Soil multistability

Dr. Simone Cesarz, Leipzig
Prof. Dr. Nico Eisenhauer, Leipzig
Dr. Cordula Vogel, Dresden

The overall objective of this subproject is to study multidimensional soil stability, including temporal stability, resistance, and recovery as defined in the Coordination Proposal, as affected by plant diversity. We designed three coordinated work packages (WPs) to comprehensively assess soil multistability by considering biological, chemical, and physical dimensions that are key for soil functioning. We propose to use all unique facilities of this Research Unit by combining synthesis of long-term data in the Main Experiment and the ΔBEF Experiment, with performing new soil analyses in the DrY Experiment, ResCUE Experiment, and a joint CoMic Experiment. In close collaboration with other subprojects, we will assess soil processes and stability indicators that will be used to calculate soil multifunctionality and multistability indices. In WP1, we will explore short- and long-term effects of plant diversity on the stability of soil (microbial) properties. In WP2, we will explore if plant diversity effects on the magnitude and stability of soil properties increase with abiotic and biotic stresses. In WP3, we will explore if plant diversity increases the stability of multiple soil properties under hot drought. Taken together, results of these three WPs will provide novel insights into the stabilizing mechanisms of soil properties along plant diversity gradients. More specifically, we test the following hypotheses:

Hypotheses of WP1: Soil temporal stability.
H1.1: The relationships between soil microbial properties (respiration and biomass C) and plant diversity are positive and strengthen over time.
H1.2: Plant diversity decreases the temporal stability of soil microbial properties in the short term (2003-2009), does not significantly affect it in the intermediate term (2010-2016), and increases it the long term (2017-2024) of the experiment.
H1.3: The stabilizing effects of plant diversity on soil microbial properties as affected by (repeated) summer drought(s) (2018 and 2019) are more pronounced in subplots with plant and soil history (representing long-term effects) than in subplots without plant and soil history (representing short-term effects).
H1.4: Positive plant diversity effects on the temporal stability of soil microbial properties can be better predicted based on resistance to than on the recovery from drought.

Hypotheses of WP2: Soil stability along stress gradients. Plant diversity effects on the magnitude and stability of soil microbial properties increase with increasing levels of stress, such as indicated by years with a high drought index (H2.1) and increasing drought severity (H2.2). Moreover, plant communities stressed with the presence of plant pathogens will show stronger stabilizing effects of plant diversity on soil properties than plant communities without plant pathogens (H2.3).

Hypotheses of WP3: Soil stability under hot drought.
H3.1: Plant diversity increases the temporal stability, as well as resistance to and recovery after a hot drought, of multiple soil properties.
H3.2: Positive plant diversity effects on the temporal stability of soil microbial properties can be better predicted based on resistance to than on the recovery from a hot drought.