两种河岸缓冲带对径流水中磷的截留效果

Effect of two riparian buffer strips on phosphorus elimination from runoff water

为更好地了解不同宽度和密度人工林河岸缓冲带对径流水中磷的截留效果,减少污染物进入水体,减缓太湖农业面源污染,以流域6块大小为20 m×40 m的中山杉与杨树人工林河岸缓冲带为研究对象,分析不同宽度(15、30和40 m)和不同林分密度(400、1 000和1 600株·hm^(-2))的河岸缓冲带对径流水中总磷与可溶性磷的截留效果。结果表明:(1)不同的人工林河岸缓冲带具有不同的优化宽度,15 m宽的中山杉林缓冲带和30 m宽的杨树林缓冲带基本能满足截留磷的要求。(2)不同林分密度中山杉林缓冲带对总磷和可溶性磷的平均截留率分别表现为:1 000株·hm^(-2)>400株·hm^(-2)>1 600株·hm^(-2)和1 600株·hm^(-2)>1 000株·hm^(-2)>400株·hm^(-2);林分密度为400株·hm^(-2)的杨树林缓冲带对总磷平均截留率最高,为87.97%;林分密度为1 600株·hm^(-2)的杨树林缓冲带对可溶性磷的平均截留率最高,达到99.42%。(3)不同林分密度下,中山杉林对总磷的截留率均高于杨树林,但差异不显著;1 600株·hm^(-2)的中山杉林缓冲带对可溶性磷的平均截留率显著高于杨树林(P<0.05)。林分密度为400株·hm^(-2)时,杨树林缓冲带对可溶性磷的平均截留率高于中山杉林。15 m宽1 000株·hm^(-2)的中山杉林缓冲带能有效减缓太湖农业面源污染。

The aim of this study was to investigate the efficiency of plantation riparian buffer strips of different widths and densities in removing phosphorus in runoff water to reduce pollutants in water and mitigate agricultural non-point source pollution in Taihu Lake. We examined six buffer strips(20 m × 40 m) of Taxodium ‘Zhongshanshan’ and poplar plantations in the Taihu Lake area. The effects of riparian buffer zones with varying widths(15, 30, and 40 m) and densities(400, 1 000, and 1 600 tree·hm^(-2)) on the removal of total phosphorus(TP) and dissolved phosphorus(DP) from runoff water were evaluated. The results showed that:(1) the optimum width of riparian buffer strips differs between plantations. A 15 m wide buffer zone of Taxodium ‘Zhongshanshan’plantation and a 30 m zone of poplar plantation is sufficient for trapping phosphorus.(2)The average retention rates of TP and DP in the buffer zone of Taxodium ‘Zhongshanshan’ plantation with the different stand density were 1 000 tree·hm^(-2)>400 tree·hm^(-2)>1 600 tree·hm^(-2)and 1 600 tree·hm^(-2)>1 000 tree·hm^(-2)>400 tree·hm^(-2), respectively. The average retention rate of TP was 87.97% in the poplar buffer zone with 400 tree·hm^(-2). When the stand density was 1 600 tree·hm^(-2), the average retention rate of DP in the poplar plantation buffer reached 99.42%.(3)At different stand densities, the retention rate of TP was higher in Taxodium ‘Zhongshanshan’ plantation than in poplar plantation, but the difference was not significant. The DP retention rate in the buffer zone of 1 600 tree·hm^(-2)in Taxodium ‘Zhongshanshan’ plantation was significantly higher than that of poplar plantation(P<0.05). When the stand density was 400 tree·hm^(-2), the average elimination efficiency of DP in the buffer zone of poplar plantation was higher than that in Taxodium ‘Zhongshanshan’ plantation. The Taxodium ‘Zhongshanshan’ plantation buffer strip with a width of 15 m and 1 000 tree·hm^(-2)can effectively reduce agricultural non-point source pollution in Taihu Lake.