Transcript Important Findings from Site Productivity Research in

Biomass Harvesting and
Forest Site Productivity
Eric D. Vance
National Council for Air and Stream Improvement
(NCASI)
Biomass/Bioenergy Workshop
February 24-25, Houston, TX
Biomass Harvesting
• Emerging markets for
bioenergy
• Removal of biomass
previously left on site
• Shorter rotations
• Concerns over site
productivity, water,
wildlife
Sustaining Site Productivity by
Manipulating Site Resources
• Water, nutrients, sunlight
• Allocation of existing site resources
– Competing vegetation, root growth
• Increasing site resources
– Artificially removing biomass and nutrients
– Cannot always rely on natural replacement
Management Intensity
and Site Resources
Intensive
Extensive
Available
Resources
Resource
Capital
Intensive Utilization of Harvest Residues
in Southern Pine Plantations
M.H. Eisenbies, E.D. Vance, W.M. Aust, J.R. Seiler
Bioenergy Research (2009) 2:90-98
• 32 million Mg yr-1 residues
available in the South
• 50-85 Mg ha-1 on site after
stem-only harvest
• 45-60% increase in midrotation fertilization may be
needed to replace nutrients
if residues removed
South Carolina Wet/Dry
Harvest Study
(Virginia Tech, MeadWestvaco, NCASI)
Flat
Planted
Class II
Class I
Bedded
ity
it v
c
u
od
g
Class III
Harvesting Residue Disturbance
Residue-Soil Disturbance Matrix
H
o
yp
s
he
iz
ed
re
c
n
a
Pr
n
si
I
t
Heavy
Moderate
Minimal
Soil Physical Disturbance
Ten-Year Effects of Harvest Residue
Removal on Relative Rank of Stand
Biomass
Fall River Long-Term Soil
Productivity Project
Univ. of Washington, Weyerhaeuser, USFS, NCASI
• Conventional boleonly removal
• Total stem (boleonly to a 5cm top)
• Total-tree removal
• Total-tree + legacywood removal
• All cable-yarded
Fall River Study
Douglas-fir Age 5 Tree Volume Index
SVOL (cm3/1000)
30
25
20
15
10
5
0
BO
C
T
BO BO BO5 TT+ TT BOnoVC
C
Forest Service Long-Term Soil
Productivity Network
Core Sites
Affiliated Sites
Competing Vegetation:
A Critical Factor
Lake States Aspen
Nutrient Depletion and Rotation Length
• Deficiencies rare
• Older studies
– Multiple, short-rotation
cycles
– Concluded 10-15 yr
rotations sustainable
• Reduced soil/foliar Ca
on some sites
• Indices underdeveloped
Aspen in the Lake States
Nutrient Budgets for Whole-tree
Harvesting over 50 years
(Mineral soils (lb/ac); Minnesota GEIS, Grigal 2004))
Ca capital = 15,125
4000
3500
3000
2500
Inputs
Outputs
Capital
2000
1500
1000
500
0
N
P
K
Ca
Mg
Short Rotation Aspen on Sandy
Soils: A Worst-Case Scenario?
• < 1% Ca drain
–
(Grigal, 2004)
• Three 20-yr rotations
– < 5% Ca removed
• 1 ton/ac wood ash
The Forest Calcium Cycle
(Likens et al. 1998)
Over a Century of Forest Nutrition
Management in Scandinavia
•
•
•
•
Science-based
Forest productivity
Forest health
Nutrient imbalances
– Foliar, soil analysis
• Biomass harvesting
Intensive Harvest and Site
Productivity: What Do We Know?
• Many sites remarkably
resilient
• Little evidence for
productivity declines
• Preconceived notions often
incorrect
• Managers often know best
But, More Work is Needed!
• Sensitive sites
• Fundamental impacts
• Long-term, repeated
removals
• Indicators
• Prevention, mitigation
A Range of Management Intensities to
Meet Society’s Needs