Large Canopy Trees Research Articles

Exarata (Bignoniaceae), a New Genus from the Choco Region of Ecuador and Colombia

Exarata is proposed as a new genus for a new species of Bignoniaceae from the Choc6 region of western Colombia and northwestern Ecuador, here described as E. chocoensis. Exarata is morphologically similar to Schlegelia by its globose indehiscent fruit, but is a large canopy tree. This taxon may be near the basal complex from which tribes Schlegelieae and Tecomeae diverged.

Simulation and future projection of succession in a Swedish broad-leaved forest

The forest succession model FORSKA was used to simulate the dynamics of stand composition and structure in Dalby Söderskog, a southern Swedish broad-leaved forest. The development of Dalby Söderskog has been monitored since the area became a national park in 1916. The model was run with the seven species found in the forest today. Species parameters were estimated from silvicultural data. A first non-initialized model run generated size distributions similar to those observed, but the numbers of the dominant species were different; beech, in particular, was too abundant. A second run, initialized to resemble the forest as it was in 1920, generated size distributions and species abundances in good agreement with observations. The known course of succession since 1930 was also correctly simulated. Today, beech is dominant in a small part of the forest; elsewhere elm is the most abundant tree, with some scattered individuals of ash and oak. Simulated future trends indicate that this forest composition is fairly stable, but that oak will likely decline. Maple, hazel and hawthorn are present in small quantities throughout the simulations; their numbers increase when large canopy trees die, implying that gap phase dynamics is important in determining the composition of this forest.

Patterns of Insect Herbivory, Growth, and Survivorship in Juveniles of a Neotropical Liana

Patterns of insect herbivory, growth, and survivorship were studied for 3 yr in the shade—tolerant liana Connarus turczaninowii. The percent damage to young leaves (°2 mo) ranged from 2.9% in 1981 to 7.5% in the census following an El Nino event (January 1984). Although the median leaflet lifetime was 2.5 yr, °33% of the lifetime damage by herbivores occurred during the first 2 mo. Annual rates of insect damage to mature leaves varied from 2.8% in 1982 to 6.0% in 1984. The most common herbivore observed on mature leaves was the beetle Demotispa sp. nov. The proportion and actual quantity of damage by this species was minimal on young leaves, but increased with leaf age. Compared with leaves in extremely low light, leaves from plants in extremely high light had lower concentrations of water and nitrogen, and more condensed tannins. Leaves from high light environments were also tougher. Although these charateristics have been shown to affect host choice or feeding in other species, no differences in rates of insect damage were detected among plants that occurred across a continuum of light environments. Plant growth increased with canopy openness, and, in one year, decreased with an increase in insect herbivory. Even though damage rates were high folowing El Nino, growth was high. We hypothesize that juvenile growth responded positively to the duration of the previous dry season because of increased light in the understory and a decrease in water loss from the soil due to the increased level of deciduousness of large canopy trees.

Genetics of Brazil nut (Bertholletia excelsa Humb. & Bonpl.: Lecythidaceae)

We provide an estimate of genetic variation within and between two populations of Bertholletia excelsa (Brazil nut), a large canopy tree found in the rain forests of South America. Average heterozygosity is 0.190, and 54.3% of the sampled loci are polymorphic. The population structure deviates significantly from Hardy-Weinberg expectations for Fest2 and Pgm2 (F =0.405 and 0.443, respectively) in one population, and highly significantly (F=-0.341) for Gdh in the other population. Although allele frequencies of the two populations differ significantly for Aat2, Est5, Mdh1, and Mdh2B, Nei's coefficient of gene differentiation (Gst) indicates that the between-population component (Dst) of genic diversity represents only 3.75% of the size of the within-population component (Hs). The implications of these findings in terms of conservation genetics are that much of the genetic diversity of this species may be preserved within one or a few populations. However, such populations must be very large because it appears that the large amount of genetic variation in Brazil nut populations is maintained by extensive gene flow and bonds of mating over a large area. The genetic architecture of Bertholletia excelsa is similar to that expected for an extensively diploidized paleopolyploid species.

The structure and phenology of a moist deciduous forest in the Central Indian Highlands

The vegetation structure and phenology of a 74.5 ha block of moist deeiduous forest in Kanha Tiger Reserve, Madhya Pradesh, India were investigated during primatological fieldwork. Within a grid of 0.25 ha quadrats all 9935 trees (woody plants > 2 m tall), of 63 species, were enumerated and their girth measured. The forest was dominated by the dipterocarp sal (Shorea robusta). Most species were rare and showed clumped distributions within the ‘sea’ of sal whilst the dispersion of five large canopy trees could not be distinguished from random. The phenology of 215 trees, of 61 species, was monitored over 14 months using an index of phytophase abundance. Leaf renewal was highly synchronous between and within species, mostly occurring between February and June. One species was evergreen, 5 were semi-evergreen and 55 were deciduous. Flowering generally occurred between leaf fall and flush whilst fruiting peaked late in the hot weather and early monsoon.

MATING SYSTEM OF A TROPICAL RAIN FOREST TREE SPECIES

Canopy tree species are the dominant elements of the species‐rich, fragile and endangered tropical rain forest ecosystems, yet little is known about the genetics of these species. We provide an estimate of the outcrossing rate in a population of Pithecellobium pedicellare, a large canopy tree in the tropical rain forests of Costa Rica. The outcrossing rate was high (t = 951 ± 0.021) and the pollen pool contributing to the progeny arrays used to measure outcrossing rate showed departure from homogeneity. The high outcrossing rate indicates that individuals scattered over a large area in this low density population could be bound with each other via outcrossing. However, despite a high outcrossing rate, the potential for inbreeding in this population is not negligible. We found a relatively large number of albino and chlorotic seedlings among the progeny arrays of several seed parents. Heterogeneity of pollen pool further indicates that the population, though widely outcrossed, may be structured. A more detailed study of mating systems in tropical rain forest trees may provide additional insights into the mating patterns of these trees. Such studies will be useful not only in understanding the dynamics of micro‐evolutionary processes, but also in the conservation and management of tropical forest trees.

Mating System of a Tropical Rain Forest Tree Species

Canopy tree species are the dominant elements of the species-rich, fragile and endangered tropical rain forest ecosystems, yet little is known about the genetics of these species. We provide an estimate of the outcrossing rate in a population of Pithecellobium pedicellare, a large canopy tree in the tropical rain forests of Costa Rica. The outcrossing rate was high (t = 951 ± 0.021) and the pollen pool contributing to the progeny arrays used to measure outcrossing rate showed departure from homogeneity. The high outcrossing rate indicates that individuals scattered over a large area in this low density population could be bound with each other via outcrossing. However, despite a high outcrossing rate, the potential for inbreeding in this population is not negligible. We found a relatively large number of albino and chlorotic seedlings among the progeny arrays of several seed parents. Heterogeneity of pollen pool further indicates that the population, though widely outcrossed, may be structured. A more detailed study of mating systems in tropical rain forest trees may provide additional insights into the mating patterns of these trees. Such studies will be useful not only in understanding the dynamics of micro-evolutionary processes, but also in the conservation and management of tropical forest trees.

Epiphyte Biomass and Nutrient Capital of a Neotropical Elfin Forest

Epiphyte Biomass and Nutrient Capital of a Neotropical Elfin Forest

Transpiration of Trees in a Tropical Rainforest

The tritium method was used to measure the transpiration of twenty trees in a tropical rainforest in the Amazon Territory of Venezuela. Transpiration rates ranged from 2-7 1 day-' for small understorey trees to 1180 1 day-' for large canopy trees. Transpiration rates were highly correlated (r = 0 96) with the sapwood area of trees. Transpiration rate, as a function of sapwood area, was independent of species and independent of soil type on which trees were growing.