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PROJECT SUMMARY

The North Temperate Lakes Long-Term Ecological Research (NTL LTER) site was established in 1981. We designed and implemented a comprehensive study of 7 lakes in the Northern Highland Lake District of Wisconsin and the surrounding landscape. The 105 peer-reviewed publications produced in the last five years have made significant advances in the understanding of lakes and their landscapes.

We propose three international projects on the long-term temporal and spatial dynamics of temperate lakes at regional to global scales. We focus on three questions that are best addressed with data from widely scattered, multiple lake districts. These questions are:

(1) What patterns occur in ecological variability and organization of lake ecosystems when lake districts are considered at regional and global scales?

(2) Can patterns of gains and losses of species from individual lakes be related to the overall patterns of species occurrence for lakes within a region?

(3) Can analyses of lake ice freeze and breakup phenologies around the globe be used to describe and understand large scale dynamics and trends in climate?

The primary reason for seeking the collaboration of our international colleagues is to increase the temporal and spatial extent of analyses. European, Asian and Canadian data on lakes are longer than those of our LTER site. Data sets as comprehensive as ours have runs of 20 or so years and ice phenology data begins as early as the 1700s on some European and the 1400s for Japan compared with the record of 135 years in Wisconsin. These longer records will be even more powerful when pulled together and analyzed at a global scale in the north temperate zone. We have identified 13 international sites or regions for initial interaction and collaboration.

For our study of ecological variability and organization of lake districts we will examine temporal variability patterns (coherence) of lakes within lake districts, explore the relationship between landscape position and lake variability across lakes in different lake districts, and examine relations between lake variability and factors such as lake morphometry and land use. Comparisons will provide opportunities to determine whether patterns we have observed at the Northern Highland Lake District occur across lake districts worldwide. We hypothesize that they will.

In our analyses of gains and losses of fish and zooplankton species we will investigate regional dynamics of species gains, losses, and turnover rates in different lake districts, relate these dynamics to the extent and strength of interconnections among lakes within these regions, and investigate how human activities may influence these processes.

In our analyses of lake ice phenology, climate change, and variability in the Northern Hemisphere, we will analyze interannual variability in thaw and freeze dates and where possible the antecedent climatic variability. Are observed patterns in Wisconsin general for larger regions of the northern hemisphere? Patterns are the recent warming based on breakup dates, and variability associated with ENSO events and inderdecadal or longer time scales, Expected patterns will be generated through global climate and ice freeze modeling.

Our overall approach will be through direct contacts and electronic networking. We will send individual scientists to non-US sites to work with local data, encourage and facilitate visits to our site, hold international analysis and synthesis workshops, emphasize joint analyses of shared data, and produce co-authored papers.