Soil Carbon and Nitrogen Isotopic Responses to Fire, Chronic Herbivory, and Seasonal Flooding in Savannas using Gorongosa National Park as a Model System

Abstract

C:N ratios, δ15N, and δ13C from two distinct plot types in Gorongosa National Park (GNP) were used to gain an understanding of soil nutrient cycling in response to various environmental disturbances. GNP is a savanna ecosystem that experiences fire, chronic herbivory, and seasonal flooding, all of which are known to have varying effects on soil nutrient cycling and composition. This study focuses on carbon-nitrogen cycle coupling, as nitrogen is the limiting factor in savannas and reduces carbon fixation. It also seeks to add to current literature pertaining to the importance of savannas as a significant carbon sink. It was found that δ15N and C:N ratios have more significant relationships to the disturbance effects when compared to δ13C. This supports that nitrogen is one of the main limiting factors in savanna ecosystems and provides empirical evidence for the importance of using models that account for both nutrients when understanding soil nutrient cycling. The lack of significant change for δ13C also supports the potential of savannas to be a key global carbon sink as the effects of global temperatures rise. Ultimately, this study seeks to add to existing literature on the importance of soil nutrient cycling in savanna ecosystems in relation to their potential as a major carbon sink.