Energy Environment And Heat Balance Of Pinus Tabulaeformis Community At HuoDiTang Forest Region In The QinLing Mountains

The forest environment and heat balance are very important content in forest energy system. Based on the observational data of the Pinus tabulaeformis community in HuoDitang forestry Region of the QinLing Mountains, daily and seasonal variation of solar radiation components (global radiation, net radiation, reflective radiation, effective radiation and long-wave radiation) were measured and analyzed. The value of heat balance components could be calculated by using Bowen-Ratio energy balance method. At the same time, the latent heat flux could be divided into transpiration heat flux and evaporation heat flux. Based on these research results, the evaporation of forestry soil and the transpiration of Pinus tabulaeformis community could be calculated by using latent heat of evaporation (L). The relationship between the evapotranspiration and climatic factors were analyzed by using principal component analysis method. The main results were as follows.Average values of daily global radiation, net radiation, reflective radiation, effective radiation, and downward, upward long-wave radiation were 14.83 MJ.m-2.d-1, 9.13MJ.m-2.d-1, 1.29 MJ.m-2.d-1, 5.83 MJ.m-2.d-1, 27.10 MJ.m-2.d-1and31.52 MJ.m-2.d-1 respectively. During the whole growing season, the total global radiation, net radiation, reflective radiation and effective radiation received by Pinus tabulaeformis community were 3252.252 MJ.m-2, 2157.509 MJ.m-2, 268.4 MJ.m-2, 808.343 MJ.m-2 respectively, with 66.98%, 8.25%, 24.85% of global radiation partitioned into net radiation, reflective radiation and effective radiation. During the whole growing season, the value of total net radiation, sensible heat flux, transpiration heat flux, evaporation heat flux and soil heat flux were 2173.5 MJ.m-2, 494.757 MJ.m-2, 1084.146 MJ.m-2, 492.908 MJ.m-2 and 86.457 MJ.m-2respectively, with 23.01%, 49.88%, 22.68%, 4.05% of net radiation partitioned into sensible heat flux, transpiration heat flux, evaporation heat flux and soil heat flux. During the growing season, the total evapotranspiration was 638.08mm, the transpiration of Pinus tabulaeformis community was 442.51mm, and the evaporation of forest soil was 201.19mm. In different typical weather, forestry soil temperature was influenced by shade of canopy, with the increasing depth of soil (30cm, 40cm), daily variation of soil temperature decreased. At night, with the increasing of depth of soil, the phenomenon of decreasing of soil temperature decreased. Principal component analysis showed that the order of climatic which infect on evapotranspiration was: net radiation>air temperature>relative humidity >wind speed>water vapor pressure>soil temperature.