The productivity and nutritive value of some cultivated perennial grasses, Bromus inermis (B), Elymus sibricus (S), E. nutans (N), Agropyron cristatum (A), Poa crymophila (P) and mixtures B + N, S + A, B + S + A, S + B + N, N + S + A, B + S + N + A, B + N + A + P, B + S + A + P and S + N + A + P, in the alpine region of the Tibetan Plateau were investigated. Elymus nutans and E. sibricus and the mixtures, B + S + N + A, B + S + A + P and S + N + A + P, were most productive with yields of dry matter (DM) of between 11 000 and 14 000kg)1 of biomass annually in the second harvest year. Acid-detergent fibre (ADF) concentrations increased (P<0

Forage selection plays a prominent role in the process of returning cultivated lands back into grasslands. The conventional method of selecting forage species can only provide attempts for problem-solving without considering the relationships among the decision factors globally. Therefore, this study is dedicated to developing a decision support system to help farmers correctly select suitable forage species for the target sites. After collecting data through a field study, we developed this decision support system. It consists of three steps: (1) the analytic hierarchy process (AHP), (2) weights determination, and (3) decision making. In the first step, six factors influencing forage growth were selected by reviewing the related references and by interviewing experts. Then a fuzzy matrix was devised to determine the weight of each factor in the second step. Finally, a gradual alternative decision support system was created to help farmers choose suitable forage species for their lands in the third step. The results showed that the AHP and fuzzy logic are useful for forage selection decision making, and the proposed system can provide accurate results in a certain area (Gansu Province) of China.

天然草原退化是北方草原地区一个严重的生态经济问题，超载放牧是引起草地退化最直接的根本性原因。对甘肃省肃南县红石窝乡的草原畜牧业生产现状调查研究表明，草原产权制度与草地过度利用密不可分，产权制度设计的缺陷和制度供给的滞后性使草地的使用和保护处于一种无序状态，诱发了牧民掠夺式经营行为的发生，致使天然草原被长期过度利用。

对不同类型草地功能群多样性和组成与植物群落生产力之间的关系进行了探讨。结果表明：（1）在矮嵩草（Kobresia humlis）草甸和金露梅（Potentilla f roticosa）灌丛中，豆科植物的作用比较明显，而其他功能群植物的作用较弱。（2）在藏嵩草（Kobresia tibetica）沼泽化草甸和小嵩草（K. pygmaca）草甸中，虽然杂类草、C3 植物和莎草科植物功能群的生产力占群落初级生产力的比例较大，但二者在统计上没有显著性差异，这表明群落生产力除受物种多样性的影响外，也受物种本身特征和环境资源的影响，更主要的是受到功能群内物种密度和均匀度的影响，即功能群组成比功能群多样性更能说明对生态系统过程的影响。（3）不同类型草地群落植物功能群盖度与群落初级生产力呈显著的线性相关。（4）不同类型草地群落生产力与功能群内物种数的变化均表现为单峰曲线关系，即功能群内物种数处于中间水平时，群落生产力最高。