The Effect Of Global Warming On The Soil Meso-and Micro- Fauna Biodiversity Of The Western Songnen Grassland, China

The western Songnen grassland is located in the semi-arid farming region, and this area is sensitive to global change and the eco-system of this area is fragile. The excessive utilization on grassland has brought serious negative effects on the eco-system and biodiversity of this region, and has degeneraten the grassland in different degree. The current environmental stresses in the western Songnen grassland are made by the management method of grassland utilization under the background of global warming. While the soil fauna is an integral part of soil eco-system, it is necessary to study the response of soil fauna to the environment changes and human activities in the context of global warming.The research region of this thesis is the western Songnen grassland, and the study object is soil fauna. Through the situ long term artificial warming treatment, including using open top charmber and infrared radiator, we simulate the global warming. The warming treatments are combining with artificial precipitation control and grassland cutting, and we discuss the effects of global warming and human activity on the underground eco-system of the western Songnen grassland from the perspective of the biodiversity of soil fauna. We hope the results should provide the basic data and theoretical basis for the management of Songnen grassland under the context of global warming.The main results include the following aspects: 1. The effects of soil warming on the soil meso-and microfaunaIn the experiments of this thesis, the increase of the soil temperature elevates the individual number of Collembola in the plots. The dominant species Orchesellides.sp1 is most sensitive species to the soil temperature fluctuation. The soil warming treatments elevate both the individual density and percentage of Orchesellides.sp1. The warming treatments show the trend of increasing the species richness and diversity of Collembola community, while there is no statistical significant difference.The nematode community shows more complicated response to soil warming. Warming in daytime significantly reduces the nematode individual density, while warming in nighttime do not show significant effect on the nematode individual density. Warming in daytime significantly increases the species richness of nematode community, while warming in nighttime shows no significant effect on the species richness of nematode community. 2. The effects of soil moisture content on the soil meso-and microfaunaThe western Songnen grassland is located in the semi-arid farming region, and precipitation is one of the major environment limiting factors. But in the experiments of this thesis, the precipitation control treatments have showed no significant effect on the soil fauna. There are two reasons for this result: first, the ground surface evaporation of the western Songnen grassland is very sharp, and the temporary aritificial precipitation addition has very little effect on the soil fauna; and second, the western Songnen grassland has been under the semiarid environment condition for very long time, so, the soil fauna of this region should be adaptted to the drought environment condition. Thus, the aritificial precipitation control in this thesis shows no significant effect on the soil fauna. 3. The effects of grassland cutting on the soil meso-and microfaunaGrassland cutting is one of the major managements in Songnen grassland. For now, Songnen grassland is confronted with a series ecolgy problem including grassland degradation and the loss in ecosystem service function. In this thesis, the individual density and diversity of Collembola community decrease as the increasing of grassland cutting intensity. Soil fauna can enhance the the cycle of mass and energy fluxes of soil ecosystem, while this will be a negative effect on the infertile soil of the western Songnen grassland. So we suggest that the management of Songnen grassland should avoid excessive grass cutting.In this thesis, we find that soil nematode community shows different response to daytime warming and nighttime warming. We consider this difference is caused by the warming in daytime have maken the soil temperature go beyond the tolerance of some nematode species, so the nematode community structure shows different trend for the asymmetry warming. In most of the current research on the response of soil fauna to global warming, there is very little attention on the asymmetry of global warming. So we suggest more attention should be taken on the response of soil fauna to asymmetry warming.