The Effect Of Plants Secondary Metabolites On The Forage Of Little Herbivorous Mammals In Qinghai-Tibet Alpine Meadow Ecosystem

The research was carried out from late May 2008 till late September 2008 in the Haibei Alpine Meadow Ecosystem Research Station, the Chinese Academy of Science. Plateau pikas (Ochotona curzoniae) and root voles (Microtus oeconomus) are little herbivorous mammals survive in Qinghai-Tibet plateau for many years. In order to explore their utilization and adaptation to the secondary metabolites in the plants growing in special environment, such as intensive ultraviolet, high altitude, hypoxia, low temperature and diverse vegetation coverage, we determined the features of floras, the contents of total polyphenols, simple phenols, condensed tannins and flavonoids, the activity of the phenylalanine ammonia-lyase (the key enzyme of synthesis of polyphenols and flavonoids ) in twenty one plants of ten families, observed the feeding amount of animals, analyzed the correlation between their choices of food with plant communities and plants secondary metabolites. The results were as follows.(1)The plant community structure in the research location varied in different months. Specifically, the number of species was at the lowest in May and scaled atop in July; the diversity index of species and the average above-ground biomass take off steadily from May till August and peaks in August followed by the gradual decline from September; the evenness index is the lowest in May and climbs up to the highest in August.(2)The contents of flavonoids in most plants increased sequentially, characterized by the lowest in June, the highest in July and August and a declining tendency in September. The contents of total polyphenols had a steady rise tendency from June to August and a drop inclination in September. With regard to the contents of simple phenols, a tendency of steady increase and decrease was detected respectively from June to August and in September. The contents of condensed tannins, also finding a monthly steady rise tendency, bottomed out in June followed by a pick-up and a significant rise to the peak in September. The activity of phenylalanine ammonia-lyase showed a downward trend during June and July and an upward one during August and September. (3)Being the most favored plants for plateau pikas, Taraxacum sp. and Plantago asiatica find comparatively higher feeding frequency and larger feeding amount. Other favored plants varied with the lapse of months. Plantago asiatica and Potentilla nivea were the most favored plants for root voles and other favored plants also varied with different months.(4)The feeding amount of the plateau pika was in strikingly negative correlation with the height of plants, while it was not in conspicuously positive correlation with the coverage of plants and biomass. The above finding revealed the height of plants could inhibit the forage of plateau pikas in contrast to the coverage and biomass of plants which facilitate their forage. As regards root voles, their feeding amount manifested no noticeable correlation with the heights, quantities, coverage, biomass and important values of plants, which explained the food choices of root voles may not be affected by plant community characteristics.(5)The feeding amount of plateau pikas was in significant negative correlation to the contents of flavonoids, but did not manifest any notable correlation with other secondary metabolites, revealing the contents of flavonoids in plants could inhibit the forage of plateau pikas as opposed to other secondary metabolites which cannot. The feeding amount of root voles were in significant negative correlation with the contents of phenylalanine ammonia-lyase, simple phenols and total polyphenols in plants, and had no noticeable correlation with the contents of flavonoids and condensed tannins in plants, which confirmed simple phenols and total polyphenols in plants could inhibit the forage of root voles.