You are here

100 years of vegetation change at the Sierra Ancha Experimental Forest

Status: 
Action
Dates: 
May, 2017

Throughout the late 1800s and into the first part of the 20th century, central Arizona experienced a period of heavy grazing from cattle and sheep ranching. The Sierra Ancha Experimental Forest first began as a series of range exclusion plots established in the early 1920s to study the threat of erosion into the newly established Roosevelt Lake. Early pioneers in southwestern rangeland ecology including M.W. Talbot and C.K. Cooperrider took painstaking efforts to establish and record plant community characteristics within dozens of meter square survey plots scattered throughout the experimental forest.  What began as an erosion study quickly morphed into a plant demography study that was continuously monitored from 1920 – 1960.  Using advanced Geographic Information Survey (GIS) techniques we have begun to resurvey these historical plots and put them into a digital format which we can then use to compare vegetation changes through time.  Combined with the long-term climatological record for the experimental forest this work will shed light on how changes in climate and land use are affecting the ecology of the area.  The outcomes of this work will help establish a long-term record of rangeland changes and assist land managers in future decision making.

Sierra Ancha Experimental Forest current sampling frame and 1920s historical plot.
Sierra Ancha Experimental Forest current sampling frame and 1920s historical plot.

Approach

W.J. Cribbs uses a staff rod to measure the height of a shrub at Plot 3 in 1935 at the Sierra Ancha Experimental Forest
W.J. Cribbs uses a staff rod to measure the height of a shrub at Plot 3 in 1935 at the Sierra Ancha Experimental Forest
This study uses a methodology developed by Lauenroth and Adler (2008) to compare plant demography characteristics within a 1 meter square plot area using digital GIS techniques.  Plant surveys conducted from 1920-1955 on the experimental forest have been relocated and re-read using similar field methodologies and are then converted into a digital format for comparison.  One of the advantages of using a long-term dataset is that it allows for the investigation of key plant demographic traits such as survivability and life span which are fundamental elements in understanding the broader implications of influences such as the land management strategies or changes in climate on plant population dynamics.  Findings from this study suggest that that perennial species have decreased slightly over the last century while annual species have increased dramatically.  Plant basal area cover has increased as has species richness due in part to the spread of non-native annual and perennial graminoid species.  Overall we observed a shift in composition toward more conservative drought-tolerant and grazing-tolerant graminoid species.   

Natural Drainage Plot 10 through the years - 100 years of vegetation change at Sierra Ancha Experimental Forest
Natural Drainage Plot 10 from 1935, 100 years of vegetation change at the Sierra Ancha Experimental Forest

 

 

 

 

 

Key Findings

Findings from this study suggest that that perennial species have decreased slightly over the last century while annual species have increased dramatically.

Plant basal area cover has increased as has species richness due in part to the spread of non-native annual and perennial graminoid species. Overall we observed a shift in composition toward more conservative drought-tolerant and grazing-tolerant graminoid species. 

 

Other

For more information about the Sierra Ancha Experimental Forest and the research conducted there, please visit the Sierra Ancha Experimental Forest webpage.

 

 

 

 

To see an animated GIF of Natural Drainage Plot 10 through the years, click here.



Project Contact: 

Principal Investigators:
Margaret Moore - Northern Arizona University - College of the Environment, Forestry, and Natural Sciences

Co-Investigators:
Kevin Grady - Northern Arizona University - College of the Environment, Forestry, Northern Arizona University - College of the Environment Forestry and Natural Sciences

Research Staff:
Joseph Bogart - GIS support - Northern Arizona University
Wade Gibson - Graduate Research - Northern Arizona University - College of the Environment, Forestry, and Natural Sciences
Scott Massed - Botanist
Christopher Updike - Field Manager - Northern Arizona University

Funding Contributors:
Northern Arizona University
Rocky Mountain Research Station