Ecological Drought in Riparian Ecosystems
Science Center Objects
Drought is killing riparian trees along many rivers in the western United States. The cause can be increasing temperature or decreasing precipitation, flow or water-table elevation. At multiple locations we are relating water availability to physiological measurements of tree survival and water stress, such as ring width, carbon stable isotope ratio and branch hydraulic conductivity. These relations will allow us to determine the minimum amount of water necessary to keep trees alive, and to predict how changes in flow, groundwater level, precipitation or temperature would affect survival.
Stable isotopes of carbon in cottonwood tree rings provide a record of past drought stress. This figure shows the strong negative correlation between annual September-August precipitation and the 13C/12C ratio of cottonwood rings averaged across seven trees from the flood plain of the Little Missouri River in Theodore Roosevelt National Park, ND (r = -0.60). Public domain.
A Common Garden at the Colorado State Nursery in Fort Collins, Colorado, established in 2005 to study evolution of phenology of riparian cottonwood and saltcedar. Plants were collected along a longitudinal gradient from Texas to Montana. Phenology is the seasonal timing of life history events including leaf opening, flowering, seed release, bud formation and leaf senescence. Monitoring of about 280 cottonwoods continues at this research site (Friedman et al. 2008, 2011). Public domain.
Drought stressed Populus euphratica along the Tarim River, in the Taklamakan Desert, Xinjiang, China. As a result of flow diversion, surface water no longer flows in this channel. Photo by Jonathan Friedman. Public domain.
Populus euphratica leaf bud. Photo by Jacqueline Robertson, contractor to USGS. Public domain.
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Date published: December 1, 2016Status: ActiveRiparian Ecology
Riparian ecologists at the Fort Collins Science Center study interactions among flow, channel change, and vegetation along rivers across the western United States and worldwide. Our work focuses on issues relevant to the management of water and public lands, including dam operation, climate change, invasive species, and ecological restoration. Investigations take place on a range of scales. ...
Climate, streamflow, and legacy effects on growth of riparian Populus angustifolia in the arid San Luis Valley, Colorado
Knowledge of the factors affecting the vigor of desert riparian trees is important for their conservation and management. I used multiple regression to assess effects of streamflow and climate (12–14 years of data) or climate alone (up to 60 years of data) on radial growth of clonal narrowleaf cottonwood (Populus angustifolia), a foundation...
Andersen, Douglas Flow regime effects on mature Populus fremontii (Fremont cottonwood) productivity on two contrasting dryland river floodplains
I compared riparian cottonwood (Populus fremontii) productivity-discharge relationships in a relictual stand along the highly regulated Green River and in a naturally functioning stand along the unregulated Yampa River in semiarid northwest Colorado. I used multiple regression to model flow effects on annual basal area increment (BAI) from 1982 to...
Andersen, Douglas C. Tree mortality in mature riparian forest: Implications for Fremont cottonwood conservation in the American southwest
Mature tree mortality rates are poorly documented in desert riparian woodlands. I monitored deaths and calculated annual survivorship probability (Ps) in 2 groups of large (27–114 cm DBH), old (≥40 years old) Fremont cottonwood (Populus fremontii Wats.) in a stand along the free-flowing Yampa River in semiarid northwestern Colorado. Ps =...
Andersen, Douglas Incorporating climate change projections into riparian restoration planning and design
Climate change and associated changes in streamflow may alter riparian habitats substantially in coming decades. Riparian restoration provides opportunities to respond proactively to projected climate change effects, increase riparian ecosystem resilience to climate change, and simultaneously address effects of both climate change and other human...
Perry, Laura G.; Reynolds, Lindsay V.; Beechie, Timothy J.; Collins, Mathias J.; Shafroth, Patrick B. Genetic and environmental influences on leaf phenology and cold hardiness of native and introduced riparian trees
To explore the roles of plasticity and genetic variation in the response to spatial and temporal climate variation, we established a common garden consisting of paired collections of native and introduced riparian trees sampled along a latitudinal gradient. The garden in Fort Collins, Colorado (latitude 40.6°N), included 681 native plains...
Friedman, J. M.; Roelle, J.E.; Cade, B.S. Salinity tolerance and mycorrhizal responsiveness of native xeroriparian plants in semi-arid western USA
Restoration of salt-affected soils is a global concern. In the western United States, restoration of salinized land, particularly in river valleys, often involves control of Tamarix, an introduced species with high salinity tolerance. Revegetation of hydrologically disconnected floodplains and terraces after Tamarix removal is often difficult...
Beauchamp, Vanessa B.; Walz, C.; Shafroth, P.B. Physiological and morphological response patterns of Populus deltoides to alluvial groundwater
We examined the physiological and morphological response patterns of plains cottonwood [Populus deltoides subsp. monilifera (Aiton) Eck.] to acute water stress imposed by groundwater pumping. Between 3 and 27 July 1996, four large pumps were used to withdraw alluvial groundwater from a cottonwood forest along the South Platte River, near Denver,...
Cooper, D.J.; D'Amico, D.R.; Scott, M.L. Riparian vegetation response to altered disturbance and stress regimes
Management of terrestrial carbon fluxes is being proposed as a means of increasing the amount of carbon sequestered in the terrestrial biosphere. This approach is generally viewed only as an interim strategy for the coming decades while other longer-term strategies are developed and implemented — the most important being the direct...
Shafroth, P.B.; Stromberg, J.C.; Patten, D.T. Channel incision and patterns of cottonwood stress and mortality along the Mojave River, California
In 1995, mapping and classification of riparian vegetation along the Mojave River in southern California revealed an 8-km reach in which riparian cottonwoods (Populus fremontii Wats.) were stressed or dying. We tested a set of predictions based on the inference that cottonwood decline was an indirect result of lowered water-table levels following...
Scott, M.L.; Lines, G.C.; Auble, G.T. Woody riparian vegetation response to different alluvial water table regimes
Woody riparian vegetation in western North American riparian ecosystems is commonly dependent on alluvial groundwater. Various natural and anthropogenic mechanisms can cause groundwater declines that stress riparian vegetation, but little quantitative information exists on the nature of plant response to different magnitudes, rates, and durations...
Shafroth, P.B.; Stromberg, J.C.; Patten, D.T. Effects of salinity on establishment of Populus fremontii (cottonwood) and Tamarix ramosissima (saltcedar)
No abstract available.
Shafroth, P.B.; Friedman, J. M.; Ischinger, L.S. Establishment of Populus deltoides under simulated alluvial groundwater declines
Establishment, growth, and survival of seedlings of Populus deltoides subsp. monilifera (plains cottonwood) were examined in an experimental facility simulating five rates of declining alluvial groundwater. The treatments were permanent saturation, drawdown rates of 0.4, 0.7, 2.9 cm/d and immediate drainage. The experiment was conducted outdoors...
Segelquist, Charles A.; Scott, Michael L.; Auble, Gregor T.