Rewilding with invertebrates and microbes to restore ecosystems: present trends and future directions

Abstract

1. Restoration ecology has historically focused on reconstructing communities of highly visible taxa whilst less visible taxa, such as invertebrates and microbes, are ignored. This is problematic as invertebrates and microbes make up the vast bulk of biodiversity and drive many key ecosystem processes, yet they are rarely actively reintroduced following restoration, potentially limiting ecosystem function and biodiversity in these areas. 2. In this review, we discuss the current (limited) incorporation of invertebrates and microbes in restoration and rewilding projects. We argue that these groups should be actively rewilded during restoration to improve biodiversity and ecosystem function outcomes and highlight how they can be used to greater effect in the future. For example, invertebrates and microbes are easily manipulated, meaning whole communities can potentially be rewilded through habitat transplants in a practice that we refer to as “whole-of-community” rewilding. 3. We provide a framework for whole-of-community rewilding and describe empirical case studies as practical applications of this under-researched restoration tool that land managers can use to improve restoration outcomes. 4. We hope this new perspective on whole-of-community restoration will promote applied research into restoration that incorporates all biota, irrespective of size, whilst also enabling a better understanding of fundamental ecological theory, such as colonisation- competition trade-offs. This may be a necessary consideration as invertebrates that are important in providing ecosystem services are declining globally; targeting invertebrate communities during restoration may be crucial in stemming this decline.

Soil inoculum identity and rate jointly steer microbiomes and plant communities in the field

“…A better functioning new soil community could, in turn, be important for the establishment of target plant species. Many functions that soil biota provide are density dependent [14] and the density of soil organisms should be sufficiently high to avoid mortality and inbreeding depression [11,12]. In this study, upland meadow soil inoculation also introduced some keystone taxa which may play key roles by determining microbiome functioning, such as, Acidobacteriota, Proteobacteria and Bacteroidota.…”

“…It is likely that the introduced soil community survives and establishes best in the local habitat and that increasing the amount of inoculated soil at the recipient site increased resemblance to the original habitat conditions, e.g. by preventing the effects of desiccation and by better resembling the original abiotic conditions such as nutrient availability and pH [11,12]. A better functioning new soil community could, in turn, be important for the establishment of target plant species.…”

“…The copyright holder for this preprint this version posted August 24, 2021. ; https://doi.org/10.1101/2021.08.22.456585 doi: bioRxiv preprint community, inoculation with a small amount of donor soil will give similar "steering power" of the plant and soil communities as larger amounts of donor soil (8,11). How the amount of donor soil that is used for inoculation influences the establishment of plant and soil communities in the field is still not known.…”

“…For example, Wubs et al recently showed that in a former arable field the composition of both the soil and the plant community was steered towards a predefined target community when using soil inoculum collected from a semi-restored grassland and from a heathland [8]. While there is now evidence that inoculation with soil from two distinctly different ecosystems can induce directional changes in the soil and in plants communities in the field [11], a major outstanding question is how specific these inoculations are and whether inoculation with soil originating from underneath different plant communities but from a similar ecosystem will also lead to differential development of the soil microbial community and ultimately the entire ecosystem at the recipient site.…”

“…Results from a controlled pot experiment show that indeed there was a positive effect between the amount of inoculated soil and plant biomass [14]. However, in the field, and over longer time periods, it is also possible that due to positive feedbacks between the soil and plant communities, inoculation with a small amount of donor soil will give similar "steering power" to the soil microbiome and plant communities as larger amounts of donor soil [8,11]. How the amount of donor soil that is used for inoculation influences the establishment of soil microbiome and plant communities in the field is still not known.…”