F 311 1st Edition Exam 2 Study Guide Week 6 Ecosystems and Soils Soils What is it made of Forest ecosystems can only be sustained if soils are sustained Minerals size coarse fragment sand silt clay make up 45 Organic Materials 5 of soil half of chemical reactions occur here Pores air water 50 pores Mineral Particle Size and organic matter Clay very small 2 micrometers 10 6 Silt Medium between 2 micrometers and 50 micrometers Sand Large between 50 micrometers and 2 millimeters Clays have the most surface area and sand has the least therefor clay holds on to water more strongly and holds more water Coarse texted soils have higher flow rates of water Soil particles bound together to form aggregates Macropores space between aggregates Warmer soils have more organic matter because there is more decomposition and production in the soil Soil element nutrients for plants and effect of nutrients on growth Trees need more than a dozen elements C O and H are the three biggest these elements come from the atmosphere and water N P Ca K and Mg are important as well N and P limit forest growth Ca K and Mg sometimes limit growth More nutrients commonly means more growth N needed for proteins enzymes DNA P needed for ATP lipids DNA K needed for activating enzymes salt levels Ca needed for cell walls Mg needed for chlorophyll enzymes Micronutrients Iron manganese Zinc Boron These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Fertilizing soils increases production of forests it produces more leaves and more growth per leaf can be twice as profitable when comparing cost of fertilizer and production Some plants have evolved to fix nitrogen with N fixing bacteria that breaks the N2 bond in the atmosphere many legumes do this adding N fixing plants can increase the productivity of surrounding plants Compaction Fertile soils have pore spaces for air and water roots also need pore spaces to be able to push through soils The more compaction in a soil the less pore space this makes it harder for roots to penetrate the soil Bulk Density Dry mass of the soil per unit of soil volume in kg L Coarse Fractions Stones and rocks Soil development over time Soils develop on original parent material Soil change over time does not necessarily affected growth or production Soils change dramatically in a season and through generations Week 7 Productivity and Growth Decline NPP GPP and tree carbon balance limitations NPP GPP respiration GPP Photosynthesis of the whole ecosystem R metabolic costs for growth and metabolism NEP NPP what dies and decomposes Tree carbon balance GPP Foliage NPP 4 13 Wood NPP 9 47 Foliage Rs 10 31 Wood Rs 4 25 TBCA root production resperiation exudates mycorrhizae 26 62 Production ecology equation Production can be measured as mass or by the energy content of the mass biologic materials have similar energy contents Production resource supply x proportion of supply captured x efficiency of using captured resource Wood production production respiration and allocation to other tissues Diameter and biomass growth of individual trees Trees slow down in diameter growth while accelerating in stem mass growth This is because mass goes up faster in relation to diameter as diameter increases Greatest total wood production always comes at highest density but high total volume for dense stands comes at a cost The average tree per acre goes down as tree size increases Tree and forest lifespan Forests all show a decline in wood production with age usually after leaf area peaks on trees Forest age may alter water use and runoff The basis of econ decisions in forestry is the length of the rotation Wood growth often peaks at canopy closure and declines from there Hypotheses for stand growth decline with age size Key problem in forest biology is figuring out where does CO2 go once it reaches the forest Working with fast growth forests comparing physiology of young and old trees are ways of studying the C02 question Fast growing tropical plantations are great for experiments because they are easy to manipulate Hypothesis 1 Wood growth declines because of increased respiration disproved Hypothesis 2 Reduced nutrient supply with stand development reduces wood growth disproved Hypothesis 3 Increased allocation to non woody components reduces wood growth disproved Hypothesis 4 increased dominance causes a decline in wood growth because subordinate trees are less efficient at using resources meaning less photosynthesis or more allocation away from wood disproved Hypothesis 5 Decreased GPP causes a decline in wood growth because nutrient supply drops or hydraulic limitation or genetic change or growth limitation supported A decline in canopy photosynthesis not respiration or nutrition caused a growth decline in Eucs Estimating GPP is hard to do measure all components and estimate GPP by sum Ultimate reason for decline in photosynthesis and efficiency remains a mystery Self thinning Self thinning is the non rapid amount of mortality in a forest The ability of one tree to dominate another by using up the sites resources depends on the difference in sizes of trees The size relationship often looks like a slanting line on a graph where you can easily get the slope Week 8 Succession CAI and MAI CAI current annual increment volume growth rate for current year or between measurement periods vol vol1 age age1 MAI mean annual increment average volume growth rate over entire life of stand vol age Succession definition and arguments against it Succession physical environment modified by the community orderly process of community development that is directional and predictable culminates in a stabilized ecosystems climax system where maximum biomass and symbiotic function between organisms are maintained per unit of available energy flow vegetation alters site and prepares for its next arrivals Clements relay florists species colonize suitable sites in a scramble and far dispersers or fast growers dominate at first Gleason initial florists disturbance changes communities and can restart the clock of succession or shift a system into different states Arguments against succession 1 Succession is not a process 2 Specifics of ecosystem change are unpredictable and influenced by numerous legitimate processes that vary in importance over space and time 3 On the ground evidence of succession is rare climax ecosystems are only temporary