Abstract: By employing the longterm simulation temperature experimental test device recommended by the International Tundra Experiment (ITEX), the responses of plant chemical components (crude ash, neutral detergent fiber, acid detergent fiber, lignin, crude fat, crude protein and nitrogen free extract) and soil physicochemical properties (available nitrogen, available potassium, available phosphorus, total nitrogen, total phosphorus, total potassium, organic matter, and moisture content) to warming on degraded and undegraded Kobresia humilis meadows were studied. The results showed that long-term simulated warming significantly affected soil physicochemical properties, and plant chemical components of three functional groups (P<0.05). There were obvious interactive effects between plant chemical components and soil physicochemical properties in degraded K. humilis meadow under long-term simulated warming (P<0.05). The simulated warming increased soil available nutrients which could be directly used by plants, but decreased soil organic matter, total nitrogen, total phosphorus, total potassium and moisture contents in the degraded meadow, compared with the control. Meanwhile, warming decreased the contents of crude fat, crude protein and nitrogen free extract of highquality herbage (Gramineae and Cyperaceae), while increased the contents of some indigestible ingredients such as crude ash, neutral detergent fiber, acid detergent fiber, lignin, consequently, resulting in a decrease in ruminant assimilation ability. Under long-term simulated warming conditions, the contributions of soil environmental factors to plant chemical composition were as follows: available nitrogen > organic matter > moisture content > available potassium. Canonical correspondence analysis showed that longterm warming further increased the advantages of Gramineae and Cyperaceae species in the nondegraded K. humilis meadow, while forbs gradually declined. In the degraded meadow, the dominance of dominant species declined, intensifying the degradation of grassland.

Key words: fishery resources, probability of detection, sample size, diversity of species, optimization