Environmental changes during secondary succession in a tropical dry forest in Mexico

• Published in: Journal of tropical ecology 2011-09, Vol.27 (5), p.477-489
• Main Authors: Lebrija-Trejos, Edwin, Pérez-García, Eduardo A., Meave, Jorge A., Poorter, Lourens, Bongers, Frans
• Format: Article
• Language: English
• Subjects: Air temperature; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; canopy; costa-rica; deciduous forest; Dry forests; Dry season; Dry seasons; Ecological succession; Environment; Environmental changes; Environmental gradient; Fallowing; Forest ecology; Forest regeneration; Fundamental and applied biological sciences. Psychology; gas-exchange; Heterogeneity; light; microclimate; Moisture content; Old growth forests; plant-communities; rain-forest; Rainforests; Rainy season; Rainy seasons; Relative humidity; Seasonal variations; Seasons; Seedlings; Soil temperature; Soil water; Synecology; Terrestrial ecosystems; tree seedlings; Tropical forests; Tropical rain forests; Understory; vapor-pressure deficit; Vegetation; Vegetation cover; Vegetation effects; Water availability
• ISSN: 0266-4674; 1469-7831
• DOI: 10.1017/S0266467411000253

Vegetation and environment change mutually during secondary succession, yet the idiosyncrasies of the vegetation effect on the understorey environment are poorly understood. To test whether the successional understorey environment changes predictably and is shaped by the structure and seasonality of tropical dry forests, we estimated basal area and vegetation cover, and measured understorey temperature, light and moisture conditions, in 17 plots forming a 60-y chronosequence and a mature forest. Light and air and soil temperature decreased with time (75−15% of open-sky radiation, 31.7−29.3 °C, and +2.5 °C to −0.5 °C relative to ambient, respectively), whereas relative humidity increased (67−74%). Soil water availability increased with early-successional development (−45 to −1 kPa) but decreased afterwards (to −18 kPa). The first axis of a PCA of the rainy-season environment explained 60% of the variation and was strongly related to air temperature and relative humidity. During tropical dry-forest succession, such factors may be more important than light, the reduction in which is not extreme compared with taller and more vertically stratified wet forests. Seasonality significantly affected the successional environmental gradients, which were marked mainly during the wet season. Environmental heterogeneity was higher in the wet than in the dry season, and larger for resources (light and water) than for conditions (temperature and humidity). The wet-season increase in environmental heterogeneity potentially creates differential growing scenarios; the environmental harshness of the dry season would mostly challenge seedling survival.