Study On Microclimate Characteristics Of A Secondary Forest In Depression Between Karst Hills

Preliminary analysis the variation of the micro-climate characteristics in secondary forest by classical statistical methods, revealed the main impact factor of secondary forest and sloping farmland by principal component analysis and declared the coupled relationship between vegetation, soil and microclimatic with canonical correlation analysis of fragile ecosystem in Karst peak cluster depressions, through a comprehensive system of vegetation survey and Soil sampling and analysis, based on the two dynamic monitoring building of secondary forest and sloping farmland in depression between karst hills, besides the2years of continuous meteorological observations with their own automatic weather station. The main conclusions are as follows.(1) The globle solar radiation of the internal and external forest shows inverted U-curve. The difference of different weather of canopy shelters:sunny>cloudy>rainy.the external radiation is higher than internal forest. Comparing with outside forest area, the average annual solar radiation inside forest reduced40.6%, there is significant seasonal variation.(2) The air temperature of the internal and external forest shows inverted U-curve.Comparing with outside forest area, the air temperature reduced from0.3℃to5.3℃, the forest can reduce the temperature of the highest value and raise the minimum value,there is significant seasonal variation.(3) The humidity of the forest shows U-curve. Comparing with outside forest area, the relative humidity increased5.8%.The humidification function of forest in spring and summer were better than autumn and winter, forest can significantly improve the minimum humidity, play a good cushioning effect.(4) The wind velocity of exernal forest is higher than internal, the average wind velocity reduced0.57m/s. The difference is significant, forest an obviously reduce the air wind.(5) Forest can keep the soil temperature stable. They were on U-shaped all in four levels, the range of the temperature change was smaller as the soil depth was deeper.(6) The principal component analysis showed that the main influence factor for the Sloping farmland ecosystems is SOC、TN、TK、AN、AK、temperature、humidity,Simpson index also played a leading role, in addition to Soil nutrient factors of pH、SOC、AN in secondary forest.(7) The canonical correlation analysis showed, in addition to the sloping land, secondary forest ecosystems of soil nutrients and climatic factors, the secondary forest soil microbes and vegetation have two pairs of canonical correlation was significant levels, the rest were only one pair of canonical correlation reached a significant level. In the sloping land ecosystem, the greatest impact of factor on the soil of SOC, AN, AK, Cmic is climate, In the secondary forest, the greatest impact of factor on the TN、AN、AK、Cmic、Fungi、 Shannon-Wiener index also is climate.