• NSF awards $5.3 million in 59 grants to study effects of recent hurricanes
• After the 2016 El Niño, coral reefs in Moorea are thriving -- why?
• Cometh the devil weed. What's the best way to slay it?

• Washington Post. One of the Oldest Climate Change Experiments Has Led to a Troubling Conclusion
• Scientific American. Hurricanes Harvey and Irma Send Scientists Searching for Data
• Earther.com. After Maria, Puerto Rico's Endangered Parrots Face an Uncertain Future
• Wired. Heating Dirt Could Cause a Runaway Rise in Carbon Emissions
• Earther.com. After Irma, Pummeled Everglades Shows Signs of Resilience
• Eurekalert! Baltimore Ecosystem Study partners with Baltimore City Public Schools
• UVA Today. Video: Preserving Life on a Sandbar

Although the modern “American Dream” is no longer defined by white picket fences, this perception of the “ideal” homestead still holds some influence on cultural norms: cookie-cutter houses lining a cul-de-sac, each with a pristinely manicured green lawn. A collaborative study of residential lawns near several LTER sites found that the quest for this suburban ideal still pervades residential development and management throughout America. So much so, in fact, that the composition of plant communities in residential lawns across the different regional sites had more in common with each other than they did with their local, unmanaged counterparts.   

The seven cities chosen for the study were selected in order to represent the dramatically different climates and vegetation types across America, making the similarities in residential lawn communities even more striking. Turfgrasses comprised the majority of residential lawn samples, and although individual species differed between regional sites, they shared similar community composition.

The study also found that different regional sites shared the same weed species, indicating that other factors outside of similar human planting practices are contributing to the narrowing of lawn plant diversity across America. Researchers suggested that the weeds are often present in turfgrass seed sources, and that lawn maintenance and disturbed soils create a distinct environment in which these specific species are successful.

Demographic components of these residential areas were also incorporated into the study. Researchers found that higher income households kept lawns with significantly less plant diversity than those of lower income households. This is likely due to the fact that high income households can afford to spend more on lawn care services that can remove any unwanted newcomers to the lawn. Conversely, the same high income households often kept gardens that yielded very high plant diversity—though these flora were often nonnative, and accounted for a much smaller area of coverage than the turfgrass lawns.

This study demonstrates that these lawn species largely belong to a continental-scale lawn community that is severely lacking in diversity and was shaped by both climatic factors and lawn management.

Radio transmitters have moved beyond the days of talking to your friends through walkie talkies. They are now being used to track alligators, the rulers of the swamp, to learn more about their movements between freshwater and marine environments. Once attached, the GPS and radio transmission devices can track the alligator’s movements for up to four months. With the use of these devices, scientists from the Georgia Coastal Ecosystems LTER were able to determine that time spent in each ecosystem is dependent on multiple physical factors within the environment, such as tidal range and temperature.   

Unlike their cousins the crocodiles, alligators do not have salt glands and therefore lack the traits necessary to survive full-time in salt water. They move back and forth between marine and freshwater ecosystems to feed and rebalance their salt levels. By tracking the alligators, the scientists discovered the most important factor influencing the duration of trips to the marine environments was maximum water depth, a proxy for tidal range.

The team found that alligators remained in marine habitats for longer periods of time around spring tide events, where there is the greatest difference between high and low tides. Spring tides mean one thing for these alligators: more food. Due to the extreme high and low tidal heights, water speeds increase and displace common marine prey such as small fish and crustaceans. Additionally, the extremely low water depths isolate and concentrate aquatic prey. Both of these spring tide factors make it easier for the alligators to feed and explains why they spend more time in marine environments around spring tides.

Other physical factors contribute to patterns of movement, such as temperature and precipitation, which are associated with the need to balance salt and water intake. By understanding which factors contribute to the movement between ecosystems, managers will gain a better understanding of the alligator’s ecological impact on coastal ecosystems and be able to target conservation priority areas for the alligator.

 —Erin O'Reilly

While Florida, Texas, and Puerto Rico recover from a devastating hurricane season, another natural disaster rages on the other side the continent. Following a record-hot summer and dry conditions, the northwestern United States and Canada have experienced one of the most intense fire seasons on record. As global temperatures rise, scientists will need a better understanding of how high-latitude, boreal forest ecosystems respond to changing fire regimes. A study by Bonanza Creek Long Term Ecological Research (BNZ-LTER) researchers found that boreal wildfires can displace dominant tree species and alter understory bryophyte populations, ultimately changing forest composition, structure, and function.   

Boreal forests in Alaska’s interior are mainly composed of coniferous trees, whose open canopy and low leaf litter allow bryophytes to thrive and carpet the forest floor. Bryophytes are non-vascular plants, such as liverworts, hornworts, and mosses that dominate the understories of boreal forests. These small plants play an important role in maintaining ecosystem health and resiliency since they help build organic layers, enhance soil insulation, retain soil moisture, increase soil nitrogen, and re-establish permafrost after fire events. Ecological disturbances, such as fires, can alter canopy composition, changing bryophyte communities and thus forest ecosystem structure, function, and resiliency.

The researchers measured bryophyte abundance and species composition, as well as soil organic layers, moisture, and temperature in 83 stands in Alaska’s interior forests. All 83 stands had similar environmental conditions, but ranged from 8 to 163 years in post-fire age and varied in canopy dominance between coniferous, deciduous, and mixed forest types.

During the early successional stage (6 to 20 years after the fire), all 83 sites had high bryophyte abundance and similar species composition. However, during the mid- to late-successional stages (over 20 years after the fire), increased leaf litter production in deciduous forest stands resulted in fewer bryophytes. Coniferous stands in the mid to late successional stage had more bryophyte abundance, but tended to be dominated by feather mosses, which enhance soil organic layers, nitrogen fixation, carbon storage, permafrost stability, and further support coniferous abundance.

As boreal wildfires increase in their severity and frequency, the potential to shift towards mixed and deciduous tree dominance could be reinforced by changes in the understory community.

It’s kind of amazing what you can learn by taking a fresh look at old data. A re-analysis of data from a large and influential decomposition experiment suggests that—at least in arid lands—the degradation of organic matter by light plays a much bigger role than previously understood.  

Back in 1990, an ambitious group of LTER scientists packed ten standard types of leaf and root litter—with widely varying chemistry—into thousands of mesh bags and asked their colleagues at 28 research sites to put them out in the field to decompose. Collected and analyzed every year over the next decade, this rich data set from the Long-term Intersite Decomposition Experiment Team (LIDET) study had tremendous influence on how ecologists understand and predict decomposition.
  
The “biotic” model that emerged from the LIDET study considered the ratios of cellulose, lignin, and soluble carbon in litter, as well as initial nitrogen content, climate, and soil conditions. It did a good job of predicting decomposition for most sites and the approach was incorporated into many standard ecosystem models.
In the nearly two decades since the LIDET results appeared, photodegradation of organic matter has come to be recognized as a potentially important driver of decomposition, especially at arid sites. This new study uses the LIDET data from three arid sites in the original study to evaluate 59 models that incorporate photodegradation.

One model stood out as a much better descriptor of decomposition dynamics for these sites. Its success suggests that, even now, the current understanding of photodegradation is incomplete. Key features of this successful model include losses from cellulose and lignin pools that do not accrue to the fast-turnover labile pool. It also allowed UV radiation to slow microbial decomposition rates and soil infiltration to “shade” litter from the effects of UV light.

The two types of models performed similarly in the first four years of decomposition, but diverged significantly in years 4-10, with the new photodegradation model coming much closer to the measured results. As drylands expand and get drier, better predictions of carbon turnover will depend on better understanding of photodegradation. Good thing they knew where to find that data!