Spectral Characteristics and Driving Factors Analysis of Soil Dissolved Organic Matter in Different Forest Types in Ziwuling Forest District
MENG Yong-xia1, 2, LI Peng1, 2*, XIAO Lie1, 2, ZHANG Chao-ya1, 2, YANG Shu-tong1, 2, LIU Jia-liang1, 2
1. Hydrological and Water Resources System, School of Water Resources and Hydropower, Xi'an University of Technology, Xi'an 710048, China
2. State Key Laboratory of Eco-Hydraulics in Northwest Arid Region of China, Xi'an University of Technology, Xi'an 710048, China
Abstract：Dissolved organic matter (DOM) is an important parameter reflecting forest soil's carbon and nutrient cycles. Therefore, describing the composition and structure of DOM from different forest types and soil depths is particularly important for understanding the forest carbon cycling process. This study used a combined method of three-dimensional fluorescence excitation-emission matrix (EEM) and parallel factor analysis (PARAFAC) to analyze the variation characteristics of DOM in Pinus tabuliformis forest (YS) and Quercus acuteserrata forest (ML) at 0～20, 20～60, and 60～100 cm. The average content of dissolved organic carbon (DOC) was higher in ML forest land, while it was lower in YS forest land and varied significantly with changes in soil depth. Four fluorescent components were identified using PARAFAC, among which C1 and C2 are humic and fulvic acid components, belonging to the humic-like fluorescence component. They are mainly concentrated in the 0～20 cm and gradually decrease with increasing soil depth. C3 and C4 are tryptophan and tyrosine-like components, respectively, belonging to the protein-like fluorescence component, and their proportion increases with increasing soil depth. Fluorescence parameter indices of soil profiles indicated that the dominant source of DOM in the 0～20 cm depth was primarily from terrestrial inputs, while in the 60～100 cm depth, it was mainly derived from autochthonous sources caused by microbial activities. Correlation analysis showed significant correlations between two forest stands' DOC and four soil enzymes. Additionally, in the YS soil, DOC was significantly positively correlated with TN (p<0.05), whereas in the ML soil, DOC was highly significantly positively correlated with TP (p<0.01). The results of the Partial Least Squares Path Modeling (PLS-PM) indicated that both physicochemical properties and soil enzymes could independently dominate DOM and interact to influence DOM. These results contribute to understanding the dynamic characteristics of soil DOM in the soil profile of Pinus tabuliformis and Quercus acuteserrata forests, and their influencing factors. These results contribute to understanding the dynamics of soil DOM in the Ziwuling region's Pinus tabulaeformis and Quercus acuteserrata forests, providing theoretical insights into carbon cycling in forest ecosystems.
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