What controls plant species diversity during long-term ecosystem development?

Etienne LalibertéSchool of Plant BiologyThe University of Western Australia

Workshop: “Plant species coexistence in young vs. old soils: same old story?”Agriculture North Lecture Theatre, G.033Perth, AustraliaFebruary 20, 2012

Funding

• School of Plant Biology (40%)

• Pro Vice-Chancellor (Research) (40%)

• Faculty Natural & Agricultural Sciences (20%)

Ancient soils, high plant diversity

Source: http://katerva.org

Yasuní, Ecuador>1,100 tree species in 25-ha plot

weathered silty clay soils

Kwongan shrublands, SWA>70 species in 10x10-m plot

little dominancehighly weathered sandy soils

Valencia et al (2004) J Ecol Lamont et al (1977) Nature

Young soils, lower plant diversity?

Vermont, USAunder ice 18,000 years ago

New Zealandgeologically active: uplift, landslides

Long-term soil chronosequences

Figure taken from Peltzer et al (2010) Ecol Monogr

Soil age

Jurien Bay dune sequence

Jurien Bay dune sequence

Laliberté et al. (2012) J Ecol

Holocene dunes(<7 ka)

Pleistocene dunes(>120 ka)

Jurien Bay

Stage 1: mobile Quindalup(very young, 0-50 years?)

Stage 2: Quindalup(young, 100s-1000+ years?)

Stage 3: Quindalup(medium, <7000 years?)

Stage 4: Spearwood(old, >120,000 years)

Stage 5: Bassendean(oldest, >2,000,000 years)

Graham Zemunik, PhD student• Plant-nutrient acquisition strategies• Vegetation surveys

Plant species richness increases with soil age

All vascular plantsobserved species richness

Plant species richness increases with soil age

All vascular plantsobserved species richness

All vascular plantsrarefied species richness

Woody plant species richness

Woody plants (trees and shrubs)observed species richness

Woody plants (trees and shrubs)rarefied species richness

Soil age

Soil N:P

ratio

Nutrient

availability

+ +/-

-

Soil pH

Soil age

Soil N:P

ratio

Nutrient

availability

+ +/-

-

Soil pH

Soil age

Soil N:P

ratio

Nutrient

availability

+ +/-

-

Soil pH

Soil age

Soil N:P

ratio

Nutrient

availability

Productivity

+ +/-

+

-

Soil pH

Plant

species

richness

Soil age

Soil N:P

ratio

Nutrient

availability

Productivity

+ +/-

+

+/-

-

Soil pH

Multiple limiting resources =higher plant species richness?

(Resource-ratio model)

N/P co-limitation

Multiple resource limitation and diversity

Harpole & Tilman (2007) Nature

no single limiting resource

N = + nitrogenP = + phosphorusC = + cationsH = + water

Multiple resource limitation and diversity

Harpole & Tilman (2007) Nature

High diversity under strong P limitation

N limitation

Strong PlimitationCo-limitation P limitation

Laliberté et al. (2012) J Ecol

Co-limitation

Plant

species

richness

Soil age

Soil N:P

ratio

Nutrient

availability

Productivity

+ +/-

+

-

Soil pH

+/-

Plant

species

richness

Soil age

Soil N:P

ratio

Nutrient

availability

Productivity

+ +/-

+

+/-

-

Soil pH

+/-

Humped-back model,dynamic equilibrium model

Low diversity at high productivity, but...

High diversity at low productivityunder P limitation

Low diversity atlow productivity under N limitation

Plant

species

richness

Soil age

Soil N:P

ratio

Nutrient

availability

Productivity

+ +/-

+

+/-

-

Soil pH

+/-

?

Plant

species

richness

Soil age

Soil N:P

ratio

Nutrient

availability

Productivity

+ +/-

+

+/-

-

Soil pH

+/-

?

+/-Species

pool size

+

-?

“species pool” hypothesis

10 species lost per unit increase in pH

• intolerance to high pH / buffering capacity (or Ca toxicity?)• reflects evolutionary history (calcareous soils are rare)• does not invoke local species interactions, only physiological explanations

Carbonate dunes(Quindalup, stage 2: 100s-1000 years?)

pH > 8

... or does P act as a filter?

• P toxicity, again reflecting evolutionary history?• perhaps, but not as convincing as pH...

Plant

species

richness

Soil age

Soil N:P

ratio

Nutrient

availability

Productivity

+ +/-

+

+/-

-

Soil pH

+/-

?

+/-Species

pool size

+

-?

probably

Conclusions• High diversity under strong P

limitation

• Low diversity at high productivity

• ... low/high diversity at low productivity (N- vs. P-limited)

• Size of species pools important

• pH strongly filters species pools

• No single explanation for species coexistence

Acknowledgements

HansLambers (UWA)

• collaborator

Graham Zemunik (UWA)• vegetation surveys

Thomas Costes (France)• nutrient limitation bioassay

Benjamin Turner(STRI)• soil analyses

Stuart Pearse (UWA)• nutrient limitation bioassay

for their cooperation

Patrick Hayes (UWA)• vegetation surveys