Resilience of grassland plant communities as influenced by root herbivores under different land use intensities

 

Previous project phase (2014 - 2017)

Scientific investigators:

Prof. Dr. Florian Jeltsch

Michael Crawford

(Uni Potsdam)

Prof. Dr. Susanne Wurst

Dr. Ilja Sonnemann

(FU Berlin)

Background

Ecosystem resilience is an essential factor underlying the sustained production of natural resources and ecosystem services in complex systems faced with uncertainty and surprise. Root herbivory can have significant impact on grassland productivity and biodiversity under constant conditions. However, there is yet no knowledge on root herbivory impact on plant community recovery after disturbances, short-term stresses or nutrient pulses. Our project aims at assessing the role of root herbivory in plant community resilience under different land use intensities.

 

Hypotheses

Root herbivore effects on grassland resilience depend on:

    •     the nature of root herbivory
           including intensity / timing / distribution / feeding preference
    e.g. feeding preference for abundant plant species promotes recovery of species diversity
    •     the nature of disturbance/stress
           affecting predominantly plants / affecting also root herbivores / promoting dominance
           of specific plant species
    e.g. comprehensive stress that affects not only plants but also root herbivores generates a
            lag phase in root herbivore activity and weakens their impact
    •      the nature of the system
            including plant diversity / nutrient level
    e.g. root herbivory has strong effects in nutrient rich systems due to its impact on
            competition for space

     

    Methods

    Exploring the dynamic interactions and feedbacks between root herbivores and grassland plant communities after different types of disturbances and stresses requires a mechanistic approach. We will determine general aspects of root herbivore impact on plant community recovery in controlled greenhouse experiments and monitor plant and root herbivore abundance and community composition after disturbance/stress in field surveys. In addition, we will develop and apply process-based simulation models of both, root herbivores and the plant community. In a next step these models will be coupled to systematically investigate the role of plant-herbivore interactions for the resilience of the coupled system. We will focus on root herbivory by click beetle larvae of the genus Agriotes as widespread and abundant generalist root herbivores in European grasslands.

     

    Land use intensity and insect root herbivores: from spatial pattern to plant community feedback

     

    Previous project phase (2011 - 2014)

     

    Scientific investigators:

    Prof. Dr. Susanne Wurst

    Dr. Ilja Sonnemann

    (Freie Universität Berlin)

    Prof. Dr. Florian Jeltsch

    (University Potsdam)

     Goals:

    (1) to identify the determinants of the spatial distribution of root herbivores in grasslands and their relation to land use intensity

    (2) to determine the impact of root herbivores on plant-mediated below-/aboveground interactions under different land use intensities

    (3)  to determine root herbivore effects on plant performance and resulting community diversity under different land use intensities, and the relation of these effects to specific plant functional traits

    Hypotheses:

    (1a) On the regional scale the distribution of insect root herbivores is rather determined by soil parameters than by plant parameters, because unfavorable abiotic habitat conditions rule out their existence even if the food source is sufficiently abundant.

    (1b) Insect root herbivores are highly aggregated under low land use intensity and more evenly distributed under high land use intensity, because they respond to the presence of their host plants and/ or soil conditions which are more heterogeneously distributed in sites under low land use than in sites under high land use intensity.

    (1c) Horizontal migration of mobile insect root herbivores depends on food abundance, because travelling through soil is costly in terms of energy and predominantly done as a response to food depletion.

    (2a) Land use intensity influences the impact of root herbivory on the metabolomic profile of Plantago lanceolata, because land use changes the growth form of P. lanceolata with consequences for induction of systemic defence and compensatory growth responses.

    (2b) Land use intensity changes the plant-mediated effects of root herbivores on the aboveground food web, because the metabolic profile of P. lanceolata and aboveground insect communities are affected by land use.

    (2c) Under high land use intensity root herbivory decreases the root colonization by AMF and pathogens less than under low land use intensity, because in intensively managed, highly fertilized systems competition between root herbivores, AMF and pathogens for plant derived carbon is alleviated.

    (3a) The susceptibility of plant species to root herbivory can be predicted from the traits root palatability, root biomass and root foraging behavior, because these traits determine quality, quantity and distribution of root tissues in the soil and thereby the abundance and effect of root herbivores on plant growth.

    (3b) Root herbivory influences species coexistence in plant communities, because root herbivores show feeding preferences according to plant specific traits (see 3a) and, thus, may influence the outcome of interspecific competition.

    (3c) The effect of root herbivores on plant species coexistence is more pronounced under low than under high land use intensity, because (i) their presence/effect is more patchily concentrated under low land use intensity, thereby further strengthening the heterogeneity of sites (see 1a), (ii) plant species with strong root foraging behavior are expected to be more prone to root herbivores under heterogeneous conditions, due to the higher accumulation of root biomass in more nutrient rich patches, and therefore cannot become the dominant species.

    Methods:

    - empirical field work
    - experiments under controlled conditions
    - simulation experiments/modelling

     

    Previous project contribution of Prof. Dr. Susanne Wurst: Interact

    Previous project contribution of Prof. Dr. Florian Jeltsch: BEAM

    To top