Vegetation patch type has a greater influence on soil respiration than does fire history on soil respiration in an arid broadleaf savanna woodland, central Namibia

Soil respiration is a critical pathway in the carbon cycle, accounting for a major flux of carbon from the biosphere to the atmosphere. However, controls over soil respiration are poorly understood in drylands. Fire is prevalent in many drylands, potentially causing both direct and indirect changes in soil respiration through altering vegetation patterns, soil organic matter, and microclimate. We investigated the independent and interactive effects of fire history (management units burned 2, 3, 15 and 25 years ago) and patch type (bare, grass and shrub) on soil respiration in an arid broadleaf savanna, central Namibia. Soil respiration was measured in situ and in a lab incubation during both wet and dry time period. Fire history showed a limited and inconsistent impact on soil respiration, while soil respiration was highly responsive to vegetation patch types. Soil under shrubs generally had highest respiration rates in the in situ study, but a lack of patch effects in the lab incubations suggest that vegetation patch effects may have been largely attributed to root respiration. These results suggest that fire indirectly affects soil respiration if it alters the distribution of vegetation patch types.