Southern Sierra Nevada Wildfire Risk Assessment:

Transcription

1 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Prepared by: Don Helmbrecht Wildland Fire Analyst, TEAMS Enterprise Unit Prepared for: Phil Bowden, Regional Fuels Manager USDA Forest Service, Pacific Southwest Region May 18, 2015

2 In accordance with Federal civil rights law and U.S. Department of Agriculture (USDA) civil rights regulations and policies, the USDA, its Agencies, offices, and employees, and institutions participating in or administering USDA programs are prohibited from discriminating based on race, color, national origin, religion, sex, gender identity (including gender expression), sexual orientation, disability, age, marital status, family/parental status, income derived from a public assistance program, political beliefs, or reprisal or retaliation for prior civil rights activity, in any program or activity conducted or funded by USDA (not all bases apply to all programs). Remedies and complaint filing deadlines vary by program or incident. Persons with disabilities who require alternative means of communication for program information (e.g., Braille, large print, audiotape, American Sign Language, etc.) should contact the responsible Agency or USDA s TARGET Center at (202) (voice and TTY) or contact USDA through the Federal Relay Service at (800) Additionally, program information may be made available in languages other than English. To file a program discrimination complaint, complete the USDA Program Discrimination Complaint Form, AD-3027, found online at and at any USDA office or write a letter addressed to USDA and provide in the letter all of the information requested in the form. To request a copy of the complaint form, call (866) Submit your completed form or letter to USDA by: (1) mail: U.S. Department of Agriculture, Office of the Assistant Secretary for Civil Rights, 1400 Independence Avenue, SW, Washington, D.C ; (2) fax: (202) ; or (3) program.intake@usda.gov. USDA is an equal opportunity provider, employer and lender.

3 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Contents Overview of the Condition Assessment... 1 Purpose and background of the assessment... 1 Assessment area... 2 Structure of report... 2 Analysis Methods... 2 Biophysical settings... 2 Natural range of variability and reference conditions... 4 Current vegetation structure... 6 Landscape units... 6 departure metrics... 9 Analysis Results Forested biophysical settings California Montane Jeffrey Pine (-Ponderosa Pine) Woodland and Mediterranean California Dry-Mesic Mixed Conifer Forest and Woodland Mediterranean California Red Fir Forest - Southern Sierra and Cascades variants Mediterranean California Mesic Mixed Conifer Forest and Woodland Great Basin Pinyon-Juniper Woodland Central and Southern California Mixed Evergreen Woodland Mediterranean California Subalpine Woodland California Lower Montane Blue Oak-Foothill Pine Woodland and Savanna Sierra Nevada Subalpine Lodgepole Pine Forest and Woodland - Wet Inter-Mountain Basins Subalpine Limber-Bristlecone Pine Woodland Shrubland biophysical settings Inter-Mountain Basins Big Sagebrush Shrubland, Great Basin Xeric Mixed Sagebrush Shrubland, and Inter-Mountain Basins Montane Sagebrush Steppe Northern and Central California Dry-Mesic Chaparral References Appendix A: Succession Class Mapping Rules Tables Table 1. LANDFIRE biophysical setting model groupings... 3 Table 2. Succession class reference proportions for each biophysical setting... 5 Table 3. Landscape level unit designations across the three forests (see also figure 4)... 7 Table 4. Landscape level for each biophysical setting... 8 Table 5. Example of stratum vegetation departure calculations... 9 Table 6. condition results for the California Montane Jeffrey Pine (-Ponderosa Pine) Woodland biophysical setting Table 7. condition results for the Mediterranean California Dry-Mesic Mixed Conifer Forest and Woodland biophysical setting Table 8. condition results for the Mediterranean California Red Fir Forest (Southern Sierra variant) biophysical setting Table 9. condition results for the Mediterranean California Red Fir Forest (Cascades variant) biophysical setting Table 10. condition results for the Mediterranean California Mesic Mixed Conifer Forest and Woodland biophysical setting Table 11. condition results for the Great Basin Pinyon-Juniper Woodland biophysical setting i

4 Table 12. condition results for the Central and Southern California Mixed Evergreen Woodland biophysical setting Table 13. condition results for the Mediterranean California Subalpine Woodland biophysical setting Table 14. condition results for the California Lower Montane Blue Oak-Foothill Pine Woodland and Savanna biophysical setting Table 15. condition results for the Sierra Nevada Subalpine Lodgepole Pine Forest and Woodland - Wet biophysical setting Table 16. condition results for the Inter-Mountain Basins Subalpine Limber- Bristlecone Pine Woodland biophysical setting Table 17. condition results for the Inter-Mountain Basins Big Sagebrush Shrubland biophysical setting Table 18. condition results for the Great Basin Xeric Mixed Sagebrush Shrubland biophysical setting Table 19. condition results for the Inter-Mountain Basins Montane Sagebrush Steppe biophysical setting Table 20. condition results for the Northern and Central California Dry-Mesic Chaparral biophysical setting Table 21. Tree, shrub, and herbaceous canopy cover classes used in LANDFIRE Table 22. Tree, shrub, and herbaceous height classes used in LANDFIRE Table 23. Final succession class (S-Class) mapping rules for each biophysical setting. Rules are based on dominant lifeform and threshold existing vegetation cover (EVC) and existing vegetation height (EVH) values. Bold cells indicate an adjustment was made from the vegetation dynamics model threshold value Figures Figure 1. Southern Sierra Nevada Land and Resource Management Plan Environmental Impact Statement analysis area and National Forests... 1 Figure 2. Biophysical settings in the environmental impact statement analysis area... 4 Figure 3. Succession classes in the environmental impact statement analysis area... 6 Figure 4. Landscape units in the project extent. Biophysical settings are assigned to a landscape unit for analysis based on historical disturbance regime characteristics and areal distribution (see also table 3) Figure 5. Distribution of the California Montane Jeffrey Pine (-Ponderosa Pine) Woodland and Mediterranean California Dry-Mesic Mixed Conifer Forest and Woodland biophysical settings Figure 6. Distribution of the Mediterranean California Red Fir Forest biophysical settings Figure 7. Distribution of the Mediterranean California Mesic Mixed Conifer Forest and Woodland biophysical setting Figure 8. Distribution of the Great Basin Pinyon-Juniper Woodland biophysical setting Figure 9. Distribution of the Central and Southern California Mixed Evergreen Woodland biophysical setting Figure 10. Distribution of the Mediterranean California Subalpine Woodland biophysical setting Figure 11. Distribution of the California Lower Montane Blue Oak-Foothill Pine Woodland and Savanna biophysical setting Figure 12. Distribution of the Sierra Nevada Subalpine Lodgepole Pine Forest and Woodland - Wet biophysical setting... 27

5 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Figure 13. Distribution of the Inter-Mountain Basins Subalpine Limber-Bristlecone Pine Woodland biophysical setting Figure 14. Distribution of the Inter-Mountain Basins Big Sagebrush Shrubland biophysical setting Figure 15. Distribution of the Inter-Mountain Basins Montane Sagebrush Steppe biophysical setting iii

6

7 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Overview of the Condition Assessment Purpose and background of the assessment This assessment was conducted to quantify vegetation departure from historical conditions generally referred to as those prior to Euro-American settlement for use in the Southern Sierra Nevada (SSN) Wildfire Risk Assessment (Scott et al. 2015) and Land and Resource Management Plan revision process. This regional-scale assessment provides information about the ecological integrity of terrestrial ecosystems across three National Forests the Inyo, Sequoia, and Sierra by comparing the current distribution of vegetation structure to the natural range of variability (NRV) in vegetation structure under historical conditions (Barrett et al. 2010). This assessment complements other plan revision work done in the region including the Sierra Nevada Bio-regional Assessment (USDA-FS 2015a) and the individual early-adopter forest-level assessments (USDA-FS 2015b, 2015c, 2015d). We acknowledge that there are limitations to focusing on one ecosystem characteristic as a measure of the ecological integrity of terrestrial ecosystems and in using the natural range of variability of the historical period as the reference condition. Nevertheless, vegetation structure is a key characteristic to which other ecosystem characteristics respond (e.g., natural disturbance regimes, wildlife habitat and connectivity, plant and animal species diversity, and hydrologic regimes); and while the impacts of future stressors such as climate change and land use change are uncertain, ecosystem characteristics within the natural range of variability prior to Euro-American settlement are assumed to provide a benchmark of those which are resilient and adaptive (Landres et al. 1999; Keane et al. 2009). Figure 1. Southern Sierra Nevada Land and Resource Management Plan Environmental Impact Statement analysis area and National Forests 1

8 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Assessment area The vegetation condition assessment uses the extent defined for the Southern Sierra Nevada Land and Resource Management Plan revision Environmental Impact Statement (figure 1). This extent (hereafter, EIS extent) encompasses the three National Forests being analyzed for plan revision and is based on the South and East South ecosubregions of the Sierra Nevada Bioregional Assessment (USDA-FS 2015a). Structure of report This report opens with a description of the purpose and background of the assessment, assessment area, and structure of the report (this page). The report then describes the analysis methods used in conducting the assessment. Finally, the report summarizes the results by biophysical setting. The results section purposefully does not go into great detail in describing biophysical settings or associated disturbance regimes as this information can be found in the LANDFIRE (2007) vegetation dynamics model descriptions. Analysis Methods This assessment was conducted using LANDFIRE data (Rollins 2009) and the vegetation departure methodology presented in the Interagency Fire Regime Condition Class (FRCC) Guidebook (Barrett et al. 2010). Information regarding the integration of these results with the Southern Sierra Nevada Wildfire Risk Assessment may be found in the report prepared by Scott et al. (2015). Four primary inputs are required to assess vegetation departure using the fire regime condition class methodology: 1. Geospatial data representing biophysical settings. 2. Reference conditions for each biophysical setting. 3. Geospatially delineated landscape units for which to analyze and summarize the departure of individual biophysical settings. 4. Geospatial data of current vegetation structure. Biophysical settings Biophysical settings represent potential vegetation that may have been present on the landscape prior to Euro-American settlement (Rollins 2009; Barrett et al. 2010). Biophysical setting map units are based on both the capability of the land and climate to support various vegetation types and the historical disturbance regime. LANDFIRE geospatial biophysical setting data were provided by Phil Bowden, USDA Forest Service Pacific Southwest Regional Fuels Manager, at the EIS extent. dynamics models describing the biophysical, vegetation, and disturbance characteristics of each biophysical setting map unit were acquired from the LANDFIRE website ( A Web-based Meeting was held on September 4, 2013 to review the model descriptions for the biophysical settings located within the Southern Sierra Nevada project extent. Meeting participants included: Don Helmbrecht (TEAMS Fire Ecologist/meeting facilitator), Marc Meyer (Regional Ecologist), Jay Miller (Remote Sensing Specialist), Hugh Safford (Regional Ecologist), Joe Scott (Wildland Fire Analyst), and Neil Sugihara (Regional Fire Ecologist). Michele Slaton (GIS Specialist) 2

9 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report and Heather Stone ( Management Specialist) provided review of the pinyon-juniper and sagebrush models post-meeting. Table 1. LANDFIRE biophysical setting model groupings LANDFIRE Biophysical Setting Name LANDFIRE Biophysical Setting Code Presettlement Fire Regime 1 LANDFIRE Model Used in Condition Assessment Inter-Mountain Basins Big Sagebrush Shrubland Big Sagebrush Inter-Mountain Basins Big Sagebrush Steppe Big Sagebrush Inter-Mountain Basins Montane Sagebrush Steppe Big Sagebrush Great Basin Xeric Mixed Sagebrush Shrubland Black and Low Sagebrush California Mesic Chaparral Chaparral-Serotinous Conifers California Montane Woodland and Chaparral Chaparral-Serotinous Conifers Great Basin Semi-Desert Chaparral Chaparral-Serotinous Conifers Northern and Central California Dry-Mesic Chaparral Chaparral-Serotinous Conifers Sonora-Mojave Semi-Desert Chaparral Chaparral-Serotinous Conifers Mediterranean California Dry-Mesic Mixed Conifer Forest and Dry Mixed Conifer Woodland Sierra Nevada Subalpine Lodgepole Pine Forest and Woodland Lodgepole Pine Sierra Nevada Subalpine Lodgepole Pine Forest and Woodland Lodgepole Pine Wet Mediterranean California Mesic Mixed Conifer Forest and Moist Mixed Conifer Woodland California Lower Montane Blue Oak-Foothill Pine Woodland and Oak Woodland Savanna Mediterranean California Mixed Oak Woodland Mixed Evergreen Great Basin Pinyon-Juniper Woodland Pinyon-Juniper Mediterranean California Red Fir Forest - Cascades Red Fir Mediterranean California Red Fir Forest - Southern Sierra Red Fir Mediterranean California Subalpine Woodland Subalpine Forest Northern California Mesic Subalpine Woodland Subalpine Forest Sierra Nevada Subalpine Lodgepole Pine Forest and Woodland Lodgepole Pine Dry Inter-Mountain Basins Subalpine Limber-Bristlecone Pine Subalpine Forest Woodland Rocky Mountain Subalpine-Montane Limber-Bristlecone Pine Subalpine Forest Woodland California Montane Jeffrey Pine(-Ponderosa Pine) Woodland Yellow Pine Mediterranean California Lower Montane Black Oak-Conifer Forest and Woodland Yellow Pine Van de Water and Safford (2011) presettlement fire regime vegetation types shown for reference. 3 Based on local knowledge and ancillary vegetation data, workshop participants felt that areas mapped as a Mediterranean California Mixed Oak Woodland biophysical setting were incorrectly classified and should be classified as Central and Southern California Mixed Evergreen Woodland (BpS model ). 3

10 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Models were reviewed for applicability to the scope and scale of the assessment. Participants chose to group certain models based on similarity of vegetation characteristics and fire regimes, primarily following the crosswalk between LANDFIRE biophysical setting and presettlement fire regime groups presented in Van de Water and Safford (2011). We reclassified the biophysical setting data to a total of fifteen biophysical setting models for use in the final assessment (table 1). The spatial distribution of biophysical settings is shown in figure 2. Figure 2. Biophysical settings in the environmental impact statement analysis area Natural range of variability and reference conditions LANDFIRE succession classes (S-Classes) represent vegetation development stages defined by species composition, vegetation structure, and stand age. The number and definition of S-Classes are unique to each biophysical setting and are described in the associated vegetation dynamics models. The standard five-box, or five-state, model uses the following classes: S-Class A: Early-development (i.e., post-replacement-severity disturbance) S-Class B: Mid-development, closed structure 4

11 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report S-Class C: Mid-development, open structure S-Class D: Late-development, open structure S-Class E: Late-development, closed structure Uncharacteristic classes are also used to represent either native vegetation conditions that would be unlikely under the natural range of variability or situations where exotic species have partially or completely replaced the native species. Table 2. Succession class reference proportions for each biophysical setting biophysical setting Biophysical Setting Name Model Succession Class A B C D E Central and Southern California Mixed Evergreen Woodland N/A N/A Great Basin Pinyon-Juniper Woodland N/A Inter-Mountain Basins Subalpine Limber-Bristlecone Pine Woodland N/A N/A Mediterranean California Dry-Mesic Mixed Conifer Forest and Woodland Mediterranean California Mesic Mixed Conifer Forest and Woodland California Montane Jeffrey Pine(-Ponderosa Pine) Woodland Mediterranean California Red Fir Forest - Cascades Mediterranean California Red Fir Forest - Southern Sierra Mediterranean California Subalpine Woodland N/A N/A Sierra Nevada Subalpine Lodgepole Pine Forest and Woodland - Wet Great Basin Xeric Mixed Sagebrush Shrubland N/A Inter-Mountain Basins Big Sagebrush Shrubland Northern and Central California Dry-Mesic Chaparral N/A N/A N/A California Lower Montane Blue Oak-Foothill Pine Woodland and Savanna N/A Inter-Mountain Basins Montane Sagebrush Steppe Reference proportions for BpS model were modified to match a locally adjusted model referenced in the Bodie Hills Conservation Action Plan (Provencher et al. 2009). The LANDFIRE vegetation dynamics model descriptions also provide an estimate of the relative abundance of each S-Class (i.e., the proportion of the BpS occupied by the S-Class) to be expected under the natural disturbance regime (i.e., prior to Euro-American settlement). abundance was estimated through state-and-transition modeling using the Dynamics Development Tool (VDDT, ESSA Technologies Ltd. 2007). Each S-Class is equivalent to a vegetation state in the state-andtransition model and each state is assigned a number of years indicating how long it typically persists before succeeding to a new state. Probabilistic transitions between states are used to represent the effects of disturbances. The pre Euro-American settlement rates of succession and disturbance used in the model are based on scientific literature, currently available data, and the experience and judgement of the modelers (Rollins 2009). Each model was run for ten, 1,000-timestep simulations in vegetation dynamics development tool to determine the natural range of variability in the proportion of each S-Class. The 5

12 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report mean relative abundance value for each S-Class within a biophysical setting was used as the reference condition for which to compare current conditions (table 2). Current vegetation structure LANDFIRE maps the S-Class of individual biophysical settings based on expert-defined rules that identify applicable ranges of existing vegetation cover, existing vegetation height, lifeform, and to a lesser extent species composition, for each S-Class. Ideally, the S-Class mapping rules would be mutually exclusive and exhaustive, but this is not always the case. We reviewed the S-Class mapping rules of each vegetation dynamics model during the web-based meeting mentioned above to ensure the rules were mutually exclusive and exhaustive. The threshold values differentiating individual classes were also reviewed for local applicability. Adjustments to rules were based on input from meeting participants (Appendix A). We remapped S-Class using updated geospatial data of existing vegetation cover, existing vegetation height, and disturbance type and severity (figure 3). These were LANDFIRE 2008 data (version 1.2.0) updated for disturbances through the year 2012, by Phil Bowden and his team. Figure 3. Succession classes in the environmental impact statement analysis area Landscape units The vegetation departure metrics of the Fire Regime Condition Class Guidebook methodology are scaledependent, and it is therefore critically important to choose appropriately sized analysis units for 6

13 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report summarizing results. The general rule-of-thumb is that units should be at an extent within which the full expression of succession classes would be expected to occur under the natural disturbance regime of the biophysical setting being analyzed (Barrett et al 2010). Three levels of landscape units were derived to account for the various disturbance regimes of the biophysical settings being assessed (Table 3 and figure 4). The largest level is associated with the three national forests in the project area (Inyo, Sierra, and Sequoia). At the middle landscape unit level, the larger units are divided into two-to-three smaller nested units that are roughly associated with ranger districts. Landscape units at the smallest level divide the mid-level units into two-to-four smaller nested units. All landscape units were derived from hydrologic unit boundaries or major geographic or physical features (e.g., U.S. Route 395). Landscape units are named based on level and associated Forest, District, and geography. Table 3. Landscape level unit designations across the three forests (see also figure 4) Level 3 Level 2 Level 1 Inyo Inyo:Mono-Mammoth Inyo:Mono-Mammoth:EA North Inyo:Mono-Mammoth:East Inyo:Mono-Mammoth:West Inyo:Mount Whitney Inyo:Mount Whitney:East Inyo:Mount Whitney:West Inyo:White Mountain Inyo:White Mountain:East Inyo:White Mountain:West Sequoia Sequoia:Hume-Tule-Hot Springs Sequoia:Hume-Tule-Hot Springs:Hot Springs Sequoia:Hume-Tule-Hot Springs:Hume Lake East Sequoia:Hume-Tule-Hot Springs:Hume Lake West Sequoia:Hume-Tule-Hot Springs:Tule River Sequoia:Kern River Sequoia:Kern River:EA South Sequoia:Kern River:East Sequoia:Kern River:West Sierra Sierra:Bass Lake Sierra:Bass Lake:East Sierra:Bass Lake:West Sierra:High Sierra Sierra:High Sierra:North Sierra:High Sierra:South 7

14 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Figure 4. Landscape units in the project extent. Biophysical settings are assigned to a landscape unit for analysis based on historical disturbance regime characteristics and areal distribution (see also table 3). Biophysical setting models were assigned to a landscape unit based on information from the LANDFIRE biophysical setting model descriptions (LANDFIRE 2007) and locally provided bioregional assessment documents (Meyer 2013a, Meyer 2013b, Safford 2013) about the historical size distribution of disturbances. Biophysical settings associated with disturbance regimes characterized by large disturbances were assessed using larger analysis units than those characterized by smaller disturbances. The acreage and areal distribution of the biophysical setting were also considered in assigning it to a landscape level. Table 4 shows the landscape level assigned to each biophysical setting. Table 4. Landscape level for each biophysical setting Biophysical Biophysical Setting Name Setting Model Landscape Level Central and Southern California Mixed Evergreen Woodland Inter-Mountain Basins Subalpine Limber-Bristlecone Pine Woodland Mediterranean California Subalpine Woodland Great Basin Xeric Mixed Sagebrush Shrubland Inter-Mountain Basins Big Sagebrush Shrubland California Lower Montane Blue Oak-Foothill Pine Woodland and Savanna Great Basin Pinyon-Juniper Woodland 2 8

15 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Biophysical Setting Model Biophysical Setting Name Landscape Level Mediterranean California Dry-Mesic Mixed Conifer Forest and Woodland Mediterranean California Mesic Mixed Conifer Forest and Woodland California Montane Jeffrey Pine(-Ponderosa Pine) Woodland Mediterranean California Red Fir Forest - Cascades Mediterranean California Red Fir Forest - Southern Sierra Sierra Nevada Subalpine Lodgepole Pine Forest and Woodland - Wet Inter-Mountain Basins Montane Sagebrush Steppe Northern and Central California Dry-Mesic Chaparral 3 departure metrics We assessed vegetation departure following the Interagency Fire Regime Condition Class Guidebook methodology (Barrett et al. 2010), which compares the reference distribution of S-Classes (i.e., the proportion that each contributes to the whole expressed as a percent) to the current distribution of S- Classes for each combination of biophysical setting and landscape unit. We present two levels of vegetation departure metrics in this report: stratum, or biophysical setting, departure and S-Class departure. Stratum vegetation departure is calculated by subtracting the sum of the S-Class similarity values (i.e., the lesser of the reference and current proportions) from 100 (table 5), for each combination of biophysical setting and landscape unit. The stratum vegetation departure is then classified into one of three vegetation condition class (VCC) categories as shown below. Stratum similarity is 59 percent, current departure is 41 percent, and vegetation condition class is 2. VCC1: low departure (less than or equal to 33 percent stratum vegetation departure) VCC2: moderate departure (greater than 33 percent and less than or equal to 66 percent stratum vegetation departure) VCC3: high departure (greater than 66 percent stratum vegetation departure) Table 5. Example of stratum vegetation departure calculations Succession Class (S-Class) Reference Proportion (%) Current Proportion (%) S-Class Similarity A-Early B-Mid C-Late Uncharacteristic S-Class departure is quantified as the percent difference of the current and reference proportions for individual S-Classes in each combination of biophysical setting and landscape unit. 9

16 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report S-Class percent difference= CP-RP max(rp,cp) *100 CP is the current proportion of the S-Class within the landscape unit and RP is the reference proportion. Positive values of this measure indicate that the current proportion of the S-Class exceeds the reference proportion; negative values indicate that the current is less than the reference proportion. For example, if the current proportion is twice the reference proportion, the S-Class percent difference is +50%; if the current proportion is half of the reference, then percent difference is -50%. S-Class percent difference is then classified into one of five relative amount categories: : (< -66 percent difference) Under-represented: ( -66 percent difference and < 33 percent difference) Similar: ( -33 percent difference and 33 percent difference) Over-represented: (> 33 percent difference and 66 percent difference) Abundant: (> 66 percent difference) These categories were further refined into deficit, similar, and surplus for use in the wildfire risk assessment (Scott et al. 2015). We used the 2008 Interagency Fire Regime Condition Class Guidebook (Hann et al. 2004) breakpoints for classifying S-Class relative amount because it provides equal ranges of departure on both sides of the reference condition. The 2010 Guidebook changed the breakpoint value between similar and overrepresented to 5 percent and the breakpoint value between over-represented and abundant to 80 percent, thus biasing the over-represented category. For example, with the 2010 breakpoints, a reference proportion of 10 percent and a current proportion of 11 percent, would be considered over-represented ((1/11) * 100 = 9.1 percent difference). A current proportion of 40 percent would also fall in the overrepresented class ((30/40) * 100 = 75 percent difference), even though the first situation has 10 percent more acreage than the reference and the later has four times as much. 10

17 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Analysis Results Forested biophysical settings California Montane Jeffrey Pine (-Ponderosa Pine) Woodland and Mediterranean California Dry-Mesic Mixed Conifer Forest and Woodland The California Montane Jeffrey Pine (-Ponderosa Pine) Woodland biophysical setting (yellow pine) is the most widely distributed and the largest biophysical setting mapped on National Forest System land within the EIS extent 290,000 acres on the Sequoia, 179,000 acres on the Sierra, and 175,000 acres on the Inyo (figure 5). Yellow pine forests were historically dominated by ponderosa pine (Pinus ponderosa) and/or Jeffery pine (Pinus jeffreyi) with a primarily open canopy structure due to a frequent, low-severity fire regime (LANDFIRE 2007). In the absence of fire, other conifer species become established and eventually co-dominate with yellow pine, making it difficult to discern from the mixed-conifer biophysical setting. Such is the case across much of the yellow pine biophysical setting distribution as a result of fire effective fire suppression. The yellow pine biophysical setting uses the standard five-state vegetation dynamics model. Figure 5. Distribution of the California Montane Jeffrey Pine (-Ponderosa Pine) Woodland and Mediterranean California Dry-Mesic Mixed Conifer Forest and Woodland biophysical settings 11

18 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report The Mediterranean California Dry-Mesic Mixed Conifer Forest and Woodland biophysical setting (drymesic mixed conifer) is mapped to 89,000 acres on the Sierra, and 63,000 acres on the Sequoia National Forests. This forest type is typically codominated by three or more conifer species including: ponderosa pine, sugar pine (Pinus lambertiana), white fir (Abies concolor), or incense cedar (Calocedrus decurrens). The dry-mesic mixed conifer biophysical setting also uses the standard five-state vegetation dynamics model. Table 6. condition results for the California Montane Jeffrey Pine (-Ponderosa Pine) Woodland biophysical setting Landscape Unit (National Forest System acres) 1 Sequoia: Kern River (209,000) Inyo:Mono- Mammoth (105,000) Sierra:High Sierra (103,000) Sequoia: Hume-Tule-Hot Springs (86,000) Sierra:Bass Lake (76,000) Succession Class 2 A B C D E U Reference Percent Current % % Difference Abundant Similar 40%, VCC2: Moderate Current % % Difference Similar Abundant 42%, VCC2: Moderate Current % % Difference Similar Abundant 49%, VCC2: Moderate NA NA Abundant NA Current % % Difference Similar Abundant 49%, VCC2: Moderate Abundant Abundant Current % % Difference Similar Abundant 58%, VCC2: Moderate Abundant Abundant 1 Acres of the biophysical setting, within the landscape unit, on Forest Service land. Values are rounded to the nearest thousand. 2 A: Early-development, B: Mid-development closed, C: Mid-development open, D: Late-development open, E: Late-development closed, U: Uncharacteristic 12

19 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report The yellow pine and dry-mesic mixed conifer biophysical settings are both assigned to fire regime group I (0 to 35 year frequency, surface severity) in the LANDFIRE vegetation dynamics models. We analyzed each biophysical setting at landscape unit level 2. The yellow pine biophysical setting is moderately departed at the biophysical setting level in each of the five landscape units for which it summarized below (table 6). The Sequoia:Kern River landscape unit is the least departed at 40 percent departure and the Sierra:Bass Lake landscape unit is the most departed at 58 percent departure. At the S-Class level, a similar pattern is seen across each landscape unit. Mid- and late-development closed S-Classes (B and E) are in surplus, while only trace amounts of the latedevelopment open S-Class (D) are present. The relative amount of the mid-development open (C) and early-development (A) S-Classes varies across landscape units. The dry-mixed conifer biophysical setting is moderately departed at the biophysical setting level in each of the three landscape units for which it is summarized below (table 7). The Sierra:High Sierra landscape unit is the least departed at 51 percent departure and the Sierra:Bass Lake landscape unit is the most departed at 56 percent departure. At the S-Class level, each unit has a trace amount of the earlydevelopment S-Class (A) and an abundance of the late-development closed S-Class (E). The relative amount of the mid-development closed and open S-Classes (B and C) and the late-development open (D) S-Class varies across landscape units but in general there is relatively more area in closed than in open S- Classes within each unit. Table 7. condition results for the Mediterranean California Dry-Mesic Mixed Conifer Forest and Woodland biophysical setting Landscape Unit (Biophysical Setting acres) 1 Sierra: Bass Lake (56,000) Sequoia: Hume-Tule-Hot Springs (44,000) Sierra: High Sierra (33,000) Succession Class 2 A B C D E U Reference Percent Current % % Difference Similar 56%, VCC2: Moderate Abundant Current % % Difference NA Similar Abundant NA 53%, VCC2: Moderate Current % % Difference %, VCC2: Moderate Abundant 1 Acres of the biophysical setting, within the landscape unit, on Forest Service land. Values are rounded to the nearest thousand. 2 A: Early-development, B: Mid-development closed, C: Mid-development open, D: Late-development open, E: Late-development closed, U: Uncharacteristic NA 13

20 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Mediterranean California Red Fir Forest - Southern Sierra and Cascades variants The Mediterranean California Red Fir Forest biophysical settings (Southern Sierra and Cascades variants) are mapped at high elevations in the upper montane zone of the EIS extent, with the Southern Sierra variant residing above the Cascades variant in elevation (figure 6). Red fir (Abies magnifica) is the canopy dominant or co-dominant in both models but the Southern Sierra variant of the model includes a significant amount of western white pine (Pinus monticola) and generally lacks white fir, whereas the Cascades variant lacks western white pine and may include white fir (LANDFIRE 2007). Both variants are mapped extensively to the Sierra National Forest (197,000 acres of the Southern Sierra variant and 115,000 acres of the Cascades variant). The Southern Sierra variant also comprises 82,000 acres of the Sequoia, and 76,000 acres of the Inyo National Forests. Figure 6. Distribution of the Mediterranean California Red Fir Forest biophysical settings The variants also differ by fire regime. The Southern Sierra variant is assigned to fire regime group III (35 to over 100 year frequency, mixed severity) in the LANDFIRE vegetation dynamics model as a result of discontinuous fuels due to natural breaks such as rock outcrops and wet meadows. The Cascades variant is assigned to fire regime group I (0 to 35 year frequency, surface severity) primarily due to more continuous fuels, however a considerable range of values has been reported in the literature for mixedand surface-severity return intervals in this biophysical setting (LANDFIRE 2007). Both variants use the 14

21 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report standard five-state vegetation dynamics model. We analyzed each biophysical setting variant at landscape unit level 2. The Southern Sierra variant is moderately departed at the biophysical setting level in each of the six landscape units for which it is summarized below (table 8). The Inyo:Mono-Mammoth landscape unit is the least departed at 34 percent departure and the Sequoia:Kern River landscape unit is the most departed at 40 percent departure. At the S-Class level, many S-Classes are within plus or minus 33 percent of the reference proportion, and with the exception of the late-development open S-Class (D) all are within plus or minus 66 percent of the reference proportion. The late-development open S-Class shows the most departure with only trace amounts in five of the six landscape units. Table 8. condition results for the Mediterranean California Red Fir Forest (Southern Sierra variant) biophysical setting Landscape Unit (Biophysical Setting acres) 1 Sierra: High Sierra (157,000) Sequoia: Hume-Tule-Hot Springs (47,000) Sierra: Bass Lake (42,000) Inyo:Mount Whitney (39,000) Succession Class 2 A B C D E U Reference Percent Current % % Difference Similar Similar Similar NA 38%, VCC2: Moderate Current % % Difference Underrepresenterepresented Over- Similar Similar NA VCC 37%, VCC2: Moderate Current % % Difference Overrepresenterepresented Over- Similar Similar NA VCC 37%, VCC2: Moderate Current % % Difference Overrepresenterepresented Over- Similar Similar NA VCC 35%, VCC2: Moderate Current % % Difference Overrepresenterepresented Over- Similar Similar NA VCC 34%, VCC2: Moderate Current % % Difference Overrepresenterepresenterepresenterepresenterepresented Under- Under- Under- Over- NA VCC 40%, VCC2: Moderate Inyo:Mono- Mammoth (35,000) Sequoia: Kern River (33,000) 1 Acres of the biophysical setting, within the landscape unit, on Forest Service land. Values are rounded to the nearest thousand. 2 A: Early-development, B: Mid-development closed, C: Mid-development open, D: Late-development open, E: Late-development closed, U: Uncharacteristic 15

22 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report The Cascades variant shows low departure at the biophysical setting level in both of the landscape units for which it is summarized below (table 9). The Sierra: High Sierra landscape unit is 19 percent departed and the Sierra:Bass Lake landscape unit is 20 percent departed. At the S-Class level, the early- and middevelopment S-Classes are in deficit and the late-development S-Classes are in surplus. All S-Classes are within plus or minus 66 percent of the reference proportion with the exception of the mid-development closed S-Class (B), which basically absent from the landscape units. Table 9. condition results for the Mediterranean California Red Fir Forest (Cascades variant) biophysical setting Landscape Unit (Biophysical Setting acres) 1 Sierra: High Sierra Sierra: Bass Lake Succession Class 2 A B C D E U Reference Percent Current % % Difference Similar 19%, VCC1: Low Current % % Difference VCC 20%, VCC1: Low 1 Acres of the biophysical setting, within the landscape unit, on Forest Service land. Values are rounded to the nearest thousand. 2 A: Early-development, B: Mid-development closed, C: Mid-development open, D: Late-development open, E: Late-development closed, U: Uncharacteristic NA NA Mediterranean California Mesic Mixed Conifer Forest and Woodland The Mediterranean California Mesic Mixed Conifer Forest and Woodland biophysical setting (mesic mixed conifer) is mapped extensively on the west slope of the Sierras (figure 7), comprising 149,000 acres of the Sequoia and 144,000 acres of the Sierra National Forests. This forest type is typically codominated by three or more conifer species including: white fir, ponderosa pine, sugar pine, or incense cedar (LANDFIRE 2007). The mesic mixed conifer biophysical setting is typically found on cooler aspects and at higher elevations than the dry-mesic mixed conifer biophysical setting. The mesic mixed conifer biophysical setting is assigned to fire regime group I (0 to 35 year frequency, surface severity) in the LANDFIRE vegetation dynamics model but also includes a relatively frequent mixed-severity mean fire return interval of 45 years. The biophysical setting uses the standard five-state vegetation dynamics model. We analyzed this biophysical setting at landscape unit level 2. 16

23 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Figure 7. Distribution of the Mediterranean California Mesic Mixed Conifer Forest and Woodland biophysical setting At the S-Class level, the early- and mid-development S-Classes (A, B, and C) are in deficit and the latedevelopment closed S-Class (E) is in surplus for each landscape unit. The late-development open S-Class (D) is similar to the reference proportion in the Sequoia:Hume-Tule-Hot Springs and Sierra:High Sierra landscape units and under-represented in the Sierra:Bass Lake landscape unit. The mesic mixed conifer biophysical setting shows low departure at the biophysical setting level in the Sequoia:Hume-Tule-Hot Springs (30 percent) and Sierra:High Sierra (28 percent) landscape units and moderate departure (47 percent) in the Sierra:Bass lake landscape unit (table 10). 17

24 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Table 10. condition results for the Mediterranean California Mesic Mixed Conifer Forest and Woodland biophysical setting Landscape Unit (Biophysical Setting acres) 1 Sequoia: Hume-Tule-Hot Springs (117,000) Sierra:Bass Lake (82,000) Sierra:High Sierra (65,000) Succession Class 2 A B C D E U Reference Percent Current % % Difference Similar 30%, VCC1: Low Current % % Difference %, VCC2: Moderate Abundant Current % % Difference Similar 28%, VCC1: Low 1 Acres of the biophysical setting, within the landscape unit, on Forest Service land. Values are rounded to the nearest thousand. 2 A: Early-development, B: Mid-development closed, C: Mid-development open, D: Late-development open, E: Late-development closed, U: Uncharacteristic NA NA NA Great Basin Pinyon-Juniper Woodland The Great Basin Pinyon-Juniper Woodland biophysical setting (pinyon-juniper) is mapped extensively on the Inyo National Forest (figure 8), comprising 229,000 acres. This forest type can be dominated by a mix of pinyon pine (Pinus monophylla) and juniper (Juniperus osteosperma), or nearly pure stands of either species (LANDFIRE 2007). Common associates include mountain mahogany (Cercocarpus ledifolius) and sagebrush (Artemisia sp.). There is much uncertainty in regards to the historical fire regime of this biophysical setting due to a lack of quantitative data (LANDFIRE 2007). The current fire regime is influenced by climate change and the presence of invasive plant species, particularly cheatgrass (Bromus tectorum) and red brome (Bromus rubens), which increase fire frequency. These issues make it challenging to apply natural range of variability concepts to this biophysical setting. We used the four-state vegetation dynamics model and reference proportions from the Bodie Hills Conservation Action Plan (Provencher et al. 2009) to analyze this biophysical setting. S-Class A represents early-development; S-Class B represents shrub dominated, mid-development; S-Class C represents tree dominated mid-development; and S-Class D represents late-development. 18

25 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Figure 8. Distribution of the Great Basin Pinyon-Juniper Woodland biophysical setting The pinyon-juniper biophysical setting is assigned to fire regime group III ( year frequency, mixed severity) in the LANDFIRE vegetation dynamics model. We analyzed this biophysical setting at landscape unit level 2. The pinyon-juniper biophysical setting is moderately departed at the biophysical setting level in each of the three landscape units for which it is summarized below (table 10). The Inyo:Mono-Mammoth landscape unit is the least departed at 38 percent departure and the Inyo:White Mountain landscape unit is the most departed at 53 percent departure. At the S-Class level, the Inyo:White Mountain and Inyo:Mono- Mammoth landscape units follow the same pattern of departure. They are both over-represented by the tree dominated, mid-development S-Class (C) and in deficit of the early-development (A), shrub dominated, mid-development (B), and late-development (E) S-Classes. The Inyo:Mount Whitney landscape unit is also deficit in the early- and late-development S-Classes but has a similar proportion of the shrub and tree dominated S-Classes (B and C) to the reference condition. 19

26 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Table 11. condition results for the Great Basin Pinyon-Juniper Woodland biophysical setting Landscape Unit (Biophysical Setting acres) 1 Inyo:White Mountain (147,000) Inyo:Mount Whitney (53,000) Inyo:Mono- Mammoth (29,000) Succession Class 2 A B C D E U Reference Percent NA 0 Current % NA 8 % Difference NA %, VCC2: Moderate NA Abundant Current % NA 40 % Difference NA 100 Similar Similar NA Abundant 51%, VCC2: Moderate Current % NA 8 % Difference NA %, VCC2: Moderate 1 Acres of the biophysical setting, within the landscape unit, on Forest Service land. Values are rounded to the nearest thousand. 2 A: Early-development, B: Mid-development (shrub dominated), C: Mid-development (tree dominated), D: Late-development, U: Uncharacteristic NA Abundant Central and Southern California Mixed Evergreen Woodland The Central and Southern California Mixed Evergreen Woodland biophysical setting (mixed evergreen) is mapped along an elevation gradient of the lower montane zone (figure 9), comprising 130,000 acres of the Sequoia National Forest and 101,000 acres of the Sierra National Forest. This forest type is dominated by canyon live oak (Quercus chrysolepis) and black oak (Quercus velutina) with scattered conifers (LANDFIRE 2007; USDA-FS 2015c, 2015d) and typically forms an ecotone between the foothill oak and pine woodland and mixed conifer vegetation types. 20

27 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Figure 9. Distribution of the Central and Southern California Mixed Evergreen Woodland biophysical setting Fire is the most common disturbance agent of this biophysical setting and it is assigned to fire regime group I (0 to 35 year frequency, surface severity) in the LANDFIRE vegetation dynamics model. This biophysical setting uses a three-state model. S-Class A represents early-development, S-Class B represents mid-development, and S-Class C represents late-development. The canopy structure is typically closed across all classes. We analyzed this biophysical setting at landscape unit level 1. The mixed evergreen biophysical setting is moderately departed at the biophysical setting level in each of the primary landscape units for which it is summarized below (table 12). At the S-Class level there is a strong deficit in the early- and late-development S-Classes with greater than 80 percent of the acres falling in the mid-development class. 21

28 Southern Sierra Nevada Wildfire Risk Assessment: Condition Assessment Report Table 12. condition results for the Central and Southern California Mixed Evergreen Woodland biophysical setting Landscape Unit (Biophysical Setting acres) 1 Sierra:High Sierra:South (39,000) Sequoia:Kern River:West (35,000) Sierra:Bass Lake:West (34,000) Sequoia:Hume-Tule-Hot Springs:Hot Springs (29,000) Sierra:Bass Lake:East (26,000) Sequoia:Hume-Tule-Hot Springs:Tule River (25,000) Succession Class 2 A B C D E U Reference Percent NA NA Current % NA NA 1 % Difference NA NA 100 NA NA Abundant 48%, VCC2: Moderate Current % NA NA 1 % Difference NA NA 100 NA NA Abundant 50%, VCC2: Moderate Current % NA NA 2 % Difference NA NA 100 NA NA Abundant 41%, VCC2: Moderate Current % NA NA 1 % Difference NA NA 100 NA NA Abundant 53%, VCC2: Moderate Current % NA NA 1 % Difference NA NA 100 NA NA Abundant 50%, VCC2: Moderate Current % NA NA 1 % Difference NA NA 100 NA NA Abundant 49%, VCC2: Moderate 1 Acres of the biophysical setting, within the landscape unit, on Forest Service land. Values are rounded to the nearest thousand. 2 A: Early-development, B: Mid-development C: Late-development, U: Uncharacteristic 22