A couple new papers from the Pennings lab, available online in “early view” format. Wenwen and Steve published a massive synthesis of many years of monitoring of Spartina alterniflora stem height and density at the GCE LTER site. The bottom line is that all the variation across zones, sites and years in Spartina alterniflora height and flowering status can be understood as resulting from a couple simple allometric rules.
Liu, Wenwen, and S. C. Pennings. 2019. Self-thinning and size-dependent flowering of the grass Spartina alterniflora across space and time. Functional Ecology. DOI: 10.1111/1365-2435.13384.
Youzheng and Steve published a study of latitudinal patterns in nematode diversity in Chinese coastal wetlands. All the field work was done by Youzheng before coming to Steve’s lab, and Steve helped guide the analysis, presentation and writing. The bottom line is that, in native (Phragmites) wetlands, nematodes display the canonical pattern of lower diversity at high latitudes. But in wetlands dominated by the introduced Spartina alterniflora, there is no latitudinal pattern in nematode diversity. The introduced plant somehow disrupts the normal latitudinal patterns. This summer Youzheng and Steve will start writing a paper about what happens when you sample nematodes across latitude in the native range within the United States. Stay tuned!
Zhang, Y., S. C. Pennings, B. Li, J. Wu. 2019. Biotic homogenization of wetland nematode communities by exotic Spartina alterniflora in China. Ecology 100(4):e02596. 10.1002/ecy.2596.
Three new papers of note from the Pennings lab:
Huy Vu and Steve published a paper in Ecosphere about how the threat of predators affects herbivory by Sesarma crabs. Specifically, whether they feed more aboveground or belowground. Ecosphere 9(2):e02107.
Chelse Prather, Angela Laws, Juan Cuellar, Steve and Chelse’s students published a paper in Ecology Letters about how grassland insects are co-limited by macronutrients and sodium. Ecology Letters 21:1467-1476.
Angela, Chelse and Steve published a paper in Journal of Animal Ecology about whether grasshopper composition or diversity determines effects on plant communities. JAE 87:1727-1737.
Good work everyone!
Spartina alterniflora, the dominant plant of Atlantic and Gulf coast salt marshes in the United S tates, is introduced in China, where it has spread to occupy a geographic range similar to that in its native range in North America. Liu et al 2017, Provenance-by-environment interaction of reproductive traits in the invasion of Spartina alterniflora in China, Ecology 98(6):1591-1599, show that, in China, plants at high latitudes are morphologically different and set more seed than plants at low latitudes. Common garden experiments showed that the morphological differences are largely plastic, due to environmental conditions, but that the differences in sexual reproduction are genetic but expressed most strongly in high-latitude gardens (hence the provenance by environment interaction). In the field, the mechanisms of invasion differ by latitude: Spartina spreads by seeds and seedlings at high latitudes but clonal expansion at low latitudes. The lead author, Wenwen Liu, will be spending a year in Steve Pennings’ laboratory starting this fall, and hopes to learn more about latitudinal variation in sexual reproduction in Spartina alterniflora in its native range. Surprisingly, we know almost nothing about this topic.
Pennings in special noodle shop. Strong contemplating fate of Chinese puppy. Zhang, Liu, Strong, Pennings editing manuscript.
Shanze Li and Steve Pennings recently published a paper on how the timing of wrack disturbance determines its effects on Spartina alterniflora and on stem-boring herbivores of Spartina. Plants completely recover from disturbance early in the season in terms of growth, and early disturbance actually stimulated flowering. Plants did not recover from disturbance later in the season, and flowering was suppressed. Plants disturbed late in the season also had a low frequency of stem-boring herbivores. The paper was featured on the cover of the journal Ecosphere, and is open access: http://onlinelibrary.wiley.com/doi/10.1002/ecs2.1675/full
Our long-standing experimental project on the spread of mangroves in the Gulf Coast has produced its first paper. Hongyu led the effort, which describes how mangrove cover affects microclimate, marsh vegetation, wrack disturbance, sedimentation, soil organic content, and bird use of the wetlands. Ecology 98:762-772.
Top photo: I don’t know his name, but this grizzled veteran of the mangroves assisted me with the water quality instrument.
Bottom photo: Our noble leader Hongyu hard at work measuring mangroves.
The snail Littoraria irrorata is one of the most important invertebrates in US coastal salt marshes on the Atlantic and Gulf coasts. A number of papers have shown that the BP Deepwater horizon oil spill killed adult Littoraria. But did the plume of oil in the water affect larvae that were due to become the next generation of snails? This is hard to address because no-one took the right samples of plankton or of newly-recruited snails the year of the oil spill. So Steve and colleagues took an indirect approach. Littoraria size-frequency distributions are bimodal, with a peak of small snails representing snails in their first year and a peak of larger snails representing all the older snails (they may live as long as 20 years). By examining the ratio of the two peaks, you can get a sense of whether the 1 year old age class is at normal densities or reduced. Size-frequency distributions are commonly measured, so there were lots of literature data on “normal” size-frequency distributions for Littoraria from both the Gulf and the Atlantic Coast. Comparing these distributions between geographic regions and among years, they found: 1) recruitment appeared to be greater in the Atlantic than the Gulf, 2) there was a dramatic drop in 1 year old snails in Louisiana in 2011, consistent with the possibility that the 2010 oil spill killed larvae in the water (this drop was at sites that were not oiled, so it was not due to post-recruitment mortality), and 3) this drop in 2011 did not happen in the Atlantic, so it wasn’t simply due to it being a “bad year” everywhere–it was a bad year in Louisiana.
Coauthors included Pennings lab alumna Carolin McFarlin, GCE-LTER colleagues Merryl Alber and Dale Bishop, and old UGAMI colleague Keith Walters.
The paper is online and open access:
Pennings, S. C., S. Zengel, J. Oehrig, M. Alber, T. D. Bishop, D. R. Deis, D. Devlin, A. R. Hughes, J. J. Hutchens, W. M. Kiehn, C. R. McFarlin, C. L. Montague, S. Powers, C. E. Proffitt, N. Rutherford, C. L. Stagg, K. Walters. 2016. Marine ecogregion and Deepwater Horizon oil spill affect recruitment and population structure of a salt marsh snail. Ecosphere 7(12)e01588, DOI: 10.1002/ecs2.1588.
Kurt Reinhart was part of the lab back in the old days when I was at Sapelo full time. He’s now working for the USDA Agricultural Research Service and recently co-authored a paper in Science on plant-soil feedbacks. The bottom line was that, for 550 populations of 55 species of trees across the USA, trees with arbuscular mycorrhizae had negative soil feedbacks whereas trees with ectomycorrhizae had positive soil feedbacks. Very cool stuff. Check it out:
Bennett et al. 2017, Plant-soil feedbacks and mycorrhizal type influence temperate forest population dynamics. Science 355:181-184.
Kurt studying something. From his website. Looks scientific.