Presentation on theme: "Silviculture Based on Natural Disturbances: Critical Reflections on Its Status and Future in the Northeastern United States Robert S. Seymour and Alan."— Presentation transcript:
Silviculture Based on Natural Disturbances: Critical Reflections on Its Status and Future in the Northeastern United States Robert S. Seymour and Alan S. White 5 th North American Forest Ecology Workshop June 14, 2005
Outline Definition Natural disturbance dynamics: brief review Status by Ownership Obstacles Simple Application Principles Personal Observations
My definition of “natural disturbance paradigm” = “Ecological Forestry” (Seymour and Hunter 1999)
Ecological Forestry defined “Using knowledge of natural disturbance regimes and ecological processes to make management decisions about …” Stand structure (vertical and horizontal) Rotations and cutting cycles Species composition Regeneration methods Other biodiversity issues
Don’t let “The Perfect” be the enemy of the “Good Enough!” Ecological mimicry is a downright threatening concept to production foresters challenged to produce value and commodities –They “tune out” in advance, because they know they cannot do this any where near perfectly About 1996, I stopped using “….emulating or mimicking natural disturbance regimes…..” and substituted “…learning from nature…” as the operative concept
Landscape-level Thinking, Maine ca. 1992: the TRIAD
Triad: Origin and Acceptance (ca. 1990-1995) Attempt to resolve seemingly irreconcilable conflict in Maine between: –Essentially no system of ecological reserves, –Predicted timber supply shortfalls Everybody endorsed 2/3 of the Triad Proved to be a great device for: –Legitimizing everyone’s agenda –Exposing everyone’s biases
Recent Evolution of “Balanced Forestry” In 1992, most people (but not me) said the “reserves” would be the hardest part Over a decade later, we have ecologically designed (though arguably inadequate) reserve systems in many places The management of “The Matrix” under dominant ecological principles – the silviculture -- has proven the be the real bottleneck (and focus of the rest of this presentation).
Ecology of Northeastern Forests: Gap Dynamics rule Natural disturbance regimes dominated by partial disturbances (some minor exceptions), long-lived shade-tolerant species Stand-replacing disturbances were rare
Estimated return intervals (years) of stand- replacing disturbances in the northeastern US (Lorimer and White 2003)
What silvicultural systems do these dynamics imply? Multi-aged stand structures, with a significant component of “old” trees Regeneration in gaps or patches within irregular stands Single-cohort (even-aged) silviculture –- where entire stands are regenerated in single cuttings -- would be the distinct exception (< 20% of the landscape under age 100) This is the bottleneck!
Status of Ecological Forestry (based on silviculture applied) Large Private ownerships (not under conservation easement or FSC certified): rare to non-existent. Practices range from traditional shelterwood (with prompt overstory removal and little retention), to heavy exploitative cuttings from above with no silvicultural intent.
Northern hardwood shelterwood on FSC certified private owner
Status of Ecological Forestry (based on silviculture applied) Public Lands (and some FSC certified private and NGO lands): Ecological forestry is more common, but the degree of “emulation” depends on forest type and land-use history
Status of Ecological Forestry (based on silviculture applied) Case 1: Acadian region (northern hardwood- spruce-fir types) –Northern New England, New Brunswick, Nova Scotia never cleared for agriculture Species composition altered somewhat, but largely intact Challenge is to restore diversity in age structure, esp. enhancing late successional stages
Group selection cutting – red spruce mixedwood, Baxter Park Scientific Forest Management Area.02-.04 ha gaps, 1/14 of the stand on 10 year cutting cycle
Status of Ecological Forestry (based on silviculture applied) Case 2: Central Hardwoods, Allegheny Hardwoods, Lakes States aspen Species composition highly altered from presettlement due to land clearing, repeated heavy cutting, wildfires. Present even-aged forest of early to mid- successional species (red oak, black cherry, white pine, aspen) is commercially valuable
Case 2: Central Hardwoods, Allegheny Hardwoods, Lakes States aspen (continued) Enlightened silviculture aims to perpetuate present forest via two-aged systems (shelterwood with reserves) In many cases, restoration of presettlement composition or structure not feasible, especially where deer populations are excessive (prevents gap regeneration, both in nature and under management).
Mature even-aged black cherry on Pennsylvania State Forest 2003 Timber sale = $8 million on 200 acres.
Shelterwood incomplete removal cutting on Massachusetts Wildlife Lands Oak and pine reserve trees
Group shelterwood (oak-pine) MDC Lands (Massachusetts) Gaps =.1 to 1 ha, 1/3 of the stand on 30-year cutting cycle
Status (summary) Modest developments, mostly on public forests and a few FSC-certified family ownerships (< 20% of forest area) Many 1990s initiatives on industrial lands have since been abandoned after ownership changes to shorter-term investors
What are the obstacles? The Science? The System? The Resource? The Profession itself? Political and Stakeholder Support ?
What about “The Science” “Applications” are documented in books (2004) Conservation biology enters mainstream forestry (1990)
Scientific Progress Since 1990, significant studies in disturbance ecology have led to useful, quantitative working hypotheses for most common forest types –Disturbance rates –Patch sizes (regenerated) –Structure Scientists have “rallied” – they’re largely not the cause for limited application
Simple Principles for Application (this is not rocket science!) Must regenerate new cohorts at a disciplined rate, keeping the matrix intact Guiding stand structure is based on AREA not size (e.g., dbh distribution) –Focuses directly on the dynamics, not static conditions Must also retain legacies (trees, patches) to restore late-successional characteristics –This is where structural goals are important
Natural Variation in Disturbances (based on ca. 20 studies; Seymour et al 2002 ) (based on ca. 20 studies; Seymour et al 2002 ) 1 Interval between Disturbances (at the same point on the landscape) - years Contiguous Area Disturbed and Regenerated - ha Severe Fire and Wind 100100010000 0.0001 0.001 0.01 0.1 1 10 100 1000 10000 Natural Canopy Gaps 100-year return interval Range =.001 -.1 ha
Clearcutting on a 100-year rotation? 1 Interval between Disturbances (at the same point on the landscape) - years Contiguous Area Disturbed and Regenerated - ha Severe Fire and Wind 100100010000 0.0001 0.001 0.01 0.1 1 10 100 1000 10000 Natural Canopy Gaps Severe Fire and Wind
Where do we turn for guidance? A Disturbance Chronology Canopy turnover by decade (for 6 forest types in an old-growth reserve, northern Maine; Fraver 2004) 10% per decade, or 1% per year
Formulating ecologically based silvicultural systems: regeneration rate 1.Forget the usual constraints of classical group selection systems (equal cutting cycles and balanced age structure) -- Nature is not this regular! The “1% rule”: Within the stand, area regenerated at each harvest should fall within natural disturbance boundaries –avg. = 10% per decade (range = 0-30%)
Comparison to unharvested old-growth Old-growth forests not balanced but bimodal, with “tail” of legacy trees Age structures old- growth red spruce stands (Fraver 2004) Old-growth legacy (100-300 yrs) Managed stand = 100 yrs
Formulating ecologically based silvicultural systems: patch size 2.Spatial arrangement of areas regenerated should also fall within natural limits –patch size =.01- 0.1 ha <<< stand size –Larger patches depart from the “natural” (but are still preferable to stand-wide uniform treatments) –Think in terms of fewer, larger stands with more within-stand diversity
Formulating ecologically based silvicultural systems: stand tending 3.Thin the matrix opportunistically, to: Presalvage short-lived species (aspen, fir, paper birch) Release crop trees of long-lived species BUT Make sure not to “over-regenerate” the stand as a whole, or harvest future legacy trees (resist uniform shelterwood). May be possible to do only once (first entry).
Formulating ecologically based silvicultural systems: biological legacy 4.Designate permanent reserve trees as a biological legacy in gaps as they are treated Maintains and restores late-successional conditions as regenerating groups enter stem exclusion
What do we call this? Combine the traditional advantages of uniform shelterwood with the ecological advantages of group selection Apply shelterwood with reserves, but in small patches within stands –Entire stand contains examples of all stages of the regeneration process –Age structure within stands varies spatially, not temporally = “Group Shelterwood (with reserves)”
Bob Wagner, Front Page of Bangor Daily News U. Maine Forest Ecosystem Research Program (FERP) – begun 1994
U. Maine Forest Ecosystem Research Program: The “Acadian Femelschlag” Expanding gap system based on three ecological parameters: 1% Annual Disturbance Frequency (20% per decade for 5 decades, then no regeneration for 50 years) Initial gap sizes average 0.1 - 0.2 ha (expanded on 10- year cutting cycle) 10% permanent structural retention, dispersed throughout the entire stand North American Translation: Irregular group shelterwood with reserves
Initial Groups 1995 2005 2015 2025 2035 40 30 20 10 0 Skid trail Age Distributions of Final Regeneration Harvest Age of Regenerated Stand Year of Harvest 200 m Entry #1
Expanding Gaps - 10 years 1995 2005 2015 2025 2035 40 30 20 10 0 Skid trail Age Distributions of Final Regeneration Harvest Age of Regenerated Stand Year of Harvest 200 m Entry #2
Expanding Gaps – 20 years 1995 2005 2015 2025 2035 40 30 20 10 0 Skid trail Age Distributions of Final Regeneration Harvest Age of Regenerated Stand Year of Harvest 200 m Entry #3
Expanding Gaps – 30 Years 1995 2005 2015 2025 2035 40 30 20 10 0 Skid trail Age Distributions of Final Regeneration Harvest Age of Regenerated Stand Year of Harvest 200 m Entry #4
Expanding Gaps – 40 years (Last) 1995 2005 2015 2025 2035 40 30 20 10 0 Skid trail Age Distributions of Final Regeneration Harvest Age of Regenerated Stand Year of Harvest 200 m Entry #5
Expanding Gap Profile (Acadian Femelschlag) First harvest (1995) Third harvest (2015) Fifth harvest (2035) the next 50 years.
Hemlock legacy tree Gap, 7 years after initial entry
Obstacles: The Resource? The challenge is RESTORATION, not maintenance –Most forests are now much younger and more even-aged than naturally Two Goals (both require PATIENCE!) 1.Re-create, on cutting at time, a forest dominated by multi- aged stands, some with strong late-successional features 2.Gradually rebuild stocking of long-lived, shade-tolerant (and valuable) species The problem is more complex than simply mitigating clearcuts or making single-cohort silviculture more biodiversity-friendly
Retention patches? Better than nothing, but not by much! Mature MW Stand, northwestern New Brunswick
Obstacles: Institutional In the US, large industrial ownerships rapidly changing hands to timber investment companies Immediate expectation of non-sustainable, double-digit rates of returns by short-term investors Ecologically, many of these forests just need a “rest”, yet many are only being cut harder and more frequently
Obstacles: Professional Practicality: Even-aged silviculture has tremendous appeal to overworked and under-funded foresters, regardless of how “unnatural” it may be, because it’s SIMPLE and PREDICTABLE.
Things that are relatively easy Buffering riparian zones, if mapped Designating large patches to cut Reserving large unmerchantable legacy trees Leaving reserves in isolated small patches (“islands”) Predicting future yields of even-aged stands Making “expedient” broad-brush even-aged regeneration prescriptions
Things that are difficult (but necessary) Marking individual trees to cut or retain Leaving dispersed reserve trees Screening areas for rare things Regenerating only 1% of the forest annually Regenerating only 10-20% of a harvest block Leaving significant areas of a harvest block untreated
Things that are difficult (continued) Leaving merchantable trees to die Predicting future yields of complex, mixed-species stands Taking the time -- and being rewarded -- for making a thoughtful, stand-specific, ecologically sensitive, balanced, silvicultural prescription that enhances diversity
Obstacles: Political and Stakeholder Support Presently in the US, meaningful application (= large-scale) must occur voluntarily on private lands –At best, regulations codify mediocrity, not reward excellence. –I see absolutely no prospect of enforcing ecological forestry via regulations (except perhaps for endangered species)
What about Green Certification? Rigorous, market-based certification (FSC, not SFI) -- the reward for doing all those “hard things” -- has failed to provide consumer- driven market incentives to “green up” management on private lands. Certification has arguably made the “good” even better, but has done little to force a larger-scale paradigm shift toward a more ecological forestry.
Personal Reflections on Ecological Forestry Obstacles are no longer scientific, but science alone does not provide a mandate! Disturbance ecology is no more or less “scientific” than old-fashioned production ecology that underlies plantation forestry –Not necessarily in conflict, if balanced at the landscape level Decision is really about human values: what do we (society) really want to sustain, and where? –Biodiversity –Free enterprise –Global competitiveness
Personal Reflections on Ecological Forestry I had hoped the forestry profession would embrace ecological forestry much more widely, in hopes of becoming popular again with people Unfortunately (for us) society has a double- standard: we don’t like our forests treated non-sustainably but we also want cheap forest products Conclusion: practicing Ecological Forestry, at present, is too costly, with no commensurate economic benefits
The Ultimate Irony? The more the forest landscape is dominated by commodity extraction, rather than long- term stewardship, the more public lands will be pressured to keep areas reserved from any cutting. –This is where the big, old trees are. Will we eventually lose our finest examples of long-term forestry in eastern North America (to reserves) so we can continue to exploit the rest under the doctrine of free enterprise?
The Ultimate Irony? The eventual consequence will be a global BIAD (like New Zealand) where wood and paper come from plantations somewhere else while our region’s forests are reserved and exploited opportunistically. Do environmental stakeholders really support ecological forestry everywhere? Or are they merely advocating that it replace production forestry on private lands?
Who is the real constituency for ecological forestry? If it’s viewed as an esoteric concept understood and embraced by only a small group of Type B foresters, academics, and scientists, then it’s doomed. We must find a way to articulate the benefits, and society must find a way to “pay” for it.
Will Ecological Forestry become a Dead End? It depends. Maintaining and improving long-term applications (via adaptive management) is SO important here! Such benchmarks are arguably as, or more, important than ecological reserves Do the best we can, whenever we have the opportunity, and hope society will eventually pay attention.