A Comparative Study On The Physiological And Ecological Characteristics Of Salix Sclrophylla On The Naqu And Lhasa

Naqu is located in the northern part of the Qinghai-Tibet Plateau,and its zonal vegetation is mainly grassland and meadows.As the urbanization process of Nagqu accelerates,the urban area expands and its microhabitats are changed.The introduction of woody plants in the changed urban micro-habitats to meet the urgent needs of urban greening for woody plants has attracted much attention in the ecological community.The introduction of Nagaki woody plants has already begun in the last century.The results show that some woody plants can survive in Nagqu,but the mechanism of survival is still unclear.This study takes the Salix sclrophylla,a native plant of Lhasa at an altitude of(3,700 m)in Tibet,as a research object.It is migrated to the Nagqu city at a higher altitude(4,600 m).In an effort to reveal the physiological and ecological response mechanisms of S.sclrophylla in different environments and provide theoretical basises of introducing and cultivating the trees into alpine areas,such as Nagqu.The soil matrixs(e.g.,temperature,water capacity,or nutrients),air temperature,light resource of Nagqu and Lhasa are tested and analyzed.The S.sclrophylla photosynthetic characteristics,leaf functional traits and were also tested.The main results and conclusions are as follows:(1)The differences in atmospheric and soil environmental factors between Nagqu and Lhasa are lower than those in Lhasa.The effective accumulated temperature of Nagqu is insufficient.The average monthly temperature of Nagqu is only 7-8 months for 10?.The monthly average temperature of Lhasa is greater than 10? to September.The growth season soil temperature in Nagqu was 13.9?,which was 5.5? lower than that in Lhasa.The Nagqu soil moisture was between 13.8-23.3%,while the soil moisture in Lhasa varied from 6.1%to 10.3%.Except for the total phosphorus content,the soil nutrients in Nagqu were higher than that in Lhasa.There was surface nutrients accumulation in both of areas.The soil pH was 8.6 in Nagqu while was 7.6 in Lhasa.(2)The S.sclrophylla' light saturation point reduced,light adaptation range got narrowed,SPAD decreased by 13.2%,maximum net photosynthetic rate decreased by 18.46%after it was migrated to Nagqu.There was a "photosynthetic lunch break"phenomenon in the leaf photosynthesis,and was restricted by non-stoma and stomatal factors.The proline content and superoxide dismutase activity increased after it was migrated from Lhasa to Nagqu.This study found that S.sclrophylla was affected by strong radiation and low temperature which led to the SPAD and photosynthetic capacity decreased.The photosynthesis was inhibited under the influence of stomatal and non-stomatal factors,and the accumulation of matter was inhibited.On the one hand,S.sclrophylla enhance the ability of resource acquisition by significantly increasing leaf area and Specific leaf area.In addition,the proline content and superoxide dismutase activity increased,indicating that the stress resistance increased after migration and to adaptated to alpine habitat.