Disturbance and Tropical Pioneer Species: Patterns of Association Across Life History Stages

BAckground

The authors studied pioneer species common in the Sinharaja World Heritage Reserve in Sri Lanka to characterize differences in relation to canopy openness and type, and intensity of disturbance using a combination of field work, canopy photos, and regression models.

Research Goals & Methods

Using a combination of sub plots and transects, seedling, sapling, and larger size classes of eight tree species (Alstonia macrophylla, Dillenia triquetra, Macaranga indica, Macaranga peltata, Melastoma malabathricum, Schumacheria castaneifolia, Trema orientalis, and Wendlandia bicuspidate) were sampled in three ~100 ha areas within the Sinharaja forest reserve, adjacent to the reserve, and 13 km away. Each individual’s light environment, stage of forest development and disturbance characteristics was assessed. Additionally, canopy hemispherical photographs and conditions of disturbance were analyzed and the probability of species’ occurrence and the relative importance of disturbance characteristics were assessed using multinomial logistical regression models.

Conclusions & Takeaways

Canopy openness demonstrated the greatest association with seedling and sapling distribution. In seedlings and saplings, disturbance type was more influential than both the historical condition of disturbance and the intensity of the disturbance, with some evidence that species do occur differentially in certain disturbance types. The authors conclude that the study provides evidence that pioneers of all life history stages differentiate in relation to amount of light and disturbance characteristics and that such differentiations are important mechanisms for the coexistence and diversity of early successional tropical tree species. The authors suggest that species selection for reforestation and restoration match the degree of exposure, history and type of disturbance of the site.