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.

中文翻译：

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跨旱地降雨梯度的多尺度空间异质性控制土壤呼吸对降水的响应

目的 土壤呼吸 (R s ) 是向大气中释放碳的主要途径。我们在多个空间异质性水平上探索了旱地 R 对降雨脉冲响应的变异性：1）沿着超干旱到干旱的降雨梯度，2）跨越稳定性和成分不同的土壤表面，以及 3）在不同的地貌和植被之间补丁类型。方法 我们在纳米布沙漠模拟降雨脉冲后测量了 48 小时的原位 R s 响应。在整个降雨梯度中，我们比较了两个土壤表面上的 R s 响应。每个土壤表面都有两种植被/地貌斑块类型，它们的有机质来源和运输过程不同，一种以沉积输入为特征，另一种以侵蚀损失为特征。结果土壤呼吸对降雨脉冲高度敏感，尽管土壤表面和斑块类型通常比降雨脉冲对 R s 施加更多的控制。年降雨量越高，降雨量通常对 R s 的影响越大。更大的 R s 发生在稳定的土壤表面而不是不稳定的土壤表面，沉积斑块类型比侵蚀斑块类型。结论 降雨区、土壤表面和斑块类型之间 R s 的巨大差异表明在解释旱地生物地球化学通量时需要仔细考虑空间异质性的多个尺度。