| Grassland biomass plays an important role in the allocation of nutrients and carbon cycle in grassland ecosystem, but also has an important influence on the structure and function of grassland ecosystem. At present, researches on the grass root mostly focus on the species of root morphology, physiological characteristics and root architecture. Most studies of the distribution of underground biomass of grass root was mainly limited to the structure characteristics of a specific vegetation type, the systematic comparative study on the distribution of root biomass for different grassland types and degradation grassland types has not been reported. Based on the above reasons, carried out a lot of aboveground biomass and root of stratified sampling survey in Ewenki Banner and Chenbaerhu Banner of Hulun Buir Grassland, this paper studied the relationship between the ground biomass and that of underground biomass, determine the distribution pattern of plant roots along soil depth, and analyzes the relationship between root distribution patterns and composition of major plant groups, researches the effect of different grassland utilization and grassland degradation on root distribution pattern, discusses the contribution of root biomass on carbon storage of grassland ecosystem.The main conclusions are as follows:1 The root biomass of each soil depth and that of 0-30 cm layer and 0-100 cm layer had significant correlation with aboveground biomass of steppe community, the linear regression equation of 0-30 cm and 0-100 cm soil depth can be expressed as: Y=5.853x+237.8 (R2=0.434; P< 0.001) Y=6.548x+362.5 (R2=0.498; P=0.002)2 Analysis with each quadrat sampling, the steppe communities have diverse root distribution pattern types, including V shape, Y shape, E shape, T shape and L shape, O shape and X shape. Among them, there was a positive correlation between root biomass and aboveground biomass for the first 4 root distribution shapes, but that showed a negative correlation of the last 3 root distribution shapes. The result is a benefit complement to the original understanding about T distribution shape of root for mast steppe communities.3. The pattern shape of root distribution are closely related with the composition of plant groups in grassland vegetation. The pattern shapes of root distribution can be mainly divided into 4 types such as V shape, Y shape, T shape and L shape based on average root biomass of each layer for the main communities. Among them, V shape and Y shape are dominant with tall bunch grasses and forbs, and the L shape is with Rhizome grass, at same time short bunch grass proportion increased, but Carex occupies a significant advantage for T shape.4 The stepper communities of different degradation degree have different root distribution patterns. The distribution pattern of ungrazing community and the seriously degraded community showed T shape pattern, but the former is dominant by the constructive species of original community, and the latter is dominant by constructive species of severe degradation. In the V shape and L shape, the constructive species of original community and forbs occupy absolute advantage with similar proportion, Y shape is still dominant by the constructive species of original community, but the proportion of onstructive species of severe degradation community increased significantly.5. The use of a different grass root configuration of root shoot ratio has a certain extent.6. The analysis of carbon storage level of different grassland types show that, the carbon density of grassland ecosystem with different root distribution pattern is obvious different. The differences and changes keep well consistence to the degradation state corresponded by various root pattern shapes. |
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