Iron Supply Broadly Influences Carbon Dynamics

California Current Ecosystem LTER
Sampling with a Trace Metal-clean rosette. Iron supply in the CCE LTER region not only impacts carbon production and export associated with mesoscale circulation features. It also influences phytoplankton growth and species composition at the subsurface chlorophyll maximum layer (SCML), which is a widespread feature during spring and summer. Consistent with regional climate indices, biogeochemical... Read more »

Episodic Events Alter Primary Production and Carbon Export

California Current Ecosystem LTER
R/V Roger Revelle at sea, one of the research vessels CCE uses to investigate primary production, carbon export,and plankton food web structure. Process studies and related time series measurements reveal the under-appreciated importance of episodic events in the oceanic carbon budget. Spatial and temporal perturbations to the carbon cycle can be associated with (sub)mesoscale features... Read more »

Double Integration of Climate Forcing

California Current Ecosystem LTER
The Integrated Pacific Decadal Oscillation index (PDO, red) nicely predicts the variation in an important species of krill (Nyctiphanes simplex, blue) in the CCE site. More than 60 years of zooplankton census data revealed that some populations respond indirectly to climate changes in two stages: first, ocean circulation responds to wind, then the zooplankton population... Read more »

Optimized Satellite Remote Sensing Products

California Current Ecosystem LTER
Satellite-estimated Carbon Export Flux (mg C m-2 d-1) from the new CCE-LTER MERGED product. Several years of effort have led to an important California Current merged satellite-derived 4 km dataset becoming openly available online. The website provides access to regionally optimized remote sensing products and rigorously integrated time series for chlorophyll-a, net primary production, and... Read more »

Biodiversity Increases Ecosystem Productivity and Stability

Cedar Creek Ecosystem Science Reserve
Left =1994 Big Biodiversity herbaceous community plots. Rectangular grid adjacent to lower right corner of Big Bio = 2012 forest biodiversity experiment (FAB l) high density forest plots. Far right gridded section = 2015 forest biodiversity experiment (FAB ll) low density plots. Research in the 1990s demonstrated that more diverse herbaceous plant communities are more... Read more »

Hidden Origins of Coastal Productivity

Florida Coastal Everglades LTER
Ecotone interface between mangrove and sawgrass in lower Shark River Slough Contradicting classical estuary models, FCE LTER research demonstrated that marine nutrient supplies (rather than freshwater nutrient supplies) control coastal productivity gradients via daily tides, episodic storm surges, and hidden groundwater upwelling. Saltwater intrusion amplifies marine pulses by increasing connectivity to the sea and liberating... Read more »

Donor Controlled Food Webs

Florida Coastal Everglades LTER
Adam Rosenblatt (Ph.D. student) holding one of his study subjects, an American alligator, in the Shark River estuary. Coastal food webs are subsidized by episodic and seasonal connections to upstream detrital food supplies. However, top coastal estuary predators show great individual variation in their ability to capitalize on this subsidy — a finding that has... Read more »

Sea Level Rise Alters Wetland Function

Georgia Coastal Ecosystems LTER
A long-term experiment at the GCE LTER revealed that rising sea levels would negatively affect tidal freshwater marshes. Sea level rise is expected to cause salt marshes to extend upstream at the expense of freshwater wetlands, dramatically altering the intertidal landscape. Experimental salinization reduces primary production, reduces plant species diversity, decreases respiration, and leads to... Read more »

River Flow Supports Marsh Production

Georgia Coastal Ecosystems LTER
Long-term monitoring of salt marsh plant production revealed the role of river flow. Long term monitoring, remote sensing, and field experiments showed that dominant estuarine plants grow up to 3 times better in years with low salinities, and that salinity is driven most strongly by river discharge. A high frequency of drought in 1998-2012 led... Read more »

Mobile Predators Structure Communities

Georgia Coastal Ecosystems LTER
Alligators are one of several mobile apex predators in southeastern estuaries. Mobile predators like alligators move between fresh and marine habitats, consume a variety of estuarine prey, and alter the behavior of intermediate predators such as blue crabs. A predator exclusion experiment initiated in 2016 indicated that blue crabs and large fish alter the abundance... Read more »

Carbon Uptake Exceeds Expectations

Harvard Forest LTER
Photo shows the NEON and EMS towers as viewed from the Harvard Forest walk-up tower. Contradictory to theoretical models, forest carbon uptake has accelerated over recent decades in maturing forests, a legacy of 19th century land use, and to a lesser degree, modern increases in atmospheric CO2, nitrogen deposition, temperature, and precipitation. This and many... Read more »

Hemlock is a Foundation Species

Harvard Forest LTER
The hemlock forest, as seen from the Woods Road to the tower. Three decades of research on abrupt declines in pre-European hemlock populations, long term regional measurements of hemlock decline from the invasive insect hemlock woolly adelgid, and the long term Hemlock Removal Experiment confirm that hemlocks are a foundation species. They control forest structure,... Read more »

Microbes Respond to Global Change

Harvard Forest LTER
The soil warming plots at Harvard Forest viewed from atop an adjacent research tower. Decades of experimental soil warming and nitrogen enrichment have induced adaptive responses in microbial communities, abruptly shifting soil carbon dynamics. The experiments have revealed phased responses to warming, oscillating between multi year periods of significant soil carbon loss and phases of... Read more »

Spring is Arriving Earlier

Harvard Forest LTER
Postdoctoral fellow David Basler releases his drone from the top of Harvard Forest's walk-up tower. Over the last 30 years, spring phenology has advanced across eastern North America, increasing photosynthesis and net ecosystem carbon storage, with a small negative feedback to climate change. Beginning in 1990 as a biannual pen-and-paper record of bud break and... Read more »

Calcium is Critical to Forests Exposed to Acid Rain

Hubbard Brook LTER
Ecosystems at Hubbard Brook have been subject to acid deposition for over 50 years, leading to the depletion of important nutrients, such as calcium, from the soils. We experimentally replaced the depleted calcium on an entire watershed by spreading a calcium-containing mineral from a helicopter. There was an almost immediate response by the vegetation, particularly... Read more »

Climate Change Affects Forest Productivity

Hubbard Brook LTER
View of the greening-up canopy of the Bartlett Experimental Forest, a sister site to Hubbard Brook, from the top of a tower where carbon dioxide exchange in measured by the eddy covariance technique. The instrument in the foreground is a sonic anemometer. These measurements of the exchange of carbon dioxide between the forest and the... Read more »

Insights into Vegetation Change

Jornada Basin LTER
2004 mesquite dunelands without grasses and 2008 mesquite dunelands with perennial grasses. The shift from grassland to shrubland is not the only alternative state for desert vegetation. Jornada Basin LTER research has documented: (a) shifts from desertified shrublands back towards native grassland, (b) shifts between different shrubland types, and (c) shifts from grasslands or shrublands... Read more »