Role of Cystitis Cystica et Glandularis and Intestinal Metaplasia in Development of Bladder Carcinoma
详细信息查看全文 | 推荐本文 |
摘要
Runoff and erosion are critical geomorphic processes in arid ecosystems, and they are strongly affected by vegetation patterns. Little is known about the influence of spot-structured vegetation on runoff and erosion in temperate deserts; especially the effects of vegetation patterns and human-induced disturbances on runoff-triggered nutrients redistribution are poorly understood. A series of simulated rainfall experiments were conducted in the Tengger Desert, northern China, to examine (1) the effects of shrub patches on runoff and erosion and related nutrients redistribution on hillslopes, (2) whether different amounts of water and nutrients are stored in the shrub patches compared to open inter-patch areas, and (3) how the runoff and erosion and related nutrients redistribution processes respond to human-induced disturbances. The results indicate that in undisturbed plots 53%of the applied water became runoff from crust patches and 55%of this was redistributed to the shrub patches. Water penetration was significantly deeper in shrub patches than in crust patches, and more than 75%of the sediments, 63%soil carbon, 74%nitrogen and 45 not, vert, similar 73%dissolved nutrients triggered by runoff from crust patches were delivered to shrub patches. The disturbance of crust patches tended to result in the uniform distribution of water over the whole slope and the reduction of flow of vital resources from the crust patches to the shrub patches. Disturbance of macrophytic patches significantly degraded the capacity for resource capture and retention and thereby decreased resources, all of which are crucial for the maintenance of plant productivity and vegetation cover. The understanding of the function of patterned vegetation in the study area suggests that it represents an aspect of the ecosystem that requires careful management.

© 2004-2018 中国地质图书馆版权所有 京ICP备05064691号 京公网安备11010802017129号

地址:北京市海淀区学院路29号 邮编:100083

电话:办公室:(+86 10)66554848;文献借阅、咨询服务、科技查新:66554700