ABSTRACT
Hymenaea courbaril L. var. stilbocarpa (Hayne) Lee et Lang. é uma espécie clímax tolerante a sombra, ao passo que Enterolobium contortisiliquum (Vell.) Morong. é uma espécie pioneira. O desenvolvimento destas espécies pode refletir a habilidade de adaptação aos diferentes fatores ambientais (luz, água e temperatura) no local em que estão crescendo. O suprimento inadequado de um desses fatores pode reduzir o vigor da planta e limitar seu desenvolvimento. O presente trabalho teve como objetivo avaliar os efeitos do nível de sombreamento no crescimento e a concentração de pigmentos fotossintéticos em duas espécies de leguminosas arbóreas, Hymenaea courbaril L. var. stilbocarpa (Hayne) Lee et Lang. e Enterolobium contortisiliquum (Vell.) Morong. O experimento foi conduzido no Setor de Olericultura do Centro Universitário Luterano de Ji-Paraná (CEULJI/ULBRA)/Rondônia. Durante a formação das mudas, ambas as espécies foram expostas a quatro tratamentos de sombra: 0 % (controle - sol pleno); 30 %; 50 % e 80 %. Cada tratamento foi constituído com três repetições de cada espécie; o delineamento experimental foi inteiramente casualisado. Quatro meses após a semeadura, as seguintes análises foram realizadas: número de folhas, altura da planta, comprimento do sistema radicular, massa seca total e concentração de pigmentos fotossintéticos. O tratamento sob sol pleno afetou negativamente o crescimento de ambas as espécies. As mudas crescidas sob 50% e 80% apresentaram melhor desenvolvimento. Conforme o aumento do sombreamento houve um decréscimo na razão clorofila a/b e um aumento nas concentrações de clorofila total e carotenóides totais.
Hymenaea courbaril L. var. stilbocarpa (Hayne) Lee et Lang. is a clímax shadow tolerant specie and Enterolobium contortisiliquum (Vell.) Morong., by the other hand, is considered as a pioneer specie. The development of these species may reflect its adaptation ability to different environmental elements (light, water and temperature) at its growth site. An inadequate supply of some of these elements may reduce plant vigor and limit its development. This work aimed to evaluate the effects of shade intensity on the growth and photosynthetic pigment concentration of two arboreal legumes that are typical to northern Brazil, namely, the Hymenaea courbaril L. var. stilbocarpa (Hayne) Lee et Lang. and the Enterolobium contortisiliquum (Vell.) Morong. The experiment was carried out at the Centro Universitário Luterano de Ji-Paraná (CEULJ/ULBRA)/Rondônia. During the formation of the seedlings, both species were exposed to four treatments of shade: 0 % (control - without shade); 30 %; 50 % e 80 %. Each treatment was carried out with three replications for each species; the experimental design was completely randomized. Four month after sowing, the following analyses were carried out: number of leaves, plant height, roots length, dry mass and photosynthetic pigment concentration. The treatment under 0% shade impaired the seedling growth of both species. The most favorable treatments were 50 % and 80 % shade. According to the shade intensity, the chlorophyll a/b ratio decreased and the chlorophyll and carotenoids increased.
Subject(s)
Photosynthesis , Sunlight , Hymenaea/growth & development , Fabaceae/growth & development , Carotenoids/analysis , Chlorophyll/analysisABSTRACT
Hunting may have drastic effects on some populations of frugivores and seed dispersal agents, which in turn may affect patterns of forest regeneration and plant diversity. However, when a species disappears, it is possible that the population of other species increases due to competition release, compensating or not, their ecological roles. The main aim of this study was to measure density compensation in primate communities, their possible effects on seedling and sapling diversity, and compensation of seed removal rates in two canopy trees (Apeiba aspera and Hymenaea oblongifolia). The study site was Amacayacu National Park (Colombian Amazon), where we carried out a census of mammal species using line transect methods in two forests with different levels of hunting pressure. Vegetation plots were used to quantify plant diversity for seedlings and saplings (4 m² and 25 m² respectively), and fruit traps were set up to estimate seed removal of A. aspera and H. oblongifolia. Large primates were less frequently encountered near human settlements, while small primates exhibited the opposite pattern, suggesting a density compensation effect. The diversity of regenerating plants was higher in the forest where large primates occur. Seed removal was higher in forests with large primates for A. aspera, but not for H. oblongifolia. Overall, the results support the hypothesis of density compensation on the primate community; however, there is no strong evidence of ecological compensation in terms of seed dispersal and regeneration in the species studied. Finally, the presence of large seed dispersers (e.g. Lagothrix lagothricha) was associated with higher plant diversity. Rev. Biol. Trop. 56 (3): 1531-1542. Epub 2008 September 30.
La cacería ha tenido fuertes efectos en algunas poblaciones de frugívoros y dispersores de semillas, lo cual en consecuencia puede afectar los patrones de diversidad de plantas y regeneración del bosque. Sin embargo, es posible que extinciones locales promuevan el incremento de otras especies, que pueden o no compensar roles ecológicos. El principal objetivo de este estudio fue examinar la posibilidad de compensación por densidad en las comunidades de primates y sus posibles efectos sobre la diversidad de plántulas y juveniles, así como también la remoción de semillas de dos árboles (Apeiba aspera e Hymenaea oblongifolia). El trabajo fue realizado en el Parque Nacional Natural Amacayacu (Amazonas - Colombia). Hicimos censos de mamíferos usando transectos lineales en dos bosques con diferentes presiones de cacería. Además, levantamos parcelas de vegetación para plántulas y juveniles (4 m² y 25 m² respectivamente), y ubicamos trampas de frutos bajo al menos seis árboles de cada especie, en cada bosque, para estimar la remoción de semillas. Los encuentros con primates grandes fueron menos frecuentes en bosques cerca de las comunidades indígenas, mientras que para los primates pequeños el patrón fue contrario, sugiriendo un efecto de compensación por densidad. Por otra parte, la diversidad de plántulas y juveniles fue más alta en bosques donde la densidad de primates grandes es mayor. La remoción de semillas fue mayor en bosques con mayor densidad de primates grandes para A. aspera, pero para H. oblongifolia las diferencias entre bosques no fueron significativas. En general, los resultados de este estudio apoyan la hipótesis de compensación por densidad en la comunidad de primates, sin embargo, no hay evidencia fuerte de compensación ecológica en términos de dispersión de semillas y regeneración. Finalmente, la presencia de dispersores grandes (ej. Lagothrix lagothricha) estuvo asociada con una mayor diversidad de plantas.