The Relationship Between Locust Growth And Precipitation At Loess Region In Shanxi Province

52.5%of the territory of China is arid or semi-arid area with low vegetation coverage,which is the main ecologically and environmentally fragile region.Vegetation restoration and the improvement of ecological environment are constrained by limited available water resources(precipitation,groundwater, surface water).The artificial restoration and reconstruction of vegetation should be carried out in accordance with the basic principle-"Planting according to moisture".Only in this way can we achieve the anticipated growth effects and form the suitable vegetation community structure for the geographical and climatic conditions.Simultaneously,we can also enhance the stability of vegetation as well as the ecological,economic and social benefits.This thesis was based on forest ecology,tree measurement science,statistics and Other mathematical theory.All the basic data was from sample field investigation,standard and advantage wood analysis,and meteorological data in the research area.The study was explored from the relationship between locust(Robinia pseudoacacia L.) growth and precipitation.Based on the comprehensive analysis of locust growth,the evaluation index was created,and the relationship between different indicators of locust growth and different indicators of precipitation was established by different statistics methods such as charts,data,correlation analysis,and regression fitting.This thesis interpreted locust growth conditions under a particular precipitation level in semi-arid area of Loess Plateau,and provided a reliable breakthrough of basic data and research method for creating Locust stand in semi-arid area.The followings are the major findings and conclusions:1.The meteorological observation data after 1957 shows:the overall precipitation in the study area was decreasing,and the temperature was rising.This hot and dry situation in study area is extremely detrimental to vegetation growth of local area.The trend of climate change has become an important consideration for creating plantations. 2.Through the analysis of the relationship between locust growth and precipitation,we found tree height annual growth was affected by both previous year and this year's precipitation,there was a significant positive correlation between them.The precipitation of the past year had a big effect on annual growth of DBH and volume,and this effect became more obvious along with the increase of density.From the study of the relationship between growth indexes and precipitation indexes,it is positive correlation between tree height growth and accumulation of precipitation in fast growing period. Furthermore,it is positive correlation between dbh and volume growth as well as accumulation of precipitation in growth period.3.In the same study area,dominant tree height of standard age(14a) generally declined around 1m when an average annual precipitation declined 100m.The multiple form site index table of locust artificial forest in research area is established based on Sloboda model.4.By using the theories and methods of building site index table,we established the precipitation index table of locust artificial forest in research area.We further demonstrated its feasibility and practicality,then combined with the density,established a growth founction including density and precipitation of locust in study area.This provides a guided theoretical basis for locust stand management under different average annual precipitation.