North Temperate Lakes LTER Regional Survey Macrophytes Plant Index 2015 - current

The Northern Highlands Lake District (NHLD) is one of the few regions in the world with periodic comprehensive water chemistry data from hundreds of lakes spanning almost a century. Birge and Juday directed the first comprehensive assessment of water chemistry in the NHLD, sampling more than 600 lakes in the 1920s and 30s. These surveys have been repeated by various agencies and we now have data from the 1920s (UW), 1960s (WDNR), 1970s (EPA), 1980s (EPA), 1990s (EPA), and 2000s (NTL). The 28 lakes sampled as part of the Regional Lake Survey have been sampled by at least four of these regional surveys including the 1920s Birge and Juday sampling efforts. These 28 lakes were selected to represent a gradient of landscape position and shoreline development, both of which are important factors influencing social and ecological dynamics of lakes in the NHLD. This long-term regional dataset will lead to a greater understanding of whether and how large-scale drivers such as climate change and variability, lakeshore residential development, introductions of invasive species, or forest management have altered regional water chemistry. The purpose of the macrophyte survey is to identify, and quantify the types of aquatic plants within the various 28 regional survey lakes. The macrophyte survey consists of sampling macrophyte plants using a metal rake attached to a 15ft pole at approximately 140 spatially resolved points on a lake that are spread out in a grid like fashion, equally spaced from each other. Sampling locations were chosen such that the maximum depth at which macrophytes were surveyed was equal to or less than 15ft of water. Macrophyte sampling occurs in the latter part of the summer (after July 10) to ensure that macrophytes have had adequate time to grow and our sampling efforts capture the typical summer macrophyte community in each lake. Macrophyte sampling in these 28 lakes is ongoing and will be repeated approximately once every six years.

北高地湖区（Northern Highlands Lake District, NHLD）是全球少数拥有近一个世纪以来数百个湖泊周期性综合水化学数据的区域之一。伯奇（Birge）与朱迪（Juday）主导了NHLD首次全面水化学评估工作，于1920至1930年代对600余个湖泊开展了采样。后续多家机构重复开展了此类调查，目前我们已获取1920年代（威斯康星大学，UW）、1960年代（威斯康星州自然资源部，WDNR）、1970至1990年代（美国环境保护署，EPA）以及2000年代（北温带湖泊长期研究站，NTL）的相关数据集。作为区域湖泊调查一部分选取的28个湖泊，至少被上述4次区域调查覆盖采样，其中包括1920年代Birge与Juday的采样工作。这28个湖泊的选取依据是景观位置与岸线开发程度的梯度分布，二者均为影响NHLD湖泊社会与生态动态的关键因子。这套长期区域数据集将助力我们更深入地探明气候变化与变率、湖滨住宅开发、入侵物种引入以及森林管理等大型驱动因子，是否以及如何改变了区域水化学组成。本次大型水生植物（macrophyte）调查的目标是识别并量化这28个区域调查湖泊内的水生植物类群。该调查采用安装于15英尺长杆上的金属耙具，在每个湖泊按网格状均匀布设的约140个空间精准采样点开展采样。采样点的选取需确保大型水生植物调查的最大水深不超过15英尺。采样工作定于夏季后期（7月10日之后）开展，以确保大型水生植物有充足的生长时长，从而捕捉到每个湖泊典型的夏季大型水生植物群落。目前这28个湖泊的大型水生植物采样工作仍在持续，计划每约6年重复开展一次。