小兴安岭林区不同生境梯度中小型哺乳动物生物多样性

Studies on bio-diversity of small mammals along different habitat gradients in the Xiao Xing'an Ling Forest Region, China

利用铗日法和陷阱法 ,于 2 0 0 0年 7～ 8月 ,对小兴安岭林区 7个不同生境梯度中小型哺乳动物群落的多样性变化进行了初步研究。结果表明 :( 1 )铗日法所捕获的物种数和个体数明显大于陷阱法 ,但后者更适合捕获小体型动物 ;( 2 )共捕获小型哺乳动物 9种 ,其中啮齿目 ( Rodentia)松鼠科 ( Sciuridae) 1种 ,田鼠亚科( Microtine) 3种 ,鼠科 ( Muridae) 4种 ,食虫目 ( Insectivora)科 ( Soricidae) 1种 ,所捕获的物种中 ,棕背( Clethrionomysrufocanus)为优势种 ,占总数的 48.77% ,与黑线姬鼠 ( Apodemus agrarius)、大林姬鼠 ( A.speciosus)和红背 ( C.rutilus)一起构成本地区的常见种 ;( 3)物种在不同的生境类型中呈明显的不均匀分布 ,以中度干扰的灌丛生境内小型哺乳动物从物种丰富度和多样性指数最高 ,次生林 1和农田生境均有较高的物种丰富度和多样性指数 ,无干扰的原生林 1、2中物种丰富度最低 ,而轻微干扰的原生林 3中物种多样性指数最低 ,受严重干扰的农田生境中小型哺乳动物均匀度最高 ,其次是次生林 1和灌丛 ,原生林 3和干扰较重的次生林 2中小型哺乳动物群落均匀度最小 ;( 4 )从物种多样性与林地郁闭度和地表草本植物覆盖度的相关分析看出 :物种多样性与郁闭度相关性不显著 。

Small mammals are of crucial importance to boreal forest ecosystem because they constitute staple food for many mammalian and avian predators and they consume plants, lichens, fungi and invertebrates. In addition, they also help plants to disperse their seeds. However, small mammals have also been shown to be more susceptible to local extinction in fragmentated habitats. The composition of small mammals in many vegetation types in Northeast Forest Regions of China is incompletely known. We also do not know what effect habitat changes caused by logging and cultivationg have on small mammal communities. We investigated the species distribution and abundance of small mammals and used them as indicators for monitoring environmental changes, and to explore how these changes would affect spatial distribution patterns and local biodiversity in a more general sense. The study was conducted in Fenglin Nature Reserve and its surrounding regions (E128°59′~129°15′,N48°01′~48°09′), which is located in the middle of Xiao Xing'an Ling forest region, in northeast China. Small mammals were trapped using snap traps and pitfalls trapping from July to August 2000 at seven sites along different habitat gradients. Two grids were established at each site, with ≥100 m between the two grids. Each grid consisted of 50 snap traps and 20 pitfalls. Snap traps were set in two parallel lines 20 m apart with 25 snap traps (5 m apart) along each line. The 20 pitfalls (5 m apart) were set between the two parallel lines of snap traps. Trapping was carried out for 4 consecutive days at each site. In total, 326 individuals were captured, comprising 1 species of shrew and 8 species of rodents. Of these, Clethrionomys rufocanus (49%) was the most commonly trapped species in this region. Apodemus agrarius, A.speciosus, C. rutilus each accounted for 10%~12% of total individuals. Rattus norvegicus only accounted for 2.1% of total individuals and was the rarest species. The captured species were not evenly distributed along the habitat gradients. Analyses of diversity of small mammals in different habitats showed that species richness and diversity index ( H ′) were highest in shrub habitats, where human disturbance has been moderate in recent years. They were also high in two secondary forests and farmland. Species richness in primary forest 1 and primary forest 2 , where were not disturbed, were the lowest, and the diversity index ( H ′) was lowest in primary forest 3, which has been disturbed lightly by human. Evenness was highest in farmland, although the human disturbance is most serious there. Evenness in the secondary forest 1 and shrub habitats ranked next, and evenness was lowest in primary forest 3 and secondary forest 2, where were seriously disturbed by mowing. Analysis of correlationof species diversity index ( H ′) and tree canopy density/vegetation coverage demonstrated a significant positive correlationof species diversity index ( H ′) with vegetation coverage but not with tree canopy density. Based on similarity indices, seven habitats can be clustered at the level of 0.0631 with systematic clustering. When a threshold of 0.6 for the similarity index was considered, the seven habitats could be categorized into three groups: (1)primary forests habitats, (2) secondary forest habitats, and (3) shrub and farmland. We conclude that, in Xiao Xing'an Ling forest region, in northeast China, the distribution and abundance of small mammals are influenced to a great extent by structural habitat factors such as stage of vegetation succession, food, and ground cover. In addition, human activity is one of the main factors affecting species diversity of small mammals in the region.