Multiple scales of spatial heterogeneity control soil respiration responses to precipitation across a dryland rainfall gradient

Aims Soil respiration (R s ) is a major pathway for carbon release to the atmosphere. We explored variability in dryland R s response to rainfall pulses at multiple levels of spatial heterogeneity: 1) along a hyper-arid to arid rainfall gradient, 2) across soil surfaces that differ in stability and composition, and 3) among different geomorphic and vegetation patch types. Methods We measured in situ R s responses for 48 h following simulated rainfall pulses in the Namib Desert. Working across the rainfall gradient, we compared R s responses on two soil surfaces. Each soil surface had two vegetation/geomorphic patch types that differed in organic matter sources and transport processes, with one characterized by depositional inputs and one characterized by erosional losses. Results Soil respiration was highly responsive to rainfall pulses, although soil surfaces and patch types often exerted more control on R s than did rainfall pulses. Rainfall generally had proportionally greater influence on R s with higher annual rainfall. Greater R s occurred on stable than unstable soil surfaces and in depositional than erosional patch types. Conclusions Large differences in R s among rainfall zones, soil surfaces, and patch types point to the need to carefully consider multiple scales of spatial heterogeneity when interpreting dryland biogeochemical fluxes.