The production of biomass by plant communities is co-limited by climatic and edaphic processes. Separating these processes is notoriously difficult due to covariation, non-independence, and non-linearities. This may be particularly problematic for coordinated distributed experiments or studies operating along larger gradients that attempt to isolate drivers of biomass production.
Material and Methods
We developed and implemented a standardized phytometer unit grown in standard substrates and local soils as a common reference system across 18 experimental sites spanning 11 countries in Europe. These sites crossed a large gradient of aridity and soil types. After a 50-day growth period, we used linear regression and model selection to investigate principle and secondary drivers of biomass production in the phytometer communities.
We show that the coupled use of standardized plant communities grown in local site soils and standard substrates reveals previously masked climate-soil effects on biomass production. Specifically, aridity was the strongest determinate of biomass production in local soils (R2 = 0.73). Our standard substrate phytometers isolated the climatic drivers of biomass production, and relativizing to their site mean showed that phosphorus availability was a hidden driver of biomass production in the local soil (R2 = 0.45).
Our phytometer-common-metric method is a flexible tool for isolating climatic and edaphic contributions to biomass production. Here, we demonstrated its use across a continental gradient by showing that after accounting for the central climatic driver of aridity, previously masked soil drivers became more apparent.