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A large-scale environmental flow experiment for riparian restoration in the Colorado River delta

Ecological Engineering

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https://doi.org/10.1016/j.ecoleng.2017.02.016

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Abstract

Managing streamflow is a widely-advocated approach to provide conditions necessary for seed germination and seedling establishment of trees in the willow family (Salicaceae). Experimental flow releases to the Colorado River delta in 2014 had a primary objective of promoting seedling establishment of Fremont cottonwood (Populus fremontii) and Goodding's willow (Salix gooddingii). We assessed seed germination and seedling establishment of these taxa as well as the non-native tamarisk (Tamarix spp.) and native seepwillow shrubs (Baccharis spp.) in the context of seedling requirements and active land management (land grading, vegetation removal) at 23 study sites along 87 river km. In the absence of associated active land management, experimental flows to the Colorado River delta were minimally successful at promoting establishment of new woody riparian seedlings, except for non-native Tamarix. Our results suggest that the primary factors contributing to low seedling establishment varied across space, but included low or no seed availability in some locations for some taxa, insufficient soil moisture availability during the growing season indicated by deep groundwater tables, and competition from adjacent vegetation (and, conversely, availability of bare ground). Active land management to create bare ground and favorable land grades contributed to significantly higher rates of Salicaceae seedling establishment in a river reach with high groundwater tables. Our results provide insights that can inform future environmental flow deliveries to the Colorado River delta and its ecosystems and other similar efforts to restore Salicaceae taxa around the world.

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Additional publication details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
A large-scale environmental flow experiment for riparian restoration in the Colorado River delta
Series title:
Ecological Engineering
DOI:
10.1016/j.ecoleng.2017.02.016
Volume:
106
Issue:
Part B
Year Published:
2017
Language:
English
Publisher:
Elsevier
Contributing office(s):
Fort Collins Science Center
Description:
16 p.
First page:
645
Last page:
660
Country:
Mexico, United States
Other Geospatial:
Colorado River