Last week was the annual workshop of the Grassland Restoration Network. This year, the host was The Nature Conservancy’s Kankakee Sands Prairie/Wetland Restoration Project in Indiana. There were more than 80 people – mainly from Illinois and Indiana this year. As always, the workshop was an opportunity for sharing notes and ideas on prairie restoration, but we also had a particular focus on animal habitat this year.
I felt like the workshop was especially productive and interesting this year, and have several posts worth of information to share from it, but I thought I would start with herpetology. Kankakee Sands is restoring wetland habitat by plugging/filling ditches and also doing some excavation – and then seeding wetland vegetation. One of the goals of that work is to create habitat for reptiles and amphibians.
Dr. Bob Brodman, from nearby St. Joseph’s College, has been sampling amphibians (and reptiles) in the area since before restoration work began, and has observed exponential increases in populations at the restoration site. It’s not really surprising that he’s found higher numbers of amphibian populations, since the Conservancy has added new wetlands to the site. More interesting – and gratifying – is that he’s also finding that the number of amphibian species per wetland is also increasing (as is the total number of amphibian species across the site). In addition, Dr. Brodman has collected data on other amphibians and reptiles that seem to show those species moving in from nearby remnant habitats. Since the major goal of the Kankakee Sands project is to reconnect those disjunct remnant habitats (for vertebrates, invertebrates, and plants) those data are encouraging.
Restoration ecologist Ted Anchor led field trips for this year’s network participants to show the immediate colonization of newly-created wetlands. We looked at two wetlands – one with muck soils and one with almost pure sandy soils. At both wetlands, we saw numerous frogs and toads, though they were much easier to see (and catch) at the more sparsely-vegetated sandy site. Additionally, we were finding both Fowler’s toads and American toads, as well as many that appeared to be hybrids between the two species. Dr. Brodman hypothesized that the temperature and moisture conditions this spring had led to the two populations breeding simultaneously in ponds where they would normally show up a couple of weeks apart.
Ted and Dr. Brodman both discussed some of the important factors to consider when restoring wetland habitat for frogs and toads. In general, they said that most amphibians utilize a buffer zone of upland habitat (about 200 meters wide) around the actual wetland habitat itself. While that habitat is very important, the most critical factor for annual breeding success tends to be the length of time water is present in wetlands each spring/summer because that determines whether breeding occurs and whether tadpoles can successfully mature before their ponds dry up. Water depth and organic matter in the wetlands soils can both affect the length of time that water stays around.
Creating wetlands with varying depths, including at least a few places where it is nearly permanent can help ensure breeding success (though fish and bullfrog populations can be counter-productive, so that can be a tricky line to walk). Most wetland restorations at Kankakee Sands have very sandy bottoms – as do the ones we’ve done along the Platte River in Nebraska. Those sites tend to hold water for shorter times than do sites with more organic matter (or clay). That organic matter will accumulate over time, gradually helping to increase breeding success over time, but again, creating some deeper pools can help in the meantime.
In addition to helping hold water, organic matter may have two other benefits. First, the darker colored soil may improve the effectiveness of the dark-colored tadpoles’ camouflage – and could increase survival (logical speculation from Dr. Brodman). Second, the organic matter increases the density of vegetation, which may help amphibians better thermoregulate and conserve moisture under the shade of those plants. Those plants probably provide more and better hiding places too…
At our Platte River Prairies, we’ve experimented with trying to supplement organic matter levels in our restored wetlands by “top-dressing” excavated wetland bottoms (spreading top soil on them). While it likely increases organic matter, the main impact we’ve seen so far is an increase in invasive plants – and/or lower plant diversity. It may be that waiting for those wetlands to accumulate organic matter slowly will allow a more diverse plant community to take hold – but may mean lower breeding success for amphibians and other species in the meantime.
A final discussion topic during our wetland field trips centered on habitat structure for shorebirds – as well as amphibians and other species – as restored wetlands mature over time. Obviously, the bare sand (or sparse vegetation) conditions immediately after wetland construction provide great habitat for shorebirds. As that plant community develops over time, a few dominant plant species often end up covering much of the area, reducing bare ground, decreasing plant diversity and somewhat simplifying habitat structure. We had an interesting set up discussions about whether (or how often) it was valuable to periodically “reset” those early conditions through intensive disturbances such as grazing or disking – and there was no consensus among the group.
We’ve experimented with periodic intensive grazing at our Platte River sites to create bare ground in and around the deeper portions of our restored wetlands. Within a year or two after the cattle have moved to another location, those wetland plant communities recover their former plant composition and habitat structure. We’ve found that kind of grazing to be useful in preventing species like cattails from choking out open water habitat – and in creating temporary habitat for shorebirds and other species that like bare ground. On the other hand, there are certainly impacts from the cattle in terms of nutrient inputs and sedimentation. I don’t have the answers about how to balance those tradeoffs. At this point, we’re banking on the ability of our sites to absorb the potential negative impacts – on a short term periodic basis – and we appreciate the apparent benefits.
It was great to have the opportunity to see what the Conservancy’s 6,000 acres of restored grassland/wetland habitat is doing for reptiles and amphibians in Indiana last week. As I’ve mentioned before, I find it valuable to think about my own restoration work through the eyes of various animal and plant species. I admit that toads aren’t one of the species I consider very frequently, so it was helpful to be reminded of the importance of those species and the types of conditions they require. As I walk our sites this week, I’ll be looking at our wetlands with a different perspective than I would have last week.
Ahhhh…a subject near and dear to my heart – herpetology. It’s interesting that Bob is finding hybrids between Fowler’s and American Toads. We have a bit of a hybrid zone here as well – up in Washington County – where Woodhouse’s Toads and American Toads are likely sharing a gene pool. Nice post. On behalf of my warty and wet amphibious friends, thanks. :)
Glad you liked it, Dan. Two herp posts in a row, actually – if you count the invading snapper… I need to pay more attention to toads here to see if we have many Americans. I mostly see/hear Woodhouse, I think.
As a long-time TNC member and early volunteer at Kankakee Sands, I can confirm that this is a wonderful site. I’m glad it came up for sale and was purchased by TNC in the late 1990’s. I don’t believe today’s TNC would buy it.
I’m sure Chris doesn’t want to touch this with a 10-foot pole. I certainly hope you’re wrong, but …
I can’t speak for TNC Indiana, but here in Nebraska, we’d certainly look at big opportunities like that to restore prairie/wetland landscapes and try to take full advantage of them.
The Nature Conservancy’s Indiana chapter has many wonderful people whom I care about and whose professional accomplishments I greatly admire. However, the chapter recently let several people go in a staffing reduction, and it has also cut back on acquisitions.
On the national level, you don’t need to read between the lines in TNC’s publications to see that the organization’s leadership lacks enthusiam for acquiring nature preserves in the way that it once did.
Many state governmental conservation programs are under budget pressure, and now we also have a frontal assault on the nation’s conservation laws and funding sources by some members of Congress.
Overall, the next few years don’t appear very favorable for the preservation of Nature!
We can be very grateful, however, for the terrific work that’s being done by Chris and many others of you in the field every day. Thank you!!
I apologize for leading this discussion away from the main topic.
Long live the herps!
I have really been enjoying your “blogs” and forward them on to my ecologist friends….thanks!
Proximity to established populations is important. I built a rain garden pond in autumn 2010, in my back yard (at the house I bought a year earlier). This fall, 6 different species of anurans (froggy critters) sang there — spring peeper, western chorus frog, southern leopard frog, American toad, gray tree frog, Blanchard’s cricket frog. My next door neighbor has a thirty year old pond that is a breeding site for all of these, so this rainy spring made it easy for them to expand their local breeding range. There are of course parallels in the restoration biz.
Go Chris. Fantastic blog site.
Can you expand on your use of cattle in setting back cattails? How much grazing pressure is necessary, how long does the effect last, etc. Thank you very much
Jeff – Our experience has been that if the cattle stomp down and graze the cattails for a good part of a season they’ll get rid of a good number of them (mostly by stomping them into the mud, I think). That seems to buy us a couple seasons. If we only have cattails in a few deep pools, the cattle tend to pick those same spots to congregate on hot days. When there are bigger areas, it may be necessary to fence the cattle into the areas you want them to impact to make sure they spread the impact out across the whole site. In the rainwater basins of Nebraska, agencies fence large herds of cattle into wetlands to really impact those sites and convert them from cattails, canarygrass, river bulrush to annual plants. I’m not advocating that kind of large scale intensive grazing if the goal is a diverse plant community, but I’m not sure it would be that bad either – wetland vegetation seems to be pretty tough. I think you’d want to experiment at a small scale at your own site and see how it looks.
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