Travis AFB_GMP 2024 2nd Ed_21Dec2024.pdf

Grazing Management Plan

Version 2

Travis Air Force Base, California

Prepared for the U.S. Air Force by:

Jaymee Marty, PhD, Marty Ecological Consulting, Inc., Sacramento, CA

Lawrence Ford, PhD1, Rangeland Conservation Science, Felton, CA

Felix Ratcliff, PhD2, Rangeland Conservation Science, Berkeley, CA

Kaveh Motamed, MS3, Rangeland Conservation Science, Berkeley, CA

Joyce Qiao, MS, Rangeland Conservation Science, Berkeley, CA

Peter Hopkinson, PhD4 (author of 2017 revised edition; Center for Environmental Management of Military Lands, Colorado State University)

1Certified Rangeland Manager (CRM) #M70, California Board of Forestry, 2CRM #M123, 3CRM #M134, 4CRM #M93

December 2024

TRAVIS AIR FORCE BASE GRAZING MANAGEMENT PLAN

Table of Contents

List of Acronyms 5

1.0 Introduction 6

2.0 Background 8

3.0 Goals, Objectives, and Performance Standards for Grazing Program 12

4.0 Existing and Desired Conditions, Predicted Effects, and Grazing Management

Considerations 15

4.1 Land-use History 15

4.2 Climate, Climate Change, and Extreme Weather 15

4.3 Topography, Hydrology, and Soils 17

4.4 Vegetation Types 22

4.5 Special-Status Biological Resources Sensitive to Grazing 23

4.5.1 Vernal pool ecosystems 23

4.5.2 Special Status Plants and Animals 23

4.6 Cultural Resources 31

4.7 Fuel Loads, Fire Hazards, and Fire History 31

4.8 Infrastructure Conditions and Improvements 32

4.8.1 Fences 33

4.8.2 Watering Troughs 35

4.9 Equestrian Center 36

5.0 Invasive Pest Plants 39

6.0 Grazing Capacity Assessment 45

6.1 Summary 45

6.2 Grazing Capacity Calculations 46

7.0 Grazing Management Strategy 48

7.1 Summary 48

7.2 General Provisions 48

7.3 Flexibility and Adjustments of Stocking Rates 48

7.4 Grazing Period 49

7.5 Grazing Management Areas 49

7.6 Livestock Movement Between Pastures 50

7.7 Supplemental Feeding 52

7.8 Livestock Distribution 52

7.9 Grazing to Reduce Fire Hazards 52

8.0 Monitoring and Adaptive Management 53

8.1 Compliance Monitoring 53

8.1.1 RDM Monitoring 54

8.1.2 Grazing Use Monitoring 55

8.2 Effectiveness Monitoring for Management Actions 56

8.2.1 Rare Plant Monitoring 56

8.2.2 Vernal Pool Plant Community Monitoring 56

8.2.3 Upland Plant Community Monitoring 57

8.2.3 Photopoint Monitoring. 57

8.3 Adaptive Management Approach 58

8.4 Additional Provisions 59

8.6 Rationale for Inclusion of Monitoring Variables 61

8.7 Data Management and Analysis 62

9.0 References Cited 64

List of Figures

Figure 1. Regional map for Travis AFB. 7

Figure 2. Grazing Pastures on Travis Air Force Base. 11

Figure 3. Annual (January to December) rainfall in inches, Fairfield, California, 2000 to 2023

(green line is mean; Western Regional Climate Center, www.wrcc.dri.edu: accessed

December 16, 2024). 16

Figure 4. Slope Classes on Travis Air Force Base. 18

Figure 5. Floodplains on Travis Air Force Base (CSU 2021). 19

Figure 6. Soil Types on Travis Air Force Base. 21

Figure 7. Equestrian Center Infrastructure. 38

List of Tables

Table 1. Travis AFB Pastures including Livestock Type and Size (acres). 10

Table 2. Travis AFB Grazing Management Goals, Objectives and Performance Standards. 13

Table 3. 1950-2023 mean monthly and annual precipitation in inches, Fairfield, California

(Western Regional Climate Center, www.wrcc.dri.edu: accessed December 16, 2024). 16

Table 4. Total acreage and rating for erosion hazard and compaction risk by soil series within

Travis AFB grazing pastures (Bates 1977; NRCS 2024; compiled by J. Qiao). 20

Table 5. Special-Status Species and Grazing Management Considerations. 27

Table 6. Average fuel loads in the fall, as measured by RDM (lbs/acre) in the fall from 2018 to

2022, Travis AFB Grazing Pastures (H.T. Harvey monitoring data). 32

Table 7. Livestock Infrastructure by Pasture. 33

Table 8. Pest Plants and Control Considerations. 41

Table 9. Animal Unit Equivalents (AUEs) Adapted from The National Range and Pasture

Handbook (NRCS 2022). 45

Table 10. Estimated grazing capacity in Animal Unit Months (AUM) for Travis AFB Pastures based on RDM calculations. 47

Table 11. Cattle Movements and Associated Risks, Travis AFB, CA. 51

Table 12. Summary of Adaptive Management Decisions, Travis AFB, CA. 58

Table 13. Annual Monitoring Summary. 60

List of Appendices

Appendix A: Land Use Regulations

Appendix B: Memorandum regarding license to operate an Equestrian Center at Travis

AFB, 1996; and Travis Air Force Base Instruction 34-201 – Managing nonappropriated funds, Travis Equestrian Center, 2011

Appendix C: Grazing Management Planning for Extreme Weather

Appendix D: Natural Resource Conservation Service 2019 Livestock Fence Specifications and

2012 Wildlife Friendly Fence Specifications

List of Acronyms

AFB Air Force Base

AUE animal unit equivalent

AUM animal unit month

BASH Bird/Wildlife Aircraft Strike Hazard

CEMML Center for Environmental Management of Military Lands, Colorado State Univ.

CTS California tiger salamander

DAF United States Department of the Air Force

EDRR emergency detection rapid response

GIS geographical information system

GPS global positioning system

INRMP Integrated Natural Resources Management Plan lbs pounds

NISC National Invasive Species Council

NRCS USDA Natural Resources Conservation Service

RDM residual dry matter

RMAT Range Management Assistance Team

SCS USDA Soil Conservation Service

UC ANR University of California Agriculture and Natural Resources

US United States

USAF United States Air Force

USDA United States Department of Agriculture

USFWS United States Fish and Wildlife Service

YST yellow starthistle

1.0 Introduction

Travis Air Force Base (AFB) is in Solano County, California, within the city limits of Fairfield

(Figure 1). In common with many military installations, Travis AFB requires a sizable land base as part of its defense mission and for security and safety purposes (Travis AFB 2022). Although much of Travis AFB’s land is developed, there are several small, undisturbed natural resource areas (Travis AFB 2022). In compliance with relevant laws and regulations, Travis AFB manages its natural resources to meet conservation and other management goals (Travis AFB 2022). As part of this natural resources management, Travis AFB has operated a livestock grazing program since 1977 (RMAT 2000).

Grazing management on Travis AFB is intended to follow an adaptive management approach.

Objective 6.3 in the Travis AFB Integrated Natural Resources Management Plan (INRMP) calls for the Air Force to “adaptively manage all resources in the rangeland ecosystem to be consistent with the military mission and environmental regulations” (Travis AFB 2022). This Grazing

Management Plan (GMP) is intended to help guide Travis AFB and its grazing lessees in their grazing management actions so that the Base meets its natural resources management goals and objectives.

The 2025 version of the GMP presents several substantive updates to the 2017 GMP written by

Dr. Peter Hopkinson. Specifically, this version of the GMP:

• updates the GMP to conform to the 2022 Travis AFB INRMP

• adds grazing prescriptions for the pastures added since 2017 including updates to infrastructure and pasture configurations

• incorporates monitoring and research information for Travis AFB relating to overall grazing management as well as special status species management

• combines the monitoring methodology drafted by H.T. Harvey (2019) into the GMP and revises these methods based on data collected since 2019

• adds information about climate change impacts and planning for severe events

• updates information on rangeland weeds

Figure 1. Regional map for Travis AFB.

2.0 Background

Travis AFB covers 5,137 acres, of which 628.1 acres are currently part of Travis AFB’s grazing program, 479.3 acres grazed by cattle in 8 pastures, 64.5 acres to be grazed by cattle or sheep, and 84.3 acres occupied by horses in 9 pastures/turnouts (Table 1 and Figure 2). Figure 2 includes the additional pastures (14-20) that were incorporated into the grazing program since publication of the first version of the GMP (Hopkinson 2017). Land uses surrounding the base include agriculture and open space to the north, east, and south and urban and commercial uses to the west (Travis AFB 2022). Prior to the early 1940s, the land that Travis AFB now occupies was used for sheep and cattle grazing (Dingler 2002, Goerke-Shrode 2007).

Travis AFB’s livestock grazing program started in October 1977 with the lease of 145 acres for cattle grazing (RMAT 2000). The land leased for grazing was necessary for “the quantity-distance criteria for explosive storage and handling facilities” and so could not be declared excess (Hopkinson 2017). The US Army Corps of Engineers Sacramento District advised Travis

AFB regarding leasing the land, monitored the lease, and collected the grazing fees (Hopkinson

2017). In March 1982, Dr. Mel George of UC Davis toured Travis AFB’s grazing land and subsequently helped develop a grazing management plan for the base (George 1982). By 1996, 605 acres of Travis AFB were being grazed, 475 leased for cattle grazing and 130 acres for horse pastures under a use license with the Travis Saddle Club (Hopkinson 2017). The same acreage for cattle and horse grazing was reported in 2000 and 2003 (RMAT 2000, Travis AFB 2003).

The most recent cattle grazing lease dates to 2003, with a 5-year term and for 280 acres of grazing land; the lessee was Tony Garcia, Valley Cattle Company. In 2007, a supplemental agreement transferred the lease to Tony Martin and Bill Traylor of J/V Angus. In 2009 and 2010, supplemental agreements extended the term of the lease to September of the following year, and in 2011, extended the term to September 2016, with a reduced cattle-grazing area of 244 acres down from the initial 280 acres. In 2012, in a further supplemental agreement, Bill Traylor became the sole lessee. Since the expiration of the lease’s term in September 2016, Mr. Traylor continued to graze his livestock on base under the terms of the 2003 lease and supplemental agreements through a “holdover” arrangement (Hopkinson 2017). Mr. Traylor signed a 5-year lease in 2018 and grazed cattle through June 2022. A new grazing lease has not been approved by the USAF since 2022. Future cattle-grazing leases will have 5-year terms and will be sent out for rebidding every five years, in accordance with the general provisions of Air Force Instruction 32-

9003 (Hopkinson 2017). Appendix A contains grazing land use regulations, drafted in 2016, that are likely to be modified and incorporated into future leases.

The most recent cattle grazing lessee, Bill Traylor, ran a cow-calf and stocker operation at Travis

AFB (H.T. Harvey 2022). In central California, cow-calf operations maintain a mother cow herd year-round and produce calves that are typically sold after weaning in late spring. Stocker operations graze weaned calves on rangeland for several months, in central California usually during late winter and spring, before selling them or moving them elsewhere in the summer. Mr.

Traylor moved animals onto base in November or December and usually removed them by May, although the lease allowed him to keep the animals on base through June. In some years, cattle were left on pastures later than June, including during the 2021-2022 grazing season where cattle were allowed to graze Pastures 1 and 14 into August 2022 (H.T. Harvey 2022).

The most recent grazing lease expired in 2022, and Travis AFB is in the process of developing a new lease to send out for bid. Since 2022, cattle grazing has not occurred on base, and some of the pastures were occasionally managed with mowing and/or sheep grazing when funding was available. Studies have shown that a lack of grazing can have negative impacts on vernal pools and grasslands including increases in invasive species cover, excessive thatch build up and decreases in native plant species populations (Marty 2005, 2015). The lack of management of vernal pools may be having a particularly negative impact on the endangered Contra Costa goldfields (CCG; Lasthenia conjugens) population in the Aero Club Conservation Area (Pasture

14). A study looking at the effects of cattle grazing on the vernal pools in the Aero Club

Conservation Area showed that grazing helps to maintain native species richness and cover and can enhance CCG populations in some years (Marty 2021, 2022a). A lack of grazing was associated with higher cover of exotic species, increased levels of thatch and extensive cover of algal matting that eliminated CCG from some pools.

Since 2018, Travis AFB has contracted with sheep grazing companies to graze pastures 15, 19 and 20 with the goal of reducing invasive species populations while also reducing fuel loads

(Marty 2023). Unlike cattle grazing where the Air Force receives payment from the operator leasing the land, sheep grazing has required payment for the service. Funding for sheep grazing has come from the Natural Resources Program beginning in 2018 and ending in 2024. The Air

Force did not fund the sheep grazing program through the Natural Resources Program in 2025 and future funding is uncertain.

The Travis Equestrian Center (also referred to as the Travis Saddle Club) has maintained horse barns, riding facilities, and associated horse pastures and turnouts since at least the early 1980s

(George 1982), although not in its current location. The move to the current location in the 1980s involved the loss of approximately half of Travis AFB’s horse-pasturing capacity (Hopkinson

2017).

The Travis Equestrian Center does not currently operate under a lease or license, in accordance with a Department of the Air Force Memorandum (DAF 1996; Appendix B). The operations of the Equestrian Center are governed by Travis Air Force Base Instruction 34-201 (Travis AFB

2011; Appendix B).

Table 1. Travis AFB Pastures including Livestock Type and Size (acres).

Travis AFB

Pasture

Livestock Use Size (acres)

Pasture 1 Cattle 178

Pasture 2 Cattle 81

Pasture 3 Cattle 15

Pasture 4 Cattle (corral) 2

Pasture 5 15 Horse turnouts 9

Pasture 6 Horse 16

Pasture 7 Horse 13

Pasture 8 Horse 19

Pasture 9 Horse 15

Pasture 10 Horse (not currently used)

Pasture 11 5 Horse turnouts 0.8

Pasture 12 2 Horse turnouts 0.4

Pasture 13 1 Horse turnout 0.05

Pasture 14 Cattle 106.7

Pasture 15 Cattle or Sheep 9.5

Pasture 16 Cattle 62.2

Pasture 17 Cattle 5.6

Pasture 18 Cattle 28.8

Pasture 19 Cattle or Sheep 36.6

Pasture 20 Cattle or Sheep 18.4

Total Acreage - All Pastures 628.1

Figure 2. Grazing Pastures on Travis Air Force Base.

3.0 Goals, Objectives, and Performance Standards for Grazing

Program

Travis AFB’s ecosystem management goals are defined in the INRMP (Travis AFB 2022). The following INRMP goal, objective and projects relate directly to grazing management on Travis

AFB:

Goal 6: Rangeland, recreational areas, and other man-made or natural landscapes enhanced or expanded to conserve natural resources and sustain mission integrity

Objective 6.3: Adaptively manage all resources in the rangeland ecosystem to be consistent with the military mission and all environmental regulations.

Project 6.3.1: Implement a grazing monitoring program that evaluates and measures grazing impacts on the vernal pools and associated grasslands within grazed areas.

Project 6.3.2 Establish grazing exclosures and monitor vegetation changes as a result of adding grazing management in the Aero Club Conservation Area.

Project 6.3.3: Describe current conditions of plant composition in grazing units and monitor landscape vegetation trends using photographic analysis and provide any GIS data collected to be incorporated into Travis AFB GIS database.

The goals and objectives in the original GMP (Hopkinson 2017) and Grazing Monitoring Plan

(H.T. Harvey 2019) were modified for this edition to incorporate lessons learned from implementation of these plans. These conclusions were limited to the first five years of implementation (2017-2022) since cattle grazing ceased in 2022. A set of performance standards was added to complement the goals and objectives and provide measurable targets for the monitoring elements.

Table 2. Travis AFB Grazing Management Goals, Objectives and Performance Standards.

Goals Objectives Performance Standard

1. Protect and enhance vernal pool ecosystem functions and processes.

1.1 Graze vernal pool ecosystem to

maintain hydrologic function within vernal pools to support vernal pool native plants and animals.

1.2 Maintain pool-adjacent

uplands residual dry matter (RDM) in fall between minimum and maximum recommended levels.

P.1.1 Inundation monitoring in multiple designated reference pools (trend based on multi-year repeat measures).

P.1.2 RDM monitoring (fall)— multiple reference samples in uplands adjacent to pools with pasture average ranging between 500 to 2,000 pounds per acre.

2. Protect and provide a conservation benefit for federal and state listed species, state species of concern, and other at-risk species, including rare plants.

2.1 Implement objectives 4.1, 4.2, 4.3, and 5.1 below.

General – in grasslands, move towards a habitat mosaic to support multiple special status species (and their prey) with varying requirements (grazed, lightly/rotationally grazed, ungrazed).

P.2.1 Monitor population density of

Contra Costa goldfields in grazing pastures (trend based on multi-year repeat measures)

P.2.2 Monitor cover of vernal pool species in grazing pastures (trend based on multi-year repeat measures)

P.2.3 Monitor presence of listed vernal pool branchiopods in reference pools within grazing pastures (trend based on multi-year repeat measures)

Compliance with P.1.1, P.1.2, P.4.1, P.4.2, and P.5.1.

3. Maintain and improve rangeland ecosystem functions and processes

3.1 Maintain RDM in fall and

herbaceous height in spring between minimum and maximum recommended levels to benefit habitat.

3.2 Reduce cover of widespread

invasive plant species.

Compliance with P.1.1, P.1.2, P.4.1, and P.5.1.

4. Maintain or increase populations of native plants that contribute to floral and faunal biological diversity.

4.1 Reduce cover of widespread

invasive species medusahead (Elymus caput- medusae).

4.2 Reduce cover of widespread

invasive species yellow starthistle

(Centaurea solstitialis).

4.3 Eliminate incipient populations

of new but not widespread invasive species, such as barb goatgrass

(Aegilops triuncialis) and stinkwort

(Dittrichia graveolens), by

P.4.1 Monitor invasive species cover— map populations and provide visual estimates of cover (trend based on multi-year repeat measures).

P.4.2 Monitor native species cover— visual estimates of cover by species along transects and in grazing monitoring plots (trend based on multi-year repeat measures).

Goals Objectives Performance Standard implementing a rapid response protocol.

4.4 Monitor native species richness

in grazed pastures.

5. Manage and improve rangeland vegetation to provide high quality livestock forage on a sustainable basis to maintain benefits received from livestock grazing leases.

5.1 Eliminate known populations

of barb goatgrass and stinkwort within five years (invasive species unpalatable to livestock).

5.2 Implement Objectives 4.1-3.

Compliance with P.1.2 and P.4.1

6. Reduce wildland fire risk and its potential effects on base facilities and natural resources.

6.1 Reduce fine herbaceous fuels

through managed livestock grazing.

Compliance with P.1.2.

7. Ensure Travis AFB grazing program supports the military mission of the installation.

7.1 Maintain fencing integrity to

avoid livestock in sensitive military areas.

7.2 Remove livestock carcasses

from pastures within 24 hours to reduce BASH risks.

7.3 Ensure ranching practices are

flexible, and ranchers are available within 24 hours’ notice if livestock needs to be moved for mission priorities.

P.7.1 Livestock fencing—survey of fence conditions (compliance with state livestock fencing law and regulations) during fall and spring monitoring.

P.7.2 Compliance with grazing lease provisions for lessee’s coordination with base commander and removal of dead livestock.

4.0 Existing and Desired Conditions, Predicted Effects, and Grazing

Management Considerations

4.1 Land-use History

Land-use history can have significant impacts on current vegetation species composition, structure, and productivity. Previous cultivation is linked to the absence of native perennial bunchgrasses and native annual forbs in California grasslands and the elimination of mima mound topography found in vernal pool grasslands (Bartolome et al. 2007).

The land occupied by Travis AFB was originally public land that bordered on Rancho Los Putos, Rancho Los Ulpinos, and Rancho Tolenos land grants from the Mexican government dating from about 1841. Prior to this time, the inhabitants were small, scattered groups of Suisun/Patwin

Indians (Travis AFB 2016). The destruction of the natural communities began in approximately

1890 when the land contained within the present-day Travis AFB was first claimed and permanently inhabited by European settlers. The early custom of free-range cattle grazing had a significant impact on the landscape, as did the subsequent practice of dry land wheat and barley farming. At the time of the original land acquisition by the federal government in June 1942, the land was acquired from approximately 20 owners (Travis AFB 2016).

Prior to the construction of the military facility in the early 1940s, the land on which Travis AFB is now located was used for sheep and cattle grazing (Dingler 2002, Goerke-Shrode 2007).

Several of the soil series found at Travis AFB are also suitable for crop agriculture, including some soil series designated as high-quality farmland (Bates 1977), suggesting that at least some areas of Travis AFB may have been cultivated in the 19th and early 20th Centuries. Information on specific locations that have been cultivated, if available, may prove useful in prioritizing future grassland restoration activities.

4.2 Climate, Climate Change, and Extreme Weather

The Travis AFB area has a typical California Mediterranean climate with cool, wet winters and hot, dry summers. Annual average precipitation is about 25 inches; 85% of that rain falls between November and March (Table 3). Averages can be misleading, however, as rainfall amount and pattern vary significantly from year to year (Figure 3), with consequent fluctuations occurring in vegetation production and species composition between years. Travis AFB’s average annual low temperature is 47°F and its average annual high is 73°F (Travis AFB 2022).

The Fairfield area, including Travis AFB, is known for its almost continuous wind, blowing primarily from the Pacific Ocean and the San Francisco Bay but also from the north. During the summer, the north winds are hot and dry, producing temperatures over 100°F and substantially increasing the risk of wildfire (Travis AFB 2022).

Table 3. 1950-2023 mean monthly and annual precipitation in inches, Fairfield, California

(Western Regional Climate Center, www.wrcc.dri.edu: accessed December 16, 2024).

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Annual

4.75 4.01 3.17 1.38 0.50 0.14 0.02 0.05 0.22 1.28 2.67 4.45 23.10

The San Francisco Bay Area, including the western half of Solano County (and Travis AFB) is expected to have approximately the same amount of annual precipitation in future years as in previous years, but with winter storms varying more in intensity and damage, and more long periods of dry or wet (California Climate Adaptation Strategy, https://climateresilience.ca.gov/regions/sf-bay-area.html, accessed July 20, 2024). Average temperatures in the region are expected to warm by 3–4.5°F by 2050 with more and longer droughts and increased wildfire risk. More flooding is expected, especially in areas closer to sea level.

Figure 3. Annual (January to December) rainfall in inches, Fairfield, California, 2000 to

2023 (green line is mean; Western Regional Climate Center, www.wrcc.dri.edu: accessed

December 16, 2024).

Periods of more drought and summer heat might reduce habitat quality for amphibians and reptiles (California Climate Adaptation Strategy, https://climateresilience.ca.gov/regions/sf-bay-area.html, accessed July 20, 2024). More wildland fires might also impact upland birds and mammals. This might lead to an increase in dry shrubs fueling wildfires. With extended periods of rainfall, reduced grazing and wildfire, grassland production might increase, and northern coastal scrub might expand into grasslands (Ford and Hayes 2007).

Fairfield, CA Annual Precipitation

(inches) 2000 to 2023 (Mean) http://www.wrcc.dri.edu/ https://climateresilience.ca.gov/regions/sf-bay-area.html http://www.wrcc.dri.edu/ https://climateresilience.ca.gov/regions/sf-bay-area.html https://climateresilience.ca.gov/regions/sf-bay-area.html

Extreme Weather Events

Droughts or floods, persistently high air temperatures, or heavy rains are common in the San

Francisco Bay region’s grasslands and appear to be occurring more often in the last decade.

These weather conditions can have significant impacts on rangeland resources and managers, and associated livestock operations such as:

• dry impermeable soil, suppressing herbaceous growth and reducing vernal pool inundation

• reduced quality and quantity of forage for livestock

• reduced livestock grazing area available

• fire hazards associated with high herbaceous production, especially early in the fire season and with any dying and fallen trees and shrubs

• soggy hills and trails causing increased hoof traffic effects

• landslides and soil erosion causing sedimentation of vernal pools and drainages, and reduced herbaceous growth

• stock pond under-filling or inundation and over-filling, and dam breaks

• damage to roads and other infrastructure

• smoke pollution and reduced visual access

• livestock requiring evacuation and mortality losses

Tracking extreme weather impacts and responding to urgent needs can be difficult and expensive. While weather each year is difficult to predict, occurrences of extreme conditions can be recognized, and some of these impacts can be planned for, to minimize damages and costs

(see Appendix C).

4.3 Topography, Hydrology, and Soils

Travis AFB’s grazing areas are predominantly flat or gently sloped (Travis AFB 2022). A few areas within Pastures 1, 7, 14, 19 and 20 have slopes that exceed 10% (Figure 4). Elevations at

Travis AFB range from 15 feet in the southwest corner of the Base to 140 feet along the Base’s northern boundary (Travis AFB 2016).

Union Creek, flowing in two branches on Travis AFB, provides the primary watershed drainage for the Base (Travis AFB 2022). Currently, there is no livestock grazing in the vicinity of Union

Creek. A recent study identifying the 100 and 500-year floodplain extent on Travis AFB was reviewed and approved by the Federal Emergency Management Agency (Figure 4; CSU 2021).

Sections of all pastures on Travis AFB fall within these floodplains. The maximum flood depth is projected to be 13 feet, and the maximum flood velocity is projected to be 6 feet/second.

Ten soil series are mapped by the USDA Natural Resources Conservation Service (NRCS) in the grazing pastures at Travis AFB (Table 4; Figure 6). These soil series have no associated NRCS range vegetation production estimates, perhaps because the soil series are considered primarily agricultural rather than range sites (i.e., a "higher" potential use than range). A more modern and

Figure 4. Slope Classes on Travis Air Force Base.

Figure 5. Floodplains on Travis Air Force Base (CSU 2021).

useful method for determining herbaceous forage production estimates (and thus grazing capacity) is provided in Section 6. Soil erosion hazard is rated mostly as slight for the Travis

AFB grazing area soils (NRCS Web Soil Survey, accessed July 21, 2024). Erosion is a moderate hazard for the higher sloped soils (Dibble-Los Osos loams and Millsholm loam), which together compose only 1% of the soils on the base. Soil compaction risk associated with off-road vehicular traffic (and sometimes concentrated cattle/sheep traffic in narrow zones), is rated mostly medium for the Travis AFB grazing area soils (NRCS Web Soil Survey, accessed July

21, 2024). These ratings indicate resistance to expected grazing impacts on all soils.

Table 4. Total acreage and rating for erosion hazard and compaction risk by soil series within Travis AFB grazing pastures (Bates 1977; NRCS 2024; compiled by J. Qiao).

Soil series Code Acres Erosion hazard

Compaction

Risk

Altamont-San Ysidro-San Benito complex, 2-9% slopes AlC 196.42 Slight Low

Antioch-San Ysidro complex, 0-2 % slopes AoA 253.6 Slight Medium

Antioch-San Ysidro complex, thick surface, 0-2 % slopes AsA 79.2 Slight Medium

San Ysidro sandy loam, 0-2 % slopes SeA 27.7 Slight Medium

Omni clay loam Om 8.6 Slight Medium

Clear Lake clay, 0-2 % slopes CeA 2.8 Slight Medium

Borrow pit BP 21.4 Not rated Not rated

Corning gravelly loam, 0-12% slopes, MLRA 17 CvD2 26.2 Slight Medium

Dibble-Los Osos loams, 9-30% slopes DbE 0.3 Moderate Medium

Millsholm loam, 15-30% slopes, MLRA 15 MmE 6.5 Moderate Medium

Total 622.72

Figure 6. Soil Types on Travis Air Force Base.

4.4 Vegetation Types

The primary vegetation type of Travis AFB’s grazing pastures is Valley grassland, also known as

California annual grassland. California’s Valley grassland type is found in the Central Valley, the foothills surrounding the Central Valley, including the central and southern Coast Ranges, and parts of the Transverse and Peninsula Ranges (Bartolome et al. 2007). Two hundred twenty-six herbaceous plant species occur on Travis AFB. Composites (Asteraceae) and grasses (Poaceae) are the most dominant families, comprising one-third of all species present. The herbaceous flora includes 109 species (48%) that are not native to California. Vernal pools provide habitat for over 110 species or just over 44% of all taxa found on the base. Furthermore, the three species listed by the California Native Plant Society (CNPS) as rare, threatened, or endangered that occur on Travis AFB reside in vernal pools. These are Contra Costa goldfields (Lasthenia conjugens), San Joaquin spearscale (Exriplex joaquiniana) and alkali milkvetch (Astragalus tener var. tener) (Travis AFB 2022).

Non-native annual grasses and forbs have dominated this grassland type for over two centuries, and in most areas, native plants make up only a very small percentage of the total cover (Barry et

al. 2006). Despite this, numerous native plant species remain, generally at very low density, and can make up a significant proportion of the species richness (i.e., number of species). Most of these native species are likely to be annual forbs.

Valley grasslands exhibit considerable spatial and temporal variation at many scales. Annual rainfall amount and pattern, temperatures during the growing season, variation in soil chemistry and texture, topographic diversity, and land-use history, among other variables, largely determine plant species composition, biomass production, and dominance relationships. Management activities such as livestock grazing generally do not cause spatially or temporally consistent changes in grassland community composition at the landscape level (Jackson and Bartolome

2002). Livestock grazing is a useful tool for reducing grassland fuel loads, for reducing vegetative biomass, especially of non-native grasses, and these changes can benefit native plant and animal species (see Section 4.5). Grazing can be used for altering vegetation structure, which can help achieve Bird/Wildlife Aircraft Strike Hazard (BASH) program goals, and, when carefully planned and implemented, for controlling some rangeland invasive plant species.

Within the Valley grasslands, several smaller specialized habitat types can occur that make a significant contribution to native biodiversity (Bartolome et al. 2014). The vernal pools that occur on Travis AFB are one such specialized habitat. The base’s vernal pool systems are classified as

Northern claypan vernal pools and vernal swales (Marty 2016).

Riparian vegetation occurs along Union Creek, but as noted above, this area is not grazed by livestock (Travis AFB 2022). Union Creek riparian vegetation comprises some small patches of willow (Salix spp.), coyote brush (Baccharis pilularis), native and non-native herbaceous species, including the invasive perennial pepperweed (Lepidium latifolium), and native emergent vegetation such as cattail (Typha spp.) and tule (Schoenoplectus acutus; Travis AFB 2022).

4.5 Special-Status Biological Resources Sensitive to Grazing

4.5.1 Vernal pool ecosystems

Vernal pools and swales are found within the Valley grasslands on Travis AFB. Vernal pools are shallow depressions or small, shallow ponds that fill with water during the rainy season and then dry out during the spring, becoming completely dry by late spring or early summer. This hydrologic regime supports the unique plant and animal communities characteristic of vernal pools. Vernal swales are ecologically and floristically related to vernal pools; however, vernal swales are drainage ways or poorly defined depressions that convey water seasonally and hold standing water for relatively short periods.

Vernal pool specialist plants typically germinate and begin to grow underwater, but their adult life generally occurs in much drier conditions. Endemic vernal pool tadpole and fairy shrimp species, several of which are federally listed, must also cope with desiccation. The federally listed California tiger salamander (CTS; Ambystoma californiense) and other amphibians also use vernal pools. In addition to these endemic species, vernal pools provide habitat for many other native plants that are largely responsible for vernal pool spring wildflower displays. The inhospitable growing conditions make it difficult for non-native grasses and forbs to flourish, so native species do not have to compete with them for resources. Unfortunately, certain non-native plant species threaten vernal pools, despite their harsh growing conditions.

Livestock grazing has been shown to protect native plant and animal biodiversity in vernal pool ecosystems in part by reducing competition from non-native plant species and reducing overall vegetation cover in the pool basin and edges thus reducing evapotranspiration losses (Marty

2005, 2015). An additional challenge facing vernal pool species is that most historic vernal pools across the state have been lost to urban and agricultural development (Holland 1998).

Hydrology of vernal pool complexes is an essential consideration in their management. Depth, surface area, and duration of pool inundation affect habitat suitability and quality for many vernal pool plant and animal species (Collinge et al. 2013). Vernal pool hydrology is determined by annual rainfall amount and timing and by local topography, with surface flow from the surrounding landscape filling pools (CH2MHILL 2006).

Vernal pools and swales occur throughout the pastures on Travis AFB, with over 900 identified base-wide (Marty unpublished data). Vernal pools on base, some of which were restored in

1999, have been extensively monitored over the last two decades (see BioSystems 1994, Collinge 1999, Gerhardt and Collinge 2003, CH2MHILL 2006, Collinge et al. 2013, ICF

International 2013) in part because they contain federally listed plant and animal species and are a threatened ecosystem.

4.5.2 Special Status Plants and Animals

California tiger salamander

The federally threated California tiger salamander occurs on Travis AFB, breeding in vernal pools and ponds and summering in small mammal burrows or soil cracks in upland grassland

(Ford et al. 2013). The Castle Terrace Preserve and a small seasonal swale on the east side of the base are the only two areas on base where CTS are known to breed (Marty 2022b).

Livestock grazing may help maintain hydrological conditions for completion of CTS’ aquatic phase, estimated to last 70 to 90 days (Marty 2005, 2015); longer vernal pool inundation periods can produce significantly more metamorphosing CTS juveniles (Marty 2022b). Livestock grazing can reduce habitat for predaceous aquatic hexapods (Bobzien and DiDonato 2007). In addition, livestock grazing can improve upland habitat conditions for California ground squirrels

(Otospermophilus beecheyi), whose burrows CTS occupy and help maintain the short grassland that CTS require for travel between upland habitat and breeding ponds (Barry et al. 2015).

Livestock grazing should not be removed from upland areas for more than a year and managing grazing for RDM based on the recommendations of Bartolome et al. (2006) is generally compatible with healthy populations of CTS.

Vernal pool branchiopods

Vernal pools on the main base contain one federally listed branchiopod species: vernal pool fairy shrimp (Branchinecta lynchi; federally threatened). Livestock grazing may help maintain the necessary hydrological conditions for reproduction of this large branchiopod species, which requires several weeks to mature (USFWS 2007a and b). A Sacramento County grazing exclosure study demonstrated that, after 9 years without livestock grazing, vernal pools took up to 2 weeks longer to fill and dried 1-2 weeks earlier on average than comparison grazed pools

(Marty 2015). Cattle reduce grass cover, which in turn reduces evapotranspiration, resulting in longer vernal pool inundation periods. In addition, Marty (2015) suggests that thatch build-up in ungrazed pools increases soil organic matter and consequently soil water-holding capacity; as a result, the surrounding soil holds more water in an ungrazed vernal pool, and less is retained in the vernal pool itself, reducing inundation period. In its most recent 5-year review for vernal pool fairy shrimp, the USFWS states that cessation of grazing is a threat to the species, noting that overgrazing that that increases sedimentation and nutrient inputs to pools is also likely to be a threat; livestock trampling may also crush shrimp cysts (USFWS 2007).

Western Monarch

The widespread decline of the monarch butterfly (Danaus Plexippus) across North America resulted in a decision by the United States Fish and Wildlife Service (USFWS) to list the species as threatened under the Endangered Species Act in December 2024. The decreasing availability of larval host plants (milkweeds, Asclepias spp.) has been implicated as one of the factors responsible for this decline. Additionally, a lack of available nectar resources in habitat along the monarch’s migratory path has also impacted the species (Xerces 2018).

Narrowleaf milkweed (A. fascicularis) occurs in all the grazing pastures on Travis AFB, with patches ranging from less than 10 stems to more than 1,000 stems (Marty 2023). Monarch butterflies have been found nectaring on native and non-native flowers and breeding on milkweed in Travis AFB pastures (Marty 2024a). Cattle grazing is generally compatible with monarch habitat in that it can reduce competition from non-native grasses that outcompete nectar plant species (Xerces 2018). Cattle and sheep tend to avoid eating milkweed due to its toxic properties, but, even if grazed to the end of the season (June), milkweed can regrow and flower for use by monarchs (Marty 2024b).

Poorly timed sheep grazing can negatively impact nectar resources within pollinator habitat if the plant is highly palatable to sheep. This was documented in Pasture 20 on Travis AFB where a 2-acre patch of the important nectar plant hairy vetch (Vicia villosa) was grazed during the flowering period. Within one day, all vetch was removed from the pasture and no nectar resources were available for the remainder of the season (Marty 2024b).

Contra Costa goldfields

An annual forb in the Asteraceae family, Contra Costa goldfields is found primarily in central coastal California and blooms from March through June (CNPS 2024). Potential threats to the species include development, agricultural conversion, hydrological alteration, intensive grazing practices, livestock trampling, and competition from non-native plants (LSA 2012a, USFWS

2013, CNPS 2024).

The USFWS in its most recent 5-year review of CCG explicitly states that “insufficient grazing” and “lack of grazing” present a threat to the species. Cattle preferentially eat grasses, reducing competition with diminutive vernal pools species. Grazing also reduces the amount of thatch in the pools. Less cover of grasses within the pool basin may reduce evapotranspiration losses, resulting in longer vernal pool inundation periods (Marty 2005, 2015). Experiments in Alameda

County demonstrated that CCG were more abundant in seasonally grazed areas than in comparison ungrazed exclosures (USFWS 2013). In addition, the review describes CCG populations in several counties that are increasing with well-managed livestock grazing programs. Heavy grazing, in contrast, is cited as a threat to the species. The USFWS appears to consider moderate grazing an appropriate and even necessary tool for controlling the negative effects of non-native grasses (USFWS 2013). Moderate grazing has been defined as livestock use that removes 50-75% of the forage each year, leaving 500-1,000 pounds per acre of residual dry matter still on the ground immediately prior to fall rains (Barry et al. 2011).

Sheep grazing may be detrimental to CCG populations and other vernal pool plants if grazing occurs after the pools have dried and while vegetation is growing in the basin. Sheep tend to prefer forbs over grasses (Larson et al. 2015) and will graze the vernal pool flowers within the pool basins, leaving upland grasses to dry and form a dense thatch. They also bed down in vernal pool basins and can create bare ground conditions when doing this in high numbers.

On Travis AFB, the largest number of occurrences of CCG occur in Pasture 14 at the Aero Club

Conservation Area. This site had been managed with mowing and had not been grazed prior to

2018. Grazing infrastructure was completed in 2018 that allowed for the site to be grazed by cattle, and a study was initiated to monitor the CCG population over time in grazed and ungrazed areas. The study showed that grazing helped to maintain native species richness and cover and enhanced CCG populations in some years (Marty 2019, 2021, 2022a). A lack of grazing was associated with higher cover of exotic species, increased levels of thatch and increased algal matting.

Alkali milkvetch

An annual forb in the Fabaceae family, alkali milkvetch (Astragalus tener var. tener) is found in central California (LSA 2012b). The species blooms from March through June (CNPS 2024).

Potential threats to alkali milk vetch are development, agricultural conversion, and competition from exotic plants (CNPS 2024). Livestock are unlikely to eat the plant as many Astragalus species are toxic to livestock, including horses and cattle (DiTomaso and Healy 2007, Forero et

al. 2011); the species may possibly be threatened by livestock trampling (CNPS 2024). Cattle and horses typically select grasses over forbs (Larson et al. 2015) and may, therefore, influence the competitive relationship between non-native annual grasses and native forbs in favor of the natives. The USFWS in the vernal pool recovery plan observe that populations of alkali milkvetch in grazed areas are rated as in good or excellent condition, and that livestock grazing may be necessary to reduce competition from non-native plants (USFWS 2005).

San Joaquin spearscale

An annual forb in the Chenopodiaceae family, San Joaquin spearscale, also known as San

Joaquin saltbush (Extriplex joaquiniana), has a range limited to the western side of the Central

Valley and small inner Coast Range valleys. There is minimal information about its ecology

(East CCC HCP/NCCP 2006a). San Joaquin spearscale flowers between April and October.

Extriplex species are relatively tolerant of disturbance but may be intolerant of fire (LSA 2004).

Potential threats to the San Joaquin spearscale include overgrazing, development, intensive agriculture, and competition from exotic plants (CNPS 2024, Little and Gerlach 2009, East CCC

HCP/NCCP 2006), although Little and Gerlach (2009) note that the species has a long-lived seedbank that germinates in response to soil disturbance and that the species can co-exist in grassland dominated by non-native annual plants.

Cattle and horses typically select grasses over forbs (Larson et al. 2015) and may, therefore, influence the competitive relationship between annual grasses and native forbs in favor of the native forbs. A researcher who surveyed San Joaquin spearscale in 5 cattle-grazed sites for 10 years suggests that moderate livestock grazing appears best for San Joaquin spearscale but that occasional rest from grazing is fine (Hopkinson 2017).

Table 5 summarizes possible grazing effects on these species and includes the pastures where the species have been found.

Table 5. Special-Status Species and Grazing Management Considerations.

Species Common Name

/Scientific Name

Grazing Management Considerations Pasture(s)

Amphibians and Reptiles

California tiger salamander

(Ambystoma californiense)

Potentially Beneficial/Timing. Grazing can be beneficial by enhancing aquatic and upland habitat for CTS. Grazing in and around ponds can have positive effects on vegetative cover, nutrient levels, and turbidity. Using grazing to maintain a 0-35% cover of emergent vegetation in ponds supports populations of CTS. A reduction in thatch from tall, dense fields of non‐native grasslands may encourage an expansion of burrowing small mammals (i.e., California ground squirrel and pocket gophers). An expansion of small mammal burrows/California ground squirrel colonies increases potential upland habitat for CTS (Ford et al. 2013).

Pastures

19, 20

Western pond turtle

(Actinemys marmorata)

Exclusion/Timing. Grazing may impact western pond turtle (WPT) upland nest or aestivation sites (between 100 ft and 500 ft from aquatic habitats (Rathbun et al. 2002).

Restricting livestock around aquatic sites may be necessary because they are known to reduce WPT survivorship through trampling of eggs and hatchlings. Short term, light grazing practices during spring, may not significantly reduce suitability of nesting habitat for WPT. Recommend WPT surveys at aquatic sites to determine where possible exclusion buffers should be incorporated.

Pastures

19, 20

Ground Nesting Raptors/Birds

Western burrowing owl

(Athene cunicularia)

Potentially Beneficial. Grazing can be beneficial by enhancing potential habitat for western burrowing owls (CalPIF 2022). A reduction in thatch in tall, dense fields of non‐native grasslands may encourage an expansion of California ground squirrels within the Reserve. Over time, an expansion of small mammal burrows/colonies may

Pastures 1, 6, 7, 14, 16

Species Common Name

/Scientific Name

Grazing Management Considerations Pasture(s) increase the availability of suitable foraging and burrowing habitat for breeding and/or wintering western burrowing owls. Recommend grazing in or near areas where

California ground squirrels currently occur to encourage expansion. Monitor areas to see if western burrowing owls move into area.

Above-Ground Nesting Raptors/Birds

Golden eagle

(Aquila chrysaetos)

(wintering)

Potentially Beneficial. Grazing can be beneficial by enhancing potential foraging habitat for golden eagles. A reduction in thatch from tall, dense fields of non‐native grasslands present throughout the Reserve may encourage an expansion of burrowing small mammals. Over time, an expansion of small mammal burrows/colonies may increase suitable foraging habitat for golden eagles (CalPIF 2022).

Pastures 1, 19, 20

Tricolored blackbird

(Agelaius tricolor)

Exclusion/Timing. Ideal foraging conditions for tricolored blackbirds are created when grazing, mowing, or shallow flood irrigation of cultivated lands keep the vegetation at an optimal height of (<15cm) (Tricolored blackbird working group 2009). Preferred foraging habitats include annual grasslands and cut-grain fields and open marsh borders adjacent or near their colony sites. Grazing may benefit tricolored blackbirds by reducing the height of tall thatch and abundance of non-native invasive plants.

Promoting native vegetation to expand may improve quality of foraging habitat. Avoid grazing in pond (or other nesting) sites during breeding season if tricolored blackbirds are actively nesting and emergent vegetation is not deemed a sufficient barrier to cattle.

Grazing of aquatic habitat during the dry season should be monitored to prevent excessive removal of emergent vegetation.

None

Swainson’s hawk

(Buteo swainsoni)

Potentially Beneficial. Nests strongly associated with riparian vegetation; grasslands provide foraging habitat only: grazing may increase visibility of prey by reducing

Pastures 2, Species Common Name

/Scientific Name

Grazing Management Considerations Pasture(s) cover (Woodbridge 1998); in Central Valley, Swainson’s hawk strongly associated with grazed grasslands (Swolgaard et al. 2008).

Invertebrate Species

Vernal pool fairy shrimp

(Branchinecta lynchi)

Potentially Beneficial. Grazing can be beneficial by reducing grass cover within the basin, which in turn reduces evapotranspiration, resulting in longer vernal pool inundation periods that help maintain the necessary hydrological conditions for reproduction.

Pastures

15, 16, 19, Western Monarch

(Danaus plexippus)

Exclusion/Timing. Grazing can be beneficial by reducing non-native grass cover around milkweed plants and nectar plants. While milkweed can be toxic to livestock, sheep and cattle will graze small patches. Removing grazers by July will allow grazed milkweed to regrow foliage and flower later in the season. This may benefit monarchs by extending the flowering season for the milkweed, allowing monarchs returning to their coast range wintering habitat in late summer/early fall a last opportunity to breed.

All

Pastures

Special Status Plants

Contra Costa goldfields

(Lasthenia conjugens)

Moderate levels of grazing are ideal in maintaining and enhancing populations of CCG.

Cattle grazing reduces competition from grasses and removes thatch that may prevent

CCG from germinating. Additionally, cattle grazing has been shown to maintain inundation periods of vernal pools and hoof action can create small…