Tag Archives: prairie reconstruction

Grassland Birds in Prairie Restorations: Response to a Research Paper

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A “Restoration Note” published in the most recent issue of the journal Ecological Restoration (March/June 2011) caught my attention last week.  I was initially interested because some of our sites had been part of the study but I hadn’t seen or heard about any of the results.  However, after reading the note (a short research article) I found myself musing yet again about the kinds of expectations people have for prairie restorations.  In this case, the authors were comparing bird communities in restored prairie to those in relatively degraded remnants with the idea that identical bird communities would equate to a measure of success for the restored prairies – something I strongly disagree with.  I apologize for not being able to provide you with anything more than the citation below and some paraphrasing of the article.  I requested permission from Ecological Restoration to post a PDF of the Restoration Note itself, but was turned down, and there is no abstract because of the short length of the article itself.  I guess if you want to read the whole article and don’t have a subscription to the journal, you’ll have to either go to a library to find it or pay their fee ($17!!) to read it online.

Nevertheless, here’s the citation for the article:

Ramírez-Yáñez, L. E., Chávez-Ramírez, F., Kim, D., Heredia-Pineda, F.  2011.  Grassland Bird Nesting on Restored and Remnant Prairies in South Central Nebraska.  Ecological Restoration 29:1-2, pgs 8-10.

In the study, the authors measured grassland bird abundance and vegetation structure/composition in six restored prairies (former cropland) and six remnant prairies (relatively degraded) along the Central Platte River valley in Nebraska.  The restored prairies ranged from 5-15 years in age, but the authors didn’t specify how many were in the younger vs. older stages.  Of the restored prairies on our property that I think were used in the study, two were seeded in 2002 and the other in 2001 (the paper isn’t clear about how many years of data were used for the analysis, or what years they were).  The researchers looked mostly at three bird species (bobolinks, grasshopper sparrows, and dickcissels) and located nests for each.

Grasshopper sparrows are nearly ubiquitous - often in high densities - in grazed pastures along the Platte River in Nebraska

From their vegetation data collection, the researchers found that the plant species richness of the remnant and restored prairies was very similar.  However, remnant prairies had more cover of low-growing grass species such as Scribner’s panicum and tall and sand dropseeds.  Restored prairies had more tall forbs such as sunflowers and goldenrods.  The average height of the vegetation was quite a bit taller in the restored prairies than the remnant prairies (average of 96 cm in restorations and 59cm in remnants).

The researchers found 242 grassland bird nests in remnant prairies and 264 in restored prairies.  There were significant differences between restored and remnant prairies in the abundance of nests of the three species they focused on.  Bobolinks and grasshopper sparrows had more than twice as many nests in remnant prairies than in restored prairies.  Dickcissels, on the other hand, had three times as many nests in restored sites as in remnants.

DIckcissels prefer tall forby vegetation structure like that found in young restored prairies.

Based on the vegetation data collected, the results of the bird data fits well with what would generally be expected – and what I observe in our sites.  Dickcissels tend to like sites with taller vegetation, especially when abundant tall forbs are present.  In contrast, grasshopper sparrows and bobolinks are most abundant in pastures and hayed prairies, respectively, where vegetation is kept short, and regular cropping of grasses favors those species with shorter stature.  Up to this point, as I read the paper, everything the authors were reporting fit with what I see for bird use in our Platte River prairies.  What threw me for a loop was the final paragraph of the article, in which the authors presented their interpretation of their data and the conclusions they had drawn from it.  The following is that last paragraph:

“Our preliminary data suggest that these restorations, at this point in time, are not creating the nesting habitat required or preferred by birds in more natural grasslands.  Most restoration practices focus on vegetation reestablishment and cover (Martin et al. 2005), which represent the restoration of primary production but do not ensure the recuperation of essential habitat components needed by native fauna (Whisenant 2005). Our preliminary results have promoted a change in our philosophy to include wildlife habitat requirements at the planning stage of restorations.”

There are three points I’d like to make about that paragraph and the conclusions drawn by the authors of the paper.  The first is something I’ve dealt with in a previous post.  The authors are assuming that the point of prairie restoration is to replicate existing prairies – at least, in this case, in terms of the vegetation structure and relative composition of the plant and bird communities.  Even in cases where remnant prairies are very high quality, I feel strongly that trying to replicate them through prairie restoration is not only unwise, it’s a strategy that is doomed to fail.  The management history, soil conditions, and many other factors are very different in a remnant prairie than they will be in a restored prairie.  Moreover, along the Platte River, the remnant prairies are almost all degraded – many significantly so – by overgrazing, repetitive haying, and/or broadcast herbicide application.  As a result most are missing many important prairie plant species and are largely dominated by grasses (including invasive grasses such as smooth brome and Kentucky bluegrass).  I think that most botanists would cringe at the idea of trying to replicate those prairie plant communities because of their degraded state.  Our restoration work, in fact, has focused not on replicating remnant prairies, but on enlarging and re-connecting them to each other by restoring cropland in between them with restored prairies planted with seed mixtures that maximize the diversity of locally-native plant species.  Those seedings, as they mature, are managed to maintain their biological diversity (including birds) – not to make them resemble the remnant native prairies adjacent to them.  In fact, we consider it to be a measure of success that the restored prairies contain many plant species no longer found in most nearby remnants.

The second point relates to the first, but deals specifically with the bird communities in the restored and remnant prairies.  Grasshopper sparrows and bobolinks are among the most abundant bird species in the landscape surrounding our restored prairies, and dickcissels (and other species that prefer tall forby vegetation structure) are relatively rare.  To me, creating restored prairies that complement the bird communities in the surrounding landscapes by providing habitat for dickcissels seems like a savvy conservation strategy.  If restored prairies favored the same bird species as the remnants, very little would be gained in the landscape since the amount of restored prairie is very small compared to the amount of remnant prairie.  We would simply be adding a few more grasshopper sparrows and bobolinks to the landscape – and we’d still be low on dickcissels.

Bobolinks are frequently found in hayed prairies along the central Platte River, as well as in light-moderately grazed prairies. (This one is sitting in a restored prairie)

The third point is that the authors are comparing grasslands (restorations to remnants) that differ significantly in both current and historical management.  The remnant prairies have long histories of either season-long intensive grazing and/or annual haying that has strongly influenced their plant species compositions.  Even though the remnants in the study are now primarily managed with fire and grazing, the plant community composition in those prairies is much more a product of historic than recent management.  In contrast to the remnant prairies, most of the restored prairies in the study have had mostly periodic dormant-season fire management that has encouraged dominance by the tall grasses and forbs that make up a large part of their plant community.  Plant species (such as panic grasses, dropseeds, and exotic cool-season grasses) that thrive in repetitively grazed or hayed prairies are not dominant.  Some of the restored prairies in the study are sufficiently established that they are now being grazed somewhat similarly to the remnant prairies – though generally at lighter stocking rates – but that management has not been going on long enough to greatly influence plant species composition.  It is no surprise, therefore, that the species composition and vegetation structure of the remnant and restored prairies are different from each other.  That difference reflects not a failure of the restoration process, but is rather a product of the difference in the length and type of management the sites have received.

To build a little further on the last point, IF the goal of the prairie restoration process along the Platte was to create prairies with plant species composition and vegetation structure similar to that of remnants, success would depend much more on management strategy than restoration planning and design.  Yes, alterations in the initial seed mixture to favor panic grasses, dropseeds (and invasives?) could give those species a greater relative abundance more quickly during the establishment of the restored prairie.  However, management is going to drive that establishment process much more than seeding design.  With periodic dormant-season fire, those species will not thrive, and warm-season native grasses and large forbs will still dominate – even if they start with lower abundances.  In contrast, relatively frequent and intensive grazing (or annual haying) would push the plant community toward high abundances of those lower-growing grasses (and probably fewer late-season tall forbs).  If you started with two young restored prairies – one with lots of low-growing grasses and few tall grasses and forbs, and one with the opposite composition – those plant communities could be pushed in opposite directions through management until each became nearly identical to the other.  In other words, if the authors of this paper want to favor grasshopper sparrows and bobolinks in future prairie restoration efforts, they could alter their restoration design to increase the abundance of low-growing grasses, etc., but they would be much better served spending their time on plans for an appropriate management regime instead.

To be clear, I don’t question or disagree with the data collected by the researchers on this project, I simply disagree with the conclusions and implications they drew from their results.  First, I’m not sure why they are disappointed to see an abundance of dickcissels in restored prairie, given their relative scarcity in the surrounding landscape.  More importantly, I have a much different set of objectives for restored prairies than they do.  Mine are related to contributions of restored prairie to landscape function and population/species viability, rather than to an attempt to replicate existing remnant prairies.

However, this kind of discussion over what prairie restoration should aim to accomplish (and what it CAN accomplish) is very productive.  The publication of articles that evaluate restored prairies – even those with a different perspective than mine! – is extremely valuable, and stimulates conversations that should move us significantly forward in our attempt to conserve and restore grassland ecosystems.  I would appreciate hearing from you about your perspectives on this and other similar topics.

An Early Attempt to Evaluate Prairie Restoration Success by Looking at Insect Use.

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Back in February, I wrote a post that laid out some ideas about how to measure success when using prairie restoration (reconstruction) to stitch fragmented remnant prairies back together.  One of the main needs is to see whether species from the remnant are also using the restored prairie.  If I’m trying to make a small remnant prairie function as a larger prairie by adding restored prairie around it, the species in the remnant must be able to expand into and travel through the restored habitat.

I just got some data from a couple of volunteer amateur entomologists that apply to that kind of evaluation, so I thought I’d share what they found.  First, let me be clear that these are amateurs (“enthusiasts” may be a better term than “entomologists” – though they are much better at insect identification than I am!) and that these are not research data.  However, what they found was very interesting, and will make a good launching point for future work.

Four species of tiger beetles were among the insects found during the 2009 inventory work.

INTRODUCTION

In early 2009, I was approached by Chris Aubushon and Connie McCartney, who live in Grand Island, Nebraska – near our Platte River prairies.  Chris and Connie were initially just looking for new sites to hunt for insects, but as we talked, we developed a bigger idea.  They volunteered to come out once a month for during the 2009 growing season and collect as many insects as they could from 6 sites and to identify what they could.  The six sites were really three sites where I had a restored prairie next to a remnant prairie, and they collected insects from both the remnant and restored portions of those sites.

Chris Aubushon (left) and Connie McCartney (right) setting up plots for their insect inventory project in early spring 2009.

Again, this was not a research project, but Chris and Connie – and some helpers – did come out once a month for 5 months and collect a lot of insects.   They restricted their sampling to one 100 foot by 100 foot plot at each of the 6 sites, and used a combination of sweep netting and pitfall traps to catch the insects.

RESULTS

Chris and Connie were able to identify 136 species from those five months of collecting.  They also found (but didn’t identify to species) approximately 33 species of spiders.  When I got the list of species from Chris, I sent it to several friends of mine who are knowledgeable about insects to get their impressions.  The consensus among those entomologists was that the insects on the list were almost exclusively common species that are habitat generalists.  In other words, the list doesn’t include many rare species, or species tied to particularly “good” quality prairies.  Instead, Chris and Connie mostly caught insect species that can be found just about anywhere.   That doesn’t diminish their efforts, but it’s important to remember as you interpret the breakdown of results.

Of the 136 species caught, 28 were seen at only one site.  Interestingly, 8 of those 28 species were found only in remnant prairie, while 20 were found only in restored prairie.  (I don’t think it is necessarily important, but of the 20 species found only in restored habitat, half were beetles.)  Two species – a firefly and a burying beetle were found at two different sites that were not adjacent to each other.  In each case, they were found in one restored prairie plot and one remnant prairie plot.

The reference insect collection from Chris and Connie's work in 2009.

All of the remaining species (106 of them) were found in both halves of at least one remnant/restored prairie pair.  In other words, except for the two species mentioned above, every other species of insect found in more than one place was seen in both the restored and remnant portion of at least one prairie.  Remembering that these are all generalist species, I’m still surprised – and encouraged – by those results.  I had expected to see at least a few insect speces that were found in remnant prairies but that weren’t yet making the jump into the adjacent restored prairies.  In fact, I was kind of counting on seeing that so that I could design some follow-up data collection to figure out what the obstacles might be that were preventing them from using restored prairie.

CONCLUSIONS

So what have I learned?  First, the prairie restoration work we’ve been doing appears to provide adequate habitat for the most common and widespread insect species in our remnant prairies.  At least for those species, the restoration work we’re doing is successfully increasing the size and connectivity of fragmented remnant prairies.

Second, I’ve learned that I need to recruit a lot more entomologists to come collect insects from our prairies because every time I do, I learn something.  A little more than a decade ago, I worked with Kristine Nemec on her graduate school project to compare insects between remnant and restored prairies along the Platte River in Nebraska.  For her project, she inventoried insects in 3 restored and 3 remnant (degraded) prairies, but the restorations and remnants weren’t adjacent to each other.  Nevertheless, among grasshoppers, katydids, leafhoppers, planthoppers, and treehoppers, she found very few species that were found in remnant prairies but not restored prairies.  She also found very similar numbers of species between remnant and restored prairie for each of the insect groups she looked at.  You can see a brief summary of some of her thesis findings here. Nemec Results

Third, I’ve learned that the next steps in our efforts to evaluate insect use of our restored prairies will be harder.  We probably need to start by identifying species of insects in our remnant prairies that may not utilize nearby restored prairie – based on what we (meaning people besides me) know about their life history.  Then we need to do some targeted sampling to see whether they are or are not using those restored prairies.  It’d be even better if we could actually track individual insect movement to see if they cross the boundary between remnant and restored prairie.   (That should be easy, right?)  Broad sampling like we’ve done so far is useful, and a good first step, but now we need to hone in on a few target species and see what we can learn about them.  Species that rely on a particular plant species or that are tied to soil organic matter levels may be examples of those we need to study.

To sum up, there’s plenty of work to do.  To this point, we haven’t found any glaring problems with our restored prairies that are so severe that common insect species are restricted from using them.  That’s pretty nice to know, but it’s just the tip of the research iceberg.  Now we need to dive in and start working on the rest.

I’m extremely grateful to Chris Aubushon and Connie McCartney for all of their hard work collecting, sorting, and identifying insects for this project.  It was an amazing effort – and done for the simple love of exploration of the natural world.  Thank you.

I’m also grateful to James Trager, M.J. Hatfield, and Ted MacRae for helping me to interpret the results of the project.  Their comments and insight helped me tremendously as I worked to understand what conclusions I could and couldn’t pull from these data.