North Temperate Lakes LTER: Macrophyte Rating - Madison Lakes Area 1995 - current

Aquatic macrophytes are sampled from a boat at stations located at depths from 1 to 4 meters at 0.5-m intervals along transects perpendicular to the lake shoreline of the four primary study lakes in the Madison area (Lakes Mendota, Monona, and Wingra, and Fish Lake) from June to August. A weighted, double-headed garden rake is cast off the front left, front right, rear left, and rear right of the boat and then dragged approximately 2 meters across the bottom by means of an attached line. For each rake cast, filamentous algae and any aquatic macrophyte species present are assigned a density rating from 0-5 based on the extent of coverage of the upper rake head. Determination of extent of coverage involves judgment of the surveyor as to the number of rake teeth and area of teeth covered by each species. It is necessary to separate plants to assess individual species coverage. Ratings from the 4 rake casts at each station can be averaged to compute an overall density rating for each species found at the station.1 to 4 meters at 0.5-m intervals along transects perpendicular to the lake shoreline of the four primary study lakes in the Madison area (Lakes Mendota, Monona, and Wingra, and Fish Lake) from June to August. A weighted, double-headed garden rake is cast off the front left, front right, rear left, and rear right of the boat and then dragged approximately 2 meters across the bottom by means of an attached line. In addition (see related data set: Macrophyte Weight --- Madison Lakes Area), the total plant mass and the total filamentous algae mass in each tow is measured. To the maximum extent possible, water is squeezed from the plants to minimize the amount of water present in the final weight. Weights are recorded in the boat using field scales. Weights from the 4 rake casts at each station can be averaged to compute overall average weights for plant mass and for filamentous algae mass at the station. Sampling Frequency: annually during summer Number of sites: 4本研究于6月至8月期间，在麦迪逊地区四座核心研究湖泊（门多塔湖（Mendota Lake）、莫诺纳湖（Monona Lake）、温格拉湖（Wingra Lake）以及费什湖（Fish Lake））开展水生大型植物（aquatic macrophytes）采样。采样以机动船为作业平台，沿垂直于湖岸的样带布设采样站位，站位水深梯度为1至4米，间隔0.5米设置一个点位。 采用带配重的双头园艺耙开展采样作业：分别从船体左前、右前、左后、右后侧将耙具投入水底，通过连接的缆绳将耙在水底拖拽约2米的距离。 每次耙捞作业完成后，根据耙头上层的覆盖范围，将采集到的丝状藻类（filamentous algae）及所有水生大型植物物种赋予0至5分的密度评级。覆盖范围的判定由调查人员根据耙齿数量及各物种覆盖的耙齿面积进行主观判断，需分离植物个体以准确评估单一物种的覆盖占比。将每个站位的4次耙捞作业所得评级取平均值，即可计算出该站位各物种的总密度评级。 此外（相关数据集：麦迪逊湖区大型植物生物量（Macrophyte Weight --- Madison Lakes Area）），需对每次耙捞作业采集的总植物生物量及丝状藻类总生物量进行称量。操作中需尽可能挤干植物体内的水分，以最大限度降低最终称量结果中的含水量。使用野外现场天平在船上完成重量记录。将每个站位4次耙捞作业所得的生物量数据取平均值，即可计算出该站位的植物总生物量及丝状藻类总生物量的平均加权值。 采样频率：夏季每年开展一次；采样位点数量：4个。