【作者】 张敏；

【导师】 张社奇；

【作者基本信息】 西北农林科技大学 ， 生物物理， 2008， 硕士

【摘要】 本文选取黄土地区主要绿化植被—油松为研究对象,采取辐射表野外定点观测的方法,研究了在典型天气条件下油松冠层内的太阳辐射能量日变化、生长季不同生长阶段的日值特征,以及辐射能量在空间和时间上的分布规律,为充分利用太阳辐射能、提高油松植被生产力以及干旱半干旱区特殊环境下的植被恢复提供了理论依据。其主要结论如下:(1)在晴朗天气条件下,油松生长季内的冠层总辐射、净辐射日变化为规则的单峰变化规律。具体表现为:在日出、日落时,太阳高度角最小,太阳辐射出现零值;中午13:00左右,太阳高度角最大,出现峰值。晴朗天气下净辐射率的日变化趋势总体上为中午高,早晨和夜晚低,日间净辐射率较为稳定,各生长阶段净辐射变化差异较小,一般保持在77%～84%之间。(2)在多云天气条件下,由于受云量等因素的影响,油松生长季内的冠层总辐射、净辐射总体上呈多峰变化规律,变化总趋势为早晚低、中午高。但在不同生长阶段的总辐射、净辐射受天气影响较大,导致辐射峰值出现的时间不同。相对于晴天条件,辐射能的起伏变化更为显著,并且在某些时刻出现了小的辐射峰值。净辐射率变化范围在26%～89%之间。(3)总辐射在不同层次表出垂直分层,而且具有一定规律性。太阳总辐射和净辐射随垂直高度的降低总体上表现为显著的递减规律。树冠顶部的太阳辐射强度最大,随着高度的降低,辐射强度随之减弱,且从树冠表面到树冠底部太阳总辐射可递减50%～70%。油松冠层对太阳辐射起到了较为明显的截流和削弱作用。(4)冠层内的太阳辐射有着明显的取向规律,并且不同取向表现出明显的分异规律。从每天8:00起,树冠内辐射由东向西呈递减趋势,随着时间的变化,东西向差异明显缩小;中午13:00以后,随着太阳西斜,树冠内辐射分布逐渐转向由西向东逐渐下降的趋势;16:00以后两者差值又逐渐增大。在整个生长季不同的生长阶段表现出相同的规律,且南北向的差异比东西方向的差异要明显的多。(5)林分环境对辐射能的分布也有一定影响。由于所测量的油松树冠北边的枝叶密度远小于南边,使得测量出的辐射在一天内大于南边辐射值。当太阳高度角最大时,南北向的差异也达到最大。(6)油松冠层红外辐射的日变化趋势和总辐射变化规律相似,呈现出有规律的单峰变化规律。在日出、日落时,太阳辐射值比较小;中午13:00左右时太阳高度角最大,出现峰值。受天气状况和林分环境的影响,数据有一些波动。整个生长季总体上表现为单峰变化规律,只是由于太阳高度角的变化,辐射的峰值大小及其出现的时间有所不同,在生长季中期辐射值最大,末期次之。更多还原

【Abstract】 In this paper, the Pinus tabulaeformis which is the main afforest vegetation in loess areas are selected for study, the method of field fixed-point observation by radiometer is used , the writer researched on the daily solar radiation energy changes of Pinus tabulaeformis canopy layer on typical weather, the daily value feature in different stages of the growing season, and the distribution of radiation energy in space and time. This paper provided a theoretical basis for making full use of solar radiation energy, improving Pinus tabulaeformis vegetation productivity and restoring the vegetation in the arid and semi-arid areas under special circumstances. Its main conclusions are as follows:Firstly, in the sunny weather conditions, the daily changes of the canopy layer’s total radiation and net radiation are regular single peak changes in the growing seasons. For the specific performances: the solar elevating angle is minimum and the solar radiation is in zero when sunrise or sunset; the sun’s elevating angle is maximum and has a value peak around 13:00 at noon. In the sunny weather conditions, the ratio of net radiation’s daily changes trends are as follows: it is high at noon and it is low in the morning and at night, the net radiation during a day is relatively stable, the net radiation changes less differences in different stages of the growing seasons, it generally maintains between 77%~84%.Secondly, in the cloudy weather conditions, for the impact of other factors, such as the clouds, the changes of the canopy layer’s total radiation and net radiation are multimodal changes regularity in the growing seasons, the general trend for change is lower in the morning or at night and higher at noon. But the weather has a greater impact on total radiation and net radiation in the different growing seasons; as a result, the peaks of radiation occur at the different time. Comparing with the sunny weather conditions, the change of the radiation is more significant, and it has a small value peak of radiation in some moments. The ratio of the net radiation has changed in the range of 26% to 89%.Thirdly, as the vertical height decreases, the changes of the total solar radiation and net radiation are of diminishing significantly. At the top of the canopy, the solar radiation intensity is maximization, the radiation will be weakened with the vertical height decreased, and the total solar radiation can be reduced 50 to 70 percent from the surface of the leaf canopy to the bottom of the leaf canopy. The leaf canopy plays a more significant role in the stop-flow and weakening the solar radiation.Fourthly, the solar radiation in the leaf canopy has a clear orientation rule, and different orientations show a law with clear differentiation. Since from the day at 8:00, the solar radiation in the leaf canopy has a descending trend from east to west, the difference between East-West significantly decreases with the time changes; after about 13:00 at noon, the solar radiation in the leaf canopy gradually has a descending trend from west to east at sunset; after 16:00, the margin also gradually increases. During the whole growing seasons, these different stages show some same rules, but the differences between South-North are more clearly than the differences between East-West.Fifthly, stand environment affects on the distribution of radiation energy too. Because the branches density at the north side of the test place is much smaller than the south’s, the measuring values of radiation in the north in one day is larger than in the south. North-south differences also reached to the maximum when the solar elevating angle of the sun is maximization.Lastly, the daily changes of the infrared radiation in the leaf canopy are similar with its total changes regularity, and it shows a regular single peak change. The solar radiation value is small at sunrise or sunset; the elevating angle of the sun is maximization; and it has a peak value around 13:00 at noon. Dates have some fluctuations because of weather conditions and stand environments. The whole growing seasons show the single peak changes regularity. Just because of the changes of the solar elevating angle, the radiation peak values and the time are different; the value of radiation is the largest in mid-stage of the growing seasons, then the second -largest at the end of the growing seasons.更多还原