FORT scientists established a Common Garden at the Colorado State Forest Service Nursery in Fort Collins, Colorado in 2005 to study the phenology of riparian cottonwood in relation to annual variation in temperature. Phenology is the seasonal timing of life history events including leaf opening, flowering, seed release, bud formation and leaf senescence.
The Cottonwood Common Garden
A common garden is an experiment to find out whether differences between plants are caused by genetics or the environment. Differences that persist when plants are grown together have a genetic component. To initiate the garden, researchers collected over 600 plants from 15 sites along a latitudinal gradient from Texas to Montana and planted the collections in the garden in random order. The garden originally also contained tamarisk collected from the same sites, but these were removed to prevent their spread in around 2009.
From 2009 to 2016, researchers allowed the cottonwoods to grow, enabling them to determine the sex of each tree and to study phenology of diameter growth, flowering and seed release. As cottonwoods grew taller and older, their phenology became more conservative, stopping growth earlier.
Because trees were beginning to die from competition for light, researchers cut them all back to the ground on January 21, 2017. They now cut them back every year to remove the confounding effect of age.
Monitoring of about 280 plains cottonwoods continues at this research site. Current plans include using this long-term data to calibrate a phenological model relating cottonwood phenology to daily variation in temperature and daylength.
Research Highlight: Genetic and environmental influences on cold hardiness of native and introduced riparian trees
Data from the Common Garden show latitudinal variation in fall, but not spring, phenology and in cold hardiness for both cottonwood and tamarisk:
- Trees originally from higher latitudes showed earlier signs of bud formation and leaf senescence in the fall.
- Trees from all latitudes produced new leaves around the same time.
This suggests that field observations of latitudinal variation in fall phenology are likely due to underlying genetics of individual trees, but observations of latitudinal variation in spring phenology are likely due to environmental variations across latitudes.
Below are other science projects associated with this project.
Riparian Ecology
FORT scientists established a Common Garden at the Colorado State Forest Service Nursery in Fort Collins, Colorado in 2005 to study the phenology of riparian cottonwood in relation to annual variation in temperature. Phenology is the seasonal timing of life history events including leaf opening, flowering, seed release, bud formation and leaf senescence.
The Cottonwood Common Garden
A common garden is an experiment to find out whether differences between plants are caused by genetics or the environment. Differences that persist when plants are grown together have a genetic component. To initiate the garden, researchers collected over 600 plants from 15 sites along a latitudinal gradient from Texas to Montana and planted the collections in the garden in random order. The garden originally also contained tamarisk collected from the same sites, but these were removed to prevent their spread in around 2009.
From 2009 to 2016, researchers allowed the cottonwoods to grow, enabling them to determine the sex of each tree and to study phenology of diameter growth, flowering and seed release. As cottonwoods grew taller and older, their phenology became more conservative, stopping growth earlier.
Because trees were beginning to die from competition for light, researchers cut them all back to the ground on January 21, 2017. They now cut them back every year to remove the confounding effect of age.
Monitoring of about 280 plains cottonwoods continues at this research site. Current plans include using this long-term data to calibrate a phenological model relating cottonwood phenology to daily variation in temperature and daylength.
Research Highlight: Genetic and environmental influences on cold hardiness of native and introduced riparian trees
Data from the Common Garden show latitudinal variation in fall, but not spring, phenology and in cold hardiness for both cottonwood and tamarisk:
- Trees originally from higher latitudes showed earlier signs of bud formation and leaf senescence in the fall.
- Trees from all latitudes produced new leaves around the same time.
This suggests that field observations of latitudinal variation in fall phenology are likely due to underlying genetics of individual trees, but observations of latitudinal variation in spring phenology are likely due to environmental variations across latitudes.
Below are other science projects associated with this project.