Schwinning Lab

Plant Ecology

Yang Tse

Invasive grasses

KR bluestem

Yellow bluestem forms nearly monocultures on Texas rangelands
Johnsongrass seedling

A Johnsongrass seedling grows faster than the seedlings of many native grasses our research showed

The invasion of American grasslands by exotic grasses poses a challenge to grassland management, but also some interesting questions for community ecology: Why is it that some grass species introduced from grasslands in Europe, Asia or Africa have been so exceptionally successful that they were able to dramatically reduce the occurrence of native grasses in American grasslands? For example, in Texas, yellow bluestem (Bothriochloa ischaemum) forms nearly pure stands where previously big bluestem, little bluestem and switchgrass were abundant. At the surface, there seems to be nothing special about the introduced species that would explain their competitive advantage over native species.

In collaboration with Drs Phillip Fay and Wayne Polley at USDA/ARS, and through funding from USDA, we have conducted greenhouse experiments to examine when and how invasive species establish competitive dominance over native species and which traits are involved. Our most recent study examined whether yellow bluestem produces inhibitory allelochemicals to suppress the germination and growth of native species.

On the issue of combating invasive grasses in the field, we have been collaborating with Kelly Lyons at Trinity University in San Antonio. Our most recent study focussed on determining combinations of disturbances that maxmize damage to invasive, while minimizing collateral damage to native species. We found out that yellow bluestem is more sensitive to prescribed burning when it coincides with summer drought conditions. Native species, by contrast, are less sensitive to the combination of summer drought and fire. This seems reasonable given that native grasses have evolved with this fire regime. Our research suggests that invasive species management can be improved by adopting 'more natural' prescribed burn conditions.

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Schwinning, S., Meckel, H., Reichmann, L.G., Polley, H.W., Fay, P.A. 2017. Accelerated development in Johnsongrass seedlings (Sorghum halepense) suppresses the growth of native grasses through size-asymmetric competition. PLOS ONE 12, 20176042 pdf

Reichmann, L.G., Schwinning, S., Polley, H.W,, Fay, P.A. 2015. Traits of an invasive grass conferring an early growth advantage over native grasses. Journal of Plant Ecology DOI:10.1093/jpe/rtw014 pdf

Havill, S. Schwinning, S., Lyons, K.G. 2015. Fire effects on invasive and native warm-season grass species in a North American grassland at a time of extreme drought. Applied Vegetation Science 18:637-649 pdf

 

 

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Lab News

Recent student presentations

Nathan Custer presented on his research at the Ecological Society of America Meeting in Portland. The title of his presentation was "Effect of transplant size on early survivorship". The paper was presented in a session on "Multiple Common Garden Experiments for Meeting Restoration Challenges: Difficulties and Potential Pitfalls" organized by Susanne Schwinning and Lesley DeFalco.

Highlighted publications

Schwinning, S., Meckel, H., Reichmann, L.G., Polley, H.W., Fay, P.A. 2017. Accelerated development in Johnsongrass seedlings (Sorghum halepense) suppresses the growth of native grasses through size-asymmetric competition. PLOS ONE 12, 20176042 pdf

Dammeyer, H.C., Schwinning, S., Schwartz, B., Moore, G. 2016. Effects of juniper removal and rainfall variation on tree transpiration in a semi-arid karst: Evidence of complex water storage dynamics. Hydrological Processes 30: 4568-4581. pdf

Other lab news

The lab welcomes two new graduate students:

Kayla Sustaita will examine the effects of adaptive rotational grazing on soil characteristics.

Logan Maxwell will investigate best restoration practices for abandoned oil and gas exploration fields in Utah.

The lab was awarded two federal grants in 2015:

NSF proposal : DEB-1557176: "Collaborative Research: Hydrological tipping points and desertification of semi-arid woodlands".

The DOD Legacy Award HQ0034-16-2-0006: "Characterizing Mojave Desert shrub ecotypes to establish seed transfer zones for military range restoration".

In the media

In August 2016, Susan was interviewed by Salwa Khan for the Wimberley Valley Radio show "Mothering Earth" Listen to the podcast here.

In September 2013, Susan was interviewed by Alan Knapp on a paper published in Functional Ecology. Listen to the podcast here.

Contact information
Susan Schwinning
601 University Drive
312 Supple Science Bldg
Texas State University
San Marcos, TX 78666, USA
Phone: (512) 245-3753
Fax: (512) 245-8713
Email: schwinn@txstate.edu

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Texas State University

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Comments on the contents of this site should be directed to Susan Schwinning