Humans are altering the composition of biological communities through a variety of activities that increase rates of species invasions and species extinctions, at all scales, from local to global. These changes in components of the Earth's biodiversity cause concern for ethical and aesthetic reasons, but they also have a strong potential to alter ecosystem properties and the goods and services they provide to humanity. Ecological experiments, observations, and theoretical developments show that ecosystem properties depend greatly on biodiversity in terms of the functional characteristics of organisms present in the ecosystem and the distribution and abundance of those organisms over space and time. Species effects act in concert with the effects of climate, resource availability, and disturbance regimes in influencing ecosystem properties. Human activities can modify all of the above factors; here we focus on modification of these biotic controls. The scientific community has come to a broad consensus on many aspects of the re- lationship between biodiversity and ecosystem functioning, including many points relevant to management of ecosystems. Further progress will require integration of knowledge about biotic and abiotic controls on ecosystem properties, how ecological communities are struc- tured, and the forces driving species extinctions and invasions. To strengthen links to policy and management, we also need to integrate our ecological knowledge with understanding of the social and economic constraints of potential management practices. Understanding this complexity, while taking strong steps to minimize current losses of species, is necessary for responsible management of Earth's ecosystems and the diverse biota they contain.

/pdf/effects-of-biodiversity-on-ecosystem-functioning-a-consensus-13j8vabcus.pdf

Effects of biodiversity on ecosystem functioning: a consensus of current knowledge

Significantly more carbon is stored in the world's soils--including peatlands, wetlands and permafrost--than is present in the atmosphere. Disagreement exists, however, regarding the effects of climate change on global soil carbon stocks. If carbon stored belowground is transferred to the atmosphere by a warming-induced acceleration of its decomposition, a positive feedback to climate change would occur. Conversely, if increases of plant-derived carbon inputs to soils exceed increases in decomposition, the feedback would be negative. Despite much research, a consensus has not yet emerged on the temperature sensitivity of soil carbon decomposition. Unravelling the feedback effect is particularly difficult, because the diverse soil organic compounds exhibit a wide range of kinetic properties, which determine the intrinsic temperature sensitivity of their decomposition. Moreover, several environmental constraints obscure the intrinsic temperature sensitivity of substrate decomposition, causing lower observed 'apparent' temperature sensitivity, and these constraints may, themselves, be sensitive to climate.

/pdf/temperature-sensitivity-of-soil-carbon-decomposition-and-5ewzh1kof4.pdf

Temperature sensitivity of soil carbon decomposition and feedbacks to climate change

As the largest pool of terrestrial organic carbon, soils interact strongly with atmospheric composition, climate, and land cover change. Our capacity to predict and ameliorate the consequences of global change depends in part on a better understanding of the distributions and controls of soil organic carbon (SOC) and how vegetation change may affect SOC distributions with depth. The goals of this paper are (1) to examine the association of SOC content with climate and soil texture at different soil depths; (2) to test the hypothesis that vegetation type, through patterns of allocation, is a dominant control on the vertical distribution of SOC; and (3) to estimate global SOC storage to 3 m, including an analysis of the potential effects of vegetation change on soil carbon storage. We based our analysis on .2700 soil profiles in three global databases supplemented with data for climate, vegetation, and land use. The analysis focused on mineral soil layers. Plant functional types significantly affected the vertical distribution of SOC. The per- centage of SOC in the top 20 cm (relative to the first meter) averaged 33%, 42%, and 50% for shrublands, grasslands, and forests, respectively. In shrublands, the amount of SOC in the second and third meters was 77% of that in the first meter; in forests and grasslands, the totals were 56% and 43%, respectively. Globally, the relative distribution of SOC with depth had a slightly stronger association with vegetation than with climate, but the opposite was true for the absolute amount of SOC. Total SOC content increased with precipitation and clay content and decreased with temperature. The importance of these controls switched with depth, climate dominating in shallow layers and clay content dominating in deeper layers, possibly due to increasing percentages of slowly cycling SOC fractions at depth. To control for the effects of climate on vegetation, we grouped soils within climatic ranges and compared distributions for vegetation types within each range. The percentage of SOC in the top 20 cm relative to the first meter varied from 29% in cold arid shrublands to 57% in cold humid forests and, for a given climate, was always deepest in shrublands, inter- mediate in grasslands, and shallowest in forests ( P , 0.05 in all cases). The effect of vegetation type was more important than the direct effect of precipitation in this analysis. These data suggest that shoot/root allocations combined with vertical root distributions, affect the distribution of SOC with depth. Global SOC storage in the to p3mo fsoil was 2344 Pg C, or 56% more than the 1502 Pg estimated for the first meter (which is similar to the total SOC estimates of 1500-1600 Pg made by other researchers). Global totals for the second and third meters were 491 and 351 Pg C, and the biomes with the most SOC at 1-3 m depth were tropical evergreen forests (158 Pg C) and tropical grasslands/savannas (146 Pg C). Our work suggests that plant functional types, through differences in allocation, help to control SOC distributions with depth in the soil. Our analysis also highlights the potential importance of vegetation change and SOC pools for carbon sequestration strategies.

The vertical distribution of soil organic carbon and its relation to climate and vegetation

Globally, soil organic matter (SOM) contains more than three times as much carbon as either the atmosphere or terrestrial vegetation. Yet it remains largely unknown why some SOM persists for millennia whereas other SOM decomposes readily—and this limits our ability to predict how soils will respond to climate change. Recent analytical and experimental advances have demonstrated that molecular structure alone does not control SOM stability: in fact, environmental and biological controls predominate. Here we propose ways to include this understanding in a new generation of experiments and soil carbon models, thereby improving predictions of the SOM response to global warming.

/pdf/persistence-of-soil-organic-matter-as-an-ecosystem-property-ago0khy192.pdf

Persistence of soil organic matter as an ecosystem property

Birch, L. C. 1955. Selection in Drosophlila pseudoobscura in relation to crowding. Evolution 9:389399. . 1960. The genetic factor in population ecology. Amer. Nat. 94:5-24. Boggild, O., and J. Keiding. 1958. Competition in house fly larvae. Experiments involving a DDT-resistant and susceptible strain. Oikos 9:1-25. Hiroyoshi, T. 1961. The linkage map of the house fly, Musca domestic L. Genetics 46:1373-1380. Kollros, C. L. 1944. A study of the gene, pearl, in populations of Tribolium castaneumn, Herbst. Unpublished Ph.D. dissertation, University of Chicago.

https://www.fcnym.unlp.edu.ar/catedras/ecocomunidades/Descomposicion%20-%20Guia%20de%20TP.pdf

Energy Storage and the Balance of Producers and Decomposers in Ecological Systems

Factors of Soil Formation

Factors of soil formation : a system of quantitative pedology / Hans Jenny ; foreword by Ronald Amundson. p. cm. Originally published: New York : McGraw-Hill, 1941. With new foreword. Includes bibliographical references and index. not include the modern Dover Press Forward, which is not public domain material.

Factors of Soil Formation: A System of Quantitative Pedology

1. Ecosystems and Soils.- A. Concept of Ecosystem.- B. Soil as an Object of Nature.- C. Soil Colors and Soil Particles.- D. Soil Taxonomy and Classification.- E. Review of Chapter.- References.- A. Processes of Soil Genesis.- 2. Water Regimes of Soils and Vegetation.- A. Soil, a Climostat.- B. Gravitational Potential of Water.- C. Sorptive Potential of Water.- D. Matric Potential of Water.- E. Capillary Phenomena.- F. Osmotic Potential.- G. Summation of Potentials.- H. Movement of Water.- I. Flow of Water through the Ecosystem.- J. Soil Water for Plants.- K. Evapotranspiration and Water Balance.- L. Review of Chapter.- References.- 3. Behavior of Ions in Soils and Plant Responses.- A. Biological Elements.- B. Ions in Rock and Soil Crystals and in Solutions.- C. Exchangeable Ions and Ion Exchange.- D. Ion Currents by Diffusion.- E. Oxidation-Reduction Potentials.- F. Aspects of Plant Nutrition in Soils.- G. Problems of Soil Acidity.- H. Mineral Cycling.- I. Limiting Factor or Performance Equations.- J. Review of Chapter.- References.- 4. Origin, Transformation, and Stability of Clay Particles.- A. Six Common Primary Silicate Minerals.- B. Weathering and Neogenesis of Clays.- C. The Structural Kinship of Micas and Clays.- D. Clay Sequences.- E. Solubilities and Stability Fields of Clays.- F. Clays as Initiators of Organic Evolution.- G. Review of Chapter.- References.- 5. Biomass and Humus.- A. Carbon Fixation.- B. Respiration, the Energy Supplier of Soil Organisms.- C. Vegetation Productivities.- D. Nitrogen Fixation.- E. Soil Organisms as Decomposers and Porositors.- F. Soil Organic Matter and Humus.- G. Nitrogen in Humus and Its Availability.- H. Steady-State Formulations.- I. Review of Chapter.- References.- 6. Soil Colloidal Interactions and Hierarchy of Structures.- A. Flocculation and Deflocculation.- B. Mutual Interactions of Unlike Particles.- B. Peds, Crusts, and Voids.- D. Swelling, Shrinking, and Their Turbations.- E. Review of Chapter.- References.- 7. Pedogenesis of Horizons and Profiles.- A. Transport Considerations.- B. Clay Migration.- C. Mottling, Gleyzation, and Concretions.- D. Podzolization.- E. Laterization.- F. The Pedocal Process.- G. Stone Lines and Stone Pavements.- H. Depth Functions of Organic Matter.- I. Review of Chapter.- References.- B. Soil and Ecosystem Sequences.- 8. State Factor Analysis.- A. Derivation of State Factor Formula.- B. Extended Equation.- C. Commentary to the Formula.- D. Ordination of Ecosystems According to State Factors.- E. Factor Variation.- F. Review of Chapter.- References.- 9. The Time Factor of System Genesis.- A. Nature of Chronosequences.- B. Buildup and Decline of Organic Matter in Chronosequences.- C. Leaching of Carbonates.- D. Clay Formation and Profile Features.- E. Pygmy Forest Ecological Staircase.- F. Chronosequences and Plant Succession Theories.- G. Review of Chapter.- References.- 10. State Factor Parent Material.- A. Conceptual Topics.- B. A Primer of Rock Compositions.- C. Soils Derived from Igneous Rocks.- D. The Serpentine Syndrome.- E. Diversity of Limestone-Derived Soils.- F. Glacial Till Variations.- G. Loess Influx Sequences.- H. Review of Chapter.- References.- 11. State Factor Topography.- A. Points of Compass Orientation.- B. Ridge and Trough Configurations.- C. Toposequences on Slopes.- D. Salt-Affected Soils.- E. Soil Erosion.- F. Review of Chapter.- References.- 12. State Factor Climate.- A. Climatic Indices.- B. Altitude Sequences.- C. The Humus-Climate Paradigm.- D. Precipitation, Base Status, and Carbonate Regimes.- E. Climate and Clay Features.- F. Review of Chapter.- References.- 13. Biotic Factor of System Genesis.- A. Formulation of Biotic Factor Sequences.- B. Partitioning Biotic Factor and Environment.- C. Plant-Controlled Initiation of Ecosystem Genesis.- D. Trees in Forests.- E. Prairie-Forest Biosequences.- F. Animal Activities and Impact by Man.- G. Review of Chapter.- References.- 14. Integration of Factors and Overview of Book.- A. Integration of Factors.- B. Overview of Book.- C. Review of Chapter.- References.- Appendix I. Names of Vascular Species Cited.

Hans Jenny

Papers

Factors of Soil Formation

Factors of Soil Formation: A System of Quantitative Pedology

The Soil Resource: Origin and Behavior

The soil resource.

Comparative Study of Decomposition Rates of Organic Matter in Temperate and Tropical Regions