Otting, Nick, and Danna Lytjen. December 2003. Steens Mountain Aspen Assessment and Monitoring: Final Report. Submitted to Bureau of Land Management (Burns District Office, Hines, OR) and Steens-Alvord Coalition (Portland, OR).
RELEVANT TO: |
MONITORING/ADAPTIVE MANAGEMENT FORESTS/LOGGING/RESTORATION |
DESCRIPTION OF DOCUMENT
This document records the results of a cooperative partnership: Burns District, OR BLM, the Steens-Alvord Coalition (a conservation NGO coalition) and the authors (Duckfoot Survey Company) to "quantitatively assess ecological integrity of selected quaking aspen...stands in the Steens Mountain Cooperative Management and Protection Area." (p. 1)
During one week in October 2003, 129 aspen stands were quantitatively assessed by two botanists using a rapid assessment method. "This study was designed to sample selected parameters quickly, allowing a broad area and range of stand types to be included." (p. 2).
The 129 aspen stands extended elevationally from a zone of overlap with juniper to high-elevation Krumholtz stands of aspen.
The methods included the following:
- Aspen stems were categorized as overstory [equal to or greater than 75% of mature stand height]; recruitment [equal to or greater than 2 m tall and up to 75% of mature stand height]; or understory [less than 2 m tall]. Recruitment trees are tall enough to be resistant to browsing by cattle, deer, or elk, and are considered to have good potential to become part of the overstory.
- Overstory senescence is "the percent of overstory trees that are dead or showing signs of decline, including many dead limbs, conks, or weeping cankers." (p. 2)
- Plots were located within the stand in a location typifying the stand. [Note: Were a "fairy ring" of recruitment stems to exist, belt transects could be used to estimate its extent. Such rings did not exist with these Steens Mt. stands.]
- Cover (separately for overstory, recruitment, and understory) and overstory senescence were recorded by visual estimates taken in a 5.62 m radius plot (100 m 2 ).
- Approximate date of initiation of the recruitment layer(s) was determined with an increment borer or by cutting through the base and removing a stem "cookie" from the bole. Growth rings were counted using a dissecting microscope after "cookies" were sanded and stained.
- Historic grazing records for the BLM allotments and historic precipitation records were obtained.
- A digital image and GPS plot data were taken at each stand.
MAJOR FINDINGS
- The number of plots and recruitment to overstory cover ratio were able to be determined for single tier, two tier, replacement, multi-age, Krumholtz, and nearly dead or recently burned stands.
- Single-tier stands included (a) senescent mature overstories with little recruitment, perhaps at risk of dying out; and (b) vigorous youthful overstories still allocating resources to overstory stems rather than to a new recruitment cohort.
- Presence of a recruitment layer was often a response to visible disease stress in the overstory.
- Dates of recruitment layers were characterized for most stands.
- Incomplete grazing history data did not allow for robust comparisons of grazing levels with stand structure.
- Stands in particularly poor condition were able to be identified. Some have compacted soils and heavily browsed root sprouts; two recently burned stands have 100% overstory and heavy browsing by cattle and elk. "Protection from herbivory would aid the recovery of these stands."
- The importance and utility of grazing histories, big game population histories and fire histories are highlighted; when they are incomplete, understanding of stand structures is impaired.
- "These methods allow for assessment of stand condition and detection of key changes in stand structure over time." (p. 7)
- "...[W]e recommend careful monitoring of overstory senescence and understory recruitment." (Pp. 7-8)
QUESTIONS THIS RAISES FOR THE THREE FORESTS
- Do the Dixie, Fishlake, and Manti-La Sal NFs have quantitative structural assessments existing for a large proportion of their aspen stands?
- Do the Three Forests have standardized, rapid assessment methods for determining the condition of their aspen stands?
- Could these rapid assessment methods be transferred via training to citizen groups interested in partnerships for monitoring? Note: the authors of this document indicate (personal communication) that "with some training and calibration, cover and senescence could be estimated by citizens, and even though age determinations of aspen are difficult, someone with basic wood shop tools and a dissecting scope can do it."
FOREST MANAGEMENT SIGNIFICANCE
- Rapid quantitative assessment of numerous aspen stands provides a basis for adjustment of management practices.
- If stand overstories are indeed becoming senescent, successful recruitment of understory sprouts may depend on limiting the relevant herbivory.
- The partnership of BLM, an environmental conservation group, and a botanical survey company to accomplish a rapid quantitative survey is notable and promising.