Tree Mortality and Collecting Botanical Vouchers in Tropical Forests1

There is growing concern about the potential impact of reseatchers on tropical forest ecology, but few data. The aim of this paper is to examine the effects of collecting botanical specimens from tropical forest trees on their subsequent survivorship, using mortality data from plots in Amazonian Peru that were established in 1989 and reinventoried in 1994. In total, 2017 trees were originally tagged and collections were made from 948 trees. Making voucher collections always involved using unsterilized telescopic plant collecting poles to cut representative small branches, and sometimes also involved using iron-spiked tree-climbing gear to gain access to the canopy. Annual mortality in the four plots averaged 1.99 percent. Among the whole population of dicotyledenous trees, there was no detectable difference between the mortality rate of collected trees (1.96%) and noncollected trees (2.29%). We conclude that in spite of the physical damage caused to collected trees, collecting voucher specimens from tropical moist forest trees may not affect their survivorship, at least in the short-term. Further studies are needed to fully evaluate the potential impacts of research activities on petmanent forest plots in the tropics.     

Influence of Forest Type and Tree Species on Canopy‐Dwelling Beetles in Budongo Forest,Uganda1

Beetles were collected on 64 trees of four species (Cynometra alexandri C. H. Wright, Rinorea beniemis (Welwitsch ex Olivier) Kuntze, Teclea nobilis Delile, and Trichilia rubescens Olivier) in Budongo Forest, Uganda, using an insecticidal fogging technique. Selected tree species were abundant, taxonomically not closely related, and different in the shape of leaves, growth form, and size, with heights between 7 and 35 m. Trees were fogged in an old primary forest stand, in an area of secondary forest where selective logging was performed, and in a swamp forest. Eight conspecific trees per forest type were fogged. A total of 29,736 beetles were collected from all trees that could be assigned to 1433 (morpho)‐species; 41.6 percent were singletons and 89.6 percent of species were found with less than ten individuals. Abundant beetle taxa included Latridiidae (N= 4093), Chrysomelidae (3952), Staphylinidae (2931), Apioninae (2621), and Curculionidae (2457). Most species‐rich groups were Staphylinidae (N= 196 spp.), Curculionidae (189), and Chrysomelidae (148). Abundance increased in the order: primary < secondary < swamp forest. Due to the relatively high dominance of some species in the secondary forest, species richness increased in the order: secondary < primary < swamp forest. Beta diversity measures and factor analysis showed distinct differences among forest types but higher similarity of beetle communities on different tree species within one forest type. The taxonomic distribution of beetles in the secondary forest was more heterogeneous than in the primary forest. Analyses of the data revealed low host specificity even for phytophagous beetles, underlining the importance of habitat structure and chance effects on the spatial distribution of beetles in the canopy of Budongo Forest.     

Age and Long-term Growth of Trees in an Old-growth Tropical Rain Forest, Based on Analyses of Tree Rings and 14C1

In an old‐growth tropical wet forest at La Selva, Costa Rica, we combined radiocarbon (¹⁴C) dating and tree‐ring analysis to estimate the ages of large trees of canopy and emergent species spanning a broad range of wood densities and growth rates. We collected samples from the trunks of 29 fallen, dead individuals. We found that all eight sampled species formed visible growth rings, which varied considerably in distinctiveness. For five of the six species for which we combined wood anatomical studies with ¹⁴C‐dates (ring ages), the analyses demonstrated that growth rings were of annual formation. The oldest tree we found by direct ring counting was a Hymenolobium mesoamericanum Lima (Papilionaceae) specimen, with an age of ca. 530 years at the time of death. All other sampled individuals, including very large trees of slow‐growing species, had died at ages between 200 and 300 years. These results show that, even in an everwet tropical rain forest, tree growth of many species can be rhythmic, with an annual periodicity. This study thus raises the possibility of extending tree‐ring analyses throughout the tropical forest types lacking a strong dry season or annual flooding. Our findings and similar measurements from other tropical forests indicate that the maximum ages of tropical emergent trees are unlikely to be much greater than 600 years, and that these trees often die earlier from various natural causes.