Soil-atmosphere terpene exchanges in the tropical forest of French Guiana with nitrogen and phosphorus fertilizer application

Abstract

Background and aims Tropical forest soils can act as sources or sinks of biogenic volatile organic compounds (BVOCs), especially terpenes, yet the impact of long-term nutrient deposition on these fluxes remains unclear. We aimed to assess how nitrogen (N), phosphorus (P), and combined (NP) fertilization affect soil-atmosphere terpene exchanges across seasons and topographical gradients in a tropical forest in French Guiana.

Methods We measured net exchange rates of terpenes using dynamic chambers in control and fertilized plots after three years of nutrient addition. Treatments were compared across wet and dry seasons, topographic positions, and under conditions with and without litter.

Results Soil exhibited both emission and uptake of terpenes, with marked seasonal patterns. Emissions peaked during the wet season, while uptake was more frequent during the dry season. N fertilization significantly increased monoterpene emissions from litter-covered soils in the wet season and reduced terpene uptake in the dry season. P fertilization weakened monoterpene uptake during the dry season but had limited effects on emissions. Combined NP treatment enhanced overall terpene exchange rates. Topography and litter presence modulated these effects but did not override the dominant influence of fertilization and season.

Conclusions Nutrient enrichment alters the magnitude and direction of soil terpene fluxes in tropical forests, with implications for ecosystem functioning and atmospheric chemistry. Our findings underscore the need to incorporate soil BVOC dynamics into models predicting biogeochemical responses to global change.