Systems Ecology & Ecological Interactions PDF

Systems ecology & ecological interactions Introduction Ecological systems are the study of the interaction between organisms and their physical environment as an integrated system. Ecological systems consist of all the organisms in an area and the physical environment with which they interact: bioti...

Systems ecology & ecological interactions Introduction Ecological systems are the study of the interaction between organisms and their physical environment as an integrated system. Ecological systems consist of all the organisms in an area and the physical environment with which they interact: biotic & abiotic processes and pools & fluxes. You have a pool of how much biomass is present. The transfer from one pool to another pool is called fluxes. For example, carbon transfer between herbivores and decomposers. The smallest ecosystem is the one on a rock and causes weathering. Different time scales (season, migration of species etc.) influence ecological systems. There is a systems approach; top-down approach; you look at the trophic dynamics. And there is a comparative approach; bottom-up approach; processes are central. State factors are influencing the ecosystems, but they are not influenced by the ecosystems; climate, time, topography, parent material and potential biota. And within an ecosystem there are internal factors that influence the ecosystem Geology, soils and landscapes Form long to short time steps: geological processes, evolutionary processes, migration, succession, season and instantaneous. Generic geological processes – rock cycle Endogenous process happens in the earth and are long term and exogenous happens outside. Lithosphere; plates that move across the earth surface independently. Convection flows in asthenosphere: movement of continents. From exogenous to endogenous: earthquake, volcanism, mountain building and subduction. Orogeny: is the process that creates mountains. Exogenous processes are weathering, erosion, transportation and sedimentation. These are shorter time steps. - Weathering  rock originated in the subsoil not stable at the earth’s surface. Important for landscape forms (morphology). Influence on chemical composition soil. And consequent on nutrient release to vegetation. Weathering is making the portions smaller, rock size reducing. This can be physical (size etc) or chemical (change rock composition). - Erosion  removal of soil particles by abrasive action of: water, wind and ice. Erosion gets the rocks into motion. It’s not the wind itself that erodes but it’s the sand within the wind that erodes. - Transport, physical  particle movement in medium: wind, water and ice. Transport capacity (how much material can it have): velocity, medium and volume. If it’s really windy, it can contain much more particles. - Transport, chemical  weathering product -> (soil) water in solution. Movement op soil water: infiltration and percolation, runoff. Evaporation increases concentration. Difference between climates: dry climate, high concentrations & humid climate, large quantities.  - Sedimentation  dynamic process varying in time and space. Deposition of particles by: reduction of velocity of medium and increased material supply. If the velocity drops then the water can’t hold the material anymore. Origin of Dutch landscapes Quaternary is the fourth period and split into Pleistocene and Holocene. Pleistocene is from 2,5 million years ago up to 11 thousand years and then we move into the Holocene. Ice ages were in the Holocene and the formation of the Alpes in the Pleistocene. In the last 2,5 million years we had cold and warm periods. The cold ones are called ice ages. This shows that the climate is never stable. Due to global cooling down during Tertiary (until 2.6 Ma), the temperature was low and there was an ice cap on south pole and Greenland. When there is a lot of ice, the sun radiation goes straight back into space. The last warm period is Holocene and that’s where we are now. 11,7 thousand years ago was the last ice age. Geological speaking, we must be in the ice ages. The warm periods are much shorter than the cold periods. The warm periods are called interglacial warm period. Landscape origin For the Dutch landscape, Weichselian, Saalian and Elsterian are important. You could say that the Entropocene is above Holocene (new period, discussion). This is the current area. BP means before present. Saalian  the North sea was land. And there was an entire ice sheet above NL. All the rivers in NL tended to go west. An ice sheet is 1-2 kilometer. If it’s moving it forms erosion. The south of the Netherlands was never glaciated. It ended near veluwe, Utrecht and Amsterdam. At the end of an ice scape, water is leaking from tunnels. At the pushed moraine, there was the end with meltwater deposits. Hunnebedden are made of boulder clay. Eemian  sea level rose. Coastline with influence of push moraines, glacial basins fill with sea water and wide river valleys. There was marine deposits with peat. Vegetation cover. Once the push moraine are eroded, we expect the rivers go north. Weichselian  periglacial environment. Nl was a polar desert/tundra environment. Generally speaking, the North sea is 40-50 meter. A polar desert is really dry because it is cold. It was also very windy due to the large climate differences. Due to the polar desert it was an erosion area. There was sedimentation by wind. Transport capacity increases with wind force. Larger particles have shorter distance. They found mammet teeth from this area. This means there was vegetation present, because otherwise there was no food for them. So this means it was beside a desert also tundra, because tundra is livable. Characteristics for Pleistocene in NL  glacial deposits form Saalian: ground moraine (boulder clay), push moraine (hills) and glacial basins (valleys)and outwash plains. Periglacial from Weichselian: cover sand and Loess. Holocene  interglacial period with warmer climate. Sea level rises and the groundwater. Changing vegetation. Important for current landscape: marine clay areas, dunes, river floodplains and bog and fen moor. Man becomes a geological factor. The sea came with 1 kilometer per year so roughly 3 meter per day to the coastline. This is because of the melting ice and the north sea is really shallow. A salt marsh gets flooded once in a while in spring. And the other one, mud bank, is flooded every day. If you don’t maintain a lake it becomes a swamp/ peat. The first layer in the river is called gyttja. The nasty smelly stuff. Peat  peat is accumulation of non-decayed plant material. Grow of vegetable material faster than decay. Stratification as a result of changing vegetation. Watermanagemenbt from 800 to 1500  people took out the water from the peat. This oxidized the lake because all the water will flood out. Because of this the land will go more down towards NAP. Besides this, the sea level rose. Dutchies say we dug under sea level but peat does not grow under sea level. The peat lowers with 0.5-1 cm per year. The sea level rises 0.5 mm per year. Peat is also a massive carbon sink. By draining the peat, CO2 will release. Boulder clay at the bottom  then cover sand  clay/peat Crash course soil science Soil is the transition between atmosphere, lithosphere, biosphere and hydrosphere. It’s about 1-1.5 meter thick. Or the soil concerns the loose material, the very upper part of the earth’s crust to a depth that is important for vegetation. Soil is formed by mineral particles, organic matter, water, air and living organisms. Soil functions: - Production of food and biomass - Conserve and filter elements (e.g., 0drinking water) - Habitat; gene pool - Physical and cultural human environment - Source of raw materials  - CO2 pool (as well source as sink) - Geo heritage (geological and archeological) A cross section of the soil is called a soil profile. The original geological material is called parent material. Every soil layer is called a horizon. The texture is the mixture of the sand and particles. Soil components - Mineral particles  weathering of unconsolidated material. Primary and secondary minerals - Organic matter  2-6% volume. Litter, humus and biomass. Degradation by bio-organisms - Soil water  ecological function. Water quantity depends on texture, structure and quantity organic matter - Soil air  in pores that are not filled with water Gravel and stones  sand  silt  clay or lutum Clay is different from sand. Particles under 2 micrometers. Tetrahedrons and octahedrons. Clay particles are negatively charged. That means that clay is fertile because it is unstable. It’s a cation exchange. For dry summer, clay is better than sand. Because clay has low pores for water drainage. So it stays in place. Geogenesis is the origin of the geological genesis – stratification due to geological deposition. This is peat and the ice capes. Pedogenesis is the whole of processes of soil formation regulated by the effects of place, environment, and history after the material has been deposited. This happens when it stays at its place. Soil forming factors (in ecology they are state factors): 1. Parent material 2. Climate  weathering: decalcification (dissolving CaCO3). Photosynthesis basis process. Formation of humus. Leaching: infiltration of soluble component. In NL we get more rainfall (800 mm) than evaporation (500 mm). so water goes down when looking at the cross section. Really white soil is due to acid flood. This is called Podzolization. Calcification is accumulation of CaCo3 by capillary rise. Salinization is accumulation of salt 3. Topography  determines groundwater flow. 4. Flora and fauna  homogenization: mixing soil material by animal or people (ploughing). 5. Time Climate and global water cycle Systems ecology was invented by Alexander von Humboldt around 1800. He made an expedition to the Andes. He was the first that wrote the world in different plant communities. Climate is the state factor that most strongly governs the global distribution of biomes. Climate is the generally prevailing weather conditions; averaged over a period of at least 30 years. Climate is defined by Earth’s energy balance. The global water cycle and earth’s energy balance are intimately linked. Water and solar energy are essential for functioning of the earth system and determine the distribution of terrestrial biomes. Climate determines the distribution of terrestrial biomes through water content and temperature. Energy balance of sun and earth High temperature of the sun results in emission of high-energy short-wave radiation. This includes the visible light spectrum. The earth is much cooler, so this radiates low energy long waves. This is not visible to the human eye. Long wave radiation is called infra-red. Gasses like CH4, N2O and CO2 absorb mostly long wavelength aka heat. This shows that the heat from the earth itself is mostly absorbed. And this makes life livable, green house effect. The earth’s radiation budget is a concept used for understanding how much energy the earth gets from the sun and how much energy the earth system radiates back to outer space as invisible light. Only 50% is absorbed by the earth surface form the incoming solar radiation. In the long wave processes, earth is reflecting more heat into space than receiving from the sun. this is due to the greenhouse effect. The radiation emitted by the earth is absorbed by the atmosphere and largely bounces back to earth. Only partly goes back to space. When absorbed sunlight and emitted heat balance each other, the earth’s temperature doesn’t change, the radiation budget is in balance. At the top of the atmosphere: + sunlight in – sunlight reflected from clouds/atmosphere – sunlight reflected from surface – IR emission 0  steady state situation, equilibrium temperature is -18 degrees At the earth’s surface: + sunlight absorbed – IR emission + IR back radiation, greenhouse effect – thermals - evapotranspiration 0  equilibrium temperature is 15 degrees Atmospheric and angle effects on solar input at different latitudes. Snow and ice surfaces reflect most of incoming radiation; oceans and land absorb most. Albedo is reflectivity of a surface, expressed as fraction of the incoming light. The albedo of the earth’s land surface varies with the type of material that covers it. Albedo also changes by season. The chemical composition of the atmosphere determines its role in earth’s energy budget. Important energy absorbing gasses: CO2, N2O, CH4, CFC’s. production aerosols (small nuclei that reflect sunlight: atmospheric dust, sea salt (H2SO4) and sulfur emission by volcano’s (H2S) and biological activity in oceans (dimethylsulfide, DMS). Water condensation around aerosols is cloud formation. Clouds  reflection of sunlight AND absorption of heat: - Clouds cool earth’s surface by reflecting incoming sunlight - Clouds warm earth’s surface by absorbing heat emitted from the surface and re-radiating it back down toward the surface - Clouds warm or cool earth’s atmosphere by absorbing heat emitted from the surface and radiating it into space - Clouds warm and dry earth’s atmosphere and supply water to the surface by forming precipitation - Clouds are themselves created by the motions of the atmosphere that are caused by the warming or cooling of radiation and precipitation Net effect of clouds: cooling of the earth but large uncertainties and regional differences and moderation of temperature differences. Colder during the day, warmer during the night. Less warm in summer, less cold in winter. Less hot in tropics and less cold at the poles. Clouds reflect sunlight  cooling  only relevant when the sun shines, so during daytime and in summer. Clouds absorb heat radiation  warming  net impact mainly when the sun does not shine. As heat rises, clouds tend to form at these areas just like the tropics. Here is the heat radiation low. Exchange of absorbed energy The difference between heat and temperature is that heat is the form of energy that transfers from a hot body to a cold body (J). Temperature is the degree of its hotness or coldness (K). four processes of heat loss 1. Conduction  is from molecule to molecule. Is the transfer of heat via direct contact. 2. Convection  warm liquid or gas rises and is replaced by cooler liquid or gas. This results in a continuous circulating pattern or turbulence. 3. Radiation  energy passing from one object to another without a connecting medium, infra- red. 4. Evaporation  chemical energy due to water phase changes and water vapor transfer. Sensible heat is literally the heat that can be felt. It is the energy moving from one system to another that changes the temperature. Latent heat is the heat needed to change from one form of matter to another, which doesn’t change temperature. Heat that changes the temperature is sensible heat, heat that changes the phase from water to gas is latent heat. Decline of air density follows that of pressure : dP/dh = -pg. p = pressure, h = height, p = density, g = gravitational acceleration. Troposphere is heating by long-wave radiation + sensible + latent heat. Stratosphere is heated from top due to absorption of UVR by ozone (O3). The troposphere is the lowest atmospheric layer and contains most of the mass of the atmosphere. The troposphere is heated primarily from the bottom by sensible and latent heat fluxes and by longwave radiation from Earth’s surface. Temperature therefore decreases with height in the troposphere. Above the troposphere is the stratosphere, which, unlike the troposphere, is heated from the top. Absorption of UV radiation by O3 in the upper stratosphere warms the air. Ozone is concentrated in the stratosphere because of a balance between the availability of shortwave UV necessary to split molecules of molecular oxygen (O2) into atomic oxygen (O) and a high enough density of molecules to bring about the required collisions between 22 2. Earth’s Climate System the climate. The sulfur released to the atmosphere by the volcanic eruption of Mount Pinatubo in the Philippines in 1991, for example, caused a temporary atmospheric cooling throughout the globe. Clouds have complex effects on Earth’s radiation budget. All clouds have a relatively high albedo and reflect more incoming shortwave radiation than does the darker Earth surface. Clouds, however, are composed of water vapor, which is a very efficient absorber of longwave radiation. All clouds absorb and re-emit much of the longwave radiation impinging on them from Earth’s surface. The first process (reflecting shortwave radiation) has a cooling effect by reflecting incoming energy back to space. The second effect (absorbing longwave radiation) has a warming effect, by keeping more energy in the Earth System from escaping to space.The balance of these two effects depends on the height of the cloud. The reflection of shortwave radiation usually dominates the balance in high clouds, causing cooling; whereas the absorption and re-emission of longwave radiation generally dominates in low clouds, producing a net warming effect. Atmospheric Structure Atmospheric pressure and density decline with height above Earth’s surface. The average vertical structure of the atmosphere defines four relatively distinct layers characterized by their temperature profiles. The atmosphere is highly compressible, and gravity keeps most of the mass of the atmosphere close to Earth’s surface. Pressure, which is determined by the mass of the overlying atmosphere, decreases exponentially with height. The vertical decline in air density tends to follow closely that of pressure. The relationships between pressure, density, and height can be described in terms of the hydrostatic equation (2.1) where P is pressure, h is height, r is density, and g is gravitational acceleration. The hydrostatic equation states that the vertical change in pressure is balanced by the product of density and gravitational acceleration (a “constant” that dP dh = -rg varies with latitude). As one moves above the surface toward lower pressure and density, the vertical pressure gradient also decreases. Furthermore, because warm air is less dense than cold air, pressure falls off with height more slowly for warm than for cold air. The troposphere is the lowest atmospheric layer and contains most of the mass of the atmosphere (Fig. 2.3). The troposphere is heated primarily from the bottom by sensible and latent heat fluxes and by longwave radiation from Earth’s surface. Temperature therefore decreases with height in the troposphere. Above the troposphere is the stratosphere, which, unlike the troposphere, is heated from the top. Absorption of UV radiation by O3 in the upper stratosphere warms the air. Ozone is concentrated in the stratosphere because of a balance between the availability of shortwave UV necessary to split molecules of molecular oxygen (O2) into atomic oxygen (O) and a high enough density of molecules to bring about the required collisions between atomic. The absorption of UV radiation by stratospheric ozone results in an increase in temperature with height. The ozone layer also protects the biota at Earth’s surface from damaging UV radiation. Biological systems are sensitive to UV radiation because it can damage DNA. The concentration of ozone in the stratosphere has been declining due to the production and emission of CFCs, which destroy stratospheric ozone, particularly at the poles. This results in an ozone “hole,” an area where the transmission of UV radiation to Earth’s surface is increased. Slow mixing between the troposphere and the stratosphere allows CFCs and other compounds to reach and accumulate in the ozone-rich stratosphere, where they have long residence times. Above the stratosphere is the mesosphere, where temperature again decreases with height. The uppermost layer of the atmosphere, the thermosphere, begins at approximately 80km and extends into space. The thermosphere has a small fraction of the atmosphere’s total mass, composed primarily of O and nitrogen (N) atoms that can absorb very shortwave energy, again causing an increase in heating with height (Fig. 2.3). The mesosphere and thermosphere have relatively little impact on the biosphere. Evapotranspiration, the sum of evaporation from surfaces and transpiration, which is the water loss from plants. Temperature commonly decreases with height, because: - The atmosphere is heated from the surface - Rising air expands and cools: adiabatic cooling. Adiabatic process is one that occurs without transfer of heat and matter. - Under ideal circumstances, temperature decrease -10 C/km, dry adiabatic lapse rate - But: smaller decrease in stable atmosphere with warm light air above (night, winter) and in clouds (warming by condensation) - With greater moisture content, more latent heat is released - Result: global mean is -6.4 C/km - In mountains: radiation is absorbed at greater heights  mean is -4.2 C/km Atmospheric circulation: the fundamental cause of atmospheric circulation is the uneven heating of earth’s surface. Atmospheric pressure is mainly caused by weight of overlying air. Wind is air movement, caused by forces of pressure gradient. Surface wind should blow from poles to equator. The atmospheric cell in which the air circulates is called the Hadley cell. However, the upper air is cooled by thermal emission and the cold and heavy air falls down to earth before the poles are reached. As a result, each hemisphere has three cells of circulating air. And wind direction turns by earth rotation from a straight line (Coriolis force). On northern hemisphere: with the clock. On southern hemisphere: against the clock. This has an impact on air and ocean currents. Summary - Vertical air movements result from temperature differences - Horizontal movements result from pressure differences - 3 wind cells per hemisphere  bands of low and high pressure - Coriolis force dictates the direction of air and ocean currents Ocean circulation plays a critical role in heat transfer. Heating and cooling results in vertical water movement. Wind results in horizontal water movement. Transport of energy from equator to the poles. Global temperature is estimated form radiation equilibrium but locally the situation is more complex. The uneven distribution of land and oceans creates an uneven pattern of heating that modifies the general latitudinal trends in climate.  - High pressure over open oceans - Seasonal differences of pressure systems over land - Mountain ranges - Deviates in wind direction  planetary waves. Changes in circulation pattern are referred to as climate modes. When the temperature of the land is higher the moist air the rain shadow effect??????? The average albedo of the earth including both the atmosphere and the surface is about 30%. Albedo: dry soil > wet soil > grasslands > deciduous forests > coniferous forests. Bowen ratio = the ratios sensible : latent heat flux. The Bowen ratio, the ratio of sensible to latent heat flux, determines the strength of the coupling of the water cycle to the energy budget. ‘Bowen ratio determines the strength of the linkage between energy budget and the hydrological cycle, because it is inversely related to the proportion of net radiation that drives water loss from the ecosystem.’ Ratios varies between 0.1 for tropical oceans and 10 for desserts. Surface roughness affects heat exchange: in woods more turbulence than over grass land. Grassland: high albedo, low evaporation and low transmitted heat. Forest: low albedo, high evaporation (lot of leaf area), high transmitted heat (higher surface roughness). Grassland also has higher Bowen ratio, more of the energy exchange results in heating the atmosphere as in the forest most energy goes into evaporation. Summary climate - Climate is defined by earth’s energy balance - The global water cycle and earth’s energy balance are intimately linked - Water and solar energy are essential for the functioning of the earth system and determine the distribution of terrestrial biomes - The balance between incoming and outgoing radiation is zero - Through atmosphere’s chemical composition heat is trapped - The net impact of clouds is a moderation of temperature differences - Atmospheric (and ocean) circulation is the result of a radiation imbalance at the tropics and poles: more incoming energy at the tropics; more outgoing at the poles - In persistent high-pressure regions, precipitation is low - In persistent low-pressure regions, precipitation is high - Topography has an impact on precipitation patterns - Vegetation impacts surface albedo and energy transfer through convection (sensible heat) and evaporation (latent heat flux). Water balance Only 2,5% of the total amount of water is fresh water and 2/3 of that is covered in glaciers and ice caps. 1.3% is surface water of the fresh water, which is the water most available to the ecosystem. Even of that amount, a large part is ice and snow. The oceans are the major source of water. Through evaporation and water vapor transport, water is brought to land where it precipitates. On land it can go to various directions; to vegetation, to glaciers. Then it goes back into the ground and ends up in the ocean. This is also called the hydrological cycle. The water cycle on land starts with precipitation. Water precipitate due to condensation after cooling of water. Cooling by thermal emission gets fog. Cooling by rising, expanding air gets clouds. Why should air rise? (1) Air rises in low pressure systems (warm areas, e.g. tropics and mid latitudes). (2) When warm moist air gets pushed against mountains and they lose their water at the windward side. As a consequence the leeward side (other side of the mountain) receives warm and dry air. This is called rain shadow effect. (3) when warm air is displaced by cool air. This can be observed in two kinds of frontal systems depending on which air mass is moving. At warm fronts, warm air slides over cold air and this produces clouds when warm air replaces cold air by sliding. At cold fronts heavy cold air displaces lighter warm air by pushing it upward. (4) an unstable atmosphere develops when warm light air develops below cold heavy air. this develops above grassland with little turbulent with little vegetation. This results in small pockets of rising air and then the formation of scattered clouds. Positive feedback: 1. Warmer air contains more water 2. Cloud contains more water 3. More condensation = latent heat flux 4. Air heats up 5. Increased moist convergence into the cloud  showers become heavier due to climate change Subtropical oceans are the major source of water vapor. Warm air contains more water vapor. Rising air  cooling  condensation  freezing  precipitation. Precipitation rate increases strongly with temperature. Water and energy budgets are tightly linked and result in large spatial and temporal variability in precipitation. Evaporation is a measure of ecosystem functioning. The correlation between Gross Primary Production and evapotranspiration shows that evaporation is a measure of ecosystem functioning. This is due to evaporation of water and CO2 uptake are both regulated by the stomata of plant leaves. If you look at the regional variation, there is a resemblance between GPP and ET. There is even a correlation between biomass and precipitation. Higher the precipitation, higher the biomass. Precipitation deficit = evaporation – precipitation. In NL 300 mm water capacity is needed. Soil water is almost everywhere limited. Tropical areas have very low water holding capacity due to the very thin top soil. The capillary force is greatest in the smallest pores. These pores will retain water. Bigger pores have more drainage. Hydraulic conductivity measures the speed with which water moves through a porous medium, like soil. In dry soil, water movement is slower. The water retention curve: - Relation between water potential and water content. - Water potential close to 0, the soil is close to saturation. Water is held in soil primarily by capillary forces - As the water content decreases, binding of water is stronger and water potential goes up. Water is strongly bound - When the water potential is less than 10, water drains by gravity. At 10 all water is drained, and this is called field capacity (optimal growth) - If water potential exceeds 1600, the plant starts wilting Temperature and water are the major actors on ecosystems functioning. Runoff is the leftover water that drains from the ecosystem at times when precipitation exceeds evapotranspiration plus increases in water storage. Human activities alter the hydrologic cycle primarily through changes in land cover and use, which affect evapotranspiration and soil water storage. Open oceans Systems ecology studies the interaction between organisms and their physical environment as an integrated system. A biome is a topographic/geographic defined area, in which the species are adapted to and limited by the physical environment. The differences in physical characteristics between water and air result in fundamental differences in structure and functioning of aquatic versus terrestrial ecosystems. One of the most important difference is the density. Due to the greater density of water than air, the physical support for photosynthetic organisms is greater in water than on land. On land plants must overcome gravity. Another one is viscosity. Water has higher viscosity than air, so it is harder for smaller organisms to go through it. So they swim with current. The heat capacity is much bigger in water, so water takes longer to warm up but also to cool down. So the temperature change in water is more gradually than in air. one advantage on survival on land, is that molecules can diffuse easier, so more accessible to organisms. When you’re tiny you have a high volume to body ratio, so more photosynthesis. 95% photosynthesizing organisms in the ocean are uni-cellular (micro algae, phytoplankton). They form the basis of the food chain in the ocean. The next trophic level have to filter these from water, so they are also small organisms. In contrasts, plants on land are often bigger and bigger than the animals that feed on them. In terrestrial systems, plants determine the habitat structure; ocean systems are shaped by physico-chemical gradients (light, nutrients, temperature). The stressfactors on land are temperature, drought and light. Nekton is the collective term of all organisms that can move independently through the water. plankton is unable to do this, they need current to move. The high average turnover time in oceans results in a higher maintenance of animals. Physico-chemical factors 71% of earth is covered by oceans and coastal seas. The difference between terrestrial and marine ecosystems results in a different approach, biogeochemical cycles of elements. Biogeochemistry is the scientific discipline that involves the study of the chemical, physical, geological and biological processes and reactions that govern the composition of the natural environment. Biogeochemistry is the study of the cycles of chemical elements and their interactions with and incorporation into living things, transported through earth scale biological systems in space and through time. The ocean color tells the productivity of the ocean and hence biomass. The distribution of chlorophyll is associated with wind patterns. More detailed distinction between regions based on water quality, light penetration, specific nutrient limitations, temperature: the Longhurst biogeographical provinces. The marine environment can be subdivided in different zones. (1) looking at the distance from the coast. There is difference between coastal and oceanic zones. The oceanic zone starts where the continental shelf ends. (2) light penetration depth. The euphotic zone is the zone where the light is still plentiful for photosynthetic activity. The disphotic zone is the twilight zone. And the aphotic zone is where no light penetrates. (3) subdivide into regions by depth; epipelagic zone (same as photic zone), mesopelagic zone (disphotic zone), bathypelagic zone and abyssopelagic zone. Physico-chemical parameters determining the boundaries of open ocean ecosystems: - Temperature + salinity = density  temperature reduces with increasing salinity. Fresh water runoff results in salinity decrease. Evaporation results in increase in salinity. Thermocline; the depth zone of the most rapid temperature decline. Halocline; the depth zone of the most rapid salinity change. Pynocline; the depth zone of the most rapid density change. This causes a formation of layers due to the variations in temperature, salinity and wind mixing. - Wind + Coriolis force + tidal activity  origin of air circulation: (1) vertical movement due to temperature differences (2) horizontal movement due to pressure differences (3) 3 wind cells per hemisphere with bands with low and high pressure. General flow patterns of surface water controlled by wind and Coriolis forces. The Ekman spiral occurs because of the Coriolis effect. When surface water molecules are moved by the wind, they drag deeper layers of water molecules below them. Like surface water, the deeper water is deflected by the Coriolis effect – to the right in the Northern hemisphere and to the left in the Southern hemisphere. As a result, each successively deeper layer of water moves more slowly to the right or left, creating a spiral effect. Another impact with an up and downwelling  consequently can be observed around low- and high-pressure systems. In a system with low pressure, you have warm rising air that diverges in the upper atmosphere. Whereas you find converging old air in high pressure system. Low pressure is called cyclonic eddy (to the left on NH; to the right on SH). High pressure is called anticyclonic eddy (to the right on NH; to the left on SH). In a cyclonic eddy, surface water moves outward. This results in upwelling of nutrient rich water. Tidal activity delivers energy in the form of high and low water currents. - Nutrient distribution (N, P, Si, Fe)  phosphate (HPO42-) is the ultimate limiting nutrient for plant growth. Nitrate (NO3-) does not limit growth of bluegreen algae, they fix nitrogen. Silicate (H2SiO4) limits the growth of diatoms (the most abundant group of phytoplankton). Nutrients are taken up by phytoplankton in the surface., when they die, they sink to the bottom where remineralization takes place. Nutrients are returned to the surface mixed layer with winter mixing and upwelling. The deep Pacific has more nutrients than the Atlantic, because the waters there have accumulated more nutrients through time. HNLC regions have high nutrients but low chlorophyll. In these regions, activity is limited by iron. Most iron in the ocean is oxidized (Fe3+), which cannot be used. Main source of iron is dessert dust. - Light  water absorbs colors in the red, orange and yellow part of the light spectrum. This leaves behind colors int eh blue part. 480 nm (blue) penetrates deepest into the ocean due to the high energy yield per photon. Coastal waters can also turn greenish or reddish as light bounces off of floating sediments and particles or when blue is absorbed by chlorophyll. Lambert-Beer law; the penetration of light decreases exponentially with depth and is depending on the absorption coefficient of the medium. Iz = Iz0 e-k dz. -> Iz = irradiance at depth z, Iz0 = irradiance at surface, k = extinction coefficient. K depends on the constituents in the water and varies in time and space. maximum mixed layer depth (MLD) typically 20-200 m. thicker (>500) in some special locations: Southern Ocean and northern North Atlantic. Phytoplankton Controlling factors: nutrients, light and temperature. The 4 major phytoplankton groups: 1. Diatoms  relatively large (2-400 micrometer). They produce silica frustules (glass bodies). They need silicate as one of their major nutrients 2. Dinoflagellates  large (5-200 micrometer). Have unique life cycle and can form big blooms in coastal areas 3. Cyanobacteria  small ( 2 NADPH2 + 2 ATP + O2 The dark reaction The dark reaction utilizes reducing equivalents, ATP and CO2 and produces carbohydrates. nCO2 + nAcc + 2n NADPH2 + 2n ATP  carbohydrates. Rubisco can fix both CO2 and O2: - Carboxylase  reaction with CO2 to form sugars. Net fixation of carbon. This is the photosynthetic process. - Oxygenase  reaction with O2, conversion of sugars into CO2. Respiration of 20-40% of the fixed carbon under normal conditions. Under very high light intensity it has a photo- protection mechanism for damage. This is called photorespiration When evolution has invented rubisco this was not an issue. Rubisco was present in cyanobacteria, the start of life on earth. There was only a very high concentration of CO2, no O2. This is an evolutionary accident. If the CO2 pressure goes down, the waist full ratio goes up. If O2 pressure goes up, the waist full ratio goes up. If you increase CO2, oxygenase goes down. Oxygenase is higher at higher temperature. This is the background of the temperature effect on GPP. The answer to the problem of oxygenase activity is PEPcarboxylase as primary CO2-fixing enzyme: C4 metabolism. phosphoenolpyruvate + HCO3- > oxaloacetate + Pi oxaloacetate > malate (during this step is NADH + H+ oxidized to NAD+) malate > pyruvate + CO2 Most plant with C4 metabolism has a characteristic Kranz-anatomy, swollen sheath cells around the vascular bundle. There is also a difference in the anatomy of chloroplasts. Chloroplasts differ between mesophyll and bundle sheet cells. In the bundle sheet cells the grana are absent: recovery of PEP form pyruvate requires ATP. conversion of oxaloacetate into malate requires NADPH (conversion of malate to pyruvate and release of CO2 in the bundle sheet cell, does generate the NADPH again). C4 is mainly found in monocots (grasses). Dicots have a seed structure where the first leaves are twofold. Monocots have a seed structure where the primary leave is a single grass like extinction. Percentage C3 plants increase with altitude. C4 plants have a less negative value of delta 13C (-15) than C3 plants. At high altitude delta 13C is very negative. In the temperate zone the light intensity is limiting, and photorespiration is less of a problem at low temperature, so more C3 plants. C4 metabolism is a tropical metabolism because it is there warmer. Quantum yield model calculates how much carbon can you fix in a unit of light, C4 vs C3. Herbivores are classified at either browser (deer, moose) or grazer (cow, sheep). Browsers are more picky eaters. Grazers are mowing machines. The decline of browser species coincides with the reduction of atmospheric CO2 (which is also one of the causes of C4 metabolism). Maximum diversity during middle Miocene. Brachydont molar for browsers and hypsodont for grazers. 30 million years ago there was no hypsodont molar. High quality food allows you to be small. Low quality food gets you big, because you need a bigger digestive system, and you eat a lot of rubbish because you’re not picky. This also why you need a big teeth structure because you also eat soil etc. The temperature at which C4 metabolism is outperforming C3 depends on the CO2 concentration. A very high CO2 concentration correlates with a higher temperature for the cross-over. The first derivative of the relation between cross-over temperature between C3 and 4 and the Co2 concentration is quite steep. We can expect that with the current rate of change in CO2 concentration the proportion of C4 plants will decrease. We are in C3 territory in NL, except cordgrass growing partially submerged. This plant is limited in his growth period, it’s not a water plant it gets his CO2 not from water. because the tides are not synchronized with day and night, he will not get enough CO2. But this plant is C4 and PEPrubisco has a high affinity for CO2, and therefore it’s a C4 plant. Corn is also a C4 plant. CAM (cacti, succulents) territory is completely dominated by drought. You have also PEPrubisco but he only does this during night. Then the temperature is low to minimize evaporation. They store CO2 in a vacuole. At day, they close their stomata. There is no separation in space only in time. Succulents have a fast water uptake after rain. The surface area volume is low. The productivity compared to C3 and C4 is low. The vacuole offers limited storage capacity. The physical and biochemical limitations of photosynthesis tend to be equalized leading to co- limitation. Physical limitation is CO2 diffusion from stomates into the leaves. Biochemical limitation is the carboxylation rate, light limitation and enzyme limitation. Light use efficiency (LUE) is efficiency of conversion of light to carbon fixation. It can be calculated from the linear part of the light response curve. LUE is almost a constant in C3 plants at low light intensity. Sun plants have a higher respiration rate because of the maintenance of all the high enzyme activity, nevertheless they have also a higher photosynthetic rate. In a vegetation the LUE is constant. There is feedback at the leaf level. There is a balance between physical and biochemical limitations. There is feedback at the canopy level. The highest photosynthetic capacity can be found high in the canopy (where light intensity is highest). Leaves that do not contribute to a positive carbon balance are abscised. For C3 plants, LUE decrease with increasing temperature. C4 is constant. The photosynthetic capacity of a vegetation is adapted to the soil. Photosynthetic capacity depends on nitrogen concentration in leaf. Higher nitrogen means higher photosynthetic rate. Nitrogen is also correlated to stomatal conductance. Photosynthetic capacity and leaf longevity (leaf lifespan) are inversely related. SLA (specific leaf area) is a good indicator of photosynthetic capacity. Higher SLA means higher photosynthetic rate. Thin leaf is high SLA. Thick leaves means more energy to the defense of the leaf. Adaptation to water limitation. Fast response is reduction in stomatal conductance. Long term response is reduction of leaf surface area maintaining high LUE. Important factors influencing GPP is leaf area, length of season in which photosynthetic productivity is possible and photosynthetic rate of individual leaves (capacity and stress). Effects on GPP Effects: leaf surface area, length of growth season and photosynthetic rate of leaf (PS capacity and stresses). Net primary production is GPP minus respiration of plant. Net ecosystem production is related to the net primary production. NEP is GPP minus (all the respiration + disturbance and leaching). The only thing that comes into ecosystem is GPP. Rplant = Rgrowth + Rmaintenance + Rion. Rion = the cost of maintaining gradients across the membranes – these are strongly correlated with NPP. Rmaintenance = the cost for repair/replacement of proteins, membranes etc. – these also correlate with NPP. The cost of growth is about equal for all organs of a plant. NPP is about 50% of GPP. Physiological control of NPP by the plant. It is demand driven. Investment in growth is the sink strength and is directed to where a plant will grow. It is strongly affected by soil parameters (nutrient and water availability). Demand for carbon has strong feedback on photosynthesis and respiration. Climate affects NPP in different ways. It direct affects growth. Long term effects on species composition. There is a trend to co-limitation. Allocation to the roots when nutrients and/or water are limiting. Allocation to the shoot when carbon is limiting. Preventing limitation by a single factor. NPP is rarely limited by a single factor. Because adjustment of allocation, environment varies with the seasons and years, plant influence the availability of their resources and different species differ in their limitations. Advantage of loss of leaves and roots. This makes reallocation possible. Cutting costs when the benefits no longer weigh up to the gains. And they will lose parasites and pathogens. The turn-over depends on tissue and biome. Tropical system has highest turn-over. Not all radiation energy is used by photosynthesis. The excess energy goes to reflection, latent heat and warming of soil and air. primary production decreases with latitude. Higher latitude has less litter production on the ground. Leaf area index (LAI) is how much leaf is present in a square. Vegetation composition determines growth potential. Biomass is largest in tropical and temperate forests. But NPP varies enormously between biomes. Nevertheless, NPP per unit leaf area in a biome is much more constant. net ecosystem production (NEP) is the difference between GPP and respiration of the whole ecosystem. The largest difference in net ecosystem exchange (NEE) of carbon is due to higher respiration at higher latitude. At lower latitude NEE is positive, so they accumulate carbon. Why do we measure positive values for NEE for most ecosystems? - Ecosystems accumulate carbon between disturbances - There is a bias in the measurements towards early successional stages - Carbon leaching is more important than we assume - The earth does currently accumulate carbon in biomass Why do some leaves stay green, and some fall off in the winter? They either allocate their energy to growth or to defense. Investment in defense depends on how vast a plant can grow. For low growth rates, investment in defense is the optimal strategy. Fast growing plants are better off by not investing in defense. Lower growth rate is compensated by longer leaf longevity. Evergreens have an overall low photosynthesis rate but they have a really long lifespan. Annual plants live very short but very active. Evergreen plants is an adaptation to poor nutrient conditions, thus low growth rate, thus more defense. Nutrient cycles The carbon flux differs from nutrient fluxes: carbon assimilation is being limited by vegetation characteristics and photosynthetic capacity. Nutrient assimilation depends largely on nutrient supply. Nutrient use efficiney (NUE); - the physiological approach (plant level)  NUE = a t o a = nutrient productivity (photosynthesis/ gram Nitrogen) o t = residence time of nutrient in the plant - ecosystem approach (vegetation level) o NUE = gram biomass / gram nutrient Nutrient ratios are fairly constant. This means that the availability of the limiting nutrient regulates the uptake of all other nutrients, however ratios do vary somewhat. The minimal variation in ratios implies regulation of the uptake process. Variation in ratios reflects storage of nutrients. A long residence time is an important adaption to nutrient poor conditions. Per plant there is a difference between residence time and nutrient productivity but at the end the NUE is almost equal. How do nutrients end up in the root?  - Diffusion (always from high concentration to low concentration. A low concentration in the root will start diffusion) - Mass flow (dissolved nutrient are transported by flowing water) - Interception (roots grow towards a nutrient patch. This is for nutrients that are adhering to root particles) All three processes depend on root length. An efficient way to increase the effective root length is mycorrhiza. Another way is that the root surface is influencing its surroundings, rhizosphere. Lowering the pH can affect the release of nutrients from soil particles (especially clay and organic particles, these are negatively charged). Iron is mainly present in Fe3+, which is almost insoluble at neutral pH. When lowering the pH, Fe3+ will be more soluble and thus available for root uptake. Increasing the root elongation is the most effective for nutrient uptake. Another way is symbiosis: - Nitrogen fixing bacteria  Nitrogen is most abundant in the atmosphere. This has become available for the ecosystem. There are a few ways. NO3- and NH4+ are the forms that a plant can take up. This comes in the form of thunder where N2 is made into NO2 and then made into NO3-. This not much. Most of the nitrogen enters the system by biological fixation by bacteria and cyanobacteria (prokaryotes). All the fixed nitrogen in an ecosystem comes from this. This happens via symbiosis or free-living bacteria. There is also a biological de-nitrification going on. They live in nodes. The node is red because the root provides them the right oxygen concentration due to hemoglobin. Nitrogenase is oxygen sensitive. Nitrogenase demands a high input of ATP, this is delivered by the plant. In free-living, photosynthesizing (oxygen production) cyanobacteria the nitrogen fixation takes place in heterocysts cells where anoxic conditions can be maintained. - Mycorrhiza  symbiosis of the root with a fungus. It increases the nutrient uptake area. The plant provides the fungus with carbohydrates (4-20% of GPP). The fungus provides the plant with nutrients (P) and water. the fungus infects the root and forms vesicles and arbuscules (little trees) in the root cortex cells. The fungus remains surrounded by the plasma membrane of the cortical cell. Phosphate cycle: phosphate is taken up in one form PO43-. Phosphate comes from soil particles due to weathering. It is lost from the ecosystem by leaching and weathering. Sulfur cycle: sulfur like N can be present in different forms. Sulfur needs to be present to make proteins. It is only present in protein in reduced form SO4-. In the soil it is present as sulfate, SO4+. Decaying of inorganic material gives inorganic sulfate. SO2, H2S and sulfate can be taken up by the plant. The typical smell of the ocean is due to sulfur, most abundant form on earth. Most nutrients that are being taken up by plants have been recycled from the litter layer. Elements are lost from ecosystems by leaching and erosion and for N and S, by losing in gaseous form to the atmosphere. Ecosystem characteristics Tropical rain forest - Constant temperature and precipitation - Rainfall between 250-500 cm - Both sides of the equator - High biodiversity - Always green, many vegetation layers, epifytes (plants without root system) Savanna - Intertropical convergence zone (trade winds, seasonality with 2 rain periods) - Precipitation 30-160 cm (intensely dry periods between rain season) - Dense grassland vegetation and open, fire-tolerant forest - Seasonal grazing and fire Desert - Precipitation less than 10 cm - Large temperature difference between day and night - Rainfall in short, heavy showers - Biodiversity blooms after rainfall. The seeds can stay long in the ground without water Mediterranean shrubland - Between 25-60 cm rain - Adapted to hot summer - Fire - Some seeds only germinate when there is fire, smoke cells. Seeds make use of ashes which contain a lot of nutrients. Deciduous forest - Deciduous, seasonal leaf fall (at rest in winter, in tropics when shortage of water) - 130-200 cm precipitation - 3-18 degrees temperature Grassland - Between 25-100 cm precipitation - Soil is stabilized by grassed and perennial herbs - Climate zone between desert and temperate deciduous forest - Growth of trees and shrubs prevented by grazing, fire and wind - Intercalary meristem is and adaption of grasses to grazing. This sits at the bottom of the leaf. And another one is; the growing tip is hidden and almost below the surface. So new growth can emerge from apex. Taiga  - Boreal conifer (evergreen) forest - -5-4 degrees temperature - 50-200 cm precipitation - Only a few tree species. Tundra - Cold winters and cool summers - Little precipitation