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