Solar-powered weather stations and soil moisture sensors have been
installed at 19 of the SageSTEP study sites on plots where trees and shrubs have been cut or shredded, where prescribed burns have been applied, and on untreated plots. The stations measure:
- air temperature
- soil temperature and
- soil moisture
Soil temperature and soil moisture data are gathered at depths between 1 and 30 cm, reflecting an area from which trees, shrubs and grasses all draw water.
Information collected from these stations is being used to assess how treatments that kill trees and shrubs affect soil water availability and the spread of invasive species such as cheatgrass. In areas with healthy shrub and perennial grass understories, soil water availability can act as a limiting factor preventing the spread of cheatgrass and encouraging the growth of native species.
Treatments such as the mechanical removal of trees and prescribed burning increase the availability of soil water. If a strong shrub and perennial grass understory does not remain following such treatments, then soil water can become available to invasive weeds.
Preliminary evidence based on data gathered by SageSTEP researchers suggests that the mechanical removal of trees to prevent woodland encroachment will be less likely to promote cheatgrass invasion if performed in the early stages of encroachment while understory shrubs and grasses are still present. More information on this study can be found in Issue 13 of the SageSTEP News.
Results of related research can be viewed in PowerPoint presentations with audio using the following links: