiment,the control group didn't capture the squirrels in the traditional way,only put the bait protection captured one squirrel,did not significantly increase the capture of the squirrel number(x2=1.003,df=1,P>0.05).By adding the barriers alone,the squirrels were captured 6 times,significantly increasing the number of capture squirrels(x2=6.102,df=1 P>0.05).Arranged the baits protection and the barriers together,and the number of captured squirrels was up to 35 times,significantly increased the capture quantity(x2=23.149,df=1,P<0.01).The above results show that put the baits protection and the barriers together is the most effective way to improve the capture rate of the squirrels.(2)Squirrel population season change and annual difference survey Using the improved squirrel capture method,the squirrel population in the North Slope of the Changbai Mountain national nature reserve was investigated in the spring(may),summer(July)and autumn(September)of 2012 to 2013 which in one year after pine seed production big year(2011)and small year(2012).The results showed that the overall ratio of females to females was 42:46,and the difference was not significant(x2=0.182,df=1,p>0.05).There was no significant difference between the female reproductive rate in 2013 and 2012(x2=0.307,df=1,p>0.05).In spring 2012,the squirrel had lower weight,and the weight difference was not obvious in other seasons.In addition,the weight difference was not obvious in 2013.The squirrel population was significantly different in 2012(x2=15.086,df=2,P<0.05).It was the lowest in spring,summer growth,and fell back in the autumn.2013 population has no significant seasonal difference(x2=1.980,df=2,P>0.05).The squirrel population quantity in 2013 was significantly lower than in 2012(x2=108.435,df=1,P<0.01).The density of the squirrels in each capture period was 17.707±1.17/km2 in spring,28.308±1.897/km2 in summer,and 17.323±1.025/km2 in autumn of 2012;5.406± 1.563/km2 in the spring,6±1.542/km2 in summer,and 8.00±0.00/km2 in autumn of 2013.(3)The effect of different interference and diverse forest type on squirrel population.Four different habitats were classified according to forest type and disturbance type.1.Natural regeneration of birch forest after fire,2.Original Korean pine,spruce,and fir forest,3.Original broad-leaved Korean pine mixed forest in the core area 4.Broad-leaved Korean pine mixed forest in the experimental area.The comparison results of squirrel population in summer 2012 showed that the original broad-leaved Korean pine mixed forest in the core area was extremely significant(x2=25.095,df=1,P<0.01)higher than the original Korean pine,spruce and fir forest.The fire interference was extremely significantly(x2=547.000.df=1,P<0.01)reduced the number of squirrel population,and the number of squirrel population was extremely significantly reduced by pick pinecone(x2=57.748,df=1,P<0.01).We captured zero squirrels in the natural regeneration of birch forest after fire and the broad-leaved Korean pine forest in the experimental area.The squirrel population density was 6.00±0.470/km2 in the original Korean pine,spruce and fir forest,and 28.308±1.897/km2 in the original broad-leaved Korean pine forest in the core area.In the autumn of 2012,the comparison results showed that the squirrel population of the original broad leaves Korean pine forest in the core area was significantly higher(x2=4.768CU.df?1,P<0.05)than the original Korean pine,cloud fir,and fir forest.The fire interference was extremely significantly(x2=381.000,df=1,P<0.01)reduced the squirrel population,and the number of squirrel population was extremely significantly reduced by pick pinecone(x2=70.674,df=1,P<0.01).We captured zero squirrels in natural regeneration of birch forest after fire,and one squirrel in the broad-leaved Korean pine forest in the experimental area.The squirrel population density was 11.3±0.976/km2 in the original Korean pine,spruce and fir forest,and 15.3±0.91/km2 in the original broad-leaved Korean pine forest in the core area.In autumn and summer,the effects of forest type and disturbance on the number of squirrels showed similar regularity.We conclude that the squirrel density fluctuates with the seed yield of Korean pine,one-year delay.The population is the lowest before reproduction in spring,the population is increased in summer and the population distribution tends to be more uniform in autumn.The number of availability seeds,berries and leaf bud foods are likely to be the key factors that restrict the squirrel populations in different habitats.The human activities such as fire interference,logging and picking pinecone which influence the above factors will decrease the squirrel population. |
PDF Full Text Request