林带对太湖地区农业非点源的控制效应研究

太湖地区是高度发达的农业生产区之一,大量使用化肥和杀虫剂加重该地区的环境污染水质污染。本研究选择以油菜-水稻和小麦-水稻为轮作方式的两片农田为农田生态系统,5年生的杨树林带和8年生的水杉林带为研究对象,通过采集水体、作物、林地下的氮和磷的样本,对农田生态系统中 N、P等(主要水污染物)迁移和淋失进行了研究,并对林带作对农业非点源污染的控制效应进行了分析。结果表明:农田生态系统中 N、P等迁移、淋失状况随轮作方式、作物种类及施肥状况而变化;农田与沟渠间的缓冲林带具有截留和净化土壤径流中的N、P等物质的作用,从而在一定程度上控制农业非点源污染。研究表明:当农田与林带宽度比例为100∶40时,在油菜-水稻轮作方式下,50.05%流失N和29.3% 的流失P可以被林带所吸收, 在小麦-水稻的轮作方式下,30.98 %流失N和86.73% P可以被林带所吸收;当农田与林带宽度比例为150∶40,在油菜-水稻轮作方式下, 33.7%流失N和19.58%P可以被林带吸收,在小麦-水稻的轮作方式下,20.65%流失N和57.82% 流失P可以被林带所吸收。因而,农田与林带宽度比例100∶40或150∶40较为合理,这种模型既能少占耕地,又能净化水质、保护生态环境。杨树生长快、用途广,适于太湖地区营造水环境保护林带。图2表4参8。

Controlling effects of forest belts on non-point source pollution of agricultural lands in Taihu Lake area, China

Taihu Lake area is one of the most developed areas in agricultural production. Application of fertilizers and pesticides in large quantities greatly aggravate environmental pollution of this area, and water pollution has worsened to an unbearable condition. Two sampling farms (respectively 1 hm2) under rape-rice rotation and wheat-rice rotation were selected as studied ecosystem and a 5-yr-old Poplar forest and 8-yr-old Metasequoia forest were chosen in the selected areas. By collecting samples of Nitrogen, Phosphorus in water, crops and underground of forest, the transfer and loss of N and P (main water pollutants) in faming ecosystem were studied, and the effects of forest belts on non-point source pollution of agricultural lands was analyzed. The results indicated that the transfer and loss of N and P vary with means of rotation, types of crops and the amount of fertilizer application. Buffering forest belts betweens farmlands and ditches can effectively stop and purify such elements as N and P in soil runoffs, thus controlling non-point source pollution of agricultural lands. When the width ratio of farmland to forest belt is 100 to 40, 50.05% losing N, 29.37% losing P can be absorbed by forest under rape-rice rotation and 30.98% N, 86.73% P can be absorbed by forest under wheat-rice rotation. When the width ratio of farmland to forest belt is 150 to 40, 33.37% losing N, 19.58% losing P can be absorbed by the forest under rape-rice rotation, and under wheat-rice rotation 20.65% lost N and 57.82% lost P can be absorbed. There is only some purification effect when the width ration of farmland to forest belt is 200 to 40. Based on model of buffering forest belts, the width ratio of farmland to forest is determined between 100 to 40 and 150 to 40, because it not only can purify water, but also occupy less farmland. It is suggested that Poplars, with the characteristics of fast-growing and high value, are suitable to be planted as shelter-forest in Taihu Lake Watershed.