Rhizosphere effects on soil nutrient dynamics and microbial activity in an Australian tropical lowland rainforest

Soil Research ◽  
2011 ◽  
Vol 49 (7) ◽  
pp. 652 ◽  
Author(s):  
Hannah Toberman ◽  
Chengrong Chen ◽  
Zhihong Xu
Keyword(s):  
Nutrient Cycling ◽  
Microbial Activity ◽  
Tropical Rainforest ◽  
Rhizosphere Soil ◽  
Critical Role ◽  
Total Carbon ◽  
Bulk Soil ◽  
Soluble Nitrogen ◽  
Global Cycles ◽  
Rhizosphere Processes

Via vast exchanges of energy, water, carbon, and nutrients, tropical forests are a major driving force in the regulation of Earth’s biogeochemical, hydrological, and climatic cycles. Given the critical role of rhizosphere processes in nutrient cycling, it is likely that rhizosphere processes in tropical rainforests form a major component of the biome’s interactions with global cycles. Little is known, however, about rhizospheric processes in rainforest soils. In order to investigate the influence of rhizosphere processes upon rainforest nutrient cycling, we compared the nutrient status and microbial activity of rhizospheric soil from Australian lowland tropical rainforest with that of the surrounding bulk soil. We found a marked difference in the biological and chemical nature of the rhizosphere and bulk soils. Total carbon, microbial biomass carbon, total nitrogen, soluble nitrogen, and a suite of trace element concentrations, alongside microbial respiration and the rate and diversity of carbon substrate use, were all significantly higher in the rhizosphere soil than the bulk soil. Rhizosphere soil δ15N was significantly lower than that of the bulk soil. Ratios of carbon, nitrogen, phosphorus, and sulfur differed significantly between the rhizosphere and bulk soil. These clear differences suggest that rhizosphere processes strongly influence nutrient cycling in lowland tropical rainforest, and are likely to play an important role in its interaction with global cycles. This role may be under-represented with composite sampling of rhizosphere and bulk soil. Further research is required regarding the mechanisms of rainforest rhizospheric processes and their relationship with ecosystem productivity, stability, and environmental change.

Vegetation alters how soil properties and climate influence microbial activity and functional diversity in rhizosphere and bulk soil along an elevation gradient

2021 ◽  
pp. 108485
Author(s):  
Daniel Hernández-Cáceres ◽  
Alexia Stokes ◽  
Guillermo Angeles-Alvarez ◽  
Josiane Abadie ◽  
Fabien Anthelme ◽  
...  
Keyword(s):  
Soil Properties ◽  
Microbial Activity ◽  
Functional Diversity ◽  
Elevation Gradient ◽  
Bulk Soil

scholarly journals Changes in Microbial Community Composition and Function during a Polyaromatic Hydrocarbon Phytoremediation Field Trial

2003 ◽  
Vol 69 (1) ◽  
pp. 483-489 ◽  
Author(s):  
Steven D. Siciliano ◽  
James J. Germida ◽  
Kathy Banks ◽  
Charles W. Greer
Keyword(s):  
Microbial Community ◽  
Festuca Arundinacea ◽  
Rhizosphere Soil ◽  
Microbial Community Composition ◽  
Hydrocarbon Degradation ◽  
Bulk Soil ◽  
Catabolic Gene ◽  
Soil Microbial ◽  
Catabolic Genes ◽  
And Function

ABSTRACT The purpose of this study was to investigate the mechanism by which phytoremediation systems promote hydrocarbon degradation in soil. The composition and degradation capacity of the bulk soil microbial community during the phytoremediation of soil contaminated with aged hydrocarbons was assessed. In the bulk soil, the level of catabolic genes involved in hydrocarbon degradation (ndoB, alkB, and xylE) as well as the mineralization of hexadecane and phenanthrene was higher in planted treatment cells than in treatment cells with no plants. There was no detectable shift in the 16S ribosomal DNA (rDNA) composition of the bulk soil community between treatments, but there were plant-specific and -selective effects on specific catabolic gene prevalence. Tall Fescue (Festuca arundinacea) increased the prevalence of ndoB, alkB, and xylE as well as naphthalene mineralization in rhizosphere soil compared to that in bulk soil. In contrast, Rose Clover (Trifolium hirtum) decreased catabolic gene prevalence and naphthalene mineralization in rhizosphere soil. The results demonstrated that phytoremediation systems increase the catabolic potential of rhizosphere soil by altering the functional composition of the microbial community. This change in composition was not detectable by 16S rDNA but was linked to specific functional genotypes with relevance to petroleum hydrocarbon degradation.

scholarly journals Ant nests as a microbial hot spots in a long-term heavy metal-contaminated soils

2021 ◽  
Author(s):  
Beata Klimek ◽  
Hanna Poliwka-Modliborek ◽  
Irena M. Grześ
Keyword(s):  
Microbial Biomass ◽  
Microbial Activity ◽  
Respiration Rate ◽  
Metal Content ◽  
Soil Microbial Activity ◽  
Bulk Soil ◽  
Lasius Niger ◽  
Soil Microbial ◽  
Ant Nests

AbstractInteractions between soil fauna and soil microorganisms are not fully recognized, especially in extreme environments, such as long-term metal-polluted soils. The purpose of the study was to assess how the presence of Lasius niger ants affected soil microbial characteristics in a long-term metal-polluted area (Upper Silesia in Poland). Paired soil samples were taken from bulk soil and from ant nests and analysed for a range of soil physicochemical properties, including metal content (zinc, cadmium, and lead). Microbial analysis included soil microbial activity (soil respiration rate), microbial biomass (substrate-induced respiration rate), and bacteria catabolic properties (Biolog® ECO plates). Soil collected from ant nests was drier and was characterized by a lower content of organic matter, carbon and nitrogen contents, and also lower metal content than bulk soil. Soil microbial respiration rate was positively related to soil pH (p = 0.01) and negatively to water-soluble metal content, integrated into TIws index (p = 0.01). Soil microbial biomass was negatively related to TIws index (p = 0.04). Neither soil microbial activity and biomass nor bacteria catabolic activity and diversity indices differed between bulk soil and ant nests. Taken together, ant activity reduced soil contamination by metals in a microscale which support microbial community activity and biomass but did not affect Biolog® culturable bacteria.

Biological processes in modelling soil functions – a balancing act between too complex and too simple

2021 ◽  
Author(s):  
Sara König ◽  
Ulrich Weller ◽  
Thomas Reitz ◽  
Bibiana Betancur-Corredor ◽  
Birgit Lang ◽  
...  
Keyword(s):  
Nutrient Cycling ◽  
Microbial Activity ◽  
Community Dynamics ◽  
Spatial Scales ◽  
Simulation Models ◽  
Microbial Processes ◽  
Biological Processes ◽  
Soil Functions ◽  
Management Options ◽  
The Impact

<p>Mechanistic simulation models are an essential tool for predicting soil functions such as nutrient cycling, water filtering and storage, productivity and carbon storage as well as the complex interactions between these functions. Most soil functions are driven or affected by soil organisms. Yet, biological processes are often neglected in soil function models or implicitly described by rate parameters. This can be explained by the high complexity of the soil ecosystem with its dynamic and heterogeneous environment, and by the range of temporal and spatial scales these processes are taking place at. On the other hand, the technical capabilities to explore microbial activity and communities in soil has greatly improved, resulting in new possibilities to understand soil microbial processes on various scales.</p><p>However, to integrate such biological processes in soil modelling, we need to find the right level of detail. Here, we present a systemic soil model approach to simulate the impact of different management options and changing climate on soil functions integrating biological activity on the profile scale. We use stoichiometric considerations to simulate microbial processes involved in different soil functions without explicitly describing community dynamics or functional groups. With this approach we are able to mechanistically describe microbial activity and its impact on the turnover of organic matter and nutrient cycling as driven by agricultural soil management.</p><p>Further, we discuss general challenges and ongoing developments to additionally consider, e.g., microbe-fauna-interactions or microbial feedback with soil structure dynamics.</p>

scholarly journals   Distribution of recently fixed photosynthate in a switchgrass plant-soil system

2012 ◽  
Vol 58 (No. 6) ◽  
pp. 249-255 ◽  
Author(s):  
D.R. Chaudhary ◽  
J. Saxena ◽  
N. Lorenz ◽  
R.P. Dick
Keyword(s):  
Panicum Virgatum ◽  
Rhizosphere Soil ◽  
Microbial Biomass Carbon ◽  
Bulk Soil ◽  
Energy Crop ◽  
Marginal Lands ◽  
Soil System ◽  
Plant Soil ◽  
Panicum Virgatum L ◽  
Maintenance Requirements

The use of switchgrass (Panicum virgatum L.) as an energy crop has gained great importance in past two decades due to its high biomass yields on marginal lands with low agricultural inputs and low maintenance requirements. Information on the allocation of photosynthetically fixed C in the switchgrass-soil system is important to understand the C flow and to quantify the sequestration of C in soils. The allocation of <sup>13</sup>C labeled photosynthates in shoot, root, soil, and in microbial biomass carbon (MBC) of rhizosphere and bulk soil of 45 days old, greenhouse grown-switchgrass was examined during 20 days <sup>13</sup>C-CO<sub>2</sub> pulse labeling period. The total <sup>13</sup>C recovered in the plant-soil system varied from 79% after 1 day to 42% after 20 days of labeling. After labeling, 54%, 40%, and 6% excess <sup>13</sup>C resided in shoot, root and soil, respectively on day 1; 27%, 61% and 11%, respectively on day 5 and 20%, 63% and 17%, respectively day 20 after labeling. The maximum incorporation of <sup>13</sup>C from roots into the MB of rhizosphere soil occurred within the first 24 h of labeling. The excess <sup>13</sup>C values of rhizosphere soil and rhizosphere MBC were significantly higher than excess <sup>13</sup>C values of bulk soil and the bulk soil MBC, respectively. The proportion of excess <sup>13</sup>C in soil as MBC declined from 92 to 15% in rhizosphere soil and from 79 to 18% in bulk soil, for 1 day and 20 days after labeling, respectively. The present study showed the effectiveness of <sup>13</sup>C labeling to examine the fate of recently photosynthesized C in soil-plant (switchgrass) system and dynamics of MBC. &nbsp;

A component model of decomposition of Spartina alterniflora in a New Jersey salt marsh

1982 ◽  
Vol 60 (9) ◽  
pp. 1618-1624 ◽  
Author(s):  
Andrew C. Marinucci ◽  
R. Bartha
Keyword(s):  
New Jersey ◽  
Salt Marsh ◽  
Spartina Alterniflora ◽  
Dry Weight ◽  
Logistic Function ◽  
Total Carbon ◽  
Component Model ◽  
Soluble Nitrogen ◽  
Litter Bags ◽  
Microbial Nitrogen

Spartina alterniflora decomposition was monitored in the high and low salt marsh in litter bags (2-mm mesh). The detritus formed in this process was analyzed at various times for ash-free dry weight (AFDW) (combustion at 550 °C), total carbon (wet combustion to CO2), and total nitrogen (Kjeldahl digestion). A mathematical component model predicting the change of these parameters was developed to explain these data.The first-order decay equation Xt = X0 e−kt was used to explain AFDW and carbon changes. The k values ranged from 0.004 to 0.02 per day for data from the high and low marsh, respectively, for New Jersey. Nitrogen fluxes are described by four functions. Three of these are decay functions which theoretically model (1) loss of soluble nitrogen, (2) loss of recalcitrant nitrogenous plant material, and (3) loss of microbial nitrogen. The fourth is a logistic function which describes the microbial incorportaion of nitrogen into the detritus. Nitrogen and C/N ratio values calculated with these equations simulated values obtained from field data.

Microbial activity and diversity in the rhizosphere soil of the invasive species Zizania latifolia in the wetland of Wuchang Lake, China

2020 ◽  
Vol 71 (12) ◽  
pp. 1702
Author(s):  
Baohua Zhou ◽  
Zhaowen Liu ◽  
Guo Yang ◽  
Hui He ◽  
Haijun Liu
Keyword(s):  
Invasive Species ◽  
Rhizosphere Soil ◽  
Remote Sensing Data ◽  
Wetland Loss ◽  
Freshwater Wetlands ◽  
Total Carbon ◽  
Freshwater Wetland ◽  
Available Nitrogen ◽  
Zizania Latifolia ◽  
Rhizosphere Soils

Information about the consequences of invasive species overgrowing freshwater wetlands is limited. According to remote sensing data, the invasive species Zizania latifolia spreads at an annual rate of 1.78km2 in the freshwater wetland of Wuchang Lake, China, resulting in wetland loss and degradation due to the overgrowth. This species not only increases soil organic matter, total carbon, total nitrogen, total sulfate, available nitrogen and the C/N ratio in the rhizosphere soil, but also results in increased urease, sucrose and catalase activity, as well as fluorescein diacetate hydrolysis. In this study, we have analysed microbial diversity in rhizosphere soils among different habitat types of Z. latifolia. Microbial communities in different habitats invaded by Z. latifolia differed considerably at the genus level, although all soil samples were predominated by the phyla Proteobacteria, Acidobacteria and Chloroflexi. The dominant bacterial taxa in the rhizosphere soil from the floating blanket included Acidimicrobiales, Thiomonas, Alicyclobacillus, Acetobacteraceae and Acidocella, whereas those in rhizosphere soils from the lake sludge were Acidobacteria, Anaerolineaceae, Bacteroidetes and Nitrospirae. The bacterial community in the rhizosphere soil differed significantly from that in the non-rhizosphere soil. Z. latifolia potentially creates suitable habitats and provides substrate for a unique set of microbes, further facilitating the succession of this species.

scholarly journals Microbial carbon recycling: an underestimated process controlling soil carbon dynamics – Part 2: A C<sub>3</sub>-C<sub>4</sub> vegetation change field labelling experiment

2015 ◽  
Vol 12 (21) ◽  
pp. 6291-6299 ◽  
Author(s):  
A. Basler ◽  
M. Dippold ◽  
M. Helfrich ◽  
J. Dyckmans
Keyword(s):  
Organic Matter ◽  
Particulate Organic Matter ◽  
Vegetation Change ◽  
Isotope Ratio Mass Spectrometry ◽  
Isotopic Signature ◽  
Total Carbon ◽  
Bulk Soil ◽  
Residence Times ◽  
Soil Matrix ◽  
Labelling Experiment

Abstract. The mean residence times (MRT) of different compound classes of soil organic matter (SOM) do not match their inherent recalcitrance to decomposition. One reason for this is the stabilization within the soil matrix, but recycling, i.e. the reuse of "old" organic material to form new biomass may also play a role as it uncouples the residence times of organic matter from the lifetime of discrete molecules in soil. We analysed soil sugar dynamics in a natural 30-year old labelling experiment after a wheat-maize vegetation change to determine the extent of recycling and stabilization by assessing differences in turnover dynamics between plant and microbial-derived sugars: while plant-derived sugars are only affected by stabilization processes, microbial sugars may be subject to both, stabilization and recycling. To disentangle the dynamics of soil sugars, we separated different density fractions (free particulate organic matter (fPOM), light occluded particulate organic matter (≤ 1.6 g cm−3; oPOM1.6), dense occluded particulate organic matter (≤ 2 g cm−3; oPOM2) and mineral-associated organic matter (> 2 g cm−3; mineral)) of a silty loam under long-term wheat and maize cultivation. The isotopic signature of neutral sugars was measured by high pressure liquid chromatography coupled to isotope ratio mass spectrometry (HPLC/IRMS), after hydrolysis with 4 M Trifluoroacetic acid. While apparent MRT of sugars were comparable to total organic carbon in the bulk soil and mineral fraction, the apparent MRT of sugar carbon in the oPOM fractions were considerably lower than those of the total carbon of these fractions. This indicates that oPOM formation was fuelled by microbial activity feeding on new plant input. In the bulk soil, MRT of the mainly plant-derived xylose were significantly lower than those of mainly microbial-derived sugars like galactose, rhamnose, fucose, indicating that recycling of organic matter is an important factor regulating organic matter dynamics in soil.

Root exudate induced microbial activities and phosphorus cycling in soil: An application of phosphate oxygen isotopes

2020 ◽  
Author(s):  
Sunendra R Joshi ◽  
David H McNear
Keyword(s):  
Microbial Community ◽  
Isotopic Composition ◽  
Oxygen Isotope ◽  
Microbial Activity ◽  
Oxygen Isotopes ◽  
Root Exudate ◽  
Rhizosphere Soil ◽  
Microbial Activities ◽  
Oxygen Isotope Ratios ◽  
P Cycling

&lt;p&gt;Rhizosphere is the most biologically active region between the plant and the surrounding soil where plant release their fixed carbon into the soils. Depending on the availability and types of carbon compounds released from the plant, they can directly solubilize nutrient or indirectly influence nutrient cycling by promoting increased microbial activity in the rhizosphere. In this study we applied phosphate oxygen isotope ratios (d&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;P&lt;/sub&gt;) to determine how root exudate influences temporal variation in microbial activities and P cycling in the rhizosphere. Rhizoboxes were filled with soils, watered to 75% water holding capacity and equilibrated for 10 days. After equilibration labeled phosphate isotopes synthesized using &lt;sup&gt;18&lt;/sup&gt;O labeled water was applied. Then a mixed exudate (i.e., glucose, alanine, and oxalate in the ratio of 1:1:1) was introduced into the soil for 4, 10, and 20 days via an artificial root. We used a sequential extraction technique (i.e., resin-Pi, NaHCO&lt;sub&gt;3&lt;/sub&gt;-P, NaOH-P, and HCl-P) to track the fate of applied P in bulk and rhizosphere soils. The root exudate effects on the rate of P cycling and microbial activity were investigated using phosphate oxygen isotope ratios in the resin-Pi pool. Microbial community structures was determined using phospholipid fatty acids (PLFA) profiles. After supplying root exudate for 4, 10, and 20 days, the results showed that bioavailable P (i.e., resin-Pi) concentration was always higher in the bulk soil compared to rhizosphere soil and originally bioavailable P transformed gradually into unavailable P (i.e., NaOH-P and HCl-P). After supplying exudate compound for 4 days, the applied PO&lt;sub&gt;4&lt;/sub&gt; was mostly in the resin-Pi pool and its isotopic composition was heavier than the equilibrium isotopic composition suggesting that this Pi pool was not completely cycled by the microorganisms. As we continue supplying exudate compounds, the concentration of resin-Pi gradually decreased and as microbial activities increased, its isotopic composition got closer to the equilibrium isotopic composition. Further the microbial community structure in the rhizosphere soil after supply of root exudate were distinctly different then the bulk soil. Using phosphate oxygen isotopes this study shows the influence of root exudates on the rate of P cycling in rhizosphere soils.&lt;/p&gt;

Which role do preferential flowpaths and fractures play in the subsurface reactivity in heterogeneous aquifers?

2020 ◽  
Author(s):  
Camille Bouchez ◽  
Nicolas Lavenant ◽  
Julien Farasin ◽  
Thierry Labasque ◽  
Ivan Osorio ◽  
...  
Keyword(s):  
Nutrient Cycling ◽  
Microbial Activity ◽  
Fresh Water ◽  
Transit Time ◽  
Major Ions ◽  
Mean Transit Time ◽  
Fracture Network ◽  
Reaction Rates ◽  
Fractured Aquifer ◽  
Preferential Flowpaths

&lt;p&gt;The underground fracture pattern, which results from tectonic, climatic and biological stresses, drives water storage dynamic and nutrient cycling in the deep critical zone. Despite a gradual decrease of fracture density with depth, the fracture network is strongly heterogeneous and anisotropic, resulting in a complex pathway distribution with variable hydraulic conductivities. High celerities occurring in preferential flowpaths govern the dynamic response of discharge flows to extreme recharge events. However, the role of preferential flowpaths in transporting fresh meteoritic water and biota remains poorly studied, while the delivery of meteoritic reactants is crucial to initiate underground chemical reactions.&lt;/p&gt;&lt;p&gt;Here, we study a fractured aquifer in a crystalline catchment located in Brittany (Guidel, France) to investigate the link between depth, water transit time and subsurface reactivity in fractures. Oxygen is used as a tracer of fresh water inputs because its availability has a tremendous impact on oxidation-driven reactions such as weathering processes and microbial activity. We performed vertically sampling of fracture fluid with an inflatable packer capable of isolating fractures in an artesian well located in the discharge chemically-reduced zone of the aquifer. Major ions, dissolved reactive gases, dissolved anthropogenic gases, stable isotopes (O, Sr and Si) and microbial diversity were analysed on five fracture waters sampled at depth between 20 and 55 m. Significant differences have been observed between fractures and younger and more oxygenated waters were found intermittently in fractures at 47 and 54m, with dissolved oxygen concentrations ranging between 0.1 and 0.5 mg/L. The penetration of oxygen in deep fractures reveals either a rapid transport of oxygen or a low consumption of oxygen in preferential flowpaths. These hypotheses are tested with a Discrete Fracture Network model, where first-order reaction rates have been implemented, and the temporal dynamic of oxygen is assessed and linked to water transit time in fractures. We investigate the concept of transit time and water-rock contact time and discuss the relevance of mean transit time to evaluate subsurface reactivity.&lt;/p&gt;&lt;p&gt;Preferential flowpaths thus not only make fractured aquifers more dynamic but can also, under extreme recharge conditions, efficiently transport fresh water at high depth. The advective-dominant transport of oxygen through artery-like fractures could have a significant impact on short term microbial activity and the associated nutrient cycling but also on long term weathering front propagation.&lt;/p&gt;

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