North Temperate Lakes LTER Regional Survey Water Chemistry 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 regional lakes survey in 2015 followed the standard LTER protocol for standard water chemistry and biology. Samples were taken as close to solar noon as possible. Seven lakes had replicates performed, which were chosen at random.

北部高地湖区（Northern Highlands Lake District, NHLD）是全球少数拥有近百年间数百个湖泊周期性综合水化学监测数据的区域之一。伯奇（Birge）与朱迪（Juday）牵头开展了该区域首次全面的水化学评估，于1920至1930年间对600余座湖泊进行了采样。后续多家机构重复开展了此类调查工作，目前已获取1920年代（UW）、1960年代（WDNR）、1970至1990年代（EPA）以及2000年代（NTL）的系列监测数据。作为区域湖泊调查组成部分的28座湖泊，至少被上述4次区域调查覆盖，其中包括1920年代伯奇与朱迪的采样工作。这28座湖泊的选取覆盖了景观位置与岸线开发程度的梯度，二者均为影响北部高地湖区湖泊社会与生态动态的关键因素。这套长期区域监测数据集将助力我们更深入地理解气候变化与变异性、湖岸住宅开发、外来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特征。2015年的区域湖泊调查遵循了长期生态研究（Long-Term Ecological Research, LTER）标准水化学与生物学采样规范。采样时间尽可能接近太阳正午时刻，其中7座湖泊开展了随机选取的重复采样。