中国土壤容重特征及其对区域碳贮量估算的意义

容重是土壤最重要的物理性质之一,不仅能反映土壤质量和土壤生产力水平,还是区域尺度土壤碳贮量估算的重要参数。由于野外测定土壤容重费时费力、并且操作过程也容易造成较大的误差,因此,土壤容重在国内外大多数清查数据库中均缺失严重。通过收集和整理中国第二次土壤普查数据、中国生态系统研究网络数据和1980—2014年论文内的中国土壤容重数据(共11845条记录),系统地探讨了中国陆地生态系统土壤容重的整体分布特征、垂直分布特征以及不同土壤类型间的差异。分析结果表明:中国陆地生态系统的土壤容重数据整体呈正态分布,平均值为(1.32±0.21)g/cm~3,中值为1.35g/cm~3;土壤容重随土层深度增加而增加,两者间表现为显著的幂函数关系。土壤容重与有机质含量呈显著的正相关关系,与沙粒含量的负相关关系较弱。此外,不同土壤类型间的土壤容重差异较大,高山土平均容重最低(0.93 g/cm~3),而盐碱土平均容重最高(1.41 g/cm~3)。结果全面阐释了中国陆地生态系统土壤容重的基本特征及其变异规律,其结论还将为准确评估区域乃至全国土壤碳贮量提供重要参数。

Evaluation of soil bulk density in Chinese terrestrial ecosystems for determination of soil carbon storage on a regional scale

Soil bulk density (BD, g/cm³) is one of most important properties of soil. BD can be used to characterize the conditions of soil quality and soil productivity and is an important parameter used for estimation of soil carbon storage within a plot or on regional and national scales. In practice, the common methods used to measure BD in the field are laborious and expensive, particularly for deeper soil layers. Moreover, it is difficult to control the quality of BD data when classical protocols utilizing soil cores are used. Therefore, large-scale field investigations of BD have not been conducted, resulting in a deficiency of BD data in databases in China and other countries. In this study, we collected BD data (11845 records) for Chinese terrestrial ecosystems from sources including the database of China''s Second National Soil Survey, the database of the Chinese Ecosystem Research Network, and public publications from 1980 to 2014 in order to explore the properties of BD on a national scale and to identify general changes in BD with soil depth and types. The results showed that the reported BD data in China were normally distributed across all soil types and at different soil depths. The mean and median values of BD were (1.32±0.21) g/cm³ and 1.35 g/cm³, respectively. BD increased with increasing soil depth along the soil profile, which could be well depicted by power functions. There was a significant positive correlation between BD and soil organic matter content and a weak negative correlation between BD and sand content. Furthermore, the values of BD seemed to vary among different soil types, and the mean values of BD ranged from 0.93 g/cm³ (alpine soil) to 1.41 g cm^-3 (alkali-saline soil). In summary, our study demonstrated the patterns of BD distribution among different soil depths and types on a national scale, and the findings may be used to estimate soil carbon storage both regionally and nationally.