The RAINFOR database: monitoring forest biomass and dynamics

Problem: Data from over 100 permanent sample plots which have been studied for 10–20 years need a suitable system for storage which allows simple data manipulation and retrieval for analysis. Methods: A relational database linking tree records, taxonomic nomenclature and corresponding environmental data has been built in MS Access as part of the RAINFOR project. Conclusion: The database allows flexible and long‐term use of a large amount of data: more than 100 tree plots across Amazonia, incorporating over 80 000 records of individual trees and over 300 000 total records of tree diameter measurements from successive censuses. The database is designed to enable linkages to existing soil, floristic or plant‐trait databases. This database will be a useful tool for exploring the impact of environmental factors on forest structure and dynamics at local to continental scales, and long term changes in forest ecology. As an early example of its potential, we explore the impact of different methodological assumptions on estimates of tropical forest biomass and carbon storage.     

Does Weeding Promote Regeneration of an Indigenous Tree Community in Felled Pine Plantations in Uganda?

The use of plantations to manage extensive tracks of deforested lands in the tropics is a conservation strategy that has recently received considerable attention. Plantation trees can promote seed dispersal by attracting dispersers and creating favorable site conditions, leading to increased germination and establishment of indigenous trees. Subsequently, plantation trees can be harvested for profit or left to senesce, leaving a native tree community. We evaluated the effect of vine, grass, and shrub cutting (weeding) over a 3‐year period on regeneration of indigenous trees subsequent to the removal of plantation softwoods in Kibale National Park, Uganda. Counter to what would be expected if weeding released trees from competition, we found no difference in the total number of stems or in the stems greater than 10 cm diameter at breast height between control and weeded plots; there were more stems greater than 1 cm diameter at breast height in the control plots. For species found in both control and weeded plots, the maximum size of individuals did not differ. At the end of the study, 61 species were found in the control plots and 43 species were found in the weeded plots, and in both types of plots the three most abundant species were the same. The number of species and stems classified as early or middle successional species did not differ between weeded and control plots. The fact that weeding did not promote regeneration of indigenous trees after the removal of plantation trees illustrates the importance of evaluating and field‐testing potential management options.     

A New Species of Poorly Known Mayfly Genus Paegniodes Eaton (Ephemeroptera: Heptageniidae) from Vietnam

A heptageniid mayfly species Paegniodes dao sp. nov. (Ephemeroptera: Heptageniidae) is described from Vietnam. The larva is distinguished by round anterolateral margins of pronotum, triangular‐shaped labrum, rudimentary lamella and well developed fibrillae of gills 1, and light brown body that lacks distinct markings. Diagnosis, line drawings, material, and habitat data are provided.     

Some factors affecting the composition of tropical ichneumonid faunas

An increasing accumulation of data shows that tropical ichneumonid faunas are no more species-rich than extra-tropical ones, despite the fact that most of their host groups show increased tropical species-richness. This lack of increase in ichneumonid species-richness can be attributed to the absence of groups whose hosts are not present (e.g. Ctenopelmatinae) and poor tropical representation by many groups of diurnal koinobionts (e.g. Campopleginae). Low host density has been postulated as a barrier to tropical koinobiont species-richness, but it is here suggested that this is not the only limiting factor as groups of nocturnal koinobionts, such as the Ophioninae, show increased tropical species-richness. It is postulated that koinobionts have the capability of being able to locate sparse hosts, but as they host-search in flight, a prolonged daytime host-searching period in the tropics would expose them to a high level of predation pressure. By being active at night koinobionts can avoid diurnally active predators. It is also postulated that sparse hosts may be located more easily at night and more habitats may be climatically suitable for ichneumonid activity when they are not subject to direct sunlight. Idiobionts, such as the Mesostenini and Pimplini, are more species-rich and morphologically diverse in the tropics than they are in extra-tropical regions. It is suggested that this results from the fact that tropical idiobionts can be active during the whole of the diapausing period, when their hosts are available, whereas activity by temperate idiobionts is prevented by inclement weather. Although many idiobionts are probably less exposed to predators than koinobionts, many have evolved obvious protective devices.     

Altitudinal changes in the incidence of crassulacean acid metabolism in vascular epiphytes and related life forms in Papua New Guinea

Summary The occurrence of Crassulacean acid metabolism (CAM), as judged from ¹³C values, was investigated in epiphytes and some related plant species at a series of sites covering the approximate altitudinal range of epiphytes in Papua New Guinea. Comprehensive collections were made at each site and the occurrence of water storage tissue and blade thickness was also determined. Some 26% of epiphytic orchids from a lowland rainforest (2–300 m.a.s.l) showed ¹³C values typical of obligate CAM and possessed leaves thicker than 1 mm. A second group of orchids, mostly with succulent leaves, possessed intermediate ¹³C values between -23 and -26% and accounted for 25% of the total species number. Some species of this group may exhibit weak CAM or be facultative CAM plants. The remainder of the lowland rainforest species appeared to be C₃ plants with ¹³C values between -28 and -35%. and generally possessed thin leaves. Obligate CAM species of orchids from a lower montane rainforest (1175 m.a.s.l) comprised 26% of the species total and mostly possessed thick leaves. The remainder of the species were generally thin-leaved with ¹³C values between -26 and -35%. largely indicative of C₃ photosynthesis. Orchids with intermediate ¹³C values were not found in the lower montane rainforest. Obligate CAM appeared to be lacking in highland epiphytes from an upper montane rainforest and subalpine rainforest (2600–3600 m.a.s.l). However the fern, Microsorium cromwellii had a ¹³C value of -21.28%. suggesting some measure of CAM activity. Other highland ferns and orchids showed more negative °¹³C values, up to-33%., typical of C₃ photosynthesis. The highland epiphytic orchids possessed a greater mean leaf thickness than their lowland C₃ counterparts due to the frequent occurrence of water storage tissue located on the adaxial side of the leaf. It is suggested that low daytime temperatures in the highland microhabitats is a major factor in explaining the absence of CAM. The increased frequency of water storage tissue in highland epiphytes may be an adaptation to periodic water stress events in the dry season and/or an adaptation to increased levels of UV light in the tropicalpine environment.     

Leaf water relations and anatomy of a tropical rainforest tree species vary with crown position

Summary Leaf water potentials, osmotic properties and structural characteristics were examined in the Australian tropical rainforest tree species, Castanospermum australe. These features were compared for individuals growing in the understorey and canopy of the undisturbed forest and in an open pasture from which the forest had been cleared. Leaf water potentials during the day declined to significantly lower values in the open-grown and canopy trees than in the understorey trees. During most of the day the opengrown tree experienced the lowest water potentials. These differences were paralleled by significant differences in tissue osmotic properties. The tissue osmotic potential at full hydration was lowest in the open-grown tree (-1.80 MPa), intermediate in the canopy trees (-1.38 MPa), and highest in the understorey trees (-0.80 MPa). As a result, the degree to which high and positive turgor pressures were maintained as water potentials declined was highest in the open-grown tree, intermediate in the canopy trees, and lowest in the understorey trees. The differences in tissue osmotic properties between individuals in the three crown positions were paralleled, in turn, by differences in leaf structual characteristics. Relative to leaves of the canopy and open-grown trees, leaves of the understorey trees had significantly larger epidermal cells with thinner cell walls, larger specific leaf areas and turgid weight: dry weight ratios, and a higher proportion of intercellular air space.Abbreviations ₁ Leaf tissue water potential - _min Lowest value of ₁ during the day ( noon) - _{P=0 1} zero turgor - R Relative water content - P Tissue turgor pressure - Tissue osmotic potential - ₀ at full hydration     

Growth responses of tropical forage plant species to vesicular-arbuscular mycorrhizae

Summary Growth and mineral uptake of twenty-four tropical forage legumes and grasses were compared under glasshouse conditions in a sterile low P oxisol, one part inoculated and the other not inoculated with mycorrhizal fungi. Shoot and root dry weights and total uptake of P, N, K, Ca, and Mg of all the test plants were significantly increased by mycorrhizal inoculation. Mycorrhizal inoculation, with few exceptions, decreased the root/shoot ratio. Non-mycorrhizal plants contained always lower quantities of mineral elements than mycorrhizal plants. Plant species showed differences in percentage mycorrhizal root length and there was no correlation between percentage mycorrhizal infection and plant growth parameters. A great variation in dependence on mycorrhiza was observed among forage species. Total uptake of all elements by non-mycorrhizal legumes and uptake of P, N and K by non-mycorrhizal grasses correlated inversely with mycorrhizal dependency. Mycorrhizal plants of all species used significantly greater quantities of soil P than the nonmycorrhizal plants. Utilization of soil P by non-mycorrhizal plants was correlated inversely with mycorrhizal dependency.     

Tree form in a mixed dipterocarp forest in Indonesian Borneo

The form of tropical trees was studied with reference to the production structure of the component individuals of a tropical rain forest stand in Sebulu, East Kalimantan in Indonesian Borneo, since the production structure as a physical or bio-economical basis of tree form still remains obscure in tropical rain forests. The pipe model theory successfully explained the crown shapes of different trees, and its parameter, designated as specific pipe length, suggested an increase in the cost of leaf mass growth with an increase in crown size. A mathematical model consisting of exponential functions of aboveground height was applied for describing stem form, and its properties were examined through changes in its coefficients and by adopting an assumption of the geometrical similarity of individual stem form as a criterion for comparing differences in stem form among individual trees. Furthermore, the cost of buttersses was discussed using the relation between bole- and buttress weight calculated from the mathematical model.