Soil organic matter transformation and stabilization depending on vegetation cover

Ing. Saven Thai

Doctoral thesis

Abstract:

The dissertation revealed that SOM and soil chemistry are influenced by vegetation covers and translocate chemical compositions differently through the soil profiles and soil types, even when they grow in the same or similar climate conditions, soil types, and elevations. Forest soil was found to have higher levels of aliphatic and carboxylic groups compared to grassland and cropland. However, the composition of SOM, including aliphatic, carboxylic groups, and polysaccharides, varied at different depths under all land uses. Additionally, the aromatic group was more prevalent in deeper soil layers of cropland in comparison to forestland and grassland, indicating the higher plant residues, SOM and root exudation under forest, while SOM under cropland was rapidly mineralized due to agricultural activities. However, the dissertation indicated that the stabilization of SOM within aggregates depends on the application of organic mulches on the soil. These organic mulches reduce the wettability of the aggregates, thereby protecting them from dispersion with water. On the other hand, in the long term, soil type (i.e., the set of climatic, geological, and geographical conditions) plays an important role in the stabilization and conservation of organic matter in the soil. Organic matter of Chernozems maintains a high proportion of aromatics and in contrast, the proportion of aliphatic components remains high in acid Cambisols even with a similar total C content. Additionally, this study discovered that the temporal changes in chemical composition are influenced by several factors, including the quantity and quality of forest residues, as well as the surrounding environments such as climate conditions, age of the forest, canopy closure, and microbial activities. Besides that, the result revealed that beech forests exhibit greater nutrient recycling, higher low molecular mass organic acids, and more dissolved organic carbon compared to spruce forests due to the presence of decomposable materials and biological activities. Moreover, after the natural beech forest was clear-cut and transformed into a spruce monoculture, the soil chemistry and SOM were pronounced in both organic and mineral horizons have changed and developed podsolization. The study also revealed that DRIFT spectroscopy is a useful method for characterization the composition and decomposition of SOM at different stages and to determine the indices of aromaticity, and wettability within the soil.

Keywords

Drift spectroscopy, Soil organic matter, Land uses, Forest species, Soil types

Language used: English

Date on which the thesis was submitted / produced: 2. 2. 2024

Thesis defence

• Supervisor: doc. Ing. Lenka Pavlů, Ph.D.
• Reader: Vilém Podrázský, CSc., prof. Ing., Lubica Pospíšilová, externi, Jiří Kučerík, externi

Czech University of Life Sciences Prague

Faculty of Agrobiology, Food and Natural Resources

Doctoral programme / field:
Agricultural Specialization / Exploitation and Protection of Natural Resources