Western Riverside County Multiple Habitat Conservation Plan Biological Monitoring Program

2016 Engelmann (Quercus engelmannii) Recruitment Survey Report

2 October 2017

2016 Engelmann Oak Recruitment Survey Report

TABLE OF CONTENTS INTRODUCTION ...... 1

GOALS AND OBJECTIVES ...... 1

METHODS ...... 2

PROTOCOL DEVELOPMENT ...... 2

STUDY SITE SELECTION ...... 2

SURVEY METHODS ...... 3

TRAINING ...... 4

DATA ANALYSIS ...... 4

RESULTS ...... 8

DISCUSSION ...... 11

RECOMMENDATIONS ...... 11

ACKNOWLEDGEMENTS ...... 12

LITERATURE CITED ...... 13

LIST OF TABLES Table 1. Engelmann oak abundance. Number observed and percent change by age and type, for plots surveyed in both 2011-2012 and 2015-2016 survey seasons...... 8 Table 2. Engelmann oak population health as observed among adult in plots sampled during two survey seasons...... 9 Table 3. Conserved populations of Engelmann , estimated population size (number of individuals), and presence of juveniles...... 11

LIST OF FIGURES Figure 1. Adult Engelmann oak abundance at the SRP survey site...... 5 Figure 2. Sapling Engelmann oak abundance at the SRP survey site...... 6 Figure 3. Seedling Engelmann oak abundance at the SRP survey site...... 7 Figure 4. Percent defoliation (i.e., “ loss”) of mature Engelmann oak trees...... 9 Figure 5. Growth in basal diameter of Engelmann oak saplings ...... 10

Western Riverside County MSHCP ii Biological Monitoring Program 2016 Engelmann Oak Recruitment Survey Report

NOTE TO READER: This report is an account of survey activities conducted by the Biological Monitoring Program for the Western Riverside County Multiple Species Habitat Conservation Plan (MSHCP). The MSHCP was permitted in June 2004. Reserve assembly is ongoing and is expected to take 20 or more years to complete. The Conservation Area includes lands acquired under the terms of the MSHCP and other lands that have conservation value in the Plan Area (called public or quasi-public lands in the MSHCP). In this report, the term “Conservation Area” refers to these lands as they were understood by the Monitoring Program at the time the surveys were conducted. The Monitoring Program monitors the status and distribution of the 146 species covered by the MSHCP within the Conservation Area to provide information to Permittees, land managers, the public, and the Wildlife Agencies [i.e., the California Department of Fish and Wildlife (CDFW, formerly California Department of Fish and Game) and the U.S. Fish and Wildlife Service]. Monitoring Program activities are guided by defined conservation objectives for each Covered Species, other information needs identified in MSHCP Section 5.3 or elsewhere in the document, and the information needs of the Permittees. A list of the lands where data collection activities were conducted in 2016 is included in Section 7.0 of the Western Riverside County Regional Conservation Authority (RCA) Annual Report to the Wildlife Agencies. The primary author of this report was the 2016 Botany Program Lead, Karyn Drennen. This report should be cited as: Biological Monitoring Program. 2017. Western Riverside County MSHCP Biological Monitoring Program 2016 Engelmann Oak Recruitment Survey Report. Prepared for the Western Riverside County Multiple Species Habitat Conservation Plan. Riverside, CA. Available online: http://wrc-rca.org/about-rca/monitoring/monitoring-surveys/. While we have made every effort to accurately represent our data and results, it should be recognized that data management and analysis are ongoing activities. Any reader wishing to make further use of the information or data provided in this report should contact the Monitoring Program to ensure that they have access to the best available or most current data. Please contact the Monitoring Program Administrator with questions about the information provided in this report. Questions about the MSHCP should be directed to the Executive Director of the RCA. Further information on the MSHCP and the RCA can be found at www.wrc-rca.org. Contact Information: Executive Director Monitoring Program Administrator Western Riverside County Western Riverside County MSHCP Regional Conservation Authority Biological Monitoring Program Riverside Centre Building 4500 Glenwood Drive, Bldg. C 3403 10th Street, Suite 320 Riverside, CA 92501 Riverside, CA 92501 Ph: (951) 248-2552 Ph: (951) 955-9700

Western Riverside County MSHCP iii Biological Monitoring Program 2016 Engelmann Oak Recruitment Survey Report

INTRODUCTION Engelmann oak (Quercus engelmannii) has the smallest distribution of all oak species found in California and occurs from eastern Los Angeles County to northwestern (Scott 1991; Roberts 1995). Riverside County accounts for approximately 6% of the remaining Engelmann oak populations in California (Scott 1991). The largest occurrence of Engelmann oak in western Riverside County occurs at the Santa Rosa Plateau Ecological Reserve (SRP), and stretches along undeveloped areas in a narrow band west through the Tenaja Corridor to the eastern boundary of the San Mateo Canyon Wilderness Area in the Cleveland National Forest (CNF). Additional populations occur at the Santa Margarita Ecological Reserve (SMER) and the Southwestern Riverside County Multi-Species Reserve (MSR), and a few remnant occurrences (ranging between 1 and 15 individuals) elsewhere within the Plan Area. The MSHCP Species Conservation Objective 3 for Engelmann oak states that we are to “maintain recruitment at a minimum of 80 percent of the conserved populations as measured by the presence/absence of seedlings and/or saplings across any consecutive five years” (Dudek & Associates 2003). However, production of seedlings and saplings is often not a limiting factor in the regeneration of oak stands; rather, overgrazing, exotic grass presence, altered fire regimes, and resource competition hinder this process (Muick and Bartolome 1987; Lathrop and Osborne 1990, 1991). Therefore, we can more informatively track whether or not successful regeneration of Engelmann oak populations is occurring by quantifying change in abundance of individual age classes through time, as opposed to using a presence/absence metric that cannot capture replacement of senescing individuals or contraction/expansion of local populations. Our specific goals and objectives in winter of 2015–2016 were as follows: Goals and Objectives 1. Quantify Engelmann oak abundance at SRP, the Tenaja Corridor and the adjacent study area in the Cleveland National Forest. a. Record abundance of Engelmann oaks within sample plots in 3 age classes: seedlings, saplings and adult trees. b. Compare abundance across survey seasons. 2. Assess the health of the adult Engelmann oak population. a. Estimate percent leaf loss for individual adult trees within plots (where 0% indicates a fully foliated ). b. Record branch loss resulting from a snow storm the previous winter (December 31, 2014). c. Record acorn abundance. d. Look for a correlation between amount of branch loss and acorn abundance. e. Record adult trees that appear to be dead. f. Compare health across survey seasons. 3. Determine whether true recruitment is occurring and senescing individuals are being replaced.

Western Riverside County MSHCP 1 Biological Monitoring Program 2016 Engelmann Oak Recruitment Survey Report

a. Record basal diameter and height category (tall or short, where tall is >1.37 m) of previously tagged saplings to determine growth rates. b. Tag and record basal diameter of new saplings. c. Record saplings that have grown into adult trees. d. Record saplings that have died or cannot be relocated. e. Determine rate of replacement (new adults to dead trees). 4. Improve accuracy of plot relocation in future survey seasons. a. Revise and create new plot maps as needed.

METHODS Protocol Development From 2007-2009, the Biological Monitoring Program documented Engelmann oak recruitment using 30 m × 5 m belt transects, (see Western Riverside County MSHCP Biological Monitoring Program Engelmann Oak Recruitment Survey Reports 2007 – 2009 available at http://www.wrc-rca.org/library.asp). While the belt transect survey method provided useful information about factors affecting oak recruitment, the study design and limited resources prohibited the sample size required to capture natural variation in oak abundance across the landscape. In 2010–2011 we implemented an alternative sampling design (i.e., population sub-sampling) that used circular plots randomly distributed within an Engelmann oak vegetation map. This design improved statistical effectiveness by increasing randomness where large Engelmann oak populations occur, while allowing an increased sample size due to a decreased survey time per sampling unit. We began implementing this design in 2010–2011 at 2 sites within the Plan Area, SRP and MSR. Our initial efforts focused on determining an appropriate sample size to capture natural variation in seedling, sapling, and mature oak abundance across the landscape. In the fall and winter of 2011-2012, we added SMER as a third study site, reduced the sample size based on the results of the previous season, and reintroduced covariate data to increase our understanding of Engelmann oak recruitment in conserved populations. In the winter and spring of 2015–2016 we resampled the SRP survey plots using the protocol established in 2011–2012. With a 4-year interval between 2 survey seasons, we began to assess growth and replacement rates across age classes. Study Site Selection We used the 2005 Geographic Information System (GIS) vegetation map of Western Riverside County (CDFG et al. 2005) to delineate a survey area of Engelmann oak habitat within the SRP Ecological Reserve, the Tenaja Corridor, and a portion of the Cleveland National Forest. Based on the Sawyer and Keeler-Wolf definition of a vegetation association (1995), we selected vegetation polygons where Engelmann oak is dominant or co-dominant with coast live oak (), scrub oak (Q. berberidifolia), and/or western sycamore (Platanus racemosa). Using the “spsurvey” package (Kincaid 2009) of the R statistical program v. 2.5.1 (R Development Core Team 2007), we distributed points within this vegetation map following a Generalized Random Tesselation Stratified (GRTS) sampling design. GRTS designs create a spatially balanced distribution of samples that lead to more uniform coverage of patchy landscapes than a truly random sample (Theobald et al. 2007) and allow changes to the sample size without

Western Riverside County MSHCP 2 Biological Monitoring Program 2016 Engelmann Oak Recruitment Survey Report

adversely affecting spatial balance. Each of the random points was buffered 15 meters to create circular survey plots with an area of 707 m2. Overlapping plots were excluded. We distributed survey plots at SMER and MSR independently of the larger population at the SRP. We did not survey the populations at SMER or MSR in 2015-2016. Survey Methods We initially distributed 1000 sampling points at SRP and surveyed 741 plots during the 2010-2011 season. The results of the first survey season determined that a sample size of about 400 plots was sufficient to obtain stable means of oak abundances across the study site (Biological Monitoring Program 2012). In 2011-2012, we decreased the sample size to 398 and reintroduced covariate data collection, including tracking all saplings on plots, and recording their basal diameters and height categories (e.g., short or tall, where tall is ≥1.37 m). Short saplings are more likely to survive to adulthood than seedlings due to having a woody stem and well-developed root system. Tall saplings, with leader stems that reach above the deer-browse line, gain height and girth more rapidly than short saplings, thus progressing more rapidly to the adult stage (Griffin and Muick 1990). We believe that tracking the intermediate sapling stage of oak growth will provide us with the most reliable indicator of successful recruitment from seedling to adulthood. Additionally, we added a plot mapping procedure to increase the accuracy of plot relocation and reduce data error due to slight differences in plot relocation over time. We continued using this methodology during the 2015-2016 surveys. Circular plots were measured by extending four 15-m long ropes from the center point of the plot in the 4 cardinal directions. A 5th, unsecured 15-m long rope was used to check whether any oaks near the edge were in the plot. Surveyors recorded all Engelmann oak and hybrid individuals (seedlings, saplings, and adults) with at least 50% of their basal stem located within the survey plot. Based on Muick and Bartolome (1987), we defined seedlings as individuals with a basal diameter of <1 cm, saplings as individuals with a basal diameter of 1–10 cm, and adults as individuals with a basal diameter ≥10 cm (see also Lathrop and Osborne 1991, Principe 2002). We used size as a surrogate for age because mortality risks and reproductive behavior are often size- dependent (Tyler et al. 2006) and because size can be more accurately recorded than other methods of capturing age. Saplings recorded during the 2011-2012 season were relocated and measured in 2015 and 2016. Large seedlings were measured and tagged if they had grown into saplings. To understand the potential impact on juvenile oak survival, surveyors recorded the type of substrate (e.g., rock, leaf litter, thatch) that dominated the area within a 1 meter radius of individual saplings. Surveyors recorded hybrids between adult Engelmann oak and scrub oak as one of 2 types based on morphological characteristics: either more closely related to Engelmann oak (H1), or more closely related to scrub oak (H2). Predominance of characteristics was considered, such as leaf shape and color, appearance of the bark, and acorns. Because we have observed in previous survey seasons that leaf type can be highly variable in hybrids, even on a single individual, we chose to simplify the classification of questionable individuals based on habit: a hybrid oak with a tall, single trunk was classified as H1, and a hybrid oak with multiple trunks and a smaller, shrub-like habit was classified H2. For seedlings and saplings, surveyors did not differentiate between

Western Riverside County MSHCP 3 Biological Monitoring Program 2016 Engelmann Oak Recruitment Survey Report

hybrid types; instead, they determined if an individual was closer to a pure Engelmann (Pure) or a hybrid (Hybrid). If a surveyor was unable to classify an individual with confidence, the Botany Program Lead revisited the sampling station to make a final determination. To assess the overall condition of the Engelmann oak woodland within the survey area, surveyors estimated the crown density of all adult trees. The surveyors estimated the percent defoliation from a fully foliated tree while standing 90º apart and between 1/2 and 1 tree length from the trunk of the tree (Zarnoch et al. 2004). A fully foliated individual received a rating near 0% while sparsely foliated trees received higher leaf- loss ratings. Surveyors used a photographic guide developed by the Monitoring Program at the beginning of recruitment surveys in 2007, depicting varying percentages of defoliation, to aid in consistent estimates across surveyors and survey seasons. Surveyors averaged their estimates to reach a final value, which was recorded in the appropriate category (0%, 1-10%, 11-20%, 21-40%, 41-60%, 61-80% or 81-100%). Surveyors also examined all Engelmann oak and coast live oak located within the survey plots for signs of insect or pathogen infestation using a photographic guide adapted from materials distributed by the United States Department of Agriculture Forest Service. Specifically, surveyors looked for goldspotted oak borer (Agrilus auroguttatus; GSOB) exit holes, bleeding, cankers, branch loss, and scarring. Training Prior to the start of oak surveys, all field personnel participated in an office-based training. During this training, surveyors received an overview of the Engelmann oak recruitment project to date and studied samples of Quercus engelmannii, Q. agrifolia, Q. berberidifolia, and Q. engelmannii × berberidifolia hybrids. Inexperienced surveyors participated in field-based training with experienced staff and learned to identify mature Engelmann oaks, seedlings and saplings. They were taught plot relocation and data collection procedures. After completing the oak training, observers were able to differentiate between the Engelmann oaks, scrub oaks, Engelmann oak/scrub oak hybrids, and coast live oaks. Additionally, observers were able to accurately relocate survey plots, estimate percent leaf loss of adult oaks, measure basal diameter of juvenile oaks, and record data using Personal Data Assistants (PDAs). Data Analysis We mapped abundance for all Engelmann oaks observed in 2015-2016 using ArcGIS Desktop 10.5 (ESRI, Inc. 1999-2016; Figures 1-3). Count categories were defined by ArcGIS, which uses Jenks Natural Breaks algorithm (ESRI 2017). We adjusted count ranges for saplings and seedlings for clarity and comparison across 2 survey seasons. We calculated basic descriptive statistics and examined changes in Engelmann oak abundance using Microsoft Excel 2013 and Mystat 12.02.00 (Systat Software, Inc. 2007). We ran chi-squared goodness-of-fit tests to test for significant changes in abundance, binning counts into the ranges represented on the abundance maps and testing them as categorical data. We ran chi-squared goodness-of-fit tests to test for significant changes in adult health categories.

Western Riverside County MSHCP 4 Biological Monitoring Program (

(! ( (! (! ( (! !( ( ( ( ( (! ( (! ( (! (! (!(! (! ( ( (! (! ( ( (! (! (! ( (! ( ( !( (! (! (! (! (! !( (! ( !( (! ( ( ( (! (! !( (! (! !( ( ( !((! (! !( (! !( (! (! (! !((! (!(!(! (! (! (! (! ! ( (! ( !( (!( (! (! (! (! ( ( (! (! ( (!(!!((! (! (! ( ! ( !( !( ( ( !( ( (!( (! ( ( (! (!(! !( (! ( ( (!( ^_ !( (! ( (! (!(! (! ( ( ( ( (! (! ( (! (! (! ( ^_!( (! (! !( (! (! ( (!! ( ( !( ( ( ( ! ( ( (! (! ( ! (! ((! ( ! (! ( !( ( ( (! ! ( (! (! (! ( ( (! (! ( ( ^_!( ( (!(! ( (! ( ( ( ( (! ( (! ( (! (! (! ( ( (! (! ( (! ( ( (! (! ( ( ! (! !( (! ((! ( ( (! (! (! ( ( ( ! ( (! (! (! ( (!( (! ( (! (! ( (! ^_ (! (! ( (! (! ( ^_ (!( ( ^_ ( !((! (( (! ( ( ( ( ( (! ( ( (! (! ( ( ^_ ! ( (! !( (!( (! ( ! ( ( (( ( ( ( !( ( ( ^_ ( ( (! (! (! ( !( ( (! (! (!(!^_( (! !( !( !( ( !((! (! ( (! ( (!( (!( (! ( !( ( (! ! (! ! (! ( ( ( ( ( (! !( ^_(! !( (! (! (!^_ (! (! ( (! (! ( !( (! (! ( ^_ ( !( !( (! (!!( ( !( !( (! (!(! (!(! !( (! (! (! (!( (! ( (! !( (! ( (! ( !( !( ( (! !( (! ( ( ( (! ( (! ( (! !( ( ^_!( !( (! !!( !( ((! Western Riverside County

Legend Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AEX, Adult Abundance ^_ New Trees Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community

( 0 Water Bodies Miles (! 1 - 3 County Boundary 0 0.25 0.5 1 1.5 2 km !( 4 - 7 Habitat Model 0 0.5 1 2 3 (! 8 - 12 Existing Conservation Land Date: 17 May 2017 UTM Nad 83 Zone 11 Study Area (! 13 + Contact: Karyn Drennen Existing Conservation Land I MSHCP Biological Monitoring Program Figure 1. Adult Engelmann oak abundance at the SRP survey site. (

( ( ( ( ( ( (! ( ( ( ( (! ( ((! ^_ ( ^_ ( (! ( (! ! ^_ ( (( ( ( ( ( ( ( (! ( ( (! ( ( ^_ ( ( ( (! ( ( ( ^_ ( ( !( ( ( ( ( ( ^_ ( ( ( !( ( ( ( ( ( ( ( ( (! ( ( ( ( ( ( ^_ ( ( (! ( ( ( ( ( (! ( ( (! (! ^_ ( ( ( ( ( ( ( (! ( (! ( (! ( ( ( ( ^_ (! (! ( ( ^_ ( (! ( ( ( ( !( ( ( ( ( ( ( (! ( ( ( ( ( ^_ ( ( ( ( ( ( ( ( ( (! ( (^_( ( ( !( ( ( ! ( ( ( ( (! ( ( (! ( ^_ ( ( ( ( ( (! ( ( ( ( (! (! !(^_ ( ( (! ^_ (( ( ( ( ( !( ( (! ( ^_!( ( ( ^_!(^_ (! ( ( ( ( ( ( ( ( ( (! (!(! ( ^_!(^_ (! (!^_ ( ( (!^_ ( ( ( ( ^_ ( !( ! (! ( ( ( ^_ (! ( ( ( ^_ !( ( ! ( ^_ ( ( ! ^_ ^_!( ( ( ! ( ( ^_ ( ( ( (! ( ^_ ( ( ( (! ^_ ! (! (! ( ( ( ( (! ( ^_ ( ( ( ( ( ^_ ( (! ( ( ( ^_ ( ( ( (!(! (! ( ( ^_ ^_ ! ( (!( (! ( ( (! ^_ ( ( (( ( ( (! ( ( ! ( ( (! ( ( ( ( ( ^_!( ( ( (! ! (!(! ( !( ( ( ( ^_(! ^_ ( ( ( ( ( ( ( ( ( ( ( ! (!( ( ( ( ^_ ^_ ^_(!^_(! ( ( (!! (! ( ( (! ( ^_ ( !( ( !( ( (! ^_ ( ( (! ( ( ^_ ( ( (! (! ( !( ( ( (!(!^_ (! (! (! !( (! ( ^_(! ( ( ( ( ( ^_(! ( ( (! ( ^_!( ^_!( ( (! ( ^_!( ( ^_( (! ( (! !( ( ( ( ( ( (!( !( (! ! ^_^_(!(! ^_^_!(( (! (!!( Western Riverside County

Legend Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AEX, Sapling Abundance ^_ New Saplings Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community ( 0 Water Bodies Miles (! 1 - 3 County Boundary 0 0.25 0.5 1 1.5 2 km !( 4 - 7 Habitat Model 0 0.5 1 2 3 (! 8 - 12 Existing Conservation Land Date: 17 May 2017 UTM Nad 83 Zone 11 Study Area (! 13 + Contact: Karyn Drennen Existing Conservation Land I MSHCP Biological Monitoring Program Figure 2. Sapling Engelmann oak abundance at the SRP survey site. (

( ( ( ( ( ( ( ( ( ( ( ( !( !( ( (! (( (! ( ( !( ( ( ( ( ( ( ( ( ( !( ( (! ( ( ( (! ( ( ( ( ( ( !( ( ( ( ( ( ( ( ( ( (! ( ( ( ( ( !( ( ( ( (! ( ( ( ( ( (! ( ( (! ( ( ( (! ( ( ( (! ( ( ( ! ( ( (!( ( ( ( ( (! (! ( ( ( (! ( ( ( ( ( (!( ( ( (! ( ( ( ( (! ( ( ( ( ( ( (! ( ( ( ( ( ( ( (!( ( ( (! ( (! ( ( ( ( (! (! ( ( (! ( ! ( ( ( (! (! ( ( ( ((! (( (! ( ( ( (! (! ( (! ( (! ( ( ( (! !( ( (! ( ( !( (! ( ( ( ( ( ( ( ( (! (! ( (! (! ( ( ( ( (! ( ( ( ( ( (! (! ( ( (! ( !( (! ( ( ( ( ( (! (! !( !( ( ( ( ( (! ( ( ( !( (( (! ( (! ( ( !(( ( ( ( ( ( ( ( !( (! ( ( ( ( ( (! !((! ( (! ( !( ( ( (! ( ( ( (! ( ( (( ( ( ( ( ! ( ( (! ( ( ( !( !( (! ( ( !(( ( (! ( ( (! (! (! ( ( ( ( ( ( ( ( ( (! ( (! (!( (! ( ( !( !( (! ( ( ( (! ( ( !(!( ( (! ( ( ( (! !( ( ( (! (! (!( ( ( ( (! ( (! (! (! ( ( !( ( ( ( ( ( (! ( ( ( ( (! (! ( !( !( !( ( ( (! ( (! (! ( ( ( ( ( (!( ! !(( ( ( (! ( (! ( (! Western Riverside County

Legend Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AEX, Seedling Abundance Water Bodies Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community ( 0 County Boundary Miles (! 1 - 10 Habitat Model 0 0.25 0.5 1 1.5 2 km !( 11 - 100 Existing Conservation Land 0 0.5 1 2 3 (! 101 - 300 Date: 17 May 2017 UTM Nad 83 Zone 11 Study Area (! over 300 Contact: Karyn Drennen Existing Conservation Land I MSHCP Biological Monitoring Program Figure 3. Seedling Engelmann oak abundance at the SRP survey site. 2016 Engelmann Oak Recruitment Survey Report

We used Kolmogorov–Smirnov tests to test for significant associations between continuous and categorical data (i.e., sapling size and sapling survival) and we used paired t-tests to test for significant growth in sapling basal diameter. We decided that paired t-tests for sapling growth were appropriate because although data were not normally distributed (SW = 0.9, p < 0.001), we had a large sample size (n = 278), and the distribution curves were similar.

RESULTS Between 10 November 2015 and 10 May 2016, we surveyed 385 plots at the Santa Rosa Plateau, the Tenaja Corridor, and a portion of the Cleveland National Forest. During 78 survey days (226 surveyor days), we completed an average of 3.6 plots per team per day, with a range of 2–18 plots. Abundance We mapped data for numbers of adult Engelmann oaks, saplings, and seedlings observed on all plots that were surveyed during the 2015–2016 survey season (Figures 1- 3). We calculated a mean abundance of 1.88 adult trees per plot (SE = 0.14), 1.02 saplings per plot (SE = 0.16), and 4.83 seedlings per plot (SE = 1.8). We ran chi-squared tests to check for significant changes in the distribution of oaks in plots that were surveyed during both survey seasons (Table 1). We found a slight increase in the mean abundance of pure adult Engelmann oaks (5%, p = 0.94), a statistically significant increase in saplings (26%, p = 0.04), and a statistically significant decrease in seedlings (-49%, p < 0.01) between sampling years.

Table 1. Engelmann oak abundance. Number observed and percent change by age and type, for plots surveyed in both 2011-2012 and 2015-2016 survey seasons (n = 381). Age/Type class 2011-2012 2015-2016 % Δ χ2 a df p Adults Pure 548 572 4.4 0.22 4 0.99 Hybrid 139 146 5.0 0.46 3 0.93 Total 687 718 4.5 0.79 4 0.94 Saplings Pure 285 361 26.7 7.67 4 0.11 Hybrid 24 29 20.8 0 1 1 Total 309 390 26.2 9.88 4 0.04 Seedlings Total 3587 1840 -48.7 111.2 3 < 0.01 a Chi-squared (χ2) values calculated using frequencies within count categories illustrated on abundance maps. Population Health Defoliation (i.e., leaf loss) increased in the 2015-2016 season for both pure and hybrid adult trees (Figure 4). The median defoliation class rose from 11-20% to 21-40% and the mode jumped 2 classes, from 1-10% to 21-40%. Results were consistent for hybrid trees, pure trees and all trees combined. The percentage of “healthy” trees (less than 40% defoliation) declined from 90% to 77% (Table 2). Trees that were considered “stressed” (greater than 40% defoliation) more than doubled, increasing from 10% to

Western Riverside County MSHCP 8 Biological Monitoring Program 2016 Engelmann Oak Recruitment Survey Report

21% of trees observed. Trees that appeared to be dormant or dead (100% defoliated) increased from less than 1% to about 2%. Changes in the health status of adult trees were statistically significant (p < 0.01) across the 381 plots that had been sampled in 2011- 2012 and were resampled in 2015-2016 (Table 2).

350

300 2011 - 2012 2015 - 2016

250

200

150 Count of Trees 100

50

0 0% 1-10% 11-20% 21-40% 41-60% 61-80% 81-100%

Figure 4. Percent defoliation (i.e., “leaf loss”) of mature Engelmann oak trees at the SRP, Tenaja Corridor and CNF survey sites, where 0% represents a fully foliated tree.

Table 2. Engelmann oak population health as observed among adult trees in plots sampled during two survey seasons. Chi-squared (χ2) values calculated across health categories. 2011-2012 2015-2016 Health Status of Trees n % n % χ2 df p Healthy 608 90 519 77 Stressed 65 9.6 143 21 Dead/ Dormant 2 < 1 13 1.9 Total 675 675 167.1 2 < 0.01

Branch Loss and Acorn Abundance We began quantifying branch loss by counting and size-classing freshly broken branches observed on the ground beneath trees and corresponding scars on trees. We were interested in finding out if the damage caused by a snowstorm the previous December could be correlated with the number of acorns produced by damaged trees. However, regardless of branch loss, most trees had no acorns at all, and those that did had very few. Due to the considerable time investment of this effort and insufficient data to detect any associations, we discontinued branch loss and acorn abundance measurements early in the survey season.

Western Riverside County MSHCP 9 Biological Monitoring Program 2016 Engelmann Oak Recruitment Survey Report

Saplings We resurveyed 309 saplings that were tagged and measured in 2011-2012. Of these baseline saplings, 31 could not be re-located or appeared to be dead. We compared the growth rates of the remaining 278 saplings across the 2 survey seasons by first testing the data for normality (SW = 0.9, p < 0.001) and then running a paired t-test. The mean growth of sapling basal diameter was 1.16 cm (CI = 0.99, 1.33; p < 0.01) and the range of sapling growth was 8.8 cm to - 6.1 cm (Figure 5). Negative growth is attributed to secondary stems taking over when primary stems died. Survival of saplings was significantly higher for individuals with larger basal diameters (KS = 0.408, p < 0.01) and for individuals in the “tall” height class (χ2 = 7.87, p < 0.01).

Figure 5. Growth in basal diameter of Engelmann oak saplings between 2 survey seasons. Individuals classified as saplings in 2011-2012 that had grown into adults in 2015-2016 (basal diameter > 9.9 cm) are included both seasons. Stars indicate outliers.

Recruitment and replacement We tagged and measured 129 new saplings in 2015-2016, 118 of which had grown from seedlings and 11 that were newly mapped due to plot refinement. New saplings that had graduated from seedling status had a mean basal diameter of 1.58 mm (SE = 0.06) and 91% were in the “short” height class. We calculated a rate of 1 new sapling for every 30 seedlings observed in 2011-2012 and a replacement rate of 3.8 new saplings for each of the 31 baseline saplings that died or could not be re-located during 2015-2016 surveys.

Western Riverside County MSHCP 10 Biological Monitoring Program 2016 Engelmann Oak Recruitment Survey Report

Of the saplings measured in 2011-2012, sixteen had basal diameters measuring greater than 10 cm in 2015-2016, putting them into the adult age class. All of those individuals were categorized in the “tall” height class. We calculated a rate of 1 new adult for every 19 saplings observed in 2011-2012. Eleven adult trees that were alive in 2011- 2012 appeared to be dead in 2015-2016. We calculated a replacement rate of 1.5 new adult trees for each tree that died.

DISCUSSION Species Objective 3 for Engelmann oak states that we are to “maintain recruitment at a minimum of 80 percent of the conserved populations as measured by the presence/absence of seedlings and/or saplings across any consecutive five years” (Dudek & Associates 2003). We have confirmed 10 geographically delineated populations of Engelmann oaks across the Plan Area, with the vast majority (approx. 96%) occurring in the SRP/Tenaja Corridor/CNF areas (Table 3). Weighting the populations by size, we have met Objective 3, confirming recruitment with full replacement of senescing individuals at 96% of conserved populations.

Table 3. Conserved populations of Engelmann oaks, estimated population size (number of individuals), and presence of juveniles. Population location Pop. Sizea % Recruitment* Agua Tibia Mountains 12 0.06 unknown Estelle Mountain 1 < 0.01 unknown Multiple Species Reserve (MSR) 52 0.28 yes Potrero 8 0.04 unknown San Mateo / Santa Ana Mtns 96 0.52 yes Santa Margarita (SMER) 630 3.54 yes Santa Rosa Plateau (SRP) yes Southeast Santa Ana Mtns (CNF) 17,800 95.7 yes Tenaja Corridor yes Wilson Valley 8 0.04 unknown Totals 18,607 100 6 of 10 a Populations of sampled locations were extrapolated from survey data across mapped suitable habitat, otherwise complete counts are reported. *Juveniles observed at population site within the past 5 years.

Recommendations Recruitment Objective Defining conserved populations of Engelmann oaks by location, irrespective of size, and documenting the presence of seedlings and/or saplings at 80% (8 out of 10) of these locations tells us very little about the conservation of Engelmann oak populations in the Plan Area. In order to meet the intended objective of maintaining 80% recruitment and to ensure the conservation of Engelmann oaks in Western Riverside County, we recommend interpreting this objective to mean that we will maintain, through recruitment, at least 80% of the baseline population of adult Engelmann oaks across the Plan Area. We recommend using results from 2010 through 2012 surveys for our baseline

Western Riverside County MSHCP 11 Biological Monitoring Program 2016 Engelmann Oak Recruitment Survey Report

population estimates. We expect that successful recruitment will primarily occur at the 3 largest population locations: SRP and vicinity, MSR, and SMER. Hybrid Engelmann oaks We detect and record hybridization with scrub oak by examining characteristics of , acorns, bark and general habit. Characteristics can vary considerably, even on a single individual, making determination of hybridization difficult in the absence of genetic testing. This difficulty is more pronounced in immature oaks. For this reason, as of this report, we are no longer recording whether or not seedlings are hybridized, and we have limited classes of saplings to denote either hybrid or pure species. We have also simplified the classing of hybrid adult Engelmann oaks (i.e., H1, H2) based primarily on single-stemmed versus multi-stemmed habit. Data collected during the 2 survey seasons examined here includes approximately 20% hybrid adults and 7-8% hybrid saplings. Results were not significant for hybrid oak data tested separately so we reported the results of both type classes combined throughout most of this report. Additional data collected over several survey seasons may eventually allow us to detect differences in recruitment rates between pure Engelmann oaks and hybrids. We recommend, after sufficient data has been collected, analyzing this data and attempting to answer the questions of whether Quercus engelmannii is evolving via hybridization, or will continue to have a stable, hybridized subset of the population occurring at ecotones between oak woodlands and chaparral vegetation alliances. If data continues to marginalize the significance of Quercus engelmanni x Q. berberidifolia hybrids, we should reassess the value of continuing this part of our survey effort. Additional studies In addition to basal diameter and height class, we have been recording covariate data describing the immediate environment of saplings surveyed. After we have collected sufficient data, we will endeavor to use a mixed model to identify habitat features important to sapling growth and survival. Our vegetation model was created by selecting polygons from 8 vegetation alliances where Engelmann oak is dominant or co-dominant. We recommend, after sufficient data has been collected, examining changes in abundance and recruitment patterns within different vegetation alliances, which may help us better understand the ecology of Engelmann oaks. We expect to continue second-season recruitment surveys at SMER and MSR in the winter of 2017-2018. These populations should be analyzed both independently and combined with the SRP population. Additionally, the scattered remnant populations that are too small for meaningful statistical analysis should be monitored for presence/absence of seedlings and saplings.

ACKNOWLEDGEMENTS We thank the land managers in the MSHCP Plan Area, who in the interest of conservation and stewardship facilitate Monitoring Program activities on the lands for which they are responsible. Funding for the Biological Monitoring Program is provided

Western Riverside County MSHCP 12 Biological Monitoring Program 2016 Engelmann Oak Recruitment Survey Report

by the Western Riverside Regional Conservation Authority and the California Department of Fish and Wildlife. Biological Monitoring Program staff who conducted surveys in 2015-2016 were: Karyn Drennen (Botany Program Lead), Jessica Burton, Tara Graham, Cristina Juran, Michelle Mariscal, Lynn Miller, Paulette Morales (Volunteer), Esperanza Sandoval, Ana Sawyer, and David Tafoya.

LITERATURE CITED Biological Monitoring Program. 2012. Western Riverside County MSHCP Biological Monitoring Program Engelmann Oak Recruitment Survey Report. Prepared for the Western Riverside County Multiple Species Habitat Conservation Plan. Riverside, CA. Available online: http://wrc-rca.org/about- rca/monitoring/monitoring-surveys/. [CDFG et al.] California Department of Fish and Game; Aerial Information Systems, Inc.; California Native Society. 2005. Vegetation - Western Riverside Co. [ds170]. Publication Date: 2005-07-31. Online: http://bios.dfg.ca.gov/. Dudek & Associates. 2003. Western Riverside County Multiple Species Habitat Conservation Plan (MSHCP). Final MSHCP, Volumes I and II. Prepared for County of Riverside Transportation and Lands Management Agency. Prepared by Dudek & Associates, Inc. Approved June 17, 2003. [ESRI] Environmental Systems Research Institute. 2017. ArcGIS Pro, Data Classification Methods. Available online at: http://pro.arcgis.com/en/pro- app/help/mapping/symbols-and-styles/data-classification-methods.htm.

Griffin JR, Muick PC. 1990. California Native Oaks: Past and Present. Fremontia 18:4- 10. Kincaid TM, Olsen AR. 2009. spsurvey: Spatial Survey Design and Analysis. R package version 2.3. Available online at: http://www.epa.gov/nheerl/arm/. Lathrop EW, Osborne CD. 1990. From acorn to tree: ecology of the Engelmann oak. Fremontia 18:30-35. Lathrop EW, Osborne CD. 1991. Influence of fire on oak seedlings and saplings in southern oak woodland on the Santa Rosa Plateau Preserve, Riverside County, California. USDA Forest Service General Technical Report, PSW-126:366-370. Muick P, Bartoleme J. 1987. Factors associated with oak regeneration in California. USDA Forest Service General Technical Report, PSW-100:86-91. [NOAA] National Oceanic and Atmospheric Administration, National Centers for Environmental Information. Climate Data Online [interactive data query system]. Annual precipitation for Station USW00053151, FALLBROOK 5 NE, CA US. 2009 - 2015. Available online at https://www.ncdc.noaa.gov/cdo-web/search. Accessed 02/07/2017.

Western Riverside County MSHCP 13 Biological Monitoring Program 2016 Engelmann Oak Recruitment Survey Report

Principe Z. 2002. Factors affecting Engelmann oak (Quercus engelmannii) regeneration [MS Thesis]. San Diego (CA): San Diego State University. R Development Core Team. 2007. R: A language and environment for statistical computing [software]. R Foundation for Statistical Computing, Vienna, Austria. Available online at: http://www.R-project.org. Roberts F. 1995. Illustrated Guide to the Oaks of the Southern California Floristic Province: the Oaks of Coastal Southern California and Northwestern Baja California, Mexico. Encinitas (CA): F.W. Roberts Publications. Sawyer JO, Keeler-Wolf T. 1995. A Manual of California Vegetation. Sacramento (CA): California Native Plant Society. Scott TA. 1991. The distribution of Engelmann oak (Quercus engelmannii) in California. In Standiford RB, tech coord. Proceedings of the symposium on oak woodlands and hardwood rangeland management; October 31 - November 2, 1990; Davis, California. Berkeley, CA; USDA Forest Service Gen. Tech. Rep. PSW-GTR-126, pp. 351-359. Theobold DM, Stevens DL, White D, Urquhart NS, Olsen AR, Norman JB. 2007. Using GIS to generate spatially balanced random survey designs for natural resource applications. Environ Manage 40:134-146. Tyler CM, Kuhn B, Davis FW. 2006. Demography and recruitment limitations of three oak species in California. Q Rev Biol 81(2):127. Zarnoch SJ, Bechtold WA, Stoke KW. 2004. Using crown condition variables as indicators of forest health. Can J Forest Res 34:1057-1070.

Western Riverside County MSHCP 14 Biological Monitoring Program