Dispersal of seeds of Hymenaea courbaril (Fabaceae) in a logged rain forest in the Peruvian Amazonian. David L. GORCHOV1, Jorge M. PALMEIRIM2, Margarita JARAMILLO3, and Cesar F. ASCORRA4 ABSTRACT Seed dispersal of Hymenaea courbaril was studied by following the fate of 585 seeds embedded with small magnets and set in displays in and near a logged strip in rain forest in the Peruvian Amazonian. Mammals took fruits from all displays, which were located in the forest, edge, and cleared strip. Overall removal rates were low – a median of 8.1 fruits / month from displays maintained with 8-10 fruits - but were higher in August than in earlier months. Most fruits were dropped near the display or had their seeds eaten, but > 13% were successfully dispersed. Most of the dispersed seeds were buried, which increases probability of germination. Maximum dispersal distance of live seeds was 12.1 m (median 3.1 m), but other magnets were transported up to 34 m, indicating seeds were dispersed further, but then eaten. Acouchies (most likely Myoprocta pratti) and agoutis (Dasyprocta fuliginosa) were apparently the main dispersal agents. Dispersal of seeds from the forest into the logged strip was rare, suggesting that although rodents disperse H. courbaril, they cannot be relied on for the reseeding this and similar species in recent clearings. KEY WORDS Caesalpinioideae, Dasyprocta fuliginosa, Myoprocta pratti, seed predation, forest management Dispersão de sementes de Hymenaea courbaril (Fabaceae) em uma floresta tropical úmida com exploração madeireira na Amazônia peruana. RESUMO Foi estudada a dispersão de sementes de Hymenaea courbaril, seguindo o destino de 585 sementes marcadas com imãs e expostas a potenciais dispersores, colocadas em agregados no interior e próximo de uma faixa de floresta cortada, na Amazónia peruana. Mamíferos retiraram frutos de todos os agregados, localizados no interior da floresta, na sua borda, e na clareira. As taxas de remoção foram baixas – mediana de 8.1 frutos/mês em agregados mantidos com 8-10 frutos – mas foram mais altas em agosto que nos primeiros meses do ano. A maior parte dos frutos foi abandonada próxima do agregado de origem ou as suas sementes foram consumidas, mas > 13% foram dispersos com sucesso. A maior parte das sementes dispersas foi enterrada, o que favorece a germinação. A distância máxima de dispersão de sementes vivas foi de 12.1 m (mediana 3.1 m), mas outros imãs foram transportados até 34 m, indicando que as sementes foram dispersas mais longe, mas foram consumidas depois. Cutiaras (muito provavelmente Myoprocta pratti) e cutias (Dasyprocta fuliginosa) parecem ter sido os principais agentes de dispersão. A dispersão de sementes da floresta para o interior da clareira foi rara, sugerindo que apesar de alguns roedores dispersarem H. courbaril, não se pode ficar dependente deles para o repovoamento desta e de outras espécies em clareiras recentes. PALAVRAS-CHAVE Caesalpinioideae, Dasyprocta fuliginosa, Myoprocta pratti, predação de sementes, manejo florestal 1 Department of Botany, Miami University, Oxford, Ohio 45056, USA ([email protected]) 2 Centro de Biologia Ambiental e Departamento de Zoologia, Faculdade de Ciências, Universidade de Lisboa, 1700 Lisboa, Portugal 3 Av. Mariscal Caceres 2022, Iquitos, Peru 4 Museo de Historia Natural “Javier Prado”, Casilla 140434, Lima 14, Peru, present address: Conservación Internacional Peru, Chinchon 858-A, Lima 27, Peru * For correspondence: David L. Gorchov, Department of Botany, Miami University, Oxford, Ohio 45056, USA (Fax 513-529-4243; [email protected]) 265 VOL. 34(2) 2004: 251 - 259 DISPERSAL OF SEEDS OF HYMENAEA COURBARIL (FABACEAE) IN A LOGGED RAIN FOREST IN THE PERUVIAN AMAZONIAN INTRODUCTION MATERIALS AND METHODS Natural forest management in the humid tropics can only be economically sustainable if commercially valuable Studied Species tree species are well-represented in the regeneration that follows felling. One system of natural forest management Hymenaea courbaril (Fabaceae: Caesalpinioideae) is a promoted as sustainable is the strip cut system canopy (sometimes emergent) tree of tropical and (Buschbacher, 1990; Hartshorn, 1989). In this system, long, subtropical forests of Mexico and the Caribbean through narrow (30 - 40 m) strips are clear-cut and all timber is Bolivia and south-central Brazil (Francis, 1990). Seedlings extracted. This width was selected to simulate the diameter are shade tolerant but grow faster in high light conditions typical of natural treefall gaps, which are the principal sites (Gerhardt, 1993). The wood is valuable when sawn and is of natural regeneration of many valuable light tropical considered durable, strong, hard, and tough (Patterson, hardwoods (Hartshorn 1980; 1989). No seedlings are 1988; Francis, 1990). In the Peruvian Amazon, its sawn wood planted in the cleared strips; regeneration is from the seed is commercially utilized (Peters et al., 1989). The fruit pulp bank, dispersed seeds, and stump sprouts. Therefore, is edible raw or prepared as a beverage (Francis, 1990). The understanding the dynamics of seed dispersal in the resinous gum is used in some areas in the manufacture of immediate neighborhood of these strips is critical for varnishes or as incense (Schultes and Raffauf, 1990), and assessing the sustainability of this system. both the bark and pulp are used medicinally (Francis, 1990). Most of the tree species valuable for their timber in The fruits are indehiscent legumes (hereafter pods) with a Amazon rain forests have large seeds. For example, of 285 woody exocarp, measuring 4 - 10 cm long by 3 - 7 cm wide forest species listed by Foster (1982), 25% have seed weights at our study site. In our region most fruits contain one seed, > 1 g, compared to 75% of species that are in genera with a but some contain two or three (mean ± SD = 1.17 ± 0.42, mill price greater than US $15 / m3 (Peters et al., 1989). n = 108). Seeds are c. 1 x 2 cm and surrounded by dry, Using seed traps placed 50 cm above the ground to quantify sweet pulp. Pods fall to the ground without breaking open, the seed rain in strips cleared by the strip-cut system in the and if the pod is not opened by animals the seeds are likely Peruvian Amazon, Gorchov et al. (1993) found that very to rot (Janzen, 1983). In Central America pods are opened few large seeds were dispersed into the strips by birds or by agoutis (Dasyprocta punctata), pacas (Agouti paca), bats; furthermore, primates rarely entered these strips (E. tapirs (Tapirus bairdii), and probably white-lipped peccaries Notman, pers. comm.). Thus, terrestrial mammals may be (Tayassu pecari); these animals eat the pulp and seeds the only potentially important carriers of large seeds into (Hallwachs, 1986). However, agoutis sometimes scatter- logged clearings. Many large-seeded tropical forest trees hoard pods under leaf litter (Janzen, 1983). Capuchin have seeds that are primarily dispersed by terrestrial monkeys (Cebus apella) consume the pulp and drop the mammals (Smythe, 1986). The presence of large artificial seeds (Galetti and Pedroni, 1994). In Costa Rica, where clearings is likely to affect the foraging behavior of terrestrial agoutis are the only dispersal agent, the probability of forest mammals, and could influence their role both as seed mortality during both seed and seedling stages is much dispersers and predators. Predation on large seeds by lower away from parent trees than under parent trees rodents is believed to be greater in treefall gaps than in (Hallwachs, 1986). A study in Venezuela suggested that closed forest (Schupp et al., 1989), although evidence is regeneration of H. courbaril in the absence of agoutis was mixed from the few studies published to date (e.g., Nepstad very limited (Asquith et al., 1999). et al., 1996; Restrepo and Vargas, 1999). Seed predation in logged strips 2 - 3 years following clearing was not different Study Site than that in forest understory 15 m from the edge for either of two tree species, but for one of the species this rate was This research was conducted at the Centro de greater than that in more distant forest, and in the other it Investigaciones Jenaro Herrera (4° 55' S; 73° 40' W), a field was lower (Notman et al., 1996). station operated by the Instituto de Investigaciones de la Hymenaea courbaril L. is a commercially valuable Amazonía Peruana and located near the Ucayali River, neotropical tree whose seeds are known to be both approximately 130 km south of Iquitos. Precipitation dispersed and preyed upon by terrestrial mammals (Janzen, averages 2521 mm per year and tends to be lower in June - 1983; Hallwachs, 1986; Asquith et al., 1999). To determine September (Spichiger et al., 1989), but rarely drops below the role that terrestrial mammals play in the dispersal of H. 100 mm per month (Ascorra et al., 1993). courbaril into logged strips from adjacent forest in the The experiments reported here were carried out in and Peruvian Amazon, we investigated (i) how rapidly terrestrial near a 30 by 150 m strip cut in October, 1999 in primary mammals removed fruits from simulated ground fruit lowland rain forest on high terrace, as part of a broader displays; (ii) how far they transported the seeds of the study on seed dispersal and regeneration. Experiment 1 was removed fruits; (iii) whether seeds were carried into recently initiated in August 1990, 10 months after clearing. At that logged strips; and (iv) the fate of the transported seeds. time, regenerating stems were dense but small, with only 266 VOL. 34(2) 2004: 265 - 273 • GORCHOV et al. DISPERSAL OF SEEDS OF HYMENAEA COURBARIL (FABACEAE) IN A LOGGED RAIN FOREST IN THE PERUVIAN AMAZONIAN 0.2 trees m-2 exceeding 2 m, evenly divided between To test whether the glue affected removal of fruits by Cecropia spp. seedlings and diverse saplings that survived mammals, on 24 June 1992 we set out in primary forest 4 the felling (unpubl.