Succession was monitored over ten years in a 10×10m plot in forest with mor humus at 1550 m in the Blue Mountains of Jamaica, following the removal in January 1975 of all aerial plant parts and some of the root material. In April 1977, August–January 1980/1 and August 1984, all woody recruits in the plot were tagged and numbered, identified and measured (height), and mapped on a 1 m grid. The height of coppice was recorded. Ten of the eleven tree species present before felling produced coppice shoots. Two individuals almost attained canopy height by 1984. Twenty tree species and three shrub species were recruited from seed; six of the tree species were normally absent from the forest. Species composition changed very little with time.

The rate of seedling recruitment was greatest immediately after clearing. The overall den-sity of individuals changed little after 1977. Overall mortality of recruits was about 10% per annum. Mortality of the earliest recruits declined with time since establishment. Later recruits and individuals with poor growth had higher mortality than other plants. Mortality was not density-dependent. Growth rates of recruits were relatively slow. Only ten individuals exceeded 4 m by 1984.

Recruitment rates, density, growth and species diversity were greatest in the parts of the plot where the mor humus had been removed or piled up during the initial clearance. Recruit-ment, growth and density were least, and mortality was greatest, at the edge. There was no relationship between any of these parameters and the presence of coppicing stumps.

Tree species showed a clear spectrum from obligate gap-demanders to obligate shade-bearers. The persistence of gap-demanding species in this forest (in which gaps are normally rare) may be due to infrequent hurricanes, and also to a natural ability to produce basal sprouts. The succession conforms to an initial floristic composition model; it is slow, and we suggest that at least 50 years will elapse before the plot begins to resemble the undisturbed forest.

I provide evidence that migrating birds concentrate in tropical second-growth woodlands due, in part, to a greater abundance of small fruits. Migrant birds markedly increased in abundance during spring migration in late March in a young (approximately 25 years old) second-growth woodland in Panama. Migrant abundance and diversity was greater at mist-net level on the second-growth site than in nearby old forest. Diversity of canopy migrants also was greater in the young woodland than in an old second-growth forest. Thus, many migrant species appear to select young second-growth during spring migration in central Panama. Degree of frugivory by many migrant species was greater during migration than earlier in the dry season. Most migrants selecting the second-growth site were highly frugivorous and migrants accounted for most of the visits to common fruit species, but use of fruit trees appeared to be influenced by fruit size relative to gape width. Most migrants have mouths that are better suited to eating the small fruits predominating in young forest than the larger fruits characteristic of old forest. Abundances of bird-dispersed fruit plants and, particularly, those fruit species known to be eaten by migrants were greater in young than in old forest. The high food demands of migrating birds added to the high degree of frugivory of most migrants selecting second-growth forest suggests that the abundance of small fruits in second-growth may be a strong cause for habitat selection during migration.

Seasonal variations in the breakdown and dynamics of chemical elements in Ficus fistulosa leaves in a mixed forest on Hong Kong Island were investigated between October 1982 and September 1983. Mean rate of leaf material weight loss from coarse-mesh (3 mm) bags was 1.82% day-1, about four times that inside fine-mesh (0.2 mm) bags (mean rate 0.44% day-1). Breakdown rates varied seasonally with maximum rates in spring or summer, and were significantly correlated with prevailing temperatures, the rainfall of the two previous months, and the soil moisture content of the previous month. Potassium and Mg were rapidly leached from leaf material throughout the year while the concentrations of C, N, P, Ca and Na remained relatively stable. In the absence of macrofauna (inside fine-mesh bags) decomposition rate constants (k) were positively correlated with the mean abundance of mites and Collembola, as well as with total invertebrate abundance. In the presence of macrofauna (inside coarse-mesh bags) decomposition rate constants were positively correlated with isopod and amphipod abundance. There was no significant correlation between breakdown rates of leaf material and mesofaunal abundance inside coarse-mesh bags. The importance of climate and invertebrates as rate determinants of Ficus decomposition is discussed.

Large areas of the Himalayas have become severely deforested although little has been published about the extent of this problem in the closed Kingdom of Bhutan. A preliminary survey was undertaken during 1983. Without detailed information or accurate maps, LANDSAT 2 imagery was used to prepare a sampling stratification and to plot the distribution of defined vegetation types after sampling and analysis. Eleven forest noda are described in relation to their habitats, and area and timber volume estimates given. Deforestation pressures are discussed.

A land use survey involving land typing and vegetation classification was conducted within the Luuq District Refugee Area (200,000 ha) in south-western Somalia. Average rainfall and annual temperature of the area are 310 mm and 30.5° C. The area is composed of limestone and basalt uplands, gypsiferous and alluvial interplains, and ancient and recent alluvial terraces of the Juba River.

Land types were identified by aerial photo survey and ground observation and mapped on a 1:100,000 scale LandSat Satellite (colour) Image. Soil types were classified according to the method used by the US Department of Agriculture, Soil Conservation Service. Vegetation was sampled according to the Braun-Blanquet approach in 52 releves located within previously mapped land types, and analysed using the traditional phytosociological methods and the DECORANA and TWINSPAN computer programs. The results of these methods are compatible with one another. Most community types identify distinct land types: basalt and limestone uplands, gypsum and alluvial interplains, and depressions and gentle rises of the Juba River terrace.

Commiphora and Acacia species dominate the open thorny bushland. They are mostly medium-sized shrubs and trees, 1 to 4 m in height. There is little herbaceous ground cover except in depressions and drainageways. Total shrub and tree cover averages 34%. Due to the large influx of refugees, there has been excessive cutting for fuelwood and construction material and notable bushland converted to cropland. Degradation of the vegetation and soils is prominent and is most evident on the upper and lower terraces of the Juba River.

In the absence of growth rings it is difficult to give a precise time scale for processes associated with the re-establishment of tropical rain forest. This paper explores other methods by which a time scale may be constructed. The proportions of primary and secondary species, an index of similarity, biomass measurements, girth dimensions and gap size are all considered from sites in East Kalimantan, Indonesia. Data from primary, secondary and experimentally cleared forest sites are compared to estimate the minimum time required for various phases involved in the re-establishment of tropical rain forest after disturbance. A simple model is proposed to accommodate the data and other estimates in the literature. The model predicts a minimum period for the stablization of secondary species numbers as 60–70 years and the replacement of primary species as 150 years at which point gap formation is initiated. After approximately 220–250 years biomass stabilizes while individual trees exist for over 500 years.

Production and nutrient content of small litterfall were studied for one year in four plantations of Agathis dammara ranging in age from 7 to 35 years old, in a 12-year-old stand of Pinus merkusii and in an approximately three-year-old shrub community dominated by Eupatorium species. The dense Pinus plantation produced considerably more litter (10 t/ha/yr, with 5.5 t/ha as needles) than any of the Agathis stands (2.6–6.2 t/ha/yr; 2.3–3.5 t/ha as leaves) or nearby Lower Montane Rain Forest (6.8 t/ha/yr; 5.4 t/ha as leaves). Litterfall in the Agathis forests increased with stand age. The shrubs produced sizeable amounts of litter (3.4 t/ha/yr). The various species responded differently to a drought occurring during the study period.

Pine litter generally exhibited low nutrient concentrations (on average 9.2, 1.9, 2.5, 0.4 and 6.0 mg/g of calcium, magnesium, potassium, phosphorus and nitrogen respectively in needle litter), whilst concentrations in shrub litter were generally high (37.8, 4.9, 1.4, 1.05 and 21.5 mg/g for the same elements); Agathis litter usually showed nutrient concentrations that were intermediate between those for pine or shrub litterfall with only minor differences between stands. Comparison of the present findings with observations at other tropical sites suggests that nutrient content of litterfall in plantation forests may approach that of natural forests when the former become about 20 years old. Pine plantations may constitute an exception in this regard.