Publisher Summary
Humus is defined as being synonymous with soil organic matter, which in turn is the total organic matter in a soil exclusive of the biomass and undecayed material Dissolved humus consists of the dissolved organic material (DOM) in soil, which influences the overall ecology and geochemistry of soil This chapter focuses on the DOM's ecological role in the unsaturated zone, with the saturated zone and the surface aquatic ecosystems being peripherally considered The relation of the DOM to other ecological components in soil is influenced by two types of fluxes The first one is physical diffusion The DOM diffuses over a concentration gradient The second physical flux is convection, which is dependent on a gradient in the soil's water content as a result of precipitation The dissolved humus is mobile and so it can be fully available theoretically This mobility and availability is not constant; it can vary both over space and time The potential ecological function and in situ availability of the dissolved humus are considered in the chapter so that one is able to understand and predict its environmental role

Dissolved Humus in Soil Waters

Soil-borne microbial communities were examined via a functional gene microarray approach across a southern polar latitudinal gradient to gain insight into the environmental factors steering soil N- and C-cycling in terrestrial Antarctic ecosystems. The abundance and diversity of functional gene families were studied for soil-borne microbial communities inhabiting a range of environments from 51°S (cool temperate – Falkland Islands) to 72°S (cold rock desert – Coal Nunatak). The recently designed functional gene array used contains 24 243 oligonucleotide probes and covers >10 000 genes in >150 functional groups involved in nitrogen, carbon, sulfur and phosphorus cycling, metal reduction and resistance and organic contaminant degradation (He et al. 2007). The detected N- and C-cycle genes were significantly different across different sampling locations and vegetation types. A number of significant trends were observed regarding the distribution of key gene families across the environments examined. For example, the relative detection of cellulose degradation genes was correlated with temperature, and microbial C-fixation genes were more present in plots principally lacking vegetation. With respect to the N-cycle, denitrification genes were linked to higher soil temperatures, and N2-fixation genes were linked to plots mainly vegetated by lichens. These microarray-based results were confirmed for a number of gene families using specific real-time PCR, enzymatic assays and process rate measurements. The results presented demonstrate the utility of an integrated functional gene microarray approach in detecting shifts in functional community properties in environmental samples and provide insight into the forces driving important processes of terrestrial Antarctic nutrient cycling.

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Functional microarray analysis of nitrogen and carbon cycling genes across an Antarctic latitudinal transect.

Size and structure of bacterial, fungal and nematode communities along an Antarctic environmental gradient

Climatic changes will not only result in higher overall temperature, but also in greater variability in weather conditions. Antarctic soils are subjected to extremely variable conditions in the form of frequent freeze–thaw cycles (FTCs), but the importance of alteration in FTC frequency, compared with increases in average temperature and indirect vegetation-mediated effects on soil microorganisms, is still unknown. We therefore designed two complementary microcosm experiments using undisturbed soil cores from Signy Island (60°43'S, 45°38'W) in the maritime Antarctic. The experiments consisted of soil core incubations with or without the overlying vegetation at four different temperatures and six different FTC regimes. We assessed bacterial and fungal density and community structure, as well as the density of several key genes in microbial nutrient cycles using a combination of RNA- and DNA-based molecular fingerprinting and quantitative PCR approaches in addition to enzymatic activity assays. Results showed that bacteria were more affected by warming than by changes in FTC frequency. In contrast, fungal community structure and abundance were mostly influenced by FTC frequency, as well as the presence of vegetation cover. The relative densities of several bacterial gene families involved in key steps of the N-cycle were affected by FTCs, while warming had little or no effect. The FTCs and incubation temperature also strongly influenced laccase enzymatic activity in soil. In total, our results suggest that, in addition to climatic warming, increased climatic variability may also have a profound impact on Antarctic microbial communities. Although these effects are difficult to detect with assays of total bacterial community structure, they do become manifest in the analysis of key functional gene densities.

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Responses of Antarctic soil microbial communities and associated functions to temperature and freeze–thaw cycle frequency

I The Environment.- Preface.- Antarctic Coastal Landscapes: Characteristics, Ecology and Research.- The Antarctic Environments and Ecosystems.- Characteristics of Antarctic Coastal regions.- The Former Use of 'Oasis' as a Synonym for Ice-Free Landscapes.- Characteristics of Antarctic Coastal Landscapes.- Localities and Topography.- Soils of Antarctic Coasts.- Conditions for Colonisation of Soils.- Development and Maturation.- Research Programmes and Objectives.- References.- Maritime and Continental Antarctic: The Sites of Investigation in Context 17.- Geography and Geology.- Climate.- The Effects on Soil Ecosystems.- References.- King George Island - South Shetland Islands, Maritime Antarctic.- Geographical Features.- Cartographic and Topographic Features.- Surroundings.- Shores.- The Sea Basin.- Changes of Climate.- Temperature.- Radiation.- Climatic Differentiations.- Climatological Effects.- Periglacial Features and Processes.- Variability in the Terrestrial Ecosystem.- References.- Wilkes Land (Casey Station).- The Windmill Islands - Physical.- Geology and Geomorphology.- Holocene Emergence.- Climate.- References 46.- Dronning Maud Land and Its Environments.- Geographical Zone of Dronning Maud Land.- Climatic Zonations.- Distribution of Mosses, Lichens and Soil Algae.- Soil Properties.- Particle Size Distributions.- Electrical Conductivity and pH(H20).- Water Availability.- Nutrients.- Environmental Monitoring.- Human Activity and Long-Range Dispersal.- References.- II Soils, Soil Development and Soil Properties.- Preface.- Glacial Changes in the Areas of Admiralty Bay, Potter Cove, King George Island, Maritime Antarctica.- Climate Change Indications in the of the Antarctic Peninsula.- Satellite Images and Historical Maps.- Glacier Retreat in Admiralty Bay and Potter Cove.- Tidewater Glaciers.- Glaciers Terminating on Land.- Possible Reasons for the Differences in Glacier Retreat of the Tidewater Glaciers in Admiralty Bay.- Conclusion.- References.- Soils and Soilscapes.- Sites and Analyses.- Soil Conditions.- Windmill Islands (Casey Area).- King George Island (Arctowski Area).- Soil Classifications.- Soilscapes.- Windmill Islands.- King George Island.- Conclusions.- References.- Weathering and Soil Formation.- Sites and Methodology.- Soil Analyses.- Lithology of the Sites and Mineralogy of Soils.- Soil Forming Processes and Their Products.- Weathering, Acidification and Mineral Formation.- Humus Accumulation and Biotic Aggregation.- Podzolisation.- Carbonisation, Salinisation and Alkalisation.- Redoximorphism.- Conclusions.- References.- Refractory Soil Organic Matter - Formation, Accumulation, Translocation and Transformation.- Sites and Analyses.- Soil Organic Matter - Distribution and Accumulation.- Soil Formation and SOM Translocation.- 13C-NMR Spectroscopy.- PyGC/MS Analysis.- Soil Formation and SOM Transformation.- Conclusions.- References 156.- Ornithogenic Ecosystems in the Maritime Antarctic Formation, Development and Disintegration.- Colonisation of Antarctic Coast by Sea Vertebrates.- Marine Vertebrates in the Maritime Antarctic Paleoecosystem.- Colonisation of Land by Sea Vertebrates During Glacial/ Interglacial Cycles.- Impact of Sea Animals on Terrestrial Ecosystem Formation.- Ornithogenic (Penguin) Soils in the Maritime Antarctic.- Mineralisation of Guano.- Ornithogenic Waters.- Phosphatisation - the Main Ornithogenic Soil Forming Process in the Maritime Antarctic.- Ornithogenic Soils of Active Rookeries.- Ornithogenic Soils of Abandoned Rookeries.- Development of Terrestrial Ornithogenic Ecosystems.- Biogeochemical Cycle of Ornithogenic Matter on the Land/Sea Boundary.- References.- III Soil Microbes, Plants and Soil Fauna.- Preface.- Heterotrophic Soil Microbes, Microbial and Enzymatic Activity in Antarctic Soils.- The Microbial Community.- Bacterial Counts.- Bacterial Biomass.- Fungi and Yeasts.- Microbial Activity.- Bacterial Activity.- Turnover Times of Glucose.- Respiration of Glucose.- Biomass Production Based on Glucose Metabolism.- Enzymatic Activity.- CO2 Evolution and O2-Consumption.- Driving Factors of Microbial Activity.- Environmental Conditions.- Dissolved Organic Matter.- Mineralisation of Guano.- References.- Plant Communities on King George Island.- Comments on the Flora.- A Review of Important Plant Communities on King George Island.- Communities of Rock Substrates.- Nitrophobic Communities.- Halophilous and Nitrophilous Communities.- Terricolous Communities.- Communities with Vascular Plants.- Communities with a Predominance of Bryophytes.- Communities with a Predominance of Lichens.- The role of Animals in Antarctic Terrestrial Ecosystems.- Distribution of the Principal Terrestrial Ecosystems.- References.- Plant Communities at Wilkes Land.- Flora and Vegetation of the Windmill Islands.- Geology, Geomorphology and Vegetation Patterns.- Plants in the Terrestrial Ecosystem.- Ecophysiological Adaptations of the Flora.- Environmental Impacts and Conservation Issues.- References.- Plant Communities at Dronning Maud Land.- Vegetation in Dronning Maud Land.- Vascular Plants.- Cryptogamic Organisms.- Moss Habitats and Communities.- Soil Algal Communities in the Vicinities of Syowa Station, East Dronning Maud Land.- References.- Soil Fauna of Antarctic Coastal Landscapes.- Faunal Composition.- Ecology and Physiology.- Interhabitat Dispersal and Population Genetic Structure.- Potential Responses to Environmental Change.- Further Research.- References.- IV Integrating Aspects for Soil Ecology in Antarctic Coastal Landscapes.- Preface.- Soils as Habitats for microorganisms.- The Microbial Environment.- The Stone Sphere.- The Aggregate Sphere.- Resource Competition.- Water as a Controlling Factor.- Consequences of Changing Water Availability.- Osmotic Stress.- Physical Effects on the Habitat While Freezing and Thawing.- Ecological Rating of Habitats - An Example from Antarctic Sites.- Adaptation - A Clue to Survival in Harsh Environments?.- References.- Ecological Classification of Terrestrial Algal Communities in Polar Environments.- Environmental Constraints.- Climate.- Hydrology and Permafrost.- Habitat Classification.- Hydro-Terrestrial Environments.- Terrestrial Environments.- Conclusion.- References.- Plants and Lichens in the Antarctic, Their Way of Life and Their Relevance to Soil Formation.- Vascular Plants.- Immigration and Distribution in Antarctica.- Physiological Properties Allow Existence in Antarctica.- Relevance of Vascular Plants for Soil Formation.- Bryophytes.- Bryophytes, as a Component of Antarctic Vegetation.- Physiological Properties That Enable Bryophytes to Live in Antarctica.- Productivity and Growth.- Growth Forms and Strategies.- Phytomass.- Other Organisms Attached to Bryophytes.- Decomposition and Mineralisation.- Catchment of Debris, Detritus, Airborne Particles, Air Spora and Trace Substances.- Nutrient Cycling.- Lichens.- Floristic Remarks.- Physiological Properties That Enable Lichens to Exist in Antarctica.- Growth and Growth Forms.- Colonisation and Succession.- Relations to the Substratum.- Ion Uptake.- Contribution to Pedogenetic Processes.- Conclusions.- References.- Soil Ecology in Relation to Plant Patterns.- Sites and Environmental Constraints.- Soils - Texture and Nutrients.- Vegetation Patterns.- Relationships Between Soils and Vegetation.- Snow and Water as Structural Components.- Conclusion and Needs for Future Research.- References.- Uses, Preservation and Protection of Antarctic Coastal Regions.- Ecological Background.- Ecosystem Development.- Colonisation by Seabirds and Seals.- Occupation, Uses and Impacts by Man.- Research Installations.- Tourism.- Disturbance and Remediation.- A Terminology for Disturbance and Damage.- Remediation.- Coastal Landscapes and Global Change.- Conservation of Coastal Landscapes.- References.- Concluding Remarks.- Taxonomic Index.- Geographical Index.

Geoecology of Antarctic Ice-Free Coastal Landscapes

A time course study of the fate of glucose, sucrose, and arabitol added to surface soils collected from vegetated and bare sites near Casey Station, Wilkes Land, Antarctica, was performed using gas-liquid chromatography. For both soils, hydrolysis of added sucrose was observed after 24 hours. Following 168 hours incubation at both 5°C and 15°C, hydrolysis of sucrose to glucose and fructose was greater than 95%. Maximum rates of sugar uptake were observed in soils from the vegetated site incubated at 15°C. After 168 hours 44%, 52% and 94% of the added arabitol, glucose and sucrose respectively had been consumed. There did not appear to be any cell-free extracellular enzymatic activity in the soils as levels of added sucrose, trehalose and maltose within soil water extracts showed no change after 168 hours incubation. The results are discussed in relation to earlier work on the microbial activity of Antarctic soils and the sources of carbohydrate input into this ecosystem.

R. Möller

Papers

Rates of soluble carbohydrate utilization in soils from the Windmill Islands Oasis, Wilkes Land, continental Antarctica