The Environmental Adaptability Of Biomass Allocation And Root Functional Traits Of Stipa Krylovii In Degraded Alpine Grassland

It is an important ecological and evolutionary significance that the change and feedback plant biomass distribution patterns have a significant work on the plant ecological adaptation strategy, community function and reproduction model. As the important organ of uptake soil resources, plant root has functions to absorption, transmission and storage of water and nutrients and so on. The change of root biomass allocation ratio will affect the growth of root system, Plant uptake and utilization efficiency of soil resources is directly affected by the distribution pattern of root system, so the function of root system will affect the function and behavior of plant. Root architecture reflects the spatial arrangement of plant roots in the living space, which influences the efficiency and maintenance cost of the root system. The growth relationship between root forks number and the link length can reflected the root distribution space and distribution density vividly, which reflects the environment adaptation mechanism of plants under the environment stress, and it is an important way to understand the regeneration strategy of plant population. In view of this, in the grassland degradation in the northern slope of Qilian Mountains in the northwest and Stipa krylovii were selected for study, standardized major axis estimation method(SMA) was used, analyzed the relationship of biomass allocation model between aboveground and underground, trade-off relationship between root forks and root link length, and the distribution pattern of specific root length, to discussion the roots construction mode of change the expansion space and the distribution density by adjusting the root functional traits of carbon allocation, and enhance the plant resources absorption efficiency and the scope of the adaptation mechanism. The results show that:(1)In the process from the native grassland to the light, middle and severe degraded grassland, the coverage, height and aboveground biomass of the grassland community showed a decreasing trend, and the soil moisture is also significantly reduced. The dominant species of grassland community succession into Potentilla acaulis from S. krylovi.(2)In the different degradation gradient, the aboveground and belowground biomass allocation pattern of S. krylovi shows some differences. With the increase of degradation degree, the aboveground and belowground biomass of S. krylovi was significantly decreased, and the rate of aboveground biomass was lower than that of underground biomass. In other words, the ratio of underground and aboveground biomass of S. krylovii was decreased.(3)With the continuation of grassland degradation, the biomass allocation ratio of root and root suckers in the underground of S. krylovii was changed. The greater the proportion of underground biomass of root suckers, the less the proportion of underground biomass of root system of S. krylovii.(4)In each degradation gradient, root length and root biomass of S. krylovii showed an allometric growth relationship. With the increase of degradation degree, the slope of root length and root biomass of S. krylovii increased gradually, so that the specific root length(root length and weight ratio) of S. krylovii was gradually increased along with the continuation of grassland degradation.(5)With increasing of the degree degradation, the plaque of S. krylovii population gradually broken and the population stability was reduce, the number of root forks gradually increased while the root link length decreased gradually of S. krylovii; In each degradation gradient, the number of root forks and the root link length of S. krylovii were negatively correlated.The growth of root functional traits was restricted by the proportion of root biomass allocation. The community environment is the key factor to change the growth rate of the root system, when the competition between the adjacent bodies is increasing. As the dominant species of the grassland community, the coordinated growth of functional traits of S. krylovii, such as aboveground biomass, underground biomass, root biomass, root length, the number of root forks and root link length and so on, to optimize the relationship of resource revenue and consumption. This relationship of trade-off is difference in different degradation gradient, which due to the population status, plaque recession and community environment changes of S. krylovii. It is necessary to adopt the best life history strategy to adapt to the habitat.