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Positive and negative dynamics of plant- plant interactions and their functional role in regulating ecosystem processes Lea L.A. Märtin, SER summer school.

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Presentation on theme: "Positive and negative dynamics of plant- plant interactions and their functional role in regulating ecosystem processes Lea L.A. Märtin, SER summer school."— Presentation transcript:

1 Positive and negative dynamics of plant- plant interactions and their functional role in regulating ecosystem processes Lea L.A. Märtin, SER summer school in Münster,

2 Results from large-scale grassland biodiversity experiments suggest positive relationship between biodiversity and ecosystem functioning! Ecological background Insurance Hypothesis (McNaughton 1977, Tilman 1994) ecosystem stability log diversity Niche Complementarity Theory (Berendse 1979, Loreau & Hector 2001) total resource use log diversity Cedar Creek, USA The Jena Experiment, Germany productivity log diversity Biodiversity-Productivity Relationship (Naeem & Thompson 1994, Tilman 2000) N2 fixed by legume altered belowground processes Facilitation & “Ecosystem Engineers” (Jones 1997) Stress Gradient Hypothesis (Bertness & Callaway 1994) facilitation (from legumes) abiotic stress

3 Overview FCE (facilitation- competition) AsDe (assembly- decomposition) EVENT (biodiversity– climate change) Garchinger Heide (restoration ecology) Theoretical background BD-Prod, Stress Grad. Hyp. BD-Prod, N-transfer Stress Grad. Hyp., Insurance Hyp. Stress Grad. Hyp., N-transfer Biotic gradient (species richness) XXX(X) Abiotic gradient (nutritional status in soil) X(X)X Methods: Fluorescence measurements + LAI X  15 N natural abundance XX  15 N tracer study X(X planned ) Cover + BiomassXX We aim to understand processes responsible for varying ecosystem services in grasslands along gradients of a)species and functional diversity b)abiotic factors like soil N-status and (weather) disturbances to apply the results to restoration projects.

4 Restoration Project „Garchinger Heide“ no topsoil removal topsoil removal no hay transfer hay transfer restoration of calcareous grassland treatments applied in 1993 (collaboration: Kathrin Kiehl) August 2007: collection of plant pairs (legume+neighbour) pairs of target (stress tolerant) and non-target (mesic) species were collected evaluation of  15 N and N-content of plant leaves

5 Restoration Project „Garchinger Heide“ H1: The presence of a legume species will facilitate N-content of neighbouring species. H2: Different legume species will affect the  15 N signature and the N-content of neigh- bouring species differently. H3: Positive interactions, reflected by  15 N and N-values, will increase along a gradient of abiotic stress. Collected species: Tri = Trifolium pratense L. (legume) Lot = Lotus corniculatus L. (legume) Gal = Galium mollugo agg. (herb) Ant = Anthyllis vulneraria L. s. l. (legume) Dor = Dorycnium germanicum (Gremli) Rikli (legume) Hel = Helianthemum nummularium (L.) Mill. s. l. (herb) stress-tolerant species: mesic species:

6 Restoration Project „Garchinger Heide“ soil removal hay transfer no soil removal hay transfer soil removal no hay transfer no soil removal no hay transfer Open questions: Why are the δ15N values so extremely low in +r+h treatment? What are is the reason for the successive increase in the δ15N values with decreasing restoration effort? Why does the hay transfer affect the δ15N signal over such a long time periode? Close correlation in non-legume species between the foliar δ15N and number of target species, the ratio NH 4 + :NO 3 - in soil No close correlation between the foliar δ15N and total number of species, other soil N-parameters (N min, N total, δ15N)

7 H1: The presence of a legume species will facilitate N-content of neighbouring species. H2: Different legume species will affect the  15 N signature and the N-content of neigh- bouring species differently. H3: Positive interactions, reflected by  15 N and N-values, will increase along a gradient of abiotic stress. Restoration Project „Garchinger Heide“ Neither confirmed nor rejected: method does not work to investigate facilitation in soil-removal treat. soil N-dynamics seems to override facilitation signal now we try to separate N-dynamics signal from facilitation signal -soil removal/-hay (mowed) -soil removal/+hay +soil removal/-hay +soil removal/+hay  15 N-signal as indicator for restoration success?

8 Thanks to all the people who helped and supported me during my work! FZ Jülich: Vicky Temperton, Uwe Rascher, Ulrich Schurr, Beate Uhlig Manfred Michulitz and his team (ZCH) for element analysis Andreas Lücke (ICG-4) for 15N-analysis FZ Jülich: Vicky Temperton, Uwe Rascher, Ulrich Schurr, André Moersch Universität Bayreuth: Carl Beierkuhnlein, Anke Jentsch, Jürgen Kreyling, Mirjam Pfeiffer, Christin Merczynski, Kerstin Grant, Thomas Gollan FZ Jülich: Vicky Temperton, Uwe Rascher, Ulrich Schurr, Edelgard Schölgens Andreas Lücke (ICG-4) for 15N-analysis TU München: Kathrin Kiehl (now in OS), Daniela Röder and: Ingo Scholz

9 Thank you for your attention!


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