Theme
Plenary Session
Speaker
Lindokuhle Xolani Dlamini – University of the Free State
Authors
Lindokuhle Xolani Dlamini – South African Earth Observation Network
Lindokuhle Xolani Dlamini – University of Burgundy
Elmarie Kotze – University of the Free State
Gregor Felg – South African Earth Observation Network
Gregor Felg – University of Pretoria
Olivier Mathieu – University of Burgundy
Abstract
Grasslands are the second largest biome in South Africa and fire plays an important role in grasslands function and management. Approximately 60% of the national carbon (C) stock is found in grasslands, with approximately 90% of the C stock in the soil, primarily in the form of soil organic C. Studies of soil C in South Africa have predominantly been in agricultural systems and generally focus on quantifying total soil C in the topsoil horizon, with less focus on subsoil horizons or soil respiration. The role of fire and the effect of land degradation on C cycling of montane grasslands are largely overlooked, specifically their effects on soil respiration, different C fractions (stable/active) and pyrogenic organic matter. This study investigates the effect of fire, vegetation heterogeneity, and climate variability on soil C dynamics at a catchment scale in a montane fire-climax grassland at Cathedral Peak. Cathedral Peak has rich long-term historical records on climate, fire occurence, and management history. Several experimental catchments have been operational since the 1940s, these include a fire-exclusion (woody plant dominated), a biennial burn, and post afforestation (degraded). Soil respiration is measured using a long-term LI-8100A Automated Soil Gas Flux System (continuous), and soil chamber-based manual technique (sampled monthly). Temperature and soil moisture sensitivity will be recorded and calculated. Soil core samples along a catenal gradient in all three catchments will be collected at regular intervals down to 100 cm. Soil bulk density, soil pH, soil aggregate stability, pyrogenic organic C, 13C and 15N isotopic signatures, soil C and N stocks, and different soil C fractions will be determined. This work will add comprehensive data and insight into soil C dynamics of fire-driven temperate grasslands, contributing immensely to C cycling models globally.