Changes in variability of soil moisture alter microbial community C and N resource use

During a 3-year study, soil microbial biomass C and N, length of the fungal hyphae, soil respiration, and the percent mass loss of needle litter were recorded in coniferous forest soil humus layers following a prescribed burning (PB) treatment or a forest fire simulation (FF) treatment (five plots per treatment). Unburned humus from adjacent plots served as controls (PC and FC, respectively). Prescribed burning was more intensive than the forest fire, and this was reflected in all the measurements taken. The amounts of microbial biomass C and N, length of fungal hyphae, and soil respiration in the PB area did not recover to their controls levels, whereas unchanged microbial biomass N and recovery of the length of the fungal hyphae to control levels were observed in the FF area. The mean microbial C/N ratio was approximately 7 in all the areas, which reflected the C/N ratio of the soil microbial community. Deviation from this mean value, as observed during the first three samplings from the PB area (3, 18, and 35 days after fire treatment), suggested a change in the composition of the microbial community. Of the two treated areas, the decrease in soil respiration (laboratory measurements) was much more pronounced in the PB area. However, when the humus samples from both areas were adjusted to 60% water holding capacity, no differences in respiration capacity were observed. The drier humus, due to higher soil temperatures, of the PB area is a likely explanation for the low soil respiration. Lower soil respiration was not reflected in lower litter decomposition rates of the PB area, since there was a significantly higher needle litter mass loss during the first year in the PB area followed by a decline to the control level during the second year. Consistently higher mass losses were recorded in the FC area than in the FF area.

Download Full-text

Visualizing Microbial Community Dynamics via a Controllable Soil Environment

mSystems ◽

10.1128/msystems.00645-19 ◽

2020 ◽

Vol 5 (1) ◽

Cited By ~ 1

Author(s):

Arunima Bhattacharjee ◽

Dusan Velickovic ◽

Thomas W. Wietsma ◽

Sheryl L. Bell ◽

Janet K. Jansson ◽

...

Keyword(s):

Soil Moisture ◽

Microbial Community ◽

Microbial Communities ◽

Community Dynamics ◽

Soil Microbial Communities ◽

Soil Microbiome ◽

Soil Core ◽

Soil Microbial ◽

Functional Relationships ◽

Microbial Community Dynamics

ABSTRACT Understanding the basic biology that underpins soil microbiome interactions is required to predict the metaphenomic response to environmental shifts. A significant knowledge gap remains in how such changes affect microbial community dynamics and their metabolic landscape at microbially relevant spatial scales. Using a custom-built SoilBox system, here we demonstrated changes in microbial community growth and composition in different soil environments (14%, 24%, and 34% soil moisture), contingent upon access to reservoirs of nutrient sources. The SoilBox emulates the probing depth of a common soil core and enables determination of both the spatial organization of the microbial communities and their metabolites, as shown by confocal microscopy in combination with mass spectrometry imaging (MSI). Using chitin as a nutrient source, we used the SoilBox system to observe increased adhesion of microbial biomass on chitin islands resulting in degradation of chitin into N-acetylglucosamine (NAG) and chitobiose. With matrix-assisted laser desorption/ionization (MALDI)-MSI, we also observed several phospholipid families that are functional biomarkers for microbial growth on the chitin islands. Fungal hyphal networks bridging different chitin islands over distances of 27 mm were observed only in the 14% soil moisture regime, indicating that such bridges may act as nutrient highways under drought conditions. In total, these results illustrate a system that can provide unprecedented spatial information about interactions within soil microbial communities as a function of changing environments. We anticipate that this platform will be invaluable in spatially probing specific intra- and interkingdom functional relationships of microbiomes within soil. IMPORTANCE Microbial communities are key components of the soil ecosystem. Recent advances in metagenomics and other omics capabilities have expanded our ability to characterize the composition and function of the soil microbiome. However, characterizing the spatial metabolic and morphological diversity of microbial communities remains a challenge due to the dynamic and complex nature of soil microenvironments. The SoilBox system, demonstrated in this work, simulates an ∼12-cm soil depth, similar to a typical soil core, and provides a platform that facilitates imaging the molecular and topographical landscape of soil microbial communities as a function of environmental gradients. Moreover, the nondestructive harvesting of soil microbial communities for the imaging experiments can enable simultaneous multiomics analysis throughout the depth of the SoilBox. Our results show that by correlating molecular and optical imaging data obtained using the SoilBox platform, deeper insights into the nature of specific soil microbial interactions can be achieved.

Download Full-text

Temperature and soil moisture control microbial community composition in an arctic–alpine ecosystem along elevational and micro-topographic gradients

The ISME Journal ◽

10.1038/s41396-019-0409-9 ◽

2019 ◽

Vol 13 (8) ◽

pp. 2031-2043 ◽

Cited By ~ 8

Author(s):

K. Frindte ◽

R. Pape ◽

K. Werner ◽

J. Löffler ◽

C. Knief

Keyword(s):

Soil Moisture ◽

Microbial Community ◽

Community Composition ◽

Microbial Community Composition ◽

Moisture Control ◽

Alpine Ecosystem ◽

Topographic Gradients

Download Full-text

Nitrogen fertilizer regulates soil respiration by altering the organic carbon storage in root and topsoil in alpine meadow of the north-eastern Qinghai-Tibet Plateau

Scientific Reports ◽

10.1038/s41598-019-50142-y ◽

2019 ◽

Vol 9 (1) ◽

Author(s):

Wen Li ◽

Jinlan Wang ◽

Xiaolong Li ◽

Shilin Wang ◽

Wenhui Liu ◽

...

Keyword(s):

Soil Moisture ◽

Tibetan Plateau ◽

Soil Respiration ◽

Alpine Meadow ◽

Growing Season ◽

N Storage ◽

The North ◽

C Storage ◽

North Eastern ◽

C And N

Abstract Soil respiration (Rs) plays a critical role in the global carbon (C) balance, especially in the context of globally increasing nitrogen (N) deposition. However, how N-addition influences C cycle remains unclear. Here, we applied seven levels of N application (0 (N0), 54 (N1), 90 (N2), 126 (N3), 144 (N4), 180 (N5) and 216 kg N ha−1 yr−1 (N6)) to quantify their impacts on Rs and its components (autotrophic respiration (Ra) and heterotrophic respiration (Rh)) and C and N storage in vegetation and soil in alpine meadow on the northeast margin of the Qinghai-Tibetan Plateau. We used a structural equation model (SEM) to explore the relative contributions of C and N storage, soil temperature and soil moisture and their direct and indirect pathways in regulating soil respiration. Our results revealed that the Rs, Ra and Rh, C and N storage in plant, root and soil (0–10 cm and 10–20 cm) all showed initial increases and then tended to decrease at the threshold level of 180 kg N ha−1 yr−1. The SEM results indicated that soil temperature had a greater impact on Rs than did volumetric soil moisture. Moreover, SEM also showed that C storage (in root, 0–10 and 10–20 cm soil layers) was the most important factor driving Rs. Furthermore, multiple linear regression model showed that the combined root C storage, 0–10 cm and 10–20 cm soil layer C storage explained 97.4–97.6% variations in Rs; explained 94.5–96% variations in Ra; and explained 96.3–98.1% in Rh. Therefore, the growing season soil respiration and its components can be well predicted by the organic C storage in root and topsoil in alpine meadow of the north-eastern Qinghai-Tibetan Plateau. Our study reveals the importance of topsoil and root C storage in driving growing season Rs in alpine meadow on the northeast margin of Qinghai-Tibetan Plateau.

Download Full-text

Seasonal trends in selected soil biochemical attributes: Effects of crop rotation in the semiarid prairie

Canadian Journal of Soil Science ◽

10.4141/s98-008 ◽

1999 ◽

Vol 79 (1) ◽

pp. 73-84 ◽

Cited By ~ 38

Author(s):

C. A. Campbell ◽

V. O. Biederbeck ◽

G. Wen ◽

R. P. Zentner ◽

J. Schoenau ◽

...

Keyword(s):

Soil Moisture ◽

Microbial Biomass ◽

Microbial Biomass Carbon ◽

Light Fraction ◽

Water Soluble ◽

Microbial Biomass C ◽

Weather Variables ◽

Total N ◽

Organic C ◽

C And N

Measurements of seasonal changes in soil biochemical attributes can provide valuable information on how crop management and weather variables influence soil quality. We sampled soil from the 0- to 7.5-cm depth of two long-term crop rotations [continuous wheat (Cont W) and both phases of fallow-wheat (F–W)] at Swift Current, Saskatchewan, from early May to mid-October, 11 times in 1995 and 9 times in 1996. The soil is a silt loam, Orthic Brown Chernozem with pH 6.0, in dilute CaCl2. We monitored changes in organic C (OC) and total N (TN), microbial biomass C (MBC), light fraction C and N (LFC and LFN), mineralizable C (Cmin) and N (Nmin), and water-soluble organic C (WSOC). All biochemical attributes, except MBC, showed higher values for Cont W than for F–W, reflecting the historically higher crop residue inputs, less frequent tillage, and drier conditions of Cont W. Based on the seasonal mean values for 1996, we concluded that, after 29 yr, F–W has degraded soil organic C and total N by about 15% compared to Cont W. In the same period it has degraded the labile attributes, except MBC, much more. For example, WSOC is degraded by 22%, Cmin and Nmin by 45% and LFC and LFN by 60–75%. Organic C and TN were constant during the season because one year's C and N inputs are small compared to the total soil C or N. All the labile attributes varied markedly throughout the seasons. We explained most of the seasonal variability in soil biochemical attributes in terms of C and N inputs from crop residues and rhizodeposition, and the influences of soil moisture, precipitation and temperature. Using multiple regression, we related the biochemical attributes to soil moisture and the weather variables, accounting for 20% of the variability in MBC, 27% of that of Nmin, 29% for LFC, 52% for Cmin, and 66% for WSOC. In all cases the biochemical attributes were negatively related to precipitation, soil moisture, temperature and their interactions. We interpreted this to mean that conditions favouring decomposition of organic matter in situ result in decreases in these attributes when they are measured subsequently under laboratory conditions. We concluded that when assessing changes in OC or TN over years, measurements can be made at any time during a year. However, if assessing changes in the labile soil attributes, several measurements should be made during a season or, measurements be made near the same time each year. Key words: Microbial biomass, carbon, nitrogen, mineralization, water-soluble-C, light fraction, weather variables

Download Full-text

Nitrogen- and sulfur-deposition-altered soil microbial community functions and enzyme activities in a boreal mixedwood forest in western Canada

Canadian Journal of Forest Research ◽

10.1139/cjfr-2013-0049 ◽

2013 ◽

Vol 43 (9) ◽

pp. 777-784 ◽

Cited By ~ 12

Author(s):

Ya-Lin Hu ◽

Kangho Jung ◽

De-Hui Zeng ◽

Scott X. Chang

Keyword(s):

Microbial Community ◽

Microbial Biomass ◽

Soil Microbial Community ◽

Oil Sands ◽

Soil Microbial Biomass ◽

Soil Microbial ◽

C And N ◽

Boreal Mixedwood Forest ◽

The Impact ◽

S Deposition

Chronic nitrogen (N) and (or) sulfur (S) deposition to boreal forests in the Athabasca oil sands region (AOSR) in Alberta, Canada, has been caused by oil sands mining and extraction/upgrading activities. It is important that we understand the response of microbial community function to chronic N and S deposition as microbial populations mediate soil carbon (C) and N cycles and affect ecosystem resilience. To evaluate the impact of N and (or) S deposition on soil microbial community functions, we conducted a simulated N and S deposition experiment in a boreal mixedwood forest with the following four treatments: control (CK), N addition (+N, 30 kg N·ha−1 as NH4NO3), S addition (+S, 30 kg S·ha−1 as NaSO4), and N plus S addition (+NS, 30 kg N·ha−1 + 30 kg S·ha−1), from 2006 to 2010. Nitrogen and (or) S deposition did not change soil organic carbon, total N, dissolved organic C and N, or soil microbial biomass C and N. Soil microbial community-level physiological profiles, however, were strongly affected by 5 years of N and (or) S addition. Soil β-glucosidase activity in the +NS treatment was greater than that in the +S treatment, and S addition decreased soil arylsulfatase; however, urease and dehydrogenase activities were not affected by the simulated N and (or) S deposition. Our data suggested that N and (or) S deposition strongly affected soil microbial community functions and enzymatic activities without changing soil microbial biomass in the studied boreal forest.

Download Full-text