Differential Effects of Nitrogen, Phosphorus and Potassium Soil Enrichment on Mycorrhization, Nutritional Status and Nutrient Resorption in Nothofagus Antarctica

Abstract

To understand how changing environmental conditions affect forest ecosystems it is crucial to explore how soil nutrient availability influences plant nutrient dynamics. However, it remains unclear the extent to which the availability of various nutrients in the soil jointly influences the dynamics of plant nutrition, including nutrient acquisition strategies (e.g., reliance on mycorrhizal symbiosis), nutritional status, and nutrient resorption during senescence. We investigated the interactive effects of N, P, and K soil enrichment on the nutritional dynamics of Nothofagus antarctica using a factorial design. The experiment included 32 plots with eight fertilization treatments (N, P, K, NP, NK, PK, NPK, and control) across four blocks. We collected root samples to measure mycorrhizal colonization, and leaf samples for specific leaf area (SLA), nutrient content, resorption efficiency and proficiency. Fertilization increased soil nutrient availability, and decreased mycorrhizal colonization. This suggests that plants may no longer need to invest in mycorrhizas, as nutrients are more readily accessible. Fertilization improved nutritional status and, at senescence, N resorption was reduced by nitrogen addition, but not P and K, indicating that N. antarctica might only be limited by N. Nutrient addition, a predicted consequence of global change, facilitated plants nutrient uptake, either alleviating nutritional needs (N) or promoting luxury consumption (P and K), and disrupted the forest’s mycorrhizal networks. This could potentially disrupt long-term ecosystem services such as carbon sequestration and nutrient cycling. Our results highlight the need for targeted nutrient management strategies in forest ecosystems to mitigate the effects of global change.