温带次生林的岛屿化对鸟类物种多样性及密度的影响

由于自然事件的影响和人类活动的干扰,越来越多的大片森林破碎成彼此孤立、面积不一的森林岛屿,这种变化无疑会对某些动物的分布模式及行为特征产生影响。于2000和2001年的春夏季,在吉林省左家自然保护区及土门岭地区,采用点样法对18块森林岛屿(面积范围:4.3–76.9hm2)中的鸟类物种多样性及密度进行了调查。主要目的是检测森林岛屿的面积效应是否对鸟类物种多样性及密度产生影响,同时分析经典的岛屿生物地理理论是否可以解释破碎化后的森林岛屿面积与物种的关系。结果表明,鸟类物种多样性在年间没有显著变化,但鸟类的密度在不同年间变化较大。不同面积森林岛屿中的鸟类物种多样性有所差异,所包含的鸟类物种数从12种到43种不等。尽管有些面积较大的斑块所包含的物种数较少,但鸟类物种数的总体趋势是随着斑块面积的增大而增多。不同鸟类对森林岛屿面积的反应并不相同,灰椋鸟(Sturnuscineraceus)、红尾伯劳(Laniuscristatus)、灰头鹀(Embrizaspodocephala)等在面积较小的斑块中密度较大,而山鹡鸰(Dendronanthusindicus)、树鹨(Anthushodg-soni)、灰背鸫(Turdushortulorum)等几乎不分布于小面积斑块之中。森林岛屿中鸟类物种随着面积变化的变异方式符合经典的岛屿生物地理理论的基本模式,但Z值和C值差异较大

The effects of forest patch sizes on bird species diversity and individual density

More and more continuous forests become fragmented because of natural events and human dis- turbance. This change will affect the distribution patterns and behavior characteristics of animals living in forests. Using point count methods, we investigated bird species diversity and individual density in 18 forest fragments (area: 4.3 to 76.9 hm2) in Zuojia Nature Reserve, Jilin Province during the spring and summer of 2000 and 2001. The main objectives of this research were to assess whether there exist area effects affecting bird species diversity and individual density in a fragmented forest. There was no significant difference of indices of bird diversity between the two years. However, the individual density of birds differed signifi- cantly in the two years. Our results also indicated that there were significant differences in bird diversity among forest patches, with the number of bird species ranging from 12 to 43. Although several large forest patches contained relatively fewer bird species, the bird species tended to increase with size of forest patch. Different bird species respond to forest patch size differently. White-checked starling (Sturnus cineraceus), brown shrike (Lanius cristatus) and black-faced bunting (Embriza spodocephala) preferred small patches, whereas forest wagtail (Dendronanthus indicus), olive-backed pipit (Anthus hodgsoni) and grey-backed thrush (Turdus hortulorum) rarely occurred in small patches. Basically, the relationship between area size and species number was in accordance with the classical theory of island biogeography, but the Z and C values were very different from those predicted. We found a threshold phenomenon in the relationship between patch area and number of bird species such that the number of bird species did not change significantly when the patch size was greater than 30 hm2. Thus, it is not suitable to use the classical theory of island biogeog- raphy directly to predict species diversity or for designing nature reserves for a fragmented forest landscapes.