Spatiotemporal disturbance characteristics determine functional stability and collapse risk of simulated microbial ecosystems

Sara König,Martin Thullner,Anja Worrich,Karin Frank,Matthias Kästner,Hauke Harms,Anja Miltner,Thomas Banitz,Florian Centler,Lukas Y Wick

doi:10.1038/s41598-018-27785-4

Abstract

Terrestrial microbial ecosystems are exposed to many types of disturbances varying in their spatial and temporal characteristics. The ability to cope with these disturbances is crucial for maintaining microbial ecosystem functions, especially if disturbances recur regularly. Thus, understanding microbial ecosystem dynamics under recurrent disturbances and identifying drivers of functional stability and thresholds for functional collapse is important. Using a spatially explicit ecological model of bacterial growth, dispersal, and substrate consumption, we simulated spatially heterogeneous recurrent disturbances and investigated the dynamic response of pollutant biodegradation – exemplarily for an important ecosystem function. We found that thresholds for functional collapse are controlled by the combination of disturbance frequency and spatial configuration (spatiotemporal disturbance regime). For rare disturbances, the occurrence of functional collapse is promoted by low spatial disturbance fragmentation. For frequent disturbances, functional collapse is almost inevitable. Moreover, the relevance of bacterial growth and dispersal for functional stability also depends on the spatiotemporal disturbance regime. Under disturbance regimes with moderate severity, microbial properties can strongly affect functional stability and shift the threshold for functional collapse. Similarly, networks facilitating bacterial dispersal can delay functional collapse. Consequently, measures to enhance or sustain bacterial growth/dispersal are promising strategies to prevent functional collapses under moderate disturbance regimes.

Highlights

Soil microorganisms provide a variety of important ecosystem services such as litter decomposition, nutrient cycling, climate regulation, and pollutant degradation
We simulated virtual microbial ecosystems exposed to disturbances introduced as recurring shocks with the effect of a drastic reduction of bacterial biomass in the disturbed area
With our simulations of recurrent disturbance events affecting a simplified microbial ecosystem, we identified the disturbance characteristics as key factors influencing the long-term functional stability in terms of the biodegradation performance and the probability of a functional collapse

Summary

Introduction

Soil microorganisms provide a variety of important ecosystem services such as litter decomposition, nutrient cycling, climate regulation, and pollutant degradation. For assessing the potential risk of such functional collapses, the underlying key factors need to be identified These factors include characteristics of the disturbances such as their frequency, intensity or spatial pattern, and specific properties of the considered ecosystem. We use a numerical simulation approach to investigate the effects of recurrent disturbances varying in their spatial and temporal occurrence on the functional performance and stability of microbial ecosystems (using bacterial pollutant degradation as an exemplary ecosystem function). We uncover the interrelated role of (i) disturbance characteristics (frequency and spatial pattern), (ii) microbial properties (specific growth rate and dispersal ability), and (iii) networks facilitating bacterial dispersal (e.g. mycelial networks) for the long-term impact of recurrent disturbances on the biodegradation function

Methods

Results

Conclusion