Störning av terrestra ekosystem Flashcards
Are terrestrial ecosystems diverse?
Yes, their soils and vegetation are influenced by climate.
What functions for humans does terrestrial ecosystems fulfill?
Providing food, building material, clothing
Regulating water and air quality, erosion
Providing space for recreation and inspiration
Central role in biogeochemical cycles, for instance that of carbon
Are terrestrial ecosystems dynamic?
Yes, they change naturally
Are terrestrial ecosystems influenced by global change?
Yes, for instance:
Changes in vegetation distribution by land use change and climate change
Increase in plant productivity by warming and increasing carbon dioxide
But also: Increases in fires, droughts, hurricanes, etc.
Do terrestrial ecosystems influence the global climate?
Yes, for instance:
Uptake of atmospheric carbon dioxide by plants
Release of greenhouse gases to the atmosphere, such as carbon dioxide by respiration or fires
Reflection of radiation - albedo
What are global distribution of different biomes and the main climatic drivers behind?
There are different vegetation types in different climate zones. Forests are located where there is enough water. Non-forested vegetations are located where it is too dry, cold and/or wet for forests to grow. Tropical desert -> Evergreen forests.
The main climatic drivers are precipitation and air temperature.
What are the main components of soil and main factors influencing soil formation?
The main components of soil are:
Minerals
Organic substances derived from dead organisms
Water
Gases such as O2, N2, CO2, and CH4
Soil organisms such as microorganisms, soil animals, fungi, and plant roots.
The main factors influencing soil formation are:
Time (how long does the degradation occur?)
Organisms
Parent rock
Topography
Climate
What are ecosystem services?
Ecosystem services are benefits that society derives from ecosystems. A few examples are pollination, food, raw materials, and water and air purification.
What are the orders of magnitudes of photosynthesis, respiration and fossil fuel emissions?
Photosynthesis and respiration have the magnitudes of over 100 Pg C/yr, while fossil fuel emissions have the order of magnitude of about 10 Pg C/yr.
What are global distribution of high/low land primary production, respiration and soil carbon?
Primary production (total carbon uptake by plants): Highest in the tropics, none to little in the deserts, and moderate in the mid latitudes.
Respiration (carbon release from soils): Highest in the tropics, low in mid Asia, and high in Europe and east North America.
Soil carbon turnover (how fast carbon is released after uptake): Slowest turnover at high latitude and in mountain areas, high in the tropics.
What is a disturbance? Examples?
A disturbance in a discrete event that removes plant biomass, for example fires, floods, hurricanes, herbivore outbreaks, glacial outbreaks, glacial advances, and volcanic eruptions.
What is succession? What is the difference between primary and secondary succession?
Succession is the process by which the structure of a biological community changes over time.
Primary succession occurs after severe disturbances that remove or bury most products of ecosystem processes, e.g. after lava flows, glacier retreat, and on new sand dunes. Takes hundreds to thousands of years.
Secondary succession occurs after moderate disturbances, and begins on soils that developed beneath vegetation, e.g. after fires. Takes hundreds of years.
What is land use change? Examples? Main drivers?
Land use change describes a change in how a piece of land is used by humans.
Examples are conversion of forest to cropland, conversion of forest to pastures, drainage of wetlands and conversion to cropland, intensification of agriculture, spread of urban areas into agricultural land, abandonment of pastures, and reforestation of pastures.
The main drivers behind land use change are population growth and technological development leading to change in practices.
What is deforestation? Afforestation? Reforestation?
Deforestation is the removal of forest with conversion of land to non-forest use.
Afforestation is the establishment of forests where there was no forest before.
Reforestation is the natural or intentional restocking of depleted forests.
What is the global distribution of deforestation and its impact on carbon cycling?
Deforestation occurs mainly in South America and Africa.
Forests take up a lot of carbon from the atmosphere, and deforestation itself leads to high carbon emissions. Since land carbon uptake is highest in the tropics, deforestation in the tropics reduces carbon dioxide uptake from the atmosphere.
