作 者 ：阎百兴*,徐莹莹,王莉霞
期 刊 ：生态学报 2010年 30卷 20期 页码：5577~5584
关键词：农田生态系统；露水强度；露水量；垂直变化；三江平原；
Keywords:farmland ecosystem, dew intensity, dewfall, vertical variation, the Sanjiang Plain,
摘 要 ：露水是农业生态系统水分平衡、养分循环不可忽视的输入项。在对露水相关参数设定的基础上进一步探讨农田露水的凝结规律。选择杨木棒做为露水收集器，在三江平原于作物生长季(6月初—9月末)对水稻、玉米和大豆茎叶上的露水凝结进行了实地监测。结果表明：生长季农作物约70%的无雨夜间有露水凝结，年露日数约为70 d；7、8月份作物露水强度最强，丰水年露水强度显著强于平水年（P<0.05），水稻和大豆的露水强度基本持平，显著高于玉米露水强度（P<0.05）；垂直方向上各作物露水凝结规律一致，冠层露水强度强于顶层，底层露水强度最弱；农作物露水量较为可观，旱田作物年露水量保守值约为10—15 mm，水田作物年露水量为旱田的2—3倍，叶面积指数（LAI）成为限制作物年露水量的关键因子。此外，露水对水田喷洒叶面肥等农业生产活动有指导意义，在旱田作物抗病虫害、集水抗旱方面具有重要生态意义。
Abstract:As a significant part of water balance, dew has attracted great interest and has been extensively studied. Dew is a crucial input for water balance and nutrients cycling of farmland ecosystem. Dew could play important role in spaying leaf fertilizers in paddy and drought-resisting and preventing the disease and pest in rain fed land. In this study, a series of parameters about dew characterization including Dew Days, Dew Frequency, Dew Intensity and Dewfall were defined comparing to parameters describing the precipitation. Based on these parameters dew condensation was measured in a farmland in Sanjiang Plain. In order to discuss the condensation law of dew, Dew Intensity was monitored in situ on stem and leaf of plant in paddy, soybean and corn fields during the growing season form early of June to late September in 2008 and 2009. The experiment was organized at the Sanjiang Mire Wetland Experimental Station (47°35′N, 133°31′E), Chinese Academy of Sciences, located in Tongjiang, Heilongjiang Province, Northeast China. Dew was collected by wood sticks made with poplar tree. The collector was daily weighted at sunset and sunrise with an electronic balance (accuracy is within 0.001 g). For each experiment, the collectors were set on the bottom (5 cm above the surface level) and canopy of the plant, respectively. The results indicated that dew occurred about 70 days in a year and Dew Days accounted about 70% non-rain nights in the farmland. The maximum Dew Intensity occurred in July and August. Statistical analyses were carried out to compare the Dew Intensity. Analysis of variance of Dew Intensity was performed using one-way analysis of variance (ANOVA) and the significance was set at P<0.05. The Dew Intensity in 2009 was significantly larger (P<005) than that in 2008 because the rainfall in 2009 was much more abundant than that in 2008. The Dew Intensity on paddy and soybean plants were almost equivalent, but the Dew Intensity on corn plant was significantly (P<0.05) lower than those on paddy and soybean plants. The vertical condensation laws of dew on various plants were similar. The Dew Intensity was maximum at the canopy, the second was at the height that was 50 cm over the canopy, and the minimum occurred at the ground level. Dew plays an important role in the water balance of farmland ecosystem. The factual Dewfall in unit field area was calculated by the factors of leaf area index (LAI), Dew Days and Dew Intensity. The annual Dewfall showed a distinct variety of the amount between paddy and rainfed land. The annual dewfall in rainfed land ranged from 10 mm to 15 mm. In the paddy Dewfall was about two to three times larger. The Dewfall increases rapidly when rainfed land reclaimed into paddy. LAI was the determining factor that affected the annual dewfall. Otherwise, the formula for calculating Dewfall offered a reliable way to analyze dewfall data in farmland ecosystem. Most importantly, dew parameters, which were defined for the first time, provide a more precise way to describe and study dew.
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