Synthesis Working Groups

With more than 36 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.


2017 LTER Synthesis Working Groups


Synthesizing population and community synchrony to understand drivers of ecological stability across LTER sites

Principal Investigators: Lauren Hallett, Daniel Reuman, Katharine Suding

gammarid amphipod
A 23-year record of zooplankton populations
from the Palmer LTER, along with hundreds of other
datasets, will contribute to understanding the
role of synchrony in ecological diversity.
Gammarid amphipod. Credit: Joe Cope/Palmer LTER

Understanding factors that influence ecological stability is a key question in ecology. Population ecology has highlighted that synchrony within a species over space is an important indicator of species stability. Community ecology, in contrast, has highlighted that asynchrony between species within space may enhance the stability of aggregate properties (such as total productivity). Using LTER data, we will integrate population and community approaches to synchrony to understand drivers of ecosystem stability at different scales. We will apply cutting-edge statistical techniques (e.g., wavelet analyses, variance decomposition) to long-term, spatially replicated data from terrestrial and aquatic LTER sites in order to: 1) understand the timescales at which synchrony occurs, 2) identify drivers of synchrony and 3) integrate the effects of population and community synchrony on ecological stability. Our diverse group consists of terrestrial and aquatic ecologists with synthesis experience and quantitative ecologists with strong analytical skills. Final products from the working group will include an R package containing our analytical tools, a data workflow and derived data product, and a series of papers synthesizing causes and consequences of synchrony across the LTER network.


Scaling-Up Productivity Responses to Changes in Biodiversity

Principal Investigators: Forest Isbell, Jane M. Cowles, and Laura Dee

silwood biodiversity plots
Long-term biodiversity-productivity experiments,
such as those at Silwood Park, UK are part of
the wide-ranging data that researchers
will synthesize. Credit: Nutrient Network

Although hundreds of short-term local experiments indicate that random changes in biodiversity can cause substantial changes in primary productivity, considerable debate remains regarding whether these influences of biodiversity are weaker or stronger at larger spatial and temporal scales in natural ecosystems. Given this knowledge gap, current models often implicitly assume no influence of biodiversity on ecosystem productivity, likely leading to inaccurate predictions in at least some cases. We propose to develop and test a strategy for scaling-up results from biodiversity experiments to natural communities by testing theory and bridging gaps between previous experimental and observational studies. In the four proposed meetings, one of which would be co-funded, we will advance understanding of scaling up in space, scaling up in time, and accounting for non-random shifts in dominant traits. Integrating these three advances will allow us to generalize from a few experiments to data from many grasslands and forests worldwide, including those at 17 LTER sites. The proposed activities would enable prediction of the scales and conditions under which changes in biodiversity strongly or weakly influence ecosystem productivity.


Advancing soil organic matter research: Synthesizing multi-scale observations, manipulations & models

Principal Investigators: Kate Lajtha and Will Wieder

soil cross section
This multi-organization mutli-site project utilizes the
opportunity that is inherent in cross-site synthesis. It's
a chance to test ideas that can't be resolved at individual
sites. Credit: Pixabay (CC0)

Soil organic matter is a massive storehouse for carbon, as well as a key regulator of nutrient cycling and soil quality in terrestrial ecosystems, yet ecology lacks a full understanding of the controls on stabilization and breakdown of soil organic matter. Two sets of competing theories underlie models that adequately predict site-specific dynamics, but result in different sets of predictions about the response of soil organic matter to perturbations.

Cross-site synthesis of long-term, studies, particularly those incorporating experimental perturbations, provides an opportunity to evaluate these theories under varying conditions of climate, biological community, and topography, among other factors. This working group is synthesizing soil organic matter data across 15 LTER sites and also includes data and participants from Critical Zone Observatory (CZO) sites, Detrital Input and Removal Treatments (DIRT) Network, and Nutrient Network (NutNET). The group’s goal is to refine and evaluate soil organic matter stabilization theories and to produce a dataset that encompasses the impact of experimental manipulations on soil organic matter at different sites.



2016 LTER Synthesis Working Groups


Stream elemental cycling: Global patterns in stream energy and nutrient cycling

Project PIs: Adam Wymore (LUQ); Sujay Kaushal (BES)

Lookout Creek at Andrews LTER
The Stream Elemental Cycling Working Group will
use data from 19 sites, including the HJ Andrews
Experimental Forest LTER (above, at Lookout
Creek). Courtesy: LTER Network Office. 

Project summary: Dissolved organic matter (DOM) provides a significant source of energy and nutrients to ecosystems and its biogeochemical cycling is inextricably linked to dissolved inorganic nitrogen (DIN). In stream ecosystems in particular, there is considerable spatial and temporal variation in the relationships between the different fractions of DOM (dissolved organic carbon and nitrogen) and DIN. Here we propose to use LTER data, as well as other data sources, to examine global patterns in the cycling of DOM and DIN. We ask the over-arching question: under what environmental conditions are the different fractions of DOM and DIN linked? We will examine the interaction between DOM and DIN among biomes ranging from tundra, boreal, desert, temperate forests, tall-grass prairies, and tropical rainforests. Compiling this unprecedented global database will also allow us to examine energy and nutrient cycling across seasons and environmental and management gradients. Our working group is comprised of leaders in the field of stream biogeochemistry, emerging early-career scientists and graduate and undergraduate students. Our synthesis will generate new results and insights, leading to high-profile publications relevant to our understanding of how streams regulate the export of energy and nutrients.


A synthesis to identify how metacommunity dynamics mediate community responses to disturbance across the ecosystems represented in the LTER network

Project PIs: Eric R. Sokol (MCM); Christopher M. Swan (BES); Nathan I. Wisnoski (AND)

Aerial of Cedar Creek
The Metacommunities Working Group will use LTER
data to assess stability across disturbance gradients, 
including the landscape at Cedar Creek LTER
(above). Photo Credit: Jacob Miller, 2014.

Project Summary: Metacommunity ecology considers both the local- and regional-scale factors that influence community assembly. Previous work has identified dispersal, niche differentiation, and habitat heterogeneity as crucial parameters that determine metacommunity dynamics and stability in response to disturbance. However, it remains unclear whether the parameter combinations that are predicted to confer stability do so over long time scales and across ecosystem types. The ecosystems in the NSF Long-Term Ecological Research (LTER) network vary in habitat heterogeneity; likewise, the species assemblages within them exhibit varying degrees of niche differentiation and dispersal ability. Using LTER datasets, we aim to synthesize the general relationships between metacommunity parameters and stability across a diverse range of ecosystems and over long temporal scales. To do so, we will characterize metacommunity stability across a disturbance gradient, estimate metacommunity parameters, assess how well estimated parameters predict stability over time, and parameterize metacommunity simulation models with LTER data to identify the major predictors of metacommunity stability. Final products from this working group include an R package containing metacommunity time series datasets and relevant analyses, a synthesis of metacommunity stability and sensitivity to disturbance across the LTER network, and a prospectus detailing the application of simulations for understanding metacommunity dynamics.

Integrating plant community and ecosystem responses to chronic global change drivers: Toward an explanation of patterns and improved global predictions

Project PIs: Kimberly J. La Pierre (KNZ/CDR/SGS); Meghan L. Avolio (KNZ); Kevin R. Wilcox (KNZ/SGS)

CAP LTER doing Long-term monitoring in desert urban parks
The Communities-to-Ecosystem Working Group will
utilize data from 101 long-term resource
manipulation experiments, like this one at Central
Arizona-Phoenix LTER studying impacts of nutrient
enrichment in urban desert parks.
Photo Credit: Tim Trumble, 2009. 

Project Summary: Many global change drivers (GCDs) lead to chronic alterations in resource availability. As communities change through time in response to these GCDs, the magnitude and direction of ecosystem responses is also predicted to change in a non-linear fashion. We propose to examine whether plant community dynamics are predictive of shifts in ecosystem function across 101 long-term resource manipulation experiments (including 32 LTER experiments). Our working group will address three main objectives: 1) identify temporal patterns of plant community change in response to global change manipulations; 2) link these patterns of community change to changes in aboveground net primary productivity and carbon storage; and 3) incorporate community change into ecosystem models predicting functional responses to GCDs. These objectives address four of the five LTER core thematic areas (primary production, population studies, organic matter dynamics, and disturbance patterns/processes). Overall, we will test current ecological theory to inform predictions of future responses to GCDs across a wide variety of terrestrial herbaceous systems, including those represented by 17 LTER sites. Funding from the LTER NCO will allow a diverse group of ecologists with expertise in modeling, statistical development, community ecology, and field experiments to come together to accomplish these objectives. 



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