Seed Addition and Disturbance Experiment

 

Previous project phase (2014 - 2017)

Scientific investigators:

Project ESCAPE

Prof. Dr. Norbert Hölzel

Dr. habil. Ute Hamer

PD Dr. Till Kleinebecker

Dr. Valentin Klaus

(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 important for basic ecological research as well as for applied perspective concerning 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 their functions and processes, recover after drastic disturbances and return to the initial condition. Additionally we will study to what degree the resilience depends on the pre-disturbance diversity and the land-use intensity of the grasslands. 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 increased diversity 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.

Experiment

At 25 established grassland plots in each of the three exploratories, we conduct a seed addition and disturbance experiment (SADE) where seeding with a regional seed mixture and top soil disturbance are combined (Figure 1). The experiment aims at studying the extent of dispersal and microsite limitation of the current plant diversity. This approach also enables us to quantify if the experimental increase in plant diversity also positively affects distinct ecosystem processes and functions. At the meantime, the resilience of the ecosystem will be studied, assessing the role of the pre-disturbance diversity of the sites for the recovery of the ecosystem and its functioning. To include effects of land management, study plots are arranged along a land-use intensity gradient. 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 study plot, the experiment consists of four 7 m by 7 m subplots at which effects of the factors “disturbance” and “seed addition” will be studied. To also separate the individual effects of the two factors, not only the combination of “disturbance” and “seed addition” but also the separate application of both factors is necessary. Additionally, an untreated control site is included in the experimental design. Seeding will be done using a regionally produced seed mixture of native plants, which will be 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 use vegetation records from earlier years from the single exploratories. The disturbance of the topsoil is done by rotary cultivation or harrowing and aims at setting back the current vegetation and creating open microsites for germination. This enables us to monitor the regeneration of the ecosystem with and without addition of further plant species.

 

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?
  • Has an experimental raise of plant diversity further positive effects on ecosystem functioning such as resilience, nutrient cycling and drought tolerance?

 

Project partners

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

 

 

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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