For 5 years, the TLC has monitored and managed 51 acres of forest and shrub swamp on the Michigan Road Preserve in Port Huron Township for Saint Clair County and a private developer. The preserve is located along the east side of Michigan Road, north of Dove Road and south of the Canadian National Railway tracks. It is a small remnant of the northern forest and shrub swamp that once covered most of the Port Huron area. This northern forest complex is an expanse of forested lakeplain swamp, periodically interrupted by upland sand ridges deposited thousands of years ago by higher waters of the early Great Lakes. The Michigan Road Preserve was protected by two conservation easements as wetland mitigation for two projects permitted by the Michigan Department of Environmental Quality. The MDEQ requires long-term monitoring and management on all wetland mitigation sites, usually by a third-party steward such as a land conservancy. For more details, refer back to the 2015 March 17 blog article, Michigan Road Preserve Stewardship:
A routine part of monitoring natural areas is collecting vegetation data to record the existing or baseline conditions. All plant species are identified and inventoried to determine the type and quality of natural community present, and to detect changes in the vegetation over time due to natural and human impacts. In Michigan, the usual impacts include the spread of invasive plant species, plant diseases and pests, over-grazing by deer, forest clearing and fragmentation, surface and ground water drainage, off-road vehicle incursions, and refuse dumping, among other things. The vegetation may also change in response to deliberate management actions by the preserve steward intended to improve the natural area, such as weeding, mowing, controlled burning, and herbicide application for invasive weed control and habitat improvement. A preserve may be seeded and planted with certain native species to improve or enhance the plant community or forest stand. Having baseline data allows the land steward to evaluate the effectiveness of their management activities.
|2014 Spring burn in the northwest of the Michigan Road Preserve.|
|Diagram of general forest succession in North America.|
|A typical square sampling plot or quadrat.|
A basic concern in measuring vegetation is whether the sampling areas are large enough to obtain representative samples. Too small, and the sampling area may exclude species that are important and the results will be skewed. A larger sampling area is better, but too large and it wastes time and effort without added benefits to the study. Usually, the idea is not to include every plant species in the sampling area, but enough to show basic trends. Knowing if sampling sizes are adequate is accomplished by producing a species-area curve, a graph of the number of species per sampling size. As the sampling size is increased from zero, the number of new species within the sampling area initially increases. This makes sense. The bigger the sampling area, the more species. The graph is an upward curve as new species are encountered. But this holds true only to a point. Keep increasing the sample size and normally, the number of new species starts to taper off, and likewise, the slope of the graph curve starts to flatten out. No matter how much the sampling area is enlarged, there are only so many new species that can be added. This is assuming that the sampling area does not cross over into a different type of plant community where completely different species occur. An example of this might be a sampling area within a swamp forest where the species are mostly wetland forest species. If the sampling crosses over onto an adjacent upland ridge, there would be several upland species added and the species-area curve would begin to slope up again.
There are two ways to vary sampling size in order to obtain representative samples of the vegetation, although they are essentially the same because they both simply increase or decrease the total sampling area. One way is to increase the size of each sampling plot until the species-area curve flattens out for each plot. For my work in Michigan, I have found that a sampling plot of 3 square meters, or a 1-meter radius circle, has almost always been sufficient to sample herbaceous plants, the mostly non-woody ground layer of vegetation. I use this 1-meter radius plot most often because I am usually sampling in open, non-forested and non-shrubby wetlands constructed as wetland mitigation. These wetlands have been developing from bare ground for only a few years, so trees and shrubs have not established to any great extent yet. Besides individual plot size, the other way to vary the sampling size is to add or subtract the total number of plots. In this case, obtaining a representative sample at each individual plot may not be so much a concern as getting a representative sample of the whole landscape or natural community. If you were to graph the number of species per number of sampling plots, you would find the same species-area relationship described earlier. The slope of the curve rises initially, and then begins to flatten out at the point where fewer species are added with each new sampling plot. I think it could be argued that it’s important to use both a large enough sampling plot to obtain representative samples at each location, and also use enough plots to obtain a representative sample of the whole natural area, but I can imagine some applications where this might not be necessary.
You might be getting the idea by now that basic ecology is mathematics, and you would be correct. This was a little surprising to me in college, but like many things, measurement and data analysis are required to draw certain conclusions. I first got a taste of this mathematical approach to ecology when studying the theory of island, or insular, biogeography in a graduate world biogeography course taught by Dr. Peter Murphy at Michigan State University. I sometimes wondered if Dr. Murphy led the life of a gothic musician at night. But anyway, island biogeography was developed in the 1960’s by ecologists Robert H. MacArthur and Edward O. Wilson to understand and explain species richness on islands and other isolated ecosystems. E. O. Wilson went on to become quite a well-known ecologist and author in later years, specializing in the study of ants. In reading a little about his life, I see that we share the experience of having taught nature at Boy Scout summer camp in our youth. The basis of island biogeography theory is species richness, or total number of species on an island, resulting from species immigration and extinction, which are functions of island size and degree of isolation, among other factors. As you might guess, smaller and more isolated islands, those more distant from other islands and mainland which serve as species sources, have less species. Landscape, habitat diversity, geographic history, length of isolation, ocean currents, chance, and other factors are all influences, but in the purest sense, island size and degree of isolation are primary determinants. So basically, island biogeography is founded on measuring land size and counting species, and then graphing the results. As simple as it is, this theory eventually led to a kind of revolution in conservation. The same ideas of size and isolation can be applied to other situations, such as isolated nature reserves, fragmented forest patches, mountains, isolated bodies of water, and so on. Concern for maintaining species richness in smaller, fragmented natural areas, eventually led to the recognition of the significance of natural corridors to allow species migration between natural areas.
Dr. Brian Palik explains his research activities for the US Forest Service in Minnesota, where they are trying to prepare for the expected invasion of the Emerald Ash Borer as the climate warms. Right now, the pest is largely excluded from northern Minnesota due to extremely cold winters, but the winters are expected to become warmer. They are looking at what happens to the forest community and what tree species will dominate in the absence of Black Ash, and how they might replace Black Ash with some other tree species currently of a more southerly range. West Central Tribune, Willmar, Minnesota, 2015 March 08, Dan Kraker: http://www.wctrib.com/news/state/3695641-warmer-climate-bid-protect-forests
|An example of Density (D), Cover (C), and Frequency (F) measurements of a single species across 5 sampling plots or quadrats.|
Which plant species are more important in the community; the few large or the many small?
|First page of the Michigan Plants Database.|
|Tony Reznicek. University of Michigan Herbarium: http://herbarium.lsa.umich.edu/|
|Wetland in the northwest of the preserve showing extensive tip-up mounds and potential habitat for Michigan Endangered Painted Trillium.|
|Eastern White Pine and Paper Birch in the east-central part of the preserve.|
|A tangle of Speckled Alder, Chokeberry, and Glossy Buckthorn in the shrub swamp portion of the preserve.|
|View north along the west side of the preserve of cleared land along Michigan Road that was forested before 2011. The Michigan Road bridge crossing of the CN Railway in the left background.|
|Increased Glossy Buckthorn growth along the west side of the preserve. Michigan Road in the background.|
TLC Intern Jeff Hansen recording vegetation data on the Michigan Road Preserve in Port Huron Township, Saint Clair County.
|TLC Interns Nicole Barth and Jeff Hansen observing vegetation within sampling plot on the Michigan Road Preserve in Port Huron Township, Saint Clair County.|
- Provide a written evaluation on the success of the long term management plan goals and recommendations.
- Sample vegetation in plots located along transects shown in the plan once between July 15 and August 31 with an approach approved by the MDEQ. Transects should occur along areas targeted in the long-term management plan for enhancement or corrective actions.
- Provide annual photographic documentation of the mitigation area approved for preservation credit from permanent photo stations located within the mitigation wetland. At a minimum photo stations shall be located at both ends of each transect. Photos must be labeled with the location, date photographed, and direction.
- Provide a written summary of data from previous monitoring periods and a discussion of changes or trends based on all monitoring results.
- The mean percent cover of invasive species including, but not limited to, Phragmites australis (Common Reed), Lythrum salicaria (Purple Loosestrife), and Phalaris arundinacea (Reed Canary Grass) shall in combination be limited to no more than ten (10) percent within each wetland type. Invasive species shall not dominate the vegetation in any extensive area of the mitigation wetland.
- If the mean percent cover of invasive species is more than ten (10) percent within any wetland type or if there are extensive areas of the mitigation wetland in which an invasive species is one of the dominant plant species, the permittee shall submit an evaluation of the problem to the MDEQ. If the permittee determines that it is infeasible to reduce the cover of invasive species to meet the above performance standard, the permittee must submit an assessment of the problem, a control plan, and the projected percent cover that can be achieved for review by the MDEQ. Based on this information, the MDEQ may approve an alternative invasive species standard. Any alternative invasive species standard must be approved in writing by the MDEQ.
- Provide a written summary of all problem areas that have been identified in meeting goals and objectives of the management plan and potential corrective measures to address them.
- A monitoring report, which compiles and summarizes all data collected during the monitoring period, shall be submitted annually by the permittee. Monitoring reports shall cover the period of January 1 through December 31 and be submitted to the MDEQ prior to January 31 of the following year. A qualified individual able to identify vegetation to genus and species must conduct the wetland monitoring. The MDEQ reserves the right to reject reports with substandard monitoring data. If the MDEQ determines that the restoration and management goals have not been met, the MDEQ may require subsequent annual monitoring until final approval from the MDEQ can be granted.
|Sampling plots or quadrats, Q-1 through Q-9, on the north side of the preserve.|
Species-area curves were produced for each sampling plot to verify that the size was adequate to obtain representative samples of species occurrence, vegetative cover, and plant density. In all cases, the sampling sizes were sufficient as indicated by the species-area curves for both individual and collective quadrats.
|Species-area curves for shrubs and trees in plots Q-1 through Q-3. Three plots are adequate. The slight rise in species at Q-3 is due to new species encountered in the sampling area on an upland sand ridge, versus the swamp forest in Q-1 and Q-2.|
Based on Cover, Density, and Frequency, Importance values were calculated for plant species in each sampling plot. The following table is a list of the top dominant species, in descending order, on the Michigan Road Preserve, observed from 2011 through 2015.
|Dominant plant species on the north side of the preserve.|
Prevailing Wetland Coefficients
Importance values were combined with Wetland Coefficients for each species inventoried in the sampling plots to determine the Prevailing Wetland Coefficient for each sampling plot. There have been only very slight variations in the values listed in the table below. Prevailing Wetland Coefficients range from a low of -3.6 (Facultative Wetland) to a high of 2.4 (Facultative Upland +). The average Prevailing Wetland Coefficient for the north part of the preserve is almost right in the middle between wetland and upland, -0.7 (Facultative), corresponding to a plant community of moderate wetness.
|Prevailing Wetland Coefficients on the north side of the preserve.|
Shannon-Wiener Diversity indices were calculated for the vegetation inventoried in each sampling plot. There have been only very slight variations in the values listed in the table below. The Shannon-Wiener Diversity indices across the north part of the preserve range from a low of 1.17 to a high of 2.68, with an average value of 2.01. These are moderate values as common and relatively undisturbed native forested wetlands in southeast Michigan typically have values in the 2.0 to 3.5 range. The generally low diversity of the north part of the preserve probably reflects the dominance of several species as opposed to a lack of species richness. However, species richness is somewhat lacking and remains a concern for long-term quality and sustainability.
|Shannon-Wiener Diversity Indicies on the north side of the preserve.|
Floristic Quality Index
From 2011 through 2014, the Michigan Road Preserve has consistently had an FQI value of 26.7, which places it in the middle of the “moderate to good” spectrum, on a scale of 0 to 50, as described earlier. With the discovery of a few new species in 2015, the FQI has raised slightly to 28.3. The preserve has a higher FQI than average natural areas remaining in Michigan, but floristically, is not significant on a statewide basis by the FQI standard. But it is not entirely the individual plant species that make the preserve a valuable natural area. The unique assemblage of species, sand ridge and depression landscape, sand soils, range of hydrology, wetland content, forest cover, and wildlife values, among other aspects, make this an important natural area. The combination of all these features indicate a relatively intact, native natural area retaining many important natural functions and likely to support rare or uncommon species. With further species surveys, the FQI is very likely to rise.
A unique aspect of the vegetation on the Michigan Road Preserve is the northern flora represented by Red Maple, Paper Birch, Black Ash, Speckled Alder, Nannyberry, Black Chokeberry, Low Sweet Blueberry, Wintergreen, Bunchberry, Dwarf Raspberry, Bracken Fern, Wild Sarsaparilla, Starflower, and Marsh Saint John’s-wort. While these species occur throughout Michigan, their distribution is generally concentrated north of Michigan’s Transition Zone. Their widespread occurrence on the preserve indicates a northern plant community somewhat disjunct from its usual location north of the Transition Zone. This is characteristic of the flora in the Port Huron area, influenced by the cooler growing season and extensive sand soils near Lake Huron. Historic fire disturbance may also have been another important factor in maintaining the northern flora. At the same time, the occurrence of southern species enhances the diversity of these areas. Distinctly southern species on the preserve include Black Oak, Juneberry, and Smooth Highbush Blueberry. This unique blend of northern and southern flora in Saint Clair County, particularly the Port Huron area, was described about 100 years ago by noted Port Huron botanist Charles K. Dodge.
|Bunchberry (white flower) and Fringed Polygala (violet flowers) on the preserve.|
|What appear to be Northern Pin and Black Oak hybrids on a sand ridge on the preserve, shown after the 2015 spring burn of the area.|
On 2015 May 01, the TLC conducted its second controlled burn on the Michigan Road Preserve. For details, refer back to: http://thumbland.blogspot.com/2015/10/2015-spring-burn-bill-collins-executive.html
|2015 spring burn on the preserve.|