Heat Stress Reduced Redwood Photosynthesis
A University of California Davis study revealed that temperatures above 86 degrees Fahrenheit limit carbon intake in coast redwoods.
Updated on Sept. 28, 2026 in Botany
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A study published in JGR Biogeosciences quantified how extreme heat impacts coast redwoods, noting a decline in photosynthetic activity when ambient temperatures exceed 86 degrees Fahrenheit. Researchers observed that leaf temperatures can climb nearly 20 degrees higher than the surrounding air during these heat events.
Why it matters
Understanding this physiological response is critical for identifying California redwood habitats currently at risk from rising temperatures. As heat contributes to the loss of coastal fog, the trees' primary water source, their ability to maintain normal metabolic processes is increasingly compromised.
Field measurements in Mendocino County showed leaves heating up to 20 degrees above ambient levels, while lab tests confirmed photosynthetic impairment at temperatures reaching 110 degrees Fahrenheit. These trees manage thermal stress by closing stomata—microscopic pores used for gas exchange—to reduce moisture loss at the expense of carbon intake.
The players
University of California Davis
A research university recognized for its extensive programs in agricultural science, plant biology, and environmental studies.
National Science Foundation
A U.S. government agency that supports fundamental research and education across all non-medical fields of science and engineering.
California Forestry and Fire Protection
The state department responsible for fire prevention, resource management, and the protection of California's natural forests.
The details
To regulate internal temperature, redwoods utilize evapotranspiration, a process where water moves through the tree and evaporates from the leaves. During heat stress, trees close their stomata, which are the small openings that facilitate the intake of carbon dioxide for photosynthesis—the conversion of sunlight into chemical energy. This defense mechanism prevents desiccation but effectively slows the tree's physiological breathing and eating processes.
Timeline
Summer 2022: Researchers measured leaf and air temperatures in Mendocino County.
Summer 2024: Researchers concluded final field temperature measurements.
The Tech Race
This study aligns with ongoing efforts by the National Science Foundation to map the resilience of biological systems against rising thermal baselines. It provides a new benchmark for evaluating how iconic species like the coast redwood transition from active growth to defensive survival modes.
The findings help forestry experts identify specific California groves that require immediate conservation interventions or adjusted management practices as heat stress becomes more frequent. While residents won't see immediate changes, the data will influence state-level forest preservation strategies.
The takeaway
Redwoods survive by trading photosynthetic speed for water retention when temperatures climb, a precarious balance that will likely define the species' distribution in the coming decades. Keep watch for future vegetation risk mapping reports from state forestry agencies that apply these findings to specific redwood corridors.
Further reading
For more research on plant physiological responses to climate variables, visit the Botany section.
Source note: This article includes information reported by YubaNet.
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