Community Structure and Diversity Distributions of Small Mammals in Different Sample Plots in the Eastern Part of Wuling Mountains

Five years＇ （2000-2004） continuous study has been carried out on small mammals such as rodents in seven different sample plots, at three different altitudes and in six different ecological environment types in the eastern part of the Wuling Mountains, south bank of the Three Gorges of Yangtze River in Hubei. A total of 29 297 rat clamps/times were placed and 2271 small mammals such as rodents were captured, and 26 small mammals were captured by other means. All the small mammals captured belonged to 8 families 19 genera and 24 species, of which rodentia accounted for 70.83% and insectivora 29.17%. Through analysis of the data, the results showed that： 1 ） although the species richness had a trend of increasing along different sample plots as altitude increased from south to north, quite a few species showed a wide habitat range in a vertical distribution （ 15 species were dispersed over three zones and two species over two zones） , indicating a strong adaptability of small mammals such as rOdents at lower altitudes in most areas and comparatively less vertical span of entire mountains; 2） whether in seven different sample plots or six different ecological types, Apodemus agrarius and Rattus norvegicus were dominant species below 1200m, and Anourosorex squamipes, Niviventer confucianus and Apodemus draco were dominant above altitudes of 1300m, however, in quantity they were short of identical regularity, meaning they did not increase as the altitude did, or decrease as the ecological areas changed; 3）the density in winter was obviously greater than that in spring, and the distribution showed an increasing trend along with altitude, but the density in different sample plots was short of identical regularity, showing changes in different seasons and altitude grades had an important impact on small mammals such as rodents; 4） in species diversity and evenness index, there were obvious changes between the seven different sample plots, probably caused by frequent human interference in this area. Comparatively speaking, there was less human interference at high altitudes where vegetation was rich and had a high diversity and evenness index, and the boundary effect and community stability were obvious. Most ecological types have been seriously interfered with due to excessive assart at low altitudes with singular vegetation and low diversity and evenness index and poor community stability, showing an ecosystem with poor anti-reversion. If human interference can be reduced in those communities at high altitudes with low diversity and evenness index, the biological diversity in the communities will gradually recover to similar levels of other ecological areas.

Influence of Human Disturbance to the Small Mammal Communities in the Forests

Small mammals have been proposed playing an important role in the energy flow and regeneration of forest ecosystems. We compared species richness, diversity (H’) of small mammal communities and abundance of six dominant species of small mammals in disturbed and protected forests (four age classes: 6 - 10, 11 - 15, 16 - 20 and 31 - 40 years old) in China. We also investigated the structural variables (such as species richness, cover rate and abundance of shrubs and grasses) in the bottom layer, which considered to be important for small mammals and might be altered by human disturbance. The relationships between small mammals and these structural variables were examined to determine the potential effects of human disturbance on the small mammals in the restored forests. Our results indicated that the structure and composition of the vegetation in the bottom layer were simplified by human disturbance, while the abundance and cover rate of grasses were significantly increased. Although no significant differences were observed in species richness of small mammals between the protected and disturbed forests at the same age, the diversity index of small mammals in the protected forests was always significantly higher than in the disturbed forests. Regression showed that the species richness and diversity of small mammals increased with the species richness of shrubs, and was negatively correlated to the cover rate of grasses in the bottom layer. Human disturbance increased the total abundance of small mammals, and the increased cover rate of grasses in the bottom layer was beneficial to the abundance of small mammals. Obvious succession of small mammal communities occurred as the protected forest aged. In the protected forests, small ground-dwelling mammals (A. chevrieri, E. miletus and M. pahari) were the dominant species in the younger forests. Other mammals (T. belangeri, D. pernyi and C. erythraeus) gradually became the dominant species as the protected forests aged. However, in the disturbed forests, the smaller ground-dwelling mammals (T. belangeri, D. pernyi and C. erythraeus) were always the dominant species at all ages of the disturbed forests. Regression indicated that the cover rate of grasses in the bottom layer was beneficial to the three smaller body size and ground-dwelling small mammal species, while the shrubs were beneficial to the three bigger body size mammal species.

人类活动对云南哀牢山小型兽类群落结构的影响

本文涉及云南景东哀牢山徐家坝森林地区,不同强度人类活动对小兽群落结构的影响。结果表明:1.在原生常绿阔叶林中小鲁16种,数量9.81％,中华姬鼠和中华鼩猬为优势种;在原生林遭砍伐而演替为次生林内6种;数量1.18％;中华姬鼠和社鼠占优;在原生林遭严重破坏所形成的毛蕨草地上5种,数量0.92％,巢鼠为优势种。2.上述3种栖息地中小兽密度依次为每公顷36.05只,5.30只,和4.35只;生物量依次为每公顷917.18g,205.0g和107.759。初步结论是:1.森林遭破坏后小兽群落组成,数量以及物种相对丰盛度均发生变化。2.物种多样性随森林破坏强度的加大而减小。3.森林破坏强度越大,小兽密度和生物量则越小。