Multivariate analyses of soil abiotic parameters, soil fungal,
bacterial and plant communities
We tested the effects of conditioning time, conditioning plant
community, and forb:grass ratio including all interactions on
soil abiotic composition (soil nutrients and including
soil pH) with a permutational analysis of variance (permanova; 999
permutations) using Euclidian distances. Furthermore, the effects on
soil fungal (ITS2), soil bacterial
(16S), and plant community composition were assessed
with permanova (999 permutations) using Bray-Curtis dissimilarity.
Fungal and bacterial data were square root-transformed and standardized
using Wisconsin double standardization prior to calculating Bray-Curtis
dissimilarity. Plot number was included in the models as a random effect
to indicate that the one- and two-year conditioned subplots belong to
the same plot. All multivariate analyses were performed in R, using the
‘vegan ’ package (R Core Team 2018; Oksanen et al. 2018)
and community composition was visualized using ordination based on
non-metric multidimensional scaling, using the ‘ggplot2 ’ package
(Wickham 2016).
To assess whether responding plant communities responded to conditioning
time and forb:grass ratio, and whether particular responding plant
species drove these responses, we performed (restricted) redundancy
analyses with either forb:grass ratio (categorical), or conditioning
time (categorical) as explanatory variables. These analyses were
performed and visualized for each of the six conditioning communities
separately. Redundancy analyses and visualizations were performed in
Canoco 5.03 (Microcomputer Power, Ithaca NY, USA).