Research On Radiation Balance And Environment Energy Of The Upper Canopy Space In Chinese Fir Forest

The effect of forests on reallocation of energy to the regional and global climate had an important influence. And the results of the redistribution of vegetation also affected the distribution of photosynthetic productivity. To understand the balance of energy redistribution characteristics of forest was not only significancy in understanding the ecological effects, but also in providing environmental parameters for Photosynthetic productivity research. Based on the observational data of the Chinese fir plantation in 2008 in Huitong, the characteristics of solar radiation components (global radiation, net radiation, reflective radiation, effective radiation and long-wave radiation) at different time scales, and the differences distribution rate of solar radiation in different seasons were measured and analyzed. Meanwile, the upper canopy space of the Chinese fir plantation forest was divided into three levels, A-layer from the ground 14.1m, B-layer distance of 22.5 meters on the ground, C-layer from the ground 32.5m. As we all kown, the environmental energy involved solar radiation, internal energy, position energy, all potential energy, kinetic energy, latent heat, appearance heat energy, warm-wet energy and so on. In this paper, temporal and spatial variation of environmental energy in different gradients was analyzed. Its main conclusions are as follows:Firstly, On the scale of day, the average daily radiation flux was QuL(34.53 MJ·m-2·d-1) >RDL(32.59 MJ·m-2·d-1)>>(10.26 MJ·m-2·d-1)>Qr(0.80 MJ·m-2·d-1). All of the monthly gross radiation flux fluctuated in single apex in a year except QDL·The average diurnal processes of Q and Qr presented peak type curves, however the processes of QDLand QuLpresented wave curves. In both of this two type of time scales, the variation coefficient (CV)of longwave radiation fluxwas obviously less than that of shortwave radiation flux. When the waves of radiation were the same, the variation coefficient of upwelling was less than that of the downwelling. On the scale of day, reflectivity fluctuated in a U-shape in a day, and at night that was more stable than of daylight. The average reflectivity of Chinese Fir Plantations was 8.0% in2008. Reflectivity of dry season was less than that of the rainy season, and its volatility was greater. At different time scales, the main effect factors of the characteristics of solar radiation flux and reflecting were different. Therefore, we should take account of scale effects, while analyzing the characteristics of solar radiation and the inter-relationship of different radiation flux.Secondly, the annual total global solar radiation in the Chinese fir plantation ecosystem was 3844.97 MJ·m-2. Thereinto this value in rainy season was 2537.06 MJ·m-2, proportionately 66.0%, meanwile, the dry season was only 34.0%, to 1307.91 MJ·m-2. Total annual net radiation was 2828.02 MJ·m-2, and that in the rainy season accounted for the total value 69.4%, so its value was much higher than the dry season. Moreover, effective radiation and reflected radiation respectively were 710.42 MJ·m-2 and 288.09 MJ·m-2, and they respectively accounted for the total value 51.1% and 70.0% in the rainy season.For the annual distribution rate of solar radiation, long-wave radiation of forest ecosystems was the largest (23.5%), followed by effective terrestrial radiation, whose percent was 19.0%, and the percentage of reflected radiation was only 7.5%. Distribution rate of solar radiation in different seasons are different, reflected radiation and net radiation in dry season were more than those in rainy season, On the contrary, effective radiation in dry season was more than that in rainy season.Thirdly, we could know that potential energy increased with height from the definition of potential energy. Whereas the maximum distance from the ground of three selected spatial levels was only 32.5m, so the potential energy generated by the gravity was very small. Therefore, the total position energy was almost composed of the internal energy. Internal energy and total position energy of B-layer were maximum in all three layers, what in C-layer were the secondary. Annual changes of the above three kinds of environment energy are single-peak curve. it standed for the value in summer were max winter minimum.When it comes to wind speed and kinetic energy, from bottom to top the its value increased with height, C-layer average wind speed was up to 1.175m/s. Those were inseparable from the weakening role of the wind speed of the canopy layer, while also shows that kinetic energy is passed down from the atmosphere above.Fourthly, temperatures and of B-layer were the highest in the three levels, so we could know that forest canopy became a direct heat source, and played a role as bridge in the process of the solar radiation into appearance heat energy. The latent heat at different levels in summer were all more than that in autumn and spring, meanwhile that in winter was the lastest. Addition to the role of canopy interception to rainfall, latent heat was also affected by transpiration of trees and the evapotranspiration of woodland. The latent energy and appearance heat energy summed to the warm-wet energy, and similar with latent heat, the warm-wet energy were the maximum in the summer, minimum in winter. This is mainly caused by the following reasons. On the one hand, the solar radiant energy as the resource of warm-wet energy could be much less in winter than in summer. On the the other hand, forests were a period of dormancy in winter, so transpiration were slow, While the evaporation capacity of the environment is also weak, providing a relatively small amount of water vapor.This study analyzed radiation balance and environmental energy in the upper canopy space in Chinese fir forest. The reaserch results not only provided a basis for the theoretical methods in water and carbon balance study involving such issues, at the same time it also provided a theoretical basis to determine the thermal structure in the area of water optimization model and improve the microclimate of the region. And seeking suitable for the growth of the energy ratio of Chinese fir was in order to reforestation and management plantations and to provide an important basis for sub-structure measurement. Furthermore, theoretical basis could be provided for how to assess the ecological benefits of plantations.