Abstract

The aim of this analytical review is to systematize information on the quantitative characteristics of variation in the content and stock of organic carbon (C_org) in soils. The review considers the estimates for validity and reproducibility of determined C_org values, as well as the spatial variation and heterogeneity of C_org at different hierarchical levels of the soil cover composition and their changes in time. The most powerful factor of C_org changeability in soils is spatial variation. The absolute standard deviation and coefficient of variation for C_org content and stock in soil shows the trend of an increase with the logarithm of the examined plot area. This trend is observed on the background of a wide range of the values of the indicators of spatial C_org variation in each narrow range of the plot area, which leads to a high uncertainty of the estimates with an increase in the area coverage. Direct dry combustion is considered the preferable method among the methods used to determine C_org content. This method gives valid (i.e., with the least biases) and well reproducible data. The indirect Tyurin and Walkley–Black methods systematically underestimate the C_org content and their reproducibility is comparable to the amplitude of seasonal dynamics and minimum spatial variation indices within an elementary soil area. The estimates for the long-term trend of C_org content require strict adherence to stringent monitoring conditions over the time intervals longer than 15 years. The spatial variation in C_org stock is more pronounced as compared with C_org content, which further increases the requirements to monitoring.

中文翻译：

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土壤有机质含量和储量随时间和空间的变化：分析综述

摘要

_{本次分析综述的目的是将土壤中有机碳 (C org} )含量和储量变化的定量特征信息系统化。_{该综述考虑了对所确定的 C org}值的有效性和可重复性的估计，以及不同土壤覆盖成分层次上C _{org的空间变化和异质性及其随时间的变化。土壤中有机质}可变性的最重要因素是空间变化。_{土壤中C org}含量和储量的绝对标准差和变异系数均随受检样地面积的对数呈增加趋势。这种趋势是在图区每个狭窄范围内的空间Corg变化指标值范围广泛的背景下观察到的，这导致随着面积覆盖范围的增加而导致估计的高度不_确定性。直接干燃烧被认为是测定C _org含量的方法中优选的方法。该方法提供有效（即偏差最小）且可重复性良好的数据。间接 Tyurin 和 Walkley-Black 方法系统地低估了 C _org含量，其再现性与基本土壤区域内的季节动态幅度和最小空间变化指数相当。_{对 C org}含量长期趋势的估计需要在超过 15 年的时间间隔内严格遵守严格的监测条件。_与C组织含量相比，C组织存量的空间变化更加明显_，这进一步提高了监测要求。