LEAF LITTER DECOMPOSITION IN NATIVE FOREST, PLANTATION OF Pterogyne nitens AND Eucalyptus urophylla IN SOUTHWESTERN BAHIA

O processo de decomposi\ue7\ue3o regula o ac\ufamulo de serapilheira e a ciclagem de nutrientes em ecossistemas florestais, sendo fundamental para sua manuten\ue7\ue3o. O objetivo deste trabalho foi avaliar a din\ue2mica de decomposi\ue7\ue3o foliar em uma Floresta Estacional Semidecidual Montana e em plantios homog\ueaneos de Pterogyne nitens Tul. e de Eucalyptus urophylla S. T. Blake, localizados no munic\uedpio de Vit\uf3ria da Conquista, Bahia, Brasil. Para avalia\ue7\ue3o da decomposi\ue7\ue3o, folhas rec\ue9m-ca\ueddas foram coletadas, secas em estufa a 65oC, pesadas e colocadas em litter bags, que foram distribu\ueddos aleatoriamente na superf\uedcie do piso florestal de cada uma das \ue1reas estudadas. Realizaram-se coletas de cinco litter bags de forma aleat\uf3ria ap\uf3s 30, 60, 90, 120, 150 e 180 dias da instala\ue7\ue3o. Com base nas massas obtidas, foram estimados o percentual de massa remanescente, as taxas de decomposi\ue7\ue3o (k) e o tempo de meia-vida do folhedo (t1/2). Para caracteriza\ue7\ue3o qu\uedmica, foram separadas tr\ueas subamostras do material foliar seco, que foram mo\ueddas e analisadas, determinando-se os teores de nitrog\ueanio total, carbono, polifen\uf3is, lignina e celulose. Os dados de decomposi\ue7\ue3o foram relacionados com vari\ue1veis ambientais (precipita\ue7\ue3o, temperatura e umidade do ar) e microambientais (temperatura e umidade do solo) referentes ao m\ueas de coleta. O ac\ufamulo total de serapilheira variou entre as \ue1reas estudadas, o maior valor foi observado no plantio de Eucalyptus urophylla (12,7 Mg ha-1), seguido pela floresta nativa (6,9 Mg ha-1) e plantio de Pterogyne nitens (1,1 Mg ha-1). Ao final dos seis meses de avalia\ue7\ue3o, o Eucalyptus urophylla apresentou a maior massa remanescente (73,6%), seguido da floresta nativa (67,8%) e Pterogyne nitens (46,3%). A constante de decomposi\ue7\ue3o (k) foi maior para a Pterogyne nitens (0,0054 g g-1dia), com menores valores para floresta nativa (0,0016 g g-1dia) e Eucalyptus urophylla (0,0015 g g-1dia). A taxa de decomposi\ue7\ue3o da serapilheira foliar do povoamento de Pterogyne nitens situa-se em uma posi\ue7\ue3o superior em rela\ue7\ue3o \ue0s taxas da floresta nativa e do povoamento de Eucalyptus urophylla, o que proporciona \ue0 esp\ue9cie maior capacidade de reciclar mat\ue9ria org\ue2nica e nutrientes. O processo de decomposi\ue7\ue3o nos ecossistemas estudados foi influenciado n\ue3o apenas pela qualidade do folhedo, mas tamb\ue9m pela qualidade do seu microambiente.The decomposition process regulates the accumulation of litter and nutrient cycling in forest ecosystems, being central to its maintenance. The objective of this study was to evaluate the dynamics of leaf litter decomposition in three forest ecosystems (semideciduous forest Montana and homogeneous stands of Pterogyne nitens Tul. and Eucalyptus urophylla ST Blake), located in Vit\uf3ria da Conquista, Bahia, Brazil. To evaluate the decomposition, newly fallen leaves on the ground of trees and shrubs in each of the studied toppings were collected. The sheets were dried at 65 \ub0C, and thereafter, 10 g portions were weighed and placed in litter bags, which were randomly distributed on the surface of the forest floor in each of the areas studied. Five litter bags at random were collected after 30, 60, 90, 120, 150 and 180 days of installation. After collection, the material contained in each litter bag was subjected to drying in an oven at 65 \ub0C and weighed. Based on the obtained masses were estimated the percentage of the remaining mass, the rate of decomposition (k) and half-life time of the litter (t1/2). For chemical characterization three subsamples were separated from the dried leaf litter, which were ground and analyzed by determination of the total nitrogen, carbon, polyphenols, lignin and cellulose. The decomposition was related to environmental variables (precipitation, temperature and humidity) and the microenvironment (temperature and soil moisture).The total accumulated litter varied significantly between the settlements studied, the highest value was observed in the area of Eucalyptus urophylla (12,7 Mg ha-1), followed by native forest (6,9 Mg ha-1) and Pterogyne nitens (1,1 Mg ha-1). At the end of the six months of the experiment, Eucalyptus urophylla showed the greatest remaining mass (73,6%), followed by native forest (67,8%) and Pterogyne nitens (46,3%). The decomposition constant (k) was higher in litter of Pterogyne nitens (0,0054 g g-1 day), with lower values for native forest (0,0016 g g-1 day) and Eucalyptus urophylla (0,0015 g g-1day). The rate of decomposition of leaf litter of the peopling of Pterogyne nitens is in a superior position in relation to rates of native forest and stand of Eucalyptus urophylla, which provides the largest species ability to recycle organic matter and nutrients. The decomposition process in the studied ecosystems is influenced not only by the quality of the litter but also by the quality of their microenvironment