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Karen Schlatter

Publications and source records attributed to Karen Schlatter.

6 recordsLinked to original sources
USGS2022

Vegetation monitoring

Sonoran Institute, Pronatura Noroeste, and University of Arizona conducted vegetation monitoring in riparian restoration sites and control sites along the Colorado River corridor in Mexico during the fall (end of the growing season) of 2018. The overall goal of the vegetation monitoring program was to quantify impacts of restoration actions on the extent, composition, and structure of riparian habitat and to relate habitat characteristics to bird abundance and diversity. Specific monitoring objectives were to measure the vegetation vertical structure, density, and cover by species in active riparian restoration sites that had been planted prior to 2017 (> 2 years of growth) in Laguna Grande (CILA, Herradura, and Cori sites) and Miguel Alemán (Fig. 3-1) and to compare vegetation metrics in the restoration sites to the control sites to assess impacts of restoration. The Chaussé restoration site is scheduled for initial monitoring in 2021. This report chapter summarizes 2018 results from the restoration and control sites and compares restoration site results between 2017 and 2018.

Arizona, Baja California↗
USGS2017

A history of the 2014 Minute 319 environmental pulse flow asdocumented by field measurements and satellite imagery

As provided in Minute 319 of the U.S.-Mexico Water Treaty of 1944, a pulse flow of approximately 132 million cubic meters (mcm) was released to the riparian corridor of the Colorado River Delta over an eight-week period that began March 23, 2014 and ended May 18, 2014. Peak flows were released in the early part of the pulse to simulate a spring flood, with approximately 101.7 mcm released at Morelos Dam on the U.S.-Mexico border. The remainder of the pulse flow water was released to the riparian corridor via Mexicali Valley irrigation spillway canals, with 20.9 mcm released at Km 27 Spillway (41 km below Morelos Dam) and 9.3 mcm released at Km 18 Spillway (78 km below Morelos Dam). We used sequential satellite images, overflights, ground observations, water discharge measurements, and automated temperature, river stage and water quality loggers to document and describe the progression of pulse flow water through the study area. The rate of advance of the wetted front was slowed by infiltration and high channel roughness as the pulse flow crossed more than 40 km of dry channel which was disconnected from underlying groundwater and partially overgrown with salt cedar. High lag time and significant attenuation of flow resulted in a changing hydrograph as the pulse flow progressed to the downstream delivery points; two peak flows occurred in some lower reaches. The pulse flow advanced more than 120 km downstream from Morelos Dam to reach the Colorado River estuary at the northern end of the Gulf of California.

Ecological Engineering↗
USGS2017

Integrating active restoration with environmental flows to improve native riparian tree establishment in the Colorado River Delta

Drastic alterations to river hydrology, land use change, and the spread of the nonnative shrub, tamarisk (Tamarix spp.), have led to the degradation of riparian habitat in the Colorado River Delta in Mexico. Delivery of environmental flows to promote native cottonwood (Populus spp.) and willow (Salix spp.) recruitment in human-impacted riparian systems can be unsuccessful due to flow-magnitude constraints and altered abiotic–biotic feedbacks. In 2014, an experimental pulse flow of water was delivered to the Colorado River in Mexico as part of the U.S.-Mexico binational agreement, Minute 319. We conducted a field experiment to assess the effects of vegetation removal, seed augmentation, and environmental flows, separately and in combination, on germination and first-year seedling establishment of cottonwood, willow, and tamarisk at five replicate sites along 5 river km. The relatively low-magnitude flow deliveries did not substantively restore natural fluvial processes of erosion, sediment deposition, and vegetation scour, but did provide wetted surface soils, shallow groundwater, and low soil salinity. Cottonwood and willow only established in wetted, cleared treatments, and establishment was variable in these treatments due to variable site conditions and inundation duration and timing. Wetted soils, bare surface availability, soil salinity, and seed availability were significant factors contributing to successful cottonwood and willow germination, while soil salinity and texture affected seedling persistence over the growing season. Tamarisk germinated and persisted in a wider range of environmental conditions than cottonwood and willow, including in un-cleared treatment areas. Our results suggest that site management can increase cottonwood and willow recruitment success from low-magnitude environmental flow events, an approach that can be applied in other portions of the Delta and to other human-impacted riparian systems across the world with similar ecological limitations.

Colorado River↗
USGS2017

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

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.

Colorado River↗
USGS2017

It takes more than water: Restoring the Colorado River Delta

Environmental flows have become important tools for restoring rivers and associated riparian ecosystems ( Arthington, 2012; Glenn et al., 2017 ). In March 2014, the United States and Mexico initiated a bold effort in restoration, delivering from Morelos Dam a “pulse flow” of water into the Colorado River in its delta for the purpose of learning about its environmental effects ( Flessa et al., 2013; Bark et al., 2016 ). Specifically, scientists evaluated whether the pulse flow, albeit minuscule compared to historical floods, could provide the ecological functions needed to establish native, flood-dependent vegetation to restore natural habitat along the riparian corridor.

Colorado River Delta↗