Soil resource acquisition strategy modulates global plant nutrient and water economics

Natural selection favors growth by selecting a combination of plant traits that maximize photosynthetic CO2 assimilation at the lowest combined carbon costs of resource acquisition and use. We quantified how soil nutrient availability, plant nutrient acquisition strategies, and aridity modulate the variability in plant costs of nutrient acquisition relative to water acquisition (beta). We used an eco-evolutionary optimality framework and a global carbon isotope dataset to quantify beta. Under low soil nitrogen-to-carbon (N : C) ratios, a mining strategy (symbioses with ectomycorrhizal and ericoid mycorrhizal fungi) reduced beta by mining organic nitrogen, compared with a scavenging strategy (symbioses with arbuscular mycorrhizal fungi). Conversely, under high N : C ratios, scavenging strategies reduced beta by effectively scavenging soluble nitrogen, compared with mining strategies. N2-fixing plants did not exhibit reduced beta under low N : C ratios compared with non-N2-fixing plants. Moisture increased beta only in plants using a scavenging strategy, reflecting direct impacts of aridity on the carbon costs of maintaining transpiration in these plants. Nitrogen and phosphorus colimitation further modulated beta. Our findings provide a framework for simulating the variability of plant economics due to plant nutrient acquisition strategies in earth system models.