Study On The Plaintive Forest Structure Characters And Growth Condition Of Northern And Southern Mountains In Lanzhou

The special landform and drought natural characteristics of Lanzhou serious affected the green space system of Lanzhou.The ecological environment became fragile and the soil was serious lost in urban.Therefore,changing the ecological environment and reducing the pollution is the first step of building the green space system of Lanzhou.In order to provide the scientific theory for developing the structure,improving the benefit evaluation of ecological environment and changing the living environment of the green space system in Lanzhou,we studied the structure characteristics and the growth of urban forest.The range and formation of urban forest of Lanzhou were analyzed by summarizing domestic and abroad studys.We studied on planted forest in southern and northern mountains of Lanzhou.The structure characterisics of urban forest and growth condition of artificial forest under different water supporting method were studied.The fixing of oxygen and releasing of carbon dioxide of Lanzhou forest were analyzed by consulting materials and using existing experiment conclusion and the computational method.The results showed that:(1) The major forest type in Lanzhou city were protective forest,public forest, special forest,landscape forest and commercial forest.(2) The 185 tree species belong to 137 genus and 56 families.1 fern,4 gymnosperms belong to 9 genus 4 family,173 spermatophytes belong to 127 genus and 51 family.The legume, rosaceous plant,feverfew and gramineous plant are rich.(3) The major forest association groups type are Platycladus orientalis-Reaumuria soongorica association groups,Platycladus Orientalis-Caragana korshinkii association groups,Platycladus orientalis- Tamarix chinensis association groups,Platycladus orientalis-Lycium chinense association groups, Platycladus orientalis- Hippophae rhamnoides L.subsp sinenisis Rousi+Reaumuria soongorica association groups.The other forest area exclude for small area.The short forest growth time formed the simple but complete community structure, including arbor, bush and herb layer.(4) In northern mountain,the altitude had a more significant effect on several tree species than slope direction.Otherwise,the slope direction had a significant effect on southern mountain.(5) The different method of water replenishing affected the community structure of plaintive forest.In"three water"forestation area (water was conserved from rain, plastic muching and water injection to root for forestation),there was no arbor layer, only shrub and herb layer. In irrigated area, there was complex community structure of arbor and bush and herb layers. And the herb layer had better growth.Compared the species diversity index of"three water"forestation area and irrigated area,irrigated area had richer species than"three water"forestation area.And Simpson index and Shannon-Wiener index and Eveness of irrigated area were all higher than"three water"forestation area.So it indicated the irrigated area had richer species and higher species diversity and more species than"three water"forestation area.(6) Discharge of SO2, dust and smoke and O2 consume and carbon release were higher than absorption of SO2 and fixing Carbon and release of O2 in Lanzhou.Thus, construction of urban forest should be strengthened to increase the forest area.The urban forest could reduce the heat island impact,clean the air and adjust micro atmosphere to provide and improve comfortable environment.