Positive and negative dynamics of plant interactions and

Positive and negative dynamics of plant interactions and their functional role in regulating ecosystem processes Lea L. A. Märtin, SER summer school in Münster, 29. 06. -03. 07. 2009

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

Overview Garchinger Heide (restoration ecology) Stress Grad. ecosystem Stress Grad. Webackground aim to understand processes responsible for varying BD-Prod, Theoretical Hyp. , Stress Grad. Hyp. N-transfer Insurance Hyp. N-transfer services in grasslands along gradients of Biotic gradient X X X (X) (species richness) a) species and functional diversity Abiotic gradient (nutritional X (X) X status in soil) b) abiotic factors like soil N-status and (weather) disturbances FCE (facilitationcompetition) Methods: Fluorescence measurements + LAI d 15 N natural abundance EVENT (biodiversity– climate change) to apply the results to restoration projects. X X d 15 N tracer study Cover + Biomass As. De (assemblydecomposition) X X (Xplanned)

Restoration Project „Garchinger Heide“ • 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 d 15 N and N-content of plant leaves no topsoil removal fer s n a r ay t h o n r nsfe a r t hay topsoil removal

Restoration Project „Garchinger Heide“ H 1: The presence of a legume species will facilitate N-content of neighbouring species. H 2: Different legume species will affect the d 15 N signature and the N-content of neighbouring species differently. H 3: Positive interactions, reflected by d 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) mesic species: 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:

Restoration Projectbetween „Garchinger Heide“ Close correlation in non-legume species the foliar δ 15 N and • number of target species, the ratio NH 4+: NO 3 - in soil No close correlation between the foliar δ 15 N and soil removal • total number of species, other soil N-parameters (N , δ 15 N) min total hay transfer no soil removal no hay transfer Open questions: • Why are the δ 15 N values so extremely low in +r+h treatment? • What are is the reason for the successive increase in the δ 15 N values with decreasing restoration effort? • Why does the hay transfer affect the δ 15 N signal over such a long time periode?

Restoration Project „Garchinger Heide“ H 1: The presence of a legume Neither species confirmed will facilitate nor rejected: N-content of neighbouring species. • method does not work to investigate facilitation in soil-removal treat. H 2: Different legume species will affect the d 15 N signature and the N-content of neigh • soil N-dynamics seems to override facilitation signal bouring species differently. • now we try to separate N-dynamics signal from facilitation signal H 3: Positive interactions, reflected by d 15 N and N-values, will increase along a gradient of abioticdstress. 15 N-signal as indicator for restoration success? -soil removal/-hay (mowed) -soil removal/+hay +soil removal/-hay +soil removal/+hay

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

Thank you for your attention!