A contrast of direct and indirect nurse-plant effects on annual plant and seedbank dynamics in two Californian Deserts

Filazzola, Alessandro

1st Progress report

Nurse Plants

Chapter

Title Purpose Status

1 The relative frequency and importance of facilitation mechanisms in nurse plants

Identify current literature on nurse-plant mechanisms

Data collection complete, write-up pending

2 Nurse plants as seed magnets: meta analysis

Summarized literature on seed trapping by nurses

Papers collected, extract data and write up

3 Regional contrast of plant and seedbank by nurses

Compare nurse effect on seedbanks and annual community

Two surveys complete, transient seedbank collected

4 Initial community density approach

Determine density dependence on annual communities under shrub

Upcoming field season

5 Importance of nurse plants as seed traps

Do nurse-plants function as seed traps and is there a cost of granivory

On-going

Nurse-plant mechanismsHypothesis: There is a gap in the

scientific literature regarding seed-trapping of nurse plants

Expect nurse plants and pollinator studies to be understudied

The Mojave Desert is an understudied regionC1

Nurse-plant Studies

Web of Knowledge: “nurse*” + “plant” = ~700 articlesC1

C1

Subs

trate

Seed

Tra

p

Pollin

ator

Moistur

e

Reduc

ed st

ress

Anti-h

erbivo

re

Evolut

ion

Spat

ial

0

20

40

60

80

100

120N

um

ber

of

Stu

die

s

Meta-mechanisms

C1

Seed-trapping metaConduct meta-analysis on ~30

papers

Hypothesis: nurse plants function as seed traps by increasing seed arrival

Papers are already found, data still needs to be extracted

C2

Regional contrast of nurse plants

Hypothesis: Nurse plants increase seed arrival and facilitate annual community production

Determine study sites◦ Northern Mojave Ridgecrest (NMR)◦ Mojave National Preserve (MJP * 5)◦ Panoche Hills Management Area (PAN * 3)

Vegetation sampling◦ Measure shrub◦ Quadrat sampling (diversity, abundance, cover)◦ Soil Cores

C3

C3

Panoche

Mojave

Grand Mean

Mean calculated Rii with standard error between 12-15 shrub/open pairs

C3

Census 1

Census 2

Grand Mean

Mean calculated Rii with standard error between 12-15 shrub/open pairs

C3

Mojave

Panoche

Grand Mean

Mean calculated Rii with standard error between 12-15 shrub/open pairs

Upcoming surveysConduct two additional surveys

(C3 - Peak biomass and C4 – just prior to recession)

Identify environmental gradient

Soil cores for transient seed bank

C3

ICD: Estimating Density Dependence

H1: Higher seed density under shrub results in greater competition between seedlings

Determine cost of nurse-association from competition

Competition greater under shrubC4

Density dependence experiment

Shrub

Open

¼ x ½ x 1 x 2 x

¼ x ½ x 1 x 2 xC4

0.25X 0.5X 1X 2X0

10

20

30

40

50

60

70

80

Shrub

Open

Density

# G

erm

ina

te P

lan

ts

Nurse effects on seedbankH1: Higher seed densities present

under shrubs than in open

H2: Increased seed rain results in higher granivory rates.

Determine cost of nurse-association from granivory

C5

Modified Community

CShrub

Open

S 0 A

C S 0 A

C5

C5

Granviory experiment

Mammal/BirdExclusion

InsectExclusion

Control -No Exclusion

Control +Full Exclusion

C5

No Mammal No Ant Control - Control +0

10

20

30

40

50

60

70

80

90

ShrubOpen

Seed

s R

em

ain

ing

C5

Chapter Title Timeline

1 The relative frequency and importance of facilitation mechanisms in nurse plants

Write up – end of year

2 Nurse plants as seed magnets: meta analysis

Extract data – end of year

3 Regional contrast of plant and seedbank by nurses

April 15-17 (C3), May 1-5 (C4), collect transient

4 ICD April 18-26 at Mojave/Panoche

5 Importance of nurse plants as seed traps

Collect cups (May 18), set up granivory exclusions (April 26-30), Collect exclusions (May 20)

Thank you!