Water-extractable organic matter (WEOM) drives many fundamental functions which determine soil equilibria, acting as a useful probe to highlight the effect of land management on overall C cycling. The ecological importance of WEOM is emphasized in tropical environments characterized by humid climate and short OC turnover. The low OC concentration and the physical–chemical conditions associated to water dissolved compounds determine an analytical issue for the characterization of WEOM. The present experiment aimed to test the diffuse reflectance infrared Fourier transformation (DRIFT) spectroscopy as a rapid tool to evaluate the dynamic of WEOM in tropical soils under different soil organic matter (SOM) managements. The influence of SOM composition on WEOM fraction was evaluated in a laboratory incubation of two tropical soils treated with different organic amendments. The superficial layers of forest and sugarcane Ultisol were incubated for 1 year with 10 mg C g⁻¹ soil of litter from either native tropical forest or sugarcane crop residues. The sugarcane residues promoted a fast increase of dissolved organic carbon (DOC) followed by a subsequent decrease in both soils, whereas the soils amended with forest litter showed DOC dynamics similar to control samples. The DRIFT analysis unveiled changes in the chemical profile of WEOM mainly reflected on the preservation of dissolved hydrophobic compounds. The results indicate the DRIFT technique as an efficient tool to monitor the chemical changes of WEOM f as related to soil use and organic inputs, and to support a comprehensive understanding of the interaction of WEOM in agro-ecological and environmental processes.

中文翻译：

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漂移光谱技术检测到的热带森林和农业土壤中水可提取有机质的变化

水可提取有机质 (WEOM) 驱动着许多决定土壤平衡的基本功能，可作为一种有用的探针来突出土地管理对整体碳循环的影响。WEOM 的生态重要性在以潮湿气候和 OC 周转时间短为特征的热带环境中得到强调。与水溶解化合物相关的低 OC 浓度和物理化学条件决定了 WEOM 表征的分析问题。本实验旨在测试漫反射红外傅里叶变换 (DRIFT) 光谱作为评估不同土壤有机质 (SOM) 管理下热带土壤中 WEOM 动态的快速工具。在用不同有机改良剂处理的两种热带土壤的实验室培养中评估了 SOM 组成对 WEOM 分数的影响。森林和甘蔗 Ultisol 的表层用 10 mg C g 孵育 1 年⁻¹来自原生热带森林或甘蔗作物残留物的凋落物土壤。甘蔗残留促进溶解有机碳 (DOC) 的快速增加，随后两种土壤中的溶解有机碳随后减少，而用森林凋落物修正的土壤显示出与对照样品相似的 DOC 动态。DRIFT 分析揭示了 WEOM 化学特征的变化，主要反映在溶解的疏水化合物的保存上。结果表明，漂移技术是监测 WEOM f 与土壤利用和有机投入相关的化学变化的有效工具，并支持全面了解 WEOM 在农业生态和环境过程中的相互作用。