Download 07 Background literature

LPES – Background literature – Ökosysteme und ihre Funktionen
From: Center for Educational Technologies. 2015. Exploring the Environment Project.
Typology of spheres
Everything in Earth's system can be placed into one of four major subsystems: land, water, living things,
or air. These four subsystems are called "spheres." Specifically, they are the "lithosphere" (land),
"hydrosphere" (water), "biosphere" (living things), and "atmosphere" (air).
Lithosphere: The lithosphere contains all of the cold, hard solid land of the planet's crust (surface), the
semi-solid land underneath the crust, and the liquid land near the center of the planet. The surface of
the lithosphere is very uneven. The solid, semi-solid, and liquid land of the lithosphere form layers that
are physically and chemically different. If someone were to cut through Earth to its center, these layers
would be revealed like the layers of an onion. The outermost layer of the lithosphere consists of loose
soil rich in nutrients, oxygen, and silicon. Beneath that layer lies a very thin, solid crust of oxygen and
silicon. Next is a thick, semi-solid mantle of oxygen, silicon, iron, and magnesium. Below that is a liquid
outer core of nickel and iron. At the center of Earth is a solid inner core of nickel and iron.
Hydrosphere: The hydrosphere contains all the solid, liquid, and gaseous water of the planet. It ranges
from 10 to 20 kilometers in thickness. The hydrosphere extends from Earth's surface downward several
kilometers into the lithosphere and upward about 12 kilometers into the atmosphere. A small portion of
the water in the hydrosphere is fresh (non-salty). This water flows as precipitation from the atmosphere
down to Earth's surface, as rivers and streams along Earth's surface, and as groundwater beneath Earth's
surface. Most of Earth's fresh water, however, is frozen. Ninety-seven percent of Earth's water is salty.
Atmosphere: The atmosphere contains all the air in Earth's system. It extends from less than 1 m below
the planet's surface to more than 10,000 km above the planet's surface. The upper portion of the
atmosphere protects the organisms of the biosphere from the sun's ultraviolet radiation. It also absorbs
and emits heat. When air temperature in the lower portion of this sphere changes, weather occurs. As
air in the lower atmosphere is heated or cooled, it moves around the planet. The result can be as simple
as a breeze or as complex as a tornado.
Biosphere: The biosphere (or sometimes also called anthroposphere) contains all the planet's living
things. This sphere includes all of the microorganisms, plants, and animals of Earth. Within the
biosphere, living things form ecological communities based on the physical surroundings of an area.
These communities are referred to as biomes.
Typology of ecosystems
There are essentially two kinds of ecosystems; Aquatic and Terrestrial. Any other sub-ecosystem falls
under one of these two headings.
Terrestrial ecosystems can be found anywhere apart from heavily saturated places. They are broadly
classed into:
1) The Forest Ecosystems: They are the ecosystems in which an abundance of flora, or plants, is
seen so they have a big number of organisms which live in relatively small space. Therefore, in
forest ecosystems the density of living organisms is quite high. A small change in this ecosystem
could affect the whole balance, effectively bringing down the whole ecosystem. You could see a
fantastic diversity in the fauna of the ecosystems, too. They are further divided into:
 Tropical evergreen forest: These are tropical forests that receive a mean rainfall of 80 for
every 400 inches annually. The forests are characterised by dense vegetation which
comprises tall trees at different heights. Each level is shelter to different types of animals.
 Tropical deciduous forest: There, shrubs and dense bushes rule along with a broad selection
of trees. The type of forest is found in quite a few parts of the world while a large variety of
fauna and flora are found there.
 Temperate evergreen forest: Those have quite a few number of trees as mosses and ferns
make up for them. Trees have developed spiked leaves in order to minimize transpiration.
 Temperate deciduous forest: The forest is located in the moist temperate places that have
sufficient rainfall. Summers and winters are clearly defined and the trees shed the leaves
during the winter months.
 Taiga: Situated just before the arctic regions, the taiga is defined by evergreen conifers. As
the temperature is below zero for almost half a year, the remainder of the months, it buzzes
with migratory birds and insects.
2) The Desert Ecosystem: Desert ecosystems are located in regions that receive an annual rainfall
less than 25. They occupy about 17 percent of all the land on our planet. Due to the extremely
high temperature, low water availability and intense sunlight, fauna and flora are scarce and
poorly developed. The vegetation is mainly shrubs, bushes, few grasses and rare trees. The stems
and leaves of the plants are modified in order to conserve water as much as possible. The best
known desert ones are the succulents such as the spiny leaved cacti. The animal organisms
include insects, birds, camels, reptiles all of which are adapted to the desert (xeric) conditions.
3) The Grassland Ecosystem: Grasslands are located in both the tropical and temperate regions of
the world though the ecosystems vary slightly. The area mainly comprises grasses with a little
number of trees and shrubs. The main vegetation includes grasses, plants and legumes that
belong to the composite family. A lot of grazing animals, insectivores and herbivores inhabit the
grasslands. The two main kinds of grasslands ecosystems are:
 Savanna: The tropical grasslands are dry seasonally and have few individual trees. They
support a large number of predators and grazers.
 Prairies: It is temperate grassland, completely devoid of large shrubs and trees. Prairies could
be categorized as mixed grass, tall grass and short grass prairies.
4) The Mountain Ecosystem: Mountain land provides a scattered and diverse array of habitats
where a large number of animals and plants can be found. At the higher altitudes, the harsh
environmental conditions normally prevail, and only the treeless alpine vegetation can survive.
The animals that live there have thick fur coats for prevention from cold and hibernation in the
winter months. Lower slopes are commonly covered with coniferous forests.
The aquatic ecosystem is the ecosystem found in a body of water. It encompasses aquatic flora, fauna
and water properties, as well. There are two main types of aquatic ecosystem:
1) The Marine Ecosystem: Marine ecosystems are the biggest ecosystems, which cover around 71%
of Earth's surface and contain 97% of out planet's water. Water in Marine ecosystems features
in high amounts minerals and salts dissolved in them. The different divisions of the marine
ecosystem are:
 Oceanic: A relatively shallow part of oceans which lies on the continental shelf.
 Profundal: deep or Bottom water.
 Benthic Bottom substrates.
 Inter-tidal: The place between low and high tides.
 Estuaries
 Coral reefs
 Salt marshes
 Hydrothermal vents where chemosynthetic bacteria make up the food base.
Many kinds of organisms live in marine ecosystems: the brown algae, corals, cephalopods,
echinoderms, dinoflagellates and sharks.
2) The Freshwater Ecosystem: Contrary to the Marine ecosystems, the freshwater ecosystem
covers only 0.8% of Earth's surface and contains 0.009% of the total water. Three basic kinds of
freshwater ecosystems exist:
 Lentic: Slow-moving or till water like pools, lakes or ponds.
 Lotic: Fast-moving water such as streams and rivers.
 Wetlands: Places in which the soil is inundated or saturated for some lenghty period of time.
The ecosystems are habitats to reptiles, amphibians and around 41% of the world’s fish species.
The faster moving turbulent waters typically contain a greater concentrations of dissolved
oxygen, supporting greater biodiversity than slow moving waters in pools.
From: Brennan SR, Withgott J. 2007. Environmental systems: Connections, cycles and feedback
Loops. Sections from chapter 6 in Environment: The Science Behind the Stories, published by
Springer, New York.
From: The Concept of the Ecosystem. 2008. The Global Change Project.
Processes of Ecosystems
By definition, all ecosystems cycle matter and use energy, and the processes define the fundamental
ecosystem functions as well. This figure with the plants, zebra, lion, and so forth illustrates the two main
ideas about how ecosystems function: ecosystems have energy flows and ecosystems cycle materials.
These two processes are linked, but they are not quite the same (see Figure 1).
Figure 1. Energy flows and material cycles.
Energy enters the biological system as light energy, or photons, is transformed into chemical energy in
organic molecules by cellular processes including photosynthesis and respiration, and ultimately is
converted to heat energy. This energy is dissipated, meaning it is lost to the system as heat; once it is
lost it cannot be recycled. Without the continued input of solar energy, biological systems would quickly
shut down. Thus the earth is an open system with respect to energy.
Elements such as carbon, nitrogen, or phosphorus enter living organisms in a variety of ways. Plants
obtain elements from the surrounding atmosphere, water, or soils. Animals may also obtain elements
directly from the physical environment, but usually they obtain these mainly as a consequence of
consuming other organisms. These materials are transformed biochemically within the bodies of
organisms, but sooner or later, due to excretion or decomposition, they are returned to an inorganic
state. Often bacteria complete this process, through the process called decomposition or mineralization.
During decomposition these materials are not destroyed or lost, so the earth is a closed system with
respect to elements (with the exception of a meteorite entering the system now and then). The
elements are cycled endlessly between their biotic and abiotic states within ecosystems. Those
elements whose supply tends to limit biological activity are called nutrients.
The Transformation of Energy
The transformations of energy in an ecosystem begin first with the input of energy from the sun. Energy
from the sun is captured by the process of photosynthesis. Carbon dioxide is combined with hydrogen
(derived from the splitting of water molecules) to produce carbohydrates (CHO). Energy is stored in the
high energy bonds of adenosine triphosphate, or ATP. Virtually all energy available to organisms
originates in plants. Because it is the first step in the production of energy for living things, it is called
primary production. Herbivores obtain their energy by consuming plants or plant products, carnivores
eat herbivores, and detritivores consume the droppings and carcasses of us all.
Figure 2 portrays a simple food chain, in which energy from the sun,
captured by plant photosynthesis, flows from trophic level to trophic
level via the food chain. A trophic level is composed of organisms that
make a living in the same way, that is they are all primary producers
(plants), primary consumers (herbivores) or secondary consumers
(carnivores). Dead tissue and waste products are produced at all levels.
Scavengers, detritivores, and decomposers collectively account for the
use of all such "waste" -- consumers of carcasses and fallen leaves may
be other animals, such as crows and beetles, but ultimately it is the
microbes that finish the job of decomposition. Not surprisingly, the
amount of primary production varies a great deal from place to place,
due to differences in the amount of solar radiation and the availability of
nutrients and water. Energy transfer through the food chain is
inefficient. This means that less energy is available at the herbivore level
than at the primary producer level, less yet at the carnivore level, and so
on. The result is a pyramid of energy, with important implications for
understanding the quantity of life that can be supported.
Figure 2. Trophic food chain.
Biogeochemistry
How can we study which of these linkages in a food web are most important? One obvious way is to
study the flow of energy or the cycling of elements. For example, the cycling of elements is controlled in
part by organisms, which store or transform elements, and in part by the chemistry and geology of the
natural world. There are several main principles and tools that biogeochemists use to study earth
systems. The principles and tools that we use can be broken down into 3 major components: element
ratios, mass balance, and element cycling.
1. Element ratios: In biological systems, we refer to important elements as "conservative". These
elements are often nutrients. By "conservative" we mean that an organism can change only slightly the
amount of these elements in their tissues if they are to remain in good health.
2. Mass Balance: Another important tool that biogeochemists use is a simple mass balance equation to
describe the state of a system. The system could be a snake, a tree, a lake, or the entire globe. Using a
mass balance approach we can determine whether the system is changing and how fast it is changing.
The equation is:
NET CHANGE = INPUT + OUTPUT + INTERNAL CHANGE
In this equation the net change in the system from one time period to another is determined by what
the inputs are, what the outputs are, and what the internal change in the system was.
3. Element Cycling: Element cycling describes where and how fast elements move in a system, by terms
of rates (how fast processes occur) and pathways (which processes occur).
From: Von Haaren C. 2004. Landschaftsplanung. Ausschnitte aus Kapitel 5, publiziert von Eugen
Ulmer KG, Stuttgart.
Assessing ecosystem functions, various sources
Biodiversity, Von Haaren, 2004
Natural production function, example 1, Von Haaren, 2004
Beispielmethode
Natural production function, 2, Lavorel et al. 2011
Carbon sequestration, example 1, Burba et al. 2013
Carbon sequestration, example 2, Thüring und Schmid, 2008
Grundwasserneubildung,
Von Haaren, 2004