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:
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,
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
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.
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
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:
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)
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?
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