Soils into which crop plants root and from which they obtain essential minerals and water contain huge arrays of microbes. Many have highly beneficial effects on crop growth and productivity, others are pathogens causing diseases and losses to yield and quality, a few microbes offer protection from these pathogenic forms and others have little or no effect. These intimate and often complex inter-relationships are being explored with increasing success providing exciting opportunities for increasing crop yields and quality in sustainable harmony with the populations of beneficial soil microbes and to the detriment of pathogens. This book explores current knowledge for each of these aspects of soil microbiology and indicates where future progress is most likely to aid in increasing crop productivity by means which are environmentally benign and beneficial.

Ecological functions and human wellbeing depend on ecosystem services. Among the ecosystem services are provisional (food, feed, fuel, fiber), regulating (carbon sequestration, waste recycling, water cleansing), cultural (aesthetic, recreational, spiritual), and supporting services (soil formation, photosynthesis, nutrient cycling). Many relationships of various degree exist among ecosystem services. Thus, land use and soil management to enhance biospheric carbon sinks for carbon sequestration requires a comprehensive understanding on the effects on ecosystem services. Payments for ecosystem services including carbon pricing must address the relationship between carbon sequestration and ecosystem services to minimize risks of overshoot, and promote sustainable use of land-based carbon sinks for human wellbeing.

Soil Carbon Storage: Modulators, Mechanisms and Modeling takes a novel approach to the issue of soil carbon storage by considering soil C sequestration as a function of the interaction between biotic (e.g. microbes and plants) and abiotic (climate, soil types, management practices) modulators as a key driver of soil C. These modulators are central to C balance through their processing of C from both plant inputs and native soil organic matter. This book considers this concept in the light of state-of-the-art methodologies that elucidate these interactions and increase our understanding of a vitally important, but poorly characterized component of the global C cycle. The book provides soil scientists with a comprehensive, mechanistic, quantitative and predictive understanding of soil carbon storage. It presents a new framework that can be included in predictive models and management practices for better prediction and enhanced C storage in soils. Identifies management practices to enhance storage of soil C under different agro-ecosystems, soil types and climatic conditions Provides novel conceptual frameworks of biotic (especially microbial) and abiotic data to improve prediction of simulation model at plot to global scale Advances the conceptual framework needed to support robust predictive models and sustainable land management practices

Research on decomposer communities of terrestrial ecosystems for a long time has focussed on microbial biomass and gross turnover parameters. Recently, more and more attempts are made to look beyond the biomass, and more specifically determine functions and populations on a smaller scale-in time and space. A multitude of techniques is being improved and developed. Garland and Mills (1991) triggered a series of publications on substrate utilization tests in the field of microbial ecology. Despite several promising results for different applications in different laboratories, many problems concerning the assay and the interpretation of results became evident. After individual discussions on the approach with colleagues from various laboratories we started to plan a workshop on the matter. The response on our first circular was extraordinary, and instead of a small workshop it became a meeting with almost 150 participants. The meeting was named 'Substrate use for characterization of microbial communities in terrestrial ecosystems' (SUBMECO) and was held in Innsbruck, Austria, from Oct. 16-18, 1996. The very focussed scope attracted enthusiastic advocates of the approach, and also serious critics. Some of the topics concerned improvements of current inoculation and incubation techniques, ranging from sample pre-treatment, inoculum density and incubation temperature to statistical data handling. New methods for calculating microbial diversity were proposed, as well as bootstrap methods that allow statistics with many variables on a relatively low number of replicates.

Tropical forest soils contain large pools of carbon, most of which is stored as soil organic matter. In spite of its significant role in the global carbon cycle, the dynamics of tropical soil organic matter, including the soil microbial communities that produce, maintain and decompose it, are poorly understood. This dissertation investigates controls on the structure and biogeochemical functions of soil microbial communities and soil organic matter, using a combination of laboratory experiments and natural gradients present at the Luquillo Critical Zone Observatory. First, we investigate linkages between soil enzyme activities, nutrient availability and plant roots in surface mineral soils through a greenhouse pot experiment. Three subsequent studies "dig deeper", by investigating microbial community structures and functions (carbon, nitrogen and phosphorus cycling capacity) along the upper 1.4 meters of soil profiles. Finally, we use NMR spectroscopy to profile the chemical composition of soil organic matter across various depths, soil and forest types, coupled with additional thermal and chemical analyses to evaluate acid-treatment effects on soil organic matter composition. We find that dynamic microbial communities exist along the upper 1.4 meters of tropical soil profiles and that, on a per biomass basis, subsoil microbial communities have similar capacity to participate in carbon and nutrient mineralization as their surface counterparts. While microbial activity is strongly correlated to soil carbon concentrations and hence energy availability, soil organic matter chemistry appears to be driven by landscape scale factors as well as pit-scale factors. Because even small amounts of active soil carbon below the surface few centimeters of the soil profile could produce significant carbon fluxes over large spatial and temporal scales, models that aim to predict the future changes to the global carbon cycle should begin to consider the capacity for carbon cycling to occur throughout the deep critical zone.