Abstract. Soil respiration (R_s) is an important carbon flux in terrestrial ecosystems and knowledge about this CO₂ release process and the drivers involved is a key topic in the context of global change. However, temporal, and spatial variability has not been extensively studied in semiarid systems such as olive groves. In this study, we show a full year of continuous measurements of R_s with six automatic chambers in a fertirrigated olive grove with bare soil in the Mediterranean accompanied by ecosystem respiration (R_eco) obtained using the eddy covariance (EC) technique. To study spatial variability, the automatic chambers were distributed equally under the canopy (R_{s Under-Tree}) and in the center of the alley (R_{s Alley}), and the gradient of R_s between both locations was measured in several manual campaigns in addition to azimuthal changes about the center of the olive trees. The results indicate that R_{s Under-Tree} was three times larger than R_{s Alley} in the annual computations. Higher R_s was found on the south face, and an exponential decay of R_s was observed until the alley's center was reached. These spatial changes were used to weigh and project R_s to the ecosystem scale, whose annual balance was 1.6–2.3 higher than R_eco estimated using EC-derived models. The daytime R_eco model performs better the greater the influence of R_{s Under-Tree} and the night-time R_eco model and R_s covaried more the higher the fraction of R_{s Alley}. We found values of Q₁₀ < 1 in the vicinity of the olive tree and R_{s Under-Tree} represented 39 % of the R_s of the olive grove. CO₂ pulses associated with precipitation events were detected, especially in the alley, during dry periods, and after extended periods without rain, but were not accurately detected by EC-derived models. We point out an interaction between several effects that vary in time and are different under the canopy than in the alleys that the accepted models to estimate Q₁₀ and R_eco do not consider. These results show a high spatial and temporal heterogeneity in soil respiration and the factors involved, which must be considered in future work in semi-arid agrosystems.

中文翻译：

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地中海裸土橄榄树林土壤呼吸的时空异质性

摘要。土壤呼吸 (R _s ) 是陆地生态系统中重要的碳通量，了解这种 CO ₂释放过程及其相关驱动因素是全球变化背景下的一个关键话题。然而，半干旱系统（如橄榄园）的时间和空间变化尚未得到广泛研究。在这项研究中，我们展示了地中海裸露土壤的施肥橄榄园中六个自动室对R _s的全年连续测量，以及使用涡流协方差 (EC) 技术获得的生态系统呼吸 (R _eco )。为了研究空间变异性，自动室均匀分布在树冠下（R _{s Under-Tree}）和小巷中心（R _{s Alley} ），并且在几个手动活动中测量了两个位置之间的R _s梯度除了橄榄树中心的方位角变化之外。结果表明，在年度计算中， R _{s Under-Tree是 R s Alley 的}三倍。在南面发现了较高的 R _{s ，并且观察到 R s}呈指数衰减，直到到达小巷的中心。这些空间变化被用来权衡 R 并将_其投影到生态系统规模，其年余额比使用 EC 衍生模型估计的R _eco高 1.6-2.3 。 R _{s Under-Tree}的影响越大，白天的 R _{eco模型表现越好；R s Alley}的比例越高，夜间 R _eco模型和 R _s协变越多。我们发现橄榄树附近的Q ₁₀ < 1值，_{树下的 R s}代表橄榄树林R _s的 39%。检测到与降水事件相关的CO ₂脉冲，特别是在小巷中、干旱时期以及长时间无雨后，但EC衍生模型未能准确检测到。我们指出几种影响之间的相互作用，这些影响随时间变化，并且在树冠下与在小巷中不同，而公认的估计 Q ₁₀和 R _{eco 的}模型没有考虑到这些影响。这些结果表明土壤呼吸及其相关因素具有高度的空间和时间异质性，在半干旱农业系统的未来工作中必须考虑这一点。