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, 29.06.-03.07.2009

Results from large-scale grassland biodiversity experiments suggest positive relationship

between biodiversity and ecosystem functioning!

Ecological background

Insurance Hypothesis (McNaughton 1977,

Tilman 1994)

ecos

yste

m

sta

bilit

y

log diversity

Niche Complementarity Theory

(Berendse 1979, Loreau & Hector 2001)

tota

l res

ourc

e us

e

log diversity

Cedar Creek, USA The Jena Experiment, Germany

prod

uctiv

ity

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)

faci

litat

ion

(fro

m le

gum

es)

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-transferBiotic gradient (species richness) X X X (X)

Abiotic gradient (nutritional status in soil) X (X) X

Methods:

Fluorescence measurements + LAI X

15N natural abundance X X

15N tracer study X (Xplanned)

Cover + Biomass X X

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 15N 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 15N signature and the N-content of neigh-bouring species differently.

H3: Positive interactions, reflected by 15N 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 removalhay transfer

no soil removalhay transfer

soil removalno hay transfer

no soil removalno 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 NH4

+:NO3- in soil

No close correlation between the foliar δ15N and• total number of species, other soil N-parameters (Nmin, Ntotal, δ15N)

H1: The presence of a legume species will facilitate N-content of neighbouring species.

H2: Different legume species will affect the 15N signature and the N-content of neigh-bouring species differently.

H3: Positive interactions, reflected by 15N 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

15N-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

Thank you for your attention!