宁夏盐池沙地农田防护林的防风阻沙效益

对宁夏盐池北部沙区典型农田防护林防风效能和阻沙效益的实地观测结果表明,小叶锦鸡儿(Caragana microphylla)灌木片林防护范围主要在林内和背风面距背风林缘0～3H(H表示树高)内,而背风面有效防护范围较小;沙柳(Salix psammophila)灌丛林带的迎风面和背风面风速均处于起沙风速(4.53 m·s-1)以上,对农田不能形成有效防护;榆树(Ulmus pumila)乔木林带残缺不全,严重影响防风效益.沙柳林带和榆树林带都是林带背风面大量积沙,未能有效地将风沙流中的来沙阻挡在农田以外;小叶锦鸡儿片林阻沙主要分布在林内,表明其能对农田形成有效防护.

Effects of Farmland Shelterbelts in Controlling Wind and Sand in Sandy Land of Yanchi

Field observation on effects of typical farmland shelterbelts in controlling wind and sand in the sandy land of Yanchi in Ningxia revealed that the shelterbelt of Caragana microphylla shrubberies provided shelter over the woodlot per se and 0-3H (H stands for height) at the leeway edge of the forest,with a limited effective range in the leeway;that the wind speeds at both windward side and leeward side of the shelterbelt of Salix psammophila were greater than the threshold velocity(4.53 m·s-1)of sand rising,so the shelterbelt gave little protection of the farmland;and that the fragmentary shelterbelt of Ulmus pumila,was unable to play its wind-breaking role.Sands accumulated on the leeway side of the latter two shelterbelts,indicating that they could not effectively prevent aeolian sands from coming into the farmland,while sands arrested inside the belts of Caragana microphylla,showing its effectiveness in controlling aeolian sands.