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by: Alexandrine Dietrich
Alexandrine Dietrich
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Rachel Schroeder

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Rachel Schroeder
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This 221 page Class Notes was uploaded by Alexandrine Dietrich on Monday September 28, 2015. The Class Notes belongs to BIOL 291 at Old Dominion University taught by Rachel Schroeder in Fall. Since its upload, it has received 5 views. For similar materials see /class/215301/biol-291-old-dominion-university in Biological Sciences at Old Dominion University.

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Date Created: 09/28/15
Ch 22 Decomposition amp Nutrient Cycling 0 a id 333 M EEK M 0 Energy flow through an ecosystem is based on the movement of carbon into and out of organisms 0 Primary productivitydepends on the movement of carbon through the food chain the uptake of essential nutrients from the atmosphere and rocks and minerals Internal cycling nutrient cycling is the transformation of organic nutrients into mineral form and back into organisms Decomposition and nutrient mineralization Most Essential Nutrients Are Recycled within the Ecosystem Plants require all essential nutrients in inorganic or mineral form Nutrients are taken up in the soil solution through the roots and the mineral is transformed from an inorganic to organic form As plant tissues age and die senesce nutrients are returned to the soil surface in the form of dead organic matter Retranslocation or reabsorption of some nutrients occurs Retranslocation Net primary productivity Litterfall Incorporation into plant tissues Dead 1 11 organic matter Decompositionmineralizationj Plant uptake Soil nutrients 2012 Pearson Education Inc Retranslocation or reabsorption of some nutrients occurs In temperate regions as days become shorter in the autumn chlorophyll production responsible for green leaf color begins to decline Plant roots can reabsorb minerals especially nitrogen from the leaves that will be lost from the plant Yellow and organic pigments begin to show and anthocyanins are produced Decomposition Is a Complex Process Involving a Variety of Organisms Decomposition the breakdown of chemical bonds of organic molecules is the key process in the recycling of nutrients within the ecosystem Release of energy carbon dioxide and water Decomposition includes many processes Leaching Fragmentation Changes in physical and chemical structure Ingestion Excretion of waste products Decomposers are organisms that feed on dead organic matter or detritus bacteria fungi and detritivores All heterotrophs function to some degree as decomposers Bacteria are the dominant decomposers of dead animal matter Aerobic Anaerobic fermentation of organic matter in mudsediments of aquatic habitats and in the ungulate rumen Fungi are the major decomposers of plant matter Extend hyphae into organic material to withdraw nutrients Bacteria and fungi secrete enzymes into plant and animal tissue to break down organic molecules 2012 Pearson Education Inc Invertebrate detritivores decompose leaves twigs and other detritus and are classified by body width Microfauna and microflora lt1OO um include protozoans and nematodes inhabiting the water in soil pores Mesofauna 100 pm to 2 mm include mites potworms and springtails that live in soil air spaces Macrofauna 2 20 mm Megafauna gt20 mm Macro and megafauna are represented by Terrestrial snails millipedes and earthworms Aquatic annelid worms crustaceans eg amphipods and isopods mollusks and crabs Earthworms and snails dominate the megafauna 2012 Pearson Education Inc 2012 Pearson Education Inc Studying Decomposition Involves Following the Fate of Dead Organic Matter Ecologists study the process of decomposition by designing experiments that follow the decay of dead plant and animal tissues through time Litter bags are used to examine the decomposition of plant litter A similar approach to litterbag experiments is used in stream ecosystems To quantify the process of decomposition plant litter that accumulates in areas of active deposition is placed in mesh bags leaf packs that are anchored in place 202 PDarson Education Inc Estimating the Rate of Decomposition Litterbag experiments are the primary means by which ecologists study decomposition Replicate litterbags are collected at regular intervals during the process of decay Researchers plot the proportion of mass loss through time Several Factors Influence the Rate of Decomposition Plant litter quality Carbon form available affects the consumption or decomposition rates Glucose and other simple sugars highquality sources of carbon small molecules high energy bonds Cellulose and hemicellulose structurally complex more energy required to break bonds moderate quality Lignin and others very large and complex molecules slow to decompose low quality Basidiomycetes are the only group of decomposers to decompose these molecules The rate of organic matter decomposition is directly affected by temperature and moisture Low temperatures and dry conditions reduce or inhibit microbial activity Warm and moist conditions are the optimum environment for microbial action Nutrients in Organic Matter Are Mineralized During Decomposition The nutrient quality of dead organic material varies greatly the higher the nutrient content the higher the nutrient value for the decomposer The net mineralization rate is the difference between the rates of mineralization and immobilization Mineralization is the transformation of nutrients contained in organic compounds into inorganic forms Immobilization is the uptake and assimilation of minerals by microbial decomposers Decomposition Proceeds as Plant Litter s Converted into Soil Organic Matter As the decomposition process continues the litter degrades into a dark brownblack homogeneous organic matter called humus As humus becomes embedded in the soil matrix it is referred to as soil organic matter Soil organic matter typically has a residence time of 20 to 50 years It can range from one to two years in a cultivated field to thousands of years in environments with slow rates of decomposition cold or dry Plant Processes Enhance the Decomposition of Soil Organic Matter in the Rhizosphere The rhizosphere is the region of the soil where plant roots function an active zone of root growth and death with intense microbial and fungal activity Decomposition in the rhizosphere is more rapid than in the bulk soil Roots alter the chemistry of the rhizosphere by secreting carbohydrates into the soil The interplay between microbial decomposers and microbivores determines the rate of nutrient cycling in the rhizosphere and strongly enhances the availability of mineral nutrients to plants The soil microbial loop Plants supplement carbon to microbial decomposers in the rhizosphere Microbes are preyed on by microbivores that release minerals and nutrients back to the soil Enhancement of mineral cycling and an increase in nutrient availability to plants Energyrrich carbon exudates lmm ne So gar r004 bps uncuon lo suppiemenl me mane ens y new a bat g m 3 l a mum derr a d5 by breaka own me sou Dvgamc matter 80M mat ban Soil cungi Snl bacteria m 2 a E a Nuwenls we sequestered durng microbial gmwm remamed asked up m Iunga an 55 n consumpho Nematodes Ieeding on bacteria hence readHy avauame or uptake by plaan 2012 Pearson Education Inc Decomposition Occurs in Aquatic Environments Flowing water ecosystems Aquatic invertebrates Shredders fragment organic particles in the process of eating bacteria and fungi on the surface of the litter Filtering and gathering collectors filter fine particles and fecal material of the shredders Grazers and scrapers feed on material growing or collecting on rocks Algae take up nutrients and dissolved organic matter from the water Open water ponds lakes ocean Particulate organic matter POM is ingested digested and mineralized as it makes its way to the bottom Bottom dwelling detritivores may further decompose the organic matter Benthic Bacteria are the primary decomposers on the bottom organic matter Water Flow Influences Nutrient Cycling in Streams and Rivers Stream inputs of nutrients Dead organic matter from adjacent terrestrial ecosystems Rainwater Subsurface seepage The continuous directional movement of water affects nutrient cycling in streams Nutrient spiraling occurs because nutrients are continuously being transported downstream A time and spatial element to cycling Spiral length is measured as the distance needed to complete one cycle the longer the distance required the more open the spiral Spiraling patterns are different for different areas of a stream eg headwater versus low reach streams Spiral length 1quot o E 39 i oor p39oration of mineral nutrients Turnover into biomass decomposition and mineralization I 39 of nutrients in dead 39 organic matter quot39 1y Water column 2012 Pearson Education Inc Nutrient Cycling Differs between Terrestrial and OpenWater Aquatic Ecosystems In virtually all ecosystems there is a vertical separation between the zones of production photosynthesis and decomposition n terrestrial and shallow water environments plants directly link production in canopy or leaves and decomposition at soil surface As water depths increase primary production is dominated by free floating phytoplankton in the photic zone while decomposition occurs in the benthic zone Zone of Pr maTY primary production DFQdUC IOn canopy photic zone surface waters Zone of Zone of decomposition decomposition benthic zone forest floor bottom sediments 2012 Pearson Education Inc Ecological Issues Nitrogen Fertilizers There is a tight link between net primary productivity NPP and decomposition NPP determines the quantity and quality of organic matter available to decomposers 0 In agriculture this balance is disrupted because plants and the nutrients that they contain are harvested and the organic matter does not return to the soil so nutrient supplements fertilizers are added Historical development of chemical fertilizers Natural fertilizers manures ground animal bones Chemical fertilizers natural and synthetic sources Three elements are necessary in large quantities for plant growth Potassium K Phosphorus P Nitrogen N Originally these came from mineral deposits K potash P phosphate rocks N saltpeter As the demand for food increased with human population there was a growing concern about the depletion of nitrogen for chemical fertilizers In the early 19005 F Haber developed the synthetic ammonia process N2 3 H2 gt 2 NH3 that made ammonia manufacture economically feasible C Bosch translated this to a large scale process using a catalyst and high pressure methods The Haber Bosch process has changed the way nitrogen fertilizers are produced and used The bounty of food produced comes with environmental cost Nitrates pollute drinking water Nitrogen runoff from agricultural fields disrupts the normal constraints on primary productivity 0 Excess nitrogen deposited in aquatic ecosystems leads to eutrophication the explosive growth of algae High inputs of organic matter result in a corresponding increase in decomposition and respiration gt huge reduction in 02 content of water Many native organisms cannot survive these subsequent low oxygen conditions Ch 21 Ecosystem Energetics Part Six Ecosystem Ecology To an ecosystem ecologist an ecosystem is composed of autotrophs heterotrophs and the abiotic environment each component processing and exchanging energy and matter Autotrophs are primary producers Heterotrophs can be decomposers or consumers The abiotic component consists of air water soil and so forth The driving force of the ecosystem is the Sun s energy The Laws of Thermodynamics Govern Energy Flow 0 Two laws of thermodynamics govern the expenditure and storage of energy The first law of thermodynamics The second law of thermodynamics The first law of thermodynamics states that energy is neither created nor destroyed it is merely transferred or transformed The second law of thermodynamics states that when energy is transferred or transformed part of the energy assumes a form that cannot pass on any further Primary Production Primary production is the production of organic compounds from atmospheric or aquatic CO2 mainly through photosynthesis chemosynthesis much less important Almost all life on earth is directly or indirectly reliant on primary production 0 Organisms responsible for primary production are known as primary producers or autotrophs and form the base of the food chain grazing food chain 0 In terrestrial ecoregions these are mainly plants while in aquatic ecoregions phytoplankton amp algae are primarily responsible Primary production is distinguished as either gross or net Energy Fixed in the Process of Photosynthesis s Primary Production Gross primary productivity GPP is the total rate of photosynthesis or the energy assimilated by autotrophs Autotrophs must expend energy in the process of respiration R 0 Net primary productivity NPP is the rate of energy storage as organic matter after respiration NPP GPP R Productivity is the rate at which organic matter is created by photosynthesis Biomass is the amount of organic matter present at any given time Standing crop biomass mass of organic matterarea gm2 0 Units of productivity Energyareatime kcaImZyr Mass of organic matterareatime gmZyr Measurement Both gross and net primary production are in units of mass area time terrestrial ecosystems mass of carbon per unit area per year g CmZyr most often used NPP Often measure change in standing biomass over time Other factors must be considered belowground productivity herbivory decomposition turnover litterfall volatile organic compounds root exudates allocation to symbiotic microorganisms SOOC E 3 2000 0 o E Temperature 1000 o Water and g Nutrients contrOI 0 mice 25 3500 4600 A D v Precipitation mm Primary Production 3000 in Terrestrial Ecosystems 2000 1000 Dry matter productivity gmzyr i 3910 O 10 20 3 Temperature C A U39 V Tropicai forest 325 Hemlock beech forest Beechimaple Pine 300 forest gtforests Chestnut oak heath 0 Pine heath Tallgrass prairie Alpine tundra Arctic O tundra Aboveground productivity Iogm gmz N 07 O CreosotuLbush desert 15 O I I I I 200 225 250 275 300 325 Eslimated actualeva otrans iration 10 mm r 9 2012 Pearson Education Inc p p gm y Global productivity patterns reflect the influence of climate in terrestrial ecosystems and the global patterns of temperature and precipitation I Productivity ranges gmzyr dry matter lt1oo 25071000 150072000 womzso I 100 500 I gt2000 2012 Pearson Education Inc Temperature water and nutrients control primary production in terrestrial ecosystems NPP increases with increasing nutrient availability Temperature light and nutrients control primary production in aquatic ecosystems Light is a primary factor limiting productivity in aquatic ecosystems Nutrients especially nitrogen N phosphorus P and iron Fe are a major limitation on primary productivity in the oceans Standing biomass kgm2 Tropical 50 O Terrestrial ecosystems rain forest 0 Marine ecosystems 40 O O 30 O 20 0 Tropical 1O coral reef O 0 39 I I Q 9 0 500 1000 1500 2000 2500 Net primary productivity gm2yr 2012 Pearson Education Inc Primary Productivity Limits Secondary Production NPP is the energy available to heterotrophs Often the NPP is not all used within the same ecosystem The fate of energy in the form of plant material varies once consumed by a heterotroph Passes from the body as waste products Maintenance Heat loss Secondary production growth and reproduction Consumers Vary in Production Efficiency There is considerable variation among consumer organisms in their efficiency to transfer energy consumed into secondary production growth and reproduction Varies with species taxonomic class and type of consumer Trophic Level 0 Trophic level position in a food web determined by number of energy transfers from primary producers to current level Primary producers occupy first level Primary consumers occupy second level Secondary consumers occupy third level Tertiary consumers occupy fourth level Ecosystems Have Two Major Food Chains There are two major food chains within any ecosystem grazing and detrital The distinction between the two is the source of energy for the first level consumer Grazing gt living plant biomass primary production Detrital gt dead organic matter or detritus The two chains are linked The initial source of energy for the detrital food chain is the input of dead organic matter and waste materials from the grazing food chain Grazing food chain Detrital food chain F H Primary producers Consumption Efficiency Determines the Pathway of Energy Flow through the Ecosystem The relative importance of the grazing and detrital food chains and the rate of energy flow can vary among different types of ecosystems The consumption efficiency defines the amount of available energy produced by any given trophic level which is consumed by the nexthigher level Consumption efficiency at different trophic levels determines the pathway of energy flow Respiration Respiration Grazer Deoomposer system system Net primary Dead organic productrvrty matter a Forest 2012 Pearson Education nL Respiration Respiration Grazer Decomposer system system I 39 Dead organic matter A Net primary productivity From terrestrial catchment d Stream community 3 2012 Pearson Education Inc Energy Decreases in Each Successive Trophic Level The quantity of energy flowing into a trophic level decreases with each successive trophic level because not all energy is used for production Only 10 percent of the biomass in a given trophic level is converted to biomass at the next higher trophic level Herbivores eat 1000 kcal of plant gt 100 kcal converted to herbivore tissue gt 10 kcal into firstlevel carnivore production gt 1 kcal into secondlevel carnivore production Trophic Dynamics A trophic view of ecosystems Trophic dynamics transfer of energy from one part of an ecosystem to another Trophic pyramid loss of energy in each successive trophic level due to respiration and heatloss Ecosystem pyramids can be constructed by summing the biomass in each trophic level Decreasing energy transfers with increase in trophic level gt decreasing standing biomass of organisms The total mass supported at each level is limited by the rate at which energy is being stored at the next lower level A general narrowing of the pyramid Dry weight gmg Tertiary consumers 15 Secondary consumers it 37 Primary consumers 809 Producers a Florida bog Dry weight 2 gm Consumers zooplankton 21 4 Producers phytoplankton b English Channel As energy losses between trophic levels accumulate eventually there is insufficient energy left to support a viable population at a higher trophic level ENERGY LOSSES LIMIT THE NUMBER OF TROPHIC LEVELS IN AN ECOSYSTEM will be on exam Biotic Controls Bottom up controls Influence of physical amp chemical factors on ecosystems Top down controls Influence of consumers on ecosystems Trophic cascades May involve indirect interactions linked through intermediary species Effects of predators on prey alterations in abundance biomass or productivity By reducing planklivomu 5 sh Trophic cascades in a lake ecosystem Planklivomus E inverlehrulcx a 39 u w i Smallhcrbivurnm 39 Lures herbivorous gr 7 V I r w moplunhnn wuplullklun E Large phymplzmkmn Nulriems 00 1 Small phymplunkmn 1 9 Ch 23 Biogeochemical Cycles N P S Biogeochemical Cycles Many chemical reactions take place in abiotic components of the ecosystem Atmosphere Water Soil Parent material The biogeochemical cycle is the cyclic flow of nutrients from the nonliving to the living and back to the nonliving components of the ecosystem There Are Two Major Types of Biogeochemical Cycles In gaseous biogeochemical cycles the main pools of nutrients are the atmosphere and the oceans Global Nitrogen carbon dioxide oxygen n sedimentary biogeochemical cycles the main pool of nutrients is the soil rocks and minerals Inorganic sources of minerals are released to living animals through weathering and erosion Phosphorus Hybrid of gaseous and sedimentary cycles occur Sulfur Both gaseous and sedimentary cycles Involve biological and nonbiological processes Are driven by the flow of energy through the ecosystem Are tied to the water cycle Biogeochemical cycles could not exist without the water cycle 0 All biogeochemical cycles have a common structure Inputs Internal cycling Outputs Atmospheric input Ecosystem Net primary Internal productivity cycling Incorporation into plant tissues Litterfall 4 t 7 Dead I 74 organic i i K 1 Out ut Plant uptake 1 it 1 matter p DecompositionMineralizationJ Soil nutrients Output Input from the weathering of rocks and minerals Nutrients Enter the Ecosystem via Inputs 0 The input of nutrients depends on the cycle Nutrients with a gaseous cycle enter the ecosystem via the atmosphere Nutrients with a sedimentary cycle enter the ecosystem via weathering of rocks and minerals Outputs Represent a Loss of Nutrients from the Ecosystem The output of nutrients depends on the cycle Release of CO2 from expiration of heterotrophic organisms Organic matter can be carried out of an ecosystem Through surface flow of water or underground flow of water By herbivores Nutrients are released slowly from organic matter as it is decomposed The Nitrogen Cycle Begins with Fixing Atmospheric Nitrogen Nitrogen is an essential constituent of proteins a building block of all living tissue 0 Nitrogen is available to plants in two forms Ammonium NH4 Nitrate NO3 The Earth39s atmosphere is 80 percent nitrogen in the form of N2 This form is unavailable to plants for assimilation 39 Inorganic j nitrogen NH4quot NOE H4 7 Inorganic nitrogen Ni 14 VNOs v 2012 Pearson k Nitrogen Fixation Atmospheric nitrogen can be converted into a usable form biologically This fixation is carried out by Symbiotic bacteria living in mutualistic associations with plants Freeliving aerobic bacteria Cyanobacteria bluegreen algae Am monification Ammonification occurs when ammonium NH4 is converted to NH3 as a waste product of microbial activity Loss of gaseous NH3 from the soil to the atmosphere is influenced by soil pH Nitrification Nitrification is the stepwise conversion of NH4 to NOZ by Nitrosomonas and then conversion of N02 to NC by Nitrobacter The nitrate may be taken up by plant roots or returned to the atmosphere Denitrification Denitrification is the chemical reduction of NO to N20 and N2 by Pseudomonas which are then returned to the atmosphere This reduction requires anaerobic conditions This process is common in wetland ecosystems and bottom sediments of aquatic ecosystems N2 Fixation Ammonification Denitrifioation Assimilation Nitrification 2012 Pearson Education Inc Fixation in 2012 Pearson Education Inc Humans amp Nitrogen 0 Human activity has significantly influenced the global nitrogen cycle Conversion of native forests and grasslands to agricultural fields Application of chemical fertilizers to agricultural fields Auto exhaust and combustion add N20 NO and N02 to the atmosphere which leads to an increase in ozone concentration of the stratosphere The Phosphorus Cycle Has No Atmospheric Pool 0 Phosphorus P can only be cycled from land to sea and is not returned via the biogeochemical cycle 0 The main reservoirs of P are rock and natural phosphate deposits Phosphorus is released by weathering leaching erosion and mining In most soils only a small fraction of total phosphorus is available to plants F p particulate phosphorus P0 organic phosphates inorganic phosphates 2012 Pearson Education Inc The phosphorus cycle Little atmospheric component although airborne transport River transport Ocean waters are a significant global pool of P simply due to large volume Organic phosphorus in the surface waters is recycled very rapidly The phosphorous deposited in sediments or deep waters is unavailable to phytoplankton until upwelling Sediments 9 2012 Pearson Education Inc x The Sulfur Cycle s Both Sedimentary and Gaseous The sulfur cycle has both sedimentary and gaseous phases In the longterm sedimentary phase sulfur is tied up in organic and inorganic deposits and is released by weathering and decomposition The gaseous phase permits sulfur to circulate on a global scale o oxidation r reduction m mobilization im immobilization 2012 Pearson Education Inc Atmospheric sulfur sources as HZS Combustion of fossil fuels Volcanic eruptions Ocean surface exchange Decomposition Atmospheric sulfur dioxide 02 is carried back to the surface in rainwater as weak sulfuric acid H2504 Transport to sea VOICan39C 4 5 activity 20 Trans on to land D d wetangj a Bio enic ry deposmon r 1 i V g 90 gases 4 l Biog39enie I gases 1 44 1 16 5 2012 Pearson Education Inc The Various Biogeochemical Cycles Are Linked The biogeochemical cycles are linked through their common membership in compounds that form an important component of their cycles Nitrate and oxygen in nitrate Autotrophs and heterotrophs require nutrients in different proportions for different processes Stoichiometry is the branch of chemistry that deals with the quantitative relationships of elements in combination Ch 17 Community Structure amp Ch 18 Factors Influencing Community Structure Part Five Community Ecology The ecological community is the set of plant and animal species that occupy an area Attempts at reconstructing communities raise countless questions questions central to the study of ecological studies What controls the relative abundance of species within the community How do the component species interact with each other How do communities change through time How do different communities on the larger landscape interact Chapter 17 Community Structure 0 A broad definition of community is a group of species that occupy a given area interacting either directly or indirectly A spatial concept A more restrictive definition of community is a subset of species such as a plant bird small mammal or fish community A relatedness or similarity among members of the community 2012 Pearson Education In Community Structure A community has attributes that differ from those of its components Physical structure Number of species species richness Relative abundance of species Nature of species interactions Communities Have a Characteristic Physical Structure The form and structure of terrestrial communities are defined primarily by their vegetation Ecologists often classify and name terrestrial communities based on the dominant growth forms eg herbaceous woody and their physical structure The physical structure of aquatic communities is defined by features of the abiotic environment eg salinity water depth Dominant organisms are also used to classify and name aquatic communities T r H r Floating pl nts Submerged Openwater 39 plants Forest strata Canopy Lower canopy Understory trees Shrub Deep ShaHow Grass Shrub Young Mature water waier 39 forest foresi Emergents Herbaceous Orga layer 2012 Pearson Education Inc Terrestrial Vertical Structure Terrestrial vertical structure is determined by the growth form of plants which controls the vertical gradient of light 0 A welldeveloped forest has multiple layers of vegetation The upper layer canopy is the primary site of energy fixation through photosynthesis get most sunlight The understory is situated under the canopy and will only form if enough sunlight can reach these lower layers The nature of the herb layer depends on various abiotic conditions eg soil moisture and density of the canopy and understory The forest floor is where decomposition takes place and nutrients and minerals are recycled Aquatic Vertical Structure Aquatic vertical structure is determined largely by light penetration through the water cdumn The photic zone is where the availability of light supports photosynthesis The aphotic zone is an area without light The benthic zone is where decomposition is most active along the floor of ocean forest etc Organisms amp Structure Various types of consumers and decomposers occupy all levels of the community Interchange takes place among the vertical strata though many highly mobile animals restrict themselves to only a few layers The composition of species in each layer shifts during the day with season in response to weather or climate in response to abiotic conditions oxygen light etc Zonation Is Spatial Change in Community Structure As one moves across the landscape the physical and biological structure of the community changes For example the changes in biological structure that occur in a hilly forest from hilltop to bottomland These changes are referred to as zonation Patterns of spatial variation in community structure or zonation are common to all environments aquatic and terrestrial Helaiiva abundance Species Hilltop Eonomland While oak 5512 7 Scarlet oak 9V Yellow poplar 1114 967 Fled maple 1508 1408 Virginia pine 2 51 Mockemul hickory 259 Dog ood 159 071 Ironwood 29 29 Sweet gum 36 27 Sycamore 8 35 Black gu 452 075 Eastern red cedar 0 68 Shannon index 169 172 species diversity I Boltomland Stream 2012 Pearson Education Inc Intertidal zonation is determined by tidal action Sandy beaches are supratidal and are situated above the hightide line Intertidal areas lie in between the high and low tide line The subtidal zones are below the low tide line and are continuously inundated Ghost Beach 7 amphipods Mole crab Ghost shrimp 1 6mm 17 39 mg Coquina clam Hugh has cucumber KI Iflsh Tvger beetle Olive Flounder 1140 unw 2012 Pearson Education Inc Ch 18 Environmental Heterogeneity Influences Community Diversity 0 Environmental conditions are typically not homogenous within a given community How does environmental heterogeneity within a community influence patterns of diversity Increased vertical structure means more resources and living space and a greater diversity of potential habitats Moisture Wettest I gt 106 MgcmZ I 076 105 lugch l 046 075 Mgcm2 Driest I 010 045 lugsz Distance m a Distance m 2012 Pearson Education Inc NO3 concentration Highest I gt 58 MgcmZd l 40 57 lugcmZd l 22 39 MgCmZd Lowest 03 21 ugcmZd Distance m O 23 46 69 b Distance m 2012 Pearson Education Inc Robert MacArthur first quantified the relationship between structural heterogeneity of vegetation and diversity of animals that depend on the vegetation as habitat MacArthur measured structural heterogeneity of vegetation and bird species diversity in 13 communities in the northeastern United States Index of species diversity Index of foliage height diversity He found a strong relationship between species diversity and foliage height diversity Environmental Complexity In many communities Forests with greater bird species diversity foliage height diversity increases with greater support high bird foliage height diversity LS diversity H39 J Bird 5p Plum communilies with low foliage height diversin support low bird species diversity Foliage height diver in H39 The Number of Species and Their Relative Abundance Define Diversity Species richness 5 is the count of the number of species occurring within the community Relative abundance represents the percentage each species contributes to the total number of individuals of all species The patterns of species richness and relative abundance can be compared between communities Species Abundance relative representation of a species in a particular ecosystem It is usually measured as the number of individuals found per sample Species Diversity A combination ofthe number of species and their relative abundance Species richness of species in a community Species evenness how close in numbers the different species in an environment are Species evenness Species evenness indicates the distribution of species richness i u uh min ch iquotmommaIwhichimi uL i nquai pmwniom i i i i Wi g a g u a f t Diversity Indices Diversity indices provide a way to quantify the relationship between species number and relative abundance Simpson39s index D ZnN2 Z summation for all species n number of individuals of species i N total number of individuals of all species D ranges between 0 and 1 and as both species39 richness and evenness increase the value approaches 0 ShannonWeiner Index 0 Shannon or ShannonWeiner index H 39leilllogz pi Relative abundance of each species pi n N p proportion of species i In the absence of diversity where only one species is present H 0 H occurs when all species are present in max equal numbers Numerical Supremacy Defines Dominance When a single or few species predominate within a community these species are referred to as dominants Dominance is the converse of diversity When the basic Simpson index D is 1 the 1 represents total dominance only one species present in the community Dominant species are usually defined separately for different taxonomic or functional groups of organisms within the community eg tree versus herbaceous plant species Dominance can reflect the number of individuals size of individuals or some combination of characteristics that include both the number and size of individuals 0 Dominant species are typically the dominant competitors under the prevailing environmental conditions Other factors may determine dominance within communities Keystone Species A keystone species has a disproportionate impact on the community relative to its abundance The removal of a keystone species initiates changes in the community structure and often results in significant loss of diversity What is a keystone species Keystone species are those whose in uence quot is Dominant species are ones that have structures by virrure of high biomass Dominau species their biomass Keyslune Species Tomi impaei of 5chicgt Lew Luw Relzuive biomass of species High Keystone Species Examples Otters man hunting caused collapse of algae ecosystem Pisaster starfish diversity of the prey went down from 56 species to 2 species once starfish removed Nile perch exotic predator introduced invasive species brought fish species from 400 to 40 in a few years Most of the time they are the top predators Top down affected by the top predator Ch 18 The Fundamental Niche Constrains Community Structure 0 All living organisms have a range of environmental conditions under which they can successfully survive grow and reproduce 0 This range of environmental conditions is not the same for all organisms A wide variety of adaptations allow an organism to function successfully under a given set of environmental conditions These same adaptations also limit its ability to do equally well under different conditions there are trade offs High versus lowlight conditions for plants Effect of ectothermy on species activity and distribution Number of offspring and the level of parental care Niches quothow an organism makes a living 0 The Eltonian niche encompasses the idea that the niche is the role a species plays in a community The ecological niche describes how an organism or population responds to the distribution of resources and competitors eg by growing when resources are abundant and when predators parasites and pathogens are scarce in turn alters those same factors eg limiting access to resources by other organisms acting as a food source for predators and a consumer of prey Definitions Guild Group of organisms usually animals that all quotmake their living in the same fashion occupy similar niche Examples Seed eating animals in the desert Fruiteating birds in a tropical rainforest Filterfeeding invertebrates in a stream 0 Life form term used for plants combination of structure and growth dynamics Trees vines annual plants sclerophylous vegetation hot dry climates grasses forbs broad leaf herbaceous Food Chains Community ecologists focus on the feeding relationships among the component species 0 A food chain is a descriptive diagram that represents the flow of energy from prey the consumed to predator the consumer Grass gt grasshopper gt sparrow gt hawk Food Webs Feeding relationships in nature are more complex than food chains and include an array of linkages among primary producers and consumers Food webs are highly interwoven with linkages representing a wide variety of species interactions K Marsh hawk Upand DIOVGr CIay co ored sparrow Ground squirrel 473 7 2012 Pearson Education Inc n l m Antarctic pelagic food web The Soil Food Web imam 5 Wmquot 39 d quot quotm quot S x mmva Birds Human15 mam mm Ma ak mm amwe Hvsnvophit Snow mm mm Founhunpm m um um wphlzlnvel luvz Imx myme thmynmesvms mommy smmum mmwm 39Ievels mm mums mm mm My my mums mm 9mm Food Webs Describe Species Interactions 0 Basic terminology is associated with food web structure Links are the arrows from one species to another and indicate the consumed and the consumer Basal species feed on no other species but are fed upon by others Intermediate species feed on other species and they themselves are prey of other species Top predators prey on intermediate and basal species Top predator Intermediate species Intermediate species Basal species 2012 Pearson Education In Ecologists often simplify the representation of food webs by grouping species into broader categories that represent general feeding groups trophic levels based on the source from which they derive energy Autotrophs primary producers Heterotrophs Herbivore primary consumer Carnivore secondary or higher consumer Omnivore Trophic Levels 0 Trophic Level position in a food web determined by number of energy transfers from primary producers to current level lst level primary producers autotrophs 2nd level primary consumers herbivores and detritivores 3rd level secondary consumers carnivores on primary consumers 4th level tertiary consumers predators of carnivores Species Interactions Are Diffuse Diffuse competition Diffuse predator prey interactions The lynx coyote and horned owl are responsible for the periodic cycles in the snowshoe hare population Diffuse mutualism A single plant species may depend on a variety of animal species for successful reproduction Diffuse feeding relationships Food Webs Illustrate Indirect Interactions Indirect effects occur when one species does not interact with a second species directly but instead influences a third species that does directly interact with the second Indirect interactions can potentially arise throughout the entire community because of a single direct interaction between only two component species Lynx predation on the snowshoe hare that feed on white spruce can positively affect the white spruce population Gooseneck bernades 3 specnes mepets Acorn 2 spec eS bamacles 3 spaces b 1 species 9 2012 Pearson Education Inc Ex removal of Pisaster starfish top predators from some areas experimental but not from others control After the starfish were removed the number of prey species dropped from 15 to 8 In the absence of predation several ofthe mussel and barnacle species superior competitors excluded the other species and reduced overall diversity Keystone predation is the indirect interaction where the predator enhances one or more inferior competitors by reducing the abundance of the superior competitors Removing a species from the community can have many unforeseen consequences Ex local extinctions of wolves and grizzly bears have affected the larger ecological community in the Greater Yellowstone ecosystem The loss of large predators has resulted in an increase in the moose population Moose selectively feed on willow and other woody species Decline in bird populations due to the loss of this habitat along river shorelines Food Webs Suggest Controls of Community Structure Species can be aggregated into trophic levels Primary producers Herbivores Carnivores 2012 Pearson Education Inc I I Primary producers b Ch 19 Community Dynamics Succession Community Dynamics 0 The changing nature of community structure across the landscape reflects the shifting distribution of populations in response to Changing environmental conditions Interactions among species Community structure is dynamic Shifting pattern of species39 dominance and diversity through time Community Structure Changes through Time Community structure varies in time and space Across the landscape zonation In one position as time passes Succession is the gradual and seemingly directional change in community structure through time from field to forest The sequence of communities from grass to shrub to forest has been called a sere and each ofthe changes is a seral stage Each sera stage has its characteristic structure and species composition It may last only one to two years or for several decades 39 Patterns Of succession are not random Early successional species or pioneer species are usually characterized by high growth rates smaller size high degree of dispersal and high rates of per capita population growth Late successional species have lower rates of dispersal and colonization slower per capita growth rate and they are larger and longer lived Disturbance and Diversity Disturbance difficult to define as it involves departure from quotaverage conditions Average conditions may involve substantial variation White and Pickett defined disturbance Any relatively discrete event in time that disrupts ecosystem community or population structure and changes resources substrate availability or the physical environment Two major characteristics Frequency Intensity Intermediate Disturbance Hypothesis 0 M Huston and J Connell proposed disturbance is a prevalent feature that significantly influences community diversity Proposed both high and low levels of disturbance would reduce diversity Intermediate levels promote higher diversity Sufficient time between disturbances allows wide variety of species to colonize but not long enough to allow competitive exclusion The Intermediate Disturbance Hypothesis IDH states that local species diversity is maximized when ecological disturbance is neither too rare nor too frequent at low levels of disturbance more competitive organisms will push subordinate species to extinction and dominate the ecosystem at high levels of disturbance due to frequent forest fires or human impacts like deforestation all species are at risk of going extinct Disturbance acts to quotreset the clockquot in succession Patterns of diversity depend on the frequency of disturbance High gt diversity will remain low because later successional species never have a chance to colonize Low gt diversity will decline as later successional species displace earlier species Intermediate gt colonization can occur but competitive displacement is held to a minimum Species diversity a o b c High Frequency of disturbance r 3 ML A D v 9 2012 Pearson Education Inc Community and Ecosystem Stability Stability Absence of change Resistance Ability to maintain structure and function in face of potential disturbance Resilience Ability to recover from disturbance Primary vs Secondary 0 Primary succession occurs on a site previously unoccupied by a community like after an extreme disturbance where all individuals were removed Secondary succession occurs on previously occupied vegetated sites after disturbance the disturbance does not always result in the removal of all individuals Primary Succession Occurs on Newly Exposed Substrates 0 Primary succession begins on sites that have never supported a community Rock outcrops and cliffs Lava flows Glacial till when glaciers retreat Sand dunes Sand dunes The establishment and growth of plant cover acts to stabilize the dunes Grasses are the most successful pioneering plants Once the dunes are stabilized mat forming shrubs invade the area The vegetation eventually shifts to trees first pines and then oak Differences in tree species based on moisture availability 2012 Pearson Education Inc Glacial till Newly deposited alluvial soil on a floodplain represents another example of primary succession Glacier Bay National Park Alaska Over the past 200 years the glacier that once covered the entire region has been retreating The newly exposed landscape is initially colonized by a variety of species Grand Pacific GI Muir GI Riggs GI Canada j Alaska McBride Gla 194Jz 1sa12 1945 1907 Plateau GI 39 1899 1 1941 1907 h79 1931 39 CasememGI 1 7 1931 1892 1900 7 1879 1879 1892 i 1913 1935 1949 1880 H Muirlnlet 1 quot 7 a 1 1860 J h Field GI 7 1 a 1857 HO nk39 1879 1 Bear Track Giap ms 1860 Glacier 1845 COVe 39 Bay 1830 1780 V Bartlett Cove 1 391760 O 8 16 24 111 7 km V Pleasant 2012 Pearson Egacation Inc Number of plant species Primary succession on glacial till During succession ai Glacier Bay the number of plum species increased rapidly for he rst 200 years and then 60 began to level off l l l L000 1500 2000 Years l 0 500 Secondary Succession Occurs After Disturbances Old field succession in the Piedmont region of North Carolina Annual crabgrass is the first species to grow after a crop field has been abandoned In the second years horseweed quickly claims the field white aster and ragweed also invade By the third summer broomsedge invades and soon dominates Pine seedlings establish and within 5 to 10 years the pines are tall enough to shade the broomsedge Eventually hardwood species take over the field 8000 D C O O L O O O Stems per acre O 20 4O 60 80 100 1 20 Years 2012 Pearson Education Inc Marine Secondary Succession Studies of physical disturbance in marine environments have demonstrated secondary succession in various communities Seaweed Salt marsh Mangrove Seagrass Coral reef Kelp forest Succession in the subtidal kelp forests of Torch Bay Alaska One year after the removal of kelp forest a mixed canopy and understory of kelp species formed During the second and third years the community returned to the original composition Seagrass Secondary succession of seagrass communities in Florida Bay Wave action and heavy grazing creates openings in the grass cover exposing underlying sediments subsequent erosion results in blowouts Rhizophytic macroalgae gt contributes to sediment Haodue wrightii colonizes gt stabilizes the sediment surface Thalassiz testudinum eventually colonizes the area and again resembles the surrouding seagrass community Udotea Penicilus Halimeda Haodue wright391 Time after disturbance 2012 Pearson Education Inc Ecological Issues American Forests ll 1 W 7 iii iii Old field communities commonly occur in the eastern United States and represent the early stages of secondary succession 0 When European colonists first arrived on the eastern shores of North America 16005 the landscape was dominated by forest Native Americans had used fire to clear areas for planting crops but this had minimal impact on the landscape 0 The clearing of forest by settlers was driven by the need for agricultural lands and forest products By the 19005 most of the forest in eastern North America had been felled The trend was reversed in the Dust Bowl period in the 19305 0 With the advent of mechanization of agriculture small family farms gave way to large commercial farms By the 19305 the amount of agricultural land in the east had peaked and it has been declining ever since 1 860 1 869 sop km 300 Miles 2012 Pearson Education Inc Acres cleared in millions 1 370 1 B79 300 ivliles Acres cleared in millions Cottomarl rabbit M mouse Black lhroated green warbler Meadow mouse x Nasth warbler sparrow a m Meadowlark 39V Wk Z 3N u Grass l Lowshrubs I Highshrubs Shrubs irees Opening Low trees I High trees Twme years 2012 Pearson Education In Secondary succession in temperate forests Number of woody plant species begins to leVel off 0 r afteraboul 100 I0 150 years v J 8 50 3 73 40 i O O U 3 P 3 3 0 5 e E 7 2 0 N I I I I l I I 0 50 100 50 200 Years Number of bird species Number of bird species leveled off after 50 to 100 years of forest succession 50 100 Years 150 200 Forest Succession Early succession quotopportunisticquot or quotpioneerquot species produce great quantity of seeds that are disseminated by the wind capable to germinate and grow under direct sun Closed canopy shade prevents germination of pioneer species shade quottolerantquot species become established under pioneer and replace pioneers as they die Eventually climax community community that will persist until disturbance occurs again Succession Is Associated with Autogenic Changes in Environmental Conditions 0 Autogenic environmental change is a direct result of the presence and activities of organisms within the community Vertical profile of light in a forest is a direct result Of the Vegetation structure 0 Allogenic environmental change is governed by physical processes Decline with average temperature with elevation In both primary and secondary succession plant colonization alters the environment eg light Alteration of light environment In the early stages of plant succession shadeintolerant species can dominate Shadeintolerant species grow above and shade the slowergrowing shadetolerant species Eventually shadeintolerant species cannot grow and survive in the shaded conditions Succession results from changes in the relative tolerances and competitive abilities of species under autogenically changing environmental conditions Species Diversity Changes during Succession Chronosequences chronoseres are groups of sites used to compare patterns of diversity through succession Some studies have shown that plant diversity increases with site age old field communities Other studies showed a different pattern Species diversity increases with herbaceous stages decreases into shrub stages increases again in young forest and finally decreases as the forest ages Number of species I I l I I 1 2 4 6 101420 50 100 200 Successional time years Stage Herb Shrub Tree stages 2012 Pearson Education Inc Community Structure Changes Over Geologic Time Earth39s surface has changed profoundly over the past 46 billion years Paleoecology is the study of the distribution and abundance of ancient organisms and their relationship to the environment Reconstruction of plant distribution after the last glacial maximum Laurentian ice sheet of the Pleistocene Climatic oscillations between cold and temperate Historic occurrence and distribution of plant species is indicated by the pollen record of sediment cores Shifting distribution of tree species in North America following the last glacial maximum 19000 years ago K r 39 E39VR r I 0 Rx EHW A Ni 9k qult 3 V1 01 18000er BOOOyrBP a b 2012 Pearson Education In Ch 20 Landscape Dynamics 2212 12 Landscapes 0 A community is a group of species occupying a given area Ecological communities have a spatial boundary and a spatial context within the larger landscape Terms A mosaic is the patchwork of different types of land cover The landscape mosaic is defined by changes in the physical and biological structure of the distinct communities called patches Landscape ecology is the study of the causes behind the formation of patches and boundaries and the ecological consequents of these spatial patterns on the landscape Environmental Processes Create a Variety of Patches in the Landscape Patches are relatively homogenous community types that differ from their surroundings in structure eg size shape and in species composition 0 Human activity makes its mark on the broad scale distribution of communities Habitat fragmentation of the natural landscape into isolated patches of forest grassland and shrubland miles Zolaalpearson Education Inc miles 1 0 miles Landscape patches vary considerably in size and shape Determined by variations in geology and soil conditions and natural events fire and grazing The area shape and orientation of the landscape patches influence Habitat suitability Wind flow Dispersal of seeds Movement of animals Transition Zones Offer Diverse Conditions and Habitats The edges ofthe landscape mark the perimeter of each patch Inherent edges are stable and permanent Induced edges are subject to successional changes over time 0 A border is the place where the edge of one patch meets the edge of another Narrow and abrupt Wide with a transition zone or ecotone Perforated Straight Convoluted Edge A Edge B Original edges Narrow Straight Wide border Convoluted Perforated border Sharp ecotone border border abru i p b c d to 2m 2 Fuarinn Education Inc 2012 Pearson Education Inc Borders 0 Borders vary in length and have an associated vertical structure Borders connect patches through fluxes of material energy and organisms The height width and porosity of borders influence the gradients of wind flow moisture temperature and solar radiation between adjoining patches Edges 0 Environmental conditions in transition zones enable certain plant and animal species to colonize border environments Plants tend to be more shade intolerant and can tolerate dry conditions Animals usually require two or more habitat types within their home range Edge species are those restricted exclusively to the edge environment Edge Effect 0 Borders blend elements from all adjacent patches and offer unique habitats with relatively easy access to adjacent communities The edge effect is the phenomenon where edge communities are often quite diverse The edge effect can also create problems Attracts more predators Restricts dispersal Patch Size and Shape Are Crucial to Species Diversity Large habitat patches contain a greater number of individuals population size and species species richness than do small patches 0 The increase in population size is a function of the increasing carrying capacity for the species More area gt more home ranges and territories Larger patches are more likely to contain variations in topography and soils Greater diversity of plant life gt a wider array of habitats for animal species Patch size and shape affect the relative abundance of edge and interior environments Only a larger patch can develop interior conditions Interior species require conditions characteristic of interior habitats and stay away from the abrupt changes associated with border environments The probability of finding certain species may increase or decrease with patch size depending on whether they are edge or interior species The Theory of Island Biogeography Applies to Landscape Patches 0 Early explorers noted that large islands hold more species than do small islands JR Forster on Captain Cook s voyage 1772 75 P Darlington on islands a tenfold increase in land area leads to a doubling of the number of species 0 The various patches that form the vegetation patterns across the landscape suggest islands of different sizes The theory of island biogeography has been applied to the study of terrestrial landscapes R MacArthur and EC Wilson developed this theory in 1963 The number of species established on an island represents a dynamic equilibrium between the immigration of new colonizing species and the extinction of previously established ones Immigration Rate gt Extinction 8 Number of species gt 2012 Pearson Education Inc Species on the mainland are the possible colonists to an uninhabited island The species with the greatest dispersal ability will be the first to colonize the island The immigration rate will decline as the number of species on the island increases Few quotnewquot species left to colonize The immigration rate will be zero when all mainland species exist on the island The rate of species extinction on the island will increase with species number Based purely on chance Later immigrants will have less access to habitats and resources Competition will increase An equilibrium species richness S is achieved when immigration rate extinction rate Equilibrium species richness 5 is affected by The distance of the island from the mainland Size of the island Immigration Extinction Rate gt Number of species gt 2012 Pearson Education Inc Rate gt b Extinction Immigration Number of spectes gt quotAny patch of habitat isolated from similar habitat by different relatively inhospitable terrain traversed only with difficulty by organisms of the habitat patch may be considered an island D Simberloff Mountaintops Bogs Ponds Dunes Areas fragmented by human land use Individual hosts of parasites Landscape Connectivity Permits Movement between Patches 0 In some situations corridors connect patches of similar habitat Strips of vegetation similar to the patches that they connect Many corridors are of human origins eg windbreaks drainage ditches Connectivity is the extent to which a species or population can move among patches within the matrix Pearson Education Inc b 2x114 Pearson Education In Corridors facilitate the movement among different patches and can encourage gene flow between subpopulations and help reestablish species in habitats that have experienced local extinction Different sized gaps in corridors allow certain organisms to cross while restricting others 0 Negative impacts of corridors They offer scouting positions for predators Avenues for the spread of disease Provide a pathway for the invasion of exotic specres If too narrow they can inhibit the movement of social groups Corridors may provide habitats especially in suburban and urban settings Roads dissect the landscape and have effects on adjacent patches of land All types of roads affect roadside vegetation Salt spread during snow removal Particulate matter from tires and exhaust Chemical pollutants from automobiles 0 Where roads invade people and development follow Wildlife crossing Frequency Intensity and Scale Determine the Impact of Disturbances A disturbance is any relatively discrete event fire windstorm flood extreme temperature drought or epidemic that disrupts community structure and function Disturbances create and are influenced by patterns on the landscape Disturbance regime Intensity is measured by the proportion of total biomass that is killed or eliminated influenced by the magnitude ofthe physical force involved Scale refers to the spatial extent of the impact relative to the size of the affected landscape Frequency is the mean number of disturbances that occur within a particular time interval A gap is generated by a small scale disturbance and becomes a site of localized regeneration and growth within the community Within a gap the physical often differs substantially from conditions in the surrounding area Large scale disturbances eg fire logging result in substantial reduction or even elimination of local populations and significantly modify the physical environment Followed by a period of colonization Various Natural Processes Function as Disturbances Disturbance is a powerful force for change in the physical environment Many disturbances arise from natural causes Wind and ice storms Moving water eg waves Hurricanes Floods Lightning fires Grazing Animal activity Fire 0 Fire is a major agent of disturbance and can be a major determinant of landscape patterns with the following effects Release of nutrients though pyromineralization Preparation of the seedbed Can lead to an increase in light water and nutrient availability to the surviving and colonizing plants Grazing Grazing by domestic and native herbivores can cause disturbance Domestic cattle spread seeds of mesquite and other shrubs in grasslands of the southwestern United States Overpopulations of white tailed deer have decimated the forest understory in eastern North America The African elephant is considered a major influence on the development of savanna communities Animal Activity 0 Beavers modify many forested areas by damming streams they alter the structure and dynamics of flowing water Snow geese have affected brackish and freshwater marshes resulting in erosion Insect Outbreaks Outbreaks of insects eg gypsy moths spruce budworms defoliate large areas of forest and cause the death or reduce the growth of affected trees Human Disturbance Creates Some of the Most LongLasting Effects Human activity is ongoing and involves continuous management of an ecosystem gt a more profound affect than natural disturbances Cultivating cropland for agriculture Timber harvesting Shifting Mosaics The community mosaic is ever changing due to large and small disturbances A shifting mosaic is composed of patches each in a phase of successional development The current mosaic of land cover is maintained by active processes many of which are forms of human induced disturbance III III lilll lEilll Iii ll IE I ll ill IE EQI i i Early succession Late succession i Mid succession Gap n Inc 7 2012 Pearson Educatio


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