Title:
E COSYSTEM R ESPONSE TO A SPEN R ESTORATION SNPLMA R OUND 12
Pile burning in aspen stand at Ward Creek. October 2011 .
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Ecosystem Response to Aspen Restoration
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Subtheme this proposal is responding to
Principal Investigator and
Receiving Institution
Co-Principal Investigator
Agency Collaborator
Grants Contact Person
Funding requested:
Total cost share (financial and in-kind contributions):
Watershed, Water Quality and Habitat Restoration subtheme 2c:
Increasing our understanding of special status species and communities
Dr. John-Pascal Berrill, Assistant Professor
Department of Forestry and Wildland Resources
Humboldt State University
1 Harpst Street, Arcata, CA 95521-8299
Phone: (707) 826-4220; Fax: (707) 826-5634
Email: pberrill@humboldt.edu
Dr. Christa M. Dagley, Research Associate
Department of Forestry and Wildland Resources
Humboldt State University
1 Harpst Street, Arcata, CA 95521-8299
Phone: (707) 826-1220; Fax: (707) 826-5634
Email: cd104@humboldt.edu
Stephanie Coppeto
Ecosystems Conservation Department
USDA Forest Service, Lake Tahoe Basin Management Unit
35 College Drive, South Lake Tahoe, CA 96150
Phone: (530) 543-2679; Fax: (530) 543-2693
Email: sacoppeto@fs.fed.us
Dr. Steven Karp, Director
Sponsored Programs Foundation, Humboldt State University
1 Harpst Street, Arcata, CA 95521-8299
Phone: (707) 826-4189; Fax: (707) 826-4783
Email: Steve.Karp@humboldt.edu
$ 69,714
$ 17,443 (20% of total project cost)
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E COSYSTEM R ESPONSE TO A SPEN R ESTORATION SNPLMA R OUND 12
A .
P ROJECT A BSTRACT
We are requesting funds to continue monitoring one-hectare permanent plots installed in nine coniferencroached aspen stands around the Tahoe Basin. Thinning of encroaching conifers has been completed at six sites, and should occur in 2012 at the other three sites. Additional funding will allow us to continue monitoring for up to five years since restoration thinning and three years since pile burning, giving time to assess ecosystem response. Before thinning, aspen and conifer trees were measured for size and their health status assessed. A total of 3,752 trees have been tagged, mapped, and measured. Post-thinning assessment has been completed in thinned stands, giving number of trees cut and records of damage to the remaining trees. Aspen and conifer regeneration has been quantified pre- and post-thinning. Over
3,000 conifer seedlings and 3,000 aspen suckers have been counted in subplots (e.g., Fig. 1) to analyze regeneration patterns. Existing data shows that thinning intensity differed widely between sites. Between
33% and 82% of trees have been cut, but these were the smaller trees, so ‘crowding’ (in terms of stand density index) was only reduced by 8% to 63% between sites. Since we measured pre-treatment crowding
(indicator of stress) and intensity of thinning, we are able to correlate these with ecosystem response in terms of regeneration, growth, and stem breakage (wind/snow damage). Ecosystem response to pile burning will also be examined. Cut conifer wood, branches, and debris have been piled for burning in small, medium, and large piles. The piles were burned at one site in fall 2011, and damage noted. The products of our study will directly support adaptive management in restoration and inform conservation of aspen communities in a changing climate by describing the biology and ecological processes underlying observed responses to restoration and external factors such as changes in water supply.
B .
J USTIFICATION S TATEMENT
The proposed research project directly addresses subtheme 2c “Increasing our understanding of special status species and communities” by providing information on aspen forest community responses to restoration activities and external factors (i.e., changes in water supply). Monitoring responses to restoration thinning and pile burning will provide all participating agencies with a determination of the effectiveness and success of their restoration treatments. The monitoring at nine sites (receiving different treatments by different agencies) will highlight successes and reveal problems, supporting adaptive management in future restoration treatments and ongoing conservation. For example, post-treatment assessment of one stand revealed that 40% of aspen trees were missing, presumably damaged by the thinning of encroaching conifers and then removed by the contractor. The agency collaborator was contacted, and will adjust future prescriptions and contract management accordingly.
Studying the growth, health, and regeneration patterns of aspen and conifer in different stands will inform future conservation and restoration: monitoring stands with different disturbance histories, severity of encroachment, thinning methods, thinning intensities, and pile burning treatments will reveal key factors or mechanisms contributing to the enhancement or decline in growth and vigor of the remaining aspen forests. Our most recent finding is that presence of aspen regeneration is significantly, negatively related to stocking of neighbor trees and proportion of neighbors that are conifer. Proposed future re-measurements of regeneration growth rates would allow for complete analysis of regeneration patterns and dynamics in restored aspen stands. Current dendrochronological analysis of aspen growth rings is revealing that growth almost doubled in the season after record snowfall. This observation needs to be quantified and examined in relation to elevation, location (N,S,E,W shores), tree size, and crowding, which is feasible given the data we have already collected. We have initiated a ‘pilot’ test (proof-ofconcept) in collaboration with USFS LTBMU to study effects of pile burning in one aspen stand.
Repeating these methods within our other monitoring plots has several benefits: our analysis would be strengthened by data from different sites; trees adjacent to burn piles have already been tagged, measured, and pre-existing health and damage assessed; and records of pile location and measurements of pile size and fuel composition will help explain future change and response to restoration activities.
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E COSYSTEM R ESPONSE TO A SPEN R ESTORATION SNPLMA R OUND 12
In summary, the proposed research project:
(i) Uses an existing permanent, long-term monitoring plot network;
(ii) Incorporates burn pile data that allows for long-term monitoring;
(iii)
(iv)
Analyzes monitoring data to evaluate, model, and predict change;
Develops guidelines for design of thinning and pile-burning prescriptions.
The analyses culminate in development of several products, including:
(i) Spreadsheet-based pile burning assessment model to support decision making;
(ii)
(iii)
(iv)
Science-based recommendations for thinning and pile burning;
Additional tests of concept (pile re-vegetation) and core data (climate & growth);
Peer-reviewed manuscripts describing methods and results.
These products will be developed from analysis of thousands of tree size and growth data, tree health and damage records, regeneration data, and increment cores from different locations, elevations, and treatments in aspen communities of the Tahoe Basin.
C .
B ACKGROUND AND P ROBLEM S TATEMENT
Quaking aspen communities throughout the Tahoe Basin are being encroached by conifers. Aspen depends on high light levels to regenerate and maintain vigor (Perala 1990). Shade-tolerant conifers grow under the shade of aspen tree crowns, and eventually overtop them (Shepperd et al. 2006). Aspen trees that are crowded and overtopped by competitors lose vigor, with an associated decline in pest and disease resistance. In a clonal species such as aspen that regenerates mainly by vegetative root suckers, loss of vigor among existing stems will lessen carbohydrate storage within root systems (DeByle and
Winokur 1985). Entire aspen clones with depleted energy reserves could succumb to major disturbances or changes in climate (Rehfeldt et al. 2009). Thinning of encroaching conifers relieves crowding in aspen stands, but may have unintended consequences. Heavy thinning may predispose older stems with habitat value (e.g., cavities for nesting) to wind throw or breakage under heavy snow loads. In remote and roadless areas, thinning of conifers generates large volumes of cut wood that cannot be extracted.
Besides leaving the cut wood in place and risking catastrophic wildfire, the only options are to either carry the wood into openings outside the aspen stand (costly), or pile and burn the wood in the stand.
Throughout the Basin, conifer trees encroaching aspen stands are being cut and piled for burning inside aspen stands (EIP Project #10080: Aspen Community Restoration Projects). However, the effects of pile burning on aspen are unknown. Soil heating from pile burning of cut conifers will kill fine aspen roots, while the flames and heat will kill adjacent aspen trees or provide entry points for pests and disease agents. However, these disturbances may stimulate regeneration and release nutrients otherwise bound up in conifer biomass and litter. Calder et al. (2011) found six times higher nutrient concentrations in soils of aspen-dominated stands versus adjacent conifer-dominated stands. Pile burning appears to be an efficient solution for disposal of cut conifer wood but is unlike fast-moving ground fire or any other natural disturbance pattern or process in aspen stands. These unknowns highlight the need for monitoring of ecosystem responses to thinning and pile burning in aspen stands. Analysis of monitoring data would inform the design of thinning and pile-building prescriptions; specifically, maximum thinning intensity, maximum burn pile size, and minimum safe distance from live aspen trees of any size.
Removal of encroaching conifers will be an ongoing task, and disposal of cut wood an ongoing challenge.
Even if all encroaching conifers are removed from every aspen stand around the Basin, future invasions are inevitable. Mature conifer trees remaining within and around aspen stands provide a steady seed source, and their seedlings establish well in the absence of ground fires. Safe re-introduction of frequent light ground fires is the ultimate goal and economical solution to conifer encroachment. Before ground fires can be re-introduced into the ecosystem, most of the encroaching conifers must be removed, and fuel
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E COSYSTEM R ESPONSE TO A SPEN R ESTORATION SNPLMA R OUND 12 loads reduced. The process of restoring aspen communities to a fire-safe and healthy condition will require multiple repeat treatments on most ownerships, for three reasons: (i) cutting all conifers in one operation would create too much cut material in most aspen stands where access is limited, especially when combined with existing down logs and debris; (ii) cutting all conifers in one operation would also predispose the already-weakened aspen trees to catastrophic disturbance from wind and snow, and; (iii) there is no scientific evidence (e.g., monitoring data) to support Tahoe Basin agency planning documents prescribing heavier thinning or burning of larger piles.
We used our pre-treatment monitoring data to calculate live conifer stemwood volume in an aspen stand at Ward Creek. Conifer volume totaled 422 m 3 ha -1 (6030 ft 3 ac -1 ) before thinning in fall 2009 to a diameter limit of 14 inches dbh (Fig. 2). The thinning treatment will be short-lived; it reduced stocking by only
24% yet generated over 70 m 3 ha-1 (1000 ft 3 ac -1 ) of cut conifer stemwood (not including branches and tops) (Fig. 3). Cut conifer was piled for burning in 124 piles ha -1 (50 piles ac -1 ) (Fig. 4; Berrill and Dagley
2010). The piles were dangerously close together (covering 8% of total ground area) yet only ~1/6 th of conifer wood volume was cut and burned. Therefore, over 350 m 3 ha-1 (5000 ft 3 ac -1 ) of live conifer biomass is still present, and continues to grow (and regenerate). A similar intensity of thinning will need to be repeated multiple times to remove the remaining conifers at Ward Creek. Thinning was much lighter at two other monitoring plots in Christmas Valley. It follows that multiple thinning treatments will be required in many/most aspen stands around the Tahoe Basin; an ongoing challenge that would be well supported by our monitoring data and results.
Tree growth rate estimates allow for prediction of ‘treatment persistence’, the time taken for a stand to return to pre-treatment condition or an undesirable state of crowding. Indicative growth estimates will suffice for most planning applications. The only relevant growth model for trees in the Tahoe Basin is the
Forest Vegetation Simulator (FVS). This model has a Western Sierra Nevada variant, however coefficients for aspen are the same as for all the California oaks, madrone, tanoak etc. – essentially it groups aspen with all other hardwoods found in the Sierra Nevada foothills and above. Independent growth data are needed to validate the FVS model, and the new Aspen Stocking Assessment Model (currently under development for SNPLMA Round 10 Science project; planned date of completion January 2013). The
Stocking Assessment Model is being developed to support agency planning; it is a spreadsheet calculator that combines various models predicting incidence of aspen and conifer regeneration, crowding, and structural changes over time since restoration thinning.
Quaking aspen is considered a keystone species (Shepperd et. al. 2006). It is one of only a few broadleaved trees in the Tahoe Basin. Issues such as providing wildlife habitat, aesthetics, water quality, natural firebreaks, and sustaining rich diverse understory plant communities and ecological processes are driving the interest in conserving and restoring aspen stands. Understanding the effects of restoration activities, natural disturbances, and climate change requires rigorous monitoring and scientific inquiry.
D .
G OALS , O BJECTIVES , AND H YPOTHESES
G OAL
The main goal of our project is to provide managers with guidance on conservation and restoration of aspen ecosystems by providing an understanding of their biological responses to disturbances and the ecosystem processes affecting them in the Tahoe Basin.
O BJECTIVES
Specifically, our objectives are to:
1.
Evaluate ecosystem response to recent restoration activities (thinning, pile burning)
2.
Monitor aspen tree injuries, health, and survival in restored stands
3.
Identify and describe mechanisms contributing to the decline of aspen (e.g., drought)
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E COSYSTEM R ESPONSE TO A SPEN R ESTORATION SNPLMA R OUND 12
4.
Pilot test different burn pile re-habilitation prescriptions
5.
Describe techniques and strategies for the long-term conservation of aspen communities
H YPOTHESES
1.
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COSYSTEM
R
ESPONSE TO
R
ESTORATION
Aspen tree response to thinning
Aspen tree growth rate increases after thinning, according to size of tree crown
Aspen tree response to thinning is delayed in stressed, severely encroached stands
Heavier thinning is followed by more wind damage (tree fall, stem breakage)
Wind damage is lower among healthier, more vigorous trees with full crowns
Older aspen trees with cavities or stem scars are more likely to suffer wind damage
Aspen tree response to pile burning
Aspen tree growth slows among trees scorched/injured by pile burning
Discoloration of aspen stems from pile burn heating leads to cambium death (Fig. 5)
Aspen trees do not survive when cambium death exceeds 1/3 stem circumference (Fig. 6)
Piles of larger logs have shorter flame lengths and injure fewer aspen than piles of smaller, flashy branch materials
Aspen regeneration
New aspen regeneration is more abundant and vigorous after heavier thinning
Less aspen regeneration arises after thinning in stressed, severely encroached areas
Pile burning is followed by a pulse of new aspen regeneration (outside burn patch)
Inside burned patches, aspen regeneration is delayed.
Conifer regeneration
New conifer seedling regeneration is more abundant in years after heavier thinning
Conifer seedlings establish preferentially on bare soil exposed by restoration activities
2.
E COSYSTEM R ESPONSE TO E XTERNAL F ACTORS
Aspen tree growth (from annual growth rings) relates to previous winter’s snowpack
Aspen growth relates to disturbances upslope/upstream (thinning/wildfire)
The individual hypotheses listed here are all testable given the data and core samples already at hand and the new data we propose to collect within existing monitoring plots.
E .
A PPROACH , M ETHODOLOGY AND L OCATION OF R ESEARCH
A PPROACH
The general approach is to minimize cost and maximize yield of useful information by using existing data and re-visiting existing sample plots. We will re-measure existing permanent monitoring plots to collect new data on tree growth and regeneration, assess changes in tree survival, health, and wind damage. We will also undertake a dendrochronological analysis of an existing collection of aspen increment cores, and relate annual growth rings to external factors that likely affected growth, such as snowpack and local disturbances that made more water available for aspen communities. The proposed study builds on recent aspen restoration work in the Tahoe Basin (SNPLMA Science Round 10: Stocking Guidelines for
Aspen Restoration). Permanent monitoring plots at nine study sites in conifer-encroached aspen stands scheduled for thinning have already been installed (e.g., Fig. 1). Tree locations within the large 1-ha (2.5ac) plots have been mapped using survey equipment, and the trees have been measured for size and their
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E COSYSTEM R ESPONSE TO A SPEN R ESTORATION SNPLMA R OUND 12 health status assessed. Thinning of encroaching conifers has been completed at six sites, and should occur in 2012 at the other three sites. Cut conifer wood, branches, and debris have been piled for burning, and piles burned at one site in fall 2011.
M ETHODOLOGY
1.
A NNUAL R E MEASUREMENT OF P ERMANENT M ONITORING P LOTS
Assess survival, health, and damage for tagged trees in all monitoring plots.
Re-measure tree dbh and quantify growth on per/year basis.
Count aspen and conifer regeneration in all subplots (total of 230 subplots at 9 sites; Fig. 1), and graph change in species composition and relative abundance over time.
Re-measure saplings in subplots and in adjacent open areas that were tagged and measured posttreatment, and relate height and dbh growth to existing summary data for tree composition and stocking around each subplot (from GIS analysis).
2.
P ILE B URNING A SSESSMENT IN P ERMANENT M ONITORING P LOTS
Map location, and record burn pile diameter, height, shape, fuel size class composition, and packing ratio. Estimate pile biomass using hand-/machine-piled fuels biomass calculator (Wright et al. 2009).
Install colored stake chasers 2m from each pile edge in cardinal directions (N,S,E,W), and assess vegetation cover in quadrats from the pile edge outward in each direction. Count and measure size of adjacent trees, saplings, and regeneration.
After pile burning, measure area of stem discoloration and extent of scorch on aspen trees. Re-install numbered tag for each pile at center of pile (for future assessments).
Pile burn rehabilitation experiment: divide selected burned patches into quarters, and apply experimental treatments: (i) turn over soil to loosen and incorporate ash; (ii) shovel soil (mycorrhizae and herbaceous seedbank) from adjacent unburned area on top of burned soil/ash; (iii) combine treatments i & ii; (iv) no treatment (Korb et al. 2004).
In spring following pile burn, and annually thereafter, return to inspect tree injuries and assess mortality (dead aspen will not ‘leaf out’ in spring). Relate mortality/injury to pile size, tree size, and pile-to-tree distance. Develop pile construction guidelines.
Assess herbaceous vegetation cover and diversity in experimental pile rehabilitation treatments
(adding soil v. cultivating soil) for factorial analysis of soil treatment and interactions on re-vegetation of burned patches.
3.
D ATA A NALYSIS
GIS analysis of localized neighbor competition (stocking, composition) around regeneration subplots and every aspen tree in all plots before and after thinning. Calculate crowding (stand density index) and percent conifer composition within fixed radius of all trees.
Logistic regression analysis of probability of wind throw or stem breakage as a function of thinning intensity, severity of encroachment prior to thinning (localized and stand level), tree size (proxy for age), and presence of pre-existing health problems or damage.
Regression analysis of regeneration growth rate in years following thinning and pile burning, testing for significant explanatory variables (e.g., burn injury, competition).
Logistic regression analysis of aspen injury/mortality as a function of pile size, pile composition
(flashy/mixed/large logs), distance from burn pile, cosine-transformed pile-to-tree azimuth related to wind speed and direction at burning, and tree size.
Validate FVS growth model predictions for Tahoe Basin aspen-conifer stands by comparing actual and predicted growth data. If FVS performs poorly, perform non-linear regression analysis of factors affecting growth, and develop predictive growth models for aspen and conifer trees of all sizes, including parameters for elevation and geographic location.
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E COSYSTEM R ESPONSE TO A SPEN R ESTORATION SNPLMA R OUND 12
Validate preliminary growth models in Aspen Stocking Assessment Model (being developed for
SNPLMA Round 10 Science project; planned completion January 2013); revise models as needed.
Multiple linear regression analysis of core sample growth ring width data: express annual crosssectional area growth as percentage of average growth over five-year period, and regress against percent above- or below-average snowfall/snowpack in preceding winter, presence/absence of disturbance upslope or upstream (wildfire/thinning), and neighbor tree competition and species composition (to account for internal and external factors affecting tree growth).
L OCATION OF R ESEARCH
The proposed study will take place within the existing nine 1-ha permanent monitoring plots. Table 1 lists ownership and location, pre-treatment trees/ha, treatment method and intensity, and a schedule of proposed future tasks. The additional work covered by this proposal is shown in bold (Table 1).
Table 1: Summary of monitoring sites: ownership, location, thinning and measurement history ( grey shading indicates completed task ). F unding is requested for proposed future tasks shown in bold ( e.g., S13
= summer 2013; F14 = fall 2014 ).
Management unit code
Ownership/management agency
Location (West, South, East shore)
Elevation (ft)
Pre-treatment density (trees/hectare)
Number of trees >10cm thinned (% of total)
Thinning intensity (% stocking cut)*
Prescription (Hand/Mech. Thin)
Plot Installation, pre-treatment data
Thin and pile (agency contracts)
Post-treatment assessment
Initial regen. growth measurement
Repeat regen. growth measurement
WA38 BP2 BC20 CV05 CV06 SSP24 SHC01 NC03 TC01
USFS CTC USFS USFS USFS USFS USFS NDOW NDOW
West West West South South South East East East
6672 6248 6468 7365 7400 7101 6658 7360 7130
589 705 576 665 438 852 802 689 593
56.0
31.0
H
S09 S10
F09
S10
M/H
? 82.1 52.5 32.6
? 63.2 19.8
S12
S13
F10 F12
F11 F13
M
S10
S11
S11
F12
F13
H
S09
F10
S11
F11
F12
H
8.2
S09
F10
S11
F11
F12
?
?
M/H
S09
S12
S13
F12
F13
58.0
28.5
H
S10
F10
F11
F12
H
?
?
S10
F11
S11 S12**
F11
F12
M/H
?
?
S10
S12
S13
F12
F13
Tree growth re-measurement
Annual tally of subplot regeneration
Burn piles: map & measure
Pile burning + pre-treatment assessment
S12+
S11+
S12+
S12+
S10 S14
F11 F14
S12+
S12+
S12
F13
S12+
S12+
S12
F12
S12+
S12+
S12
F12
S12+
S12+
S14
F14
S12+
S12+
S12
F12
S12+
S13+
S13
F13
S12+
S12+
S14
F14
Post-burn injury/survival asssessment S12 - S14 S13 S13 - S13 S14 -
*Stocking in terms of stand density index (SDI); indicates ‘crowding’. **2-phase treatment assessed F11 after 1st partial thinning.
Analysis of increment cores will initially focus on the above-average winter snowfall of 2005-06 related to growth in 2006 at four sites (N,S,E,W shores). Cores taken at Sugar Pine Point State Park in an aspen stand directly downhill from an area thinned in 2002 and pile burned in 2005 will be examined for response. Cores taken upstream and downstream from the 2002 ‘Showers Fire’ at Christmas Valley will give response in the years following the wildfire (downstream trees) compared to tree growth upstream where no response would be expected.
F .
R ELATIONSHIP TO E XISTING R ESEARCH , M ONITORING , AND E NVIRONMENTAL I MPROVEMENT
The Principal Investigator (Dr. Berrill) and Co-PI (Dr. Dagley) are currently collaborating with agency land managers actively engaged in aspen restoration activities: Stephanie Coppeto (Project Leader, Aspen
Community Restoration Project), Duncan Leao (Forester-Vegetation Planner, South Shore Fuels
Reduction and Healthy Forest Restoration Project), Judy Clot (California Tahoe Conservancy), David
Catalano (Wildlife Biologist III, Nevada Department of Wildlife), Dave Marlow (Management Analyst III,
Nevada Division of State Lands), and Tamara Sasaki (Resource Ecologist, California State Parks). Our
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E COSYSTEM R ESPONSE TO A SPEN R ESTORATION SNPLMA R OUND 12 collaboration with these land managers focuses on the monitoring of aspen restoration treatments, and providing updates of the associated scientific inquiry. Reports summarizing (i) pre-treatment assessments of nine aspen stands prior to conifer removal treatments; and (ii) preliminary stocking guidelines for aspen restoration have already been prepared and disseminated.
The proposed research has been designed to build on three existing studies in the Tahoe Basin (SNPLMA
Round 9: Hubbert & Busse, “Effects of pile burning in the Tahoe Basin on soil and water quality”; Round
10: Berrill & Dagley, “Stocking guidelines for aspen restoration”; LTBMU-HSU Monitoring Collaboration:
Berrill, Dagley & Coppeto, “Effects of slash pile burning after restoring conifer-encroached aspen”). We have sought advice and discussed plans with Dr. Matt Busse (Soil Scientist, USFS PSW) and Dr. J. Morgan
Varner (Fire Scientist, Humboldt State University). We have also been working with Cheryl Beyer
(Botanist, USFS LTBMU) to identify ~30 species of herbaceous understory vegetation in the monitoring plot at Ward Creek, and collected increment cores with Silver Hartman (CA State Parks) at Burton Creek
(North shore) and Sugar Pine Point State Park (West shore).
G .
S TRATEGY FOR E NGAGING WITH M ANAGERS AND O BTAINING P ERMITS
Throughout the project we will work with managers involved in aspen restoration around the Tahoe
Basin. We have obtained advice, positive feedback, and permission to sample aspen stands from aspen restoration project managers named above (Section F). Formal applications for field research permits will be submitted to the Tahoe Science Program annually in spring. We will continue to share preliminary findings and progress reports with our network of agency land managers, and request that they distribute our findings to any other land managers involved in aspen management and restoration. Our highest priority will be disseminating results with clear discussion of implications for management, and alert managers of unforeseen consequences of restoration activities detected during our regular site visits.
H .
D ESCRIPTION OF D ELIVERABLES /P RODUCTS AND THEIR R EVIEW AND D ISSEMINATION
T HIS PROJECT WILL PRODUCE :
Final report written for Tahoe Basin land managers summarizing data and key findings;
Annual conference presentations (oral/poster) at the Tahoe Basin Science Conference;
Data summary report for the nine monitoring plots (comprehensive pre- and post-treatment);
Report on dendrochronological analysis of disturbance and climate factors affecting aspen growth;
Predictive models for aspen survival/injury and pile construction guidelines for restoration thinning;
Report on validation of FVS model and Aspen Stocking Assessment Model (Berrill & Dagley);
Peer-reviewed journal article: “Patterns and dynamics of conifer encroachment in aspen”
Peer-reviewed journal article: “Response of degraded aspen communities to thinning and burning”
Quarterly reports of progress and study findings, and annual accomplishment reports.
P RODUCTS OF THIS RESEARCH WILL BE :
Reviewed internally by agency collaborators and Humboldt State University faculty;
Posted online under an “Aspen Restoration” link on the Tahoe Integrated Information Management
System (TIIMS) website (summary data, reports, powerpoints, pile burning calculator and guidelines);
All agency collaborators will be notified via e-mail of new uploads to TIIMS, with the specific URL link to TIIMS included in the message.
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E COSYSTEM R ESPONSE TO A SPEN R ESTORATION SNPLMA R OUND 12
Major milestones and deliverables are listed in the following project schedule (deliverables shown in bold ).
S CHEDULE OF M AJOR M ILESTONES /D ELIVERABLES
Milestone/
Deliverables
Re-measure trees and regeneration at all sites
Start
Date
Jun
2012
End
Date Description
Oct
2012
Measure tree diameters at all sites (giving 2-yr/3-yr growth); reassess regeneration, health; map & measure burn piles at all sites treated in 2010 (4 sites).
Data entry, summary, and analysis
Collect posttreatment measurements
Burn pile assessments
Data summary and analysis
Collect posttreatment data
Model development and reporting
Progress reporting
Disseminate results
Nov
2012
Jun
2013
Jun
2013
Sept
2013
Jun
2014
Sept
2014
Jul
2012
Jan
2013
May
2013
Oct
2013
Aug
2013
Apr
2014
Aug
2014
Apr
2015
Apr
2015
May
2015
Complete stand summaries, analyze regeneration patterns;
Calculate pile volume & density.
Dendrochronological analysis : measure ring widths, relate to climate and disturbance data. Distribute report for review.
Post pile burning assessment for sites burned in 2012: tree survival/health/healing, new regeneration.
Measure tree growth, assess survival, health, regeneration.
Map & measure burn piles at sites treated in 2011.
Apply experimental pile re-vegetation restoration treatments.
Re-assess sites burned in 2011 and 2012: tree survival, health, injury healing, new regeneration.
Summarize monitoring plot data, model trends, report changes to agency collaborators: Interim data summary report.
Spatial GIS analysis of tree density and species composition surrounding each subplot; relate to regen. and sapling growth.
Spatial GIS analysis of tree density and species composition surrounding each aspen; relate to growth, windthrow.
Re-assess sites for growth, health, regeneration, post-burn tree survival/health/healing; assess vegetation in burned patches.
Fit, validate, and refine final predictive models and pile burn thresholds (for range of pile size/distance scenarios).
Use repeated annual re-assessment data to develop indicators of mortality/health risk from scorch parameters.
Apply models to predict aspen survival/damage for range of pile size/distance scenarios, define thresholds.
Submit quarterly progress reports to Tahoe Science Program coordinator by the 1 st of July, October, January, and April, and summary of annual accomplishments by October 15 th , annually.
Science conference presentations; distribute data summary report and dendrochronological analysis report ; aspen pile burn mortality models ( spreadsheet calculator ) and pile burning guidelines ; update 2013 report on stocking assessment model (validation); submit manuscripts to peerreviewed journals; upload reports and models to TIIMS.
Final reporting May
2015
May
2015
Submit final report to Tahoe Science Program coordinator and
Tahoe Basin aspen forest managers
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L ITERATURE C ITED
Berrill, J-P.; Dagley, C.D. 2010. Preliminary stocking guidelines for aspen restoration in the LTBMU: comparing thinning prescription diameter limits. SNPLMA-funded report prepared for aspen forest managers in the Lake Tahoe Basin. 23p.
Calder, W.J.; Horn, K.J.; St. Clair, B. 2011. Conifer expansion reduces the competitive ability and herbivore defense of aspen by modifying light environment and soil chemistry. Tree Physiology 31:
582-591.
DeByle, N.V.; Winokur, R.P. 1985. Aspen: ecology and management in the western United States. Gen.
Tech. Rep. RM-119, U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and
Range Experiment Station. Fort Collins, CO.
Hardy, C.C. 1996. Guidelines for estimating volume, biomass, and smoke production for piled slash. Gen.
Tech. Rep. PNW-GTR-364, U.S. Department of Agriculture, Forest Service, Pacific Northwest
Research Station. Portland, OR.
Korb, J.E.; Johnson, N.C.; Covington, W.W. 2004. Slash pile burning effects on soil biotic and chemical properties and plant establishment: recommendations for amelioration. Rest. Ecol. 12(1): 52-62.
McGinnis, T.W.; Shook, C.D.; Keeley, J.E. 2010. Estimating aboveground biomass for broadleaf woody plants and young conifers in Sierra Nevada, California, Forests. West. J. Appl. For. 25(4): 203-209.
Perala, D.A. 1990. Populus tremuloides . pp. 555-569. In: (Burns, R.M. and B.H. Honkala, tech. coords.)
Silvics of North America: 2, Hardwoods. Agriculture Handbook 654. U.S. Department of
Agriculture, Forest Service. Washington D.C.
Rehfeldt, G.E.; Ferguson, D.E.; Crookston, N.L. 2009. Aspen, climate, and sudden decline in western USA.
For. Ecol. Manage. 258: 2353-2364.
Shepperd, W.D.; Rogers, P.C.; Burton, D.; Bartos, D. 2006. Ecology, biodiversity, management, and restoration of aspen in the Sierra Nevada. Gen. Tech. Rep. RMRS-GTR-178, U.S. Department of
Agriculture, Forest Service, Rocky Mountain Research Station. Fort Collins, CO.
Wright, C.S.; Balog, C.S.; Kelly, J.W. 2009. Estimating volume, biomass, and potential emissions of handpiled fules. Gen. Tech. Rep. PNW-GTR-805. Portland, OR: U.S. Department of Agriculture, Forest
Service, Pacific Northwest Research Station. 23p.
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F IGURES
E COSYSTEM R ESPONSE TO A SPEN R ESTORATION SNPLMA R OUND 12
Figure 1: Tree locations inside 1-ha (150 x 67m) monitoring plot, and locations of 0.004ha regeneration subplots (10 x 25-m spacing) adjacent to meadow, South Shore Project (SSP24), South Lake Tahoe, CA.
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E COSYSTEM R ESPONSE TO A SPEN R ESTORATION SNPLMA R OUND 12
Figure 2: Ward Creek stem location map of 1-ha (200 x 50 m) permanent sample plot in riparian aspen stand with conifer encroachment before and after thinning in 2009.
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180
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Aspen
Pine
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Pine
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10-20 20-30 30-40 40-50 50-60 60-70 70-80 80-90 90-100 > 100
Figure 3: Diameter distribution data for aspen-conifer stand at Ward Creek, Placer County, CA. Shown above are pre-treatment data from 1-ha permanent plot. Shown below is same stand after restorative thinning. Removal of hundreds of smaller conifers gave only minor reduction in stand density index
(SDI), suggesting that very little relief from crowding would be achieved under this restorative thinning prescription.
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E COSYSTEM R ESPONSE TO A SPEN R ESTORATION SNPLMA R OUND 12
Figure 4: Ward Creek burn pile and stem location map of 1-ha (200 x 50 m) permanent sample plot in riparian aspen stand with conifer encroachment after thinning in 2009. Inset shows examples of different distances between burn piles of different sizes and neighboring aspen trees of different sizes.
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E COSYSTEM R ESPONSE TO A SPEN R ESTORATION SNPLMA R OUND 12
Figure 5: Aspen stem discoloration and crown scorch from pile burning at Ward Creek fall 2011. Postburning assessment showed that heat and flames had led to discoloration of aspen bark (shown in photo) and crown scorch among trees near burn piles. Smaller aspen suckers were completely defoliated and presumed dead. Of interest to managers will be what happens to discolored aspen over time i.e., did the heating kill the cambium? And, will the tree survive, or develop health problems?
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E COSYSTEM R ESPONSE TO A SPEN R ESTORATION SNPLMA R OUND 12
Figure 6: HSU researchers measure distance of approximately 3m from the edge of large old burn pile to neighboring (dead) aspen. Aspen trees around this pile all had bark peeled and cracked on the side of stem facing the burn pile, suggesting that aspen may not recover from stem heating injuries. Heat may have killed the cambium on that side of the tree. Note: cause of death cannot be attributed to pile burning without assessment of pre-burn tree status. It will be instructive to track changes on aspen with stems discolored by heat (e.g., Figure 5).
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