The Future of Cross-site
Climate Research in LTER
Organizer: Doug Goodin (KNZ)
Participants:
Tony Brazel (CAP)
Andrew Fountain (MCM)
Julian Hadley (HFR)
Glenn Juday (BNZ)
Mark Losleben (NWT)
Douglas Moore (SEV)
The purpose of this workshop was to discuss ideas and plan for the next stage of climate-ecosystem to be conducted within the LTER network. This new program follows the highly successful Climate Variability and Ecosystem Response (CVER) project, organized and led by David Greenland and members of the LTER climate committee. The CVER project involved the contributions of over 50 LTER scientists and resulted in an edited volume featuring 20 contributed chapters and extensive synthesis material. The CVER program was motivated by a series of framework questions organized around temporal scale. Within these temporal and topical constraints, researchers were free to choose which of the framework questions they wished to address and what time scale or scales (short-term, quasi-quintennial, decadal, century/millennial) were most appropriate for their topic. CVER research addressed a broad range of topics, the majority of which concentrated on a single time scale at one LTER site – although a few chapters dealt with cross-site analysis or with multiple time scale at a single site. As a result of adopting this format, the CVER volume represents a comprehensive synthesis of climate-ecosystem interactions within the LTER network.
Because of the comprehensive nature of CVER, there was a general feeling among workshop participants that another project built around broadly defined synthesis questions would not generate great interest. Instead, it was felt that a more focused research topic encompassing all of the sites would be preferable. Further, the workshop participants felt that a single research topic applied across the network would fit better with the current LTER emphasis on network-wide synthesis. Discussion among workshop participants therefore centered on topics that could exploit the unique capabilities of the LTER network. Several topics were suggested, but the one that generated the most enthusiasm was a cross-site investigation of extreme climatic events, and their importance in ecosystem functioning.
From an ecological perspective climatic extreme events are an important area of research. Considerable research has been done looking at specific events at specific sites, there is little systematic work on the topic itself. Even the terminology is not well defined. From a weather-climate perspective, an extreme event can be defined statistically in terms of measurable variables. For example, an extremely large precipitation event, tropical storm, or drought would all qualify as extreme events, although occurring at different time scales. From an ecosystem perspective, however, extreme events are not as easy to define. For example, in grasslands, which tend to be systems adapted to extreme and variable climate regimes, exceptionally large transient temperature or precipitation events may have little lasting effect on the ecosystem unless they persist for a period of years. In contrast, a temperature change of only a few degrees over a much shorter time period might cause great changes in the function of Antarctic ecosystem, and would thus constitute an extreme event.
One of the explicit goals of this research will be to define extreme events from an ecological perspective, a process made possible by the unique characteristics of the LTER network. As has been frequently noted, the distribution of LTER network sites is too geographically sparse and irregular and the available data series at most sites too short to support studies of the spatial distribution of climate. The LTER network was not designed to support this type of research. However, within the LTER network is a large group of scientists with extensive knowledge of the workings of the ecosystems represented by each site, including the interaction of climate and the ecosystem. In addition, the network itself provides these researchers with an accessible mechanism for communicating both data and ideas. We propose to use these unique capabilities of the network to help define extreme events for each of the ecosystems represented by the various LTER sites. This will involve development of a set of questions aimed at defining criteria for determining when an individual system (i.e. site) is exhibiting an extreme response, as well as defining the type and duration of weather/climate events that might shift the system into this extreme response space. To facilitate gathering this type of information, these questions will be used to interview interested and willing researchers at each of the LTER sites. Once these interviews are gathered and organized, they will be used to define a “typology” of response to extreme events. LTER sites will then be sorted into categories based on their response type. Project collaborators will then produce a series of chapters describing each of the types of extreme events and the ecosystem(s) in which they typically occur. These chapters will become the basis for an edited volume.
We believe this project will be important for two reasons. First, it will contribute to fundamental knowledge of climate-ecosystem interactions by systematically defining the types of weather/climate processes that are “extreme” within various ecosystems, while at the same time considering how various systems might be similar or related in terms of their response to weather or climate. We envision development of an “extreme event space” analogous to the climate space which is frequently used to define ecosystems but with dimensions such as event type, event duration, event energy, etc. Plotting LTER sites within this space might shed light on some fundamental aspects of climate-ecosystem interaction across the LTER network.
The second potential value for the project is as a model for cross-site synthesis. An important lesson from the CVER project was that relevant climate processes vary widely across the network, and that synthesis must be based on a unifying organizational framework, rather than on investigation of processes common to all sites. We intend to extend the idea of the unifying framework to include a variable (extreme events) whose definition might vary with ecosystem, but whose relevance is network wide. We hope that this might provide guidance for further climatic or other investigations arranged by topic, rather than by process.