Long-term ecosystem development       and belowground controls over          terrestrial plant diversityEtienne LalibertéS...
Organisms   Climate    Parent material        Topography   Time                                                           ...
Vegetation succession on Lake Michigan dunes                             Cowles (1899) Botanical Gazette
Classical vegetation succession model                                         ‘Climax’                    Johnson & Miyani...
Eugene P.Odum(1913-2002)         Odum (1969) The strategy of ecosystem development. Science 164:262-270
Hawaiian 4.1 million-year island          sequence                         Crews et al. (1995) Ecology
Jurien Bay >2-million-year dune   Jurien                                     Bay           chronosequence                 ...
Wardle et al (2004) Science
Maximum standing biomass(‘climax’) does not persistin the in the absence ofmajor disturbances:     • landslide     • glaci...
Long-term soil chronosequencesBuild-up (progressive) phase      Maximal phase                   Decline (retrogressive) ph...
What causes ecosystem decline?          Total P                    Total N               Soil age                         ...
Pedogenesis – Jurien Bay dunes                     Ecosystem progression Very young dune(10’s—100’s years)AC        Very l...
Pedogenesis – Jurien Bay dunes                     Ecosystem progression Very young dune                           Young d...
Pedogenesis – Jurien Bay dunes                        Ecosystem progression   Very young dune                            Y...
Pedogenesis – Jurien Bay dunes                        Ecosystem progression   Very young dune                            Y...
Implications for Australia               Most               ecologists               work here          Mt Michaud, Lesueu...
Plant strategiesSoil ‘available’ P     Leaf P concentration
Ancient soils, high plant diversity                                                            Kwongan shrublands, SWA    ...
Plant diversity along soil   chronosequences                   Graham Zemunik                       Laliberté et al (in pr...
Nutrient availability and stoichiometry                                                   Time                            ...
‘Humped-back’ model             • Low diversity at               high fertility             • Low diversity at            ...
Jurien BayFertility increases to apeak around 1000’s yearsand then declines in oldersoils
High diversity at low productivity in old soils  Low diversity at high          productivityLow diversity atlow productivi...
Multiple resource limitation and            diversity         Harpole & Tilman (2007) Nature
Multiple resource limitation and            diversity         Harpole & Tilman (2007) Nature
High diversity under strong P limitation                                                                        Strong P  ...
Nutrient availability and stoichiometry                                                              Time                 ...
Resource partitioning                                                  Time                           Pedogenic stageDiver...
Nitrogen uptake and partitioning                                            Bever et al (2010) TREE                 Hill e...
Phosphorus-acquisition strategies                                        P ‘miners’ = non-mycorrhizal/cluster roots    P ‘...
Turner (2008) J Ecol
Resource partitioning                                                   Time                           Pedogenic stageDive...
Soil spatial heterogeneity                          Time      Pedogenic stage         Soil spatial        heterogeneity   ...
More niches, more specieshomogeneoussoil conditions     calcrete
Soil spatial heterogeneity does not explain plant diversity                                         Smaller islands burn l...
Soil spatial heterogeneity                            Time      Pedogenic stage         Soil spatial                      ...
Belowground heterotrophs                                         Time      Pedogenic stage                          Belowg...
Plant-soil feedback                  Janzen-Connell                      hypothesis                  Host-specific pathogen
Mount St-Helens, USA                              • volcanic eruption                                1980                 ...
Barro Colorado Island, PanamaPhoto: STRI              Mangan et al (2010) Nature
Belowground heterotrophs                                                                    Time                          ...
Species pool hypothesis                                   Abiotic        environmental                        Time        ...
Siskiyou Mountains, Oregon, USAGrace et al (2011) Ecology
Carbonate dunes(Quindalup, stage 2: 100s-1000 years?)       pH > 8
Species pool hypothesis                                                        Abiotic        environmental               ...
Multivariate controls over plant                       diversity                                                          ...
Conclusions• Ecosystem ‘build-up’ followed by  ecosystem ‘decline• Driven by loss of nutrients (e.g. P)• Plant diversity o...
Honours, PhD?etienne.laliberte@uwa.edu.au
Long-term ecosystem development and plant diversity
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Long-term ecosystem development and plant diversity

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Lecture from ENVT3363: Ecological Processes, third-year course at the University of Western Australia (UWA).

Lecture on long-term ecosystem development, patterns of plant diversity along soil chronosequences, and potential controls over plant diversity

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  • lecturer in plant biologysmall teaching loadi get to choose what i want to teachthe topic of thislecture is essentially the main theme of my current research
  • one of the key outcomes of this Unit is for you to gain a comprehensive understanding of ecosystems, including the links between its different aspectsthis lecture fits well with this outcome because it first starts with a description of ecosystem processes – how soils formand then explores the consequences this has on terrestrial plant diversity – community processesthe rationale is that you cannot understand how plant diversity changes during long-term ecosystem development if you do not have a basic understanding of soil and ecosystem development in the first place
  • How soils forms, and how plant communities respond to changes in soil conditions during soil formation, is one of the oldest and most-studied themes in plant ecologywhy? because it’s inherently interestingalso because it understanding how communities develop in time is the first step towards predictionHenry Cowles classic studies on vegetation succession along Lake Michigan dunesthis process is generally called ‘succession’
  • Equilibrium‘Self-perpetuating’
  • This view of a ‘climax’ or equilibrium also influenced ecosystem ecologyEugene Odum was one of the first and most influential ecosystem ecologistthis figure from his classic 1969 paper on ecosystem development in Science reinforces this view that ecosystems eventually reach a ‘climax’ or an ‘equilibrium’initially lots of resources or nutrients, therefore production rises rapidly (and so does respiration).but gross production rises more rapidly than respiration, therefore net production increases and biomass accumulateseventually resources get taken up so gross production declineshowever, as you accumulate biomass, you need to maintain that biomasstherefore net production starts to declinenot much biomass accumulates – peak standing biomass -> equilibrium or ‘climax’this was an important model, but it’s only dealing with relatively short-term changes – does the equilibrium state persists over longer time scales?
  • to answer questions like this you need soil age gradients much longer than what Lake Michigan can give youone of the most well-known system are the Hawaiian islandshot spot that leads to volcanic eruptionsas islands move away from the hotspot, volcanic eruption ceaseshave not been glaciated for a long time, no major disturbancetherefore you can find soils and ecosystems from very young (a few 100’s years) to very old (4 million years)Sequence has been widely used to improve our understanding of nutrient cycling and nutrient limitation in terrestrial ecosystems
  • you don’t need to go as far as Hawaii to find similar long-term soil age sequencesin fact you’re sitting on one right nowall across the Swan Coastal Plain you find systems of dune that range from very young to very old, around 2 million yearsthis is what I use in my current research
  • there are a number of other long-term sequences like this around the world, around 10in different biomes and climatesforest biomass -- does it follow Odum’s model?
  • causes are pretty clear and are due to nutrient limitationyou start with low nitrogen because that comes from the atmospherehowever you start with all the phosphorus you’ll ever have because phosphorus comes mostly from minerals
  • Long-term ecosystem development and plant diversity

    1. 1. Long-term ecosystem development and belowground controls over terrestrial plant diversityEtienne LalibertéSchool of Plant Biology, UWAENVT3363 Ecological ProcessesSept 11, 2012
    2. 2. Organisms Climate Parent material Topography Time Ecosystem processes Soils Soil abiotic Soil biotic properties properties Community processes Terrestrial plant diversity
    3. 3. Vegetation succession on Lake Michigan dunes Cowles (1899) Botanical Gazette
    4. 4. Classical vegetation succession model ‘Climax’ Johnson & Miyanishi (2008) Ecology Letters
    5. 5. Eugene P.Odum(1913-2002) Odum (1969) The strategy of ecosystem development. Science 164:262-270
    6. 6. Hawaiian 4.1 million-year island sequence Crews et al. (1995) Ecology
    7. 7. Jurien Bay >2-million-year dune Jurien Bay chronosequence Perth0-7 ky120-500 ky >2000 ky
    8. 8. Wardle et al (2004) Science
    9. 9. Maximum standing biomass(‘climax’) does not persistin the in the absence ofmajor disturbances: • landslide • glaciation • volcanic eruptionEcosystem decline orretrogression Wardle et al (2004) Science
    10. 10. Long-term soil chronosequencesBuild-up (progressive) phase Maximal phase Decline (retrogressive) phase Soil age Peltzer et al (2010) Ecol Monogr
    11. 11. What causes ecosystem decline? Total P Total N Soil age 10 mg kg-1
    12. 12. Pedogenesis – Jurien Bay dunes Ecosystem progression Very young dune(10’s—100’s years)AC Very low N High P
    13. 13. Pedogenesis – Jurien Bay dunes Ecosystem progression Very young dune Young dune(10’s—100’s years) (~1000’s years)A AC C Highest N Very low N High P High P Peak fertility/productivity
    14. 14. Pedogenesis – Jurien Bay dunes Ecosystem progression Very young dune Young dune (10’s—100’s years) (~1000’s years) A A C C Highest N Very low N High P High P Peak fertility/productivity Ecosystem retrogression Old dune(~500,000 years)A low NAe low PEB1B2
    15. 15. Pedogenesis – Jurien Bay dunes Ecosystem progression Very young dune Young dune (10’s—100’s years) (~1000’s years) A A C C Highest N Very low N High P High P Peak fertility/productivity Ecosystem retrogression Old dune Very old dune(~500,000 years) (>2,000,000 years)A low N OAe very low P AEB1 EaB2 E low N extremely low P ‘terminal state’
    16. 16. Implications for Australia Most ecologists work here Mt Michaud, Lesueur National ParkProductivity Most of Australian terrestrial ecosystems are here Soil age
    17. 17. Plant strategiesSoil ‘available’ P Leaf P concentration
    18. 18. Ancient soils, high plant diversity Kwongan shrublands, SWA Yasuní, Ecuador >70 species in 10x10-m plot >1,100 tree species in 25-ha plot little dominance weathered silty clay soils strongly leached sandy soilsSource: http://katerva.org Valencia et al (2004) J Ecol Lamont et al (1977) Nature
    19. 19. Plant diversity along soil chronosequences Graham Zemunik Laliberté et al (in preparation)
    20. 20. Nutrient availability and stoichiometry Time Pedogenic stage Nutrient availability and stoichiometry resource-ratio model, productivity- diversity (+/-) Plant diversity
    21. 21. ‘Humped-back’ model • Low diversity at high fertility • Low diversity at very low fertility • Highest diversity at intermediate fertility Grime (1973) Nature
    22. 22. Jurien BayFertility increases to apeak around 1000’s yearsand then declines in oldersoils
    23. 23. High diversity at low productivity in old soils Low diversity at high productivityLow diversity atlow productivity in young soils
    24. 24. Multiple resource limitation and diversity Harpole & Tilman (2007) Nature
    25. 25. Multiple resource limitation and diversity Harpole & Tilman (2007) Nature
    26. 26. High diversity under strong P limitation Strong P N limitation Co-limitation Co-limitation P limitation limitationLaliberté et al. (2012) J Ecol
    27. 27. Nutrient availability and stoichiometry Time Pedogenic stage Nutrient • a role for productivity? availability and • data inconsistent with resource-ratio model stoichiometry resource-ratio model, productivity- diversity (+/-) Plant diversity
    28. 28. Resource partitioning Time Pedogenic stageDiversityof N and Diversity of N and P formsP forms tend to increase in older soils Plant resource diversity partitioning (+)
    29. 29. Nitrogen uptake and partitioning Bever et al (2010) TREE Hill et al (2011) Nature Climate Change
    30. 30. Phosphorus-acquisition strategies P ‘miners’ = non-mycorrhizal/cluster roots P ‘scavengers’ = AM fungiLambers et al (2008) Trends Ecol Evol
    31. 31. Turner (2008) J Ecol
    32. 32. Resource partitioning Time Pedogenic stageDiversityof N andP forms Perhaps, but no data yet! Plant resource diversity partitioning (+)
    33. 33. Soil spatial heterogeneity Time Pedogenic stage Soil spatial heterogeneity Plant diversity
    34. 34. More niches, more specieshomogeneoussoil conditions calcrete
    35. 35. 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 Arjeplogisland area gradient, Sweden Gundale et al (2011) Ecography
    36. 36. Soil spatial heterogeneity Time Pedogenic stage Soil spatial Niche theory = classical heterogeneity explanation, but does not seem to actually be important (at least in this island system) Plant diversity
    37. 37. Belowground heterotrophs Time Pedogenic stage Belowground heterotrophs Plant diversity
    38. 38. Plant-soil feedback Janzen-Connell hypothesis Host-specific pathogen
    39. 39. 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
    40. 40. Barro Colorado Island, PanamaPhoto: STRI Mangan et al (2010) Nature
    41. 41. Belowground heterotrophs Time Pedogenic stage• Positive feedback may Belowgroundexplain lower species heterotrophsrichness in young soils• Negative feedback occursin old soils: a role for plant Plant diversityspecies coexistence?• More data needed
    42. 42. Species pool hypothesis Abiotic environmental Time conditions filtering (-) Pedogenic stage Stage- specific species pool size Plant diversity species pool hypothesis (+)
    43. 43. Siskiyou Mountains, Oregon, USAGrace et al (2011) Ecology
    44. 44. Carbonate dunes(Quindalup, stage 2: 100s-1000 years?) pH > 8
    45. 45. Species pool hypothesis Abiotic environmental Time conditions filtering (-) Pedogenic stage Stage- specific species pool sizeProbably important in most systems Plant diversity species pool hypothesis (+)
    46. 46. Multivariate controls over plant diversity Abiotic environmental Organisms Climate Parent material Topography Time conditions filtering (-) time-area Pedogenic stage Commonness hypothesis (+) Stage- of habitat specific species pool sizeDiversity Nutrient Soil spatial Belowgroundof N and availability and heterogeneity heterotrophsP forms stoichiometry niche negative plant- resource-ratio theory (+) soil feedback (+) model, productivity- diversity (+/-) Plant resource diversity species pool partitioning (+) hypothesis (+)
    47. 47. 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
    48. 48. Honours, PhD?etienne.laliberte@uwa.edu.au

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