Presentation on theme: "Revising Southern Sierran Forest Management: The Implications for Plants Malcolm North, USFS Sierra Nevada Research Center, and Dept of Plant Sciences,"— Presentation transcript:
Revising Southern Sierran Forest Management: The Implications for Plants Malcolm North, USFS Sierra Nevada Research Center, and Dept of Plant Sciences, UC Davis Upper Yosemite Valley from Colombia Point
Outline: 1. Some of the lessons from the Teakettle Experiment 2.The current stalemate in Sierran Forest Management 3.The proposed “Ecosystem Management Strategy for the Southern Sierra” 4.What are the implications for plants?
What are the best means of restoring forest ecosystems? Fire? Thinning? Both? And if a forest is thinned, what kind of prescription? 2003 Healthy Forests Restoration Act: "In carrying out a covered project, the Secretary shall fully maintain, or contribute toward the restoration of the structure and composition of old growth stands according to the pre-fire suppression old growth conditions” 1996 Sierra Nevada Ecosystem Project: Critical Findings “Although silvicultural treatments can mimic the effects of fire on structural patterns of woody vegetation, virtually no data exist on the ability to mimic ecological functions of natural fire.” Restoration and Forest ‘Health’
1) Teakettle Experiment’s location, design, and integrated sampling scheme Each plot is 200 by 200 m Total plots = 18 Thinning Level:Unburned Burn NoneControl (UN)Burn Only (BN) Understory CASPO thin (25 cm < thin <76 cm) Unburned/Thin from below (UC) Burn/Thin from below (BC) Shelterwood thin (25 cm < thin & leave 22 large t/ha) Unburned/Overstory thin (US) Burn/Overstory thin (BS)
Conceptual model used in the Teakettle Experiment Results presented in 38 peer reviewed publications (Dec. 2007)
How do thinning, fire and their interaction affect the ecosystem processes/health? Thin Only EffectPossible Reason MicroclimateIncrease extremesReduction in canopy Plant DiversitySignificant decreaseLitter and slash Invertebrate Div.Significant decreaseLitter and slash Carbon Store/RespireReduce/Big IncreaseLog removal/ Slash and litter Decomposition RateSlowsFragmenters work on slash Tree Growth/MortalityModerate increase/slightReduced density/yarding Food Chain ImportanceGeneralists (chipmunk)—none Specialists (flying squirrel)— decrease Change in seed comp. but not abundance Significant drop in truffles Available NitrogenDecreaseIncrease in soil decomposers from litter and slash Soil MoistureIncreaseReduced tree density
How do thinning, fire and their interaction affect the ecosystem processes/health? Fire Only EffectPossible Reason MicroclimateNo changeNo effect on overstory canopy Plant DiversitySlight increaseLimited impact on litter Invertebrate Div.No changeLimited impact on litter and slash Carbon Store/RespireSlight Decrease/No changeSome combustion/ Slash and litter Decomposition RateNo changeNo increase in moisture Tree Growth/MortalityNo changeLimited burn extent/low severity Food Chain ImportanceNo changeLimited burn extent/low severity Available NitrogenNo changeFew ceanothus burned Soil MoistureNo changeLittle change in tree density
How do thinning, fire and their interaction affect the ecosystem processes/health? Thin and Burn EffectPossible Reason MicroclimateIncrease small scale variabilityIncreased habitat heterogeneity Plant DiversityLarge increaseSignificant reduction in litter and slash Invertebrate Div.Large increaseIncreased habitat heterogeneity Carbon Store/RespireImmediate decrease than building/Reduced Combustion than tree growth/ Less slash-litter Decomposition RateIncreaseIncrease in moisture Tree Growth/MortalityLarge increase after 2 yrs/ Increase Nutrient flush, increase moisture/ Burn Food Chain ImportanceGeneralist—no change Specialist--decrease No change in seed abundance/truffles reduced Available NitrogenLarge IncreaseBurned shrubs Soil MoistureLarge IncreaseReduced tree density
Forest Understory Present Forest Conditions (Pre-Treatment): Water most important to herb cover and richness Indirect light and dry soil most important for shrubs
Control Unburned / Understory Thin Unburned / Overstory Thin Burn / No Thin Burn / Understory Thin Burn / Overstory Thin Bare ground (no litter layer; %) 7.82 c c c c b a Coarse woody debris (%) 8.61 ab a a 4.94 ab 3.34 b 8.50 ab Litter depth (cm) 3.22 a 2.89 ab 3.61 a 1.67 c 1.80 bc 0.71 d Transmitted direct light (mol.m-2.d-1) d c ab d bc a Transmitted diffuse light (mol.m-2.d-1) 2.20 d 2.94 c 3.82 b 2.14 d 3.20 c 4.22 a June soil moisture 0-15 cm (%) 13.9 abc 15.6 ab 19.1 a 13.0 bc 15.1 ab 12.9 c Total N, cm (%) 0.10 ab 0.11 ab 0.10 ab 0.09 b 0.12 a 0.11 ab Total C, 0-10 cm (%) 5.42 a 6.33 a 5.28 ab 4.36 ab 4.94 ab 4.24 b NH 4, 0-10 cm (ppm) 7.33 ab a 8.90 ab 5.57 b 7.97 ab 8.64 ab NH 4, cm (ppm) 2.25 c 4.00 a 3.32 ab 2.53 bc 2.76 abc 3.82 ab NO 3, 0-10 cm (ppm) 1.12 b 2.47 ab 3.54 a 0.90 b 3.47 a 4.19 a NO 3, cm (ppm) 0.13 b 0.41 ab 0.57 ab 0.14 b 0.41 ab 1.55 a P (Bray method), 0-10 cm (ppm) ab b a a a ab P (Bray method), cm (ppm) a a a a a a 4. How is the plant community affected by fire and thinning treatments?
What is the most effective restoration for the forest and its plant community? Get low-intensity fire back into the forest. Fire is essential. Thinning is a tool that should serve fire by increasing its extent and ‘work’. Reduce stem density and moisture stress. Currently plant diversity and many ecosystem processes are severely restricted by limited soil moisture Reduce litter and slash because it stalls most ecosystem processes and significantly reduces understory cover and richness. Provide for more large trees. Current forest, even old growth, has fewer large trees than under active-fire conditions.
Some of the road blocks: Concerns over thinning intermediate (20-30”) size trees? Does it affect fire behavior? Concerns over the impact of management practices on the Pacific Fisher Limited use of prescribed burning Many fuels treatment projects are stalled or take a long time to implement. Why?
An Ecosystem Management Strategy for Southern Sierran Mixed-Conifer Forests North, M., P. Stine, K. O ’ Hara, W. Zielinski and S. Stephens Much of current forest management is focused on landscape strategies intended to achieve immediate fuels reduction (e.g.., (SPLATs and DFPZs). These treatments have largely been developed with a short-term view, using fairly arbitrary diameter limits for mechanical tree removal. We have learned much in recent years, however, that can contribute to re-evaluating Sierran forest management strategies. We believe a more complete understanding of the ecological role of fire, fuel dynamics, sensitive wildlife habitat, and the importance of forest heterogeneity can help revise current silvicultural practices. A central premise of this paper is that the risks of carefully considered active management are lower than the risks of inaction in the Sierras’ fire-prone forest types.
An Ecosystem Management Strategy for Southern Sierran Mixed-Conifer Forests North, M., P. Stine, K. O ’ Hara, W. Zielinski and S. Stephens THE ECOLOGICAL IMPORTANCE OF FIRE: Mixed-conifer forests should be prescribed burned whenever possible. If an area cannot be burn, documenting the reasons for no burning may help inform the public about current limitations and the need for remedies LIMITED USE OF CROWN SEPARATION FUELS TREATMENTS: Reducing crown bulk density and increasing tree crown separation should be sparingly applied only to key strategic zones. SPATIAL VARIAION IN FOREST STRUCTURE:. Produce different forest conditions and use topography as a guide for varying treatments. Within stands, important stand topographic features include concave sinks, cold air drainages, moist microsites. Landscape topographic features include slope, aspect, and slope position.
An Ecosystem Management Strategy for Southern Sierran Mixed-Conifer Forests North, M., P. Stine, K. O ’ Hara, W. Zielinski and S. Stephens STAND-LEVEL TREATMENTS FOR SENSITIVE WILDLIFE: Areas of dense forest and high canopy cover will be needed for California spotted owls and Pacific fishers. We suggest identifying those areas as places where fire would have burned less frequently or at lower severity, due to cooler microclimate and moister soil and fuel conditions. SILVICULTURAL MODEL/STRATEGY: The frequency distribution of tree diameters in Sierran mixed-conifer forest subject to frequent low-intensity fire was highly variable but generally flat due to periodic episodes of fire-induced mortality and subsequent recruitment. Stand treatments should strive to significantly reduce the proportion of small trees and increase the proportion of large trees as compared to current stand conditions.
An Ecosystem Management Strategy for Southern Sierran Mixed-Conifer Forests North, M., P. Stine, K. O ’ Hara, W. Zielinski and S. Stephens TOPOGRAPHIC FEATURES CREATE DIFFERING CIRCUMSTANCES FOR STAND DENSITY AND THUS HABITAT CONDITIONS: Basic topographic features result in fundamental differences in vegetation composition and density producing variable forest conditions across the Sierra’s landscape. TREATMENT OF INTERMEDIATE SIZED (20-30”) TREES: In most cases thinning these trees will not affect fire severity and therefore other objectives for their removal should be clearly identified. Silvicultural prescriptions would only remove intermediate-sized trees when they are shade-tolerants on mid or upper slope sites. FIELD IMPLEMENTATION OF SILVICULTURAL STRATEGY: Marking rules are based on crown strata or age cohorts (a proxy for size/structure cohorts) and species rather than uniform diameter limits applied to all species.
White-flowered hawkweed Pyrola picta Corallorhiza maculata Pterospora andromedea ‘Pinedrops’ Some plants were sensitive to all disturbances
Malcolm North USFS Sierra Nevada Research Center 1731 Research Park Dr. Davis, CA Website: