Specimen of Field-Label (5 in. by 8 in.). BOTANICAL SURVEY OF SOUTH AFRICA. Coll. No...... Habit and Size....... District.. Habitat... Frequency. Plant Community of Principal Associated Plants. Locality....... Alt... Date.... Economic or Biological Notes by..... Coll. by...... jo METHODS OF BOTANICAL SURVEY: SUGGESTIONS FOR THE BEGINNING OF THE WORK AND PROPOSED CONVENTIONAL SIGNS. By Professor J. W. BEWS. It is sufficiently obvious that we should take advantage of the work that has been done elsewhere, and each worker should be urged to make himself as well acquainted as possible with the increasing literature of the subject. Since there is, however, a certain danger of becoming too diffuse amid the rather bewildering details of a multitude of publications, the beginner will do well to confine himself to certain well-known works at the outset. Assuming that he has had the usual preliminary botanical training of our universities, he will already have learned the main facts that are necessary and a course of reading on the lines of the following works will give him the proper outlook : Warming, E..... "Plant Succession." "Plant Indicators." Types of British Vegetation." Tansley, A. G...... This should be followed by a study of the various South African ecological publications listed elsewhere. Other ecological papers will come to his notice from time to time. He should note any new ideas or general principles or methods of treatment and consider their applicability to South Africa. His greatest difficulty will soon appear to be not to find work to turn his hand to, but to decide which of the many useful and interesting problems should be tackled first. Some of those who have begun the study of plant ecology find it difficult to take a big view of natural phenomena and to grasp the general principles involved. To those who have devoted attention chiefly to minute studies in plant morphology or physiology, there sometimes comes a kind of mental myopia. It is literally true that they cannot see the wood for the trees. The ecologist tries to see both the wood and the trees, shrubs, herbs, climbers, and everything else that composes it. He has come to realize that any type of plant community, such as a forest, obeys certain laws. of development and passes through certain stages of growth which are in many ways analogous to the life-history of an individual plant. Ecology thus has much in common with the science of sociology. Many complaints are made concerning the system of nomenclature adopted by various ecologists. Similar complaints are levelled against the whole science of botany itself. We are constantly asked why plain English terms cannot be used instead of those derived from Latin or Greek, or, what is still worse, barbaric combinations of the two. The answer is that loose descriptive language without clearly defined terms leads to nebulous and confused thinking. Once a new idea or a new fact is clearly grasped, a proper term applied to it helps to fix it in one's mind. Words already in use for other ideas cannot very well be used, and besides it is convenient to have terms which tend to become international. In a young " science, such as ecology, some time must elapse before there is general agreement regarding the use of new terms. As our ideas become clearer, there is, however, a gradual approach to uniformity. The term "plant community is used in a perfectly general way for any assemblage of plants. The term "formation" is best restricted to the climax units of vegetation, i.e. the stable vegetation of an area where the factors of the habitat are more or less uniform, e.g. bush or forest, grassveld, scrub (sometimes), macchia, etc. If the plant community, as in the case of much of our eastern scrub, gives way in the course of time to another type, e.g. forest, then it is not climax and is not a "formation." The plant "" associations are the subordinate units dominated by two or more species which are associated regionally to constitute the formation, e.g. Podocarpus-Olea association in the forest formation. If there is a single dominant species the term "consociation" is used, e.g. Podocarpus falcata consociation in forest. If the vegetation type is not climax but represents merely a stage in the succession, the terms are altered to show this, e.g. Leucosidea-Buddleia " associes" or Leucosidea "consocies." (6 (( Smaller plant communities are designated by the terms "society if climax, or socies" if not climax. There are seasonal or aspect societies with local dominance (either "vernal," "aestival" or "autumnal") scattered through our grassveld, e.g. numerous species of Compositae. Leguminosae, bulbous plants, etc., and there are numerous "layer societies" in the forest. If the grassland is of a primitive kind, these scattered patches of associated plants form "socies" rather than "societies." The term "clan" is used by Clements for a still smaller (climax) unit, scattered and isolated. The term "colony" is used for small clumps of pioneer plants. Clements advocates the use of the term "sere" for a definite plant succession. A succession beginning in water is called a "hydrosere." There is a considerable degree of uniformity in its stages: (1) submerged aquatics, (2) floating aquatics, (3) reed stage (phragmites), (4) sedge stage (Cyperaceae), (5) vlei grasses, (6) hydrophilous trees and shrubs or moist grassveld, and (7) forest or grassveld. A succession beginning with bare land or rock is called a xerosere," and it leads on to the climax vegetation of each climatic region. The xerosere may be divided into the “lithosere ' for rock surfaces and the "psammosere" for sand. Note that both the "hydrosere" and the xerosere" tend to converge towards the same climax. 64 66 While ecology has many different aspects suited to different individual tastes, the beginner will do well to concentrate for a time on the study of habitats. The facts to be ascertained are so numerous that there is an imperative need of dealing with them in a systematic way. For the instrumental methods of investigating habitats, Clements' Research Methods" should be consulted. The subject is too big to enter on here. The plant collector, however, can do much to systematize the facts that come under his observation by working according to a well-defined scheme. The chief factors to be noted for each species are: (1) Nature of soil, both chemical and physical-sand, clay, loam, humous, calcareous. (2) Water. The gradations: very dry, dry, periodically wet and (3) Light.-Densely shaded, shady, diffuse light, full sunlight. (5) Other species of plants associated and their influence and relationships. (6) Occasionally other factors, e.g. wind-swept habitats, salt spray, etc. The following list of typical South African habitats is not to be considered exhaustive, but suggestive rather of the kind of detail that is wanted. In the primitive stages of the plant successions, the influence of other species is not so important. In climax stages the associated plants are of the utmost importance. 1. Smooth Bare Rock.- -Horizontal. 2. Smooth Bare Rock.-Sloping (give aspect, e.g. N.E.). 4. Cliffs.-Perpendicular or sloping (give aspect). (The geological 5. Rock Crevices.-Horizontal or vertical. Shallow or deep. Describe the soil if present, and other factors: (a) wet crevices, (b) dry crevices, (c) shady crevices, etc. 6. Rock Ledges.-Give depth and nature of soil and water and light as before. 7. Rock Flushes.-(Water-dipping crags.) State whether water is permanent or seasonally periodic. 8. Boulder Slopes.-Describe soil, water, and light. 9. Gravel Slopes.-Describe soil, water, and light, and give origin of the gravel and depth. Give the aspect. 10. Stony Patches.-Horizontal. II. Termites' Nests. 12. Sandy Patches.-Describe the sand and give the depth. 13. Rocky Seashore. 14. Sandy Seashore. 15. Sand Dunes.-Give full description of all the above factors and state whether dunes are "fixed" and covered with vegetation, or are nearly bare and mobile. 16. Blow-outs among Dunes.-Describe all the factors as before. 20. Quarries, etc. 21. Cultivated Land-Give the crop. 22. Fallow Land. State when it was ploughed last, if possible. 24. Ponds, Pools, Lakes.-Give size. Give depths of the water. "" 25. Vleis, Fresh Water.-Give particulars of degree of stagnation in 28. Mud Flats. 31. Warm Springs. 32. Sulphur Springs. 66 34. Flushes."-On hillsides below springs. 36. Rivers.-State the exact nature of river or stream bank, describing 37. Dongas. Give size and depth approximately and describe all the other factors. 38. Kloofs, Ravines. 39. Ant-bear Holes. The above are for the most part of a relatively primitive and unstable nature. In the more highly developed plant communities, the habitat has been influenced by the vegetation itself, and each species is definitely related to the other species growing with it. This relationship must be brought out in describing the habitat. In the larger sense the habitats are few in number, including : After naming the particular type the chief factors should again be noted soil, water, and light. The character of the surrounding species and, if possible, some of their names should be given. Where a species is being suppressed by others this should be carefully noted. It should be noted whether a species is marginal in the forest or not. Various layers should be distinguished--trees, under shrubs, under herbs, epiphytes, climbers. The following commonly accepted symbols may be used to denote frequency = a. 1.a. f. 1. 0. r. rare. v.r. very rare. After a beginning has been made with ecological collecting on these lines, the worker will probably find that his interest is attracted to the behaviour of certain definite species. He should always be on the outlook for cases of plants being suppressed by other plants, for this throws valuable light on the question of plant succession. In fact, wherever a species = = dominant. locally sub-dominant. locally abundant. local. |
0 Reviews Reviews aren't verified, but Google checks for and removes fake content when it's identified Write review |