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Comparative analysis of photosynthetic light environments within the crowns of juvenile rain forest trees

by Oberbauer, S.F; Clark, D.A; Clark, D.B; Quesada, M.
Publisher: 1989Subject(s): MINQUARTIA GUIANENSIS | PITHECELLOBIUM PEDICELLARE | REGIMENES DE LUZ | BOSQUE NATURAL PRIMARIO | COSTA RICA | LIGHT REGIMES | COSTA RICA | REGIME LUMINEUX | COSTA RICA In: Tree Physiology (Canadá) v. 5(1) p. 13-23Summary: Irradiances within the crowns of saplings of two tropical tree species were simultaneously compared in primary rain forest in Costa Rica. The species examined, Minquartia guianensis Aubl., a relatively slow-growing, canopy species, and Pithecellobium pedicellare (DC) Benth., a less-tolerant, emergent species, have different crown and leaf display patterns. Crown light environments were assessed by placing arrays of quantum sensors among leaves and recording at 5-s intervals for seven days with microloggers. Median total daily quantum flux densities for saplings of both species were less than 2 percent of full sun and did not differ significantly. More than 90 percent of the measurements within the crowns of these saplings were less than 25 ¿mol m exponent-2 s exponent-1. Spatial variability of photon flux densities within sapling crowns was similar for the two species despite differences in leaf display patterns. In saplings of both species, photon flux densities varied significantly over the relatively short distances within crowns and from day to day. Height growth of both species was significantly correlated with total daily photon flux densities and with percentage of full sun. However, only the tolerant species, Minquartia, showed a significant correlation between diameter growth and crown light environment.
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Irradiances within the crowns of saplings of two tropical tree species were simultaneously compared in primary rain forest in Costa Rica. The species examined, Minquartia guianensis Aubl., a relatively slow-growing, canopy species, and Pithecellobium pedicellare (DC) Benth., a less-tolerant, emergent species, have different crown and leaf display patterns. Crown light environments were assessed by placing arrays of quantum sensors among leaves and recording at 5-s intervals for seven days with microloggers. Median total daily quantum flux densities for saplings of both species were less than 2 percent of full sun and did not differ significantly. More than 90 percent of the measurements within the crowns of these saplings were less than 25 ¿mol m exponent-2 s exponent-1. Spatial variability of photon flux densities within sapling crowns was similar for the two species despite differences in leaf display patterns. In saplings of both species, photon flux densities varied significantly over the relatively short distances within crowns and from day to day. Height growth of both species was significantly correlated with total daily photon flux densities and with percentage of full sun. However, only the tolerant species, Minquartia, showed a significant correlation between diameter growth and crown light environment.

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