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1、BlOTROPlCA 35(3): 306-317 2003 Age and Long-term Growth of Trees in an Old-growth Tropical Rain Forest, Based on Analyses of Tree Rings and 14C1 Esther Fichtler lnstitut fur Forstbotanik, Universitaet Goettingen, Buesgenweg 2, D-37077, Goettingen, Germany Deborah A. Clark Department of Biology, Univ
2、ersity of Missouri-St. Louis, 8001 Natural Bridge Road, St. Louis, Missouri and Martin Worbes lnstitut fur tropischen und subtropischen Pflanzenbau, Universitaet Goettingen, Grisebachstrasse 6, D-37077, Goettingen, Germany 63121-4499, U.S.A. ABSTRACT In an old-growth tropical wet forest at La Selva,
3、 Costa Rica, we combined radiocarbon (I4C) 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
4、species formed visible growth rings, which varied considerably in distinctiveness. For five of the six species for which we combined wood anatomical studies with %-dates (ring ages), the analyses demonstrated that growth rings were of annual formation. The oldest tree we found by direct ring countin
5、g 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 ra
6、in 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 fo
7、rests indicate that the max- imum 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. RESUMEN En una area de bosque muy hhmedo tropical localizado en La Selva, Costa Rica, usamos una combinaci6n de andisi
8、s de radiocarbon0 P4C) y anilisis de anillos de crecimiento, para estimar las edad de irboles del dose1 con un amplio espectro de tasas de crecimiento y de densidades de la madera. Analizamos la madera de ocho especies muestreada de troncos de 29 individuos muertos (irboles caidos). Encontramos que
9、las ocho especies estudiadas forman anillos de crecimiento visibles, per0 que estos varian en la distinci6n del limite de sus anillos. Para cinco de las seis especies para las cuales combinamos un estudio anat6mico de la madera con fechado de 14C (edades de 10s anillos), nuestro andisis demostr6 que
10、 10s anillos de crecimiento fueron anuales. El irbol mis viejo en nuestra muestra fue un ejemplar de Hymenolobium mesoamericanum Lima (Papilionaceae), que muri6 a la edad de aproximadamente 530 afios. Las edades a las que murieron 10s demL individuos analizados, incluyendo irboles de gran tamafio y
11、de lento crecimiento, heron entre 200 y 300 afios. Estos resultados demuestran que, ahn en un bosque tropical muy hhmedo, el crecimiento de muchas especies de irboles puede presenrar un crecimiento annual ritmico. Esre estudio demuestra que es posible extender el andisis de anillos de crecimiento po
12、r todo el trbpico, incluyendo las zonas de bosque que no experimentan ni una estaci6n seca fuerte ni inundaci6n anual. Nuestros resultados, y 10s de otros estudios en bosques tropides, indican que es poco probable que las edades mhimas de irboles tropicales emergenres lleguen a ser mucho mayores a 1
13、0s 600 ahos, y que tales irboles frecuentemente mueran a edades menores por causas naturales. Kq word: emergent trees; La Selva; Costa Rica; old canopy; radiocarbon dating; tree ring analysis; tropical wet forest. UNDERSTANDING THE PAST AND CURRENT DYNAMICS OF THE WORLDS TROPICAL rain forests is a p
14、ressing challenge for ecologists. Tropical evergreen forests are disproportionately important in the global car- bon cycle. They have been estimated to account for 32 percent of terrestrial net primary productiv- ity (Field et al. 1998), and combined with tropical dry forests, they comprise an estim
15、ated 59 percent of forest biomass globally (Dixon et al. 1994). In this context, the nature of tropical tree growth rhythms, the maximum age attained by the low- land rain forest trees, and their response to climate variability are still questions under discussion. Received 28 February 2003; revisio
16、n accepted 3 July 2003. 306 Age of Tropical Rain Forest Trees 307 The very large trees in tropical rain forests play important roles in ecosystem structure and func- tion. In spite of their low densities (usually 3% of stems 210 cm diam), they can comprise 25-40 percent of the total aboveground biomass (Brown & Lug0 1992, Brown et al. 1995, Clark & Clark 1996). Likely to be among the oldest trees present, these individuals could serve as valuable indicators of stand history. Very little is curre
