Study On Micro-climate Characteristics Of North Subtropical Secondary Oak Forests

In this paper, micro-climate characteristics of north subtropical secondary oak forests were studied. The main results are summarized as following:(1) From the perspective of the year,the difference of atmospheric temperature and humidity inside and outside of oak forests was not significant Majority time in the day, the temperature inside of forest was higher than that outside. The difference of the maximum temperature in the same time between inside and outside was the best significant in July, and also in July, the average temperature was the highest. In sunny, cloudy or rain day, the humidity changes were on U-shaped. The average monthly humidity was the highest in July and was the smallest in November also inside and outside. Both inside and outside the Oak forests,the relative humidity changes of every month were correlative.(2) Characteristics of solar radiation changes inside and outside of oak forests: the diurnal variations of GSP, PAR in different weather were same basically. The margins of diurnal GSR variations inside and outside of oak forests were compared in different seasons: summer>autumn>spring>winter; The diurnal peaks of PAR inside of oak forests were compared in different seasons: spring> winter>autumn> summer. The monthly average of solar radiation inside of oak forests was far below outside. In the monitoring cycle, solar radiation inside and outside of oak forests were 323579.7 w/m² and 1232281 w/m² respectively.(3) The monthly change of soil temperature in four levels were on U-shaped all. The range of temperature change was smaller as the soil depth was deeper. From the point of view throughout the year, soil moisture content of each level was very stable. Soil moisture content increased with the increasing soil depth, but the range of soil moisture content change reduced as the soil depth was deeper.(4) Neither in terms of diurnal variation nor in terms of monthly variation, wind speed outside of oak forests is greater than that inside. Changes in wind direction throughout the year: inside of oak forests, northwest wind accounted for 14.6 percent, southwest wind accounted for 26.6 percent, southeast wind accounted for 27.8 percent, northeaster wind accounted for 31.0 percent; outside of oak forests, northwest wind accounted for 13.9 percent, southwest wind accounted for 9.7 percent, southeast wind accounted for 38.5 percent, northeaster wind accounted for 37.9 percent. The differences of wind speed inside and outside of oak forests was significant Throughout the year.(5) Above canopy that the ground 30m away from the Department, CO₂ concentrations in April was higher than other months (range in 382-390 mmol/mol), CO₂ concentrations in July was lower(range in 376-380 mmol/mol). The variations of CO₂ concentrations between day and night were pronounced in April and July.