Study Finds Trees Stop Wood Growth Before Photosynthesis Ends

A study of 137 sites across the United States found that trees stopped wood growth months before photosynthesis ended each year. The research showed that roughly 36 percent of yearly carbon uptake at eastern sites and 26 percent at California sites occurred after growth had ceased.

Forests convert carbon dioxide into wood that can store the gas for decades or centuries. Other uses of carbon, such as foliage production, typically last shorter periods.

Scientists measured conditions at four sites in greater detail. Wood growth occurred only during periods of low aridity and temperature, while photosynthesis continued at a reduced rate under hotter and drier conditions. The study reported that growth activity stopped quickly when dry and hot conditions arrived. Photosynthesis persisted longer under the same circumstances.

Current climate models often assume that higher photosynthesis directly increases wood growth. The researchers stated that this assumption does not match observed patterns. If more absorbed carbon flows to short-term uses instead of wood, the long-term carbon storage capacity of forests would decline.

The authors wrote that models assuming tight links between photosynthesis and growth may overestimate future forest carbon sequestration under rising atmospheric moisture demand. The team plans to examine whether the same pattern appears in other tree species and regions.