Abstract

The occurrence of annual growth rings in tropical trees-the result of the seasonal activity of vascular cambium-has been explained by seasonal water deficit or flooding periods. However, little is known about the drivers of annual tree-ring formation under tropical hyper-humid conditions without clear seasonal dry periods or flooding (ever-wet conditions). Shelford's law states that the deficit or the excess of environmental resources limits plant growth. Accordingly, we hypothesize that excess soil moisture, a slight seasonal reduction of precipitation and a reduction in light availability determine rhythmic growth in ever-wet tropical forests.We first assessed the occurrence of rhythmic growth in 14 tree species from the Biogeographic Choco Region (annual rainfall 7200 mm) using three methods: Radiocarbon (C-14) dating (all studied species), tree-ring synchronization (4 species that have replicates) and automatic dendrometers (two species). Then, we assessed the effect of environmental drivers (rainfall, short-wave radiation, temperature and soil moisture) on tree growth based on tree ring and dendrometer observations.We present evidence of annual tree-ring formation in all 14 studied tree species. Depending on the tree species, we observed positive and negative correlations between growth, water availability and light availability. These relationships suggest that both excess or deficit of environmental resources may explain the seasonal pattern of tree growth. Although we cannot differentiate between excess soil water and low light availability by high cloudiness, we suggest that cloudiness frequency could affect tree growth in these forests.Synthesis. We reveal the annual formation of growth rings in the unexplored wetter-end tropical forests, where seasonal growth depends on either high soil moisture and hypoxia or light limitations by cloudiness and photosynthesis constraints.

Keywords

Choco biogeographical region; dendrometers; rainiest place on earth; tree rings

Published in

Journal of Ecology
2023, Volume: 111, number: 4, pages: 889-902
Publisher: WILEY

SLU Authors

• Sierra, Carlos

  • Department of Ecology, Swedish University of Agricultural Sciences
    
  • Max Planck Institute for Biogeochemistry

UKÄ Subject classification

Ecology


Publication identifier

DOI: https://doi.org/10.1111/1365-2745.14069

Permanent link to this page (URI)

https://res.slu.se/id/publ/121617