Ecological Dryness: Beyond the Rain Gauge

Trees don’t experience “drought” the way we measure it meteorologically.

The Soil Moisture Story

What matters is available soil moisture, atmospheric demand (VPD), and duration.

Condition	Soil Moisture (VWC)	Response
Optimal	30–50 %	Normal growth
Mild stress	20–30 %	Stomata close midday
Moderate	15–20 %	Leaf drop, growth stops
Severe	<15 %	Wilting, possible mortality

The Old Growth sites show remarkable resilience, with deeper roots maintaining moisture during dry spells.