One of the primary components of the Irvine Prairie mission is the restoration and maintenance of an ecologically diverse tallgrass prairie. We began this work in 2018, seeding ~ 9 ac on the hilltop nearest the farm in May. In order to ensure that our efforts at restoring a diverse prairie are effective, we must reliably monitor our progress through detailed vegetation sampling. Monitoring also allows us to anticipate potential problems in the future, and helps us tweak our management practices in order to get the best results we can get out of the seeds and plants we’ve planted. This document serves as a “check-up” to see how the restoration is doing, and how well we are meeting our goals. In this update we 1) review how we conducted our monitoring (Methods), 2) show what the monitoring tells us (Results), and 3) discuss steps we should take based on our results (Management Implications).
Our approach to monitoring is to use randomized, permanent plots to answer our questions about the performance and ecology of Irvine Prairie. We established the first set of monitoring points in 2018. Each permanent plot consists of two steel pipes recessed into the ground at the corners of a ~ 10 ft2 square area, with approximately 2 in of exposed pipe. A custom constructed sampling frame with downward facing pipefittings can be placed on the permanently established pipes to form a repeatable sampling area. These permanent steel “corner posts” are designed to withstand both fire and mowing (> 4 in), and similar permanent marker designs have been used successfully under comparable circumstances (Meissen et al. 2017).
We measured species identity, vegetation density and canopy cover metrics at each sampling location. To measure canopy cover, we identified all species present and estimated the area covering the ~10 ft2 quadrat by each species (including bare ground) using Daubenmire cover classes. We then used the class midpoints to estimate canopy cover by species and combined species data to estimate canopy cover by functional group. We used this data (species presence in ~10ft2) to estimate species richness. We measured density data using a smaller ~1ft2 quadrat nested in the southwest corner of the larger ~10 ft2 quadrat. Here we measured each plant and number of stems for all species present in the quadrat.
We catalogued all species present in the 2018 planting using a meandering walk. During the walk, we recorded all planted species encountered, and estimated their overall abundance using a qualitative scale: Very Rare, Rare, Uncommon, Infrequent, Frequent, Common, Very Common.
Overall, restoration outcomes met or exceeded expectations in 2018. It appears seeding was executed without significant issues, and both native species and cover crops established well (Fig. 1, Fig. 2). Weed issues were nearly non-existent across most of the site, with the exception of crabgrass matting in the areas nearest the parking area. This mat prevented all native establishment. The area that used to be a waterway in the northwest had issues in establishment, apparently due to water moving seeds off-site.
Establishment of the planted seed mix was very good in 2018 (Fig. 3). Compared to other benchmark seed mixes, this seed mix performed about as well or better than the Nashua Diversity Mix. Establishment rates exceeded 10%, which is rare in prairie restoration.
Vegetation structure was quite varied throughout the 2018 planting (Fig.4). We found a relatively even mix of native forbs, annual weeds, bare ground and cover crops on site, and a fairly high abundance of native grass. We were encouraged to find little to no perennial weed cover throughout the sample site.
We found over 40 species throughout the planting site (Table 1). This is encouraging given the generally late timing of planting- many forbs are likely to emerge next year as dormancy is broken over the cold months. We expect the list of species present on site to grow substantially in 2019.
Species abundance was highly variable, but we found most at low abundance (1-5% cover) (Fig. 5). Some grass species like composite dropseed, switchgrass, and sideoats grama were particularly common, with cover ranging from 10-20%.
In general, the outcomes from our formal vegetation assessment were good. To continue achieving ecological goals on schedule, we suggest similar implementation and management should continue.
There are two areas that will likely require re-seeding next year: Area 1 with crabgrass matting and Area 2 that experienced some seed washout (Fig. 6). Further monitoring in these areas in 2019 will confirm the necessity of reseeding. If no further native plant establishment occurs by September 2019, re-seeding will commence that fall or the following spring.
The high abundance of switchgrass should be reassessed next year to inform whether warm season grass control measures should be considered for this planting in the future. Unlike many switchgrass cultivars, the Iowa ecotype switchgrass we planted is not typically overly competitive. However, the abundance of switchgrass that established is much higher than expected given the moderate seeding rate. The potential for competitive exclusion of conservative species in this planting due to switchgrass abundance exists, but ultimately is probably low.
Switchgrass seeding densities should be reduced in other Irvine Prairie plantings. We may see different establishment patterns in 2019 due to the differences in site preparation (bean stubble vs disked corn) that may render switchgrass overabundance a non-issue, but we prefer to avoid that risk by lowering the seeding rate.
Meissen, J. C., S. M. Galatowitsch, and M. W. Cornett. 2017. Meeting seed demand for landscape-scale restoration sustainably: the influence of seed harvest intensity and site management. Ecoscience 24:145–155.
Figure 1. Typical view of the planting area, 8/1/18. Oat cover crop fully established.
Figure 2. Typical vegetation detail. Note high nurse crop cover. Several small native seedlings can be seen.
Figure 3. Seedling emergence after one growing season (% planted seeds emerged) compared to benchmark seed mixes.
Figure 4. Canopy cover of functional groups sampled in ten ~10 ft2 quadrats. Cover may exceed 100% due to use of cover classes.
Figure 5. Canopy cover of top 20 species sampled in ten 1m2 quadrats. Cover may exceed 100% due to use of cover classes.
Figure 6. Emergent management areas. Area with yellow hatching show locations with poor initial establishment. Follow up monitoring and likely reseeding should occur in these areas in fall 2019.