天津于桥水库菹草的空间分布格局

Spatial Distribution of Potamogeton crispus in Yuqiao Reservior

为及时了解春季水生植物的实际生长情况和客观反映水深对菹草（Potamogeton crispus）分布的影响,2014年4月4日和21日对天津市蓟县于桥水库的水生植物进行初步调查。利用GPS定位和google地图,在于桥水库库区内均匀设置30个采样点,采集以样点为中心、周边1 m^2内的菹草并称量鲜重,对各采样监测点的水深情况进行测量。通过数据分析,发现菹草的总体分布水深在1.5-5.0 m,2次调查时于桥水库水位分别为19.00 m和18.86 m,计算得出菹草的分布区域高程为13.5-17.5 m（大沽）。对库区菹草生物量进行调查并采用Surfer软件制作其分布等值图,结果显示,库区北岸除峰山南区域（24、27号点）以外,菹草生物量总体较南岸大;其中桃花寺一带（12号点）菹草生物量最大,为4.978 kg/m^2;菹草生长受水深和光照影响较大,水深超过5 m的区域,光照强度和水温均不能达到菹草石芽萌发的条件。在一定水深范围内其生物量与水深之间存在着较明显的负相关关系,对菹草生物量（y）和水深值（x）进行回归分析,拟合方程为：y=0.2092x^2-2.5191x＋7.5095（R^2=0.8941）。

Potamogeton crispus,a perennial submerged species with a wide range of climatic habitats,is an important primary producer in freshwater ecosystems and provides good fodder for herbivorous fish. It not only absorbs nitrogen and phosphorus from the water,but also grows well in eutrophic lakes when other higher aquatic plants are rapidly degraded. However,overgrowth of Potamogeton crispus can degrade water quality,influence normal operation of water conservancy projects and even affect drinking water safety. In this study,we analyzed the aquatic plant community in Yuqiao Reservior,especially the spatial distribution of Potamogeton crispus. The reservoir is the only source of drinking water for Tianjin and is facing serious pollution and eutrophication. This study will help clarify the existing state of aquatic plants in Yuqiao Reservior and provide reference data for overgrowth of Potamogeton crispus and for controlling eutrophication in the reservoir. Thirty sites were selected in Yuqiao Reservoir using GPS and Google maps and the water depth of each sampling site was measured in advance. The fresh weight of Potamogeton crispus and the growth condition of other aquatic plants were investigated at 17 sampling sites near the bank of the reservoir on April 4,2014 and 13 sampling sites at the center of the reservoir on April 21. The biomass of Potamogeton crispus in one square meter at each sampling site was measured five times and the average value was calculated. The water level of Yuqiao Reservior during the first and second survey was 19. 00 m and 18. 86 m,respectively. Potamogeton crispus was found primarily in areas where the water depth was 1. 5-5. 0 m and the elevation 13. 5-17. 5 m. Based on the distribution map of Potamogeton crispus drawn with Surfer software（ versions8. 0,Golden Software LLC）,we found the biomass of Potamogeton crispus in the northern area（ except at sampling site No. 24,No. 27） was higher than that in the southern area of Yuqiao Reservior. The highest value,4. 978 kg / m^2,was observed in the Peach Blossom Temple area（ sampling site No. 12）. Our results indicate that water depth and light intensity greatly influenced the growth of Potamogeton crispus and there was a clear negative correlation between Potamogeton crispus biomass and water depth,within the range tested. The regression equation of water depth and biomass of Potamogeton crispus was y = 0. 2092x^2-2. 5191 x ＋ 7. 5095（ R^2= 0. 8941）. In order to prevent and control the eutrophication caused by the overgrowth of Potamogeton crispus,it is suggested to raise water level and regulate the running time of high water level in Yuqiao Reservior.