Monthly Archives: January 2014

Jennifer Blake-Mahmud on National Geographic

Jennifer in Costa Rica

Jennifer, a past undergraduate from our lab, took the OTS graduate field course in Costa Rica, and appears in an article about the course on the NGS web site.

http://newswatch.nationalgeographic.com/2014/01/29/out-of-their-element-science-students-produce-films-in-costa-rica/

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Factors structuring tidal salt, brackish and fresh marsh plant communities

A new paper by Hongyu Guo, Kazik, Zhenjiang and Steve looks at how tidal marsh plant communities are structured using statistical methods to identify how deterministic the communities are. The bottom line is that tidal salt and brackish marsh communities are highly deterministic, likely reflecting the strong abiotic stresses and competitive interactions that have been previously identified in these systems. But tidal fresh marsh communities were much less deterministic, probably due to higher species richness, recruitment from seed, and lower abiotic stress. At the scale of the estuary, deterministic processes structure plant communities along the salinity gradient from tidal fresh to tidal salt marshes, as shown by previous experimental studies.

Full citation: H. Guo, K. Wieski, Z. Lan and S. Pennings 2014. Relative influence of deterministic processes on structuring marsh plant communities varies across an abiotic gradient. Oikos 123:173-178.Image

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Healthy rivers make healthy marshes

A new paper by Kazik Wieski and Steve Pennings in Ecosystems shows that Spartina alterniflora production in Georgia increases in years with high discharge from the Altamaha River during the late spring and summer. We examined 12 years of fall biomass data from 9 sites in the GCE-LTER domain, and found that river discharge increased productivity at all the sites, with plant biomass up to 3 times larger in high- versus low-discharge years. Coastal rainfall and year to year variation in sea level also affected plant growth to some extent, but not as consistently as river discharge. It is likely that all three factors affected porewater salinity, and that salinity was the proximate driver of plant production. We also found that hotter summers had lower productivity, because temperatures in GA can exceed the thermal optimum for Spartina alterniflora.

Kazik in marsh

Future work by the GCE-LTER will use LandSat data to extend the S. alterniflora productivity record back in time (O’Donnell and Schalles) and will look at variation in productivity in other common marsh species (Pennings).

Kazimierz Wieski and Steven C. Pennings, 2013, Climate Drivers of Spartina alterniflora Saltmarsh Production in Georgia, USA. Ecosystems. DOI: 10.1007/s10021-013-9732-6.

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