沉水植物分布格局对湖泊水环境N、P因子影响

INFLUENCES OF SUBMERGED MACROPHYTES DISTRIBUTION PATTERN ON NITROGEN AND PHOSPHOROUS FACTORS OF WATER ENVIRONMENT IN LAKES

利用实地调查数据模拟保安湖沉水植物分布及水环境生态因子场。应用GIS空间分析功能 ,分别空间选取四种优势沉水植物 (金鱼藻CeratophyllumdemersumL .,穗状狐尾藻MyriophyllumspicatumL .,微齿眼子菜PotamogetonmaackianusA .Benn .,及苦草VallisneriaspiralisL .)的分布水域及无沉水植物分布水域的局部生态因子场。根据得到的局部因子场特征 ,比较分析不同水生植物分布格局对水环境中N、P因子的影响。结果显示四种沉水植物的分布对水环境中N、P因子均有显著影响 ,但效果和强度有所差异。四种植物各自分布水域内的N、P因子的平均浓度分别为 ,总氮 (TN) :穗状狐尾藻 (0 .774mg·L- 1 ) >苦草 (0 .71 4mg·L- 1 ) >金鱼藻 (0 .70 1mg·L- 1 ) >微齿眼子菜(0 .695mg·L- 1 ) ;总磷 (TP)平均含量 :穗状狐尾藻 (0 .1 2 3mg·L- 1 ) >微齿眼子菜 (0 .1 1 8mg·L- 1 ) >金鱼藻 (0 .1 0 7mg·L- 1 ) >苦草 (0 .0 79mg·L- 1 )。结果同时表明金鱼藻、微齿眼子菜和苦草对水中TN含量无显著影响 ,而穗状狐尾藻则明显可以提高水中TN水平。四种沉水植物均能有效吸收水中的P ,从而降低水中的TP含量。综合比较发现 。

Baoan Lake is one of typical shallow lakes along middle reach of the Yangtze River. In August 2001, submerged macrophytes were investigated in Baoan Lake by setting up 103 sampling sites with assistant of a GPS setting. Water samples were collected simultaneously for chemical analysis. Under the support of GIS software ArcView 3.2, we established two GIS databases, including the database of mycrophytes and the database of physicochemical factors, and the data source comes respectively from the field sampling and chemical analysis. Then the database was applied to simulate macrophytes distribution and ecological factor fields in the lake. Based on the technique of GIS spatial analysis, different parts of N and P factor fields were selected spatially according to distribution areas of four dominant submerged macrophytes ( Ceratophyllum demersum L ., Myriophyllum spicatum L .,Potamogeton maackianus A. Benn. and Vallisneria spiralis L.), and the non macrophyte distribution area. By characterizing these selected fields with the grid statistic method, we analyzed the influence of each macorphyte distribution pattern on the levels of N and P factors in the water environment. The results implied significant impact of each macrophyte distribution on N and P factors concentration in their surrounding water environment, moreover impact effect and intensity has varied according to the mycrophyte species. As far as the concentration of TN and TP in surrounding water is concerned,TN: M. spicatum (0.774mg·L -1 )> V. spiralis (0.714mg·L -1 )> C.demersum (0.701mg·L -1 )> P. maackianus (0.695mg·L -1 );TP: M. spicatum (0.123mg·L -1 )> P. maackianus (0.118mg·L -1 ) > C.demersum (0.107mg·L -1 )> V. spiralis (0.079mg·L -1 ). The results also demonstrated C.demersum, P.maackianu and V.spiralis are unable to change the TN concentration in the water phase by comparing with the non mycrophyte distribution area. The influence on N factor is just to regulate and control the N circle among different inorganic compounds. In addition, P. maackianus and C. demersum presented the potential on organic pollutants degradation. M. spicatum is quite different from other macrophytes. TN concentration in water increases sharply because of M. spicatum distribution. The increased N is mainly emitted from M. spicatum individuals. As to TP concentration in water environment, the four macrophytes have the same effect. They are all able to absorb P directly from surrounding water, decreasing observably the TP concentration in water. It suggested that the water phase is playing a role in the nutrition of these species in the eutrophic waters. It is different from the in oligotrophic waters in which macrophytes acheive P requirements by direct uptake from the sediments. In condusion submerged macrophytes have ability to reduce TP concentration and stabilize TN concentration in waters. Macrophytes help to reduce the trophic level of water expcept that M. spicatum accelerate the eutrophication.