关键词: 供氮水平, 损失, 吸收, ¹⁵N尿素, 果实品质, 苹果, 利用

Abstract: By using niche theory, this paper analyzed the niche characteristics of ‘noxious and miscellaneous grass type’ degraded grassland on the northern slopes of the Qilian Mountains under the grazing disturbance of Stipa krylovii grassland. In the degraded grassland of ‘noxious and miscellaneous grass type’, the constructive species (S. krylovii) and the main accompanying species (Stellera chamaejasme and Melica przewalskyi) had the similar higher importance value. The niche breadth of Aneurolepidium dasystachys and S. chamaejasme was 0.925 and 0.922, respectively, being greater than that of the other species, while the niche breadth of
S. krylovii was only 0.669. There were 207 species pairs having the niche overlapping index over 0.05, indicating a lower niche polarization of the populations. The niche of the degraded grassland had some special characters different from other degraded grassland types, which could be related to the changes of community microenvironment, the resistance strategies of the populations against the microenvironment changes, and the populations themselves adaptability, reflecting the adaptive approaches of the populations to the regeneration under grazing disturbance.

Key words: apple, utilization, loss, ¹⁵Nurea, nitrogen level, absorption, fruit quality.