Key Findings

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 »

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 »

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 »

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 »

CDR Experiment E141 - BioCON (Biodiversity, CO2, and N) / TeRaCON (Temperature, Rainfall, CO2, and N) experiments. In two nested global change experiments, nitrogen (N) and soil moisture jointly constrained the response of biomass production to elevated CO2 over the long term. When both water and N were limited, elevated CO2 did not affect plant... Read more »

CDR Experiment E002 - Long-Term Nitrogen Addition to Disturbed Vegetation. Chronic N addition reduced plant species richness and led to the local extinction of species with efficient N use. Species richness returned to its original level after ceasing the addition of low levels of N. These changes in composition were readily reversed after low levels... Read more »

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 »

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 »

Eddy covariance tower at SRS-6 in lower Shark River before (left) and after (right) Hurricane Irma. Long term data reveal that multiple types of disturbances — including cold snaps, fires, droughts, floods, and tides — play a strong role in shaping coastal ecosystems. Tropical storms can be beneficial by connecting upstream and downstream food webs... Read more »

Dr. Greg Starr and Dr. Justin Cummings working on the eddy covariance and meteorological tower near TS/Ph-1b in Taylor Slough. Rising seas can stimulate the inland transgression of mangroves and amplify carbon gains (as observed in historic carbon budgets based on long term flux data, paleoecology, and remote sensing). However, FCE LTER studies, experiments, and... Read more »

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 »

Although estuaries are small in area, they play an outsized role in the global carbon budget. Estuaries are net sources of CO2 to the atmosphere and coastal ocean, and net sinks for oceanic and atmospheric O2. This finding challenges the simplistic treatment of estuaries in global carbon models, and suggests that interactions between river discharge,... Read more »

Ammonia oxidizing archaea peak in the summer and play a previously-unknown role in driving estuarine nitrogen cycling. Ammonia-oxidizing archaea (AOA) convert ammonium into nitrite, but little is known about the population dynamics of this relatively new addition to the nitrogen cycle. Research from GCE LTER found that mid summer blooms of AOA coincide with a... Read more »

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 »

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 »

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 »

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 »

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 »

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 »

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 »

The streams at Hubbard Brook are closely interconnected with the forests around them. Ecological theory led us to expect that in the period that we have been measuring the stream chemistry (1963-present), stream nitrate concentrations should have increased because of the continuing deposition of air pollutant nitrogen on the ecosystem, and because the forests have... Read more »

Hubbard Brook researchers have been studying bird populations for over 50 years. This graph shows the number of birds breeding on a 10-hectare forest plot from 1969-2013. Neotropical migrants show a marked decline early in the record, followed by a stabilization of population more recently. Populations of hort-distance migrants and permanent residents have been stable... Read more »

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 »

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 »

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 »