Effects Of Feral Rooting On Vegetation Communities & Rare Endemic On , California Structure Of Talk

• Vegetation Monitoring Design – Community – Rare Plants • General Community- level Patterns – Richness, Diversity & Eveness – Structure & Species Composition • Rooting Effects On Vegetation Dynamics • Rooting Effects On Rare Endemic • Generality Of Results Physical Characteristics

• 246 km2 in area (96 mi2) • Complex Topography (highest elevation 745 m) • Complex Geology & Santa Cruz Island Floristics

• 10-12 Communities – 5-6 major ones • 470 Native Species • 157 Non-native Species • 36 Channel Island Endemic Species • 7 Santa Cruz Island Endemic Species Goals

• Vegetation – Evaluate the degree to which feral pig rooting was influencing changes in structure & species composition in the 5 major vegetation communities • Rare Plants – Determine which species were being impacted by feral pig rooting Vegetation Communities

• 5 types – Grassland – Chaparral/Bishop Pine – Oak Woodland – Coastal Scrub – Fennel Vegetation Monitoring Protocol

• Stratified (semi) random design – 100 plots (30 m x 2 m) • Species-based – Cover (100 points) • Point Intercept • Herbaceous layer, shrub layer, tree layer – Density (60 m2) • Belt transect • Shrubs and trees • Bare ground, litter, rooting • Sampling 1991-1995, 1998 Rare Plants Rare Plant Monitoring Target Species

• Berberis pinnata insularis – Presence/Absence – 3 populations • Arabis hoffmannii – Census, height, floral counts – 3 populations • Thysanocarpus conchuliferus – Presence/Absence – 1-11 populations • nesiotica – Density, cover, & floral counts – Height – Vegetation community (cover & height) • Malacothamnus fasciculatus nesioticus – Census, height, floral counts – 3 populations General Patterns For Vegetation Communities Species Diversity

70 15

60 12 50

40 9

S

N2 30 6 Community 20 CS 3 Chap/Pine 10 Fennel Grass 0 0 OW 1991 1992 1993 1994 1995 1991 1992 1993 1994 1995

0.7

0.6

0.5

0.4

G 0.3 Community 0.2 CS Chap/Pine 0.1 Fennel Grass 0.0 OW 1991 1992 1993 1994 1995 Shrub Expansion

100 100

10 Community 10 CS Fennel

Adult Shrub Density Adult(log) Density Shrub

Shrub Seedling Density (log) Seedling Density Shrub Grass OW 1 1 Pine/Chap 1991 1992 1993 1994 1995 1991 1992 1993 1994 1995 Native Grasses & Forbs

Native Herbaceous Species Native Herbaceous Species

40 100.00

30 10.00

20 1.00

Cover (%)Cover Community

Species (%)Species

10 CS 0.10 Chap/Pine Fennel Grass 0 0.01 OW 1991 1992 1993 1994 1995 1991 1992 1993 1994 1995 Alien Grasses & Forbs

Alien Herbaceous Species Alien Herbaceous Species

80 100.00 70

60 10.00 50

40 1.00

30 (%)Cover Community

Species (%)Species

20 CS 0.10 Chap/Pine 10 Fennel Grass 0 0.01 OW 1991 1992 1993 1994 1995 1991 1992 1993 1994 1995 Rooting Effects On Vegetation Communities Magnitude Of Rooting

80

70

60

50

40

Rooting (%) 30

20

10

0 1991 1992 1993 1994 1995 Rooting Frequency & Vegetation Communities

200

150

100

Frequency

50 Condition Unrooted 0 Rooted

CS OW Pine Chap Fennel Grass Vegetation Community Rooting Intensity & Vegetation Communities

80

70

60

50

40

Rooting (%) 30

20

10

0

CS OW Pine Chap Fennel Grass Vegetation Community Analysis Approach

• Disturbance Regime – Intensity (% rooted) – Frequency (cumulative number times) – Interval (years since last rooted) • Multiple Regression – Community Measures • Total Species Richness (S) • Species Diversity (N2) • Evenness (Molinari’s G) – Guilds/Vegetation Structure • Shrub Species Richness, Cover, Density • Shrub Seedling Density • Non-native and Native Forb Cover and Species Richness – Annual & Perennial • Non-native and Native Grass Cover and Species Richness Rooting/Community Measures Correlations

Return Statistic Intensity Frequency Interval

S Positive Positive

N2 Negative

G Negative Rooting/Vegetation Structure Correlations

Guild Intensity Frequency Return

Shrub Species Negative Positive

Shrub Cover Negative Negative Positive

Shrub Seedlings Negative Negative Positive

Native Annual Positive Forb Species Alien Annual Positive Forb Species Alien Annual Positive Forb Cover Alien Grass Positive Cover Ordination of Plots

1.0

ASPECT

SLOPE

-1.0 1.0

ELEVATION INTENSITY

FREQUENCY

-1.0

ENV. VARIABLES

SAMPLES

Chaparral/Pine Coastal Scrub Oak Wooldand Fennel Grassland Ordination of All Species

0.8

rhuint

ceameg lotden stilep ASPECT rhuova artcal

SLOPE eriarb filcal luzsub

adefas pittri erobot galang mimlon miccal brorub atrsem lolmul bacplu pinmur erigra arcins mimfle hapsqu lamaur zigfre achmil stipul gnamic vulmyu dicpul quepar erocic avefat -1.0 marvul avebar 1.0 marmac silgal sonasp quedum hetarb sanarg hypgla bromol latlae amsint eromos ceaarb medpol cenmel claper lupbic brocar brodia cerglo branig bacpil horgen ELEVATION checal stemed foevul INTENSITY galapa

vioped

FREQUENCY

-0.8

SPECIES

Alien Annual Forb Alien Perennial Forb Alien Annual Grass Native Perennial Grass Native Perennial Forb Ferns Shrubs Trees

Native Annual Forb

ENV. VARIABLES Ordination of Rarer Species

0.8 peremo

oxaalb

poaann ASPECT helsco mircal dodcle SLOPE rhapir filari ruburs tricil quetom queagr cenexa disspi ericon astgam lindia agrdie cashol sillac hemfas oenhoo antnut ascfas quechr trigra

symmol trialb poasca epicil michet erifol comdiv frasal lepfra horcal -1.0 gilach galpor lilhum 1.0 arctom adijor phamin delpar jepmal lomutr casaff vencar calcat trimic2 cardra pteaqu polcal vicsat

calalb lacser ELEVATION stabul silmar anaarv INTENSITY conbon chemur eromac chlpom

polare lomcar

FREQUENCY gnalut

-0.8

SPECIES

Alien Annual Forb Alien Perennial Forb Alien Annual Grass Native Perennial Grass Native Perennial Forb Ferns Shrubs Trees

Native Annual Forb

ENV. VARIABLES Summary & Interpretation For Vegetation

• As much as 10% of the island can be rooted in years with high pig density • Most rooting occurs in grassland, fennel and oak woodland communities • High intensity of rooting reduces overall species diversity, but species richness increases in plots with frequent, low intensity rooting • Recruitment and cover of woody species are reduced with increasing intensity of rooting • Increase in species richness is outcome of native and non-native annual forbs replacing woody species • Rarer species potentially reduced by higher intensity and frequency of rooting • Rooting mediates community structure, patch dynamics and probably succession patterns Feral Pig Impacts On Rare Plants

• Thysanocarpus conchuliferus – 11 of 14 known populations found in 1991with individuals present – 3 populations found in 1992 with individuals present (3 populations rooted) – 1 population found in 1993- 1998 with individuals present (2 additional populations rooted) – N=56 in remaining population (1998) – 5 populations rooted by ; remaining ones heavy cover alien grass Feral Pig Impacts On Rare Plants

• Arabis hoffmannii – Centinela Population • Pigs reduced stem density from 32 in 1992 to 19 in 1993. Population rebounded 78-110 stems 1994-98. – Platt’s Harbor Population • Pigs destroyed population in 1995 (N=15 stems) – Albert’s Road Population • Discovered 1995 • No impacts • Stem density 11-81 from 1995-1998 Generality Of Results

• Likely To Be Representative Of Effects In Many Similar Ecosystems With Mediterranean-climate • Mediation Of Shrub Invasion Into Grasslands Has Conservation Importance – Type conversion • Rare Species Impacts!