Stand Structure and
Ecological Restoration
Charles W. Denton
Ecological
Restoration Institute
John D. Bailey, Associate Professor of Forestry,
Associate Professor of Forestry, Northern Arizona
University, School of Forestry
Today’s Topics
•
•
•
“Stand Dynamics” and the role
of disturbance
Single vs. multiple species
Density and basal area
– Even-aged stands
– Multi-aged stands
•
•
•
Special stand structures, living
and dead
Scaling up spatially
Temporal variation and planning
Stand Dynamics
Regulates:
–
–
Age and size distribution =
even-aged vs. multi-aged stands
Vertical canopy structure/layers
–
Horizontal arrangement issues
Four basic stages:
•
Stand initiation
–
•
Stem exclusion (“thinning”)
–
•
Stand replacing event, growing space
Self-thinning, low diversity, zero g.s.
Understory reinitiation (“transition”)
- shifting mosaic
•
Old-growth
Presettlement Age Distribution
in Northern Arizona
trees/ha
Ponderosa pine age distribution at 1876
18
16
14
12
10
8
6
4
2
0
70
180
250
310
age (years)
Mast et al. 1999
Single vs. Multiple Species
Mix and ratios based on:
• Disturbance type (e.g., fire)
• Shade tolerance
–
Initiation vs. transition
• Management preferences
• Spatial arrangement issues
Presettlement Ponderosa Pine
Spatial Distribution
Gus Pearson Natural Area
width of circle indicates age
Covington et. al., 1997
Current conditions at the Gus Pearson Restoration site
Diameter Distribution
Fort Valley, Arizona
200
current
predicted residuals
trees/ac
150
100
50
0
2
6
10
14
18
diameter class (in)
22
Kathy Smith’s thesis 1999
S9
S10
Interpreting Density Measures
• Trees per acre
– Little use in multi-aged
• BA and SDI
– Workable, particularly at
extremes
• Canopy closure
– Aerial fuels and growing
space
Hypothetical Results of a BDQ 14-50-1.2 Treatment
S9-10 Before Treatment
S9-10 After Treatment
Implications
• Multi-aged is ‘historically
accurate’
• Group selection created
“clumpiness” relative to
individual-tree selection
• Must revisit the sites regularly
- the 1919 cohort is now a real
problem
• VSS distribution
• Mistletoe does not have to be
a concern
Special Structural Elements
• Large, old trees
–
Not “old-growth” trees
• Vigorous lower and midcanopy trees
–
True advantage of multi-aged
• Snags and aerial dead wood
–
Wildlife habitat value
• Downed, coarse woody debris
–
Ecosystem value
ALL have their limits!
STIFH Treatment Gradient
Unburned
Control
Thinned
Burned
Thinned
Wildfire
and
Burned
Disturbance Gradient
Forest Health “Indicators”
• Overstory structure and
growth/vigor
• Fuel loading
• Understory composition
• Insect diversity
• Soil nitrogen
• Ectomycorrhizal fungi
• Wildlife use
Scaling up spatially
welcome to “ecosystem management”
• Three fundamental scales
for diversity:
–
–
–
Within stand
Among stands
Landscapes, watersheds and
fragmentation
• Stand inequality is good
ALL have their role!
Temporal Scales
•
•
•
•
Trees grow
Disturbance happens
Trees grow
Stands change somewhat
predictably given stand
dynamics, but often
unpredictably
• Trees grow
…Adaptive Management!
Fire mortality
1999 data collection
REGENERATION
• Adequate in most decades
– seed tree density and
production
– seedbed and germination
– mortality, particularly with fire
• More likely TOO MUCH
• Some decades may be
insufficient, but that’s OK
Concluding Remarks:
Structure and Restoration
• It’s ALL about structure
• Multi-aged is often the way,
but more complicated
• Promote small trees, too
• Spatial heterogeneity
• Diversity at all three scales