Ecological strategies of evergreen and deciduous woody species: including nitrogen and phosphorus allocation among organs, and element-based network

Nitrogen (N) and phosphorus (P) allocation strategies are central to plant ecology, yet most studies oversimplify stems by ignoring the functional divergence between bark and wood. In addition, the combination of stoichiometric homeostasis and network analysis to elucidate adaptation strategies between evergreen and deciduous species has rarely been investigated. Here, we measured N and P concentrations across the plant–soil system (leaf, bark, wood, root, and soil) in 75 subtropical woody species (44 evergreen and 31 deciduous). Bark exhibited a lower N vs. P scaling exponent (α = 0.80) compared to wood (α ≈ 1.0). Functionally similar organs (e.g., leaf-bark in photosynthesis, wood–root in transport) showed isometric N and P allocation (α ≈ 1.0), whereas functionally divergent organs (e.g., leaf–root) followed an allometric scaling relationship (α < 1.0), aligning with the functional similarity rule. Compared to deciduous species, evergreen species exhibited greater stoichiometric homeostasis, higher network edge density (0.61 vs. 0.25; indicating stronger resource integration), and reduced modularity (0.09 vs. 0.31; reflecting functional interdependence rather than division). Our findings demonstrate that evergreen and deciduous species adopt divergent strategies through homeostasis and network structure differentiation, and highlight the need to refine ecosystem models by incorporating bark–wood differentiated N–P allocation mechanisms.