Little Calumet River Prairie and Wetlands: A Comparison in Restoration Management
By: Blaire Byg, Leah Garner, Lily Gordon, Colin Parts, Roberta Weiner
In recent times, environmental stewardship and land management practices have grown significantly in popularity and in sophistication of techniques. As popularity and techniques have grown, so have the opportunities to gather data from these restoration sites. Groups such as the Northwest Indiana Restoration Monitoring Inventory (NIRMI) have begun to compile data on various restoration projects throughout the country. Most of the sites within the specific focus of NIRMI are in the Calumet region, which borders Lake Michigan on the South, stretching across the Northern end of Indiana toward Michigan.
One of the sites that NIRMI monitors, the Little Calumet River Prairie and Wetlands is of special interest to our group because of the nature of the stewardship that the site receives. Dr. Spencer Cortwright, a professor at the Indiana University Northwest, is in charge of restoration at this specific site. However, since the city of Gary owns part of the property, Dr. Cortwright is only able to manage two of the six plots that are currently under measurement by the NIRMI team. Due to the fact that these stewardship practices have only been applied to two of the six monitored plots, our group thought it would be ideal for measuring the effects of stewardship on a wetland habitat.
Though some research has been done on certain aspects of environmental restoration in the context of effects on the ecology of a habitat, the studies have largely had the effect of informing how restoration should be carried out. The results of a study on the effects of land management on soil quality indicate that land management can have extreme impacts on soil quality, and the least disruptive land management techniques result in the greatest soil quality as calculated by the soil quality index (Welch np). Additionally, a study comparing the species existent in restored wetland prairies to natural wetland prairies shows that while restoration can help to increase the species diversity of a wetland prairie, the seed bank will not have the same level of diversity as that of a natural wetland prairie (Galatowitsch 102). These studies roughly outline the manner in which it seems environmental restoration should be carried out, using non-disruptive techniques and ensuring the spread of native seeds in the restoration area. However, these studies do not indicate the effects that restoration can have on environmental quality as measured through the metrics we used.
The purpose of our study was to determine how substantial the effects of stewardship and restoration practices within a degraded environment are on biodiversity and the reduction of invasive species. The fact that the Little Calumet Wetland and Prairie location had NIRMI data for both actively managed and unmanaged plots provides us with a control for environment type, allowing for more accurate results. We hypothesized that the plots where the land was actively managed would show better overall ecological quality (as measured by the Floristic Quality Index and the coefficient of conservatism) than the plots where the land was not managed because land managers strive to increase biodiversity and environmental health.
Little Calumet River Prairie and Wetlands is a 10 acre site “stretching from Indiana University Northwest north to 80/94 and west to the Gleason Golf Course (“Little Calumet River Prairie & Wetlands”). It is located on the Little Calumet River, hence it’s name. Little Calumet River Prairie and Wetlands is comprised of 3 ecosystems: prairie, wetland, and woodlands. Restoration monitoring at the Little Calumet River Prairie and Wetlands has been ongoing since 2010 on six plots within the site. The portion managed by Dr. Spencer Cortwright (plots 1 and 2) is regularly burned, planted, seeded, weeded, and sprayed, whereas the portion owned by the City of Gary (plots 3-6) experiences no active management. By following different plots within the 10 acres of the Little Calumet River Prairie and Wetlands site over the same time period, habitat type and time scale could be controlled for. Due to the distinct management practices and available controls, the Little Calumet River Prairie and Wetlands serves as the ideal site for determining the effect of such management practices.
To quantify the effect of land management on restoration efforts, we used the data and metrics provided by NIRMI. These metrics include species richness, average coefficient of conservation (average C-value), Floristic Quality Index (FQI), alpha diversity, beta diversity, and the Jaccard coefficient. Each of these metrics offer different information about the quality of the site. The species richness conveys the count, distribution, and cover of native, non-native, and invasive species dynamics. The average C-value is an average of each species’ coefficient of conservatism, which represents the affinity of a species for a habitat quality level. For instance, a common species like box elder (Acer negunda) that tolerates variation in habitat quality has a low value (close to 0). Species, like that are able to survive only in a narrow range of conditions found in high quality sites (like the Kalm’s St John’s Wort, Hypericum kalmianum) have high C-values. An extension of this is the FQI, which expresses the quality of a site. FQI is related to the coefficient of conservatism in that it takes into account how many high-quality species are in the area, but it also measures the coverage percentages of all of the species in the site. Alpha diversity measures the total diversity of a site, while beta diversity measures the change in diversity. Lastly, the Jaccard coefficient quantifies the similarity between sites.
Using the NIRMI database and metrics, we graphically illustrated the annual change in species count, FQI, and average C-value (Figure 4). The cumulative values for each metric were averaged for both the managed plots and the unmanaged plots (Figure 5). Pairwise plot comparisons were made in the following way: plot 1:2, 1:3,4,5,6, and 2:3,4,5,6 throughout all four years of NIRMI monitoring (2010-2013). Comparisons between treatments allowed for evaluation of the habitat quality of actively managed versus unmanaged plots.
Figure 1: Site Map
With this project we examined plots within a wetland restoration site with the goal of comparing biodiversity, native species, and invasive species between plots that are actively managed versus those that are not. Generally, we found a clear difference between the plots that are actively managed versus the plots that are not, with the managed plots (plots 1 and 2) containing higher numbers of species, higher C-values, and higher FQI values than the plots that received no management (plots 3 through 6). All of these results support our hypothesis that if land is actively managed, the overall land quality (as measured by FQI and the C-value) for that land will be better than in unmanaged land. By examining plots 1 through 6 for beta diversity, which measures the differentiation between habitats, and by calculating the Jaccard coefficient between plots, which measures similarity, differences between the managed and unmanaged plots became evident. In short, this data provides evidence that the two managed sites are more similar in plant species and diversity than they are with the unmanaged sites, establishing a difference between the two sets of plots with different levels of management.
The differences that our comparisons highlight between the managed and unmanaged plots within the Little Calumet River Prairie and Wetlands show that it can be problematic to take the average C-value of the entire site, without doing a more fine-grained analysis. The degraded plots within a site can significantly lower the overall value for a site, obscuring the restoration progress that has been made on well-managed plots within the site. While this is not a factor in our own analysis because we found the C-value for each individual plot, a similar problem can also occur with taking an average C-value across time, something that we did do in our comparisons and that should be considered when interpreting our results. The average C-value changed from 2010 to 2013 for plots 1 and 2 as restoration proceeded. This shows that the C-value was not static across time, causing the average C-value across time to differ from the current C-value. However, because we were using average C-values for the unmanaged plots, we used average C-values for managed plots in order to make our comparisons consistent.
Our data, while it does indicate a difference in ecological quality between managed and unmanaged land, only compares plots within one site. This is in order to control for confounding factors that might be associated with comparing multiple sites. However, it is useful to understand the metrics for other wetland habitats in the Calumet region in order to have a reference for average C-values and FQI values for wetland habitats in the region. Therefore, we also looked at the C-values and FQI for four other wetlands in the region: the ExxonMobil Hammond Terminal, the Marquette Pannes, Samuelson Fen, and INDU Great Marsh.
|INDU Great Marsh||5.432||36.031|
The data above shows that the Little Calumet has a lower average C-value than all of the other wetlands in the region. Even the actively-managed plots of the Little Calumet have lower average C-values than the other sites. This indicates that the Little Calumet site has fewer species that are considered unique and high quality to the habitat than the other wetland sites in the area. This difference could be attributed to a variety of factors such as: restoration in Little Calumet has not gone on for as long as it has in these other wetlands, the land managers in these different sites use different management practices, or the particular locations of all the wetland sites and the composition of their bordering habitats.
While the C-value for the Little Calumet Wetlands was lower than the other wetland sites, the FQI was about average. The FQI for the entire Little Calumet site was very similar to Marquette Pannes and Samuelson Fen and higher than ExxonMobil and INDU Great Marsh. This means that the Little Calumet site is of similar floristic quality to several of the other wetland habitats in the region, despite its lower average C-value. While we did not look at the invasive species coverage in all of the wetland sites, higher invasive species coverage in the other wetland sites compared to Little Calumet might account for the discrepancy between C-value and FQI.
In regards to native versus invasive species in the Little Calumet site, plots 1 and 2 contain more native species than any of the other plots, supporting the hypothesis that active restoration increases native plant species cover. However, the total number of invasive species in those two plots is also larger than any of the other plots. Some reasons for this could be that the locations of plots 1 and 2 border areas with more invasive plants, or that the higher number of native species in the plots increase the health of the soil and, therefore, attracts more invasives because more species can exist within a healthier plot. In addition to the existence of more invasive species in the managed plots versus the unmanaged plots, there were also a few invasive species that were found exclusively in the managed plots. An example is Trifolium repens, or white clover, a small herbaceous plant with heads of white flowers, native to Europe, North Africa, and West Asia. However, it should also be noted that there was one invasive plant found in the unmanaged but not the managed plots. This plant is Morus alba, or white mulberry, a 10 to 20 meter tall tree that is native to China. This difference might exist because the restoration efforts in plots 1 and 2 focus on getting rid of larger invasive plants and therefore involve cutting down large trees, rather than eliminating all small invasives, or it could exist because of the particular composition of the habitats bordering each of the plots.
Looking to the future, our analysis suggests that active management of restoration sites can aid in re-establishing a strong presence of native plants. In order to create healthier land that promotes rich biodiversity, we suggest that land be actively managed. One thing we did not compare is the type of management and its effect on the restoration trajectory. If specific management techniques were known for each site, the NIRMI data from sites of the same habitat could be used to evaluate this further. One could also perform an indicator species analysis in order to determine the health of the plots by examining which species are indicative of healthy plots of land and whether or not they are present in each plot. Another analysis that could be helpful in expanding the knowledge about the restoration of wetlands in the Calumet region would involve the analysis of the data from more wetland sites in order to better understand the health of the wetlands of the Calumet region more broadly.
Figure 1 courtesy of Pete Avis of NIRMI
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