Hi everyone. I am studying the influencing factors of soil organic carbon. In my research, I found that soil water content has a strong correlation with organic carbon content, and plays a very important role in the fitting linear equation. However, the soil water content only represents the soil water condition at the time of sampling, which is affected by climate ( eg. precipitation, temperature) and terrain ( eg. slope , aspect ). This indicates that there may be some uncertainty in the relationship between the single soil moisture content data and the organic carbon content. So how to determine the relationship between soil moisture and organic carbon？
You can conduct a regressinot/correlation analysis on the data you obtained for SOM and SOC and depending R-squared value you determine the extent of relationship
Good question! The study shared by Nagalakshmi Radhakrishnan is very helpful. This study also highlights the importance of soil texture as a control on soil organic carbon content (more clay + silt = more SOC generally). My guess is that your samples' soil moisture differences are also acting as a proxy for differences in soil texture (more clay + silt = higher soil moisture generally). Texture is more of the direct, soil property control on SOC, for which there is a voluminous scientific literature . It's also true, as you suggest, that lower, generally wetter landscape positions may be associated with more SOC: for example, lower landscape positions may be wetter for longer periods in seasonally dry environments, supporting greater primary productivity, which in turn can support higher SOC contents. Conversely, in wetter climates, these lower landscape positions lead to higher SOC often as a result of periods of soil saturation that limit SOC decomposition, supporting higher SOC contents (think wetlands as the extreme case). It's also possible that these lower landscape positions may also have finer textures (more clay + silt) as a result of erosion/deposition, including erosion and deposition of SOC, which will complicate understanding the exact controls (texture vs. moisture vs. terrain features). So, if I were you, I would definitely determine soil texture on my samples, check the level of correlation between texture and moisture, and then begin to figure out how much additional variance can be explained by other terrain features or perhaps indices of vegetative productivity, using a GIS approach, but caution that in this analysis the "controls" on SOC are likely related to one another also.
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