Spatial and temporal scales of canopy disturbance and recovery across an old‐growth tropical rain forest landscape

Abstract

AbstractThe distribution of canopy heights in tropical rain forests directly affects carbon storage and the maintenance of biodiversity. We report results from a unique 20‐yr record of annual monitoring of canopy‐height distributions across an old‐growth tropical rain forest landscape at the La Selva Biological Station in Costa Rica. Canopy heights to 15 m were measured annually in 18 0.50‐ha plots at 231 points on a 5 × 5 m grid from 1999–2018 (nine plots in 1999), and heights >15 m were classified as “high canopy.” During the study two major disturbance events (one immediately prior to the study) dominated the landscape‐scale distribution of canopy heights. Height recovery from the 1997–1998 strong El Niño disturbance took approximately 15 yr. Frequency of canopy gaps varied an order of magnitude among years and 96% disappeared in ≤2 yr. High‐canopy coverage and gap frequency varied substantially across the local gradients of soil nutrients and topography, and plot‐level conditions and trends frequently differed from the landscape‐level patterns. In contrast to the two major landscape‐level disturbances, significant plot‐level disturbances were common throughout two decades. Including a similar data set taken in 1992, canopy‐height distributions for the last three decades over this old‐growth tropical rain forest landscape are most parsimoniously interpreted as showing local disturbance and recovery and no unidirectional trends over time. Together these results suggest that understanding the landscape‐ and plot‐level dynamics of tropical rain forest canopy‐height distributions will require repeat sampling for multiple decades, while accurately measuring gap frequency and recovery will require sample intervals of ≤2 yr.