Zalamea M.

Leaffall Phenology in a Subtropical Wet Forest in Puerto Rico: From Species to Community Patterns

Zalamea, M. & González, G. (2008) Leaffall phenology in a subtropical wet forest in Puerto
Rico: from species to community patterns. Biotropica, 40, 295-304.

Abstract: 
leaffall periodicity has been related to rainfall regime and dry season length. In weakly seasonal forests, where there is no marked dry season, other climatic factors could trigger leaf shed. In this study, we aimed to determine if other climatic variables (wind speed, solar radiation, photosynthetic photon flux density [PPFD], day length, temperature, and relative humidity) could be better correlated with patterns of litter and leaffall in a weakly seasonal subtropical wet forest in Puerto Rico. Leaffall patterns were correlated mainly with solar radiation, PPFD, day length, and temperature; and secondarily with rainfall. Two main peaks of leaffall were observed: April–June and August–September, coinciding with the periods of major solar radiation at this latitude. Community leaffall patterns were the result of overlapping peaks of individual species. Of the 32 species analyzed, 21 showed phenological patterns, either unimodal (16 species), bimodal (three species), or multimodal (two species). Lianas also presented leaffall seasonality, suggesting that they are subject to the same constraints and triggering factors affecting trees. In addition to solar radiation as a main determinant of leaffall timing in tropical forests, our findings highlight the importance of interannual variation and asynchrony, suggesting that leaffall is the result of a complex interaction between environmental and physiological factors.

Earthworm communities along an elevation gradient in Northeastern Puerto Rico

Gonzalez, Grizelle; Garcia, Emerita; Cruz, Veronica; Borges, Sonia; Zalamea, Marcela; Rivera, Maria M. 2007. Earthworm communities along an elevation gradient in Northeastern Puerto Rico.. European Journal of Soil Biology 43 .

Abstract: 
In this study, we describe earthworm communities along an elevation gradient of eight forest types in Northeastern Puerto Rico, and determine whether their abundance, biomass and/or diversity is related to climatic, soil physical/chemical and/or biotic characteristics. We found that the density, biomass, and diversity of worms varied significantly among forest types. The density of earthworms was highest in the Pterocarpus forest. In terms of biomass, both elfin and the Pterocarpus forests had the highest values. The number of earthworm species significantly increased as elevation and annual rainfall increased and air temperature decreased. We conclude that differences in earthworm species richness along this elevation gradient may be due to a combination of biotic and soil physical and chemical factors. Soil pH and root length density are important predictors of number of worm species along this elevation gradient.
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