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
Companion dataset: https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-ntl&identifier=23
Please consult NTL's website for information on experimental lake manipulations and the DNR's website for management activities

本数据集于6月至8月期间，在麦迪逊地区四座主要研究湖泊——门多塔湖（Mendota）、莫诺纳湖（Monona）、温格拉湖（Wingra）以及费什湖（Fish Lake）——沿岸布设垂直于湖岸的样带，沿样带在水深1至4米、间隔0.5米的站位处，从船上开展水生大型植物（Aquatic macrophytes）采样工作。
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，通过连接的绳索拖拽约2米划过湖底。针对每次耙拖采样，根据上部耙齿的覆盖范围，将采集到的丝状藻类与水生大型植物总丰度按0至5级进行密度评级。覆盖范围的判定由调查人员根据耙齿数量及被覆盖齿面面积进行主观判断。对每个站位的4次耙拖采样评级取平均值，即可得到该站位的总密度评级。
此外，还将测量每次耙拖采样中获取的总植物生物量与丝状藻类总生物量。采样过程中应尽可能挤干植物中的水分，以减少最终称重时的含水量。使用野外便携秤在船上完成称重操作，对每个站位的4次耙拖采样的生物量取平均值，即可得到该站位的植物总生物量与丝状藻类总生物量的平均权重。
另有配套数据集《大型植物评级——麦迪逊湖区》（Macrophyte Rating --- Madison Lakes Area），其中包含针对单一水生大型植物物种的耙拖评级数据。在该数据集中，需针对每次耙拖采样，根据上部耙齿的覆盖范围，将采集到的丝状藻类与各单一水生大型植物物种分别按0至5级进行密度评级。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齿面面积进行主观判断，因此需要将不同植物分离以评估单一物种的覆盖情况。对每个站位的4次耙拖采样评级取平均值，即可得到该站位所发现的各物种的总密度评级。
采样频率：每年夏季一次；采样站位数量：4个。
配套数据集链接：https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-ntl&identifier=23。如需了解湖泊实验调控相关信息，请查阅NTL官网；有关管理活动的详情，请咨询DNR官网。