The scaling of fine root nitrogen versus phosphorus in terrestrial plants: A global synthesis

Abstract

Leaves and roots may differ in nitrogen (N), phosphorus (P) and N:P stoichiometry, which can influence plant growth and ecosystem functioning. As compared to leaves, however, relatively little is known about the N versus P scaling relationship and N:P stoichiometry in root systems, particularly in fine roots. We used a global dataset comprising 1,890 observations for a total of 763 terrestrial plant species in 123 families (spanning 433 sites world‐wide) to examine live fine root N and P concentrations and stoichiometry, and to determine the scaling of N versus P within and across different plant groups and ecosystems. The global geometric mean values of fine root N and P concentrations and N:P ratios were 10.84 mg/g, 0.94 mg/g and 11.55, respectively. Fine root N and P concentrations and N:P ratios varied both within and across plant groups and ecosystems. A 0.82‐power law described the scaling of fine root N with respect to P across the entire dataset and for major plant phylogenetic and functional groups; however, the numerical value of the N versus P scaling exponent declined from the tropics to higher latitudes and varied significantly at different local sites. Soil nutrient account for much of the variation observed in the scaling of fine root N versus P concentration at different local sites. This study advances our knowledge about limiting resource allocation strategies in below‐ground organs and has important implications for modelling plant growth at local, regional and global levels. A free Plain Language Summary can be found within the Supporting Information of this article.

Plant type dominates fine‐root C:N:P stoichiometry across China: A meta‐analysis

“…In our study, the geometric means of fine‐root N and P are 10.7 mg/g (arithmetic mean 11.7 mg/g) and 0.9 mg/g (arithmetic mean 1.0 mg/g), respectively. These values are nearly identical to that reported by Wang et al () and by Gordon and Jackson ().…”

“…trees, shrubs, graminoids, forbs, and conifers) and N‐fixation groups (i.e. legumes and non‐legumes) (Ma et al, ; Wang et al, ). Collectively, the database covered most terrestrial ecosystems, including forests, grasslands, and deserts.…”

“…All data presented in this manuscript are available from the Dryad Digital Repository https://doi.org/10.5061/dryad.j6q573n8q (Wang et al, ).…”

“…As the below‐ground analogue of leaves for plant nutrients uptake, fine‐root C, N, and P concentrations might be expected to have a similar phenomenon that was observed for leaves. Previous studies have shown that fine‐root as well as leaf C:N:P ratios can vary among plant groups and biomes (Thompson, Parkinson, Band, & Spencer, ; Wang et al, ; Yuan et al, ; Zhang et al, ; Zhao et al, ). However, much uncertainty remains as to how plant species community composition affects the geographical variation in fine‐root C:N:P stoichiometry.…”

Allocation Strategies for Seed Nitrogen and Phosphorus in an Alpine Meadow Along an Altitudinal Gradient on the Tibetan Plateau

“…For example, using extensive data sets for leaves, 2/3 and 3/4-power “laws” have been proposed by different workers ( Reich and Oleksyn, 2004 ; Wright et al, 2004 ; Niklas, 2006a ; Reich et al, 2010 ). Furthermore, based on 1890 observations of 763 terrestrial plant species, Wang et al (2019) have proposed a 0.82-power “law” for global fine root N vs. P across different plant groups and ecosystems. Consequently, the scaling exponent for the N vs. P scaling relationship manifests statistically significant differences between leaves and fine roots.…”