Environmental controls on soil respiration across a southern US climate gradient: a meta-analysis

• Identifying controls on soil respiration can improve understanding of soil C cycling.
• Physiographic region and soil moisture regime effect soil respiration.
• Numerous similarities among multiple regression model coefficient estimates were identified.
• Moisture regime within region affected relationships explaining soil respiration.

Carbon (C) cycling in the soil is intimately associated with soil respiration as organic matter is decomposed by microbes. Consequently, soil C stocks and sequestration potential are also intimately associated with soil respiration. Although many soils of the southern and southeastern United States (US) are generally more weathered and contain less C than those of the upper Midwest due to moist, and generally warmer climatic conditions, their soil C sequestration potential may be greater due to their ability to produce biomass year-round, which, in turn, results in greater C inputs. Identifying influential environmental factors that control soil respiration across a large geographic area and climate gradient can improve understanding of soil C sequestration potential in the southern US. The objectives of this study were to evaluate the effects of i) physiographic region (i.e., Arkansas Ozark Highlands, Arkansas Delta, and Florida Flatwoods) and ii) soil moisture regime (i.e., udic and aquic) on the relationship among soil respiration and combined soil moisture and soil temperature related environmental parameters. Despite some expected differences and generally low model predictiveness (R2 < 0.4), results showed numerous similarities among multiple regression model coefficient estimates across widely differing physiographic regions along a southern climate gradient. Results also showed the relationship among soil respiration and soil moisture and soil temperature related environmental parameters differed (P < 0.05) between soil moisture regimes within regions. Improving the ability to predict soil respiration from directly measured and/or indirectly calculated environmental parameters will increase the understanding of factors controlling soil C sequestration, and potential agronomic and ecological sustainability, in the weathered soils of the southern and southeastern US.