Direct and indirect effects of global change on species responsiveness,

invasion success and weed performance in dry regions

José M. GrünzweigRobert H. Smith Faculty of Agriculture, Food and

Environment, the Hebrew University of Jerusalem, Israel

2nd International Conference on «Novel and sustainable weed management in arid and semi-arid agro-ecosystems», Santorini,

Greece, 8 September 2009

1. Global change as a complex concept in ecology, agronomy and plant science

2. Responsiveness to global change of plant species in general and weeds in particular

3. Invasive species in natural and agricultural ecosystem under global change

4. Conclusions: Weed success and invasion at different spatial scales in arid and semi-arid regions under future changed conditions

OutlineOutline

1. Global change as a complex concept in ecology, 1. Global change as a complex concept in ecology, agronomy and plant scienceagronomy and plant science

U.S. Global Change Research Act of 1990Public Law 101-606(11/16/90) 104 Stat. 3096-3104

"Global change" means changes in the global environment (including alterations in climate, land productivity, oceans or other water resources, atmospheric chemistry, and ecological systems) that may alter the capacity of the Earth to sustain life.

Climate change

Atmospheric CO2 enrichment

Nitrogen deposition Change in stratospheric ozoneTropospheric ozone pollution...

Change in atmospheric compositionChange in atmospheric composition

Land use change and anthropogenic disturbanceLand use change and anthropogenic disturbance

Alien species invasionAlien species invasion

A. Danin

A. Danin

Barry A. Rice

2. Responsiveness to global change of plant 2. Responsiveness to global change of plant species in general and weeds in particularspecies in general and weeds in particular

• Differential response of species and possible mechanisms underlying those responses

• Potential relevance for agricultural weeds

Modified from Zavaleta et al. 2003 Ecol. Monogr.

Differential impact of global change on plant speciesDifferential impact of global change on plant speciesGlobal change manipulation in a ‘natural’ grassland in California:• Atmospheric CO2 enrichment (C)• Climatic warming (W)• Rain (precipitation) addition (P)• Atmospheric nitrogen deposition (N)

Species

= increase = decrease = inconsistent response0 = no change

Impact of global change on plant species: example from a Impact of global change on plant species: example from a semi-arid community under atmospheric COsemi-arid community under atmospheric CO22 enrichment enrichment

-5

0

5

10

15

20

25

Onobrychis crista-galliP = 0.009

P.f. M.m.C.d.

H.c. B.f. P.p. C.a. P.co. B.a. P.a. D.s. B.l. Bi.d.

A.s.

H.c. M.t.H.s.

S.c.T.c.

R.s.H.u.

R.p.D.g.

P.cr.Br.d.

R.a. S.p.

SpeciesCh

ang

e in

ab

ove

gro

un

d b

iom

ass

(g·m

-2)

440-280

600-280

0

100

200

300

Ab

ove

gro

un

d b

iom

ass

(g m

-2)

280 440 600

CO2 concentration (ppm)

bb a

Grünzweig & Körner. 2001. Oecologia. Grünzweig & Körner. 2001. Oikos

Some growth-determining plant factors that can be altered by elevated CO2

• Photosynthetic rate

• Stomatal conductance

• Respiration rate (differences between different plant parts)

• Partitioning of dry matter (leaf vs. stem, roots or storage organs)

• Leaf duration (leaf senescence)

• Allocation of carbon to symbionts and exudation

0.00.10.20.30.4

280 440 600CO2 concentration (ppm)

LW

Ra Leaf weight ratio (LWRLeaf weight ratio (LWRaa = leaf = leaf

DW / total aboveground DW) DW / total aboveground DW) for for Onobrychis crista-galliOnobrychis crista-galli

28 397 7

Evapotranspiration

Rain

Water leaching

Morgan et al. 2004. Oecologia

Soil moisture

Water saving under atmospheric COWater saving under atmospheric CO22 enrichment as indirect effect enrichment as indirect effect

on plant performance and species compositionon plant performance and species composition

Period during growing season

Onobrychis crista-galli: the largest species and the most mesic legume in the community

Low CO2 High CO2

Seed production at elevated CO2

Onobrychis crista-galliS

eed

pro

du

ctio

n (

no

. m

-2)

CO2 concentration (ppm)

0

400

800

1200

280 440 600

P = 0.010

Parentucellia flaviflora

0

200000

400000

600000

280 440 600

CO2 concentration (ppm)

P = 0.001

A. Danin

P.h.:C.c. = 1:1

P.h.:C.c. = 1:3

Competition between a semi-arid CCompetition between a semi-arid C44 pasture grass and an pasture grass and an

invasive Cinvasive C33 weed under atmospheric CO weed under atmospheric CO22 enrichment enrichment

Cenchrus ciliaris introduced C4 pasture grass in semi-arid subtropical and tropical pastures of northern Australia

Parthenium hysterophorus invasive C3 weed

Potential causes of increased growth and reproduction of P. hysterophorus under elevated CO2:

Plant water savings and accelerated plant development under conditions of rapid soil drying

Ziska. 2003. J. Exp. Bot.

Increase in total biomass (%)

Invasive weeds under past and future atmospheric COInvasive weeds under past and future atmospheric CO22 enrichment enrichment

Potential causes of increased growth under elevated CO2:

Substantial belowground sinks contributing to largely stimulated plant growth→ potential link between invasiveness and CO2

responsiveness

Hemiparasite performance under global changeHemiparasite performance under global change

Phoenix & Press. 2005. Folia Geobot.

Responses of CResponses of C33 and C and C44 species to global change species to global change

Atmospheric CO2 enrichment

Higher sensitivity of C3 vs. C4 photosynthesis to elevated CO2

Stimulation of C4 relative to C3 species by elevated CO2 under warm and dry conditions

Climate change

Global warming: favors C4 plants in general

Timing of global warming:

Warmer winters → stimulation of C3 plants

Warmer and wetter summers → stimulation of C4 plants

Warmer and drier summers → suppression of C4 plants

(unless fire plays a role in the ecology of the site)

3. Species invasiveness in natural and agricultural 3. Species invasiveness in natural and agricultural ecosystems under global changeecosystems under global change

Lectures to be learned from natural ecosystems and potential application to invasive weeds in an agricultural context

Skinner et al. 2000. Weed Sci.

Enhancement of an invasive annual grass under Enhancement of an invasive annual grass under atmospheric COatmospheric CO22 enrichment in the desert enrichment in the desert

Smith et al. 2000. Science

Success of the invasive alien Bromus madritensis spp. rubens in the Mojave Desert FACE experiment

Evans et al. 2001. Ecol. Appl.

Yield losses and costs for weed control (W USA,

Canada): US$ 350-375 million/year

Invasive alien cheatgrass (Bromus tectorum)

Positive feedback loops of alien plant invasionPositive feedback loops of alien plant invasion

Mediterranean islandsMediterranean islands

Human-dominated habitats

Habitat

Modified from Hulme et al. 2008 In: Tokarska-Guzik et al., Backhuys Publishers

Plant invasion on Mediterranean islandsPlant invasion on Mediterranean islands

Ross et al. 2008 Persp. Plant Ecol. Evol. Syst.

Impact of climate and land use on plant invasionsImpact of climate and land use on plant invasions

Oxalis pes-caprae invasion on the island of Crete (Greece)

Barry A. Rice

Agricultural sites colonized by

Oxalis pes-caprae

Initial bulbil biomass

Model output on the effect of disturbance frequency on native and invasive species on the island of Lesbos (Greece)

Quercus ilexQuercus ilex

Quercus cocciferaQuercus coccifera

Juniperus oxycedrusJuniperus oxycedrus

Ailanthusaltissima

Gritti et al. 2006. J. Biogeogr.

Gritti et al. 2006. J. Biogeogr.

Ailanthus altissima (invasive tree)

Amaranthus retroflexus (invasive C4 herb)

Plantago lanceolata (native herb)

Different native trees and shrubs

Model output on the effect of disturbance frequency on native and invasive species on the island of Lesbos (Greece)

Theory of alien invasions can suggest causes for Theory of alien invasions can suggest causes for successful invasive weedssuccessful invasive weeds

Davis. 2000. J. Ecol.

a) Increased resource availability b) Enemy release

Invasive species

Keane & Crawley. 2002Blumenthal. 2005. Science

Combination of a) and b)

4. Conclusions: Weed success and invasion at 4. Conclusions: Weed success and invasion at different spatial scales in arid and semi-arid different spatial scales in arid and semi-arid

regions under future changed conditionsregions under future changed conditions

Ecophysiological topics• Large aboveground or belowground sinks• Efficient carbon allocation and canopy development

Rainfed agriculture• Water waster in a water-saving system• Accelerated growth and development

C4 weeds• Higher water use efficiency• Better adapted to elevated temperatures and heat stress

than C3 plants

HemiparasitesEffects of host water, carbon and nutrient relations

High responsiveness to global changeHigh responsiveness to global change

• Drying → gaps in the vegetation as opportunity for

establishment and integration

• Land use change, fire and disturbance → extensive

opportunity for establishment and integration under increased

resource availability, leading to high propagule pressure

• High propagule pressure → spread

• Warming → competitive advantage (C4) for integration and

spread

• Elevated CO2 → competitive advantage (species with large

seed or belowground sinks) for integration and spread

Plant invasiveness and site conditions prone to invasionPlant invasiveness and site conditions prone to invasion