uwa workshop 2012
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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
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