Examples of Monitoring Projects
Monitoring of exotics has been an on-going activity since the early decades of this century, but has focused almost exclusively on agricultural and forestry pest species. These include weeds, destructive insects and other invertebrate pests and plant pathogens that have a substantial impact economically.
Phytosanitary inspection of in-coming plant materials by government officials is one form of long-term monitoring that minimizes the risk of exotic pest entries into a country. Inspections and federal and provincial weed and seed acts regulate the entry and movement of exotic plants, especially those that are considered harmful or noxious. Major efforts have also been made in the first half of the 1990s to document the spread of some high profile invasive species such as zebra mussels and purple loosestrife. The national purple loosestrife survey campaign encouraged public participation through the reporting of sightings using a standard report form. Many other plant exotics that do not have a direct agricultural or forest industry connection warrant more extensive data compilation than is presently available in order to clarify the extent and degree of infestation and impact on native ecosystems.
Some of the major invasive or potentially invasive exotic plants are tabulated in Appendix 1 by geographical occurrence. This listing supplemented by reading a booklet such as that on Invasive Plants of Natural Habitats in Canada (White, Haber and Keddy 1993) can be used to select species of interest for possible monitoring studies. Specific examples of monitoring activities are given here that can be adapted to local circumstances and species present. Monitoring aids are briefly outlined and illustrated in Appendix 2.
Each monitoring project undertaken should have a clear purpose established. This will make it easier to set out a course of action for monitoring so that useful information can be compiled and, where warranted, specific control actions can follow. Some projects may be initiated to monitor the spread of a species in an area of establishment with the view to eradicating small infestations to slow the spread. Monitoring could also be done as part of an early warning system so that any newly established plants or populations in an area previously beyond the range of occurrence can be readily identified and removed to prevent their spread. Other types of monitoring, such as the study of the rate of population or clump expansion or first flowering, provide valuable biological information that may allow for improved control measures. As well, monitoring activities can be directed at determining the impact invasive species have on the native flora of monitored plots.
The following project examples and supplementary ideas represent five main types of monitoring activities that can be undertaken to document exotic plants:
- Occurrences - determining the presence of all exotics in a region, plot or natural area and the recording of new exotic arrivals with time
- Abundance - recording changes in numbers or area covered within specified areas or plots
- Expansion - measuring the rate of expansion of a clump or population
- Biology - recording seasonal flowering events; longevity of a perennial exotic; seedling survival; seed production in different habitats; presence of herbivores/pollinators
- Impact - replacement of native plants in plots; change in use of the plot by animals as the exotic becomes dominant
The examples provide a basic framework for monitoring activities that can be modified to suit individual interests or needs of the region. Projects can be undertaken solely on species that are presently known to be invasive in natural habitats or a broader focus can be maintained by monitoring other exotics whose invasive potential have not been clearly, or at all, established.
Unlike monitoring activities that record the change in biodiversity of native fauna and flora within a region or specified plot, the monitoring of exotic species commonly has, as its ultimate purpose, the control or eradication of such species. The following projects generally are based on this principle or on the gathering of data that may ultimately be of value in providing a better understanding of the biology of exotics so that their proliferation can be controlled.
Project 1. Linear Highway Surveys
Purpose: The monitoring and eradication of recently established plants or small populations of a species (or more than one species) to slow the spread within a region or to prevent the establishment within an area not previously occupied. This project can be considered as a variation of the "Adopt a Highway" programme. Instead of keeping the highway clean of refuse, the project is aimed at controlling the spread of troublesome non-indigenous plants.
Overview: In order to take action in controlling an exotic plant, its current distribution must be known. This requires the mapping of occurrences and recording of some rough measure of population size so that individual plants or relatively small populations that are most amenable to eradication can be identified. As well, yearly monitoring of the same roadsides or study areas will indicate the establishment of new plants or populations that are also suitable candidates for eradication. Such monitoring along stretches of roadways within a specified geographical area, together with control actions, will slow or prevent the spread of nuisance plants.
Methods: For roadside wetland or woodland edge surveys, a stretch of primary or secondary highway is selected where suitable habitats for monitoring occur. Specific start and end points are selected so that a reasonable monitoring distance is included. Ten to 50 km routes, or even longer, may be manageable, depending on the kind of transportation to be used. In some areas, monitoring by bicycle may be possible or preferred. The frequency of the habitats present and time and effort to be expended are other considerations that will determine the lengths of monitoring routes.
A new road map can be used to record the positions of the species sightings. A site number should be placed on the map at the approximate kilometric position from a landmark such as a local town or major crossroad indicated on the map. A log entry should also be recorded in a field book or on a special monitoring records form such as that in Appendix 2 (Exotic Plants Roadside Monitoring and Action Form) for all sites located during a particular monitoring survey. To help prioritize sites for eradication, it is useful to record whether the sites are near park boundaries or in areas where further spread might result in infestation of natural areas of particular significance. For each significant site, a detailed Exotic Plant Survey Record Form, similar to that in Appendix 2 should be completed to document the occurrence in detail.
If the intent is to promote action on small, easily eradicated sites, then the approximate number of plants or area in square metres occupied, together with a brief indicator of the type of habitat, should be recorded. This will allow for the selection of sites that might be most amenable to eradication or control. A reasonable estimate of the area can be obtained by determining, through experimentation, the size of pace required to approximate one metre and then pacing off two sides of the sites. To ensure a somewhat greater accuracy, a small inexpensive retractable tape measure can be helpful as part of the field equipment to establish pace length and, as well, to measure plant heights, diameter of clumps or depth of water. Actual measurements with a long tape measure can also be made if precise quantification is desirable.
A standard form can be prepared in a tabular layout that can be used to record excursion results. To avoid confusion between surveys of different years, no duplicate numbers should be used. A sequential number should be used without duplication from year to year. A common convention in ecological studies is to adopt the two digit abbreviated year as a prefix for the site identifier with the subsequent digits representing the specific site location for that year (e.g., 9723 for site 23 during 1997). This site location number should remain a unique number from year to year so that the fate of individual sites can be properly monitored. A different colour of pen or pencil can also be used to distinguish sites recorded in subsequent years on the reference map.
For those interested in greater precision in recording population positions, one or more topographic maps of a suitable scale such as the 1:50,000 NTS (National Topographic System) maps can be used to record the localities along the roadside. This will also allow for precise coordinates, either latitude and longitude or the UTM military grid easting and northing values to be determined readily. Such coordinates will allow for computer mapping of localities and the development of databases that can be used for mapping and record management. If data are to be recorded in a database or spreadsheet format, site numbers in the format suggested above can also be readily sorted by computer if no other characters are placed between the year and the site identifier. When coordinates are required for a study, the tabular record form should have a place for this information. The inclusion of standard coordinates on labels of voucher collections is also a valuable and precise means of identifying site locations.
Although expensive and beyond the normal scope of use by naturalists, a hand-held GPS (global positioning system) can be purchased that provides easily captured coordinates for roadside localities and open area surveys. These units work best where there is little interference from trees blocking signals from the overhead satellites that make possible geolocation to within approximately 10 m for ordinary portable units. Storage of site coordinates and direct transfer to computer databases is possible for computer mapping purposes and analyses using GIS (geographic information systems).
With information compiled on population location and size in square metres, decisions can be made on which sites might be suitable for eradication or control by manually sorting sites based on the maximum size of area that can be most readily treated by an individual or group. Information stored in database or spreadsheet form is much more readily retrievable, especially if there is a large data set.
The methods outlined here can be applied also to recording and monitoring species occurrences within a region of defined aerial extent. Surveys can be conducted along all of the roadways within a township, for example, and frequency of occurrence of populations of a specified minimum size can be calculated for the region per km of road length. Most projects that require the calculation of abundance within an area would require some form of careful notation of population sizes as part of the inventory of a species. A general notation of frequency per linear km of distance surveyed along a highway could be recorded by using a simple set of relative frequencies. Examples of categories of frequencies are absent, infrequent, sparse, common and abundant, with each category representing an occurrence based on a defined level of plant or patch frequencies (see Groh and Dore 1945).
Project 2. Trail Monitoring
Purpose: The establishment of an early warning and exotic species eradication programme for hiking and nature trails.
Overview: The development and use of hiking and nature trails in natural areas of vegetation results in opening corridors that allow weedy and invasive plants an opportunity to become established in places normally not readily accessible. Monitoring the spread and possible invasion of natural areas by non-indigenous species allows for the early detection of potentially troublesome species that can be eradicated before they become firmly established and have a negative impact on the native flora. Subsequent monitoring of sites where exotics are removed will ensure that complete eradication can be effected. A monitoring plot can also be established as a study project to determine the impact of an established population of an invasive plant on the native ground flora of the site.
Methods: Volunteer monitors from a club are assigned to specific portions of hiking or nature trails that pass through relatively undisturbed wooded or other types of vegetation for the purpose of recording significant incursions of non-indigenous plants. A programme of monitoring trail sections is established whereby each monitor records the location of significant patches of weeds or of newly established plants of an invasive species for the purpose of eradicating such point sources of invasion.
Aids to monitoring could include a photocopy of the official trail map with landmarks clearly indicated. These will be used as reference points for pacing off distances to identify the location of infestations. The use of an NTS map sheet with the trail position indicated provides a more accurate means of identifying infestation positions. Such a topographic map allows for latitude and longitude or UTM coordinates to be recorded for precisely locating sites of establishment. This may be particularly desirable in areas where obvious trail landmarks are not available. A survey report form similar to the Exotic Plant Survey Record Form (Appendix 2) can be used to record information on the exotic species localities found. A specific trail form similar to that in Appendix 2 can also be prepared that provides a running account of infestations and actions taken. A unique site occurrence number should be used to keep track of each point of infestation over subsequent years. A specific identification number such as described in project 1 is recommended.
When weeds or invasives are located, their positions can be indicated along the trail with a short length of colourful flagging tape attached to a nearby shrub or branch. The unique site number should be written with a waterproof felt marker on the tape. The site is then indicated on the trail map and recorded in the field notebook or special report form. If the infestation consists of only a few herbaceous plants, these can be uprooted by the monitor and bagged for later disposal in a public landfill site or by burning. Larger infestations or specimens such as invasive shrubs that are more difficult to remove can be scheduled for action at a later time by the club's volunteer "Weed Eradicators". Subsequent monitoring of each identified site of infestation will allow newly emerged seedlings to be removed to ensure complete eradication.
As an additional activity of club members, the impact of an infestation on the local flora can be monitored by establishing a plot in a manner similar to that described in Project 4.
Project 3. Plant and population expansion
Purpose: To document the rate of expansion of a single plant, patch (clone) or population of an invasive plant.
Overview: An understanding of the rate of expansion of an exotic plant can be useful in making inferences on the history of establishment of a population and can provide data useful in determining the potential threat of a species. The faster the rate of expansion of a species the greater is its potential for becoming a troublesome weed or, in some cases, a troublesome invasive. To determine the rate of spread, a point source of establishment and of potential infestation within an area is located and the expansion is monitored over a period of several years. A point source can be an individual plant, colony or small population. The rate of spread can be determined within a single habitat type or within different habitat/substrate types to compare the species' response under varying conditions. Such information is valuable in determining priority species for control within a region.
Formulas for patch expansion have already been developed for leafy spurge that permit the determination of the age of a patch or the total number of stems if its area is calculated (Bangsund, Stroh and Leitch 1993). The rate of patch expansion, as well as the stem counts per unit area, were the underlying variables that needed to be calculated based on field observations. The simple procedures outlined here can be used to determine the rates of invasion of a species within a habitat. If statistical reliability of data is an important factor, professional assistance should be obtained for the appropriate selection of sample sizes for monitoring.
Methods: The monitoring of expansion rates will vary with the species to be investigated. For perennial terrestrial species, the growth and expansion of a single plant can be followed as it increases in size and produces additional aerial stems to form a patch (clone) that increases yearly in size. This is easiest for shrubs and those species with a prominent underground rootstock such as is found in flowering rush, leafy spurge, Canada thistle and various grasses that tend to reproduce vigorously through vegetative propagation to form discrete clumps. Even for such species, one needs to keep in mind that their spread across the landscape, in general, also depends on the ease of seed dispersal, seedling establishment and other factors related to human activities that promote spreading of plants.
To monitor an exotic that is an annual, biennial or short-lived perennial, the rate of expansion of the species must be determined based on the overall spread of the local population from the initial point of introduction. The vegetative reproductive capacity of an aquatic such as European frog-bit can be studied by following the yearly growth of one or more individual plantlets that forms in the spring.
In every case, the plant or population being monitored should represent an isolated occurrence where data collected on expansion will be based on that selected individual or population. There should be minimal chance of including plants in the expansion data that have originated from an outside source of seed or other means of establishment.
A) Basal area expansion of a perennial plant. The expansion of area occupied by an individual plant, such as a shrub, can be determined simply by measuring the yearly diameter, each fall or spring, with a metric measuring tape held at the widest point of the branches on opposite sides of the plant. For a large shrub, either an assistant holds the tape at the outer edge of shrub growth on one side or a marker is placed on the ground directly in line with the outer limit of branch growth (the drip line) and the measurement is taken from this point to the outer limits at the other side.
To ensure that the same individual is recorded, a ribbon of flagging tape, for better visibility, can be used together with a plastic label that is securely attached and marked with an identification number. If fading is a problem, the label may have to be replaced on a yearly basis to ensure correct identification and monitoring. In forested areas, aluminum labels should not be used because deer tend to chew on these. An additional notation of the exact position of the plant should also be made based on distances from a readily discernible marker point. A topographic map would be very useful in recording the position of the plant.
The yearly increment in area occupied by the plant can be approximated and determined by using the standard formula for the area of a circle (pi * r²). If the species occurs in widely different soil types and moisture regimes, monitoring of individuals in different sites will provide a better understanding of the species' potential for growth under different conditions. If desired, the yearly increase in height can also be measured and graphed. To eliminate individual variability within a site, several plants, perhaps as many as 5-10 should be monitored and the results averaged. To determine whether there is a meaningful difference in expansion of plants between sites, will require a more technical approach based on using statistical tests of significance. Such tests can be obtained from basic statistical reference books.
If the species does not seem to have clearly delimited substrate preferences, 10 or more plants can be monitored across a range of sites within one of the ecoregions described in A National Ecological Framework for Canada (Ecological Stratification Working Group 1996). A yearly average can be determined and plotted to show the increase in ground space occupied by the exotic being monitored.
A simpler alternative approach to determining the change in basal area occupied by a woody exotic as it ages is to measure the diameters of a sizeable number of shrubs. A total of 30 shrubs of different sizes, from very small to the largest available within a site or area should be measured. The thickest stem within the centre of each shrub is cut off near its base and the annual growth rings counted so that basal area can be compared with age. A graph with age on the x-axis and diameter on the y-axis can be plotted to show the increase in basal area with age.
B) Basal area expansion of a clump or distinct patch. When dealing with herbaceous perennial invasives that tend to form expanding patches as the result of the vegetative spread of the rootstock, a similar technique to that outlined for a single shrub can be used. The main difference is that the centre of the clump should be marked with a plastic or metal stake and a plastic label attached with the patch identifier written in pencil or waterproof ink. The expansion of clump diameter should be monitored for different initial sizes of clumps over a period of perhaps 3-5 years, or more if possible. As well, to minimize individual patch differences or unforeseen factors, it is always preferable to monitor several patches. It would be preferable to monitor 3-5 clumps for each of several initial size classes ranging including small, medium and large. The results of yearly expansion within the classes can be combined and averaged as long as the clumps that were selected within each category were of relatively identical initial diameters.
It would be preferable to select clumps for monitoring in areas not heavily infested by the species to ensure that within-species competition is not one of the variables that is controlling or limiting expansion. A worthwhile monitoring activity would be to compare patch expansion in areas dominated by certain assemblages of other native or exotic species to determine potential impact on growth rate of the exotic being monitored.
Monitoring results can be graphed, as for individual shrubs, to show the yearly expansion. Based on the recorded expansion rates per year, a formula similar to that developed for leafy spurge may be used for determining the potential rate of coverage of an infested area over a specified period of time (Bangsund, Stroh and Leitch 1993).
C) Rate of propagation of a floating aquatic (European frog-bit). In the course of a season, a single overwintering bud of European frog-bit (Hydrocharis morsus-ranae) produces many floating plantlets, all attached to a common stem. At the end of a growing season, in some areas, thick dense mats are formed by the accumulated vegetative biomass. The current distributional pattern of this species in Ontario indicates that it may be limited to watersheds primarily to the south of the Canadian Shield.
Monitoring the rate of vegetative expansion and biomass productivity in different watersheds where the species is established would be useful in understanding the limiting factors that may restrict the species' spread. By tagging an individual plantlet early in the season, the number of plantlets produced by the end of the season when first frost arrives, or by a specific date, will give an idea of the vegetative reproductive capacity of an overwintering bud. Careful separation of the tagged plants and their offshoots from other plants is required to determine accurately the number of plantlets produced in one season. The individual plantlets must be properly identified with a suitable plastic tag with identifier numbers written in pencil or waterproof ink. The tags may need to be attached with thin, flexible monofilament fishing line that will not decay in the water over the course of the season.
A more complex field study that could be suitable for a graduate student project would be the monitoring and determination of the propagation capacity based on numbers of plants and biomass produced by a single plantlet in different watersheds with different nutrient levels and pH. Sites in watersheds throughout the species' range in Ontario are selected on the basis of differing nutrient and pH levels. Individual plantlets are weighed in a standard quantity of water early in the season, tagged and monitored over the course of the summer.
At the end of the season, the progeny of the parent plantlet are carefully extricated from the surface mat of plants and weighed. The water is drained off and the plants are dried with absorbent towelling and left in the air for a short period to remove additional films of moisture. The fresh weight of the season's growth can be compared with the initial weight of the plantlet itself and, as well, the dry weight of the biomass can be determined following standard procedures for such determinations.
The results can then be evaluated in reference to the nutrient levels and pH in the water column below or within the mat. Additional information can be gathered over the season on nutrient and pH changes to evaluate further the changes in the environment as plant mats proliferate. Control water samples should also be evaluated for nutrient and pH changes from adjacent sites where European frog-bit is not growing.
The results from such field monitoring studies will contribute to an understanding of nutrient requirements and potential limiting factors for the growth of European frog-bit.
D) Expansion of herbaceous plants (annuals or biennials). Annuals and biennials tend to spread primarily by seed and therefore produce local populations of plants. This is in contrast with some herbaceous perennial exotics that form discrete patches (clones) primarily by vegetative propagation. A perennial exotic will remain in place and expand its area of coverage vegetatively with time. An annual or biennial, however, depends primarily on seed production and its dispersal. Reliance on seed dispersal results commonly in the movement of populations from the original point of introduction outward depending on factors such as dispersal agents for the seeds. For annuals and biennials, change in population size and spatial displacements must be monitored.
To monitor expansion of such populations, it is desirable to select isolated populations to minimize risks of entry of outside seed sources during the course of the monitoring study. It may also be preferable to select a recently established, small population or site where only a single or few clustered specimens are growing. This is more likely to ensure that no other seeds are present in the vicinity that might lead to misinterpretation of the rate of spread from the initial parent population or plant.
Depending on the size of the population, a monitoring plot 1 m² is established centred over the parent plant or population. The corner posts of the plot can be marked with metal pegs but bright plastic pegs, such as thick durable tent pegs, are preferable. If discreetness is a necessity, only the tops of the pegs are left visible above the ground. As the population expands, this initial 1 m² plot can form the centre of a larger plot based on a 5 x 5 m grid. A small plastic stake can be used to mark the position of the initial plant or centre of the small population. The location of the plot should also be recorded in a field notebook using distance measurements from readily identifiable marker points or landmarks. If it seems desirable not to leave a permanent indicator of the centre of the original population, the location will have to be recorded through measurements based on the corner post locations.
The expansion of the population can be monitored in a number of ways. If the population spreads symmetrically, a metric tape is used to measure the distances from the original centre to the stems of the outermost plants that have become established. An average distance of spread is then determined in cm or metres per year from the original centre. These measurements are repeated yearly at the end of the season when mature plants have developed or first year rosettes have formed. The total area of spread can also be approximated by calculating the area of a circle (pi * r²) using the total linear expansion from the original centroid to the outer margin as the radius.
If a population tends to expand asymmetrically under the influence of the wind carrying seeds primarily in one direction, a convenient method of tracking its movement is by overlaying a 1 m quadrat divided up into a 10 or 20 cm metric grid (see Appendix 2). The outermost periphery within which all of the plants are found is recorded and transcribed at a reduced scale to a sheet of graph paper. The approximate total area of coverage by the population can be determined by summing the number of square cm on the paper graph. A more detailed yearly coverage can be determined by summing the basal areas of individual plants in the population. This more detailed calculation will require the transfer of basal area data for each plant to a paper grid. This can be done with the use of a pantograph. This is a specially designed armature that enables one to copy the outline of an object at the same or different scale (see Weaver and Clements 1938). The basal areas of individual plants can also be carefully transferred to the graph paper by visual inspection of the outlines in relation to the grid lines. The rate of movement of such a population can be determined by measuring the distance of its mid-point from that of the original centre of the population. The number of flowering stems within the total area occupied at the end of a season can also be recorded as part of the data gathered to document population expansion.
An overhead photographic record of a quadrat can also be made using a low stepladder to gain enough elevation to take the picture. The four corners of a 1 m² plot should be demarcated and visible in the field of view. By taking an overhead photograph aided by a wide angle lens, the enlarged print can be used to record the positions of the plants within the plot. It is important to ensure that the same height is used for repeat photographs and that the camera is held above the centre of the quadrat. Some improvisation will be necessary in order to hold the camera directly over the quadrat and to ensure that the entire plot is in view and in focus. If a string grid is already in place on the quadrat this will aid in recording basal areas from the photo.
The print should be enlarged to an appropriate scale to facilitate conversion of areas from the quadrat to the print. A 35 mm single reflex camera can be used for this photography but a camera with a larger film format would be preferred in order to allow for clear print enlargements to be made. If the quadrat is within a shaded woodland site, the use of one or more electronic flash units may be required or a film with a high ISO value must be used to ensure that available light will provide a proper exposure.
Project 4. Monitoring impacts on native vegetation
Purpose: To monitor the impact of the spread of an invasive plant on native vegetation.
Overview: Few studies are available that document the effect of an invasive plant on native species within natural habitats. Such studies require careful monitoring of individual plants within a plot over a number of years. The following procedure can be used to document changes in numbers of plants and species composition within a plot where an invasive plant has become established. Such studies may be most readily undertaken for terrestrial species within open and wooded habitats. The size of the monitoring plot (quadrat) needs to be selected to accommodate the size of plants being monitored. If the invasive is a shrub, the size of the plot may need to be in the order of 5 x 5 metres square so that ample vegetation is included for study. For the study of grasses and herbaceous vegetation in fields and woodlands, a quadrat of 1 square metre is commonly used (Weaver and Clements 1938). The methods described for recording and charting plant numbers and positions within a plot allow for the compilation of both simple observations on the numbers of plants and species that are present with time as well as changes in area occupied by each respective species.
Methods: If monitoring an invasive shrub and its impact, a quadrat should be set up that includes one or more young shrubs and other native vegetation whose change with time will be monitored. If a herbaceous species is selected, the quadrat should include only one or a few stems or a small clump of the invasive among a suitable mixture of native species. The quadrat should be selected with due precaution to avoid disturbance through human activities. Permanent corner stakes should be fixed in place and the layout verified that it is a square.
Ensuring that a quadrat is square is readily accomplished. A quadrat is square when the diagonals are equal in length. The initial corner lines can be established at right angles, especially for a large quadrat, by using the Pythagorean theorem - the 3/4/5 rule - that deals with the square on the hypotenuse. If two lines are extended at an acute angle from a common point, with one being 3 units and the other four units long, the angle becomes a right angle when the measurement of the third side of the triangle, the hypotenuse, reaches five units. When monitoring herbaceous vegetation, one need not be restricted to using replicates of individual quadrats. If a suitable area is found with a number of the invasive plants scattered within an elongate area, a linear series of two or more metre square quadrats can be established.
For recording the exact centres and basal area coverage of plants or clumps of both invasive species and all native species in the quadrat, a grid is established. For a larger quadrat this may entail delimiting the area within the corner posts by a strong cord. A metric grid is then established subdividing the area into appropriate units depending on the size of the quadrat and the abundance and location of plants in the quadrat.
A letter code is then assigned to each species, perhaps representing the genus or scientific binomial of a species. The centre point of each plant and the species designation is indicated on graph paper of suitable size to adequately record the number of plants present. If the basal area, representing the amount of space occupied by a plant, is to be recorded, a special ruler can be devised (see Appendix 2) that will give the approximate basal area when the diameter of the plant or clump is measured. A unique number can also be assigned to each plant to track its presence and change with time.
Setting up individual square metre quadrats can be done perhaps most readily by cutting out a template from a thin sheet of plywood or hardboard with a square hole with one metre sides. This can be used to place the four corner pegs and as well to establish a 10 cm grid across the open area of the template. To do this, small galvanized nails are fixed to the template at 10 cm intervals along all four sides and left to protrude above the surface. Cord is then wound back and forward to create the grid. Each 10 cm unit is numbered around the perimeter as indicated in the example in Appendix 2. Other simple methods of demarcating one metre quadrats using narrow strips of wood or metal are also reviewed in Appendix 2.
Yearly data can be recorded in a tabular manner such as in the quadrat record form provided in Appendix 2. The fate of individuals for both the invasive and the native plants can be monitored and recorded in this fashion. Also, a photographic record can be made to record the change in plant occurrences and size within a plot. The method of overhead photography can be readily applied to a small quadrat as described in Project 3D.
A simple means of providing a photographic record of seasonal and yearly changes in growth and expansion of invasives within a site is to use the technique of camera sets. A series of photographs are taken at the same location at regular intervals throughout the seasons and in successive years. A tripod is set on three reference stakes or pegs in the ground with the camera adjusted to a standard height and facing in the same direction for every photograph. Such a technique provides a unique photographic record of changes in vegetational growth as well as the expansion or retreat of exotics and their impact on native species and habitats.
Another way of recording changes in the landscape is to use a modern video camera. Even the less expensive units permit the addition of date signatures to indicate when the segments were recorded. As well, a voice-over will record pertinent field observations to help interpret the status of vegetation changes. The same film is used to monitor the same site throughout the growing season and over a period of several years. The film is relatively inexpensive and can be used to provide footage from a number of angles and at various zoom positions.
Supplementary Project Ideas
Other projects can be undertaken that provide interesting facts that will add to the understanding of the biology of exotic plants. The following are suggestions for possible monitoring studies:
- recording first flowering dates of one or more exotics for comparison with native species in the same habitat
- date of first sign of senescence or dormancy
- seasonal frequency of use of an exotic by insects recorded by major groups
- use of an exotic by native wildlife
- change in seed/fruit production with age of a perennial exotic
- survivorship of seedlings within a plot
- longevity of a clonal exotic
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