【作者】 徐莹莹；

【导师】 阎百兴；

【作者基本信息】 中国科学院研究生院(东北地理与农业生态研究所) ， 环境科学， 2012， 博士

【摘要】 露水是湿地、农田生态系统重要的水分输入项，露水凝结量及水质对湿地植物和农田作物生长有重要影响。近60年来，三江平原经历了大规模的湿地垦殖过程，农田已成为主要的景观类型。下垫面的剧烈变化对露水凝结过程、露水水质及露水水汽来源的影响程度尚不清楚。本研究选择三江平原典型沼泽湿地（季节积水、常年积水）及农田（旱田、水田）为研究对象，监测了露水在植株表面的凝结情况，辨析了影响露水形成的主要因子，阐明了土地利用方式变化对露水量、露水水质及露水水汽来源的影响，得出以下结论：1)三江平原湿地和农田生态系统日落1.5小时后露水开始在植株上凝结，至次日凌晨日出前0.5小时时停止，生长季露水日凝结历时约6～8小时。2)8月份露水凝结量最大，露水量与夜间相对湿度、露点温度、水汽压呈正相关，与风速呈负相关。露水凝结最适宜的条件是风速在2.0m/s左右、水汽压高于9hpa、相对湿度在90%-95%、露点温度高于6℃。3)旱田作物植株表面露水凝结强度略低于沼泽湿地与水田。沼泽和农田生态系统冠层露水强度大于近地表层。水田植株上露水凝结量最多，年露水凝结量在30mm左右，为湿地和旱田露水量的2～3倍。4)常年积水沼泽露水的pH为6.42±0.23，未监测到酸露现象；露水中金属元素种类丰富，K含量为29531μg/L，Ag、Th、U、Be和Tl的含量低于0.03μg/L；露水中的K、Ca、Na、Mg、Mn、Fe和Zn浓度远高于当地雨水，露水为湿地植物生长提供了丰富的营养元素和微量元素；露水中金属主要来源于地表积水和大气干沉降。露水中Pb、Ba、Se、As、Co、Cr和Cu等微量元素含量极低，研究区环境空气质量良好。5)农田露水pH在5.36～7.00，均值为6.36，总体偏酸性。相比雨水，露水为作物提供了更多的有效态N、P。水田露水中NO₃^--N含量显著高于NH₄⁺-N（P<0.05）。露水是水稻重要的N、P输入源，7～9月通过露水凝结输入水田的NH₄⁺-N，NO₃^--N和PO₄^3--P量分别为0.10，0.22和0.04kg/hm²，高于叶面肥输入的有效态N、P量。6)应用稳定同位素方法，发现雨季水田露水中约30%的水分来自于水稻蒸腾和作物吐水，约70%来源于空气中水汽和田面水蒸发的水汽；湿地露水主要来源于地表积水蒸发的水汽。露水与雨水中氢氧同位素组成与含量变化同步，利用露水同位素信息可反映降雨水汽的来源。7)沼泽开垦为旱田后，露水量接近，旱田改为水田后露水量大幅度上升。LAI是影响生态系统露水量的关键因素。水田露水N、P含量低于湿地露水。水田与湿地露水水汽来源主体均为地表积水蒸发水汽。更多还原

【Abstract】 Dew is a crucial input for water balance and nutrients cycling of wetland orfarmland ecosystem. Dew could play important role in spaying leaf fertilizers inpaddy and drought-resisting and preventing the disease and pest in rainfed land andwetland. In the1960s, Sanjiang Plain was the largest concentrated area of freshwaterwetlands in China. Over the last60years, Sanjiang Plain was reclaimed four times.Most of its marsh wetland areas were turned into cultivated land. But it was still notclear that the process of dew formation, character of dew and vapor source of dewfrom different land types. Dew was monitored in situ on stem and leaf of plant inCarex lasiocarpa, Calamagrostis angustifolia, soybean or corn, and paddy fieldsduring the growing season from2008to2010. Method on dew condensationmonitoring in Wetland and farmland ecosystem was explored for the first time. Themethod including to set up a series of parameters about dew characterization, to selectthe proper collector, to identify the dew duration and to deduce the dewfall formula.The conclusions was list as following:1)Dew began to condense from one and a half hour after sunset and I reachedthe peak at about half an hour before sunrise. Dew duration was about6-8hours frommid-May to mid-October in mire wetland at Sanjiang Plain.2)Dew intensity reached peak at August. The higher relative humidity, dew pointtemperature, and vapor pressure were the important factors improving the dewintensity. In addition, wind speed is also a non-neglected factor. The dew productionin Carex lasiocarpa marsh more frequently occurred under the conditions of windspeed around2.0m/s, the water vapor pressure above9hPa; the relative humiditybetween90%and95%and dew point temperature above6℃.3)The annual Dewfall showed a distinct variety of the amount between paddyand rainfed land. The annual dewfall in rainfed land ranged from10mm to15mm. Inthe paddy Dewfall was about two to three times larger. The Dewfall increases rapidlywhen rainfed land reclaimed into paddy.4)pH of Carex lasiocarpa dew was6.42±0.23and the acid dew never occurredin the research area. Therefore, dew can not damage protective surfaces on leaves, interfere with guard cells and poison plant cells from the aspect of pH. The types ofmetal element in Carex lasiocarpa dew were abundant. K, Mg, Ca are the nutrientelements and Mn, Cu, Cr, Zn, Na, Mo, V, As, Fe, Ni are the trace elements. They wereall can be monitored in Carex lasiocarpa dew. The mean concentrations of Cd, Be, Co,Se, Mo, Th, U and Tl were below1.0μg/L. The mean concentrations of Pb, As, Ni, Cr,V, Ag, Cu and Zn were between1.0μg/L and100μg/L. The mean concentrations of00Na, Al, Fe and Ba were between100μg/L and1000μg/L. The meanconcentrations of K, Mg, Ca and Mn were higher than1000μg/L. Carex lasiocarpadew can provide nutrient elements and trace elements to plant. Dew can reveal the airpollution status and it is significant to monitor the chemistry character of dew. Thetrace amount of Pb, Ba, Se, As, Co, Cr, Cu in Carex lasiocarpa dew implied that thereis no automobile exhaust, coal combustion or industrial pollution in this area.5)pH was between5.36and7.0with a mean pH of6.36. Therefore, dew cannotdamage leaves in the paddy. The NO₃^--N concentration in dew was significantly（p<0.05） greater than NH₄⁺-N and PO₄^3--P concentrations. Dew can offer moreNH₄⁺-N, NO₃^--N and PO₄^3--P than rain. The deposition amount of NH₄⁺-N, NO₃^--Nand PO₄^3--P from July to October in paddy dew was0.10,0.22and0.04kg/hm²,respectively. This amount was much larger than the volume of foliar fertilization, withthe deposition amount of essential nutrients in dew close to100times as much as thatin foliar fertilization.6) Based on isotopic mass conservation to partition quantitatively thecontribution of different vapour sources of dew, the guttation and transpiration fromthe plant accounted about30%and the evaporation of surface water mixed withvapour in air accounted the other partition of paddy dew in rainy season. As towetland dew, the evaporation of surface water took the most patition. The δ18O andδD values of dew exhibited the similar trend to the stable isotope in rain. Therefore,the stable isotope value of dew is a useful indicator as vapour resource of rain.7)The Dewfall did not change too much when wetland reclaimed into rainfedland but increase rapidly when rainfed land reclaimed into paddy. LAI was thedetermining factor that affected the annual dewfall. N and P content was lower in paddy dew than it in wetland. The main vapor of dew in wetland and paddy was boththe vapor evaporated from surface water.更多还原