Climate Warming Alters Nutrient Cycling and its Constraint on CO2 Fertilization in Global Forests

Abstract

Purpose of Review

Climate warming affects both nutrient availability and plant nutrient requirements, with a potential alteration of nutrient limitation to the CO₂ fertilization effect on net primary productivity (NPP) and carbon (C) sinks, but the overall impact remains poorly understood. Based on a literature review, we synthesized the current understanding of climate warming-induced changes in (i) availability, (ii) demands, and (iii) limitation of the nutrients nitrogen (N) and phosphorus (P) in global forest biomes as well as (iv) how climate warming alters nutrient constraints on CO₂ fertilization.

Recent Findings

Climate warming generally increases nutrient availability via accelerating nutrient cycling but this effect largely varies between different forest biomes, resulting in a considerable increase in N availability in temperate and boreal forests but a weak P availability increase in tropical forests due to a depleted soil P pool. Climate warming likely causes an increase of NPP and nutrient demands in thermal-limited boreal and temperate forests, but it can result in a reduction of growth and nutrient demand in forests with an exceedance of optimal growth temperatures (e.g. some of tropical forests) and/or warming-induced moisture deficiency. Overall, climate warming tends to alleviate N limitation in boreal and temperate forests to support NPP in response to rising CO₂ concentrations. In contrast, climate warming combined with CO₂ fertilization will likely strengthen P limitation in tropical forests.

Summary

Warming-induced changes in nutrient limitation can lead to biome-specific responses of NPP to rising atmospheric CO₂ concentrations. Our review highlights the role of climate warming-induced changes in nutrient availability, demand, and limitation in constraining biogeochemical feedback to future CO₂ enrichment.