Aspen Functional Types – a more management friendly classification
By Dale Bartos and Ron Ryel
Overview of talk
A functional classification of aspen to aid land managers
Use GTR-178 as a guide for classification http://www.fs.fed.us/rm/pubs/rmrs_gtr178.pdf
7 current aspen stand types in the Sierra Nevada.
Elaboration and refinement by Rogers, Ryel, et al.
What’s the problem? Aspen possesses an “essential uniformity…throughout its wide range” and that “there is always a successional tendency working in aspen stands” (F.S. Baker, 1925, p.2)
Photo: Wayne Shepperd
One size doesn’t fit all: • successional bias • timber bias • inappropriate application • ‘command & control’ vs. ‘adaptive management’
Why Functional Types?
Benefits: • ecological awareness • application/ intuitive • toward resilience
Functional Types = communities that differ markedly in their physical and biological processes and interactions
Meadow Fringe (Seral Aspen Community)
Riparian Aspen (Seral Aspen Community)
Upland Aspen/Conifer (Seral Aspen Community)
Lithic Aspen (Lava, Bolder, Talus)
Snowpocket Aspen (Stable Aspen Community)
Upland Pure Aspen (Stable Aspen Community)
Krummholz Aspen (Stable Aspen Community)
FT Framework
Quaking Aspen (Populus tremuloides)
Terrain isolated
Elevation/aspect limited
Colorado Plateau/mesa
Seral
Stable
Boreal
Parklands
Montane
TYPES SUB-TYPES
Riparian
SPECIES
Higher Elevation Aspen
Lower Elevation Aspen
FT Framework MONTANE Major Associates Minor Associates
Abies lasiocarpa; A. magnifica; Juniperus occidentalis; Picea engelmannii; Pinus contorta; P. jeffreyi; P. ponderosa; Pseudotsuga menziesii
Acer glabrum; A. grandidentatum; Abies concolor; A. grandis; Juniperus scopulorum; Larix occidentalis; Libocedrus decurrens; Quercus gambelii; Picea pungens; Pinus albicaulis; P. aristata; P. lambertiana; P. flexilis; Salix scouleriana Key differences:
• Topo: highly variable; slope & aspect
• Size: 10-100s ha • Precip: 379-1807 mm • Roots: bedrock confined • Dist: mixed/high severity
FT Framework TERRAIN ISOLATED Minor Associates
See Montane Major Associates
Key differences: • Topo: variable
• snowpocket: concave • lithic: flat/steep • avalanche: steep/narrow
• Size: 1-10s ha • Roots: bedrock confined; variable • Dist: stand replace – gap/phase; fire, insects/disease, avalanche
FT Framework RIPARIAN Major Associates Minor Associates
Abies magnifica; Picea engelmannii; P. pungens; Populus angustifolia;
Abies magnifica; Acer grandidentatum; Betula occidentalis; Picea engelmannii; P. pungens; Populus angustifolia;
Key differences: • Topo: mod./steep • Size: 1-10s ha • Ecohydrology: subsurface flow • Roots: water table confined • Dist: flood, beaver; occasional adjacent fire
Differences among aspen classes
Stand structure Stand dynamics Associated vegetation (Mueggler’s
community type work) Replacement by other species
(conifers) Growth potential as related to
environmental conditions Genetics unknown but may play a
part.
Why there are different classes
Physical environment • Air temperature • Soil types
Water dynamics Nutrient cycling
• Ecohydrology – water movement by plants and soil processes Snow pack melt EXAMPLE: Krummhols Movement of surface and subsurface EXAMPLE: Snow pocket aspen
Example Snow pack Melt Aspen
Krummholz
Example Snowpocket Aspen
Links to Management
All aspen stands are not the same • Management may differ by class • Need to know how different classes function
and how to best manage.
Management may differ depending on resource needs. • e.g. Harvest, grazing, wildlife habitat • Effective managmenent for different resources
may differ among aspen classes.
Links Cont.
Management practices alter community composition and function • Effect on nutrient cycling
Role of fire Role of turnover of trees and understory
composition. • Genetic diversity and reproductive type
(sexual vs. asexual) • Removal of understory vegetation –
more biomass in mature trees?
Examples Biomass shifts
Mueggler RNA
Summary
Does “one size fits all” ---successional/stable?
Functional classes of aspen more useful for management on a landscape scale.
Work is being done on refining initial functional classes by Rogers, Ryel, et al.
Feedback---ideas/suggestions