Analysis On The Plant Functional Groups Of Degraded Grassland In Upreach Area Of Shiyang River

Plant functional groups are the plant species in the groups which have the similar reaction to the environment , or have the similar function to the main ecological course. Life-form of plant is widly used in classifying Plant functional groups. In this research , by dint of life-form plant functional groups as the main research objects , using plant species , plant community , soil nutrients in different layers , phenological phenomenon characteristics as the subordination objects to analyse the characteristics of Alpin degraded grasslands upreach area of Shiyang river , and to construe the reasons why the grasslands degraded . The results showed that:There were five plant functional groups in this area , the perennial bunch gramineous grass and perennial weed were the most important life-form plant functional groups .1. Stipa. krylovii Roshev. was the primary components of the perennial bunch gramineous grass functional group . The characteristics in degraded grassland showed that :1) the numerical characteristics had distinct association between perennial bunch gramineous grass and Stipa. krylovii Roshev , except the coverage in degraded grassland , the similarity coefficient were variance from 0.807 to 0.999 ; 2) the density, the coverage, the height, the phytomass and the importance value decreased by 45.1%,42.1%,47.6%,70.3% and 43.0% for each ; 3) the niche breadth of S. krylovii Roshev decreased by 15.7% , and the niche overlap with other species increased; 4) the inter-species association between the perennial bunch gramineous grass and other plant functional groups increased ; 5) this type of plant functional group was the decreased plant functional group in degraded grassland.2. Heteropappus Altaicus (Willd.) Novopokr .is the most importance component of the perennial weed functional group , the characteristics of the plant functional group were shown that : 1) the numerical characteristics had significant association between perennial weed and H. Altaicus , the similarity coefficient were variance from 0.763 to 1.000 in both degraded grassland and CK grassland ; 2) when the grassland degraded in this area , the density , the coverage , the height , the phytomass and the importance value increased by 141.1%, 109.8%,139.2%, 404.5% and 116.45% in file , so the numerical characteristics of this plant functional group increased distinctly ; 3) the niche breadth of H. Altaicus decreased by 300% and the niche overlap increased; 4) the association relationship between perennial weed and other plants increased ; 5)so this type of plant functional group was the increased plant functional group in degraded grassland.3. There had been ecology compensation existing in the inner plant functional groups .For example , S. krylovii and A. cristatum were belong to the same plant functional group, S.krylovii decreased in degraded grassland , while the A. cristatum increased. But the compensation could not prevent the trend of this plant functional group degrading , it could be conferred that the compensation in this degraded grassland could cushion the degraded trend of this plant functional group , but not prevent degrading trend .4. There also had been ecology compensation existing between plant functional groups .For example the function of S. krylovii decreased , while the perennial weed functional groups increased in the process of disturb There were two faces to the phenomena , for one thing , it could increase the stability of the plant functional groups which were disturbed; for the other , it could raised the risk which the grassland changed to other succession stages.5. The status and functions of perennial bunch gramineous grass could be decreased by grazing in the grassland in the early spring , while perennial weed could use the resources which the perennial bunch gramineous grass left to grow well . Additionally the perennial weed plant functional group burgeon late , that maded it avoide grazing , that's one of the reason to explain the status and function of the perennial weed raised in degraded grassland .