Divergent nitrogen and phosphorus allocation strategies in terrestrial plant leaves and fine roots: a global meta-analysis

The quantification of the allocation of nitrogen (N) and phosphorus (P) among plant organs is essential to improve our understanding of plant growth, life-history strategies, and ecosystem nutrient and energy cycles. However, allocation strategies of N and P between terrestrial plant leaves and fine roots are unclear.

Here, we compiled a global dataset comprising 807 terrestrial plant species to analyze the stoichiometric scaling of N and P between leaves and fine roots across species, families, plant groups, biomes, and locations.

We found that N and P, and N:P ratios manifest different scaling exponents (α-values) between leaves and fine roots. Specifically, overall α_N and α_P were >1 and <1, respectively, and α_N:P = 1, indicating a higher proportional increase of N to fine roots and P to leaves. However, there were differences in α_N, α_P, and α_N:P among major species, families, plant groups, biomes, and locations. In addition, α_N and α_N:P increased with latitude; there was no clear trend for α_P. Mean annual temperature accounted for the greatest proportion of variation in αN, whereas soil total P accounted for the greatest proportion of variation in α_P and αN:P.

Synthesis. Our results demonstrate a divergent N and P allocation strategy between leaves and fine roots in terrestrial plants. This study improves our understanding of the effects of the environment (including changes in global climate, and life history strategies) on nutrient allocation patterns between these two important plant organs.