Chemodiversity of Soil Dissolved Organic Matter and Its Association With Soil Microbial Communities Along a Chronosequence of Chinese Fir Monoculture Plantations

Abstract

The total dissolved organic matter (DOM) content of soil changes after vegetation transformation, but the diversity of the underlying chemical composition has not been explored in detail. Characterizing the molecular diversity of DOM and its fate enables a better understanding of the soil quality of monoculture forest plantations. This study characterized the chemodiversity of soil DOM, assessed the variation of the soil microbial community composition, and identified specific linkages between DOM molecules and microbial community composition in soil samples from a 100-year chronosequence of Chinese fir monoculture plantations. With increasing plantation age, soil total carbon and dissolved organic carbon first decreased and then increased, while soil nutrients, such as available potassium and phosphorus and total nitrogen, potassium, and phosphorus, increased significantly. Lignin/carboxylic-rich alicyclic molecule (CRAM)-like structures accounted for the largest proportion of DOM, while aliphatic/proteins and carbohydrates showed a decreasing trend along the chronosequence. DOM high in H/C (such as lipids and aliphatic/proteins) degraded preferentially, while low-H/C DOM (such as lignin/CRAM-like structures and tannins) showed recalcitrance during stand development. Soil bacterial richness and diversity increased significantly as stand age increased, while soil fungal diversity tended to increase during early stand development and then decrease. The soil microbial community had a complex connectivity and strong interaction with DOM during stand development. Most bacterial phyla, such as Acidobacteria, Chloroflexi, and Firmicutes, were very significantly and positively correlated with DOM molecules. However, Verrucomicrobia and almost all fungi, such as Basidiomycota and Ascomycota, were significantly negatively correlated with DOM molecules. Overall, the community of soil microorganisms interacted closely with the compositional variability of DOM in the monoculture plantations investigated, both by producing and consuming DOM. This suggests that DOM is not intrinsically recalcitrant but instead persists in soils as a result of simultaneous consumption, transformation, and formation by soil microorganisms with extended stand ages of Chinese fir plantations.

Chemodiversity of Dissolved Organic Matter Is Governed by Microbial Biogeography in Inland Waters

“…DOM chemical composition will be determined by their sources and subsequent processing. Lignin is an important organic composition of terrestrial vascular plants and an ideal biomarker for terrestrial organic matter. , In the sediments rather than the waters, lignin being the main DOM component means that terrestrial plant debris moved into water is stored in the sediment after continuous degradation, as lignin is generally difficult to be degraded by microorganisms . Phytoplankton are an important primary producer assimilating inorganic nutrients and can release DOM through cell autolysis and/or exudation of metabolites .…”

“…5,47 In the sediments rather than the waters, lignin being the main DOM component means that terrestrial plant debris moved into water is stored in the sediment after continuous degradation, as lignin is generally difficult to be degraded by microorganisms. 48 Phytoplankton are an important primary producer assimilating inorganic nutrients and can release DOM through cell autolysis and/or exudation of metabolites. 49 An increase in WT can enhance phytoplankton growth, 28 and phytoplankton consume CO 2 and release O 2 by photosynthesis, resulting in an increase in water pH and DO.…”

Phototrophic Biofilms Transform Soil-Dissolved Organic Matter Similarly Despite Compositional and Environmental Differences

“…3 Because of its high water solubility and relatively low molecular weight, DOM is the most chemically and biologically active component of soil organic matter (SOM). 4 DOM changes dynamically in soil; for instance, it can be consumed by soil microbes and be continuously produced via leaching, microbial decay of humus, and desorption from minerals. 1,5 Different soils can vary greatly in DOM composition and thus in its chemical and biological activities.…”

“…In soil, dissolved organic matter (DOM) plays crucial roles in biogeochemical cycling of carbon and nutrients, sustaining agricultural production, and supporting microbial metabolism. , Soil DOM originates from all of plant litter, soil humus, microbial biomass, and root exudates . Because of its high water solubility and relatively low molecular weight, DOM is the most chemically and biologically active component of soil organic matter (SOM) . DOM changes dynamically in soil; for instance, it can be consumed by soil microbes and be continuously produced via leaching, microbial decay of humus, and desorption from minerals. , …”

Root system-rhizosphere soil-bulk soil interactions in different Chinese fir clones based on fungi community diversity change

“…Hook.) is the most common fast-growing timber species in subtropical China, with good material and high yield per unit area (Li Y. et al, 2021); however, the management mode of continuous planting of Chinese fir plantations for multiple generations has significantly reduced the availability of soil nutrients, and the productivity of stands was difficult to maintain for a long time (Farooq et al, 2019a). However, with the maturing of Chinese fir breeding technology, excellent breeding clones have become the main means of afforestation of Chinese fir plantation.…”