Plant nitrogen acquisition strategies impact ecosystem carbon storage under future climate

Abstract. Plant nitrogen (N) use strategies affect ecosystem nutrient cycles and limitation and thereby the response of ecosystems to global change. However, their influence on future projections of nutrient limitation and land carbon (C) sink remains unclear. Here, we used a nitrogen-enabled biosphere model (QUINCY) to evaluate the competitiveness of acquisitive (high uptake, low resorption) and conservative (low uptake, high resorption) N-use strategies within plant functional types (PFTs) and climate zones under a scenario of future climate change (SSP3-7.0). We assessed competitive advantage via net primary productivity (NPP) and implications for C storage and N cycling through total ecosystem C and the ecosystem N uptake/loss ratio. Our results suggest that a broad-leaved deciduous (BDS) conservative strategy has a stronger competitive advantage compared to needle-leaved evergreens (NE) conservative, as shown by the largest relative gains in NPP (+48 %) and Ecosystem C (+22 %) together with smaller increases in N losses (-7.6 %) . This overall response varies across climate zones reflecting the latitudinal gradient in nutrient limitation. In the tropics, where N is generally not a limiting nutrient, acquisitive and conservative N-use respond similarly. In contrast, temperate and boreal regions sustain a clear advantage for conservative strategies, with higher gains in NPP (+24.8 % vs. +18.7 % in temperate BDS; +18.8 % vs. +17.7 % in temperate NE; +41.3 % vs. +30.5 % in boreal BDS; +56.7 % vs. +46.5 % in boreal NE), and consistent patterns for C storage. Together, the findings underscore that the functional N-use strategy diversity within PFTs may influence future C and N projections, and represents a conceptual step toward improving model realism.