long-term ecosystem development and plant diversity

Long-term ecosystem development and belowground controls over

terrestrial plant diversity

Etienne LalibertéSchool of Plant Biology, UWAENVT3363 Ecological ProcessesSept 11, 2012

Soil abiotic

properties

Soil biotic

properties

Climate Parent material Topography TimeOrganisms

Terrestrial plant

diversity

Soils

Ecosystem

processes

Community

processes

Cowles (1899) Botanical Gazette

Vegetation succession on Lake Michigan dunes

Classical vegetation succession model

Johnson & Miyanishi (2008) Ecology Letters

‘Climax’

Odum (1969) The strategy of ecosystem development. Science 164:262-270

Eugene P. Odum(1913-2002)

Hawaiian 4.1 million-year island sequence

Crews et al. (1995) Ecology

JurienBay

Perth

Jurien Bay >2-million-year dune chronosequence

0-7 ky

120-500 ky

>2000 ky

Wardle et al (2004) Science

Maximum standing biomass (‘climax’) does not persist in the in the absence of major disturbances:

• landslide• glaciation• volcanic eruption

Ecosystem decline or retrogression

Wardle et al (2004) Science

Long-term soil chronosequences

Peltzer et al (2010) Ecol Monogr

Soil age

Build-up (progressive) phase Maximal phase Decline (retrogressive) phase

Soil age

Total N

Total P

10 mg kg-1

What causes ecosystem decline?

Pedogenesis – Jurien Bay dunes

A

C

Very young dune

(10’s—100’s years)

Ecosystem progression

Very low NHigh P

Pedogenesis – Jurien Bay dunes

A

C

A

C

Very young dune

(10’s—100’s years)Young dune

(~1000’s years)

Ecosystem progression

Very low NHigh P

Highest NHigh PPeak fertility/productivity

Pedogenesis – Jurien Bay dunes

A

C

A

C

Ae

B1E

A

B2

Very young dune

(10’s—100’s years)Young dune

(~1000’s years)

Old dune

(~500,000 years)

Ecosystem progression

Ecosystem retrogression

Very low NHigh P

Highest NHigh PPeak fertility/productivity

low Nlow P

Pedogenesis – Jurien Bay dunes

A

C

A

C

Ae

B1E

A

B2

Ea

E

O

A

Very young dune

(10’s—100’s years)Young dune

(~1000’s years)

Old dune

(~500,000 years)

Very old dune

(>2,000,000 years)

Ecosystem progression

Ecosystem retrogression

Very low NHigh P

Highest NHigh PPeak fertility/productivity

low Nvery low P

low Nextremely low P‘terminal state’

Implications for AustraliaP

rod

uct

ivit

y

Soil age

Most ecologists work here

Most of Australian terrestrial ecosystems

are here

Mt Michaud, Lesueur National Park

Plant strategies

Soil ‘available’ P Leaf P concentration

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 dominancestrongly leached sandy soils

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

Plant diversity along soil chronosequences

Laliberté et al (in preparation)

Graham Zemunik

Nutrient

availability and

stoichiometry

Time

Pedogenic stage

Plant

diversity

resource-ratio

model, productivity-

diversity (+/-)

Nutrient availability and stoichiometry

‘Humped-back’ model

• Low diversity at high fertility

• Low diversity at very low fertility

• Highest diversity at intermediate fertility

Grime (1973) Nature

Jurien Bay

Fertility increases to a peak around 1000’s years and then declines in older soils

High diversity at low productivity in old soils

Low diversity atlow productivity in young soils

Low diversity at high productivity

Multiple resource limitation and diversity

Harpole & Tilman (2007) Nature

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

Nutrient

availability and

stoichiometry

Time

Pedogenic stage

Plant

diversity

resource-ratio

model, productivity-

diversity (+/-)

Nutrient availability and stoichiometry

• a role for productivity?• data inconsistent with resource-ratio model

Time

Pedogenic stage

Diversity

of N and

P forms

Plant

diversityresource

partitioning (+)

Resource partitioning

Diversity of N and P forms tend to increase in older soils

Nitrogen uptake and partitioning

Bever et al (2010) TREE

Hill et al (2011) Nature Climate Change

Phosphorus-acquisition strategies

P ‘scavengers’ = AM fungi

P ‘miners’ = non-mycorrhizal/cluster roots

Lambers et al (2008) Trends Ecol Evol

Turner (2008) J Ecol

Time

Pedogenic stage

Diversity

of N and

P forms

Plant

diversityresource

partitioning (+)

Resource partitioning

Perhaps, but no data yet!

Soil spatial

heterogeneity

Pedogenic stage

Plant

diversity

Soil spatial heterogeneity

Time

More niches, more species

homogeneoussoil conditions calcrete

Soil spatial heterogeneity does not explain plant diversity

Smaller islands burn less often:• last fire ~5000 years ago• accumulate humus• slower nutrient cycling• lower productivity• LOWER soil spatial heterogeneity• HIGHER plant species richness

Gundale et al (2011) Ecography

Arjeplogisland area

gradient, Sweden

Soil spatial

heterogeneity

Pedogenic stage

Plant

diversity

Soil spatial heterogeneity

Time

Niche theory = classical explanation, but does not seem to actually be important (at least in this island system)

Time

Belowground

heterotrophs

Pedogenic stage

Plant

diversity

Belowground heterotrophs

Plant-soil feedback

Janzen-Connell hypothesis

Host-specific pathogen

Mount St-Helens, USA

• volcanic eruption 1980

• high P, low N

• Lupinus lepidus = N2-fixing legume

• Pathogens/herbivores less abundant?

• Positive feedback = high dominance?

Photo: John Bishop

Barro Colorado Island, Panama

Photo: STRI

Mangan et al (2010) Nature

Time

Belowground

heterotrophs

Pedogenic stage

Plant

diversity

Belowground heterotrophs

• Positive feedback may explain lower species richness in young soils

• Negative feedback occurs in old soils: a role for plant species coexistence?

• More data needed

Time

Stage-

specific

species

pool size

Pedogenic stage

Abiotic

conditions

Plant

diversity species pool

hypothesis (+)

environmental

filtering (-)

Species pool hypothesis

Siskiyou Mountains, Oregon, USA

Grace et al (2011) Ecology

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

pH > 8

Time

Stage-

specific

species

pool size

Pedogenic stage

Abiotic

conditions

Plant

diversity species pool

hypothesis (+)

environmental

filtering (-)

Species pool hypothesis

Probably important in most systems

Nutrient

availability and

stoichiometry

Soil spatial

heterogeneity

Climate Parent material Topography Time

Belowground

heterotrophs

Stage-

specific

species

pool size

Commonness

of habitatPedogenic stage

Diversity

of N and

P forms

Abiotic

conditionsOrganisms

Plant

diversityresource

partitioning (+)

species pool

hypothesis (+)

negative plant-

soil feedback (+)

niche

theory (+)resource-ratio

model, productivity-

diversity (+/-)

environmental

filtering (-)

time-area

hypothesis (+)

Multivariate controls over plant diversity

Conclusions

• Ecosystem ‘build-up’ followed by ecosystem ‘decline

• Driven by loss of nutrients (e.g. P)

• Plant diversity often increases with soil age

• Multivariate controls over plant diversity:– productivity

– resource partitioning (N and P forms)

– plant-soil feedback

– species pools

Honours, PhD?etienne.laliberte@uwa.edu.au