九段沙芦苇湿地生态系统N、P、K的循环特征

对九段沙(上沙、中沙、下沙)芦苇湿地土壤、植物中N、P、K含量进行了测定,研究其分布规律.结果表明:水平分布上,湿地土壤全量养分与速效性养分含量均是中沙最低,并以中沙为中心向两端递增,速效性养分的这种变化尤为显著.垂直分布上,土壤全N和全K含量的分布规律一致,为上层＞下层＞中层;全P含量分布为中层＞上层＞下层.速效N含量分布为上层＞中层＞下层;速效P含量上层土壤最高,中、下层土壤含量因湿地类型而异;速效K含量多以中层土壤最低,上、下层土壤含量变化不稳定,以不同湿地而异.不同芦苇湿地的土壤速效性养分含量差异显著大于全量养分的差异,0～60 cm深度土壤的全量养分和速效性养分含量排序均为K＞N＞P.中沙湿地植物中养分含量最低,与土壤中营养元素总体水平分布一致;多数芦苇湿地植物中营养元素含量排序为N＞K＞P,与土壤养分含量排序不一致.不同芦苇湿地的吸收系数排序均为N＞P＞K;芦苇湿地利用系数排序为P＞K＞N;循环系数排序为N＞K＞P.

Characteristics of N,P and K cycling in Phragmites australis wetland ecosystem in Jiuduansha shoal of Shanghai

The study on the contents and distribution patterns of N,P and K in Phragmites australis wetland ecosystem in Jiuduansha shoal of Shanghai showed that horizontally,the contents of soil total and available N,P and K were the lowest at the middle section of the shoal,and increased gradually from the middle to the upper and lower sections of the shoal,being most notable for the available nutrients.Vertically,the contents of soil total nitrogen(TN) and potassium(TK) decreased in the order of upper layer > lower layer > middle layer,total phosphorus(TP) was in the order of middle layer > upper layer > lower layer,and available nitrogen(AN) was in the order of upper layer > middle layer > lower layer.Soil available phosphorus(AP) content was the highest in upper layer but differed in middle and lower layers in different wetlands,while available potassium(AK) content was the lowest in middle layer and changeful in upper and lower layers in different wetlands.The differences of soil available nutrient contents in different wetlands were greater than those of total nutrient contents.At the soil depth of 0-60 cm,both total and available nutrients were in the order of K>N>P.The nutrients content in plants was the lowest at the middle section of the shoal,which was consistent with that in soil.In most plants of P.australis wetland,the nutrients content was in the order of N>K>P,which was not inconsistent with that in soil.The absorption coefficient of nutrients in different wetlands was N>P>K,and the utilization coefficient was in the order of P>K>N.N had the greatest cycling coefficient,while P had the least one.