What is tamarisk?
Tamarisk is an invasive shrub or small tree that is found across the American West. Also known as saltcedar, tamarisk favors sites that are inhospitable to native streamside plants because of high salinity, low water availability, and altered streamflow regimes created by dams. Researchers debate the extent of tamarisk’s negative impacts, but this invasive species can and does alter habitat quality for some wildlife, water use by floodplain vegetation, and the frequency and intensity of wildfires.
One successful tamarisk control method is the introduction of a leaf-eating beetle from the tamarisk’s native range in Asia. Where tamarisks are declining, USGS scientists are studying how ecosystems respond to the removal of an invasive species.
Invasive Saltcedar and Russian Olive Trees Consume Similar Amounts of Water as Native Cottonwoods and Willows, Wildlife Effects Mixed
Long considered heavy water users and poor wildlife habitat, non-native saltcedar and Russian olive trees that have spread along streams and water bodies in the West may not be as detrimental to wildlife and water availability as believed.
Saltcedar with buds and a pollinator
Erosion of invasive saltcedar
Anatomical changes in rings of buried stems can be used to date stratigraphy. Saltcedar stem cross-section cut 2.8 m below the ground surface. Following initial burial of 68 cm in 1969, ring-width decreased, vessel size increased, and annual transitions became less distinct. After a second burial by 41 cm in 1972, annual transitions became indistinguishable. (Friedman and others 2005, 2015).
A beetle introduced to the US to control saltcedar has dispersed to the Middle Rio Grande. This natural-color image by DigitalGlobe, Inc. on July 18, 2016 shows saltcedar defoliated by the beetle (purple) at the confluence of the Rio Puerco and the Rio Grande. If the beetle kills large areas of saltcedar, subsequent floods could accelerate erosion in tributaries, leading to siltation along the Rio Grande and in Elephant Butte Reservoir.
What the beginning of a Tamarix transect looks like. Each transect (using a tape measure in this case) travels perpendicular to the river and ranges from tens of feet to hundreds of feet. Along the transect we collect information about plant community composition, riparian zone architecture, light, leaf litter depth, and soil chemistry (fall 2010).
USGS scientist collecting data on one of our Colorado River Tamarix transects. These are difficult data to collect due to dense thickets Tamarisk can create (spring 2014).
Panels A and B are high resolution, multispectral imagery at the Kanab Creek confluence with the Colorado River in Grand Canyon showing dense stands of tamarisk vegetation that was green and healthy in May 2009 (panel A), but brown and defoliated in May 2013 due to herbivory by the tamarisk beetle (panel B). Panel C shows a lidar and multispectral image-based classification of tamarisk defoliation (“Tamarisk Decline” in legend) due to the tamarisk beetle along the Colorado River in Glen Canyon.
Extensive defoliation of tamarisk (orange/brown vegetation throughout mid-ground) along the Virgin River, Arizona, 2009. Photo by Patrick Shafroth, USGS.
Invasive Tamarisk or saltcedar as it is known, growing on the side of a river. Photo by NASA.
This image is of invasive tamarisk (salt cedar) growing on the banks of the Colorado River.
The northern tamarisk beetle (Diorhabda carinulata) from a Fukang, China lab colony at USDA/ARS Quarantine in Temple, Texas.