Linking nitrogen and water – spatiotemporally optimizing forest fertilization for balancing forest productivity and ecosystem services

Nitrogen fertilization in productive forests is one of the most profitable measures to increase forest growth in Sweden. Fertilization can cause profoundly negative impacts on other ecosystem services, however.

An advanced management tool is required to minimize the negative impacts.The growth response to nitrogen fertilization varies significantly with soil water availability.

Yet, the interactive effects of soil nitrogen and water status are poorly understood, and thus the feedback mechanisms are largely ignored in current models.In this project, I aim to develop a new mechanistic module of the interactive effects of soil nitrogen and water status, and trees´ water-use on forest nutrition and production, and incorporate the new module in a widely used ecosystem production model, 3-PG (Landsberg & Waring 1997).For this, I will use a novel soil monitoring system in combination with advanced stable isotope technique.

The planned controlled laboratory and the manipulative field experiments will provide empirical datasets with unprecedented resolution to construct and validate a new mechanistic module.Subsequent development of the 3-PG model by incorporating the new module will substantially enhance abilities to spatiotemporally optimize forest fertilization to meet nutrient requirements under given soil and climate conditions, thereby reducing overfertilization, inefficient fertilizer use, and impact on downstream water quality, while sustaining optimal forest productivity.