With over 40 years of continuous data collection across many biomes, the Long Term Ecological Research (LTER) Network is a rich source of information for testing big-picture concepts about how ecosystems work. Luckily, the Network also brings together a group of scientists with creative ideas about how to wring new insights from diverse data sources.

The LTER synthesis working group process is designed to capitalize on the experiments, contextual knowledge, data, and creativity of the LTER Network. By funding small groups of scientists from inside and outside the Network to work intensely together on a synthesis project, the process encourages the ecological community to use existing data to probe novel theories, test generality, and search for gaps in our understanding.

Curious about progress of synthesis working groups?

The 2021-2022 LTER Synthesis Webinar Series presents hour-long updates from current Synthesis working groups. The schedule includes links to recorded presentations and registration for upcoming webinars.

At the 2018 LTER All Scientists’ Meeting, site principal investigators were treated to a series of short, videotaped presentations from current synthesis groups. Those presentations are now available on the LTER Network YouTube Channel.

In Spring 2018, each synthesis group gave an hour-long webinar detailing their questions, approaches and progress to-date. Please visit the Spring 2018 Webinar Series web page for links to each webinar.

A global synthesis of multi-year drought effects on terrestrial ecosystems

Principal Investigator: Kate Wilkins, Colorado State University, Osvaldo Sala, Peter Wilfahrt, University of Bayreuth, Laureano Gherardi, Melinda Smith
Award Date: January 9, 2020
Description: PIs: Kate Wilkins (CSU), Osvaldo Sala (ASU/JRN), Peter Wilfahrt (University of Bayreuth), Laureano Gherardi (ASU/JRN), Melinda Smith (CSU/KNZ) Drought impacts on terrestrial ecosystems have increased globally over the last century with models forecasting that droughts will become more frequent, extreme, and spatially extensive. The goals for this project are to synthesize results from a unique global network of drought manipulations, focusing on how ecosystem productivity responds to drought over time and key mechanisms (changes in plant composition) underlying these impacts. We propose to host a series of working groups to synthesize an existing multi-year dataset from the International Drought Experiment (IDE). The IDE is a coordinated, global network of extreme drought experiments at >100 sites, including eight LTER and four ILTER sites. The objectives for these synthesis meetings include: 1) analyzing how short-term drought affects ecosystem sensitivity patterns (i.e. the relationship between plant production and precipitation), 2) identifying how aboveground productivity and plant species composition (abundance, richness, evenness, re-ordering) change in response to a 4-year drought, and 3) determine how shifts in plant species composition indirectly affects the sensitivity of productivity to drought over time.

Ecological Metagenome-derived Reference Genomes and Traits (EMERGENT)

Principal Investigator: Jeff Blanchard, UMass Amherst/HFR, Janet Jansson, Pacific Northwest National Laboratory, Jorge Rodrigues, UC Davis, Lee Stanish, NEON, Margaret O’Brien, UC Santa Barbara, Jason McDermott, Pacific Northwest National Laboratory
Award Date: January 9, 2020
Description: Our climate crisis, resulting from changes in interacting climate variables (temperature, rainfall, atmospheric chemistry) over the last century, has impacted all ecosystems on the surface of the Earth. With modern DNA sequencing techniques it is now possible to simultaneously sample thousands of different species, providing a window into the diverse soil organismal community and their ecological traits. While often the sequence data is stored at international nucleotide sequence data centers (NCBI, EBI, DDBJ), these databases do not have the resources to process and integrate microbiome data. This results in the compartmentalization of studies, failure to effectively utilize data across sites, and repetitive development of similar analytical pipelines across multiple research groups. The EMERGENT working group intends to alleviate some of these bottlenecks to make greater use of the existing genetic data to address climate related-questions and provide reference species (genomes) for future research. Their work will advance efforts to harmonize molecular information for microbial taxa and their functional traits, streamline their use in syntheses with related ecosystem level data, and enable future metagenomic studies to leverage EDI environmental data, spurring future microbial ecology research at LTER sites.

Ecosystem transitions: increased variability and regime shifts

several large rainfall exclusion shelters on an open grassland
Principal Investigator: Cristina Portales-Reyes, University of Georgia, Y. Anny Chung, University of Georgia
Award Date: January 8, 2021
Description: Human impacts on ecosystems can result in persistent compositional shifts that are difficult to reverse even after relaxation from perturbations. Considerable debate remains on whether these observed shifts in ecosystems are due to the existence of tipping points and systems with alternative attractors, or whether observed shifts in ecosystems represent communities in alternative trajectories that will eventually reach a common stable point. In addition to human perturbations, ecosystems are also experiencing other transient dynamics, such as increased climate variability, which could promote or prevent state shifts. Using cross-site synthesis of LTER experiments that have simulated human perturbations or climate variability, this synthesis effort will test whether and which observed compositional shifts are a result of critical transitions or transient dynamics. Researchers will use these data to develop and inform theory that will improve predictions on the magnitude and frequency of perturbations and climate variability needed to promote or prevent lasting shifts in ecosystem composition.

From poles to tropics: A multi-biome synthesis investigating the controls on river Si exports

Principal Investigator: Joanna Carey, Babson College, KathiJo Jankowski, US Geological Survey
Award Date: January 9, 2020

Riverine exports of silicon (Si) directly influence global carbon (C) cycling through the growth of diatoms, ubiquitous autotrophs in marine and freshwater systems, which account for ~25% of global primary production. Rivers play essential roles in processing and supplying the Si necessary for diatom growth, but we have limited knowledge of the controls on river Si exports, especially how they vary across biomes. Prior work has shown conflicting importance of various drivers, such as lithology, riverine productivity, and terrestrial vegetation in controlling river Si exports. Capturing a baseline understanding of how these factors influence Si exports across biomes is essential for understanding freshwater and marine C cycles, especially during this period of rapid climatic warming. This synthesis will answer three specific research questions related to the roles of 1) terrestrial vegetation, 2) river productivity and 3) climate warming in controlling river Si exports across biomes. Our proposed sites span the globe (e.g., Antarctic, tropical, temperate, boreal, alpine, Arctic systems), and present a unique cross-network opportunity to connect LTER-based research with that of the Critical Zone Observatory and USGS. Together, we will create the first data-driven predictive framework of how riverine Si exports will respond to global change.

Identifying environmental drivers of plant reproduction across LTER sites

Principal Investigator: Jalene LaMontagne, DePaul University, Elizabeth Crone, Tufts University, Miranda Redmond, Colorado State University
Award Date: January 8, 2021
Description: Reproduction is a key component of plant life cycles and is crucial for dispersal, however it has a surprisingly poorly understood relationship to environmental drivers. This is particularly true for plant species with highly variable reproduction over time, known as ‘mast seeding’. While mast-seeding patterns have been linked to weather (temperature, precipitation), describing past patterns and predicting future reproduction of plant populations is particularly challenging because high temporal variability in reproduction (with 3-7 or more years between large reproductive events) requires large long-term datasets for analysis, particularly if patterns are changing over time. Using data across Long Term Ecological Research (LTER) sites, and bringing together experts in mast-seeding, forest ecology, population dynamics, synthesis, and statistical and mathematical modeling, the synthesis group plans to:
  1. assess how generalizable temporal patterns of mast seeding are across species and disparate locations;
  2. test how environmental drivers and past performance influence mast seeding along a continuum from non-masting (i.e., low temporal variability) to strongly masting (i.e., high temporal variability) species; and
  3. compare statistical approaches for finding environmental drivers for plant reproduction.
Products from this working group will include: an R-workflow for calculating mast seeding metrics, incorporation of LTER plant reproduction data into i) an existing R-package for LTER population-level synthesis (Popler) and ii) global mast-seeding databases, multiple publications, and a workshop on spatio-temporal patterns and environmental drivers of plant reproduction.


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