Study On Drought Resistant Forestation Technology Of Lhasa Semi-arid Valley And Overflow Land

Drought resistant forestation technology is very important in the ecological environment construction in arid area. In Lhasa semi-arid valley and overflow land , around the recovery technique and vegetation reconstruction of degraded ecosystem , develop the selection and collocation of suitable forestland species and drought resistant forestation technology, put forward drought resistant forestation technology in semi-arid valley and overflow land , it's very meaningful to design a set of ecological safe shelter zone in Lhasa semi-arid valley and overflow land, and also construction needs of the State Ecological Safe Shelter Zone on the Tibet Plateau. So, this paper according to the reasons of water storage and less rain, afforestation survival rate and tree increment are low in Lhasa semi-arid valley and overflow land, through analyzing the rainfall,temperature,humidity and evaporation, combined with different site types, established a technical research on drought resistant forestation technology in three typical site types in river valley, have been selected with the species of s. var. tibetica,populus alba,Salix microstachya and Jiangzi sea-buckthorn,using drought-relief technical measures such as aquasorb mix soil + rooting powder, aquasorb mix soil, rooting powder dipping the root, film mulching, straw mulching ,pebble mulching, film mulching + aquasorb mix soil. The results show that:In Lhasa semi-arid valley and overflow land, afforestation in spring and rainy season, can improve afforestation Survival Rate and the results show that afforestation survival rate is higher in rainy season than in spring . Do research in preserving rate of afforestation in next spring ,it improved 20.4%, 21.1%,and21.5% than in rainy season. In planting effect, afforestation in spring in river valley is suitable, and repair planting in rainy season.Sedimentary sand type afforestation technology. Seven different treatment measures are taken, aquasorb mix soil + rooting powder, aquasorb mix soil, rooting powder dipping the root, film mulching, straw mulching ,pebble mulching, film mulching + aquasorb mix soil, and the test tree planting is populus alba. Results show that under the different treatment measures in all can reach moisture retention. The most influence on the soil temperature and water , the survival rate and decreasing, high growth and the Biomass of populus alba is aquasorb mix soil + film mulching, then aquasorb mix soil + rooting powder + film mulching, the last is rooting powder dipping the root.Sandy gravel soil types of afforestation technology. Six different treatment measures are taken, aquasorb mix soil+ rooting powder,aquasorb mix soil,rooting powder dipping the root,film mulching,straw mulching and film mulching+ aquasorb mix soil, the test tree planting is JiangZi seabuckthorn. Results show that, the influence on this content is film mulching + aquasorb mix soil; Additionally, straw mulching,film mulching,and aquasorb mix soil+ rooting powder three measures.Sandy gravel layer thickness type afforestation technology. Five different treatment measures are taken, aquasorb mix soil+ rooting powder,film mulching,straw mulching,pebble mulching and film mulching+ aquasorb mix soil, the test tree planting is s. var. tibetica. Results show that, the most influence on this content is film mulching+ aquasorb mix soil , then aquasorb mix soil+ rooting powder,film mulching,pebble mulching,straw mulching.Soil structure is one of the factors, the success or failure of the afforestation. Effect degree for thick sandy gravel soil>sandy gravel soil>Sand deposition. In three different types of site, using the same four technology, to improve soil temperature and soil moisture and maintain the obvious effect. From the experiment results, film mulching+ aquasorb mix soil in soil water and heat, seedling survival rate, most obvious effect. In comparison, rooting powder dipping the root mode, the effect is not obvious; Repeat straw mulching mode,pebble mulching mode, the effect in between.