Two new synthesis working groups capitalize on the intensive and extended record of observation at LTER sites to shed light on thorny ecological questions.

The Long Term Ecological Research (LTER) Network Office is pleased to announce the award of two new synthesis working groups to launch in 2021. While individual LTER sites focus primarily on understanding the ecological dynamics of a particular place, network-level syntheses develop knowledge of how those mechanisms vary across many locations, yielding deeper insight into general ecological principles.

Whether “tipping points” truly exist and what they mean for successfully managing ecosystems is one of the most hotly debated topics in ecology. Whether — and how — an ecosystem can be permanently changed by just a small shift in climate, rainfall or nutrient inputs affects the investments that states and communities need to make in early detection and prevention of such changes.

several large rainfall exclusion shelters on an open grassland

The Extreme Drought in Grassland Ecosystems (EDGE) experiment is replicated at 6 sites in NM, CO, WY, and KS. It is one among many ecosystem manipulations that will be incorporated into the synthesis study.
Credit: Anny Chung

The Ecosystem Transitions synthesis group will draw on dozens of experimental manipulations to investigate if tipping points appear to have been reached and learn whether they, in fact, represent alternative stable states.

LTER experiments often include multiple levels of multiple factors, as well as control conditions. For example, one experiment might include two levels of nutrient additions together with three levels of simulated rainfall. They also are often maintained and monitored for decades, not only during manipulation, but long into a “recovery” phase after manipulations have ceased.

Capitalizing on these experiments, the Ecosystem Transitions synthesis team will explore whether some apparent tipping points actually represent alternative pathways to a common endpoint or altered susceptibility to external factors such as climate variability. The group is led by Dr. Cristina Portales-Reyes, a recent graduate student at Cedar Creek LTER and now at a postdoctoral scholar at the University of Georgia and Dr. Anny Chung, an Assistant Professor of Plant Biology and Plant Pathology at the University of Georgia.

In mast seeding years, white spruce trees may produce up to 100’s or 1000’s of times the number of cones produced in non-mast years.
Credit: Amanda Graham via Flickr. CC-BY-NC-ND 2.0

A second synthesis working group, Plant Reproductive Drivers, will focus their efforts on understanding what factors drive the timing of mast seeding, in which some species produce unusually large crops of seeds at irregular intervals. Climate and precipitation are thought to be important controls, but the exact relationship is difficult to parse because 1) both are quite variable and 2) the increased seed production may lag a year or more behind the driver; and 3) mast seeding may be subject to modifying influences, such as plant health, nutrient status, and productivity. The intensity of observations at LTER sites makes them ideal for this type of study, in which many factors might come into play.

Mast seeding affects not only the structure of plant communities, but also the size of food sources for birds and mammals. In a classic example of the importance of mast seeding, mast years of acorns typically drive higher-than-normal populations of white-footed mice — which in turn support large populations of ticks and an increase in the prevalence of Lyme disease, which is carried by the ticks.

A 2000 NCEAS synthesis group on mast seeding made significant progress on the topic, but mathematical techniques for quantifying synchrony have improved dramatically in the past 20 years and this new research team — led by Dr. Jalene LaMontagne, a population ecologist and quantitative biologist at DePaul University, together with Dr. Elizabeth Crone, a population ecologist at Tufts University, and Dr. Miranda Redmond, a forest ecologist at Colorado State University — is eager to apply these new approaches.

LTER synthesis groups incorporate data and researchers from many sources, both inside and outside the LTER Network. The 2021 projects were selected by a panel of LTER and non-LTER researchers and will begin their work over the next few months. In addition to travel and meeting support, participants will receive training and assistance with reproducible research techniques and best practices for collaboration. The LTER Network Office expects to hold additional competitions for synthesis working groups in 2022.

LTER logoThe Long Term Ecological Research (LTER) Network links nearly 30 National Science Foundation-funded programs applying long-term observation, experiments, and modeling to understand how ecosystems function over decades. LTER research integrates many disciplines to understand ecological processes as they play out at individual sites, while synthetic studies reveal broader principles that operate at a global scale. The LTER Network Office is the hub of scientific synthesis, education, and outreach activities for the Network. 

NCEAS logoThe National Center for Ecological Analysis and Synthesis (NCEAS) is an independent research affiliate of the University of California, Santa Barbara, with a global network and impact. They work to accelerate scientific discoveries that will enhance understanding of the world and benefit people and nature, as well as to transform the scientific culture to be more open, efficient, and collaborative.