Alkali soilAlkali, or Alkaline, soils are clay soils with high pH (greater than 8.5), a poor soil structure and a low infiltration capacity. Often they have a hard calcareous layer at 0.5 to 1 metre depth. Alkali soils owe their unfavorable physico-chemical properties mainly to the dominating presence of sodium carbonate, which causes the soil to swell and difficult to clarify/settle. They derive their name from the alkali metal group of elements, to which sodium belongs, and which can induce basicity.
Soil healthSoil health is a state of a soil meeting its range of ecosystem functions as appropriate to its environment. In more colloquial terms, the health of soil arises from favorable interactions of all soil components (living and non-living) that belong together, as in microbiota, plants and animals. It is possible that a soil can be healthy in terms of eco-system functioning but not necessarily serve crop production or human nutrition directly, hence the scientific debate on terms and measurements.
Soil gasSoil gases (soil atmosphere) are the gases found in the air space between soil components. The spaces between the solid soil particles, if they do not contain water, are filled with air. The primary soil gases are nitrogen, carbon dioxide and oxygen. Oxygen is critical because it allows for respiration of both plant roots and soil organisms. Other natural soil gases include nitric oxide, nitrous oxide, methane, and ammonia.
Productivity (ecology)In ecology, the term productivity refers to the rate of generation of biomass in an ecosystem, usually expressed in units of mass per volume (unit surface) per unit of time, such as grams per square metre per day (g m−2 d−1). The unit of mass can relate to dry matter or to the mass of generated carbon. The productivity of autotrophs, such as plants, is called primary productivity, while the productivity of heterotrophs, such as animals, is called secondary productivity.
Economic analysis of climate changeThe economic analysis of climate change explains how economic thinking, tools and techniques are applied to calculate the magnitude and distribution of damage caused by climate change. It also informs the policies and approaches for mitigation and adaptation to climate change from global to household scales. This topic is also inclusive of alternative economic approaches, including ecological economics and degrowth. Economic analysis of climate change is considered challenging as it is a long-term problem and has substantial distributional issues within and across countries.
Sol acide à sulfatesIl existe sur tous les continents des sols dits « sols acides à sulfates ». Ils sont souvent situés en zone sédimentaire proche de l'océan et/ou en arrière-pays de zones ferrugineuses ou latéritiques. Les cultures y sont plus difficiles, et ces sols sont souvent plus vulnérables à l'érosion, à la dégradation et à la salinisation. Ils sont aussi plus vulnérables que les sols basique à de nombreuses pollutions (par les métaux lourds par exemple, qui sont plus mobiles et bioassimilables dans un substrat acide).
Production primaire400px|vignette|Selon les données « couleur de l'océan » recueillies par le capteur SeaWiFS, la production primaire dans l'océan mondial est sensiblement égale à celle sur les terres émergées, bien que la biomasse primaire océanique soit environ 500 fois moins importante que la biomasse terrestre, ce qui traduit la très grande efficacité du phytoplancton océanique (avec notamment les diatomées qui représentent 40 % de la production primaire des écosystèmes marins).
Agricultural productivityAgricultural productivity is measured as the ratio of agricultural outputs to inputs. While individual products are usually measured by weight, which is known as crop yield, varying products make measuring overall agricultural output difficult. Therefore, agricultural productivity is usually measured as the market value of the final output. This productivity can be compared to many different types of inputs such as labour or land. Such comparisons are called partial measures of productivity.
Soil chemistrySoil chemistry is the study of the chemical characteristics of soil. Soil chemistry is affected by mineral composition, organic matter and environmental factors. In the early 1870s a consulting chemist to the Royal Agricultural Society in England, named J. Thomas Way, performed many experiments on how soils exchange ions, and is considered the father of soil chemistry. Other scientists who contributed to this branch of ecology include Edmund Ruffin, and Linus Pauling.
Attribution du changement climatique récentL'attribution du changement climatique récent est le travail entrepris pour déterminer scientifiquement les mécanismes responsables du réchauffement climatique récent et des changements climatiques induits sur la Terre. L’effort s’est concentré sur les changements observés au cours de la période de relevés de température instrumentale, en particulier au cours des cinquante dernières années. C’est la période durant laquelle l’activité humaine a connu la croissance la plus rapide et pour laquelle on dispose de relevés atmosphériques au-dessus de la surface.
