This Just In: Latest Chicago Wilderness "100 Sites" map

The ‘100 Sites’ project draws together multiple natural areas across the region into a replicated natural experiment.  The sites are matched by habitat type (woodland, prairies) and restoration intensity.  

We are doing this  in order to address two main questions:
How effective are current management practices for restoring and conserving biodiversity?  
How effective are current management practices for rehabilitating key ecosystem processes?  

The image above shows the 121 sites that are currently in the system.

The project is managed by Lauren Umek; the PIs are Liam Heneghan and David Wise.  We are collaborating with many managers throughout the region.

This project is funded by the The Gaylord and Dorothy Donnelley Foundation, 

Reflections on Experimental Soil Manipulations to Reduce European Buckthorn Invasion, (with observations on soil lead mobilization)

What follows are some reflections on the results of our MOLA restoration experiment.  Please note that I post these to provoke conversation and get your thoughts on soils and restoration.  The reflections are very preliminary and have not been peer-reviewed.  For ease of read (or quick skim) I have not included literature references or a bibliography.  In the coming weeks we will be sending a manuscript in for publication on the topic.  Lauren Umek is the project manager and is a senior scientist on the project. 

For more background on the project see here and here.

The analysis of soil nitrogen availability is a focus of many studies examining the efficacy of incorporating material of low carbon quality (e.g. wood mulch) into soils as a potential restoration tool.  This is because these treatments are hypothesized to reduce nitrogen, elevated in soil as a consequence of anthropogenic atmospheric input or as a legacy of fertilizer use in agricultural land.  Nitrogen elevation is known to be a factor in some invasions and in a concomitant loss of native species.  Defertilization (N reduction) in circumstances where land is managed for the protection of biodiversity may lead to a reduction in invasion and an increased prevalence of species of conservation significance.  Our treatments were designed to reduce the availability of soil nutrients, especially nitrogen, and thereby modify the structure of the plant community in revegetating plots in this manipulative field experiment.  We anticipated that the soil environment modified in this way would support a lower density of Rhamnus cathartica (hereafter “buckthorn”) a dominant shrubby invaded of Midwestern Woodlands. 

We found that for some of the nutrients measured in our study, including nitrogen, availability was indeed reduced.  However, these effects were not consistent over the two years that we measured them with the important exception of phosphorus availability which increased in plots that had received a mulching treatment.  Consistent with our expectations buckthorn seedlings and saplings density was significant reduced in all plots compared with our controls (where buckthorn was not cut).  Additionally, those plots that had received wood mulch, either of buckthorn or commercial mulch, had lower buckthorn seedling or sapling density than all other treatments.

SEKsy Restoration: A Design for a Restoration Experiment employing Soil Ecological Knowledge to reduce Re-invasion by European Buckthorn

This work was undertaken with Lauren Umek who is the project manager and with the assistance of Tom Murphy from DePaul and a crew of dozens.

This recent restoration experiment directly addresses the hypothesis that successful prevention of the re-invasion of species like European buckthorn, Rhamnus cathartica, will be promoted by reducing soil nitrogen (N) levels.  High N in soils may be a legacy of long-term invasion by buckthorn, and other invaders, which have high N levels in their leaf litter.  As a consequence of reducing N as we attempt to do in this experiment, and perhaps this is counter-intuitive, the success of native plant diversity may be increased since the native community does not then have to complete with an aggressive invasive species.

In this experiment we chose those strategies for manipulating N availability in the upper soil horizons that managers might be expected to adopt if our experiment demonstrates desirable outcomes. These management techniques included mulching with buckthorn woodchips or with commercial mulch, a two-year corn-harvesting regime, and mowing and removal of a cover crop. Both of these strategies are expected to  reduce N levels in the soil and therefore reduce reinvasion rates.

Sneak Peek at 100 Sites Map

 

This cool map is from the 100 sites project (100 1 hectare research sites in the Chicago Wilderness region where researchers and ecological managers are collaborating on long term evaluation of restoration activities).  David Wise from University of Illinois Chicago, and I are PIs on this Gaylord and Dorothy Donnelley Foundation funded project.  Lauren Umek is project manager and has overseen the work on all of the sites. The map was prepared by Alex Ulp.

Graph-Post 1: Soil phosphorus after removal of invasive shrub (Rhamnus cathartica)

 

 

This graph shows the soil phosphorus levels during the first year after an invasive shrub, European or Common buckthorn (Rhamnus cathartica), was cut and removed from our experimental site (controls are uncut buckthorn).  Each bar represents 5 separate plots per treatment.

In this experiment, conducted in collaboration with Lauren Umek and other colleagues at DePaul university, we removed the invasive species and then implemented a variety of treatments:

Best Management Practice (BMP 1) is to cut and then seed with natives;  

BMP + cc, is cutting of invasive follower by planting of a cover-crop of grasses;  

Corn is removal followed by growing a rotation of corn; 

The commercial mulch treatment is incorporated into the soil and native seed is planted; 

A mulch is prepared out of the wood from Rhamnus and incorporated into soul for the final two treatments (with cover crop, or with native seed).

The idea that we are playing with here is that a manipulation of the soil - wood mulches are especially important in this regard - reduces that availability of key soil nutrients, nitrogen in particular, which in turn reduce the rates of reinvasion by invasive species, and create an environment favorable to species of conservation interest.  Mulches may reduce availability of some nutrients because the microbes that decompose the wood "mop up" any extra nutrients making them less available to plants.

The results of an analysis of soil nutrients (sampled with a probe buried for approximately a month in Spring of 2008) revealed that mulched treatments generally had more phosphorus available in the soil.  The uncut control plots had the least phosphorus.  Contrary to our expectation nitrogen is not altered by any of our treatments.

I'll show, in later graph-posts whether this corresponds to changes in the vegetation (spoiler - there are interesting patterns in the reinvasion of the plots after invasive species removal and treatment).