North Temperate Lakes LTER: Macrophyte Biomass - 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, the total amount of filamentous algae and aquatic macrophyte species present is 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. Ratings from the 4 rake casts at each station can be averaged to compute an overall density rating for the station In addition, 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. A related data set (Macrophyte Rating --- Madison Lakes Area), contains rake ratings for individual macrophyte species. 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. Sampling Frequency: annually during summer Number of sites: 4 Please consult NTL's website for information on experimental lake manipulations and the DNR's website for management activities

本数据集针对麦迪逊地区四座核心研究湖泊（门多塔湖、莫诺纳湖、温格拉湖以及菲什湖），于6月至8月期间开展采样工作。采样沿垂直于湖岸的样带布设站位，站位水深梯度为1至4米，间隔0.5米，所有采样操作均在船上完成。采用带配重的双头园艺耙，分别从船体左前、右前、左后、右后侧抛入水中，通过连接绳索拖拽约2米穿过湖底。针对每次耙捞作业，根据耙头上部的覆盖范围，将采样获得的丝状藻类与水生大型植物（aquatic macrophytes）总丰度赋予0至5分的密度评级。覆盖范围的判定由调查员依据耙齿数量及耙齿被覆盖的面积进行主观判断。将每个站位的4次耙捞评级取平均值，即可得到该站位的总体密度评级。此外，需对每次拖捞获取的总植物生物量与丝状藻类生物量进行称量。称量前应尽可能挤去植物体内的水分，以降低最终称重时的含水量，使用野外天平在船上记录重量数据。同样将每个站位的4次耙捞重量取平均值，计算得到该站位的植物总生物量与丝状藻类总生物量的平均水平。另有配套数据集"Macrophyte Rating --- Madison Lakes Area"，该数据集包含单种水生大型植物的耙捞评级数据。针对每次耙捞作业，需根据耙头上部的覆盖范围，为每种存在的丝状藻类与水生大型植物物种分别赋予0至5分的密度评级。此时需将植物分离，以评估单物种的覆盖情况，覆盖范围的判定仍由调查员依据耙齿数量及各物种覆盖的耙齿面积确定。将每个站位的4次耙捞评级取平均值，即可得到该站位各检出物种的总体密度评级。采样频率：每年夏季一次。采样站位数量：4个。如需了解湖泊实验调控相关信息，请查阅NTL官网；有关湖区管理活动的信息，请查询DNR官网。