A unique stand of mangroves of the genus Bruguiera occurs on the shore terrace at Hosnies Spring, Christmas Island, Indian Ocean. The mangrove stand, of about 0.33 ha, occurs 120 m inland and over an elevational range of 13 m, from 24 to 37 m above sea level. It is flooded by freshwater from a spring which trickles over a partially-cemented calcsinter concretion gravel with mud. Trees reach 30–40 m high, and 80 cm diameter breast height. The size structure is bimodal with few trees in the 10–25 cm dbh size classes, but abundant propagules, seedlings and saplings. The shore terrace contains corals, some in their position of growth, and has been shown by Uranium-series dating to be Last Interglacial in age. Several alternative explanations of how the mangroves reached this site are examined. One explanation is that this stand of mangroves has persisted at the site for approximately 120,000 years since the Last Interglacial. While this cannot be proved it does appear that the stand is relict and is actively regenerating in this unusual location.

Abundance and density data for terrestrial arthropods from the forest floor, trunk and canopy of primary and secondary dryland forests near Manaus, Brazil are given.

Litterfall was measured monthly in ten 1 m2 traps in each of two 0.25 ha plots in the rain forest of Southern Bakundu Forest Reserve, Cameroon for 18 months from 1 July 1982 to 31 December 1983. Particular emphasis was placed on measuring species contributions and in relating litterfall to climatic factors; the litterfall data were also used in estimating leaf production. Annual litterfall ranged between 12.9 and 14.1 t ha−1 and was partitioned to leaves (61–66%), branches (23–38%), fruits and flowers (8–12%) and ephiphytes (0.8%). Emergents and top canopy species like Desbordesia glaucescens (evergreen) and Ceiba pentandra (deciduous) contributed more litter than the numerically dominant lower storey species like Cola lepidota and Diospyros spp. Litter fell throughout the year but was greatest during the dry season (November to March); litterfall was thus strongly negatively correlated with environmental moisture variables and could be predicted from its linear regression on time of year, throughfall and relative humidity. By correcting the leaf fall data for leaf weight losses due to grazing and re-translocation, leaf production rates of 10.2 to 11.2 t ha−1 yr−1 were estimated for the forest.

Earthworm populations in grassland and plantations in the area of Bulolo, Papua New Guinea were compared with populations in nearby undisturbed rain forest. The grasslands had been maintained by burning for many years. The Pinus plantation had been developed on a burned grassland site and the Araucaria plantation on a site which had been cleared of secondary forest.

The grasslands and the Pinus plantation supported moderate populations of exotic earthworms including Pontoscolex corethrurus, but no indigenous species. The Araucaria site supported a native species, Amynthas zebrus only, which was also found together with two other native species at very low density in rain forest.

Exotic earthworm species widespread throughout the tropics, were present in disturbed soils and formed moderately high density populations in burned grasslands. There was no evidence that they displaced native Megascolecidae in rain forest.

Fish communities of a fourth order stream impounded by a weir were studied in Southern Nigeria. Fifty-eight species were recorded of which 90% occurred upstream while reservoir and downstream accounted for 48% and 43% respectively. The distribution of some fish families indicated the effects of habitat alterations caused by reservoir and downstream conditions. The fauna upstream was different from that of reservoir and downstream. Relative abundance of non-cichlids common to reservoir and downstream showed 42% similarity. The longitudinal distribution of three non-cichlid populations was different in reservoir and downstream. Non-cichlid species richness was almost similar in reservoir and downstream, but its general diversity and evenness were higher in reservoir than its downstream. Fish community changes in this stream are discussed.

An investigation into the causes of massive destruction of the vegetation around Tsekelewu Oil Field in the Niger Delta was carried out. The 200 km2 area suffering varying degrees of damage was mapped and the damage quantified by photo interpretation of black and white aerial photographs. Soil, surface and ground water samples were taken from the various zones for chemical analyses which included the determination of pH, electrical conductivity and soluble salt analysis.

The results showed that salt accumulation decreased from the sea inland-wards, with some upsurge in the saline-fresh water transitional zone where the greatest damage occurred. The electrical conductivity of the ground water varied from 45 dS m−1 in the area of greatest damage to less than 4 dS m−1 in the fresh water zone where there was no apparent damage. The salt-tolerant species along the coast were not affected, but in the transitional saline-fresh water zone in which the electrical conductivity of ground water was greater than 30 dS m−1, all the vegetation including the relatively salt-tolerant white mangrove (Avicennia africana) were killed. This destruction is attributed to high salinity caused by salt water incursion from the sea.

An attempt was made to evaluate the consequences of applying a strict definition (Brokaw 1982a) to the delimitation of forest gaps in the field. The northernmost Neotropical rain forest, at Los Tuxtlas, Mexico, was searched for young (1–2 years old) single-event gaps that would meet the criteria of the definition. In 60 ha of rain forest, only 12 such gaps containing pioneer species could be found. Thirty-three pioneer species (shrubs and trees) were used as indicator species for gap conditions. Gap size, measured as projected canopy opening (sensu Brokaw 1982a), underestimated from 44 to 515% the size of the area colonized by pioneer species. On average the size of the colonized area was 3.4 times larger than the size of the projected canopy opening. The majority of the pioneer species showed a relative preference for gap borders, an area generally not included in the projected canopy opening. Pioneer plant abundance and density, and species richness and density, did not differ significantly between gap centres and gap borders. Floristical variation was not related to gap size or location in the gap. These findings can be explained if gap environment (to which pioneer plants respond) is seen as the result of many interacting factors, of which size of the canopy opening is only one. It is concluded that the definition for delimiting gaps in the field as proposed by Brokaw (1982a) cannot be regarded a generally applicable definition, and that its value as a comparative standard is doubtful.