Stanley R. J. Woodell

The Ecology of Serpentine Soils

Publisher Summary The chapter provides details of the chemistry of the minerals frequently present in ultramafic rocks, and discusses the ecology of serpentine soil. Serpentine is used by biologists to describe a group of ultramafic rocks and the soils derived from them. Three principal polymorphic forms of serpentine are recognized: chrysotile, antigorite, and lizardite. The processes by which serpentine rocks develop into soils depend on climate, time, relief, and biotic factors along with the chemical composition of the parent material. As a result many types of soil occur on serpentines. The characteristics of serpentine are briefly discussed. Serpentine vegetation has two major characteristics: Physiognomic differences from the vegetation of surrounding rocks, and rare species and combinations of species. The vegetation of serpentines presents a wide range of appearances. Biologists have concentrated on the situations where serpentine vegetation is in sharp contrast with that of the surroundings. Such contrasts do not always occur and when this happens the serpentine vegetation is often not documented. The more closely studied serpentines have many vegetation features in common but the causes of these similarities can be very different. There is much scope for further work in many fields on serpentines.

THE EFFECT OF WATER ON POLLEN GERMINATION IN TWO SPECIES OF PRIMULA

of karyotypic variation in some insular Peromyscus from British Columbia, Canada. Cytologia 38:485-495. WAHRMAN, J., R. GOITEIN, AND E. NEVO. 1969. Evolutionary significance of chromosome variation. Science 164: 82-84. WEBSTER, T. P., W. P. HALL, AND E. E. WILLIAMS. 1972. Fission in the evolution of a lizard karyotype. Science 177:611-613. YOSIDA, T. H., AND K. TSUCHIYA. 1970. Segregation of three types of the largest No. 1 (A-I) chromosomes in Rattus rattus bred in a population room. Ann. Rep. Nat. Inst. Genet. Japan 20:9-10. YOSIDA, T. H., K. TSUCHIYA, AND K. MORIWAKI. 1971. Frequency of chromosome polymorphism in Rattus rattus collected in Japan. Chromosoma 33 :30-40.

Regeneration in the shrub Acacia burkittii FvM. ex Benth. in the arid zone of south Australia

Abstract A study of the age structure of several populations of Acacia burkittii at Middleback, South Australia shows that while some populations have not reproduced for 75 or more years, others are actively regenerating. The possible reasons for the differences are discussed. It is suggested that changes in management on the station, reduction of rabbit populations by myxomatosis, and rare high rainfall events may be responsible for the recommencement of successful regeneration in some populations. The future of this and other shrub species is discussed in the light of these results.

Giant tortoise and vegetation interactions on Aldabra atoll—Part 2: Coastal

Abstract Grazing by a large population of giant tortoises on Aldabra atoll in the western Indian Ocean may be linked to apparent changes taking place in the coastal grass and scrub lands. This paper presents a circumstantial case for the involvement of the tortoise population in a change from coastal, maritime, scrub-tussock vegetation to one of short, turf grassland.

Cape St Vincent and the Sagres Peninsula, Portugal: Important Biological Sites Under Threat

An account is given of the unique area comprising Cape St Vincent and the Sagres Peninsula, in southwestern Portugal. It has a variety of plant communities, some of which occur only in this area, and is the home of several endemic plant species. The two promontories are important breeding sites for several bird species, and are a landfall for thousands of migrating birds. Other animal groups of the area are less well-known. The area is subject to increasing visitor pressure, and tourist development is on the increase. The case is pressed for its conservation as a vital ecological resource, and as an asset to Portugal.