scholarly journals The ecology of heterogeneity: soil bacterial communities and C dynamics

2021 ◽  
Author(s):  
Xavier Raynaud ◽  
Hannes Schmidt ◽  
Naoise Nunan
Keyword(s):  
Spatial Distribution ◽  
Microbial Ecology ◽  
Environmental Heterogeneity ◽  
Fundamental Property ◽  
Molecular Heterogeneity ◽  
Spatially Explicit Model ◽  
Fully Integrated ◽  
Soil Bacterial Communities ◽  
Decomposition Of Organic Matter ◽  
Bacterial Decomposition

<p>Heterogeneity is a fundamental property of soil that is often overlooked in microbial ecology. Although it is generally accepted that the heterogeneity of soil underpins the emergence and maintenance of microbial diversity, the profound and far-reaching consequences that heterogeneity can have on many aspects of microbial ecology and activity have yet to be fully apprehended and have not been fully integrated into our understanding of microbial functioning.</p><p>Heterogeneity in soils has multiple facets, from the molecular heterogeneity of the diversity of substrate available, the activity heterogeneity due to the activity of microbial species and the spatial heterogeneity of the soil structure and the distribution of organisms.</p><p>In this contribution we present a simple, spatially explicit model that can be used to understand how the interactions between the heterogeneity of decomposers (in terms of species and spatial distribution) and environmental heterogeneity (in terms of the diversity of substrates and their spatial distribution) affect the bacterial decomposition of organic matter. We found that environmental heterogeneity is a key element in determining the variability of the decomposition process.</p>

scholarly journals The ecology of heterogeneity: soil bacterial communities and C dynamics

2020 ◽  
Vol 375 (1798) ◽  
pp. 20190249 ◽  
Author(s):  
Naoise Nunan ◽  
Hannes Schmidt ◽  
Xavier Raynaud
Keyword(s):  
Microbial Ecology ◽  
Environmental Heterogeneity ◽  
Gene Copy Number ◽  
Fundamental Property ◽  
Gene Copy ◽  
Rrna Gene ◽  
Bacterial Strains ◽  
Potential Growth ◽  
Genome Database ◽  
Soil Bacterial

Heterogeneity is a fundamental property of soil that is often overlooked in microbial ecology. Although it is generally accepted that the heterogeneity of soil underpins the emergence and maintenance of microbial diversity, the profound and far-reaching consequences that heterogeneity can have on many aspects of microbial ecology and activity have yet to be fully apprehended and have not been fully integrated into our understanding of microbial functioning. In this contribution we first discuss how the heterogeneity of the soil microbial environment, and the consequent uncertainty associated with acquiring resources, may have affected how microbial metabolism, motility and interactions evolved and, ultimately, the overall microbial activity that is represented in ecosystem models, such as heterotrophic decomposition or respiration. We then present an analysis of predicted metabolic pathways for soil bacteria, obtained from the MetaCyc pathway/genome database collection ( https://metacyc.org/ ). The analysis suggests that while there is a relationship between phylogenic affiliation and the catabolic range of soil bacterial taxa, there does not appear to be a trade-off between the 16S rRNA gene copy number, taken as a proxy of potential growth rate, of bacterial strains and the range of substrates that can be used. Finally, we present a simple, spatially explicit model that can be used to understand how the interactions between decomposers and environmental heterogeneity affect the bacterial decomposition of organic matter, suggesting that environmental heterogeneity might have important consequences on the variability of this process. This article is part of the theme issue ‘Conceptual challenges in microbial community ecology’.

Bivariate normal song territories in ovenbirds

1978 ◽  
Vol 56 (10) ◽  
pp. 2088-2092 ◽  
Author(s):  
Reto Zach ◽  
J. Bruce Falls
Keyword(s):  
Spatial Distribution ◽  
Environmental Heterogeneity ◽  
Equal Frequency ◽  
Bivariate Normal ◽  
Fixed Boundaries

Song perches of each of nine male ovenbirds were bivariate normal in spatial distribution. Thus, song territories had no fixed boundaries. Song territories were elliptical rather than circular in shape, presumably due to environmental heterogeneity. Eighty-five percent equal frequency ellipses, which contain about 85% of the song perches of a given bird, corresponded approximately in area to the more conventional 95% song territory. Similarly, 90% equal frequency ellipses had about the same area as total song territories. However, all area estimates yielded closely correlated results. Distances between song centers and nest locations were highly variable. The distribution of nests was similar to that of song perches.

scholarly journals Dwarf-shrubs dynamics in Mediterranean high mountain ecosystems

2021 ◽  
Author(s):  
Andrea De Toma ◽  
Marta Carboni ◽  
Manuele Bazzichetto ◽  
Marco Malavasi ◽  
Maurizio Cutini
Keyword(s):  
Land Use ◽  
Spatial Distribution ◽  
Environmental Factors ◽  
Environmental Heterogeneity ◽  
Temporal Trends ◽  
Shrub Encroachment ◽  
High Mountain ◽  
Fine Scale ◽  
Dwarf Shrubs ◽  
The Past

AbstractQuestionVegetation in the alpine and treeline ecotone faces changes in both climate and land use. Shrub encroachment is considered an effect of these changes, but it’s still unclear how this effect is mediated by environmental heterogeneity. Our goal is to determine which environmental factors shape the fine-scale spatial distribution and temporal trends of alpine dwarf shrub.LocationThree sites in the Central Apennine, Italy.MethodsWe used a comprehensive set of environmental factors across a broad temporal span to model, at a fine-scale, both (1) the current spatial distribution and (2) the change in shrub cover over the past 60 years.ResultsOur results show that dwarf shrubs have generally increased in our study sites over the past 60 years, yet their distribution is strongly shaped by the joint influence of the fine-scale topography, productivity, land use and micro-climate. In particular, shrubs have been locally favored in areas with harsher alpine environmental constraints and stronger resource limitation. Instead, contrary to expectations, at this fine scale, warmer temperatures and the decline in grazing have not favored shrub encroachment.ConclusionDwarf shrubs appear as a stress-tolerant, pioneer vegetation that is currently distributed mainly over areas that are otherwise sparsely vegetated. It appears that shrubs exhibit poor competitive ability to invade grasslands and, though they have increased overall, they remain restricted to the least productive areas. Fine-scale environmental heterogeneity may strongly influence future responses of dwarf shrubs in changing alpine ecosystems.

scholarly journals How the Microbial World Saved Evolution from the Scylla of Molecular Biology and the Charybdis of the Modern Synthesis

2009 ◽  
Vol 73 (1) ◽  
pp. 14-21 ◽  
Author(s):  
Carl R. Woese ◽  
Nigel Goldenfeld
Keyword(s):  
Molecular Biology ◽  
Microbial Ecology ◽  
Microbial World ◽  
Fully Integrated ◽  
Current Thinking ◽  
Recent Developments ◽  
History Of ◽  
Relationship Of ◽  
The Relationship ◽  
History Of Microbiology

SUMMARY In this commentary, we provide a personal overview of the conceptual history of microbiology and molecular biology over the course of the last hundred years, emphasizing the relationship of these fields to the problem of evolution. We argue that despite their apparent success, all three reached an impasse that arose from the influence of dogmatic or overly narrow perspectives. Finally, we describe how recent developments in microbiology are realizing Beijerinck's vision of a field that is fully integrated with molecular biology, microbial ecology, thereby challenging and extending current thinking in evolution.

Geotechnical implications of diagenetic iron sulfide formation in Champlain Sea sediments

1979 ◽  
Vol 16 (3) ◽  
pp. 575-584 ◽  
Author(s):  
Joseph J. Donovan ◽  
Ginette Lajoie
Keyword(s):  
Iron Sulfide ◽  
Ferric Hydroxide ◽  
Geochemical Data ◽  
Stable Phase ◽  
Iron Hydroxides ◽  
Reducing Conditions ◽  
Decomposition Of Organic Matter ◽  
Bacterial Decomposition ◽  
The Stability ◽  
High Sulfide

It has been proposed that iron hydroxides act as cementing agents in Champlain Sea clays, causing brittle behaviour and high sensitivities. Study of interbedded turbiditic sandy and clayey strata of the Champlain Sea disputes this contention. Ground waters flowing through these sandy interbeds have high pH and are sodium bicarbonate dominant and strongly reduced, with a calculated Eh of −276 to −343 mV, using the sulfate–sulfide redox couple. During movement from recharge to discharge, sulfate is reduced by bacterial decomposition of organic matter in the clays, producing high sulfide and bicarbonate activities. In terms of Eh and pH, these waters fall within the stability fields of Fe2+ and FeS2.No pyrite was detected in the sediments, but in borehole samples and very fresh exposures of both clay and sand lithologies a very finely-disseminated black mineral phase, interpreted as iron monosulfides, was observed which is highly unstable in an aerobic environment, oxidizing rapidly to red-brown ferric hydroxide. The presence of these monosulfides, along with the aqueous geochemical data, indicate strongly reducing conditions in the clay strata, in which iron hydroxides are not a stable phase. Ferric hydroxides can therefore not be called upon as cementing agents; past studies which identified these ferric compounds as such cementing agents based their conclusions on samples out of equilibrium with their natural environment and are not directly relevant to the behaviour of the clay under natural conditions. The effects of these iron monosulfides and associated organic material on clay behaviour have not yet been studied.

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