A Scientific Basis for Ecological Restoration and Management of Ponderosa Pine and Dry Mixed-Conifer

Forests of the Colorado Front Range

Context• Need for more information on range of variability in forest structure based on

environmental variability and interactions with disturbance regimes• Groupy/clumpy structure is an important difference between restoration

and fuel reduction treatments, but what are the mechanisms leading to groupy/clumpy structures and where most or least likely to be present on the landscape

• Desire to see restoration treatments create structural variability in site-appropriate ways in order to enhance forest resilience/sustainability

• Assist managers in developing site-specific desired conditions by describing “elements” of a restored forest and expected ranges of variation based on site conditions

• Guidance for implementation – how to incorporate concepts into treatment designs and marking practices

PurposeTo provide a scientific basis for restoration management and to facilitate consistent

application of restoration guidelines for ponderosa pine and dry mixed-conifer forests along Colorado’s Front Range

Ecologically Important Changes for Front Range PP and DMC Forests

• Fire is less prevalent on the Front Range currently than it was historically • The current forest is more dense than historical forest• There are fewer openings currently• There are fewer old, large trees on the landscape currently… less old-growth• Fire sensitive species such as Douglas-fir have increased relative to fire tolerant species such

as ponderosa pine• Even-aged condition more common currently• Surface fuel loads and ladder fuels are more abundant currently• Wildlife associated with open forest conditions (e.g. Pawnee skipper) has declined• Understory vegetation – loss of diversity and fire-dependent species• Invasive species such as cheatgrass are present in many cases currently• Current forest less complex and more homogenous

Historical complexity and heterogeneity in forest structure and composition conferred resilience…

Description of Historical Forest Conditions and Disturbance Regimes

Restoration Goals

To create forest conditions that are sustainable in the face of inevitable disturbance events and climate change

• Resilience not only to wildfire but also to insect and disease epidemics• Habitat for sensitive wildlife and game species• Clean air and drinking water and other ecosystem services• Recreational opportunities• Sustainable resource extraction for human uses and to support local

economies• Resilience to climate change

Begin with general concepts based on ecological forestry principles and forests as “complex adaptive systems”

• Natural disturbance processes – fire, insects/disease, lightning, etc… think about the way in which these processes influence forest developmental processes

• Forest developmental processes – tree mortality and regeneration dynamics in particular

• Environmental gradients – how disturbance phenomena and forest developmental processes are shaped by environmental factors such as moisture availability

Restoration Guidelines

Use natural patterns of tree mortality as a guide for restoration treatments• Low severity fire kills primarily younger trees – “bottom up” disturbance• Mixed severity fire may create openings• Insects often attack large trees – “top down” disturbance

Develop desired conditions that are site-specific and forward-looking• Importance of place, working with variation in environmental gradients, avoid one-size

fits all• Informed by historic range of variation but not constrained by them – importance of

anticipating climate change impacts and use of climate analogues

Consider natural distribution of forest composition and structure along environmental gradientsProviding descriptions of forest change across gradients in:• Elevation• Aspect• Slope position• “Shape of the land”• Soil characteristics• Latitude

Visualization tools….

Questions/Discussion

Questions/Discussion

TRMI from Jonas…

Accept a range of forest structural possibilities for any given site

Structure described according to density and dispersion…

Tree DensityLow High

Dis

pers

ion

Clum

pyU

nifo

rm

1 2 3

4 5 6

7 8 9

10

Forest Structural Archetypes at the 1/10 Acre Scale

Accept a range of forest structural possibilities for any given site

Possibility of “stand-level self-organizing aspects in which certain structurestend to perpetuate themselves and maintain a semi-static mosaic…” (Perry et al. 2011)

Table depiction of what we think were the most common structures by physiographic setting with narrative description; also illustrates range of conditions can be present

Manage for desired “elements” of forest structure across multiple scales• Tree groups/clumps, scattered individual trees, openings (grass/forb/shrub interspace)

Scale Elements Metrics

Plot(< 1 acre)

Trees (individuals and groups) Grass/Forb/Shrub interspace Snags/Logs/CWD Forest Floor (litter/duff)

Tree size (diameter at breast height, height), age, species, crown base height, insect/disease damage, distance to nearest neighbor, number of old trees (>150 years), number trees in groups, number of groups, distance between groups, range of structural archetypes (Figure x.) Percent interspace versus tree canopy, interspace size range, percent cover and type of cover, species composition Number per acre, size distribution, species, decay condition (sound versus rotten) Percent cover of litter and range of duff depths

Stand (1-100 acres)

Trees (individuals and groups) Openings

Average tree size, tree density (trees per acre, basal area), species composition, canopy cover, canopy base height, number of groups per area, size of groups, percent of trees as groups v. individuals Percent of stand in openings, size distribution, spatial arrangement

Project(100-1,000 acres)

Forest Stands Meadows/Shrublands

Percent forested area, stand size, cover type/species composition, variability from stand to stand in stand-level metrics Percent area in meadows or shrublands, functional group composition (herb/woody)

Landscape(1,000 – 100,000 acres)

Forest patches Non-forest patches

Patch size (grain size?), patch density (closed forest v. open forest), patch composition (e.g. aspen v. conifer), between-patch variability, connectivity among patches,

Consider landscape scale pattern-process linkages and context…

• How decisions at stand and project scales should be influenced by landscape scale, i.e. the landscape context

• Why important – wildlife, landscape functionality, etc. • Drivers of landscape pattern – physiographic template plus fire

Monitor and compare to dynamic (not static) reference conditions

Maintain treatments

Acknowledge uncertainty

Focus on restoring processes and meeting functional objectives• Prescribed fire• Understory restoration• Food web based approach, trophic interactions• Wildlife discussion

Restoration Strategies/Actions

Create openings – variable size and spatial arrangement

Favor fire tolerant species – ponderosa pine, especially on dry sites. Douglas-fir occurs more naturally on moist sites such as north-facing slopes, so leave there… Leave large, old trees – but no age/diameter cap Leave “defect” trees – important for wildlife and structural heterogeneity Target age and size classes that are overrepresented for removal – based on inventory data – ensure balance of age and size classes… Leave trees in groups Minimize edge – natural disturbances do not usually result in sharp edges but more often represent a continuum of effect whereby higher-density areas grade into lower-density areas which grade into openings.

Favor aspen

Maintain treatments

Translating general guidelines into actions

Implementation Guidance

How can guidelines/principles be operationalized?

• Use the density v. dispersion diagram and table showing historical distribution of archetypes to get an idea of range structural variation for a given physiographic setting

• Use knowledge of environmental variation and local landform variation to guide site-specific prescriptions and marking

• Discussion of photo guide of commonly encountered restoration situations, possibly including actual data

• Example prescriptions

GIS Technologies and Tools

Binning/Parsing the landscape according to physiographic settings based on digital elevation models

Visualization tools

Next steps• Continue development of implementation guidance section, working

with land managers• Reach out to individuals with specialized experience• Workshop with larger Front Range restoration community, summer

2013• Finish writing/editing• Publish late summer/early fall 2013• Possible follow-on documents with case-studies

Questions?