绿洲-荒漠过渡带典型防护林体系环境效益及其生态功能

Effect of environmental and ecological function of shelterbelts in oasis-desert ecotone of the lower Tarim River

在塔里木河下游绿洲-荒漠过渡带,选取乔灌草结构(胡杨-柽柳-花花柴群落)、乔灌结构(胡杨-柽柳群落)和单一乔木结构(胡杨群落)三种典型防护林为研究对象,采用野外监测和室内分析相结合的方法,探讨了不同类型防护林对空气温湿度、土壤理化特性及防护效应等的作用,并分析了产生差异的原因及生态功能。结果表明:(1)干旱区绿洲-荒漠过渡带不同结构组成的防护林均可提高群落内温湿度的稳定性,改善土壤理化性质,其中乔灌草结构防护林较其它群落更有利于增加0～50 cm土壤有机质、全N、全P和20～100 cm土壤全K的积累;能更有效地增加0～30 cm土壤水分、抑制0～100 cm土壤盐分、稳定0～50 cm土壤温度;(2)单一胡杨林群落的有效防护高度为2～3 m,横向有效防护距离为40 m;胡杨-柽柳群落的有效防护高度为2～4 m,横向有效防护距离为60 m;胡杨-柽柳-花花柴群落的有效防护高度分别为小于1 m和2～4 m,高度超过1 m以上的横向有效防护距离为60 m,在1 m以下其横向有效防护距离可达100 m;(3)群落结构、植物密度和覆盖度是影响防护林环境特征和生态功能的主要原因。

The soil desertification and the vegetation degradation are serious in the oasis - desert ecotone of the low- er 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 shel- terbelts of oasis - desert ecotone in the lower reaches of Tarim River as the objects, and the environmental features and ecological function of sheherbelts, 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 laborato- ry 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 shelterbehs, simultaneous monitoring the wind speed 1 min at different height of the com- munity 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 shel- ter 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 re- suits showed as follows ： （ 1 ） All of the shelterbehs 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 1 m 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 sheherbehs.