关键词: 群落结构, 防护效应, 土壤特性, 过渡带, 生态功能

Abstract: The soil desertification and the vegetation degradation are serious in the oasis-desert ecotone of the lower reaches of Tarim River, which severely damaged the stability of oasis. To, restored and rebuilded the shelterbelt of oasis-desert ecotone is an important issue for the oasis sustainable development. In this paper, the typical shelterbelts of oasis-desert ecotone in the lower reaches of Tarim River as the objects, and the environmental features and ecological function of shelterbelts, as well as reasons resulted in the differences between them, which structure including arbor-shrub-herb, arbor-shrub and only arbor were studied based on field investigation and laboratory analysis. Setting the monitoring points each 10 m among 0 to 100 m at the community leeward side, meanwhile, a control point was selected at the bare ground without vegetation or sparse vegetation in the community windward side. The monitoring height was set 0.5, 1, 2, 3, 4, 5 m in these monitoring and control points. When observing the protection benefit of shelterbelts, simultaneous monitoring the wind speed 1 min at different height of the community and the control point by anemometers (DEM6). Air temperature and relative humidity were synchronously measured in the 2m height of the shelter community and the control point every 2 hours from 08∶00 to 20∶00 using hygrothermograph (AR827) in the sunny day. Soil temperature at 0, 5, 10, 20, 30, 50, 80, 100 cm of the shelter community and the control point was simultaneously monitored using digital thermometer (HH10/Onecal) every 2 hours from 08∶00 to 20∶00 in the sunny day, and the soil moisture, salinity and nutrients at different layers (0-5, 5-10, 10-20, 20-30, 30-50, 50-80, 80-100 cm) were measured by conventional methods. The results showed as follows:(1) All of the shelterbelts with different structures in the study area has particular micro-environmental features, such as adjusting the air temperature and air relative humidity, improving soil properties, stabilizing soil temperature and slowing down wind speed, especially for the plant community mixed with arbor-shrub-herb, which could more effectively increase soil organic matter, total N, total P at 0-50 cm soil layer and total K at 20-100 cm soil layer, improve soil moisture at 0-30 cm soil layer, inhibit soil salt at 0-100 cm soil layer, stabilify soil temperature at 0-50 cm soil layer. It suggested that the shelterbelt mixed with arbor-shrub-herb effectively changed the soil physical and chemical properties to improve the plant growth and development. (2) The effective height and distance for slowing wind speed of the shelterbelt with arbor were 2-3 m and 40 m, respectively, the plant community mixed with arbor and shrub were 2-4 m and 60 m, respectively. The effective height for slowing wind speed of the plant community mixed with arbor, shrub and herb were less than 1m and 2-4 m, and the effective distance were 60 m when the height was more than 1 m and 100 m when the height was less than 1 m. (3) The rational community structure and higher coverage and density were main reasons which resulted in the environmental and ecological differences of the different shelterbelts.

Key words: community structure, protection effect, soil property, ecotone, ecological function