GUIDANCE FOR DELINEATING INVASIVE AQUATIC PLANTS FOR MANAGMEMENT

Transcription

1 GUIDANCE FOR DELINEATING INVASIVE AQUATIC PLANTS FOR MANAGMEMENT Objectives 1. Delineating and qualifying boundaries of invasive aquatic plants for management purposes. 2. Collect additional information on the geographic locations, size (boundaries), and relative abundance of invasive aquatic plants for management purposes. 3. Identify native aquatic plants and their locations in proximity to invasive aquatic plants to inform management decisions including buffering treated areas. Introduction Delineating vegetation is critical for natural resource planning, management and protection. A map provides a physical representation of where plants occur. By classifying vegetation, selected properties of the plants (e.g. species identity or relative abundance) can be used to describe and differentiate areas for management purposes. For example, the map can depict areas where invasive plants occur and distinguish areas with native plants. There are multiple needs for data on aquatic plant beds or stands. The MN DNR Invasive Species Program, lake groups and local units of government are interested in mapping stands of invasive and native aquatic plants for management activities (e.g. Eurasian watermilfoil, curly-leaf pondweed flowering rush or starry stonewort control as well as native plant protection), assisting in rapid response planning, evaluating and tracking populations over time. An aquatic plant surveyor must delineate invasive aquatic plants before management actions are undertaken. If a contractor or lake group completes a delineation, some effort by the DNR to verify the results is required. Generally, large beds or stands of invasive vegetation should be mapped as contiguous areas for management (polygons) and isolated plant occurrences mapped as points. Aquatic plant definitions and classifications Delineation: a specific type of survey recognized by the MN DNR that is used to identify areas of vegetation either targeted for control or identified for protection. Polygon: a shape, usually drawn with GIS or GPS, which describes the area of a plant stand or bed to be controlled or protected/buffered from management activities. Waypoint: a sample point or survey point taken with a GPS unit where plant observations are recorded. Stand or Bed: an area of vegetation that is identified based on distinctiveness and uniformity. It is mapped or delineated as a polygon based on the target species presence and abundance. Treatment: management activities used to control an invasive plant species generally through mechanical, chemical or biological means. Note MN DNR permits are required in most instances. 1 P age

2 Target Plant: the plant species (invasive or native) identified as the primary concern for the delineation (e.g. for control or protection purposes). Associated Plants: plants that are observed in a bed or stand but are not dominant. Both native and invasive plant species should be noted during the delineation as well as their respective relative rake fullness or visual abundance (see definition for Relative Rake Fullness or Visual Abundance below). Plant Abundance via. Rake Sampling: an abundance ranking (0-3) based on the number of plants or percent plant coverage observed at a sampling point (waypoint). For invasive plant delineations these rankings are used to determine potential management areas for control purposes. MN DNR Invasive Species Program uses a quantitative ranking of 0-3 based on rake coverage. (See Table 1 below for clarification). Table 1. Quantitative ranking (0-3) used to estimate plant abundance based on rake coverage and/or visual observation. A zero (0) ranking indicates no target plants were retrieved or observed in a sample. Stand Density: an overall abundance ranking for a target species within a larger plant stand or bed. Stand density can be used as an assessment tool by comparing stand densities over time or before and after management. Equipment A checklist of recommended field equipment is provided in Appendix. Data can be recorded on paper forms or electronically. If there are historic maps of target invasive plants or previously controlled areas, surveyors should review them and make copies on waterproof paper (e.g., Rite-in-the-rain ) to bring in the field or input them into their GPS devices. 2 P age

3 If mapping with a hand-held or boat-mounted GPS unit (e.g. Garmin Map 76 or GPS Map 78), surveyors must collect a series of waypoints, boat tracks and notes to identify the plant species associated with each delineated plant bed or stand. Post-processing of data generally occurs with a desktop computer using a GIS mapping program such as ArcMap or Google Earth to create delineated polygons (i.e. treatment polygons, or native species beds or stands) from the boat tracks and waypoint observations. Processed data should be submitted to the DNR including GIS files and associated invasive/native plant data (as a tabular electronic spreadsheet) so that a map can be recreated if needed. Delineation timing and purpose A field delineation is simply the process of mapping the extent (edges) of invasive and native aquatic plant stands or beds. Surveys are best done under low to moderate wind conditions (< 20 km/h or 12 mi/h). Surveyors should time pre-treatment delineations when the target aquatic plant is actively growing and observable. The distribution and abundance of plants can change dramatically throughout the growing season and from year to year. For this reason, delineations are generally performed during the season in which management has been planned for the target plant. To schedule early season delineations (typically applies to curly-leaf pondweed), communication with lake residents/users can be helpful as they may have knowledge of when plants are present. To evaluate effectiveness of management efforts, a follow-up delineation can be performed after treatment or the subsequent year depending on the management strategy. Lastly, additional surveys, such as point-intercept surveys, may be appropriate to identify changes in a plant community over time and at a lakewide scale. The objective of a point-intercept survey is distinct from a delineation and these surveys are not ideal to identify areas for invasive plant control (i.e. delineate polygons). Conducting the delineation Delineation of a target plant occurs through field observations generally made via three methods. These methods are often combined during a delineation and include: visual observations, SONAR (fishfinder) observations, and thrown or spun rake observations. The ability to visually identify the boundaries of submersed plant stands varies with water clarity, depth, wind, plant height and plant cover. If water clarity is limited, a surveyor must use a sampling rake or other below-water sampling device to identify plants. A metal rake head attached to a rope can be thrown and dragged along the lake bottom, or a rake head attached to a long pole pushed to the lake bottom and spun (rotated). The surveyor then records each plant species collected on the rake and quantifies rake fullness to characterize relative plant abundance. SONAR can assist in below water plant observations but must be verified by a sampling rake. Delineation field process 3 P age

4 1. Pre-survey: gather previous year s delineation or polygons and upload this information on the GPS unit for reference. If helpful, review bathymetric maps (lake contours) to get an idea where submersed invasive plants may grow. 2. Record the track of the boat with the GPS receiver. 3. Beginning at one end of the first area to delineate, run transects (paths) perpendicular from shore lakeward, using a zig-zag pattern for narrow littoral zones (See Figure 2 below). Figure 1. Example of delineation process. Polygon indicates an invasive plant treatment area, solid black line indicates boat track, and waypoints indicate plant abundance observations. 4. Along the transect, take waypoints at regular intervals noting target and associated plant observations (see below Sampling Waypoints for more information). If the target area is narrow, make the intervals short and vice versa. NOTE: A general rule could be applied which allows for points to be spaced meters apart on small lakes ( acres), 35m on medium lakes ( acres) and 50m on large lakes (1000+ acres). Additionally, one hundred (100) waypoints is a general minimum number of survey points to be taken on a small waterbody. However, number of survey points will vary depending on the size of survey area, extent of infestation, and whether the stands are monocultures or are composed of a diverse mix of plant species. 4 P age

5 5. As sampling progresses to deeper depths, stop when the target plant is no longer observed. 6. Repeat this process until the entire littoral zone or targeted area has been surveyed. Postprocessing of collected data is then completed using GIS software to edit polygons and create a map. 7. As an option, surveyors can assign a qualitative stand density rating for each delineated plant stand based on the target plants (see Figure 6). Surveyors can sample random points within the stand by rake toss and use the average rake-collected relative abundance of the target plant (on a scale of 1-3) to characterize stand density. Sampling Waypoints: (At each sample point) 1. If visibility is adequate, record visual plant observations or use a sampling rake if inadequate or to verify plant species present. Use SONAR to assist in detecting plant presence, especially at deeper depths. Record and estimate the range in depths where target invasive plant occurs. 2. Record water depth at all sample points (if available). 3. Record an estimate of relative abundance of the target plant at each sample waypoint (use the abundance scale of 0-3 and see Table 1 for rake abundance clarification). 4. Record observations of native plants when present and their relative abundance (i.e. rake fullness). Early season native plants may be sparse, small and more difficult to detect. Note the presence and location of stands of floating leaf and emergent vegetation. 5. Other parameters or observations to consider: Water temperature: Record 1-3 observations of water temperature below surface at dispersed locations around the lake including GPS location and depth of temperature reading. Some observers record temperatures from different depths: surface, mid depth, and near lake bottom. Water clarity: record at least one observation and GPS location of Secchi disk transparency during survey at a lake depth that exceeds the Secchi observation. Other observations: it may be helpful to include the weather and conditions of your survey day. Additionally, any other notes that may be helpful to your delineation assessment. 5 P age

6 Figure 2. Example field data recording sheet for delineation surveys. 6 P age

7 Figure 3. Example field data recording sheet for delineation survey on Middle Cormorant Lake. Abundance ranking represented as 1-3, zeros (0) not listed. 7 P age

8 Figure 4. Example delineation map with proposed treatment polygons for Eurasian watermilfoil. Points courtesy of Anoka Conservation District. 8 P age

9 Figure 5. Example delineation map of Eurasian watermilfoil. Lake Josephine, Ramsey County, MN. 9 Page

10 Figure 6. Example map inset of delineated polygons of Eurasian watermilfoil with qualitative density ranking. 10 P age

11 APPENDIX Example Field Delineation Equipment List Clipboard Lake Access point / Map Data sheets on waterproof paper (Rite-in-the-rain ) or electronic data collection device Bathymetric map of lake Pencils Double sided rake on rope or metal garden rake with handle Plant ID books/ AIS identification sheets Polarized sunglasses Plastic bags/collection containers Sharpie marker Sorting trays for plants and invertebrates (white or light color) Hand lens Digital camera Depth Pole or SONAR fishfinder Boat / Canoe Life Jackets [1 each wearable (USCG Type 1, 2, 3, or 5) and 1 throwable (USCG Type IV)] GPS Unit with historical data/polygons uploaded Secchi disk 11 P age