无瓣海桑和秋茄人工林的减风效应

Wind-attenuation effect of Sonneratia apetala and Kandelia obovata plantations

以海南东寨港三江湾无瓣海桑和秋茄人工林为研究对象,观测红树林内距向海林缘50m、地面以上2m高处的风速、风向特征,研究红树林的减风效应.结果表明:无瓣海桑和秋茄人工林均对偏北方向由海向岸的风速有明显的减弱效应,林带内50m处的平均风速减低85%以上,并且秋茄林的减风效应更显著.随着风速的增加,林分的减风效能呈先下降后平缓的趋势.当风速低于5m·s-1时,无瓣海桑人工林内50m处的平均风速减低89.8%;当风速在10m·s-1以上时,其风速减低率趋于稳定;当风速>15m·s-1时,平均风速减低58.9%～63.6%.与冷季相比,无瓣海桑人工林暖季的减风效应更显著.在台风等极端天气状况下,无瓣海桑人工林内50m处的平均风速和极大风速分别减低59.4%和53.2%.

A field monitoring was conducted to examine the wind-attenuation effect of mangrove plantations at the Sanjiang Bay of Dongzhai Harbor,Hainan Province of South China.The wind speed and wind direction were measured at a site 50 m away from the offshore forest fringes of Sonneratia apetala and Kandelia obovata plantations and 2 m above the ground.Both the S.apetala and the K.obovata plantations had obvious effect in attenuating the speed of the wind from northerly to the shore,with the mean wind speed decreased by 85% and the better effect of K.obovata plantation.With the increase of the wind speed,the wind-attenuation effect of the plantations presented a trend of decreasing first and remained stable then.At 50 m away from the offshore forest fringe of S.apetala plantation,the wind-attenuation rate was higher than 89.8% when the mean wind speed was lower than 5 m·s-1,tended to be stable when the mean wind speed was 10 m·s-1,and turned to be 58.9%-63.6% when the mean wind speed was higher than 15 m·s-1.The S.apetala plantation had better wind attenuation effect in warmer season than in colder season.Under the extremely adverse weather like typhoon,the mean wind speed and extreme wind speed at 50 m away from the offshore forest fringe of S.apetala plantation were decreased by 59.4% and 53.2%,respectively.