Project description:The characteristic of particle size distribution (PSD) in the newly formed wetlands in coast has seldom been studied. We applied fractal-scaling theory in assessing soil particle size distribution (PSD) features of newly formed wetlands in the Yellow River Delta (YRD), China. The singular fractal dimensions (D) values ranged from 1.82 to 1.90, the capacity dimension (D0) values ranged from 0.84 to 0.93, and the entropy dimension (D1) values ranged from 0.66 to 0.84. Constrained corresponding analysis revealed that 43.5% of the variance in soil PSD can be explained by environmental factors, including 14.7% by seasonal variation, 8.6% by soil depth, and 8.0% by vegetation type. The fractal dimensions D and D1 were sensitive with fine particles with size ranging less than 126 μm, and D0 was sensitive with coarse particles with size ranging between 126 μm to 2000 μm. Fractal analysis makes full use of soil PSD information, and offers a useful approach to quantify and assess the soil physical attributes in the newly formed wetland.
Project description:To explore the adaptation of the fine root morphology and chemical characteristics of Tamarix chinensis to water-salt heterogeneity in the groundwater-soil system of a coastal wetland zone, T. chinensis forests at different groundwater levels (high: GW1 0.54 m and GW2 0.83 m; medium: GW3 1.18 m; low: GW4 1.62 m and GW5 2.04 m) in the coastal wetland of the Yellow River Delta were researched, and the fine roots of T. chinensis standard trees were excavated. The fine roots were classified by the Pregitzer method, and the morphology, nutrients, and nonstructural carbohydrate characteristics of each order were determined. The results showed that the groundwater level had a significant indigenous effect on the soil water and salt conditions and affected the fine roots of T. chinensis. At high groundwater levels, the specific root length and specific surface area of fine roots were small, the root tissue density was high, the fine root growth rate was slow, the nutrient use efficiency was higher than at low groundwater levels, and the absorption of water increased with increasing specific surface area. With decreasing groundwater level, the N content and C/N ratio of fine roots first decreased and then increased, and the soluble sugar, starch, and nonstructural carbohydrate content of fine roots first increased and then decreased. At high and low groundwater levels, the metabolism of fine roots of T. chinensis was enhanced, and their adaptability to high salt content and low water content soil environments improved. The first- and second-order fine roots of T. chinensis were mainly responsible for water and nutrient absorption, while the higher-order (from the third to fifth orders) fine roots were primarily responsible for the transportation and storage of carbohydrates. The fine root morphology, nutrients, nonstructural carbohydrate characteristics, and other aspects of the water and salt environment heterogeneity cooperated in a synergistic response and trade-off adjustment.
Project description:Vegetation represents probably the most crucial step for the ecosystem functions of wetlands, but it is unclear how microbial populations and functions shift along with vegetation. In this study, we found that the richness and diversity of soil bacteria increased with vegetation levels and that the community composition was distinctly shifted from bare to vegetative places. The bare land displayed an extremely high abundance of Cyanobacteria as a monospecies genus, while a Gemmatimonadetes genus was predominant as multiple species in all the vegetative wetlands, suggesting their important ecosystem functions and potential mechanisms. Expression of the genes related to photosynthesis was enriched exclusively in bare land. Genes involved in biological organic carbon metabolism and the cycling of main elements (C, N, S, and P) were highly expressed in vegetative wetlands and were mostly included in the metagenome-assembled genome (MAG) of Gemmatimonadetes Some compounds identified from soil metabolomic results also corresponded to pathways involving these key active genes. Cyanobacteria is thus responsible for the carbon sink in early infertile wetlands, and Gemmatimonadetes plays a crucial role in ecosystem functions in vegetative wetlands. Our results highlight that the soil microbial populations execute ecosystem functions for wetlands and that vegetation is the determinant for the population and functional shifts in the coastal estuarine wetland of the Yellow River Delta.IMPORTANCE Vegetation probably represents the most crucial step for the ecosystem functions of wetlands, but it is unclear how microbial populations and functions shift in pace with the colonization and succession of vegetation. In this study, we found that a Cyanobacteria monospecies genus and a Gemmatimonadetes multispecies genus are fastidiously predominant in the bare and vegetative wetlands of the Yellow River Delta, respectively. Consistently, photosynthesis genes were enriched exclusively in bare land, while genes involved in biological organic carbon metabolism and the cycling of main elements were highly expressed in vegetative wetlands, were mostly included in the MAG of Gemmatimonadetes, and were consistent with soil metabolomic results. Our results provide insight into the adaptive succession of predominant bacterial species and their ecosystem functions in response to the presence of vegetation.
Project description:Analysis of microbial gene expression in response to physical and chemical gradients forming in the Columbia River, estuary, plume and coastal ocean was done in the context of the environmental data base. Gene expression was analyzed for 2,234 individual genes that were selected from fully sequenced genomes of 246 prokaryotic species (bacteria and archaea) as related to the nitrogen metabolism and carbon fixation. Seasonal molecular portraits of differential gene expression in prokaryotic communities during river-to-ocean transition were created using freshwater baseline samples (268, 270, 347, 002, 006, 207, 212). Total RNA was isolated from 64 filtered environmental water samples collected in the Columbia River coastal margin during 4 research cruises (14 from August, 2007; 17 from November, 2007; 18 from April, 2008; and 16 from June, 2008), and analyzed using microarray hybridization with the CombiMatrix 4X2K format. Microarray targets were prepared by reverse transcription of total RNA into fluorescently labeled cDNA. All samples were hybridized in duplicate, except samples 212 and 310 (hybridized in triplicate) and samples 336, 339, 50, 152, 157, and 199 (hybridized once). Sample location codes: number shows distance from the coast in km; CR, Columbia River transect in the plume and coastal ocean; NH, Newport Hydroline transect in the coastal ocean at Newport, Oregon; AST and HAM, Columbia River estuary locations near Astoria (river mile 7-9) and Hammond (river mile 5), respectively; TID, Columbia River estuary locations in the tidal basin (river mile 22-23); BA, river location at Beaver Army Dock (river mile 53) near Quincy, Oregon; UP, river location at mile 74.
Project description:Analysis of microbial gene expression in response to physical and chemical gradients forming in the Columbia River, estuary, plume and coastal ocean was done in the context of the environmental data base. Gene expression was analyzed for 2,234 individual genes that were selected from fully sequenced genomes of 246 prokaryotic species (bacteria and archaea) as related to the nitrogen metabolism and carbon fixation. Seasonal molecular portraits of differential gene expression in prokaryotic communities during river-to-ocean transition were created using freshwater baseline samples (268, 270, 347, 002, 006, 207, 212).