Taxonomic and Physiognomic Classification

Environmental Systems Final Exam Questions for studying: Topic 1 Part 1 and 2 - What is the difference between taxonomic and physiognomic classification? (provide an example of each, recognize each when an example is given) - Can you describe, define and recognize the layers of vegetation in a forest? - Can you define and differentiate the following? Tree, shrub, liana, herbaceous, forb, graminoid, epiphyte, arboreal Broadleaf tree, needle leaf tree Deciduous, evergreen Annual, perennial Forest, woodland - Where does water enter a plant? Where is it lost? - What strategies (adaptations) help plants reduce water loss? - How would you characterize a xerophytic plant? Part 3 - Can you describe and compare the basic climate, vegetation and soil characteristics of the following biomes, highlighting the differences among them and indicate where they are on a map of the world? 1. Desert 2. Tropical rain forest 3. Mid-latitude broadleaf and mixed forest 4. Boreal forest (needle leaf) 5. Mediterranean shrubland 6. Tundra - What strategy for avoiding moisture stress is typical of the Mediterranean shrubland? - Can you describe the pattern of vegetation change on the North American continent from east to west at approx.. 40 degree latitude? - How are transitions in vegetation communities with latitude and altitude similar? Why? Can you give examples of the vegetation changes? Topic 2 - Can you explain the difference between primary and secondary succession? - What environmental changes occur during succession? - What is meant by the expression climax vegetation? - çHow are some ecosystems resistant or resilient? - What is a paradigm? - Can you provide a definition of niche? - Can you describe the process of secondary succession in : Mid-latitude broadleaf deciduous forest The equatorial rain forest In the boreal forest - Which types of succession support the theory of succession leading to climax vegetation? - Which examples of succession leading to climax vegetation? Energy flow - How is productivity measured - Why is there less energy available at the top of a food chain than at the bottom the beginning? - Why do some say that the earth can support less carnivores than herbivores? - Consider two food chains of unequal length, both start with plants containing equal amount of the pesticide DDT. Ath the top of which food chain would you expect to find higher levels of DDT : the shorter or the longer? Why? - Define the terms Producer Autotroph Carnivore Food web Decomposer Detritivore Herbivore Heterotroph Food chain Trophic level Detritus Compensation point Consumer (primary, secondary) Primary productivity Net primary productivity Biological amplification/magnification - Describe the process of photosynthesis. Where does it occur? What are the inputs and outputs of photosynthesis? - What are the inputs and outputs of respiration? - Can you rank the biomes in terms of their net primary productivity - Can you describe the global cycle of carbon including the major C sinks and sources? - Can you make a diagram showing major flows and storage? - Can you explain the recent increase of carbon dioxide in our atmosphere and greenhouse warming? - Why is the Mauna Loa co2 curve not a smooth line? Impact of global climate change on natural carbon sinks and penguins - How has climate warming affected population of the adelie and Emperor penguins of antartica? - How might increases in temp, atmospheric concentration of carbon dioxide and human disturbances affecting the relative abundance of lianas and trees in the tropical forest and what does it mean in terms of carbon storage and cycling? - How might increased temperatures affect fire frequency in the boreal forest region its carbon stocks and cycling? - How might increased temperature in artic tundra affect carbon storage and greenhouse gas emissions there? - What is the likely fate of tundra ponds with increased temperatures? Coastal and cultural eutrophication and case studies - What groups of organisms are the primary producers in estuaries and the ocean? - Can you define eutrophication? - What is meant by the term limiting nutrient? - Can you provide examples of point and non point sources o nitrogen pollution? - What different changes can occur in estuaries as a result of eutrophication? - Examples will be given in 4 case studies representing various times, temporal scales, spatial scales and severity Topic 1, Part 1- Describing vegetation - - Biogeography: the study of organisms (that is, plants and animals) the diverse spatial patterns they create and the physical and biological processes, past and present, that produce Earth’s species richness. Biogeographers: work at the interface of several disciplines: ecology, geology, paleontology, climatology, limnology, oceanology Phytogeographers (plants), zoogeographers (animals) Historical biogeography: reconstructing the origin, dispersal, and extinction of taxa and biotas Ecological biogeography: accounting for present distributions in terms of interactions between organisms and their physical and biotic environments Paleoecology: relationship between organisms and past environments Classification - Groups similar things - Helps us to see relationships and patterns - By observing patterns, we can often determine factors that control their distribution Taxonomic Classification: All living things (organisms) are classified by the binomial system of nomenclature, the Linnaean system - Species: is the basic unit of classification Is a group of organisms with structural, functional and developmental similarities A group of organism where all members do or have the potential to breed with one another and produce fertile offspring Each has a unique two part name : italique or underlined - Genus – plural genera (homo, triticum, Acer, Canis, Cannabis, picea) - Species names: include genus and spcies epithet Ex: Homo sapiens Tiricum aestivum (bread wheat) Acer saccharum (sugar maple) - Hierarchical levels of taxonomic (Linnaean) classification are based upon evolutionary relatioships, assuming relationships in genetic (DNA) structure Taxonomic Hierarchy: Class Order Family Genus Species Physiognomic Classification: groups plants simply upon similarities in structure of lifeform - Ex. Branching, leaf shape, height - Two individuals may have similar structure, but be genetically distant - Ex. Terms most regularly used : tree, shrub - Shrub: a woody plant having several stems branching near the ground - Herbs or herbaceous plants: lack wody stems, usually of shorter stature than trees Graminoids: grasses, sedges and rushes (have parallel venation) Forbs: have dendritic of webbed venation Some graminoids can be Arboreal (same height as trees) - Epiphytes: plants that use other plants as supporting structures. They are not rooted in the ground and they do not take nutrients or energy from the plant they grow on. They are not parasitic. - Thallophytes: lichens (on trees, on rocks, on the ground), mosses, liverworts - Leaf-shape and size: broad-leaved, needle-leaved - Deciduous: sheds leaves and becomes dormant in unfavorable seasons - Evergreen: retains green foliage year around - Periodicity: annual (lives a single year), perennial (lives for multiple years) Layers - Moss layer - Herb layer: on the forest floor we find herbs and thallophytes – in a temperate deciduous forest they grow the most in spring and late fall when light is available - Shrub layer: Shorter shrubs and young trees comprise this layer – this is generally not continuous - Tree layer - Crown of trees (head, top part) – together crown of trees compose the canopy Collective terms - Forest: vegetation where trees grow close together - Woodland: vegetation where trees are spaced so that crowns are separated - Mature forest – canopies of trees overlap - Woodlands or savannas the crowns are spaced apart Topic 1, Part 2 – plants and environment - The two most important environmental factors influencing plant growth are water and temperature - Water is lost through transpiration – primarily from the stomata this process cools the plant - Water first enters from soil to the roots, then passes to the stems and finally into the leaves, when it reaches the leaf it passes from the vascular system into a substomatal chamber, then diffuses out as CO2 moves in, some moisture is lost through the epidermis (the skin) of the leaf, Adaptation to dry or droughty conditions – xeric = arid = dry - To be successful in arid environments plants must minimize water loss - They do this through several mechanisms or strategies - Species of plants that are adapted to droughty conditions are called xerophytes Strategies to reduce water loss - minimize loss of water through their epidermis – thick epidermis, special coating - Less surface area maybe no leaves at all - Spines evolved from eaves they slow air flow across the epidermis thus slow evaporation and reduce herbivory - Reduce the number of stomata and sink them to protect them from dry air or reduce the amount of time stomat are open – some strategies do not show up in the outside physiognomy - Deep roots and allow them to tap groundwater - Some desert plants have deep roots that allow them to tap groundwater - Many plants are succulents – they store water in leaves, stems or roots – here you see a stem succulent with no leaves just spines - Seeds of many desert wildflowers germinate in response to rains. They finish their life cycle quickly: flowering and producing seeds that persist through conditionsthat would be too stressful for the living plant They take on a deciduous abit – the plant can become dormant, reducing its water needs Plants in unlimited water areas – rain forest - Evapotranspiration = no problem - Water can be so abundant and so constant that it may sit on leaves for long periods of time - This becomes a problem, fungus can grow on the leaves while nutrients may leach out of the leaf and into the water – to help shed water leaves of many plants have drip tips. - High productivity of plants means they compete with each other for light – the canopy of the rain forest is so dense that light gets through – plants of the rain forest floor need large leaves to capture the shifting flecks of light that pass through as the sun moves overhead - High moisture availability allows plants to have a large leaf surface area as there is no stress in terms of moisture loss through transpiration Carbon crediting and forests - First temporary certified credits for reforestation issued in China - The Kyoto protocol : the ultimate objective of this convention is to achieve stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropoenic interference with the climate system - Net changes in greenhouse gas emissions are determined by considering: Reductions in emissions by sources - Removals by sinks resulting from direct human-induced land-use change Forestry activities, limited to afforestation, reforestation and deforestation since 1990 Afforestation: planting of new forests on lands which historically have not contained forest Reforestation: planting of forests on lands which have historically previously contained forests but have been converted to some other land use Deforestation: not defined but presumably conversion offorests to non-forest Topic 1, Part 3 – Environment radients and biomes Plants and abiotic factors: temperature and moisture - Different species live under a wide varity of conditions - They have different tolerances and different optimum growing conditions Temperature limits - Decreasing temperatures cause a decrease in metabolic rates - Freezing can cause cell damage if ice crystals form in cells – they would cause physical damage physical damage to the cell and tissues - Cold-tolerant species can expel excess water from cells to spaces between cells, where freezing will do no damage - High temperatures can also cause stress – increased respiration and increased water loss higher metabolic rates with physiological, biochemical and molecular changes in plant metabolism Plants and abiotic factors: temperature and moisture - Biomes: A large terrestrial ecosystem classified according to the predominant vegetation type and the adaptations of particular organisms to that environment - Presence of a biome is determined by annual precipitation and average annual temperature Altitude - What happens to temperature, evapotranspiration and moisture availability as we go higher that is increase in elevation? - Temperature decrease, evapotranspiration decreases and moisture availability increases - This further contributes to a sequence of vegetation zones related to altitude The desert biome - Characterized by low precipitation but the degree of aridity is also dependent upon the temperature and the amount of insolation received - The higher the temperature, the drier conditions will be with the same amount of rainfall - Water lost through plants is termed transpiration – that lost directly from the surface of soil and other areas is termed evaporation - Deserts receive precipitation that is less than ½ of the potential evapotranspiration - Displays xerophytic characteristics: succulence leafless – spines – slow growing annuals - Plants are also widely spaces – this helps reduce the competition for moisture - Some plants release toxins from their roots – this prevents other plants from growing too close this practice is called allelopathy. - Low to high in north American south west Increase moisture in moisture allow denser plant cover : from desert cacti to grasses to shrub oak to needleleaved trees in a woodland – there is a transition from a woodland to a needleaf montane forest to alpine tundra Across north America Biome - Midlatitude deciduous/temperate broadleaf forest - The coast rhode island salt marsh on an estuary (where river meets ocean) - Between grassland and forest = oak savanna - Midlatitude grasslands in the prairies with dominant grasses and a number of forbs - Prarie soils: chernozems (mollisols) – mollic epopedon – big litter layer black soil - Become the short grass prairie (grass steppe) - Become desert Equator to the tropic of Cancer in Africa - Rainforest at the equator – soils red clays and not very fertile everything happening above ground - Go up in latitude – tropical scrub/steppe/savanna - Desert in Sudan South from the artic circle in Scandinavia to the coast of Africa - Scandinavia – snow and mountains - The tundra biome: the greatest adaption to low temperatures is shown by plants of the tundra biome – tops of high mountains also have tundra vegetation (alpine tundra) - Artic tundra is characterized by: a short growing season but long days - Summer warmth melts the frozen soil but only the surface. The surface freezes again in winter. The ground below stays permanently frozen and soils are poorly developed – permafrost - Because the lower levels of soil stay frozen, drainage of surface soil is impeded causing marshy wet, conditions - Plants growing here may be adapted to both wet and cold conditions - These wet conditions encourage accumulation of organic matter which in itself helps to hold moisture thus creating a feedback - Growth rates are slow at these cool temperatures and low light intensities, the cycle of freezing and thawing also breaks large roots - Thus tundra plants are small – but also because it is an advantage to be lower that the level of the snow - Snow serves to protect plants by providing insulation and preventing wind damage Mediterranean shrubland - sclerophyll vegetation – scler= hard, phyll=leaf - Many plants that grow in a meditarranean climate for instance have hard, leathery leaves with a thick cuticle - The adaptation is most obvious in the desert biome Plant habitat: - the type of environment where an organism resides or is biologically adapted to live a physical location to which an organism is biologically suited. Most species have specific habitat parameters and limits Subdivision of the plant environment having a certain combination of slope, drainage, soil type, and other controlling physical factors The term habitat is casually used and may have slightly variable meanings, it implies a system on a scale smaller than biome. In some uses it may be the smallest unit Topic 2 – Disturbance and ecological succession Disturbance and succession - In many places, the natural vegetation patterns we observe are a function not of just physical limits, but also of disturbance – natural and human - A disturbance will remove biota from a habitat and possible change the physical nature of the habitat that is cause environmental changes - The vegetation cover that appears immediately after a disturbance is often not the same as that which was lost - Over time the plant species change until the original plant cover returns – or another disturbance occurs - The pattern of change for some biomes is a predictable one - This process is ecological succession Succession � Primary succession is the ecological change that occurs in areas that have been denuded of soil, thus soil organic matter has been lost � The physical conditions in such situations limit the growth of many plants species � The substrate may be bare rock which can be colonized only by lichens and mosses � What types of disturbances might be responsible? Lava flows from volcanic eruptions Landslides Strip mining Glaciers that have scraped the land surface or deposited till upon the land - - Secondary succession is more common in nature – it occurs as a result of less severe disturbances such as fire and windstorms – natural disturbances Land cleared after forestry or agriculture Anthropogenic disturbances Field abandonment : the example most commonly used is the sequence of plant communities that appears after a pasture or crop field has been abandoned Similar to primary succession, there is plenty of light available but there also is soil and some relict vegetation Recovery: stage 1 – annual plants : the first plants to become established are thus that are easily and broadly dispersed – these also grow and mature quickly Those that might be growing on the edge of the cleared area - These are pioneer species – are plants that require full sunlight – include most weeds – their nutrient demands are low they reproduce quickly and seem to get their seeds just about everywhere through wind-dispersal - Stage 2 – perennial herbs and grasses - After the first year or two plants which are not as effectively dispersed and slower growing may become dominant in the plant community - These may be perennial forbs and grasses but still low growing and sun loving - Stage 3: shrub stage : woody plants are slow-growing and become an important part of the landscape over-time first with shrubs then trees eventually replacing shrubs - Through this progression of species replacements the soil continues to change and mature gaining organic matter and nutrient (from plants that die) - Stage 4 – tree stage - Changes in soil conditions make it easier for tree species to survive. Within the forest community we first see trees which are shade intolerant – their seedlings cannot develop in shade - When these trees have grown and developed a canopy other plants including those of their own species will no longer succeed - Stage 5 – final tree stage - The final species replacements are shade tolerant trees – it is not that these trees require or prefer shade- they may take longer to get to a site and/or be slower growing - Climax community Southern US example - Without disturbance, the shade tolerant trees will be the most permanent vegetation cover - If major species replacements no longer occur and it is self- perpetuating it may be termed the climax community - Annual plants - Perennial plants and grasses - Shrubs - Softwood – needleaf) – trees pines - Hardwood trees Paradigm about climax communities - Framework of concepts, results and procedures within which subsequent work is structured - Normal science proceeds within such a framework or paradigm - A paradigm is upset in response to an accumulation of anomalies and stresses that cannot be resolved within this framework Resistance - Some communities have high inertial stability (thus resistance) Redwood forest Pine forest Tropical rain forest - What happens when these systems face large scale disturbances? - There are micro-climate changes – surface temperatures change due to a dramatic change in albedo - Cleared forest tracts are slow to recover - Resilience may be compromised for stability Resilience - Some communities have high resilience – a mid-latitude grassland - It is a matter of onlt a few years for it to recover from a fire or drought Natural disturbances - Always occurring somewhere - Rather than a homogenous climax community (as suggested by our map generalization) landscapes are really a patchwork mosaic of habitats - Each patch is in a different stage of succession - The end product and rate of change can vary depending upon the severity and size of the disturbance, differences in soil condition and history - Now we will begin to evaluate the concept of climax community and the role of disturbance in maintaining broad leaf deciduous forest and boreal forest, rain forest and boreal forest. - Niche: refers to the function or occupation of a life form in a given community – it is the way an organism obtains and sustains the physical, chemical and biological factors it needs to survive Creation of forest gaps - Wind disturbance can blow down a single aging tree, or if severe such as hurricane a large number of trees may fall - This creates gaps in the canopy of the forest, allowing increased light to reach the forest floor - Upturned roots dislodge the soil around them - The organic surface layer will come up with the roots leaving a small patch of mineral soil Gap succession - The size of the gap will affect the composition of the species that begin to fill it - Small patches may be easily filled by species growing adjacent to it - The larger the patch the more difficult it is for any species to reach the middle Birch - Has small light seeds which disperse 100m - Its seeds germinate well on mineral soil - Birch cannot grow in the shade of the other forest trees - It is not shade tolerant - Thus it persists in the deciduous forest only because disturbances provide it with lighted gaps to colonize - As yellow birch grows it produces shade and adds organic matter to the soil changing conditions just enough to make possible the establishment of sugar maple and beech - Both sugar maple and beech demand higher quality soil conditions - The change in habitat brought about by yellow birch that makes it possible for other species to grow is an example of facilitation - The shade prevents new seedlings of birch from surviving in the gap - Instead sugar maple is likely to become established next - because it produces so many seeds and it tolerates shade – seeds are easily dispersed Beech - Will eventually grow in the patch – sprouting from seeds but it can also grow from roots of older beech - Creation of a gap is a small scale disturbance that occurs at a high frequency direst replacement without disturbance – self perpetuating - Through this process all 3 species continue to survive, not in the same location but within the forest as a whole. Each stage of this cycle will be represented simultaneously at some location within the forest Larger scale succession - There is a slightly different response to disturbances at larger scales - Logging or clear cutting - In this situation the first shrub to colonize was pin cherry – it depends not on rapid dispersal but on a seed bank - Pin cherry seeds may survive in the soil for more than 60 years - Seeds are stimulated to germinate by increased levels of nitrogen in the soil when the increased sunlight warms the soil and speeds up microbal activity - The fast growth of pin cherry results in increased productivity of a clear cut - Its leaf litter is high in nitrogen but decomposes slowly due to high concentrations of lignin a carbon compound resistant to decomposition - Thus pin cherry helps to stabilize nitrogen losses and return organic matter to the system - Resilience: pin cherry contributes to the resilience of the deciduous forest - Resilience is the capability of an ecosystem to recover after being perturbed by a disturbance Tropical rain forest - Soils have little organic matter – it is limited to a very thin layer - The organic matter decomposes quickly in the warm, humid climate and nutrient cycling is rapid as compared to the midlatitude deciduous forest - Most of the nutrients are held in the living plants – the nutrient cycling action is there - Vegetation structure: tall, closely set trees, crowns form a dense canopy - The trees crowns may be grouped in layers: the highest is the emergent layer, these trees may have buttressed roots for support - Other layers : lower level canopy, middle level canopy and high one - Trees support growth of numerous other plants – epiphytes and lianas - The complex structure of the rain forest allows not just packing of plants, but packing of varied life strategies or niches. This great variety of plant species in turn supports a high diversity of animal species - Gap succession is a process by which also the tropical rainforest is maintained - Succession in tropical rain forests is not predictable as the pattern of species replacements in the temperate zone - There is such diversity in the mature rain forest that it is difficult to describe a single climax comparable to the beech-maple forests of North America - It is also difficult to identitfy one or a few dominant species - In the rain forest the initial cause of a gap is usually the fall of a senescent tree (aging) - A group of trees will be pulled down with the aging tree because the individual tree crowns are linked together with lianas and are top heavy with epiphytes - A special term has been introduced for the process of gap succession in the rain forest : Chablis - The Chablis is process and product : the fall of the tree, the hole in the canopy, the accumulated debris - The disturbance to the soil - A crown gap with the lower tree and shrub layers intact, but mineral soil spread around - The epicentre in which the crown fell, lots of organic matter is added to the soil surface here - The peripheral zones - The succession will begin with pioneer species, those short-lived and unable to germinate in the shade - Smaller trees in the understory will now grow into the canopy, followed by species capable of germination in the shade - Tropical rain forest vs. ML deciduous forest : the difference between the two is that in the tropical rain forest the final, climax species that dill the gap will not be the same species that were originally in that location – WHY? - There is high seed predation – in the rain forest - Many animal species have co-evolved with plant species and will feed on only one species – they have a very narrow niche - Where should an herbivore look for seeds of its target species? Around the plant - Thus seeds that fall in the vicinity of the producing tree will not be available to sprout when conditions are right - They will be available some distance away and may help to fill a gap there - Charcoal (biochar) enriches the soil as shown in the pit on the left, but there are even more fertile soil patches Harvesting in the tropical rain forest - What happens when the rain forest trees are cut? - The majority of nutrients and organic matter are lost with the vegetation leaving poor soils - In the past, clearance was in small scales by a process called slash and burn – burning of vegetation released some nutrients but fields wew used only for a few years, then abandoned and allowed to go fallow and recover - It is hypothesized that the high diversity of the amazon rainforest is a legacy of such activities by ancient peoples - Settlements of early people and their middens left these patches of dark rich fertile soils called terra preta - The rainforest has been exploited for growth of many economic plants: rubber, cacao, and nuts but at a cost – single crop plantations are attractive to insect pests and soils are depleted of nutrients quickly - This is very different from the slash and burn and regular shifting of sites historically practiced - 50 % of the forest has been lost Part 3 – fire and the boreal forest - Soils have low decomposition rates thus accumulation organic matter - During the last ice age, ice sheets scraped away much of the soil leaving bare rock or just shallow sediments upon which to develop soils - Much of the boreal forest is underlain by permafrost Climax vegetation : - one could say that the climax community and these trees and needle-leaved conifers – most are evergreens (spruce and fir) Larch, a deciduous conifer is common and dominant in Siberia. These trees create a dense canopy which shades the forest flooe year- round - Ground cover is composed of lichens and mosses Disturbance and succession in the boreal forest - 1st effect tree canopy removed with fire – pioneer appear now these are species that are not shade tolerant: aspen and birch - Because these trees are deciduous theu allow greater light penetration in spring thus allow earlier warming of soil and accumulation of litter - Their litter are high in nitrogen and low in lignin ( a carbon compound that resists decomposition – overall this would appear to be a positive feedback loop with conditions improving for production and the new production improving soil conditions - More sunlight reaches forest floor and permafrost melts deeper - Black spruce a fire-climax species – slow growing and shade tolerant – can continue to grow under the canopy of the deciduous trees – black spruce increases in importance developing a higher and broader canopy - New seedlings of black spruce start togrow immediately after the fire - Black spruce has serotinous cones (cones which do not open until exposed by the heat of a fire) - The shade of the spruce canopy begins to decrease soil temperatures - Spruce needles have high lignin content thus are resistant to decomposition. This leads to increased organic matter on the forest floor and decreased nutrient availability - Reverse feedback – soil temperatures decline over the years, depth of the active layer also declines further restricting drainage resulting in increased soil water content - The higher soil water content means that it takes more energy to raise soil temperatures (energy which is not available) so soil temperatures decline - Until there is a fire again – the likelihood of fire continually increases with drought - The moss layer grows in thickness accumulating organic matter – soil water content becomes more favorable to mosses – compete against spruce for soil nutrients and win – release H making soil more acidic - Moss is now physiological dominant as opposed to structural dominant – a fire is necessary for the serotinous cones to release seeds so no new spruce trees will appear until the next fire Concept of climax vegetation - In this definition of biome dominant vegetation – climax vegetation is the vegetation that would be self –perpetuating if left alone Topic 3 – Energy flow Photosynthesis - Carbon + water + solar = glucose +oxygen - Occurs in the cells of the plant, in organelles inside the cell, organelles are called chloroplast - Chloroplasts contain molecules of chlorophyll, the pigment that absorbs the light - It is the process powered by sunlight by which carbon dioxide is unite with hydrogen to produce organic matter - The stoma is the pore in the surface of the leaf - It can open and close thanks to guard cells - When it opens CO2 enters - The process goes into the chloroplast - Surfaces must be moist for CO2 to pass from the stomata to the intercell chamber to the cell that is why water vapor is lost from these chambers through the stomata – problem in arid regions Respiration - As plants are living they are also respiring – they are consuming enegy to maintain their cells and perform metabolic functions – essentially the reverse of photosynthesis - For a plant to survive it must store or fix as much energy as it uses in respiration - This break-even point is called the compensation point - Unless a leaf is functioning on the production side of the compensation point it is not worth it to the plant to keep that leaf - Water enters through the roots and then flows through the xylem within the vascular system to all parts of the vascular system – the nutrient carried in the system are important constituents of the enzymes that facilitate critical reactions in photosynthesis and plant metabolism in general Gross photosynthesis – total amount of carbohydrate produced Netphotosynthesis - amount of carbohydrate remaining after respiration - What can increase photosynthesis : More carbon dioxide More light Less respiration (a plant in stress due to heat or disease will respire more) Primary productivity - Not net photosynthesis but net primary primary productivity – used for a single plant - The amount of stored chemical energy (biomass or organic matter) generated per unit time - Refers to a rate process – the amount of vegetable matter produced per day, week, or year - Fundamental ecological variable – measures the energy input to the biosphere and carbon dioxide assimilation and significance in indicating the condition of the land surface area, wide range of ecological processes and the role of an ecosystem in the global carbon cycle - Carbohydrate is one form of biomass – can be defined mass of organism per unit area expressed in units of energy or mass if dry organic matter - PP of a community amount of biomass produced through photosynthesis per unit area and time by plants - 243 billion metric tons of dry biomass per year Measure PP - Measure the amount of biomass fixed as this represents the store of chemical energy - Harvesting the plant at the end of growing season – drying it and measuring its weight per unit area – end of season standing crop - Relationship between biomass and tree diameter - Height-weight relationships are determind for a few trees by harvesting all tree (cut down and measure) - Do not confuse productivity with standing biomass - Measure carbon dioxide concentrations around a leaf surface or a group of plants – measure the photosynthetic rate and productivityover time – most be scaled for biome Fate of PP - Only about 44% of the shortwave radiation occurs at wavelength useful for photosynthesis – photosynthetically active radiation (PAR) – only incorporate 3 to 10% of PAR Energy flow - through a complex food web – still refer to the sequence of organisms through which energy and nutrients can move in a community as a food chain – each step in the chain of consumption represents another trophic level - Producers – plants - Primary consumers – rabbits, squirrels, mice, vegetariens - Secondary consumers – foxes, hawks, snakes - Energy is lost at each successive trophic level – only a fraction of energy at one trophic level can be passed onto the next level – 10% - As energy is passed from level to level energy is lost in respiration Vegetarianism – biomass energy available - Direct consumption of grain - you get the full energy - Beef eat the wheat and get full energy then eat beef and get only 10% of that energy Biological Magnification - Persistant compounds at each trophic level – pesticides DDT just becomes more concentrated- PCB, mercury, other toxins - Biomagnification - Toxins are retained opposed to energy wich is respired Bioaccumulation - The longer an animal lives the more it consumes in energy but also toxins - Energy is lost but most DDT are not – accumulation of such toxins The carbon cycle - Energy is left is dead biomass called detritus - Detritus are consumed by decomposers (detritivores) who gain their energy that way - Live in environment rich in scaterred food particles – less mobile - Consume organic wastes and shed tissues and dead bodies of plants and animals - Ex. Earthworms - Rate of decomposition: temperature, soil oxygen and soil moisture content tend to be the primary factors - Oxygen may not be readily available – in these systems aerobic respiration cannot take place and the breakdown of organic compounds and energy extraction must proceed by anaerobic pathways such as fermentation – much slower in anaerobic enviornments partly because they are not conducive to fungal growth - Release heat from metabolic activities - End result of decomposition is the conversion of oranic matter back into its original inorganic nutrient form - Mature forest and grass soils the decomposition process establishes and equilibrium over time where litterfall additions equal the amount of organic matter decomposed Biogeochemical cycle - Circuits of flowing elements and materials that combine earth biotic and abiotic systems – the cycling of materials is continuous and renewed through the earth ecosystem - Some pathways may occur over geologic time to sedimentary cycles – these longer cycles would trace the movement of an element or compound from weathering rock through sedimentation and back into rock Controls the Co2 cycle - Most abundant and important greenhouse gas - Methane and nitrous oxide are more powerful greenhouse gases - Reservoirs – a large portion of carbon is stored – oil (formed from ancient deposits of algae production) - Carbonate rock – coal formed from ancient swamp deposits – plants, also primary production - Sinking carbon – temporary storage in vegetation and soil/ longterm storage in peat that accumulate in swamps and marshes – small part to the bottom of lakes and oceans Mauna Loa Hawaii – wave variation in summer and winter – no photosynthesis in winter (less) – respiration instead so more co2 - Increased uptake of coa by the ocean is causing acidification which affects the ability of marine organisms to form shells What we should do – reduce fossil fuel emissions – use less energy Enhance sinks? – rain forest? Extensive losses are occurring storage is fairly temporary Boreal soils – these repeat a cycle carbon is turned over in a period of 1000 years Deciduous forests – regular disturbances means this carbon is recycled Impacts of Global and climate change on natural carbon sinks and penguins Lianas - Decline in carbon sink because increase in liana in the tropical rain forest – not monitored or surveyed - Increased fragmentation of the tropical forest – more light - Increased concentration of co2 – more liana and less trees and the forest edges - Reduce carbon fixed in the forest – more rapid release back the atmosphere – rely on structure of trees – more energy into production of foliage than carbon dense stems Boreal forest - Increase forest fires – successional deciduous forest will burn before spruce can mature - Birch trees have shorter lives so cycling carbon should be more rapid - The lower mineral layer in the spruce forest held more carbon than the birch – surface organic soil layer in birch and spruce forest soil has a higher carbon nitrogen ratio – decompositions is thus faster in these soils retaining less carbon - Shallow permafrost so less soil burned with fire when spruce - Absence of moss cover un the early successional birch forest means conituned soil warming and drying contributing to permafrost loss – deciduous landscape has a higher albedo and there could be a feedback of a longer fire return interval Artic Tundra global warming impacts - Increased respiration by drying, warming by 20% - Decrease of 30% in pond area - longer warmer summers, encouraged greater growth of aquatic plants around the pond margins – increased transpiration from those plants - Increase in the active layer depth below the ponds – could be due to drainage Penguins - Loss of ponds – loss of habitat for organisms that depend upon this habitat - Warming in antartica means less ice and more Adélie penguins – because use rocks for nest so more rocks - Emperor decrease the population because ice melt and food becomes far away Coastal and cultural eutrophication and case studies - In estuaries and lakes primary producers may be submerged vascular plants (flowering plants that grow under water) eelgrass - Macroalgae – non flowering vegetation such as sea lettuce that grow in large sheets Diatoms – smaller than 1 mm - A major component of the phytoplankton in seas and lakes - Microscopic single-celled organisms - Float in the upper water layers – get nutrient from the water - Clear waters some live at the bottom on the mud surface – nutrients from the mud Dinoflagellates - Dinoflagellates are also part of the plankton – these microscopic single celled organisms can be producers or consumers Succession in marine water - At temperate latitude – yearly seasonal succession in phytoplankton - Diatom bloom in the spring nutrient abundant - Diatoms remove nutrient N becomes limiting - Dino more mobile and better at getting scarce nutrient replace diatoms as phytoplankton later in the season Eutrophication - When limiting nutrient are supplied to an aquatic system - Development of lake ecosystems when retreat of glaciers – nutrient become available as terrestrial succession proceeds – very slow process - Limiting nutrient is essential plant nutrient in shortest supply relative to the needs of algae and plants Cultural eutrophication - Often produces an excessive nutrient induced increase in the production of organic matter - Fertilization of lakes, rivers or coastal waters with previously scarce nutrient such as nitrogen or phosphorous boosts primary productivity of algae base of aquatic food chain - Another nutrient will become limiting - Mass of algae grows – murkier water – block light penetration in the water - Algae dies and decomposes periods of oxygen depletion occur – in the sediments and bottom waters - Favor species over others – red tides – decrease in diversity Nutrient pollution - Called nutrient over-enrichment are vital to plant growth - Limiting in freshwater - Estuary – where the river meets the sea – where fresh and salt water mix - Sources: soils after clear cutting, agriculture fields, fertilizer, manure ( non-point sources) both run into surface waters streams and lakes overland or through the soil - Discharge from sewage treatment plants (point souce) - Deposition of N from the air – industrially produced fertilizer and overuse of fertilizers 4 case studies New Bedford – Massachusetts - Land clearance - Wetland loss - Infrastructure development - Indicators of productivity in sequential layers of sediment – fossils of dinoflagellates and diatoms as well as the chemical record of diatoms - Biogenic silica from the frustules outer shell of diatoms – higher concentration of biogenic silica mean karger diatom populations - Forest clearance causes release of 10 times the nitrogen per unit area – is limiting in marine waters - phosphorous in freshwaters limiting - Increase tubidity of waters blocking light and inhibiting photosynthesis – nitrogen imputs ceased because no more clearing and not increasing pop. - Pop then increase lived close to the harbour and sewage in there – became health problem – contains large amount of nitrogen – diverting the waste stream to the waters beyond the harbour – practice common in many places – nutrient levels began to decrease Case study 2 : Chesapeake bay Nonpoint sources – run-off from farmland – and paved areas and lawns Point sources : industry and wastewater treatment plants - Sea grasses provide essential habitat for fisheries – microflora (diatoms) grow as epiphytes on the sea graa - Nutrients enrichment caused excessive growth of this microflora, shading the grass killing it eventually Case study 3 : gulf of mexico Case study 4: north carolian, Maryland – killer algae - Pfiesteria piscicida - crazy life cycle - Cyst satge in water but primarily in mud – waits for the right conditions- feed on bacteria, algae, small animals or on bits of fish flesh - Feed by attaching to prey cells using peduncle - Triggered by pork feces - Highest concentrations of pigs – highest concentration of pig waste in estuaries - Cause lack of dissolved oxygen in the water and other environmental changes Canada - pulp mills, sewage plants, fish plants, septic systems - some waters are still clean like – nutrient pollution is a problem degrading eelgrass habitat such as in bouctouche bay on the gulf of the st. Lawrence and estuaries of Prince Edward island