Higher Plant Communities

Introduction

These methods are based on recommendations made by Dr D.G. Dawson.

Personal Safety

Please read the safety pages before planning any survey.

Seasonality

Certain species can only be located at certain times of the year. If you are undertaking a survey to produce a list of species at a site you will normally need to make more than one visit to ensure you maximize the proportion of species present at the site that are found during surveying. If you are surveying specific species you should ensure all visits are carried out at the appropriate time of year. If in any doubt consult literature about the species or an acknowledged expert before deciding when to visit. In general, the vast majority of vascular plants flower in spring or summer, so a minimum of two visits during this season would be usual. If the site is known to hold species that can only be found at other times, or likely to hold such species, then additional visits should be made as appropriate

Monitoring Frequency

To be able to monitor long term trends, it is important that surveys are repeated on an annual basis. To allow comparisons to be made from year to year, the visit date or dates each year should not vary by more than a few days. This rule is particularly important when surveying species that are only visible for a short period each year as any deviation from the normal date of visit may lead to a difference in numbers that could be misinterpreted as a real increase or decrease.

Equipment

From the following list depending on the methodology used (see Methodology section for details):

  • Map(s) of site(s) with compartments marked ensure the scale is sufficient to allow accurate recording of the plots and/or plants as applicable)
  • Recording forms and field guides
  • Metal pegs to mark plots in first year of recording
  • Metal detector to re-locate pegs in future years
  • Tape measure and/or length of string or cord

Methodology

Three methods are described. Plant Community Monitoring (Method 1) is designed to describe trends in the dominant and widespread species on a site. The other two methods (Mapping and Plane table methods) are designed to document individual rare or interesting species.

Method 1- Plant Community Monitoring (for dominant and widespread species on a site)

1: Before monitoring is attempted, the study area must be divided into plant communities and/or management compartments, each of which is visually uniform. Monitoring plots are located in each.

2: It is vital that the plots can be easily relocated in future years. This can be done by driving metal markers right into the ground, which can be found again with a metal detector. Plot location must also be written down, with appropriate sketch maps, etc. and deposited with the data from the plots, preferably in more than one place for security. On the first field visit the reverse of the recording form can be used for this information.

3: There must also be a way of navigating to the search area. Define a transect line across the habitat parcel with respect to landmarks, one of which at least must be on the site, to act as a zero-point for measured distances along the transect. Plots can be relocated along short transect lines with good precision without permanent markers, using a long tape measure or knotted cord.

4: Plots are located at regular intervals along the transect line (or random intervals if there is any suspected regularity in the compartment being sampled). Plots should be circular in short vegetation; it is easier to carry a single peg and measured cord than a square transect form. In taller vegetation, plots should be square, with one side along the transect line beginning at the defined point and placed in the direction of travel from there. The rest of the square is placed always to the left of the line.

5: Recommended plot size:

CommunitySquareRadius
Woodland canopy and shrub layers
Sparse scrub
50 x 50 m
Dense scrub
Tall woodland field layers
Species-poor herbaceous vegetation
10 x 10 m5.64 m
Short woodland field layers
Tall herbaceous vegetation
Heaths
Open vegetation
4 x 4 m2.26 m
Short herbaceous vegetation
Dwarf-shrub heaths
2 x 2 m1.13 m

6: Number of plots: At least three and preferably five plots should be placed in each parcel of habitat to be sampled. This may be increased if desired, as long as all parcels already have three to five plots, but it is vital to be able to maintain their monitoring in future years. About 12-15 plots can be documented daily.

7: Plot spacing: This should be chosen in advance, to ensure plots are spread more or less evenly along the transect line length.

8: Sampling: For linear vegetation the full width is sampled over a standard length: 10 metres for linear aquatic vegetation, walls and the field layer of hedges; 30 metres for the core of hedges. These lengths must be relocatable, their starting points being defined distances from a landmark on the linear feature.

9: Recording: The plot must be identified with a clear and unambiguous number and a very clear note should be made of the plot size and perimeter selected for each transect. On the first visit to the plot, notes should be made of its altitude, slope (in degrees), aspect, soil, geology and topography. On each visit notes may also be made on matters such as layering, zonation, succession, grazing, browsing, damage, disease, trampling, fire, use, management, etc.

Vegetation should be described on the attached standard recording form. Where there is much variation in the height of a single vegetation layer, this should be noted. Where there are distinct layers, a separate species list and cover/abundance record should be made for each layer, repeating species names as necessary. The total Domin values for a given layer may exceed 100%. Additional species in the stand, but not in the plot, can be recorded with a “ “. The cover of non-vegetated surfaces (bare ground, litter, rock, open water, etc) must also be recorded on the Domin scale. Although it is difficult to make visual assessments of cover abundance, and some species will lie near the cut-off points on the Domin scale, trends of interest will usually take several species more than one Domin point away from where they were. This reduces the effect of possible errors of the order of one point on the scale.

Each species on the plot is named and its cover/abundance given on the Domin scale, as follows:

  1. Few individuals <4% cover
  2. Several individuals <4% cover
  3. Many individuals <4% cover
  4. 4% cover to 10% cover
  5. 10% cover to 25% cover
  6. 25% cover to 33% cover
  7. 33% cover to 50% cover
  8. 50% cover to 75% cover
  9. 75% cover to 90% cover
  10. 90% cover to 100% cover

Data analysis can be undertaken by comparing the results with those from a previous year and is described in detail in the ‘Use of Collected Data’ section below.

Use of DAFOR scale as an alternative?

DAFOR: ‘dominant, abundant, frequent, occasional or rare – these classes have no strict definition and you must decide on your own interpretation. (Sutherland)

Method 2 – Mapping (unsuitable for routine monitoring of many species as this method is labour-intensive)

Mapping can be of individual plants, clones of rare plants, or of the edge of distribution of a larger patch of some species that may be expanding or contracting at its range. Mapping is most efficiently conducted by three people. One surveyor walks the site to hold a pole at each point to be plotted, whilst the other two stay at the end of a measured and relocatable base line, either holding one end of a surveyor’s tape or sighting on the pole from a plane table. With fewer people, temporary markers need to be placed at the points to be mapped, before measuring or sighting. These markers must be visually distinct from each other so that the measurements or sightings can be associated with a unique point.

Mapping with measured distances

The numbered crosses are at the points to be mapped (individual plants, clones or points along the border of a patch). The notes may record details on the status of each of the plants or clones, as well as information allowing them to be mapped. The base line AB is chosen to be relocatable in a similar way to the recommendation for the lines for plot sampling above. It is vital that the points A & B can be relocated with a high degree of precision in future years, and that the distance between them is measured. The method will be more precise to the extent that A & B are chosen so that the lines from them to the points intersect at angles near 90 degrees. Significant errors begin to emerge if any of the angles is below about 15 degrees or above about 175 degrees.

Mapping with measured distances

Measuring distances to points

The distance of each point to A (da) and to B (db) are measured. The points must be uniquely identified with this pair of distances in the notes to avoid ambiguity in the final map. The map is prepared by representing the line AB at an appropriate scale and drawing compass arcs from AB to represent the distances, at the same chosen scale. The points of intersection of the arcs are the map positions of the plants. It is convenient to represent tight groups of plants as single points on the map, and to annotate those points with the number of plants involved, otherwise the map becomes overcrowded.

Measuring distances to points 2

Method 3 – Plane table

This method requires a good line of sight from the points A & B to all the points and to each other. Where this is possible, the distances can be great. The details of positioning and the need to relocate the base line are the same as for measuring. The plane table itself is a flat surface mounted on a tripod, preferably one which can be tilted to match the slope of the survey area. This method is easiest with three people, in which case there needs to be two tables: one over each of points A and B. One table suffices where the points to mapped are marked. The table has a sheet of paper on it and a pin inserted near one corner, as illustrated. The pin is positioned over the baseline point on the ground. A ruler is placed with one edge against the pin and a sighting made along it to the other base point (eg to B if working at A) and to each of the points to be mapped. A line is drawn on the paper, along the edge of the ruler which touches the pin. These lines must be labelled according to the point they represent.

The map is prepared by representing the line AB at a chosen scale and at an appropriate position on a piece of paper. Then the lines drawn in the field are placed under this on a light-table, the pin hole positioned under the appropriate point (A or B) and the line corresponding to the other baseline point is positioned under the map base line. This allows the lines to be copied onto the map, and if needs be, extrapolated beyond the length drawn in the field. The points are mapped at the intersections of the corresponding lines.

The results of this monitoring enable either the fate of individual plants or clones to be followed, or enable documentation of the spread or decline of a large patch. It is important to realise in the former case that plants may not only die, but that new plants may be recruited to the population and that some individual plants may be much more conspicuous in some years than in others. The search each year should therefore be independent of the previous year’s results to avoid bias towards mortality and away from recruitment.

Next page – analysis of results from these methods