Recommandé
Recommandé
Contenu connexe
Tendances
Tendances (19)
En vedette
Similaire à Long-term ecosystem development and plant diversity
Similaire à Long-term ecosystem development and plant diversity (20)
Dernier
Dernier (20)
Long-term ecosystem development and plant diversity
- 1. Long-term ecosystem development and belowground controls over terrestrial plant diversity Etienne Laliberté School of Plant Biology, UWA ENVT3363 Ecological Processes Sept 11, 2012
- 2. Organisms Climate Parent material Topography Time Ecosystem processes Soils Soil abiotic Soil biotic properties properties Community processes Terrestrial plant diversity
- 3. Vegetation succession on Lake Michigan dunes Cowles (1899) Botanical Gazette
- 4. Classical vegetation succession model ‘Climax’ Johnson & Miyanishi (2008) Ecology Letters
- 5. Eugene P. Odum (1913-2002) Odum (1969) The strategy of ecosystem development. Science 164:262-270
- 6. Hawaiian 4.1 million-year island sequence Crews et al. (1995) Ecology
- 7. Jurien Bay >2-million-year dune Jurien Bay chronosequence Perth 0-7 ky 120-500 ky >2000 ky
- 8. Wardle et al (2004) Science
- 9. 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
- 10. Long-term soil chronosequences Build-up (progressive) phase Maximal phase Decline (retrogressive) phase Soil age Peltzer et al (2010) Ecol Monogr
- 11. What causes ecosystem decline? Total P Total N Soil age 10 mg kg-1
- 12. Pedogenesis – Jurien Bay dunes Ecosystem progression Very young dune (10’s—100’s years) A C Very low N High P
- 13. 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
- 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 N Ae low P E B1 B2
- 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 O Ae very low P A E B1 Ea B2 E low N extremely low P ‘terminal state’
- 16. Implications for Australia Most ecologists work here Mt Michaud, Lesueur National Park Productivity Most of Australian terrestrial ecosystems are here Soil age
- 17. Plant strategies Soil ‘available’ P Leaf P concentration
- 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 soils Source: http://katerva.org Valencia et al (2004) J Ecol Lamont et al (1977) Nature
- 19. Plant diversity along soil chronosequences Graham Zemunik Laliberté et al (in preparation)
- 20. Nutrient availability and stoichiometry Time Pedogenic stage Nutrient availability and stoichiometry resource-ratio model, productivity- diversity (+/-) Plant diversity
- 21. ‘Humped-back’ model • Low diversity at high fertility • Low diversity at very low fertility • Highest diversity at intermediate fertility Grime (1973) Nature
- 22. Jurien Bay Fertility increases to a peak around 1000’s years and then declines in older soils
- 23. High diversity at low productivity in old soils Low diversity at high productivity Low diversity at low productivity in young soils
- 24. Multiple resource limitation and diversity Harpole & Tilman (2007) Nature
- 25. Multiple resource limitation and diversity Harpole & Tilman (2007) Nature
- 26. High diversity under strong P limitation Strong P N limitation Co-limitation Co-limitation P limitation limitation Laliberté et al. (2012) J Ecol
- 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. Resource partitioning Time Pedogenic stage Diversity of N and Diversity of N and P forms P forms tend to increase in older soils Plant resource diversity partitioning (+)
- 29. Nitrogen uptake and partitioning Bever et al (2010) TREE Hill et al (2011) Nature Climate Change
- 31. Phosphorus-acquisition strategies P ‘miners’ = non-mycorrhizal/cluster roots P ‘scavengers’ = AM fungi Lambers et al (2008) Trends Ecol Evol
- 32. Turner (2008) J Ecol
- 33. Resource partitioning Time Pedogenic stage Diversity of N and P forms Perhaps, but no data yet! Plant resource diversity partitioning (+)
- 34. Soil spatial heterogeneity Time Pedogenic stage Soil spatial heterogeneity Plant diversity
- 35. More niches, more species homogeneous soil conditions calcrete
- 36. 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 Arjeplog island area gradient, Sweden Gundale et al (2011) Ecography
- 37. 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
- 38. Belowground heterotrophs Time Pedogenic stage Belowground heterotrophs Plant diversity
- 39. Plant-soil feedback Janzen-Connell hypothesis Host-specific pathogen
- 40. 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
- 41. Barro Colorado Island, Panama Photo: STRI Mangan et al (2010) Nature
- 42. Belowground heterotrophs Time Pedogenic stage • Positive feedback may Belowground explain lower species heterotrophs richness in young soils • Negative feedback occurs in old soils: a role for plant Plant diversity species coexistence? • More data needed
- 43. Species pool hypothesis Abiotic environmental Time conditions filtering (-) Pedogenic stage Stage- specific species pool size Plant diversity species pool hypothesis (+)
- 44. Siskiyou Mountains, Oregon, USA Grace et al (2011) Ecology
- 45. Carbonate dunes (Quindalup, stage 2: 100s-1000 years?) pH > 8
- 46. Species pool hypothesis Abiotic environmental Time conditions filtering (-) Pedogenic stage Stage- specific species pool size Probably important in most systems Plant diversity species pool hypothesis (+)
- 47. 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 size Diversity Nutrient Soil spatial Belowground of N and availability and heterogeneity heterotrophs P forms stoichiometry niche negative plant- resource-ratio theory (+) soil feedback (+) model, productivity- diversity (+/-) Plant resource diversity species pool partitioning (+) hypothesis (+)
- 48. 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
Notes de l'éditeur
- 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