What drives the invasion of non-native wetland plants? What are the best techniques for controlling wetland invasives?
Synthesis across species
Karin and her collaborator Dr. Carrie Reinhardt Adams addressed these research questions in a broad way by conducting a literature review and meta-analysis of published invasive species control experiments. You can read about our findings here. Now we are trying to take some of our own advice on how to conduct more rigorous invasive plant control experiments with our work with Phragmites (see below).
Diane Menuz, a recent graduate of the lab, looked at broad patterns of plant invasion in riparian areas in the eastern Columbia and western Missouri River Basins using species distribution models. She found that climate was the most important predictor of species distributions across the suite of her 11 study species, while disturbance and soil factors were important for only a subset of species. These findings have important implications for riparian management and in the face of climate change. Her manuscript is currently in revision at Biological Invasions.
Diane Menuz, a recent graduate of the lab, looked at broad patterns of plant invasion in riparian areas in the eastern Columbia and western Missouri River Basins using species distribution models. She found that climate was the most important predictor of species distributions across the suite of her 11 study species, while disturbance and soil factors were important for only a subset of species. These findings have important implications for riparian management and in the face of climate change. Her manuscript is currently in revision at Biological Invasions.
Phragmites australis in the Chesapeake Bay and Utah
The non-native lineage of Phragmites australis is invasive in many parts of North America including the Chesapeake Bay and Utah. We have been addressing a number of questions in our attempt to better understand the spread of this invasive plant as well as how best to control it.
In the Chesapeake Bay, we have conducted a number of studies looking at modes of reproduction of Phragmites, the importance of cross-pollination to viable seed production, the role of nutrient enrichment in increased sexual reproduction, and the presence of Phragmites and native plants in wetland seed banks. You can find a number of papers summarizing our work on our Publications page.
More recently, Ph.D. student Eric Hazelton along with Karin, Dr. Dennis Whigham, and Dr. Melissa McCormick, has been looking at the restoration potential ofPhragmites-dominated wetlands in the Chesapeake Bay across watersheds with differing land uses. He has identified 8 watersheds where he has a "natural" wetland site (reference site), a Phragmites-dominated site that will be left intact, and a Phragmites-dominated site that was sprayed in fall 2011. At each site he is monitoring changes in wetland vegetation, Phragmites sexual reproduction and genetic diversity (clonal richness), and environmental conditions such as nutrient and salinity levels. Some of the hypotheses that Eric is testing are that: (1) Phragmites-sprayed sites (the restorations) in forested watersheds will recover to more closely resemble the nearby reference site than sprayed sites in more disturbed and nutrient rich developed watersheds; and (2) the process of restoration may increase local levels of genetic diversity in Phragmites patches, thereby having a positive effect on Phragmites cross-pollination and viable seed production.
In Utah, Karin has collaborated with Dr. Karen Mock to look at differences in reproductive mode and dispersal in native vs. non-native Phragmites (click here for the resulting publication). Karin is also collaborating with Dr. Mac McKee and Dr. David Rosenberg at the USU Water Lab to look at small spatial and fine temporal changes in Phragmites cover at the Bear River Migratory Bird Refuge. Using the AggieAir's UAVs (unmanned aerial vehicles), we have acquired 15-cm resolution imagery to track Phragmites expansion across years and multiple times within a year.
Meanwhile, Masters student Lexine Long in collaboration with Karin and Dr. Christopher Neale has been processing remotely sensed images taken of the eastern third of the Great Salt Lake to get a present-day estimate of Phragmites coverage. The classified vegetation map can be seen here (see picture below). She will next use these data of Phragmites cover for species distribution modeling to better understand what factors best explain Phragmites' current distribution and to predict where it may expand to in the future. Ultimately, these data will allow her to develop a prioritization framework for Phragmites control in the Great Salt Lake watershed.
One of the biggest challenges for managers having to deal with Phragmites in Utah and across North America is knowing how to best control it. This is particularly challenging given recent work that shows that invasive Phragmites spreads largely by seeds, while the most common control strategy is to spray in the fall, once seeds may have already matured and begun to disperse. To that end, Masters students Christine Rohal and Chad Cranney are evaluating potential strategies for control of small patches and large stands of Phragmites, respectively. Because these different types of Phragmites invasions have different logistical constraints, we believe it is important to consider control strategies for these different spatial scales. Christine has six sites along the Great Salt Lake where she is comparing the effectiveness of:
Chad has four sites where he's applying:
(left: a mowed Phragmites stand; right: a black plastic treatment)
In the Chesapeake Bay, we have conducted a number of studies looking at modes of reproduction of Phragmites, the importance of cross-pollination to viable seed production, the role of nutrient enrichment in increased sexual reproduction, and the presence of Phragmites and native plants in wetland seed banks. You can find a number of papers summarizing our work on our Publications page.
More recently, Ph.D. student Eric Hazelton along with Karin, Dr. Dennis Whigham, and Dr. Melissa McCormick, has been looking at the restoration potential ofPhragmites-dominated wetlands in the Chesapeake Bay across watersheds with differing land uses. He has identified 8 watersheds where he has a "natural" wetland site (reference site), a Phragmites-dominated site that will be left intact, and a Phragmites-dominated site that was sprayed in fall 2011. At each site he is monitoring changes in wetland vegetation, Phragmites sexual reproduction and genetic diversity (clonal richness), and environmental conditions such as nutrient and salinity levels. Some of the hypotheses that Eric is testing are that: (1) Phragmites-sprayed sites (the restorations) in forested watersheds will recover to more closely resemble the nearby reference site than sprayed sites in more disturbed and nutrient rich developed watersheds; and (2) the process of restoration may increase local levels of genetic diversity in Phragmites patches, thereby having a positive effect on Phragmites cross-pollination and viable seed production.
In Utah, Karin has collaborated with Dr. Karen Mock to look at differences in reproductive mode and dispersal in native vs. non-native Phragmites (click here for the resulting publication). Karin is also collaborating with Dr. Mac McKee and Dr. David Rosenberg at the USU Water Lab to look at small spatial and fine temporal changes in Phragmites cover at the Bear River Migratory Bird Refuge. Using the AggieAir's UAVs (unmanned aerial vehicles), we have acquired 15-cm resolution imagery to track Phragmites expansion across years and multiple times within a year.
Meanwhile, Masters student Lexine Long in collaboration with Karin and Dr. Christopher Neale has been processing remotely sensed images taken of the eastern third of the Great Salt Lake to get a present-day estimate of Phragmites coverage. The classified vegetation map can be seen here (see picture below). She will next use these data of Phragmites cover for species distribution modeling to better understand what factors best explain Phragmites' current distribution and to predict where it may expand to in the future. Ultimately, these data will allow her to develop a prioritization framework for Phragmites control in the Great Salt Lake watershed.
One of the biggest challenges for managers having to deal with Phragmites in Utah and across North America is knowing how to best control it. This is particularly challenging given recent work that shows that invasive Phragmites spreads largely by seeds, while the most common control strategy is to spray in the fall, once seeds may have already matured and begun to disperse. To that end, Masters students Christine Rohal and Chad Cranney are evaluating potential strategies for control of small patches and large stands of Phragmites, respectively. Because these different types of Phragmites invasions have different logistical constraints, we believe it is important to consider control strategies for these different spatial scales. Christine has six sites along the Great Salt Lake where she is comparing the effectiveness of:
- (1) summer glyphosate + winter mow;
- (2) fall glyphosate + winter mow;
- (3) summer imazapyr + winter mow;
- (4) summer mow, fall glyphosate, + winter mow;
- (5) summer mow + black plastic;
- (6) untreated control
Chad has four sites where he's applying:
- (1) summer glyphosate + winter mow;
- (2) fall glyphosate + winter mow;
- (3) summer imazapyr + winter mow;
- (4) fall imazapyr + winter mow;
- (5) untreated control
(left: a mowed Phragmites stand; right: a black plastic treatment)