鼎湖山针阔混交林旱季能量平衡研究

Dry Season Energy Balance of a Coniferous and Broad-leaved Mixed Forest at Dinghushan Mountain, Southern China

运用涡度相关(Eddy covariance,EC)法开路系统、常规微气象观测系统及土壤热通量板等设施对鼎湖山季风常绿阔叶林旱季(2003/1/9-2003/1/23)的能量分量进行测定。结果表明,平均净辐射通量(Netradiation,Rn)为53.14Wm-2,与下行短波辐射具有相同的变化趋势。林冠上层EC法潜热通量(Latentheat,LE)、显热通量(Sensibleheat,Hs)实测平均值分别为57.18Wm-2、43.40Wm-2,林冠下层分别为12.61Wm-2、7.61Wm-2。白昼EC法所测得的LE和Hs数据与利用波文比-能量平衡法(Bowenratioandenergybalance,BREB)计算出的数据相比,略偏低,而夜间及凌晨数据差异较大。土壤热通量日变化曲线呈“S”形,平均土壤热通量为-1.50Wm-2,表面土壤总热通量(Gt)仅为5cm处土壤热通量的84.0%,可见表层土壤尽管很薄,但其热储量不能忽略。将LE、Hs之和与可供能量(Rn-Gt)进行闭合,回归直线斜率为0.9128,相关系数达0.8517,与许多研究结果的60%-90%的区间相符,这说明鼎湖山涡度相关法通量观测数据是非常可靠的。

Net radiation and heat fluxes in a coniferous and broad-leaved mixed forest were monitored by a microclimate monitor system, an eddy covariance (EC) open-path system, and soil heat flux plates during January 9-23, 2003 in Dinghushan Mountain, Southern China. The average net radiation (Rn) above the canopy was 53.14 W m-2. The average latent heat flux (LE) and sensible heat flux (Hs) above the canopy were 57.18 W m-2 and 43.40 W m-2, while the LE and Hs below the forest canopy were 12.61 W m-2 and 7.61 W m-2, respectively. The LE and Hs fluxes estimated by the EC and by the Bowen ratio energy balance method were very similar in daytime, but very different in the rest of the day. The diurnal changes of soil heat flux (Gt) were in an 'S' shape. The average Gt was -1.50 W m-2,which suggested that soil was one of the heat sources. The total Gt was only 84.0% of the soil heat flux at 5 cm depth, which indicated that the heat stored by the soil should not be ignored in spite of the thin soil layers. A significant correlation (r = 0.8517) between the amount of heat flux (LE+Hs) and available energy (Rn-Gt) with a slope of 0.9128 suggested that the LE and Hs measured by EC at the research site were within the reasonable range reported in the literature.