Out of the shadows: multiple nutrient limitations drive relationships among biomass, light and plant diversity

Abstract

Summary1. The paradigmatic hypothesis for the effect of fertilisation on plant diversity represents a one-dimensional trade-off for plants competing for below-ground nutrients (generically) and above-ground light: fertilisation reduces competition for nutrients while increasing biomass and thereby shifts competition for depleted available light. 2. The essential problem of this simple paradigm is that it misses both the multivariate and mechanistic nature of the factors that determine biodiversity as well as their causal relationships. 3. We agree that light limitation, as DeMalach and Kadmon argue, can indeed be an important factor associated with diversity loss, and we presented it as an integral part of our tests of the niche dimension hypothesis. 4. We disagree with DeMalach and Kadmon that light is the 'main' factor explaining diversity, because this misrepresents the causal structure represented in the design of our experiment in which multiple nutrient addition was the ultimate causal driver of a suite of correlated responses that included diversity and light, and especially live and dead biomass, which are the factors that control light depletion.

Nitrogen and Phosphorus Additions Alter the Abundance of Phosphorus-Solubilizing Bacteria and Phosphatase Activity in Grassland Soils

“…This agrees with studies reporting that the abundance and diversity of Pseudomonads was higher on a nutrient-poor than on nutrient-rich medium (Aagot et al, 2001) and that most PSB were Pseudomonads in non-fertilized soils (Mander et al, 2012). A reason for the higher number of Enterobacterales than Pseudomonas OTUs under N and NP addition could be that they respond differently to changing amounts and composition of root exudates as can be expected by the reported strong changes in plant community composition in response to the nutrient additions (Rengel and Marschner, 2005;Badri and Vivanco, 2009;Harpole et al, 2017). This speculation is based on the observation that Enterobacterales and Pseudomonads prefer different substrates: Enterobacterales prefer amino acid glycine, while Pseudomonas prefer sugars (Goldfarb et al, 2011).…”

The Neolithic Plant Invasion Hypothesis: the role of preadaptation and disturbance in grassland invasion

“…Instead, it is more likely that the non‐native species responded more rapidly, in turn suppressing native flora. This can happen if competition shifts to other limiting resources such as moisture, light or other nutrients (phosphorus, potassium) (Harpole et al ., , ). This possibility seems to be supported by a comparison of nutrient responses of 14 congeneric invasive and noninvasive European grassland species (Schlaepfer et al ., ); the invasive species responded to enrichment by producing more biomass and flowers.…”

Seeking salt: herbivorous prairie insects can be co‐limited by macronutrients and sodium

“…For this reason, the applicability of Leibig's law of the minimum to populations and communities has been questioned (e.g. Danger et al 2008), and now multiple resource limitation is generally recognised to likely be common in plant communities (Harpole et al 2011(Harpole et al , 2017Fay et al 2015). Co-limitation may occur via several different pathways (Sperfeld et al 2016): independent co-limitation occurs when two different nutrients separately enhance populations, and these effects are further enhanced when both nutrients are abundant: simultaneous limitation occurs when neither nutrient positively affects an organism, but together they produce a positive effect when a critical threshold of both is reached; and serial co-limitation occurs when one of the nutrients produces a moderately positive effect that is enhanced by the addition of some other limiting nutrient.…”