Improving land use decision-making and sustainable resource management through greater reliance on scientific knowledge
The Minnesota Department of Natural Resources established the Ecological Monitoring Network in 2017 to track ecological change throughout the state. We will provide data on how the state’s native plant communities are changing in the face of new challenges, such as climate change, invasive species and increasing habitat fragmentation. This effort is being led by the Minnesota Biological Survey, in collaboration with other DNR divisions and partners such as The Nature Conservancy, the University of Minnesota, and the U.S. Fish and Wildlife Service.
Minnesota’s native grasslands, wetlands, and forests provide recreation, timber, water filtration, habitat for wildlife and pollinators, flood protection, carbon storage and other valuable ecosystem services to Minnesotans. These services are threatened by direct and indirect stressors, such as changes in climate and management, increases in non-native invasive species and pollution, and increased pressure on land and water use.
Ecological monitoring in near Pembina, MN
Bees and other insect pollinators are also facing similar environmental challenges, in addition to habitat loss and degradation and population declines related to parasites and disease. Pollinators are vital to maintaining the diversity and reproduction of flowering plants, which are essential components of grasslands, wetlands and forests. There is currently no comprehensive statewide monitoring network that consistently measures and evaluates changes in the vegetation that comprises native grasslands, wetlands, and forests. Without such information, it will be increasingly difficult to detect which factors are driving environmental changes
Goals
University, federal, and state scientists met to define specific goals for how the EMN will compliment other efforts, further scientific knowledge through long term monitoring and deliver results to stakeholders.
Ecological monitoring near Kertsonville, MN
Create a statewide vegetation monitoring network.
Provide information on the status and trends in structure, composition, and condition of native grasslands, wetlands, and forests.
Design a scientifically rigorous monitoring approach that is fiscally responsible.
Provide information to managers and others in a timely manner so that inferences can be made about ecosystem health as a result of stressors.
Aid decision making by natural resource managers, legislators, local units of government, conservation organizations, and land owners to improve conservation, management, policy and land-use decisions.
Complement existing long-term monitoring projects in grasslands, wetlands and forests that span several agencies and organizations.
Design a monitoring network that can be used for research by ecologists, wildlife biologists, entomologists, and other scientists.
Collect a baseline survey of selected groups of pollinating insect species occurring in targeted vegetation types and use this information to inform future monitoring of pollinators related to vegetation.
Objectives
Objectives are essential to research and analysis. They help determine specific metrics (i.e., deer browse pressure, plant species abundance, water conductivity, canopy cover) to quantify for analyses. The objectives below were defined in 2017 and are the foundation for all future EMN research. Preliminary analyses (where available) are linked to specific objectives.
Vegetation
Assess current and long-term trends in vegetation composition, structure and condition within native grasslands, wetlands and forests.
Document plant community change by assigning plots to Minnesota native plant community types in the field and assess quality and condition of native plant communities over time.
Document status and trends in forest structure.
Track long-term trends in forest succession by tracking height and diameter (DBH) and by documenting tree mortality and regeneration.
Determine relationships between landscape context (e.g., size of surrounding natural area and proximity of anthropogenic land use) and changes in native grassland, wetland, and forest vegetation.
Soils
Assess soil type and health in order to relate it to trends in grasslands, wetlands, and forests.
Qualitatively assess topographic position, aspect, and soil type at the onset of monitoring.
In peatlands, document organic soil depth and depth to mineral soil and track status and trends in substrate as it relates to peat type, hummock height, and dominant bryophytes.
Hydrology
Assess hydrology and its relationships to trends in wetland vegetation.
Document long-term changes in hydrology in select sites that represent a spectrum of wetland types.
Assess status and trends of pH in wetland vegetation.
Pollinators and Other Wildlife
Collect baseline surveys of select groups of pollinating insect species occurring in targeted vegetation types.
Document high priority vegetation characteristics related to wildlife habitat (e.g. snags and depth of leaf litter).
Pests and Pathogens
Assess the extent and degree of known pest and pathogen outbreaks.
Field Methods
Data are collected along three 45-meter parallel transects. Woody plants in the tree canopy and subcanopy layer are sampled in a 45-by 10-meter subplot centered along each transect. Woody plants and vines in the shrub layer, and groundlayer plants, are sampled in 24, 1-meter² quadrats (includes a small nested plot) placed every 5 meters along each transect.
Depending on the habitat, various other components are added that are not shown, such as deer browse and coarse woody debris metrics, water chemistry or measurements of grassland structure. A few of the elements of this design are subject to change as we continue to refine our metrics to best capture the data.
A scale diagram of the general plot, showing three 45 meter parallel transects along which various data are collected. Woody plants in the tree canopy and subcanopy layer are sampled in a 45 x 10 meter subplot centered along each transect. Groundlayer plants are sampled in 24, 1 meter² quadrats (includes a small nested plot) placed every 5 meters along each transect. Depending on the habitat, various other components are added that are not shown, such as deer browse and course woody debris metrics, water chemistry, or measurements of grassland structure. A few of the elements of this design are subject to change as we continue to refine our metrics to best capture the data.
A sampling quadrat placed along a transect in a wooded native plant community.
Ecological Monitoring Network Update (July, 2024)
The tables and figures below summarize Ecological Monitoring Network (EMN) progress and patterns in the data being collected, as plots are installed and surveyed across Minnesota. Regular resurveys in the future will document long-term change, or stability, in vegetation in the monitoring plots. The patterns highlighted below relate to several of EMN’s basic objectives: for example tracking trends in invasive species and detecting change in measures of forest health. These highlights represent just a small fraction of the information and patterns that can be extracted from data that will be collected over time at EMN plots.
Summary
EMN has established and surveyed 387 plots, from the beginning of the project in 2017 through the 2023 field season.
We plan to install and collect data from 500-550 plots in total to monitor change in Minnesota’s native forest, prairie and wetland vegetation.
45% of the plots established so far are in upland forests, 23% in open wetlands, 15% in forested wetlands, 12% in upland prairies and 5% in wetland prairies.
42% of plots are on land managed by the state of Minnesota (such as wildlife management areas, scientific and natural areas, and state forests), 20% on federally managed lands, 18% on privately owned lands, and 17% on lands managed by local governments (such as county parks, city parks, and tax forfeited land).
Private Companies, Universities, The Nature Conservancy, and others
12
Private (18%)
Privately Owned by Individuals
69
State (42%) (DNR Managed)
Aquatic Mangement Area
1
State Forest
67
Parks and Trails
18
Scientific and Natural Area
14
Wildlife Management Area
61
Objective: Track effects of browsing on vegetation
Heavy browsing by herbivores such as white-tailed deer can negatively impact forest vegetation. Deer eat tree seedlings and saplings and can suppress regeneration of the species that would otherwise form the future tree canopy. This can lead to shifts in forest composition and structure. Over-browsing of forests can also lead to reduced deer populations long-term and reduce other ecosystem benefits provided by healthy forests.
EMN evaluates the effect of deer browsing on woody vegetation less than two meters from the forest floor.
Browse pressure is measured as a ratio of browsed to total branches of all woody species in the plot.
EMN forest plots in southern Minnesota appear to be experiencing consistently higher browse pressure than plots in northern Minnesota.
Figure 4. Levels of browse pressure within individual EMN plots (ratio of browsed:total branches). Larger dot size represents higher browse pressure by deer. Click to enlarge
Relative browse pressure on canopy tree species for all forested EMN plots
Relative Browse Pressure (RBP) is the ratio of browse pressure on a single woody species in a plot (such as sugar maple) to the total browse pressure on all woody species in the plot. A RBP value greater than 1 indicates higher browse pressure on that species relative to the collective pressure of all other woody species in the plot.
Objective: Document status and trends in non-native invasive plant species
Initial Work and Observations
Non-native species cover is the ratio between the sum of non-native species cover compared to total species cover in a plot.
EMN plots installed in prairies have higher relative non-native species cover than plots installed in forests. This difference is likely driven by two invasive grasses, Kentucky bluegrass (Poa pratensis) and smooth brome (Bromus inermis), that occur largely in non-forested habitats.
EMN plots installed in southern communities have higher relative non-native species cover than plots installed in northern communities.
Click to enlarge
Figure 7. Ratios of non-native species cover to the total species cover at each EMN plot. Larger cylinders represent higher relative non-native species cover. Plots are categorized into four groups by ecological classification system: Fire Dependent Forest (red), Mesic Hardwood Forest (green), Upland Prairie (yellow), and Wet Prairie (orange). There appears to be a spatial pattern of increases in relative non-native species cover from north to south and east to west. In addition, upland and wet prairie systems appear to have high relative non-native species cover than fire dependent and mesic hardwood forests.
Ratios of non-native species cover to total species cover in northern vs. southern floristic regions in four Ecological Systems
Ratios of non-native species cover to total species cover in northern vs. southern floristic regions in four Ecological Systems. Overall, plots in the southern floristic regions of each system appear to have higher cover of non-native species compared to their northern counterparts. The prairie systems have noticeably larger invasive species cover than the forest systems.
Objective: Determine status and trends in volume of coarse woody debris
Coarse woody debris (CWD) is the large dead wood present in the forest. CWD includes both snags (standing dead trees) and fallen logs. CWD plays a major role in natural forest processes, including providing habitat (e.g., small mammals, invertebrates), cycling nutrients, and storing carbon.
EMN staff measure the diameter of all downed woody debris (and strongly leaning snags) ≥ 7.5cm in diameter that intersects the 45-meter-long center lines of EMN plot transects.
From these measurements, volume is estimated for the amount of CWD that would occur in a full hectare ( m^3/ha )
Under natural conditions in forests, leaf litter breaks down slowly leaving the forest floor layered with organic matter in various stages of decomposition, from intact leaves to finely decomposed particles. Several native forest plant species are adapted to this slow layering process, requiring finely decomposed leaf litter, called duff and humus, to survive. Invasive earthworms, transported into Minnesota by human activity since the 1700s, are rapidly removing duff and humus layers in forests throughout many parts of Minnesota. Measurements of leaf litter and humus are collected in forested EMN plots to assess the presence and impact of invasive earthworms.
Click to enlarge
Initial Work and Observations
EMN uses the Invasive Earthworm Rapid Assessment Tool (IERAT) to evaluate depletion of leaf litter on forest floors by earthworms. IERAT scores range from 1 in plots with intact, unfragmented litter, duff, and humus layers (i.e., no worm effects), to 5 in plots characterized by bare mineral soil with abundant earthworm casts and middens (i.e., high worm effects).
IERAT was developed for mesic hardwood forest systems, like sugar maple and basswood dominated communities.
EMN plots show higher levels of invasive earthworm impacts in mesic forests in the southern half of the state relative to the northern half.
Funding for this project was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR). The Trust Fund is a permanent fund constitutionally established by the citizens of Minnesota to assist in the protection, conservation, preservation, and enhancement of the state’s air, water, land, fish, wildlife and other natural resources.
Ecological monitoring in near Pembina, MN
Ecological monitoring near Kertsonville, MN
