This section is from the book "British Wild Flowers - In Their Natural Haunts Vol2-4", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
(a) The Field Itself. - The author has recently had to undertake the survey of a particular district upon ecological lines, and has found that the introduction of a novel plan of work has been the most productive of results, and is adapted to all classes of workers.
In this system fields are studied one by one. An Ordnance map of the district is procured, and upon this the fields are numbered. In the field the plant-lists bear the same numbers as those given to the fields on the map.
The plan adopted is to make a general survey of the field by considering the abundance or dominance of the Grasses in the first place. The one which is most dominant is put down first in the list, and the percentage may be stated in relation to that of other Grasses. Then the next most common Grass is put down second, and the others in their order, and so on. In a dry field one may have an abundance (75 per cent) of Yellow Oat Grass or Sheep's Fescue; in a wet meadow Tussock Grass may locally be dominant. As meadows are artificial enclosures, the dominance or frequency in one has to be contrasted and checked by that of other fields. (The terms used are abundant, locally abundant, frequent, occasional, rare.)
After the Grasses have been put down, the rest of the plants are noted in order of abundance or by frequency or percentage. When a detailed survey is required, a plot is staked out in squares, and every plant is noted and mapped on squared paper.
The examination of the ditches surrounding a field may come next. These are likewise artificial, but may indicate in connection with the type of water (hard or soft) the character of the natural aquatic vegetation from which they are derived. The ditch is rather too small to treat in the same way as a river or stream, and to show the zonal arrangement or riparial vegetation, floating plants, submerged plants, etc. But where these different types or others (on the basis of Nymphaea, Hippuris, Hydrocharis types, etc.) occur they should be noted. It is as well, if this can be done, to note the absence or presence of Algae Liverworts, or Mosses (the last on banks usually), as these also throw a light upon the vegetation.
All ditches do not contain water all the year round, and this should also be stated. Some ditches are perennially dry, and many are filled with thorns cut from a layered hedge. The fact that a ditch has been just cleared out should be noted, and it is important to compare the new flora of such a ditch with the result of a former examination. The seedlings that come up will not all live, but all should be observed and put down in the memoranda on the spot. Where bridges and culverts exist, these should be examined. Many lichens grow on the stones or brickwork.
The hedge forms an artificial barrier to the field or division between two ditches and contiguous fields. It serves two purposes in the main apart from the use it has as a boundary: (1) it acts as a barrier to dispersal of seeds, and thistle down will not travel beyond it usually, hence the affinity of some thistles for the hedgerow; (2) it serves, as pointed out already, as a retreat for the shade-loving plants; and we may add (3) it forms a line of distribution by aid of birds, etc, for the dispersal of seeds carried by such agency from one point to another. The hedgerow is thus an important factor in botanical work in the meadow.
The method of survey may be carried out as for woods. The trees, which are mainly planted like the hedgerow, should be noticed in order of frequency. Their influence upon the plants covered by their overshadowing branches should be noted. It is often very marked. The lichen and moss flora upon such trees may be studied by advanced pupils, and the several aspects taken up by each noted. The hedgerow plants may then be noted in the same way. The direction of the hedgerows, as in the case of the ditches, should be stated.
Then the ground flora beneath should be noted, as in the case of the plants in the open field, the frequency estimated, and the plants on the different sides should be distinguished. Where the hedge bank has no ditch its flora will differ from that of a ditch bank.
Climbing plants should be put down separately, and a distinction drawn between the trailing plants in the hedge bottom and the erect types.
In many if not most fields there are one or more ponds. These isolated tracts of aquatic vegetation should be studied separately, though as parts of the meadow flora. They are often artificial, but some are natural pools adapted to agricultural purposes.
The plants growing on the banks may be noted first. Then the vegetation around the margin, such as Sedges growing in the water, but sending up erect stems and leaves. Occasionally in large pools there are patches of Reed-mace and Reeds, forming a further type or reed swamp. The floating plants may be studied by themselves, then the submerged and half-submerged types.
The pupil should be on the lookout for such rare plants as Hydrocharis or Frogbit, or others that give the pool or pond a special character.
As in the case of ditches, the presence or absence of Algae and other Cryptogams should be noticed if possible.
See also Section VIII (Vol. IV).