The importance of non-carbonate mineral weathering as a soil formation mechanism within a karst weathering profile in the SPECTRA Critical Zone Observatory, Guizhou Province, China

Abstract

Soil degradation, including rocky desertification, of the karst regions in China is severe. Karst landscapes are especially sensitive to soil degradation as carbonate rocks are nutrient-poor and easily eroded. Understanding the balance between soil formation and soil erosion is critical for long-term soil sustainability, yet little is known about the initial soil forming processes on karst terrain. Herein we examine the initial weathering processes of several types of carbonate bedrock containing varying amounts of non-carbonate minerals in the SPECTRA Critical Zone Observatory, Guizhou Province, Southwest China. We compared the weathering mechanisms of the bedrock to the mass transfer of mineral nutrients in a soil profile developed on these rocks and found that soil formation and nutrient contents are strongly dependent upon the weathering of interbedded layers of more silicate-rich bedrock (marls). Atmospheric inputs from dust were also detected.

Mineralisation of atmospheric CO2 in hydromagnesite in ultramafic mine tailings – Insights from Mg isotopes

“…Tipper et al, 2006;Pogge von Strandmann et al, 2008). This is consistent with simple isotope mass balance considerations that dictate that Mg isotopes are not fractionated during complete dissolution of minerals, such as expected for weathering of magnesite or brucite (Mumpton and Thompson, 1966;Moore et al, 2017). Accordingly, measurable suggest that some of the above alteration products can form at near-ambient temperatures (De Obeso et al, 2020;Streit et al, 2012).…”

Soil functions and ecosystem services research in the Chinese karst Critical Zone

“…They correlated these contents with mineral and elemental contents in the overlying soils to conclude that the soils were formed from the bedrock impurities and not via deposition of transported material. Non-carbonate mineral contents can vary even within a single outcrop as observed by Moore et al (2017) who found adjacent beds in Puding County, Guizhou, with 4, 25, and 33% non-carbonate mineral contents. Based on the abundances of non-carbonate (largely silicate) mineral impurities in the bedrock of the karst…”

“…The substantial rainfall of the sub-tropical monsoonal climate of southwest China promotes rapid carbonation (although higher temperatures will slow the rate as carbon dioxide (CO2) is less soluble at higher temperatures), and subsequently, only minimal amounts of undissolved mineral particles are available for soil formation in karstic systems of the region. Therefore, in the absence of aeolian deposition, soil formation in karst areas depends on "impurities" within the bedrock, predominantly silicate minerals, which provide both a structural matrix and additional elements, many of which are essential macroand micro-nutrients (Wang et al 1999;Moore et al 2017). Wang et al (1999) examined bedrock from five sites across Guizhou and Hunan provinces and found 11.6 -38.8% noncarbonate residual mineral content in the limestones and 0.6 -4.0% residual content in the dolostones.…”

Analysing and simulating spatial patterns of crop yield in Guizhou Province based on artificial neural networks

“…They are characterized by exposed carbonate rocks that weather rapidly and are highly susceptible to environmental change and natural erosion. In China, the karst landscape in the southwest region has experienced rapid and intensive alterations to land use and associated ecosystem degradation over the last 50 years (Chen et al, 2018; Li et al, 2018; Moore et al, 2017). The intensification of agriculture since the late twentieth century has led to a rapid deterioration of the soil, reflected in reduced crop production and the rapid loss of soil (Green et al, 2019).…”