Long-term experiments in the LTER network: Past, present, and future roles

Background/Question/Methods   

Manipulative experiments have been long been central to advancing ecological understanding, and while short-term experiments are much more common, long-term (LT) experiments have had a foundational role in ecology.  The NSF-funded US Long-term Ecological Research (LTER) program has been conducting site-based research for more than three decades, with LT experiments figuring prominently in the research portfolios of many of the sites within the LTER network. Although there are certainly many valuable LT experiments outside the LTER network, arguably the largest and most diverse collection of LT experiments are associated with the LTER program, and thus an assessment of the role of these LT experiments in the LTER Network and the broader scientific community, as well as the collective lessons learned from these experiments is warranted as the LTER program continues into its 4^th decade.

Results/Conclusions  

Our review of LT experiments across the LTER network revealed many unique insights into long-term patterns and processes that, in many cases, only became apparent after many years of study. In some cases, answers to the questions motivating these experiments were opposite when based on short-term (3-5 year) responses vs. LT responses (>6 years). Further, many of the longest running experiments have become research platforms for other investigators allowing for both opportunistic research to be conducted that was outside the original expectation for the experiment, as well as more detailed mechanistic studies to be nested within these experiments. Over time, the complexity of LT experiments has increased with many more multi-factor experiments specifically related to global change issues ongoing across the network today. However, it is clear that given the scale and scope of global change drivers, coordinated, multi-site and multi-factor experiments are needed, yet these are rare in the LTER network. Such a network of LT experiments would be particularly valuable if it was strategically designed to take advantage of the long-term observations and contextual understanding extant within the LTER platform, as well as other long-term field sites outside the LTER network.