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Kompetice rostlin

Kompetice rostlin. and maintenance of species diversity in plant communities.

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Kompetice rostlin

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  1. Kompetice rostlin and maintenance of species diversity in plant communities

  2. Definice kompeticeDůsledky přisedlého způsobu životaTypy kompeticeKomponenty kompetice o zdroje (resource competition)Modely Grime vs. TilmanEmpirické studie - pozorování a manipulativní experimentySpecies coexistence as violation of competitive exclusion principleGradients of species diversity and their causes

  3. Jak definovat kompetici? Grace (1990): “The variety of possible definitions of competition were discussed and it is safe to say that there is no universally accepted definition.” Možnosti: Podle efektu: interakce - - (obě populace jsou ovlivněny negativně. Velmi široká definice) Podle mechanismu: Grime: “The tendency of neighbouring plants to utilise the same resources” (tendence sousedících rostlin užít stejný zdroj) (velmi úzká definice) Řada dalších definic (někde mezi)

  4. Rostlinná kompetice: Rostliny jsou sedentární, takže: Konkurence probíhá jen mezi sousedy - důležitost prostorové struktury a heterogenity Jsou ovlivněny heterogenitou prostředí (velká morfologická plasticita jako řešení) Zůstávají během celého života na jednom místě Velikost individua je důležitější druhová identita (dospělý smrk lehce potlačí dospělou Calamagrostis ale dospělá Calamagrostis zahubí smrkový semenáč) Kompetice je velmi asymetrická (zvláště kompetice o světlo)

  5. Typy kompetice Obr. Connell

  6. Negativní efekt zprostředkovaný ohněm (strategie: Ať mě chcípne koza, hlavně když sousedovi chcípne kráva!)

  7. Allelopatie: vylučování toxických chemikálií do půdy (s cílem zabránit kompetici a růstu jiných rostlin) Problém s experimentálním prokázáním? Podobný efekt má produkce těžko rozložitelného opadu

  8. Apparent competition (zdánlivá kompetice) Příklad z Abisca Nízké břízy (Betula nana) jsou pod vyšším herbivorním tlakem pod kongenerickými vysokými břízami Betula tortuosa.

  9. Kompetice o zdroje (Resource competition) Zdroj musí být limitující, k dispozici v omezeném množství a oba organismy jej musí využívat. Rostliny si konkurují o světlo, vodu a v ní rozpuštěné živiny v půdě, ale též o opylovače Většinou si nekonkurují o CO2 - není důležitá absolutní koncentrace zdroje, ale rychlost jeho přísunu

  10. Mechanismy kompetice o zdroje

  11. Obě závislosti musí fungovat najednou. Pokud ne, potom není žádný vliv jednoho druhu na druhý.

  12. Rostliny ovlivňují jak zdroje (čerpáním), tak i charakteristiky nezdrojového charakteru. (Strom sníží hladinu světla stíněním, ale může ochránit před přehřátím. Efekt nemusí být vždy negativní Facilitation (obvyklé v nepříznivých podmínkách, nebo během nepříznivých období) [Vliv gapu na růst semenáčů byl positivní v průběhu vlhkých, a negativní v průběhu suchých let.]

  13. Classical Lotka-Volterra competition model Stable equilibrium if and i.e., when the inhibitive effect of each species on its own population is bigger than on the competitor (scaled by the corresponding K) => niche differentiation

  14. Tilman’s theory: the species with lower R* is the winner (i.e. species, able to growth in the lowest concentration of the resources)

  15. Population Resource

  16. According to the theory, number of coexisting species can not exceed the number of limiting resources Plant compete for light and [water and nutrients] (and often tens of species coexist on a small area) Competition for pollinators, seed dispersers Competition for space - the aboveground space is far from being filled by plant mass. “Competition for space” - the way sedentary organisms attempt to monopolise the resources.

  17. Grime vs. Tilman What is measure of competition success What are the trait of successful competitors (Grime - ability to capture the resources, high RGR, Tilman ability to grow at low resource levels, i.e. low R*) Importance of time scale

  18. Empirical studies of competition 1. (Indirect) From (spatial) pattern 2. (Direct) Manipulative experiments a) planting (sowing) monocultures and mixtures b) transplanting (e.g. into a sward and into a gap) c) removal of vegetation in surrounding of target d) removal a species from a community

  19. Regular (uniform) spatial patter is most probably consequence of increased mortality due to neighbours competition Aggregated (clumped) pattern has many causes, positive interactions being just one of less probable. (Most common: environmental heterogeneity, dispersal.) Changes in the pattern in the course of time are better evidence than static pattern.

  20. Correlating the available space (or quantity of neighbours) with performance of the individual. [Danger of the confounding factors, reverse causality, etc.] Eccentricity of the root system

  21. Experimental approaches

  22. Growing plants in monocultures and together Long tradition in agricultural research

  23. Pot competition experiment with Holcus lanatus, Lychnis flos cuculi and their mixture at different nutrient levels

  24. Additive design vs. replacement series

  25. Transplant experiments - Prunella vulgaris

  26. Clonal plant’s reaction to competition - increase of stolon length and orientation of stolons to “competition free” part

  27. Lychnis flos cuculi Tradeoff between flowering (in competitive environment) and producing secondary rosettes (in gaps)

  28. Removal of vegetation around target individuals Attempts to separate above- and belowground competition

  29. Dominant removal from a community

  30. Species coexistence: can be seen as a violation of the competitive exclusion principle Competitive exclusion principle: two species can not coexist for indefinitely long time in a homogeneous environment The equilibrium and non-equilibrium explanations Equilibrium: Environment is not homogeneous (niche differentiation) Non-equilibrium: time is not sufficient

  31. Medium disturbance hypothesis Repeated disturbance of medium intensity or frequency is able to prolong species coexistence

  32. What is medium depends on the productivity

  33. Density dependence - parasites & predators Janzen hypothesis - species diversity in tropics

  34. Gradients of species diversity Tree species richness in Canada and the United States. Contours connect points with the same approximate number of species per quadrat. Quadrat size is 2.5˚ x 2.5˚ south of 50˚N, and 2.5˚ x 5˚ north of 50˚N (Currie and Paquin 1987).

  35. Diversity usually decreases at very low and very high productivity Explanations of gradients of species diversity: 1. by community mechanisms 2. by species pool

  36. Diversity decrease at high nutrient levels: some of the hypotheses - less species adapted to high nutrient levels - higher competition at high nutrients (Grime) - switch from underground competition to competition for light (which is more asymmetric) - suppressed seedling recruitment

  37. Seedling recruitment of Gentiana pneumonanthe mown burned gap control

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