Uncertainties arising from the so-far poorly explained spatial variability of soil respiration (R_s) remain large. This is partly due to the limited understanding about how spatially variable R_s actually is, but also on how environmental controls determine R_s's spatial variability and how these controls vary in time (e.g., seasonally). Our study was designed to look more deeply into the complexity of R_s's spatial variability in a European beech even-aged stand, covering both phenologically and climatically contrasting periods (spring, summer, autumn and winter). Although we studied a relatively homogeneous stand, we found a large spatial variability of R_s (coefficients of variation > 30%) characterized by strong seasonality. This large spatial variability of R_s suggests that even in relatively homogeneous stands there is a large potential source of error when estimating R_s. This was also reflected by the sampling effort needed to obtain seasonally robust estimates of R_s, which may actually require a number of samples above that used in R_s studies. We further postulate that the effect of seasonality on the spatial variability and environmental controls of R_s was determined by the seasonal shifts of its microclimatic controls: during winter, low temperatures constrain plant and soil metabolic activities and hence reduce R_s variability (temperature-controlled processes), whereas during summer, water demand by vegetation and changes in water availability due to the microtopography of the terrain (i.e., slope) increase R_s variability (water-controlled processes). This study provides novel information on the spatiotemporal variability of R_s and looks more deeply into the seasonality of its environmental controls and the architecture of their causal-effect relationships controlling R_s's spatial variability. Our study further shows that improving current estimates of R_s at local and regional levels might be necessary in order to reduce uncertainties and improve CO₂ estimates at larger spatial scales.

中文翻译：

---

欧洲山毛榉（Fagus sylvatica L.）林分中土壤呼吸（Rs）的空间变异性及其控制受到强烈的季节性影响

迄今为止，由于土壤呼吸（R _s）的空间变异性解释不充分而产生的不确定性仍然很大。这部分是由于对 R _s实际上如何空间变量的理解有限，而且还由于环境控制如何确定 R _s的空间可变性以及这些控制如何随时间变化（例如，季节性）。我们的研究旨在更深入地研究欧洲山毛榉平均年龄林分中 R _s空间变异的复杂性，涵盖物候和气候对比时期（春季、夏季、秋季和冬季）。虽然我们研究了一个相对同质的林分，但我们发现 R _{s 的}空间变异很大（变异系数 > 30%）具有很强的季节性。R _{s 的}这种大空间变异性表明，即使在相对均匀的林分中，估计 R _s时也存在很大的潜在误差源。这也反映在获得 R _{s 的}季节性稳健估计值所需的抽样工作上，这实际上可能需要比 R _s研究中使用的更多样本。我们进一步假设季节性对 R _s的空间变异性和环境控制的影响取决于其小气候控制的季节性变化：在冬季，低温限制了植物和土壤的代谢活动，从而降低了 R _s变异性（温度控制过程），而在夏季，植被对水的需求以及地形（即坡度）的微地形引起_的可用水量变化增加了 R _s变异性（水控制过程）。这项研究提供了关于R的时空变异特征的新型信息_小号，并期待更深入地进入其环境控制的季节性和其因果因果关系使R的结构_小号的空间变异。我们的研究进一步表明，为了减少不确定性并改进更大空间尺度上的CO ₂估计值，可能有必要在地方和区域层面改进当前对 R _{s 的}估计。