Studies On Patterns Of Component Species Number And Biomass Of Desert Rodent Community Under Different Disturbance

The four kinds of sites under different human disturbance were selected in the typical region of the Alashan Desert of Inner Mongolia from April until October in 2002-2007 , i . e. a farmland area , a rotational-grazing area , a over-grazing area and a prohibited-grazing area. The four kinds of mark-recapture samples and of line samples were taken in different human disturbance areas. In inder to reveal feature of response of rodent community to different disturbance in desert fragile ecosystem , following study was done : Firstly , The features of density, biomass per hektare annual changed of rodent community and species number, number and biomass annual changed of dominant population of corresponding community were comparatively analysed under different disturbance. At the same time , Number and biomass distributed of rodent community were analysed on different disturbance areas. Secondly , Diversity indices , number eveness indices , richness indices , dominance indices , biomass eveness indices annual changed of rodent community were analysed under different disturbance. Finally , sensitive features of species number and biomass were synthetically analysed. Moreover , the corelation between species (number and biomass) and vegetation factors were synthetically analysed. The results showed:(1) The number and biomass of rodent community were distributed as follows on different disturbance areas in six years. Number annual changed of rodent community was more prominent on over-grazing area . Number annual changed of rodent community on rotational-grazing area was apposite to those of rodent community on over-grazing area. Number annual changed of rodent community on prohibited-grazing area was significantly different from those of rodent community on rotational-grazing area and over-grazing area. Number seasonal changed of rodent community on rotational-grazing area was similor to those of rodent community on over-grazing area . Number seasonal changed of rodent community on prohibited-grazing area was significantly different from those of rodent community on rotational-grazing area and over-grazing area. Regularity of number seasonal changed of rodent community on farmland area was out of accord. Biomass annual and seasonal changed of rodent community were the same as number annual and seasonal changed of rodent community and also more prominent on over-grazing area . Biomass annual changed of rodent community was decided by number annual changed of rodent community on farmland areas . Biomas seasonal changed of rodent community , which was influenced by difference between indivual biomass of different species and between indivual biomas of same species , was not entirely decided by number seasonal changed of rodent community . Biomass annual and seasonal changed of rodent community were both out of accord with number annual and seasonal changed of rodent community on rotational-grazing area and prohibited-grazing area .(2) The species number was more on rotational-grazing area and over-grazing area.. The fluctuation tendency of biomass of rodent community per hektare were all in accord with those of density(capture rate per 100 trap nights)on different disturbance areas in 6 years . The trends of annual number and biomass of component species in the rodent communities were different under different disturbance. Dominant species in rodent community showed different response under different disturbance , which was the characters of sensitive response. The dominant species of sensitivity to different human disturbance also made a key important role and influenced patterns of number and biomass in rodent community under different disturbance. The above analysis account for dominant species number in rodent community was sensitive mechanism under different human disturbance in the typical region of the Alashan Desert. The appearance and disappearance of dominant species was regarded as an indication of rodent community under different human disturbance . The results from two methods ( line sites and mark-recapture samples ) both showed : the appearance of Meriones unguiculatus and disappearance of Dipus sagitta were regarded as indication of rodent community on the farmland area ; the appearance of Dipus sagitta and rising of its number were regarded as indication of rodent community on the over-grazing area . Sensitive response of dominant species biomass was based on its number in rodent community and was correlated with size of biomass between dominant species.(3) Shannon-Weiner diversity indices , Simpson diversity indices and Margalef richness indices of rodent community on farmland area were more than those on rotational-grazing area , over-grazing area and prohibited-grazing area under different disturbance in six years .(4) The species of sensitivity to number were different and significantly varied as follows: hydrophilic species(Cricetulus barabansis) on the farmland area , hydrophilic species(Citellus dauricus) and xerophilic species(Dipus sagitta , Phodopus roborovskii) on the rotational-grazing area . The species of sensitivity to number were the same as the species of sensitivity to biomass on the prohibited-grazing area , which both included Allactaga sibirica and Meriones meridianus. The number of species of sensitivity to number were less , whereas the number of species of sensitivity to biomass were more on the over-grazing area . The species of Mutual sensitivity to number and biomass were Allactaga sibirica , Dipus sagitta , Citellus dauricus on the over-grazing area . The species of sensitivity to number and biomass both included Meriones meridianus , and the population number of Meriones meridianus was higher , also the population biomass of Meriones meridianus was larger on different disturbance areas in spite of on the over-grazing area .(5) Xerophilic species were significantly correlated with shrub and herbage on the rotational-grazing area and over-grazing area . Hydrophilic species were significantly correlated with variables of vegetation community on the farmland area(Citellus dauricus, Cricetulus barabansis) and prohibited-grazing area(Cricetulus barabansis). Meriones meridianus was significantly correlated with variables of vegetation community and was regarded as a eurytopic species in different disturbance habitats .