青藏高原三江源区人工草地能量平衡的变化特征

发布时间：2018-03-22 16:53

本文选题：青藏高原　切入点：反射率　出处：《生态学报》2017年15期 　论文类型：期刊论文

【摘要】：为揭示建植人工草地对青藏高原三江源区能量平衡的影响,利用涡度相关和微气象系统的观测数据定量分析了该区域人工草地能量收支及其各分量的变化特征。结果表明:太阳总辐射(R_s)和净辐射(R_n)的日最高值分别为33.6和19.1 MJ m~(-2)d~(-1),年累计值分别为6789.4和2773.3 MJ/m~2;全年R_n与R_s的比值(R_n/R_s)为0.41,但生长季的R_n/R_s(0.54)明显高于年均值;显热(H)与潜热(LE)通量呈明显的季节变化,H最低值出现在12月,之后随R_s的增强而增加,但进入生长季后呈下降趋势,7月中旬出现次低值;而LE在冬季维持较低值,3月以后迅速增加,最高值出现在生长旺季的7月。在能量分配上,可利用能量主要消耗于LE和H,年均LE/R_n,H/R_n,G/R_n分别为0.46,0.45和-0.13。但能量分配的季节变化差异明显,波文比(β=H/LE)在冬季、春季、夏季和秋季的平均值分别为3.33、0.68、0.42和1.29。受植被叶面积指数(LAI)等生物因素以及土壤含水量(SWC)、饱和水汽压差(VPD)等环境因素的共同影响,冠层导度(g_c)和解耦系数(Ω)的年最大值均出现在夏季,其平均值分别为16.22mm/s和0.70,表明在植被生长盛期LE仍受R_n的控制,其它季节Ω均值低于0.5,说明LE更多的是受VPD调控。本研究说明,虽然三江源区接收的太阳总辐射较强,但R_n/R_s相对较低,生态系统能量平衡中各分项的变化主要受植被、土壤含水量以及净辐射的控制,在退化草地恢复过程中,由于建植人工草地增加了植被覆盖度,进而改变了能量收支过程及能量平衡各分项。
[Abstract]:In order to reveal the effect of artificial grassland on energy balance in the source region of the three rivers in the Qinghai-Tibet Plateau, The variation characteristics of energy budget and its components of artificial grassland in the region were quantitatively analyzed by using vorticity correlation and micrometeorological system observation data. The results show that the daily maximum values of total solar radiation (Rss) and net radiation Rnn (Rn) are 33.6 and 33.6, respectively. The annual accumulative values were 6789.4 and 2773.3 MJ / m-1, respectively, and the ratio of Rn / Rs was 0.41 in the whole year, but the Rn / RsS 0.54 in the growing season was significantly higher than the annual average. The flux of sensible heat (H) and latent heat (LEL) showed obvious seasonal variation. The lowest value of H appeared in December, then increased with the increase of Rs, but decreased after entering the growing season, and the next low value appeared in the middle of July. But le maintained a low value in winter and increased rapidly after March. The highest value appeared in July of the growing season. In energy distribution, the available energy was mainly consumed in le and H.The average annual LER / RnS / R / R _ n was 0.46 / 0.45 and -0.13 respectively. However, the seasonal variation of energy distribution was obvious. The average values of 尾 -H / L ratio in winter, spring, summer and autumn were 3.33 ~ 0.68 ~ 0.42 and 1.29 respectively, which were influenced by biological factors such as vegetation leaf area index (Lai), soil water content (SWC), saturated vapor pressure difference (VPD) and so on. The annual maximum values of canopy conductance and decoupling coefficient (惟) appeared in summer, with the average values of 16.22mm/s and 0.70, respectively, indicating that le was still controlled by RC during the peak period of vegetation growth. The mean value of 惟 in other seasons is lower than 0.5, which indicates that le is more regulated by VPD. This study shows that although the total solar radiation received in the source region of the three rivers is stronger, the R_n/R_s is relatively low, and the changes in the energy balance of the ecosystem are mainly affected by vegetation. Under the control of soil water content and net radiation, the vegetation coverage was increased due to the establishment of artificial grassland, which changed the process of energy budget and energy balance.
【作者单位】：南开大学生命科学学院;中国科学院西北高原生物研究所;
【基金】：国家自然科学基金项目(31570478)
【分类号】：S812

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