黄泛平原小网格农田林网的风场特征

有效控制黄泛平原风沙危害对于农业增产增收具有重要的意义,以山东省菏泽市鄄城县黄河滩区3种主林带林龄(分别为4 a、6 a和8 a)的等面积小网格(分别记为网格1、2、3)农田林网为研究对象,通过空间多点观测,研究网格内风场的空间分布特征及其防护效能。结果表明:主林带树高或林龄对林网内风速的变化有较大影响,防风效能和防护面积随着主林带树高的增加而增大。林网内风速的半方差函数分析表明,3种网格内风速理论变异模型分别为高斯模型、球型模型和球型模型,而且有强烈的空间自相关性,其自相关性大小和空间连续性与主林带林龄密切相关,表现为网格1<网格2<网格3。以降低风速30%～50%为标准确定有效防护面积,3种网格的平均有效防护面积比分别为31.0%、40.7%和46.7%。总体上,相同面积林网的防护效能随林带树高增大而增大。研究成果可为农田林网的可持续经营提供理论依据。

Wind field characteristics of small farmland shelterbelt network in Yellow River floodplain

Controlling wind-sand disaster plays an importance role ininereasing agricultural productivity effectively in Yellow River floodplain area. The spatial distribution characteristics of wind field and protective effectiveness of three same size farmland shelterbelt networks, named network 1,2 and 3, with different main forest belt ages （ i. e. 4 a, 6 a and 8 a） , were analyzed by multi-point observations in lowland of the Yellow River in Juancheng County, Heze City, Shandong Province. The results indicated that the main forest belt height and age had strong influences on the wind speed within the forest networks and their wind-break function and wind-break area increased with the main forest belt height increasing. The wind speed analysis of semivariance results in 3 forest networks showed that their variation models of wind speed were Gaussian model, Spherical model, and Spherical model, respectively, and there were strong spatial autocorrelations, in addition, the magnitude of autocorrelation values and spatial continuities were strongly related with the main forest belt ages, which performed as forest network 1 〈 network 2 〈 network 3. With the standard of reducing wind speed 30% - 50% , the average effectiveprotective area ratios of the 3 forest belt networks were defined as 31.0% , 40.7% , and 46.7% , respectively. Totally, the overall protective function of networks increased with the tree height increasing. These research results could provide the theory basis for improving the sustainable management of farmland shelterbelt network.