Shade limits understory trees far more than weather does
Kašpar J, Krejza J, Holík J, Janík D, Janoutová R
Forest Ecology
Shade-tolerant trees you plant beneath a canopy, like hornbeam or field maple, won't respond to a warm spell the way open-grown trees do, so timing care and watering around weather forecasts matters much less than managing light access.
Scientists tracked how trees at different heights in old-growth forests grow hour by hour and found that trees living in the understory, tucked beneath the main canopy, grow in shorter, less frequent windows. Even though the understory has more stable, buffered conditions, those trees can't take full advantage because there's simply not enough light. When they do grow, they grow efficiently, but overall they end up smaller because good growing moments are rare.
Key Findings
Understory trees accumulated fewer total growing hours and had shorter growing seasons than canopy trees across all five species studied.
When understory trees did grow, their growth rate per hour (normalized by stem diameter) was higher than canopy trees, but total annual growth remained constrained.
Statistical models (GLMMs) predicted canopy tree growth well using climate variables but performed poorly for understory trees, confirming that light, not weather, drives understory growth timing.
chevron_right Technical Summary
Trees growing in the shade beneath a forest canopy grow for fewer hours, in shorter bursts, and are less responsive to weather than their sun-lit neighbors above. Light, not temperature or humidity, is the main bottleneck for understory tree growth.
Abstract Preview
Original paper
Growth patterns and climate sensitivity differ for understory and canopy trees.
While vertical forest structure is known to influence microclimatic conditions and tree growth, detailed knowledge of differences in seasonal growth dynamics between understory and canopy trees, es...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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