Ongoing Vegetation Transects

The Ongoing Vegetation Transects database includes measurements of vegetation (cover, biomass, and/or density by species) for locations originally used in four experiments established by S. Clark Martin. Three of those experiments began in the 1950s and proceeded for approximately 10 years, with annual measurements of cover and biomass on permanently established plots. These experiments were designed to compare vegetation responses to different seasons of livestock grazing, the removal of velvet mesquite, and the spatial distribution of water developments for livestock use. The fourth experiment used a subset of the permanent transects from the previous three experiments and 30 new permanent transects to compare, on a large scale, the vegetation responses to continuous-yearlong grazing versus a three-pasture rotation grazing system called the Santa Rita Grazing System. This experiment lasted from 1972 to 1984, with measurements made every 3 years. Since 1991, Mitchel McClaran and his graduate students and assistants at the University of Arizona continue to measure cover, biomass, and/or density by species every 3 years on 131 transects that are a subset of the transects used in the Santa Rita Grazing System study and that are now included in the Ongoing Vegetation Transects database. 

All data collected on the 131 selected transects are available for download on this website. Specifically, the pages listed below provide:

• The measurement protocols
• Measurements of vegetation by species or species group made on the study transects for cover (since 1953), density (since 1972), fetch (from 2009 to 2012), grass basal diameter converted to biomass (since 2009)
• Figures for cover, density, and perennial grass biomass
• Ecological Site Designations for the study transects
• UTM coordinates for the study transects
• Photographs of the Ongoing Vegetation Transects for viewing and downloading (since 1957)
• The original Forest Service Studies FSRM 1706- 09, FSRM 1706-12, FSRM 1706-15, and FSRM 1706-25 during which the Ongoing Transects were established.

Data users are requested to acknowledge their use of the database in publications, research proposals, websites, and other outlets by following the Instructions for Use, Citations, and Acknowledgement.