安吉毛竹林生态系统水汽通量的变化特征

Variation characteristics of water vapor flux in Anji Phyllostachys edulis forest ecosystem

2012—2014年利用涡度相关技术观测安吉毛竹林生态系统的水汽通量,同时结合降雨量对该生态系统的水分收支数据进行比较,以揭示毛竹林的水分利用能力,进而为其水分管理提供理论指导。结果显示:2012—2014年毛竹林生态系统水汽通量均为正值,表现为较好的水汽源作用,7月份最大,12月最小;各年水汽通量分别为695.96、749.07和656.47 kg·m-2,并表现出明显的季节变化,即夏季最高,春秋季次之,冬季最低。3年中月降雨量与月蒸散量呈显著正相关(r=0.67,P<0.05);此外,各年降雨量和蒸散量均主要集中在6—8月。2012—2014年降水总量为2018、1509和1476 mm,5 cm土壤含水量分别为3.173、3.045和3.013 m3·m-3,水分利用效率分别为2.84、2.10和3.37 g·kg-1,且各年蒸散量分别占到全年降雨量的34.49%、49.66%和44.48%,表明毛竹林的径流量较大,水分利用效率较低。饱和水汽压差和环境温度对毛竹林水分利用效率有显著影响,表明水热资源分布的不一致是影响毛竹林水分高效利用的主要原因。因此,经营时要注意调节温度和湿度(即高温高湿或低温低湿),以提高毛竹林的水分利用及其产量,从而避免水资源的浪费。

To reveal the water use ability of Phyllostachys edulis and further provide theoretical guide for its water management, eddy covariance observation technology was used to obtain water vapor flux data and rain gauges were applied to gaine precipitation data of P. edulis forest ecosys- tem in Anji County, Zhejiang Province from 2012 to 2014. The results showed that water vapor fluxes were positive during 2012-2014, indicating the ecosystem was a good water vapor source for the atmosphere. Water vapor fluxes were 695.96, 749.07 and 656.47 kg ~ m-2 in 2012, 2013 and 2014, respectively. Meanwhile, the maximum value occurred in July, and the minimum in December. Water vapor flux presented a seasonal variation, being summer 〉 spring 〉 autumn 〉 winter （except spring 〈 autumn in 2014）. Monthly precipitation showed a good positive correla- tion with monthly evapotranspiration in the three years （ r = 0.67, P 〈 0.05 ）. In addition, both precipitation and evapotranspiration maximally occurred during the period from June to August. The total precipitation amounts were 2018, 1509 and 1476 mm in 2012, 2013 and 2014, soil moistures at depth of 5 cm were 3.173, 3.045 and 3.013 m3 m-3, and water use efficiencies （WUE） were 2.84, 2.10 and 3.37 g kg-1 , respectively. Annual evapotranspiration accounted for 34.49%, 49.66% and 44.48% of annual total precipitation for the three years, respectively, suggesting that the runoff of P. edulis forest was greater, with a lower WUE. Moreover, vapor pressure deficit and air temperature had significant effects on the WUE of P. edulis forest, which indicated that the asynchronization of water and heat was the main limiting reason of high WUE. It is recommended that the regulation of temperature and humidity （high temperature and high humidity or the opposite） should be conducted when managing the forest, so as to improve the WUE and production of P. edulis and avoid the waste of water resource.