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Volume 8, Number 1 December 2015: EXPERIENCES IN REVEGETATION ON THE LOWER COLORADO RIVER (Softcover)
Bulletin of the Revegetation and Wildlife Management Center
Volume 8, Number 1 December 2015: EXPERIENCES IN REVEGETATION ON THE LOWER COLORADO RIVER


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Bulletin of the Revegetation and Wildlife Management Center
Volume 8, Number 1 December 2015: EXPERIENCES IN REVEGETATION ON THE LOWER COLORADO RIVER

by Bertin W. Anderson

PRICE: 15 $

ISBN: 978-0-9890784-5-0
Softcover 545 pages

 

INTRODUCTION

When I began work with Dr. Robert D. Ohmart on the lower Colorado River (LCR) in 1973 saltcedar (Tamarix ramosissima) was already a species with a very bad reputation. The general opinion was that its spread needed to be eradicated or at least reduced in areal extent. At that time the primary reason for wanting to control it was to save water, the assumption was that saltcedar used inordinately large quantities of water. Such conclusions were based on scanty data or simply made by proclamation. (In those days this procedure was sometimes simply referred to as “best professional judgment”). The Bureau of Reclamation was the leader in the effort to get saltcedar control off the ground and that this effort was to follow a highly professional protocol.
The initial steps of the protocol were to include a classification of the vegetation types in the valley and then determine the density and diversity of the birds and mammals associated with the various vegetation types. When I arrived, the idea was to begin censusing birds and mammals at the north end of the LCR and gradually work to the south end by study’s conclusion. Problems with this approach were immediately apparent to me; to be meaningful comparisons of the bird and mammal composition of the various plant community types it was imperative to census the entire valley each month. The latter procedure was adopted. By the end of 1974 we were censusing most of the plant community types found between Davis Dam and Yuma, AZ each month. Word was that when this was completed, efforts would begin to replace large tracts of saltcedar with smaller tracts of native vegetation that would be equal or better wildlife habitat than the saltcedar stands. This would result in no damage being done to the wildlife along with water salvage. By 1978 we were asked by the Bureau of Reclamation to initiate a small effort to re-establish native vegetation. Most of the initial effort was directed at finding out what was known about autecological requirements of native riparian plant species. This involved library work as well as interviews of knowledgeable people and led to the realization that there was practically nothing known about autecological requirements of native plant species—including cottonwood and willow.
With this in mind we began a much larger 2-year revegetation project adjacent the Cibola National Wildlife Refuge. The site for this project was sandy dredge spoil that had very low salinity levels. The objective of the project was to investigate things like the importance of depth to the water table, effects of competition from other plants, the importance of tillage, and how much water various species needed for maximum growth. There were no plans for long term monitoring of this effort, the presumption being that everything we needed to know could be learned in 2 years.
Dr. Ohmart and I applied what we learned on that initial project to a small project on the Rio Grande River near Presidio, Texas. We obtained additional valuable information on that project, but again there was no long term monitoring. In fact, large releases from Rio Grande River Dams flooded the site for so long that most of the trees were drowned in the second year. About that time I departed from Arizona State University and began, on my own, to study revegetation in greater depth with a series of projects on the Kern River near Kernville, California. This work involved 4 projects funded through the Nature Conservancy that were executed over a 4 year period with monitoring continuing through the fourth year. The duration was better (longer is better, at least with revegetation monitoring) and we learned a great deal via several controlled experimental studies, but monitoring was, again, over too short a period. At that point, with much new information in hand, I began revegetation work on the LCR.
It was obvious that if we were to ever get long term results we would have to encourage agencies to conduct revegetation projects for a longer period of time. It was not so easy to convince those funding such projects that this should be done. As a part of monitoring schemes we thought that projects should always be associated with experimental work and that the projects should be monitored for at least 5 years. By this time the trees on our original project adjacent the Cibola National Wildlife Refuge were 6 years old. We decided that we would do as much monitoring on that site as we could squeeze in. (There was a final report for this project- Anderson and Ohmart 1982- but was much too long for inclusion here). That effort yielded much valuable information, especially concerning the importance of depth to the water table for a variety of species and the benefits of deep tillage. Following this we conducted a 40 ha project on the Cibola National Wildlife Refuge. We conducted this project with a complex series of experimental designs, but as was usually the case this project was funded for only 2 years and we had to beg for the second year. In addition there was no final report required for the project. Nonetheless we learned a great deal more, especially about the effects of salinity and denser soils on growth and survival of several species. Had we prepared a report for this project it would be the lead chapter in this report. This brings us to the point where this volume begins.
We continued to conduct revegetation projects on the LCR from 1989-2008. This book is made up of 30 reports involving autecological projects completed on the LCR during this time period. Most of these projects are based on a revegetation project. The results of one study (p.522), conducted in 1987 (discussed next), involved random collection of a number of autecological variables on 50 randomly distributed 20 ha plots lying between Davis Dam in the north and of Cibola National Wildlife Refuge. The intent was to learn the range associated with a number of variables and their distribution throughout the LCR valley. The overall objective of this report is to provide investigators with the data that we collected. We also wanted to point out the proportion of studies that were done on sites that were not compatible with long term survival judged on the basis of what we had learned beginning in 1980. When agencies or other parties had a site, they didn’t seem to be concerned with whether it was suitable or not—just get it revegetated. Long term outcomes were seldom given more than lip service. The attitude was simple—plant the trees and they will grow and survive. We always insisted that there be experimental work superimposed on the practical efforts and we were able to develop this aspect.
Another intent of this book is to present a historic narrative of progress that we made in developing a perspective on the autecology of the lower Colorado River ecosystem. Although, couched in somewhat subdued language, readers will come away with a sense of the frustrations that we encountered as well as the feelings of exuberance associated with projects that went well. Experimental designs often suffered disruption when events difficult to predict, nevertheless happen.
The book ends with an assessment of the findings associated with our work spanning the 3 decades of work involving the 29 sites reported on. I will comment on the proportion of the LCR riparian zone that are suitable for riparian obligate and facultative species. I will present data concerning the likelihood that it is arrowweed, not saltcedar, that is currently expanding. Finally, I will review the care, or lack of it, that went into the series of projects.

 

 

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