典型沙生灌木生态系统凝结水量估算

郭晓楠; 查天山; 贾; 昕; 杨强; 穆家伟; 刘鹏

doi:10.13332/j.1000-1522.20160017

摘要: 当前对干旱半干旱过渡带生态系统凝结水量的估算及其年际变化的认识仍十分有限。本研究以宁夏盐池沙生灌木生态系统为对象,运用微型蒸渗仪、涡度相关(eddy covariance,EC)法和Penman-Monteith公式对凝结水进行测定和估算,以求探索涡度相关法和Penman-Monteith公式估算凝结水的准确性,并且分析凝结水季节和年际变化、其对生态系统水量平衡的贡献及降雨对凝结水的影响。结果表明:1)以微型蒸渗仪观测结果为对照标准,涡度相关法因在夜间存在严重的能量不闭合会造成凝结水严重低估,而Penman-Monteith公式可以较准确地估算凝结水量(R2 =0.94,P0.05);2)采用Penman-Monteith公式估算2012—2014年凝结水,日平均凝结水量为0.14±0.08 mm,年平均凝结水发生天数为259 d/a,估算2012—2014年凝结水年总量分别为46、33和29 mm。凝结水多发生在夏秋季。2012—2014年降雨年平均量为301 mm。凝结水年均总量是平均降雨总量的12%。3)降雨时与降雨后一天凝结水成显著正相关关系(R2=0.81, P0.05)。2012—2014年≥20 mm的降雨次数占全年总降雨次数百分比分别为10%、5%和3%,≥20 mm的降雨能够为空气提供较多水分,增加凝结水量。因此≥20 mm降雨次数占全年总降雨次数的百分比将显著影响当年凝结水总量。结果证实,虽然凝结水总量年际差异较大且占降雨的百分比较小,凝结水是维持荒漠生态系统功能的重要稳定水源。

Abstract: Estimation of dewfall amount and its interannual variation in arid and semi-arid transitional ecosystems are still limited. Microlysimeter, eddy covariance (EC) method and Penman-Monteith equation were used to calculate the dewfall amount in a desert shrub ecosystem in Yanchi Research Station, Ningxia, Northwest China. The objectives of this study were to explore the accuracy of EC and Penman-Monteith equation in dewfall estimation, to analyze the seasonal and interannual variations of dewfall amount, the contribution of dewfall amount to the water balance of the ecosystem and the influence of rainfall on dewfall. The results indicated that: 1) taking the results observed by microlysimeter as a control, EC method could lead to a substantial underestimation of dewfall amount because of its low energy closure at night, but the Penman-Monteith equation could precisely estimate dewfall amount (R2 = 0.94, P0.05). 2) Dewfall amount during 2012—2014 was estimated by the Penman-Monteith equation. Mean daily dewfall amount (during 2012—2014) was 0.14±0.08 mm, average number of dewfall days was 259 days per year, dewfall amount in the years 2012 to 2014 was 46, 33 and 29 mm, respectively. Dewfall occurred more frequently in summer and autumn. The average annual rainfall amount during 2012—2014 was 301 mm. The average annual dewfall amount accounted for 12% of the average annual rainfall. 3) Rainfall and the dewfall amount on the day after rainfall showed a significant positive relationship (R2=0.81, P0.05). The percentage of ≥20 mm rainfall events accounted for 10%, 5% and 3% of the yearly total rainfall events in the years 2012 to 2014, respectively. Rainfall larger than 20 mm could add more water vapor in the air, thus increasing dewfall amount. Thereafter the percentage of ≥20 mm rainfall events to the yearly total rainfall events would significantly influence the annual dewfall amount. The results prove that dewfall is an important and stable water resource to maintain the function of desert ecosystem system despite of its large interannual differences and relatively small percentage in rainfall.

典型沙生灌木生态系统凝结水量估算

Estimation of dewfall amount in a typical desert shrub ecosystem.