Ecological Benefits Of Salix Gordejevii Sand-barrier In Desertification Land Of Northern Hebei

Chengde,located in the north of Hebei province,which belongs to the Sandstorm Source Control Project in and around Beijing and Tianjin constrction area,is one of the ecological potective screens of Beijing and Tianjing. Because the ecological environment is fragile in farming-pastoral zone and the land became desertified after vegetation destruction, vegetation restoration and reconstruction are main and basic measures of desertification control in desertification land of Norhtern Hebei. Planting biological sand-barrier both has the function of sand fixation and natural vegetation recovery. The severely desertified land were fenced by Mulan Forestry Administration Bureau of Hebei Province in 2003. Mainly technical measures including planting Salix gordejevii biological sand-barrier and artificial afforestation in the sand-barrier were taken on the basis of enclosure to shorten the vegetation restoration. This study examined ecological benefits of salix gordejevii sand-barrier in different slope position in fenced enclosures by field sruvey and observations, with main conclusions being achieved as follows:(1) There had been significantly differences between growth condition of Salix gordejevii in different slope positions after the sand-barrier been planted for 5-6 years. Salix gordejevii grew well in the top of slope and in the middle slope,while the decline of Salix gordejevii growth condition showed up in the lower foot slope.(2) The wind-break potency at the height of 0.5m in salix gordejevii sand-barrier in different slope positions reached more 40%.The effect of Salix gordejevii sand-barrier on the wind-breaking and sand-fixation in the top of slope was better than the middle and lower foot slope.The wind-break potency at the height of 0.5m in Salix gordejevii sand-barrier was 47.03%,and the ground roughness in sandy land with Salix gordejevii and the sand accumulation were 0.1903cm,0.1766m3 in the top of slope.(3) In 0～100 cm soil layer, the natural soil moisture of different slopes with Salix gordejevii sandy-barrier was the top of slope>middle slope>lower foot slope. The maximum field moisture capacity,capillary moisture capacity and the saturation moisture content of the soil in the lower foot slope were higher than the top of slope and the middle slope. In 0～40 cm soil layer,the order of slope ,in the term of soil total porosity,capillary porosity was the lower foot slope > middle slope > top of slope;in the term of non-capillary porosity was the top of slope>lower foot slope>middle slope.The soil mechanical composition was towards finer fractions from the top of slope to the lower foot slope.(4) The soil pH in the top of slope was deflected to alkalescence slightly and the soil pH in the middle slope and lower foot slope were belonged to neutrality. The soil organic matter average content in 0~40cm depth soil layer in the middle and lower foot slope were significantly higher than that of the top of slope. In 0～40 cm soil layer, the order of slope , in the term of soil total nitrogen content,soil total phosphorus content,soil available nitrogen content,soil available potassium content was the lower foot slope >middle slope>top of slope.(5) In 0～40 cm soil layer, the soil bacteria amounts of different slopes with Salix gordejevii sandy-barrier was the top of slope>middle slope>lower foot slope.There was no significant difference in soil fungi amounts and actinomycetes amounts between slopes with Salix gordejevii sandy-barrier. In 0～40 cm soil layer, the order of slope , in the term of soil urease activity,soil catalase activity was the lower foot slope >middle slope>top of slope,and soil invertase activity had no difference between slopes with Salix gordejevii sandy-barrier.(6) From the top of slope to the lower foot slope with Salix gordejevii sandy-barrier,the litter amount were 1.7522 t/hm2,3.1451 t/hm2,2.9720 t/hm2.The maximal litter water holding rate and the modified interception amount were 183.76%,4.5828 t/hm2 in the middle slope and the litter water-storage capacity in the middle slope was better than that of the other two slopes. In 0～40 cm soil layer, the soil saturation holding capacity of different slope with Salix gordejevii sandy-barrier was lower foot slope>middle slope>the top of slope.The soil capillary water holding capacity in the top of slope was lower than that in the top of slope and lower foot slope, but the non-capillary water holding capacity in the top of slope was higher than the other two slopes.(7) There were 7 families and 17 species of plants found in three slopes with Salix gordejevii sandy-barrier,among which 7 families and 15 species of plants appeared in the lower foot slope. From the top of slope to the lower foot slope with Salix gordejevii sandy-barrier,the dominant species of community shifted from annual herbaceous plant Kochia scoparia to perennial herbaceous plant Medicago ruthenica and Lespedeza floribunda,and the community vegetation biomass increased gradually.The species richness index of community in three slopes was lower foot slope>the top of slope>middle slope. Simpon diversity index,Shannon-Wiener diversity indexe,Pielou evenness indexe,Simpon dominance index had no difference between communities in three slopes.