Responses of ecosystem carbon dioxide fluxes to soil moisture fluctuations in a moist Kenyan savanna

Abstract

Measurements were conducted within a fence-exclosure between February 2008 and July 2009 to investigate the influence of soil moisture on ecosystem CO₂ fluxes in a Themeda triandra-dominated grassland of a humid Kenyan savanna. Rainout shelters were constructed to reduce ambient rainfall by 0%, 10% and 20% respectively to attain variable soil water content (SWC) during plant growth. SWC within the top 30 cm layer, above-ground biomass, soil and plant nitrogen (N) concentrations were assessed monthly alongside CO₂ fluxes. Net ecosystem CO₂ exchange (NEE) and ecosystem respiration (R eco ) were measured with closed chambers while carbon (C) partitioning during the wet and dry seasons were assessed through pulse ¹³C labelling. There were significant seasonal and between plot differences in SWC, above-ground biomass, canopy light utilization efficiency (α), CO₂ …