Seed Addition and Disturbance Experiment

Scientific investigators:

Project ESCAPE II

Prof. Dr. Norbert Hölzel

Dr. habil. Ute Hamer

PD Dr. Till Kleinebecker

Martin Freitag

(Uni Münster)

Core project Botany

Prof. Dr. Markus Fischer

Dr. Daniel Prati

Deborah Schäfer

Judith Hinderling

(Uni Bern)

 

Objectives

Our experiment addresses several unanswered questions which are highly important for basic ecological research but also for applied sciences of agriculture and nature conservation. On the one hand, these questions address ecosystem resilience, which is a measure of resistance against permanent changes. The resilience represents an important component of the stability of an ecosystem. Hereby, we will assess how fast grassland ecosystems including all their functions and processes recover after drastic disturbance and return to the initial conditions, in dependency on pre-disturbance diversity and land-use intensity. On the other hand, we will determine to what degree seeding of non-resident species can increase the local plant diversity and how such an increase may benefit ecosystem services such as yield, forage quality, pollination or carbon fixation. The seeding also allows one to estimate to what degree the current diversity of grassland is limited by a restricted dispersal capacity of plant species. Finally, the experiment tests the adaptive potential of grasslands to future climatic changes and extreme weather events, because a higher diversity of the vegetation could be associated with a higher resilience of the system.

Guiding question

  • How strongly does the resilience of a grassland ecosystem depend on plant diversity and land-use intensity?
  • How long do grasslands need to fully recover after disturbance with and without addition of species, including all ecosystem functions?
  • How strongly is the current vegetation limited by seed and microsite availability?
  • Which biotic, abiotic and land use driven filters determine the species composition of the grassland plant communities.
  • Has an experimental raise of plant diversity further positive effects on ecosystem functioning such as resilience, nutrient cycling and drought tolerance?

 

Experiment

At in total 73 grasslands with the three regions we conduct a seed addition and disturbance experiment (SADE) where seeding with a regional seed mixture and sward disturbance are combined along the land-use intensity gradient (Figure 1). As many different working groups from the biodiversity exploratories participate in the experiment, we will be able to asses a high number of above- and belowground parameters and processes, which can then be related to each other.

Design

At each grassland, the experiment consists of four 7 m × 7 m subplots at which effects of the factors “disturbance” and “seed addition” are studied. To also separate the individual effects of the two factors, not only the combination of but also the separate application of both factors is necessary. Additionally, an untreated control subplot is included in the experimental design. Seeding is done using a regionally produced seed mixture of native plants, which was compiled for each region separately. Thus, each plot within one of the regions will be treated with the same combination of grasses, herbs and legumes. As basis for the species mixture, we used vegetation records from earlier years from the single exploratories. Due to regional differences in species pools, seed mixtures differed in species richness among regions, ranging from 47 to 66 species. The disturbance of the topsoil is done by rotary cultivation or harrowing down to 10 cm soil depth and aims at setting back the current vegetation and creating open patches for germination. This enables us to monitor the regeneration of the ecosystem with and without addition of further plant species. Further details and first results of the experiment can be found in Klaus et al 2017 (doi: 10.1093/jpe/rtw062).

 

Project partners

Botany, Uni Bern
ESCAPE, Uni Münster
Crustfunction, Uni Rostock
RootHerb II, FU Berlin
SEBRA-MS, FU Berlin
SCALEMIC, Uni Hohenheim
AntAphid, Uni Bayreuth
Microorganisms, UFZ Halle
ForNit, Helmholtz Zentrum München

Project in previous phases

 

 

Seed addition in Hainich, Photo V. Klaus
Disturbance in Schwäbische Alb, Photo V. Klaus
Figure 1: Design of the seed addition and disturbance experiment SADE
 

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