The cycling of carbon, nitrogen, and other nutrients through vegetation and soils has major effects on global-scale climate, agricultural productivity, and natural ecosystem dynamics. The release of carbon dioxide from soil organic matter mineralization actively contributes to global climate change, while the availability of nutrients (nitrogen and phosphorus in particular) in the soil constrains vegetation growth. A proper management of soil carbon and nutrient dynamics may allow reducing carbon emissions to the atmosphere, and optimizing agricultural production. For soil management to be successful there is a need for a quantitative understanding of soil carbon and nutrient processes. Mathematical models have thus been developed to describe soil processes at spatial scales ranging from few microns to thousands of kilometers and temporal scales spanning seconds to centuries. In this dissertation, the theory behind these mathematical models is critically revisited and extended to explore the mathematical and practical limitations of some model formulations and to unify different theoretical approaches. The main focus is on the effects of climatic variables and stoichiometric constraints on soil and plant residue decomposers, which are the predominant drivers of carbon and macro-nutrient mineralization from plant residues and soil organic matter. More specifically, the results suggest that nonlinear decomposition models are best suited to quantify carbon dynamics at short time scales where the interactions between the decomposers and their substrate is stronger, while linear models can be used at longer scales. Linear stability analysis of the nonlinear models also demonstrated that the climatic factors control the dynamic behavior of the soil system. Nutrient dynamics are tightly coupled to carbon evolution in soils and decomposing plant residues. Such coupling is primarily regulated by the stoichiometric requirements of the decomposers, which are shown to be more important than climatic variables in shaping the global scale patterns of accumulation and release of nitrogen and phosphorus in decomposing plant residues. A major consequence of these stoichiometric constraints is that decomposer respiration rates tends to increase in response to low nutrient content of the residues, suggesting that mechanisms of carbon overflow may be more important than currently thought.

By combining the analysis of biotic and abiotic components of terrestrial ecosystems, this book synthesizes material on arid and semiarid landscapes, which was previously scattered among various books and journal articles. It focuses on water-limited ecosystems, which are highly sensitive to fluctuations in hydrologic conditions and, in turn, play an important role in affecting the regional water cycle. Intended as a tool for scientists working in the area of the earth and environmental sciences, this book presents the basic principles of eco-hydrology as well as a broad spectrum of topics and advances in this research field. Written by authors with diverse areas of expertise who work in arid areas around the world, the contributions describe the various interactions between the biological and physical dynamics in dryland ecosystems, ranging from basic processes in the soil-vegetation-climate system, to landscape-scale hydrologic and geomorphic processes, ecohydrologic controls on soil nutrient dynamics, and multiscale analyses of disturbances and patterns

Wetlands are very sensitive ecosystems, functioning as a habitat for many organisms. Protection and regeneration of wetlands are of great importance in ecological research and in nature conservation. A huge amount of research has been done on the hydrology, plants and animals in wetlands. Knowledge about soil organisms and soil ecological processes of wetlands is still lacking. This knowledge is a prerequisite for landscape planning purposes or climate change predictions. In the case of climate change, trace gas emissions from wetlands are of great interest. The authors provide an overview of the state-of-the-art on soil ecology in wetlands. The book is divided into the following main chapters: 'Wetlands as habitats for soil organisms', 'Soil ecological processes in fens and floodplains', 'Carbon and nitrogen dynamics in soils with different water regimes' and 'Trace gas emissions'.

Phosphorus (P) is a finite resource which is essential for life. It is a limiting nutrient in many ecosystems but also a pollutant which can affect biodiversity in terrestrial ecosystems and change the ecology of water bodies. This book collects the latest information on biological processes in soil P cycling, which to date have remained much less understood than physico-chemical processes. The methods section presents spectroscopic techniques and the characterization of microbial P forms, as well as the use of tracers, molecular approaches and modeling of soil-plant systems. The section on processes deals with mycorrhizal symbioses, microbial P solubilization, soil macrofauna, phosphatase enzymes and rhizosphere processes. On the system level, P cycling is examined for grasslands, arctic and alpine soils, forest plantations, tropical forests, and dryland regions. Further, P management with respect to animal production and cropping, and the interactions between global change and P cycling, are treated.

Litter Decomposition describes one of the most important processes in the biosphere - the decay of organic matter. It focuses on the decomposition process of foliar litter in the terrestrial systems of boreal and temperate forests due to the greater amount of data from those biomes. The availability of several long-term studies from these forest types allows a more in-depth approach to the later stages of decomposition and humus formation. Differences between the decay of woody matter and foliar litter is discussed in detail and a different pattern for decomposition is introduced. While teachers and students in more general subjects will find the most basic information on decomposition processes in this book, scientists and graduate students working on decomposition processes will be entirely satisfied with the more detailed information and the overview of the latest publications on the topic as well as the methodological chapter where practical information on methods useful in decomposition studies can be found. Abundant data sets will serve as an excellent aid in teaching process and will be also of interest to researchers specializing in this field as no thorough database exists at the moment. Provides over 60 tables and 90 figures Offers a conceptual 3-step model describing the different steps of the decomposition process, demonstrating changes in the organic-chemical structure and nutrient contents Includes a synthesis of the current state of knowledge on foliar litter decomposition in natural systems Integrates more traditional knowledge on organic matter decomposition with current problems of environmental pollution, global change, etc. Details contemporary knowledge on organic matter decomposition

Ecological stoichiometry concerns the way that the elemental composition of organisms shapes their ecology. It deals with the balance or imbalance of elemental ratios and how that affects organism growth, nutrient cycling, and the interactions with the biotic and abiotic worlds. The elemental composition of organisms is a set of constraints through which all the Earth’s biogeochemical cycles must pass. All organisms consume nutrients and acquire compounds from the environment proportional to their needs. Organismal elemental needs are determined in turn by the energy required to live and grow, the physical and chemical constraints of their environment, and their requirements for relatively large polymeric biomolecules such as RNA, DNA, lipids, and proteins, as well as for structural needs including stems, bones, shells, etc. These materials together constitute most of the biomass of living organisms. Although there may be little variability in elemental ratios of many of these biomolecules, changing the proportions of different biomolecules can have important effects on organismal elemental composition. Consequently, the variation in elemental composition both within and across organisms can be tremendous, which has important implications for Earth’s biogeochemical cycles. It has been over a decade since the publication of Sterner and Elser’s book, Ecological Stoichiometry (2002). In the intervening years, hundreds of papers on stoichiometric topics ranging from evolution and regulation of nutrient content in organisms, to the role of stoichiometry in populations, communities, ecosystems and global biogeochemical dynamics have been published. Here, we present a collection of contributions from the broad scientific community to highlight recent insights in the field of Ecological Stoichiometry.