Patterns of plant carbon, nitrogen, and phosphorus concentration in relation to productivity in China's terrestrial ecosystems

Abstract

Plant nitrogen (N) and phosphorus (P) content regulate productivity and carbon (C) sequestration in terrestrial ecosystems. Estimates of the allocation of N and P content in plant tissues and the relationship between nutrient content and photosynthetic capacity are critical to predicting future ecosystem C sequestration under global change. In this study, by investigating the nutrient concentrations of plant leaves, stems, and roots across China's terrestrial biomes, we document large-scale patterns of community-level concentrations of C, N, and P. We also examine the possible correlation between nutrient content and plant production as indicated by vegetation gross primary productivity (GPP). The nationally averaged community concentrations of C, N, and P were 436.8, 14.14, and 1.11 mg·g^-1 for leaves; 448.3, 3.04 and 0.31 mg·g^-1 for stems; and 418.2, 4.85, and 0.47 mg·g^-1 for roots, respectively. The nationally averaged leaf N and P productivity was 249.5 g C GPP·g^-1 N·y^-1 and 3,157.9 g C GPP·g^-1 P·y^-1, respectively. The N and P concentrations in stems and roots were generally more sensitive to the abiotic environment than those in leaves. There were strong power-law relationships between N (or P) content in different tissues for all biomes, which were closely coupled with vegetation GPP. These findings not only provide key parameters to develop empirical models to scale the responses of plants to global change from a single tissue to the whole community but also offer large-scale evidence of biome-dependent regulation of C sequestration by nutrients.

Keywords: allocation; leaf nitrogen productivity; leaf phosphorus productivity; nutrient concentrations; plant stoichiometry.

Fig. 1.

Changes in C, N, and P concentration in leaves, stems, and roots with mean annual temperature. Solid lines represent significant fits (P < 0.05), whereas dashed lines represent nonsignificant fits (P > 0.05).

Fig. 2.

Venn diagrams illustrating the relative contribution of climate, soil, and vegetation to the variation in C, N, and P concentration in the leaves, stems, and roots in China’s terrestrial ecosystems. The numbers in each subset figure show the percentage of total variation explained by the model and variations explained by independent effect of (a) vegetation type (green), (b) soil (pink), and (c) climate (blue), and the joint effect of (d) vegetation type and soil, (e) climate and soil, (f) vegetation type and climate, and (g) all three factors. The circle size indicates the relative contribution of the three factors.

Fig. 3.

Relationships between N (or P) concentrations (A) or contents (B) among tissues in different biomes in China.

Fig. 4.

Relationship between leaf N (or P) content and annual GPP in different biomes in China. Solid lines represent significant fits at P < 0.05, whereas dashed lines represent nonsignificant fits (P > 0.05).

Fig. 5.

Relationship of leaf N (A) and P (B) productivity to mean annual temperature and log-transformed precipitation in China’s terrestrial biomes.