What do relationships between extractable metals and soil organic carbon concentrations mean?
What do relationships between extractable metals and soil organic carbon concentrations mean?
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DOI：
10.1002/saj2.20343
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发表时间：
2022-01-26
影响因子：
2.9
通讯作者：
Thompson, Aaron
中科院分区：
文献类型：
--
作者：
Hall, Steven J.;Thompson, Aaron
含铝(Al)和含铁(Fe)矿物，特别是短程有序相(SRO)被认为保护土壤有机碳(SOC)。然而，评估铝与铁矿物或金属络合物的影响在方法上仍然具有挑战性。虽然SRO的Al相和Fe相有一些共同的性质，但草酸盐溶解的Al(Al-OX)往往比草酸盐溶解的Fe(Fe-OX)或柠檬酸二亚硫酸盐(Fe-Cd)溶解的Fe与SOC有更强的相关性。为了进一步评估这些关系，我们分析了来自国家生态观测网络的一个大型北美土壤数据集。即使排除了富含SRO矿物质的土壤(安迪土和腐殖土)，Al-OX和SOC之间仍然存在很强的关系(而Fe-OX-SOC关系较弱)。草酸盐溶出的Al与柠檬酸盐-二亚硫酸盐可提取铝(Al-Cd；斜率=0.92，R2=0.69)有很强的相关性，其差异可以解释为柠檬酸-二亚硫酸盐对铝取代铁相的溶解较大，而草酸盐对铝硅酸盐的溶解较大(R2=0.87)。草酸盐溶解的铝和Al-Cd都是SOC的强预测因子，尽管它们与硅(Si)的关系不同。草酸盐溶Al与Si-OX强烈协变(R-2=0.79)，而Al-Cd与Si-Cd不一致(R-2=0.18)。Al-OX和Al-Cd与SOC的关系相似，尽管草酸盐和柠檬酸二亚硫酸盐提取的矿物不同，但Al-OC络合物(而不是铝硅酸盐或含铁矿物)是最好的SOC预测因子。这就引出了一些重要的问题：Al-OC复合体是否表明了对分解的保护，或者只是反映了有机酸对矿物风化的更大强度；如果是后者，那么也许SOC输入推动了Al-Ox和SOC的相关性，而不是Al的相组成或丰度。
Aluminum (Al)-bearing and iron (Fe)-bearing minerals, especially short-range-ordered (SRO) phases, are thought to protect soil organic C (SOC). However, it remains methodologically challenging to assess the influence of Al vs. Fe minerals or metal complexes. Whereas SRO Al and Fe phases share some properties, Al dissolved by oxalate (Al-ox) often correlates stronger with SOC than Fe dissolved by oxalate (Fe-ox) or citrate-dithionite (Fe-cd). To further evaluate these relationships, we analyzed a large North American soil dataset from the National Ecological Observatory Network. A strong relationship between Al-ox and SOC (and weaker Fe-ox-SOC relationship) persisted even after excluding soils rich in SRO minerals (Andisols and Spodosols). Al dissolved by oxalate was strongly correlated with citrate-dithionite-extractable Al (Al-cd; slope = 0.92, R-2 = .69), and discrepancies could be explained (R-2 = .87) by greater dissolution of Al-substituted Fe phases by citrate-dithionite and greater dissolution of aluminosilicates by oxalate. Aluminum dissolved by oxalate and Al-cd were both strong SOC predictors despite their differing relationships with silicon (Si). Al dissolved by oxalate and Si-ox strongly covaried (R-2 = .79), but Al-cd was inconsistently related to Si-cd (R-2 = .18). Similar relationships of Al-ox and Al-cd with SOC, despite differences in minerals extracted by oxalate and citrate-dithionite, suggest that Al-OC complexes (as opposed to aluminosilicate or iron-bearing minerals) were the best SOC predictor. This raises important questions: do Al-OC complexes indicate protection from decomposition or simply reflect greater intensity of mineral weathering by organic acids; and, if the latter, then perhaps SOC input is driving Al-ox and SOC correlations rather than Al phase composition or abundance.