关键词: 杉木, 水分利用效率, 年龄序列, 养分状况

Abstract: In order to identify the features of plant seeds in dung of yak and Tibetan sheep grazing at different grazing stages of winter pasture (alpine meadow) on Eastern Qilian Mountain, the number of species, the seed diversity index, the seed number and density were studied. The results showed that in the same grazing stage, the number of seed species in yak dung was higher than in Tibetan sheep dung. The seed density in yak dung was lower than in the Tibetan sheep dung, but the difference was significant only at the middle grazing stage. At the initial and final grazing stages, the seed diversity index in yak dung was significantly higher than that in Tibetan sheep dung. The seed species number and seed density (grains·kg^-1) in yak dung at the different grazing stages were both in order of final grazing stage > initial grazing stage > middle grazing stage, and those in Tibetan sheep dung were in order of initial grazing stage > final grazing stage > middle grazing stage and of middle grazing stage > final grazing stage > initial grazing stage, respectively. The seed number of sedge was the highest in yak dung, while the seed number of forbs was the highest in Tibetan sheep dung. The different conditions of winter pasture at the different grazing stages made the seed distribution different in each synusia of plant community, together with the differences in grazing habit, forage intake per bite and digestibility of yak and Tibetan sheep, causing the differences in seed density, seed species and seed diversity of their dung.

Key words: chronosequence, Cunninghamia lanceolata, nutrient status, water use efficiency