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WOODSHED ANALYSIS Addison County Five Towns. Analysis by Marc Lapin, Chris Rodgers, & David Brynn Winter/Spring 2009. Purpose. To model the forest landbase suitable for sustainable harvest of forest biomass, and to estimate low-quality wood production on that landbase. General Methods.
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WOODSHED ANALYSISAddison County Five Towns Analysis by Marc Lapin, Chris Rodgers, & David Brynn Winter/Spring 2009
Purpose To model the forest landbase suitable for sustainable harvest of forest biomass, and to estimate low-quality wood production on that landbase
General Methods • Determine forestland sustainability criterion that can be utilized for spatial modeling • Construct spatial model to evaluate the landscape • Calculate the low-quality wood growth on the suitable forest landbase by applying several forest growth estimates to the suitable acreage
Sustainability CriteriaApplicable to Spatial Modeling Ecological criteria for sustainability refer to forest health, productive capacity, soil and water, biodiversity, and carbon and nutrient budgets
Soils • Forestland Value Group Exclude two least productive groups, representing limited & very limited forestry potential (available from NRCS soils surveys) • Slope Exclude slopes >60% Separate slopes 30-60%, which may present sustainability/operability constraints
Water Quality and Wetlands • Exclude water bodies and wetlands • Exclude 75’ buffered area surrounding all water and wetlands • Fragile and ‘Significant’ Natural Communities • Exclude all lands above 2,500’ elevation • No reliable spatial data for significant natural communities, therefore exclude 10% of landbase to account for such features as well as for the forest access road network
Conserved Lands • Exclude all lands where timber extraction is legally prohibited • Separate publically owned lands from privately owned lands for information purposes • Conserved lands GIS layer, GAP Protection Level data utilized
Suitable Forestlands Results • 60% forested • 52% of forestlands suitable = 42,100 acres • 84% of suitable landbase privately owned • 9% forested landbase legally protected from extraction • 10% subtraction leaves 37,900 acres available
Excluded Lands by Criterion Percentages include ‘overlap’ among criteria • Water, wetlands & their buffers – 8.5% • Forestland value group – 36.6% • Elevation – 5.4% • Slopes >60% – 0.9% • Potentially unsuitable slopes – 9%
BRISTOL • Small amount of suitable forest • May be more than shown on less sloping parts of Hogback • Most public land in wilderness protection
LINCOLN • Large acreage of suitable private forest landbase • Large amount suitable public lands • Few areas with 30-60% slopes • Very small percentage with conservation easements
MONKTON • Some moderate-sized patches of suitable forest • Perhaps more than shown on less sloping areas of Hogback • Very small percentage with conservation easements
NEW HAVEN • Mostly farmland with some large wetlands • Very little suitable forest • Small percentage with conservation easements
STARKSBORO • Large acreage of suitable forest • Substantial amount of 30-60% slopes • Small percentage with conservation easements • Large amount of suitable public lands
Tree Growth Per Year • Leak et al. (1987) – Northern Hardwoods modeling • Intensively managed – 1.7 green tons per acre • Unmanaged – 1.2 green tons per acre • Sherman (2007) – based on FIA plot data • Addison County – 2.6 green tons per acre • Frieswyk and Widman (2000) – based FIA plot data • 1.25 green tons per acre • Frank and Bjorkbom (1973) – Spruce-Fir modeling • Best case scenario – 1.25 green tons per acre
Estimated Low-Quality Wood Amounts in green tons/year • Most conservative estimate = ~22,000 • Lowest growth rate, low amount low-quality • Very believable • Mid-range estimate = ~31,000 • Middle growth rate, low amount low quality • Perhaps, with more intensive management • High estimate = ~57,000 • Highest growth rate, high amount low quality • Not supported by recent data
Unanswered Questions • How much of the available and future wood in the woodshed is/will be low-quality wood whose ‘best’ use after harvest would be for burning? • What is the actual growth per year? • The models show substantial variation • Without intensive field data collection in a specific woodshed, we don’t know how reliable the estimates are for any actual landscape
Where to Place Confidence? • Leak et al. model for unmanaged forests and recent FIA-based estimates coincide rather closely • Sherman growth estimates appear too high • A whole lot depends on management intensity, which depends on balancing numerous values, not merely maximizing biomass for burning • Landowner choices are, perhaps, the greatest unknown
What to Continue Questioning • Can our forests provide us with large amounts of biomass for energy while continuing to provide the other ecosystem functions and services we expect and hope for? • Will landowners opt for more intensive management to strive for greater forest biomass? • As management proceeds over many decades, centuries, how much will the proportion of the low-quality wood supply diminish? • A role for coppice management?