LTER Key Research Findings

Among the many research results from LTER sites, some findings stand out as being particularly important to achieve the LTER goal of providing information to conserve, protect, and manage the nation's ecosystems. Short descriptions of key findings at each site emphasize the importance of long-term data in understanding the pace and pattern of ecological change.

Climate variability and change (KNZ LTER)
Climate is a critical driver of grassland structure and function. Grasslands occur in areas that are prone to occasional drought and are characterized by highly variable patterns of rainfall, both between (inter-annually) and within (intra-annually) years. North American grasslands were formed by climate changes originating during the Miocene-Pliocene transition, and their present day...
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Fire and Grazing (KNZ LTER)
Understanding the ecological effects of fire and grazing in grasslands is an important aspect of research at the Konza Prairie (KNZ) LTER site. The tallgrass prairies of North America were shaped by natural disturbances that included periodic fires and the activities of ungulate grazers, and these remain important processes in tallgrass prairie and other grasslands around the world. In order to...
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Grassland stream ecology (KNZ LTER)
Grasslands and wooded grasslands cover around 40% of the Earth’s terrestrial surface and more than ¼ of global runoff originates from these systems. Yet, surprisingly little is known about the ecology and unique properties of streams that link grasslands to downstream habitats. Understanding the ecology and ecosystem services provided by small headwater streams in the Great Plains region is...
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Restoring Grasslands (KNZ LTER)
Restoration ecology seeks to repair the diversity and dynamics of ecosystems degraded by human activities. Restoration studies in tallgrass prairie have become a core part of the Konza Prairie LTER (KNZ) program over the last decade, and are particularly timely because human activities have resulted in widespread loss and degradation of tallgrass prairie and other temperate grasslands. Here we...
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Woody plant encroachment (KNZ LTER)
Predicting how ecosystems will respond to forecast environmental changes and to evaluate the consequences of those responses is a major challenge for ecologists today. One of the most prevalent contemporary land-cover changes is woody plant encroachment into grasslands and increased cover of shrubs and trees in grasslands and savannas. Causes of increased woody plant abundance may vary in...
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Hurricanes, Humans, and Future Ecosystems (LUQ LTER)
Ecosystems are increasingly subjected to combined natural and human disturbances. Since 1990 in Puerto Rico we have been studying human and hurricane disturbance and their interactions in a tropical forest. The work takes place on the 16-ha Luquillo Forest Dynamics Plot (LFDP) in the Luquillo Mountains. Part of the plot was logged or farmed up until the 1930s (Fig. 1). On the rest of the plot...
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New Pathways (LUQ LTER)
Nitrogen is a key resource for plants and animals. Thus there has been much research on what controls nitrogen retention and loss in terrestrial ecosystems. But much uncertainty remains, especially with regard to gaseous nitrogen losses. This is particularly troubling in the context of human modification of the nitrogen cycle, which is dramatically increasing nitrogen pollution, runoff, and the...
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Tropical Carbon Cycling (LUQ LTER)
Tropical forests (Fig. 1) absorb more atmospheric carbon dioxide (CO2) than any other terrestrial biome globally. They also account for about 30% of global net primary production (i.e., carbon uptake) in about 17% of the land area. These ecosystems play a key role in the global carbon cycle, but there is growing concern that global warming could decrease the ability of tropical forests to...
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Chain Reaction (MCM LTER)
MCM scientists are contributing to the recognition that ecosystem responses to climate change are not necessarily gradual or directional, especially in low diversity ecosystems where harsh environmental conditions dominate (Fig. 1). For example, in soil ecosystems in the McMurdo Dry Valleys in Antarctica there are only a few soil nematode species, compared to the hundreds in a temperate soil...
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Fast Geochemistry (MCM LTER)
The ubiquitous dissolution of soils and sediments results in dissolved loads of major ions and nutrients to streams. In most temperate watersheds, the rate of weathering is generally positively correlated to temperature and precipitation. In the cold and dry McMurdo Dry Valleys of Antarctica, dilute glacial melt water generated during 8-10 weeks in the austral summer flows into well-defined...
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Habitats on Ice (MCM LTER)
Cryoconite (cold dust) holes are small ~10 cm diameter, water-filled, cylindrical holes (~10^3 cm) found in the glacier surface. Often, these holes contain algae. While common to glaciers globally, those in the Dry Valleys of Antarctica are covered by ice. Sand patches on the ice surface, blown on to the glacier by wind, melt into the ice. Once below the surface, the sand absorbs energy from the...
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Organics From Microbes (MCM LTER)
The McMurdo Dry Valleys and other desert oases on the coast of East Antarctica are essentially "plant-free" environments. As a result the dissolved organic material (DOM) present in the water of the dry valley lakes and streams is derived only from the breakdown of biomass originally produced by microbes, e.g. algae and bacteria. These microbes grow in the water column of the lakes, such as...
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Waiting in Winter Darkness (MCM LTER)
The permanently ice-covered lakes studied in the MCM can be considered as an oasis for life in this cold desert because they are some of the few habitats on the Antarctic continent that contain year-round liquid water. Strong microbial linkages have been defined in all of thse lakes and point to the tight coupling of carbon and other nutrients and the reliance of the system on phytoplankton...
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Coral Reef Observing Network (MCR LTER)
Coral reefs are complex, biologically diverse and highly valued ecosystems that are under increasing threat from both natural and human-induced disturbances. Timely ecosystem observations about the condition of coral reefs on a range of temporal and spatial scales are essential to assist policy makers and resource managers to address the challenges of their management and conservation, as well as...
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Diversity Matters (MCR LTER)
As the effects of human society on the global environment intensify, notably to elevate atmospheric concentrations of carbon dioxide, coral reefs and reef-forming corals find themselves the colloquial "canary in the coal mine" in providing early warning of the dire effects of these changes. Nearly 30 years ago, scientists raised the alarm over the effects of unseasonably warm seawater in causing...
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Fish Grow Coral (MCR LTER)
There is an obvious relationship between coral and the tropical fishes that live in close association with them -- in general the more coral there is on a reef, the more fish will occur there. While it is clear that the amount of coral habitat on a reef influences the number of fishes present, MCR scientists have found that the reverse often is true as well -- the number of coral-dwelling fishes...
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Managing For Resilient Coral Reefs (MCR LTER)
Tropical reefs around the world are being disturbed more and more often by events that greatly reduce the amount of living coral on reefs. In some cases the disturbed reef returns to its previous state of high coral cover; however, in other instances, the reef becomes dominated by persistent stands of macroalgae that greatly slow or prevent the re-establishment of coral. Macroalgae can overgrow a...
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Carbon Storage (NTL LTER)
Scientists studying the global carbon cycle have primarily focused on quantifying storage and fluxes of the ocean and the terrestrial landscape, often to the exclusion of wetlands, lakes, rivers, and reservoirs. One of the first hints that aquatic systems may play a larger than expected role in regional and global-scale carbon dynamics was the observation of CO2 supersaturation in a world-wide...
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Lakes In The Landscape (NTL LTER)
NTL researchers developed the concept of "lake landscape position" -- how a lake's location within the larger landscape provides a basis for understanding lake characteristics and dynamics. Lakes can receive water from precipitation, surface runoff (streams and rivers) and groundwater. In general, lakes higher in the landscape (i.e., at greater elevations) receive a larger percentage of their...
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Managing Water Quality in a Changing World (NTL LTER)
Eutrophication, the over-enrichment of lakes and rivers with nutrients, causes toxic algae blooms, deoxygenation, foul odors, fish kills, and heavy economic losses to communities that depend on clean water for drinking, industrial use, or recreation. The fix-up sounds simple: stop adding nutrients to the water. However, lakes and rivers are embedded in complex systems of people and nature,...
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Real World Solutions (NTL LTER)
Some of the most pressing ecological issues are global in nature. Highly valued ecosystem services, such as those provided by lakes and reservoirs, will come increasingly under stress in the future. Studying lake ecosystems at the continental, or even global scale requires a broadly distributed network of sites that can leverage local knowledge, data, and expertise toward the goal of...
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Science, Scenarios and Surprise (NTL LTER)
Ecological forecasting and long-term ecological research are synergistic. Long-term data are essential for calibrating models, and forecasts are hypotheses to be tested by long-term research. Existing models are limited in scope. Generally they provide predictions of biological, biogeochemical or physical trajectories of ecosystems, given specified inputs including human actions....
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Tracking Ice Cover (NTL LTER)
The annual timing of the formation and disappearance of ice in aquatic systems represents a valuable proxy for climate change and provides an early warning for potential responses that may occur within these ecosystems. The strength as a climate proxy includes the broad spatial distribution and regional, continental, and global abundance of sites, the annual resolution of the data, data records...
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Air Pollution (NWT LTER)
Alpine environments are sensitive indicators of air pollution. By combining monitoring of high-elevation ecosystems and field experiments, NWT scientists have determined that current levels of nitrogen pollution associated with industry and agriculture are altering alpine plant diversity and are polluting lakes and streams, and may soon acidify soils. Long-term ecological measurements and...
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Early Warning Signs (NWT LTER)
NWT research indicates that alpine ecosystems provide important early warning signs of global climate change. Alpine plants and animals survive on the razor's edge of environmental tolerances, making them more sensitive to changes in climate than downstream ecosystems. Signs of stress in the American pika: The hamster-sized American pika or "rock rabbit" is an icon of rocky landscapes that...
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