Publication Number: 500-04-071F
Publication Date: March 2004
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A measurement and monitoring activity was carried out to assess the relative biomass carbon storage potential of extending forested buffer zones by 200 feet (100 feet either side of existing regulations) at two study sites representing key timber production regions in California: Sierran mixed conifers at Blodgett Forest Research Station(BFRS) in the Sierra Nevadas and coastal redwoods at Jackson Demonstration State Forest (JDSF). Each of these site assessments is presented as a specific and independent case study and each reflects a unique set of conditions (e.g., species composition), which determines the response to different management practices.
Figure S1. Location of Jackson Demonstration State Forest
And Blodgett Forest Research Station in California
Blodgett Forest Research Station
Supplementary field measurements were made during October 2003 to allow data from the Blodgett Forest Research Station's (BFRS) network of permanent plots to be used for carbon analyses. Data from the permanent sample plots were converted to biomass carbon estimates in trees using regression equations available in the literature for Californian forests. Other data from the Blodgett forest plots were not directly usable for estimating carbon stocks. The additional data collected consisted of measurements to relate litter and duff depth and biomass, soil carbon stocks, and dead wood densities.
Analyses of the BFRS permanent plots alongside literature reports permitted the creation of growth curves. The plot data also resulted in relationships between forest age or aboveground biomass carbon and forest floor carbon, standing and lying dead wood and the carbon stocks belowground in roots. There was little relationship between forest age and soil carbon stocks and so soil carbon was emitted from this analysis.
Extension of riparian buffer zones from 75 feet (baseline) to 175 feet results in carbon storage benefits amounting to approximately 1,100-1,200 tons over the additional 6.1 hectares of riparian forest retained per straight line kilometer of stream length after 80 years. The additional carbon results from continued accumulation of forest carbon in the protected area compared with varying forest carbon in the managed (baseline) area due to successive harvests and regrowth and consequent reduction in equivalent long-term average forest carbon storage. The reduction in forest carbon on the managed site is not offset by cumulative carbon storage in long-term wood products.
Jackson State Demonstration Forest
Field data were collected at the JDSF in February 2004. Measurements were made of trees in and around clearcuts and group selections and of dead wood, litter, understory and soil carbon. The JDSF was dominated by redwood forests and activities focused in this forest type.
Growth curves for coastal redwood at JDSF were developed from existing empirical yield tables. Field measurements drove the calibration of models predicting the accumulation of dynamic forest carbon pools including litter and downed dead wood stocks. Standing dead wood, understory vegetation, and soil carbon showed no appreciable changes with management or stand age. These findings were used to predict responses in forest biomass with change in management practices. The transformation efficiency of receiving mills was substantiated via interviews with local operators.
Over one rotation of model scenarios involving different site productivities and initial stand ages, extension of riparian buffer zones from the existing mandate of 100 feet (baseline) to 200 feet either side of the watercourse, consistently results in an unambiguous increase in carbon storage. Over one rotation, carbon storage benefits resulting from extension of the buffer area range from 151 to 208 t C per hectare or 921 to 1,269 t C per one kilometer length of stream.
Average carbon storage in the baseline case, even including harvest-derived pools of slash and long term wood products, is easily exceeded by the steadily growing, unharvested, forest within the buffer extension area. In fact, the addition of post harvest slash and long-term wood products to carbon storage, which approaches an average of 110 t C/ha derived after 500 years, does not offset the reduction in long term average forest carbon storage accompanying management, approximatelt -300 t C/ha (approximately 500+ t C/ha for a mature redwood stand on site index 160 minus the long term average of 193 t C/ha for the same redwood stand under even-aged management with a 90-year rotation). The extended buffer can thus potentially generate an increase in carbon storage that approaches 200 t C/ha on a time scale of hundreds of years.
Conclusions and Recommendations
Extension of riparian buffer zones by 100 feet in commercially managed forests in California can lead to estimated carbon benefits of 1,100 tons per km of stream over 80 years in mixed Sierran conifer forests and 920 tons per km of stream over 100 years in coastal redwood forests. Additional benefits to California will be in water quality, and in habitat for wildlife and fisheries.
The estimates provided here are assessments of the potential carbon benefits from extending riparian buffer zones. The report outlines details of the measurements and the types of analyses needed to calculate the carbon stocks under baseline and change-in-management conditions when there are existing inventory data and how to consider the variance in calculating the number of plots required for measuring and monitoring. Where there are no existing inventory data, additional measurements would be required but the analyses would essentially be the same as those given here. In a separate report (Methods for Measuring and Monitoring Forestry Carbon Projects in California - Energy Commission publication # 500-04-072F) we provide more details on the methodology for collecting the field data.
A measurement and monitoring activity was carried out to assess the relative biomass carbon storage potential of extending forested buffer zones by 200 feet (100 feet either side of existing regulations) at two study sites representing key timber production regions in California: Sierran mixed conifers at Blodgett Forest Research Station(BFRS) in the Sierra Nevada and coastal redwoods at Jackson Demonstration State Forest (JDSF).
Each of these site assessments is presented as a specific and independent case study, and each reflects a unique set of conditions (e.g., species composition), which determines the response to different management practices. The assessments were based on a combination of existing field data from forest inventory plots gathered by the respective forest sites, new field measurements for missing components, empirical modeling, and data integration.
Researchers estimated the changes in carbon stocks for baseline conditions (continued harvesting) and compared these to the carbon stocks from conserving the forests with no harvesting. Extension of riparian buffer zones can lead to estimated benefits of 1,100-1,200 tons of carbon (C) per kilometer (km) of stream (or 2.3-2.5 t C/hectare per year (ha.yr)) over 80 years in mixed Sierran conifer forests and 920-1,270 tons C per km of stream (or 1.5-2.1 t C/ha.yr) over 100 years in coastal redwood forests.
The carbon benefit arises from the increased biomass in living and dead trees in the forest exceeding the carbon stored in wood products and logging slash. Additional environmental benefits would include habitat for wildlife, protection for fish breeding and migrating sites, and a reduction in runoff from the land.
Table of Contents
Executive Summary 1
1.0 Introduction 4
1.2. Environmental co-benefits of extended riparian protection 6
1.3. Leakage 6
1.4. References 6
2.2. Carbon calculations for Blodgett forest 10
2.3.2. Forest floor and dead wood 14
2.3.3. Soil organic carbon 15
2.3.4. Carbon pools summed 16
2.3.5. Long-term wood products 18
2.4.2. Without-buffer scenario 20
2.6. Carbon benefits 24
3.2. Accumulation of carbon on growing redwood stands 29
3.3. Biomass calculations for Jackson forest 29
3.3.2. Belowground biomass 31
3.3.3. Litter and duff 31
3.3.4. Dead wood 32
3.3.5. Understory vegetation 34
3.3.6. Soil organic carbon 34
3.3.7. Harvest efficiency, slash and long-term wood products 35
3.3.8. Carbon pools summed 37
Appendix A: Variance and Number of Plots A-1
List of Figures
Figure S1. Location of Jackson Demonstration State Forest and Blodgett Forest Research Station in California 1
Figure 1.1. The amount of land in the existing legislated buffer and the proposed extension. A straight length of stream here represents any form of stream. 5
Figure 2.1. Mixed Sierran conifer forest at BFRS 7
Figure 2.2. Blodgett Forest Research Station. The forest compartments are outlined. 8
Figure 2.3. Even-aged stands of ponderosa pine adjacent to BFRS 10
Figure 2.4. Relationship between litter/duff depth and biomass carbon 11
Figure 2.5. The Chapman-Richards curve fitted to the Blodgett plot data (± 95% Confidence Interval) 14
Figure 2.6. Relationship between forest age and biomass carbon of litter and duff 15
Figure 2.7. Relationship between forest age and biomass carbon of down dead wood 15
Figure 2.8. The relationship between aboveground live biomass carbon density and biomass carbon of standing dead wood 15
Figure 2.9. Carbon accumulation in a Californian Sierran forest modeled over 200 years 16
Figure 2.10. A slash pile in the forest at Blodgett 17
Figure 2.11. Growth and harvest cycles for live biomass in Sierran forests, the long term average biomass carbon density is indicated. 18
Figure 2.12. Proportions of harvested timber converted to saw and veneer logs and various wood waste streams as reported by Morgan et. al. (unpublished) from surveys of California wood product plants in 2000 19
Figure 2.13. The oxidation of long-term wood products through time. (a) after a single harvest, and (b) with multiple harvests on an 80-year rotation 20
Figure 2.14. Comparative carbon accumulation in the extended buffer area with buffer (no harvest) and without buffer (even-aged management with an 80-year rotation) considering an initial stand age of 60 years on medium productivity site. Managed area (without protection) long-term (160-year) average carbon storage in all pools including LWPs is 199 t C/ha. 21
Figure 2.15. Accumulation of carbon in long-term wood products (LWPs) over and above the long-term average (LTA) forest carbon stock with management (180 t C/ha) 22
Figure 2.16. Carbon storage on 80-year rotation even-aged management and medium productivity with initial forest ages of 20, 40, 60, and 80 years 23
Figure 3.1. Engine and skid road circa 1890, Fort Bragg, California (from Williams 1989) 26
Figure 3.2. Jackson Demonstration State Forest. The location of field investigation sites is indicated. 27
Figure 3.3. Fifteen-year-old stand of redwood regenerating after a clearcut at JDSF 28
Figure 3.4. Growth curves for redwoods at site indices of 120, 160, and 180. The points represent the results from the yield tables (Lindquist and Pelley 1963), the curves are extrapolation of these points. 30
Figure 3.5. Inferred accumulation of biomass carbon in litter on aggrading redwood stands at JDSF with 95% confidence intervals. Biomass carbon density of litter (t C/ha) = 10.4 * (1 - exp(-0.073 * forest age))4 . 31
Figure 3.6. Remnant log section from a cut dating from circa 1860Ð1890 32
Figure 3.7. Relationship between biomass carbon accumulation in down dead wood and forest age +/- 95% confidence intervals 34
Figure 3.8. Comparative soil carbon in redwood stands harvested 1985/1990 (n=14) and circa 1860Ð1890 (n=16) at JDSF. Error bars equal 95% confidence interval. Differences are not significant. 35
Figure 3.9. Logging slash on a 15-year-old group selection at the Boundary stand, JDSF 36
Figure 3.10. Mean proportions of harvested redwood saw logs converted to boards and "waste" streams derived from interviews with northern California sawmill operators (n = 5) 37
Figure 3.11. Sum of each of the significant biomass density pools for second-growth redwood forest accumulating over 250 years. A site index of 160 and the moderate levels for down dead wood and forest floor are illustrated. 38
Figure 3.12. Sum of each of the significant biomass carbon pools in and derived from second-growth redwood forest accumulating over three harvest (clearcut) cycles. A site index of 160 with moderate levels for down dead wood and forest floor is illustrated. 39
Figure 3.13. Comparative carbon accumulation in extended buffer area with buffer (no harvested) and without buffer (harvested) with initial stand age of 60 years on site index 160 with moderate levels for down dead wood and forest floor. Without project (with harvest) rotation length (90-year) average carbon storage in all pools including LWPs is 275 t C/ha. 40
Figure 3.14 Projected accumulation of stored carbon (equivalent t C/ha) in long term wood products and post harvest slash additional to the long term average (LTA) forest biomass carbon, 193 t C/ha, for a redwood stand on site index 160 under even-aged management with a 90-year rotation 42
List of Tables
Table 2.1. The tree species of BFRS. Commercially grown species are underlined. 9
Table 2.2. The allometric regression equations of Jenkins et al. (2003) and the Blodgett Forest species to which they are applied 10
Table 2.3. Oven-dried dead wood densities 12
Table 3.1. The tree species of JSDF. Dominant species are in bold. Commercially grown species are underlined. 28
Table 3.2. The allometric regression equations of Jenkins et al. (2003) and the Jackson Forest species to which they are applied 29
Table 3.3. Oven dried densities of decomposed dead wood 33
Table 3.4. Comparative total carbon storage (t C/ha) of with (with-project) and without (without-project) harvest in extended buffer cases over a 90-year project period. With-project values equal total forest biomass accumulated at the end of the period. Without-project values equal average carbon storage, including harvest-derived pools of slash and long term wood products, derived for the same 90-year period. 41