The US National Science Foundationfunded Long Term Ecological Research (LTER) Network supports a large (around 240) and diverse portfolio of long-term ecological experiments. Collectively, these long-term experiments have (a) provided unique insights into ecological patterns and processes, although such insight often became apparent only after many years of study; (b) influenced management and policy decisions; and (c) evolved into research platforms supporting studies and involving investigators who were not part of the original design. Furthermore, this suite of long-term experiments addresses, at the site level, all of the US National Research Council's Grand Challenges in Environmental Sciences. Despite these contributions, we argue that the scale and scope of global environmental change requires a more-coordinated multisite approach to long-term experiments. Ideally, such an approach would include a network of spatially extensive multifactor experiments, designed in collaboration with ecological modelers that would build on and extend the unique context provided by the LTER Network.
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More challenging is the definition of long term. Ideally, ecological or life-history criteria (e.g., process and turnover rates, life span of organisms) or the time scales of ecological phenomena would be used to define an experiment as long term. Operationally, however, the duration of experiments, which typically require financial resources to be initiated and continued, is to a large extent constrained by funding cycles. Given the Long Term Ecological Research (LTER) Network focus of this review, we view a long-term experiment as one that is planned to exceed or already exceeds six years in length, which would span two traditional LTER Network funding cycles and is also a sufficient length to allow both mechanisms and temporal dynamics to be identified. This duration is also consistent with the requisite period of continuous measurements for support by the US National Science Foundation’s Long-Term Research in Environmental Biology program.
- LTER Network
- climate change
- global change
- long-term research
- multifactor experiments