Tropical Vegetation Types Research Articles

The Influence of Cyclones on the Dry Evergreen Forest of Sri Lanka

I assessed damage caused by a cyclone in November 1978 to a dry evergreen forest in Sri Lanka. Damage included defoliation, breakage of twigs, branches and trunks, tree fails and post-cyclone tree mortality. Within the 3 km2 study area there was a trend for increasing damage with forest height. Tree species in the upper forest layers had significantly more falls and post-cyclone mortality than trees in the more sheltered subcanopy and shrub layers. Mortality was significantly greater among trees which lost 40 percent or more of their branches and trunks than among trees with lesser crown damage. Defoliation and twig loss were extreme in the discontinuous upper layers and probably contributed to the greater tree mortality evident there. Overbrowsing by folivorous primates after the cydone may have contributed to the demise of some preferred feeding trees. Total tree loss was 46 percent from the upper forest layers, 29 percent from the subcanopy, or 40 percent from all tree layers. Five upper layer tree species were subject to tree losses of 80 to 100 percent representing a virtual elimination of 22 percent of species from the upper layers or 12 percent from the evergreen forest formerly covered 80 percent of the island's land area, and often has been described as old secondary climax in recognition of past disturbance. Extrapolations from meterological data indicate that 33 to 44 percent of the range of dry evergreen forest may be subject to cyclone damage per century. The species composition of dry evergreen forest on a local and wider geographical scale typically is fairly uniform in the subcanopy layer, but variable in the upper layers. I suggest that recurrent cyclone damage may be an important factor contributing to succession in dry evergreen forest and to the variation in species composition of the upper layers. TROPICAL CYCLONES OR HURRICANES are known to cause extensive damage to human life and property in the coastal regions of the Bay of Bengal in the Indian Ocean. Although natural plant and animal populations are also subject to cyclone damage, published reports addressing this phenomenon are rare and concern areas outside the Indian region (e.g., Webb 1958, Whitmore 1974). A recent cyclone which swept through the dry evergreen forest of Sri Lanka provided an opportunity to study the effects on phenology, forest structure and floristic composition. Quantitative data concerning these features were collected before the cyclone, allowing their comparison before and after the cyclone. The objectives of this paper are threefold: first, to assess the nature and extent of cyclone damage to the forest; second, to examine the causes of tree mortality in the 42 months following the cyclone; and third, to consider the effect of recurrent cyclones on the geographic variation in species composition of the dry evergreen forest of Sri Lanka. The long-term recovery of the forest from cyclone damage will not be examined in this report. Data concerning phenology are considered briefly, however, in order to show the immediate effects of the cyclone. NOMENCLATURE AND NATURAL HISTORY The forest types of Sri Lanka have been classified according to several schemes (e.g., Chapman 1947; Holmes 1956; Koelmeyer 1957, 1958; Gaussen et al. 1964; Fernando 1968). Mueller-Dombois (1968) offers an evaluation of these schemes and additional refinements have been made recently by Greller and Balasubramaniam (1980) and Greller et al. (1980). The forest type considered here is commonly known in Sri Lanka as the forest. It has also been referred to as Evergreen Forest (Champion 1935, Chapman 1947, Holmes 1956), Mixed Evergreen Forest (de Rosayro 1950; Koelmeyer 1957, 1958; Andrews 1961), Semideciduous Forest (Gaussen et al. 1964, 1965), South Tropical Moist Deciduous Forest (Chapman 1947, Koelmeyer 1957), Lowland Seasonal Rain Forest (Perera 1975) and Semi-evergreen Forest (Dittus 1977). The last label had been selected to conform to Walter's (1971) worldwide classification of tropical vegetation types, although Walter does not specifically refer to the dry-zone forest of Sri Lanka. In the literature the dry-zone forest is most frequently referred to as Dry Evergreen Forest and therefore I will follow this tradition here. Taxonomic nomenclature follows Abeywick-rama (1959) and Dassanayake and Fosberg (1981, 1983). I Received 2 August 1983, revised 11 May 1984, accepted 14 June 1984. 2 Field address: Smithsonian Institution Primate Project, 4/4 Galkanda Road, Anniewatte, Kandy, Sri Lanka. BIOTROPICA 17(1): 1-14 1985 1 This content downloaded from 207.46.13.127 on Wed, 12 Oct 2016 04:32:28 UTC All use subject to http://about.jstor.org/terms

Inheritance of Color Phases of Ferruginous Hawks

BEARD, J. S. 1955. The classification of tropical American vegetation types. Ecology 36:89-100. CONOVER, W. J. 1971. Practical nonparametric statistics. Wiley, New York. DIAMOND, J. M., AND J. W. TERBORGH. 1967. Observations on bird distribution and feeding assemblages along the Rio Callaria, Department of Loreto, Peru. Wilson Bull. 79:273-282. KANTAK, G. E. 1979. Observations on some fruit-eating birds in Mexico. Auk 96:183-186. LAND, H. C. 1963. A tropical feeding tree. Wilson Bull. 75:199-200. LECK, C. F. 1969. Observations of birds exploiting a Central American fruit tree. Wilson Bull. 81:264269. LECK, C. F. 1971. Overlap in the diet of some neotropical birds. Living Bird 10:89-106. LECK, C. F. 1972. Seasonal changes in feeding pressures of fruitand nectar-eating birds in Panama. Condor 74:54-60. LECK, C. F., AND S. HILTY. 1968. A feeding congregation of local and migratory birds in the mountains of Panama. Bird-Banding 39:318. MORTON, E. S. 1973. On the evolutionary advantages and disadvantages of fruit eating in tropical birds. Am. Nat. 107:8-22. PAYNTER, R. A., JR. 1955. The ornithogeography of the Yucatan Peninsula. Peabody Museum of Natural History, Yale University, New Haven, CT. PIANKA, E. R. 1969. Sympatry of desert lizards (Ctenotus) in western Australia. Ecology 50:1012-1030. SCHOENER, T. W. 1971. Theory of feeding strategies. Annu. Rev. Ecol. Syst. 2:369-404. SCHOENER, T. W. 1974a. Resource partitioning in ecological communities. Science 185:27-38. SCHOENER, T. W. 1974b. The compression hypothesis and temporal resource partitioning. Proc. Natl. Acad. Sci. 61:4169-4172. SHEPHERD, J. D. 1975. The phytosociology of a tropical seasonal forest in southeastern Mexico. M.S. thesis, Univ. of Wisconsin, Madison. SNow, B. K., AND D. W. SNow. 1971. The feeding ecology of tanagers and honeycreepers in Trinidad. Auk 88:291-322. TERBORGH, J. W., AND J. M. DIAMOND. 1970. Niche overlap in feeding assemblages of New Guinea birds. Wilson Bull. 82:29-52. WILLIS, E. O. 1966. Competitive exclusion and birds at fruiting trees in western Colombia. Auk 83:479480.

Soil Respiration of Tropical Vegetation types

Soil respiration rates, measured during the dry season of 1966 in Costa Rica by absorption of CO2 through KOH followed by titration with HCI, were lowest in the savanna and the decidous forest (300—400 mg CO2/m2/hr); they were between 1,000 and 2,000 mg CO:2/m2/hr in the gallery forest and the wet forest; and were highest in the secondary growth vegetation (2,556 mg CO2/m2/hr). The results were related to the climatic conditions in these habitats. The climate limits the development of organisms in the soil and the primary production in the vegetation. Comparisons of European, Canadian, and tropical soil respiration rates show the limitation of soil respiration through limitations of primary productivity.

The Recording of Structure, Life Form and Flora of Tropical Forest Communities as a Basis for Their Classification

AT the Annual Meeting of the British Ecological Society in January 1938, Dr J. Burtt Davy read a paper on classification of tropical woody vegetation with the object of obtaining constructive criticism from the Society. As a result of the discussion which followed, a committee of three (the authors of the present paper) was appointed to examine and report on the subject. The Committee carefully considered Dr Burtt Davy's paper published, under the title mentioned, by the Imperial Forestry Institute as Institute Paper No. 13, Oxford, 1938, and duly reported to the Council of the Society. At a recent meeting this Report was approved and adopted by Council, which accepted an invitation to publish it, with appropriate modifications, as an Imperial Forestry Institute Paper' and ordered that it should also appear in The Journal of Ecology. The present paper contains the substance of the Committee's Report. Most of it is unaltered, but the introductory portion has been rewritten for publication. There is an urgent demand for stabilization of the nomenclature of tropical forest vegetation, on the part of Conservators and other Forest Officers, in order to avoid t,he confusion and misunderstanding that result from different officers calling the same things by different names and possibly different things by the same name. Dr Burtt Davy's essay on the classification of tropical woody vegetation types, above referred to, is a praiseworthy effort to meet this need. But it must be recognized that a natural classification of any set of phenomena can only be made when our acquaintance with the facts on which a classification can be based has reached a fair degree of completeness. In the present inadequLate state of our knowledge of tropical woody communities no classification can be other than provisional, and Dr Burtt Davy claims no more for his effort. The authors certainly do not possess knowledge that would enable them to replace it by anything which they would consider a satisfactory classification, nor can such knowledge be obtained from existing publications. The use of mixed criteria, largely but not wholly based on habitatwetness and dryness, evergreen and deciduous habit, stature and life form, altitude, and sometimes the systematic position of dominants-must lead to