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, [email protected]
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