4. Discussion
With this study we aimed to identify the independent effects of soil and
climate on plant trait variation within model grassland communities. Our
results point to three key findings. The first is that while individual
biomass responses to climate and soil are species-specific, species
dominance hierarchies (i.e., relative species contributions to community
biomass) are stable. The second finding is that soil differences drive
highly stochastic trait variation across both site and species. Lastly,
climate differences lead to consistent trait responses in all three
species, with species responses irrespective of site.
While these results exemplify the utility of plant-model communities as
an ecological tool, caution is necessary when interpreting results.
Firstly, we lacked statistical power to explore interactions between
specific climate and soil effects. We therefore limit interpretations to
descriptions of climate-specific differences and do not treat climates
as representations of any single abiotic gradient. To address separating
climate effects from soil effects in situ , we standardized the
local soil to the reference soil at each climate, however these results
must be interpreted in the context of the local climate. Further, our
experimental set-up did not preclude micro-organism contamination of the
reference soil and we did not characterize the microbial composition of
local soils. Local soils likely contained rich microbial communities
including Arbuscular Mycorrhizal Fungi (AMF). AMF are known symbionts of
the three species in this study and affect interspecific competition and
growth (Kyriazopoulos et al. 2014; Scheublin, Logtestijn, and Heijden
2007). Lastly, it was observed that reference soil treatments had larger
root biomass, while concurrently having higher rates of mortality,
potentially due to physical restriction belowground. With larger root
biomass, reference soil communities likely experienced faster dry-down
following precipitation, leaving individuals more susceptible to drought
stress (Turner 2019). While these points of concern are common in
ecological studies, they nonetheless should be considered when
interpreting experimental results.