Structure Processes And Determinants Of Bird Community In The Secondary Broadleaf Forest

Secondary forest is one phase of plant community during succession, is a common type of forest when original forests being deforested. Study on determinant factors and structuring process of bird communities in such types of forests would be helpful to discuss the mechanism of community structure and configuration process.We developed a study on determining and stracturing processes of bird community in the Secondary broadleaf forest within a same habitat and scale to post the mechanism of the determining and stracturing processes of bird community in temperate secondary broadleaf forest. Our main finding as follows:1. The study on the mechanism of bird community formation in a secondary broadleaf forest with an area of 39.8hm~2 found that the formation and stabilization of bird community relys on‘Key group’. We defined the key group as species that can influence the formation and patterns of a community. There are two key groups in bird community of secondary forest, one is primary cavity-nesting birds, the other is Magpie.2. We adopted the methods of adding nest boxes in experimental plots, and by comparing with control plots to discuss the structuring process and stabilization of cavity-nesting bird communities. Our results showed that the resource of natural cavity as nest-site was stable, and no significant difference of the utilization rate of natural cavities in experimental and control plots was detected, which indicated that the cavity-nesting bird communities in secondary broadleaf forests were stable.3. We studied the determinating and structuring process of breeding bird communities of secondary broadleaf forest in a same habitat and scale for 20 years. We found that the traits and mechanism of determinating process, structuring process and stochastic process of breeding bird communities were as follows:1) The structuring process and characteristics of breeding bird communities in secondary broadleaf forests (1) The species abundance of bird communities ranged from 20 to 30 in temperate secondary broadleaf forests with trees varied from 60 to 70 years old. The number of bird individuals ranged from 132 to 250. Therefore, the thresholds for the bird species abundance and number of individuals in temperate secondary broadleaf forests with tree ages over 60 years was 36 species and 250 individuals respectively. The structuring process can be divided into three periods: the bird species remained no change for 9 years from 1987 to 1996, ranged from 22 to 22 species; the abundance of bird species ranged from 24 to 32 during 1997 to 2001; the abundance of bird species ranged from 29 to 36 during 2002 to 2006.(2)“constructive species”playing important role during bird community formation Sixteen breeding bird species wre recorded annually during the 20-year study, which accounted for 40.0% of all breeding species, and they were the mainbody in structuring bird communities. The total number was 2590 individuals, and the consume biomass accounted for 51.2% of total.(3) Key groups playing important role during bird community formation key groups included Magpie and primary cvity-nesting birds, they provide nest-sites for 7 bird species.(4) The structuring process of bird communities is a stochastic process of successionNew bird communities will occur following the vegetation succession, and the structuring process of bird communities is a evolutive process, at the same time, the structuring process of bird communities is a stochastic process of bird species intruded and seceded.Birds species will change following the change of important value of dominant tree species. Species prefer to nest in forests with older trees appeared when tree age increased, such as Ring-necked Pheasant, Hazel Grouse. Oder trees also provided nest-site resurces for primary cavity-nesting bird, secondary cavity-nesting birds and other bigger birds. Species prefer to nest in forests with dense shrubs appeared when shrubs under arbors, such as Japanese Bush Warbler, Fantail Snipe, Red-tailed Shrike.2) The mechanism of mataining bird communities is the integrative process of determining process and stochastic process(1) The determining process is①the rationality of spital structure fo bird community;②exiting constructive species in bird community;③cavity-nesting bird communities were constructured continuously during structuring process of community ;④exiting key groups during structuring process of community.(2) The stochastic process is①bird communities changed with change of vegetation;②breeding birds intruded and seceded;③bird dominated by species suffered little effects of climate changes.4. The studies on the relationships between population trends of 18 bird species and climate changes (air temperature and rainfall) for 20 years foud that the changes of climate posed little on population size, that is, the air temperature and rainfall were not the main factors in shading poplation size of birds. The possible reason is that 14 out of 18 bird species are cavity-nesting and Magpie’s nest nesting birds.5. We predicated the population trends of 26 bird species during future 10 years in a plot with an area of 39.8hm~2 in temperate secondary broadleaf forests by using NN method. Our results indicated that the abundance and number of the 26 bird species will change during the future 10 yeas. Bird communities will consist of 25 bird species during 2007-2016, the total number would be 1898 individuals, and the Ashy Starling will recoil from the plot after 2012, the number of Grey-headed Woodpecker would range from 8 to 12 individuals, the number of Greater Pied Woodpecker would range from 8 to 16 individuals and the number of Nuthatch would range from 12 to 22 individuals. The increasing and fluctuating curve of those birds would be similar, the process of population size increasing and decreasing would be stable.