soils Flashcards

Question

5 types of chemical sedimentary rocks

Answer 1

1. limestone - CaMg(CO3)2 2. evaporites - Na and Ca chlorides and sulphates 3. ironstone - oxides and hydroxides of Fe and Al 4. hydrothermal deposits - black smokers 5. organic - coal, oil

Answer 2

Harder and more resistant to erosion and weathering than original rock. Formed by transformation of igneous and sedimentary rock by 1. heating 2. pressure 3. heating + pressure 4. compression + shear

Answer 3

1. magma at center of earth consisting of primary mineral material rises to crust where crystalizes (externally and internally) to form igneous rock. 2. rocks are weathered and eventually form the substrate of soils (pedogenesis). 3. Sediments are further eroded and transported away to rivers, lakes, and oceans where they are sedimented. 4. Sediments compacted down by own weight (diagenesis) to form sedimentary rocks. 5. Sedimentary rocks undergo metamorphosis via subduction into deeper areas of earth's crust to become metamorphic rocks. 6. Come back to rising magma (anatexis) to become metamorphic rocks oncemore.

Answer 4

Sediments and soils.

Answer 5

1. intensity of process 2. strength/resistance of rock and minerals

Answer 6

1. physical: physical disintegration of rocks and minerals. facilitated by freeze-thaw cycles, variations in water content and temperature, and biological activity. 2. chemical: chemical transformation of minerals into new products. facilitated by high temperatures and high biological activity, the production of organic acids and co2 in the soil, and by acidity.

Answer 7

the breakdown of rocks and minerals. crucial to soil formation.

Answer 8

1. Freeze-thaw weathering: water fills small cracks in rocks and freezes, expanding in volume and cracking the rock apart through release of pressure. 2. Thermal changes: variations in temperature lead to different rates of expansion and contraction amongst minerals and rocks. There is a larger night/day temperature amplitude in desert because of low cloud cover (less ghg effect -longwave outgoing radiation is lost into space). 3. Salt weathering: formation and growth of salt crystals in pores and cracks of rocks creates strong pressure, leading to disintegration of rocks. 4. Biological: root systems of plants infiltrate rocks, grow and split it apart.

Answer 9

1. Direct solution : dissolution of soluble salts 2. Hydration: minerals absorb water molecules, disintegrating or forming different minerals. 3. Redox: change in valency of element 4. Chelation: reaction of insoluble elements with complex (eg Fe, Al), organic compounds produced by decomposition of organic matter. 5. Carbonation: reaction of carbonic acid (H2CO3) with carbonates. 6. Hydrolysis: reaction of H+ ions with cation in mineral. occurs with H+ from co2 dissolution in water or from acidic rain with the exchange of cation in mineral lattice with hydrogen.

Answer 10

Igneous > metamorphic > sedimentary

Answer 11

hotter + wetter --> strong chemical weathering colder + drier --> strong physical weathering (freeze thaw cycles, thermal variations between day and night)

Answer 12

1. bedrock is exposed to atmosphere --> physical and chemical weathering processes that disintegrate rock 2. pioneering organisms, mostly lichens, have opportunity to set roots 3. Accelerates physical (root systems) and chemical (exudes organic essences) weathering. 4. Biomass accumulates, slowly developing parent material. C horizon forms below parent material. Organic layers grow in depth until A horizon is formed at top of ground. 5. Soil horizon becomes more mature as weathering processes continue, growing downward in depth untill B horizon is formed (between A and C). 6. Larger plants such as trees and brushes set roots as soils are more developed.

Answer 13

1. O horizon: organic material, almost black 2. A horizon: mixture of mineral fragments and organic material. Darker brown/grey. 3. E horizon: transition zone between A and B horizons. lighter brown in colour. 4. B horizon: sub soil. often brown in colour. 5. C horizon: weathered bedrock. 6. solid bedrock

Answer 14

1. Additions - Precipiation (with included ions and solid particles) - organic matter 2. transformations - organic matter decomposes to become humus. - primary minerals undergo chemical rxns to form hydroxous oxides, ions, h4SiO4 and secondary minerals such as clay. 3. transfers - transfers down: humus compounds, clays, ions, h4SiO4. Ocurrs via movement of rainwater down. - transfers up: ions, h4SiO4. Occurs via transfers of capillary rise of groundwater 4. removals - ions, h4SiO4 - mostly due to leaching as water percolates into soil and sometimes runs off - erosion is the most important removal process in soil

Answer 15

1. parent material - sediment type, minerology, ease of weathering 2. climate - temperature and precipiation 3. time - older soils more strongly developed than younger soils 4. organisms - eg deciduous vs coniferous forest, grassland vs forest 5. topography - controls water regime, wet vs dry, and rates of soil erosion 6. human activity - framing practices, land degradation, tilling, deforestation

Answer 16

1. Different mineralogies have different chemical compositions, some more acidic, some more basic. The more acidic = the more difficult to weather. 2. Geologic processes might bring different rock layers to the surface, affecting nutrients and ph. 3. sedimentation processes - fluvial sedimentation during flooding - parent material might come from far away and have been transferred downstream, not necessarily underlying. Sediments left behind are often rich in silt. 4. other processes that might include parent material not derived from rock - volcanic eruptions - glaciation --> move material across surface -high winds --> carries dust and soil particles from one place to another

Answer 17

Increased precipitation + temperature --> increased rates of weathering + chemical alterations (ie decomposition) --> more developed, deeper soil profiles. increased precipitation --> base cations which puffer pH against acidity will be leached out and soil will become more acidic.

Answer 18

grasslands - more below-ground biomass - thick Ah horizon, thinner B horizon - high ph, higher fertility, higher nutrient availability forests - more above-ground biomass - thinner A horizon, thicker B horizon - lower ph, lower fertility, lower nutrient availability - tree roots create channels in soil for water to come through

Answer 19

steep slope = free drainage flat surface = poor drainage

Answer 20

1. texture 2. pH 3. organic matter content

Answer 21

gravel > sand > silt > clay

Answer 22

particle - size determines how soil responds to particular hydrology mineral - chemical composition of particle

Answer 23

1. influences soil infilitration rate, determination rates of overland flow and soil erosion. 2. influences soil permeability and therefore drainage 3. controls available water capacity of soil - determines ability to supply water to plants for transpiration 4. influences soil structure, allowing root growth and aeration. 5. provides cation exchange capacity for retention of Ca, Mg, K supply to plants and buffering against acid rain.

Answer 24

optimal conditions for plant growth is between sandy loam and clay loam sand (large particle size)= low field capacity, slow wilting point --> less available water since soil drains quickly but plants can easily take up this water from soil clay (small particle size)= large storage capacity, field capacity, relatively quick wilting point --> sheet like structure = large surface area --> more available water but holds on to water and plant nutrients very tightly

Answer 25

amount of water left behind in soil after three days of drainage.

Answer 26

the amount of water per unit soil volume that is held so tightly by the soil matrix that roots cannot absorb this water and a plant will wilt.

Answer 27

Important control of pH and soil nutrition. Plant exude base cations or respire, adding acidity into system that can be buffered by base cations.

Answer 28

the balance between input and output establishes the amount of organic matter in soils. input = dead plant and animal tissues output (as co2) = from decomposition by organisms (bacteria, fungi, earthworms..) greater npp --> greater input (more organic matter) greater rate of decomposition --> greater output (less organic matter)

Answer 29

higher temp + precip = higher npp and decomposition tropical forest (higher temperature, higher rainfall) - hold not as much as take in because rate of decompostion so high temperate forest (colder temperatures, lower rainfall) - low npp but slow decomposition = high organic matter content. carbon from atmosphere more efficiently stored in system boreal forest (cold + dry) - most efficient carbon storage - very high organic matter content bog - very high water content -> low ph due to leaching of base cations + anaerobic soil --> less microbe activity --> lower rate of decomposition -nearly 100% organic matter content in soil because have very little output

Answer 30

1. temperature and precipiation 2. plant tissue type - tissues rich in N and P decompose quickly because nutrients are used by organisms in the soil - pine needles are acidic 3. soil properties - fertility - increase - texture - organisms - increase

Answer 31

1. Improves soil structure and porosity - increases infiltration rate and available water capacity 2. supplies nutrients (Ca, Mg, K, N, P) to plants through slow decomposition. 3. Humus (part of soil organic matter) possesses a high cation exchange capacity leading to retention of cations (Ca, mg, k) and buffering against acid rain.

Answer 32

1. determines environmental conditions 2. determines availability and accessibility of soil nutrients 3. determines what community life can be supported

Answer 33

the comparative concentrations of H+ (more acidic) and OH- ions (more basic). higher precipiation = lower pH the more water that perculates through the soil column, the more base cations that buffer against acidity will be leached from the soil. Higher temperature higher temperature = lower pH the molecular vibrations in the solution rise resulting in the ionization and formation of H+ ions.

Answer 34

1. Low soil pH can lead to aluminum toxicity for plants 2. Determines nutrient availability, in particular that of phosphorous. 3. Influences cation exchange capacity 4. Influences earth worm activity and other fauna in soils 5. strong influence on microbial community in soil.

Answer 35

colour, depth, texture, structure, moisture

Answer 36

how different cultures around the world describe soils. Many cultures have traditionally names for various classes of soils that help convey the people's collective knowledge about their soil resources.

Answer 37

Hierarchal structure from orders to families. retains old European names that contain info about soil that makes communication easy. categorical levels 1. order: properties that reflect the environment and soil forming processes. 2. great group: subdivision of order reflecting differences in dominant processes. 3. subgroup: differentiated by content and arrangement of horizons. 4. family: differences in texture, mineralogy, climate and chemistry 5. series: detailed features of the pedon differentiate subdivisions of the family.

Answer 38

Soil horizons are named and standardized as diagnostic in the classification process. Several mineral and organic horizons are used. 3 mineral horizons A = mineral horizon formed at or near the soil surface B = accumulation of material from ae horizon or by alteration of parent material C = horizon with little evidence of pedogenic activity 4 organic horizons: O = organic material L = litter litter, readily recognizable F = partially decomposed leaf and twig material (folic material) H = humic material, decomposed organic materials with no original structures.

Answer 39

provides a global vocabulary for communicating about soils since many countries have their own system. consists of 32 soil reference groups, differentiated mainly by the pedogenic process (eg accumulation of clay) and the parent material (eg volcanic ash).

Answer 40

1. weathering of minerals from rocks (rock derived nutrients ca, mg, k, and p) 2. death and decay of vegetation (litter, soil organic matter provides N and P) 3. atmospheric deposition dry and wet (N and particulates containing Ca, Mg, and K)

Answer 41

1. plant uptake and harvest 2. erosion 3. atmosphere (loss of gaseous forms of N) 4. ground water table and streams through leaching and erosion.

Answer 42

primary: n, p, k secondary: ca, mg, s

Answer 43

fe, mn, zn, cu (copper), b, mo, cl, si, co

Answer 44

undisturbed system: cycling is 'tight' with inputs relatively equal to outputs disturbed system: cycling can be "loose", with outputs > inputs

Answer 45

ease of loss : N > K > Ca > P N as NH4+ on clays but No3- is very mobile in soils base cations (ca, mg, k) on cation exchange complex (from clay and organic matter) phosphgate retained most tightly due to negative partial charge. strongly absorbed on clays, Fe-Al oxides/hydroxides, and Ca.

Answer 46

Nitrification and P sorption control plants prefer to take up nitrate because it is an anion, meaning it is mobile in the soil, and translocates quickly. ammonium is a cation so it is retained in the soil. control of retention of nutrient in soil matrix is controlled by the soil pH and the base cation supply to plants.

Answer 47

1. nitrogen fixation: incorporation of N2 from atmosphere. 2. mineralization: decomposition of organic matter to mineralize N as ammonium (NH4+) - soil microorganisms fix atmospheric nitrogen and form ammonia (NH3). NH3 is a precursor of amino acids that later becomes mineralized to form NH4, a cation that is very reactive with soil organic matter and clay surfaces. 3. nitrification: conversion of NH4+ to nitrate (NO3-) - bacteria use ammonium as energy source and form nitrite as waste product (=toxic to plants and a potent GHG). Another strain of bacteria oxidizes nitrite to form nitrate, a nutrient that plants can take up. Over leaching into groundwater of nitrate can make water toxic but humans have enzyme that ensures doesn't become toxic. 4. denitrification: conversion of NO3- to N2 and nitrous oxide (N2O) by microbes. 5. leaching: loss of soluble NH4+ nad NO3- to surface and ground water.

Answer 48

1. phosphros enters cycle through weathering of minerals, dust deposition, decomposition (mineralization) of organic matter, usually as organic / inorganic phosphate (PO43-). 2. solubilization: dissolution of phosphorous from soil minerals. 3. sorption: chemical process by which p becomes attached to surfaces of soil particles. Due to high negative charge, phosphates sorb strongly to iron and aluminum oxides and clay minerals. 4. Mineralization: decomposition of organic matter (enzymatic hydrolysis of organic P compounds) to release inorganic phosphate (PO4 3-) 5. Immobilization: uptake of inorganic P by plants and microorganisms and subsequent transformation to organic P. 6. Leaching: loss of soluble organic and inorgic P to surface and ground water.

Answer 49

Ph controls the availability of phosphate in soil nutrition. pH < 6 As ph becomes lower (ex through acid rain), phosphates will react more with iron and aluminum and become chemically fixed (occlusion). Less phosphate is available to plants because it is transferred into chemical species that plants can access. ph 6-7 phosphates are relatively available. ph > 7 As pH becomes higher, phosphates react strongly with calcium, forming calcium phosphate minerals that are not available to plants but not strongly occluded.

Answer 50

Takes out a lot of phosphates fixated in pools faster than can be replenished by natural pathways from other pools.

Answer 51

1. input via weathering and dust deposition 2. solubilization: dissolution of potassium from soil minerals. 3. sorption: chemical process by which K+ becomes attached to surfaces of soil particles. 4. Immobilization: uptake of K+ by plants and microorganisms 5. Leaching: loss of soluble K+ to surface and groundwater

Answer 52

N - nitrogen deficiency causes pale, yellowish green corn plants with spindly stalks. symptoms appear on leaves as a v shaped yellowing, starting at the tip and progressing down the midrib toward the leaf base. P - deficiency is usually visible on young corn plants. it readily mobilizes and translocates in the plant. Plants are dark green with reddish-purplish leaf tips and margins on older leaves. k - deficiency is first seen as a yellowing and necrosis of the corn leaf margins, beginning on the lower leaves.

Answer 53

Rich countries use more fertilizer than poor countries. As china started to farm more intensively, they needed more fertilizer. States that don't regulate fertilizer --> more fertilizer applied than needed. issue = - fertilizer feeding soils rather than plants because more is applied than plants can take up - P and N (as nitrate bc mobile) carried overland via runoff or leaches into groundwater. - leads to transfer of nutrients from land to aquatic ecosystem - primary pathway for nutrient pollution, other than atmospheric nitrgous deposition (amonious gasses volatize into atmosphere, form ammonium, which is deposited downwind in ecosystems).

Answer 54

excessive nutrient concentrations --> excessive plant growth (algal blooms / cyanobacteria) --> dead plant material accumulates in water column --> decomposes and depletes dissolved oxygen in water collumn --> aquatic organisms die cyanobacteria produce younger toxins which make drinking water unpotable and restrict recreational activities --> large economic damage

Answer 55

1. freshwater runoff creates layer of freshwater in gulf, cutting off saltier water below from contact with oxygen in the air. 2. nitrogen and phosphorous from fertilizer and sewage in the freshwater layer ignite huge algae blooms. when the algae die, they sink into the saltier water below and decompose, using up oxygen in the deeper water. 3. starved of oxygen and cut off from resupply, the deeper water becomes a dead zone. fish avoid the area or die in massive numbers. tiny organisms that form the vital base of the gulf food chain also die. winter brings respite, but spring runoffs start the cycle anew.

Answer 56

1. reduce fertilizer application rates and increase efficiency in application (ex precision agriculture) 2. improve wastewater treatment technology and ban nutrient additions where unnecessary (ex phosphates in detergents) 3. nature-based solutions ie vegetated riparian buffer strips, and wetland restoration.

Answer 57

- intercept nutrients before reach stream. If roots are deep enough, they can intercept subsurface flow nutrients. - promote denitrification in streams and rivers

Answer 58

addition of proximate limiting nutrients stimulate biological processes and growth. ex nitrogen - moves quickly so impact kicks in faster but solutions will also have immediate impacts. addition of ultimate limiting nutrients leads to transformation of whole ecosystems and or species composition ex phosphorus - accumulates in soil, held tightly and released slowly. residence time is much longer so difficult to solve. have legacy p in soils from years ago. P changes whole ecosystem because allows plants to fix nitrogen from atmosphere efficiently such that blue green algae can grow rapidly.

Answer 59

the wearing away of the topsoil by the natural physical forces of water and wind or through forces associated with human activities (e.g. tillage, cattle grazing, tree harvest).

Answer 60

soil which is high in organic matter, fertility, and soil life

Answer 61

reduces the productivity of croplands and natural ecosystems and contributes to the pollution of adjacent watercourses, wetlands, and lakes.

Answer 62

1. soil creep: slow downslope movement of soil particles in response to disturbances (expansion/ contraction with wetting/drying, soil faunal activity etc). very slow rates (< 0.05 tons ha-1 yr-1) that increases with slope angle. 2. landslides and earthflow: rapid mass movements when soil strength is exceeded by gravity, usually follows heavy rainfall. 3. fluvial: by running water. By far the most important form of erosion. 4. Aeolian: wind removal of surface layer; requires absence of protective vegetation cover, dry soils and strong winds.

Answer 63

1. raindrop impact and splash - detaches soil particle and destruction of soil structure. making it easier for mobilization by overland flow 2. creation of overland flow - transport particles in downward direction 3. deposition - deposited in small hollows along hill slope or at bottom of hill. - fertile soil may accumulate at downslope but might suffocate young seedinglings and has no structure (poor aeration --> poor redox potential)

Answer 64

1. sheet erosion - whole areas erodes in fairly homogenous manner 2. rill erosion - steeper hillslopes have small channels where water flows faster ex plowing lines in agricultural fields. 3. gully erosion - enhanced rill erosion. if continues to occur for many years it becomes a gully (deep and wide crevace). can occur very quickly with large rainfall events.

Answer 65

Largely consists of silt that was transported away during ice age through wind erosion and deposited in areas where there was a windshield. Productive, fertile region where food production is occurring. ex china loess plateau tibetan plateau served as wind shield to slow down westerly winds. eroded material transpoted downstream to small channels and rivers, entering into the Chinese sea and depositing material in the yellow river delta. Characterized by deep gully erosion all around farming systems on steep terraces.

Answer 66

In forest, a large part of rainfall is intercepted and infilitrated and a small part becomes overland flow. In unimproved pasture, all rain hits the ground. because of cattle, soil has been compacted and the structure is destroyed, severely reducing infiltration and increasing overland flow --> increasing erosion. Sheet erosion on agricultural fields depsoit material at far end of field, suffocating the crops located there. topsoil eroded away from field --> infertility.

Answer 67

1. collect soil downslope in troughs and measure the amount of soil that has been eroded over distance and area. - simple but imprecise 2. measure loss of soil against stable existing surfaces ie tree roots - tree roots sticking out of ground indicate that in the past there was soil much higher.

Answer 68

A = R x K x LS x C x P where, A = erosion rate (tons ha-1 yr-1) R = rainfall erosivity K = soil erodibility LS = combination of length and slope of field C = crop type (bare soil=1, crops=<1, forest=near 0) P = conservation measures applied (no conservation=1, contour ploughing is high, terracing is low) A, R, K defined by farmers can alter all factors to limit erosion.

Answer 69

1. rainfall intensity: affects the creation of overland flow by exceeding soil infiltration rate. 2. rainfall energy: higher kinetic energy + mass --> increased ability to splash soil particles downslope and destroy soil aggregates

Answer 70

1. soil infilitration rate (sand > loam > clay) 2. ease of detachment of soil particles (silt > clay > sand) - silt easier to detach than clay even though larger and heavier because of ease of detachment from soil particles vs clay sticks together with soil organic matter. 3. ease of transport of soil particles (clay > silt > sand > gravel)

Answer 71

1. length of slope - longer slopes = greater cumulative overland flow from upslope, leading to faster movement, thicker layer and greater capacity to erode and carry soil. 2. slope angle (larger effect) - steeper slopes mean faster overland flow and greater capacity to erode and carry soil.

Answer 72

1. reduced water availability - increases surface runoff (reducing water for plant growth) - removes finer particles (clay, organic matter), leaving sand and gravel particles which have lower available water capacity, and thus ability to store water and supply crops. 2. reduced soil fertility - loss of fertilizers, especially N and P, by overland flow -removal of smallest particles which have highest available nutrient content and cation exchange capacity 3. reduces rooting depth for plants (shallower soils) 4. gully creation - loses agricultural land and increases accesibility costs of farming 5. greater energy costs - more plowing, tillage, seeding, and fertilizer needs 6. leads to positive feedback exposure of lower soil horizons by erosion --> decreases infilitration rates --> less vegetation --> increases overland flow --> more erosion --> exposure of lower soil horizons

Answer 73

1. change crop type or planting/harvest schedules (C) 2. protect soil surface and increase infilitration rate - add organic matter (mulch) or reduce tillage practices 3. change length and angle of field by creating terraces or ploughing parallel to slope (LS) 4. reduce grazing densities to allow grass cover: > 25% grass cover is critical in reducing erosion rates (C)

Answer 74

1. reduction of itensity of timber harvest (clearcutting only gentle slopes) 2. suitable methods of tree removal 3. scheduling of harvest during dry season or when ground is frozen 4. design and management of roads and skidding trails to ensure doesn't become flow path for erosion / rill creation 5. buffer strips along stream channels

Answer 75

1. sedimentation of eroded soil in river channels, dams, reservoirs --> eutrophication, pesticide pollution --> deteriorates water quality 2. increased frequency of flooding - increased surface runoff - channel volume may be reduced by deposited soil

Answer 76

1. creeping - large particles creeping on land surface 2. saltation - smaller particles jump 3. suspension - airborne particles in the wind

Answer 77

1. soil moisture 2. soil cover 3. tillage 4. barriers

Answer 78

shelterbelts - lines of trees that slow down wind before hit field

Answer 79

1. bacteria: important for biogeochemical cycling of elements, especially nutrients. 2. algae: ability to fix nitrogen to provide N to other organisms. 3. protozoa: regulate microbial population. can be parasites and predators. 4. fungi: thrive in moist, acidic, nutrient poor soils because good at decomposing dead biomass.

Answer 80

1. enhance nutrient and water uptake Mycorrhizal fungi colonize the root network called the rhizosphere. symbiotic relation= take carbohydrates from the plant, efficiently taking up nutrients through large surface area of hairlike rootings and provide that to the plant. 2. help with nematode pest (invasive species that damages harvest) 3. stabilize soil exude organic acids and a certain kind of protein rich gel that helps with root growth and plant uptake. Sticks cay minerals nad small organic compounds together, helping with development of soil structure. 4. important evolutionary role in helping plants adapt to the terrestrial environment

Answer 81

1. organic farming 2. cultivation of certain crops 3. continuous soil cover - after harvesting an additional plant is seeded that covers soil 4. mild soil tillage practices, mild pesticide applications

Answer 82

1. ingest and excrete large amounts of top soil 2. affect soil structure and nutrient availability, by mixing of organic and inorganic (mineral) fractions and stimulating decomposition of organic matter, further developing A horizon. 3. improve soil structure - crumblke --> allows for good aeration and penetration by plants 4. potential to increase pH and concentrate soil nutrients = ecosystem engineers bc change soil environment that live in

Answer 83

1. last glacial maximum mostly beneath line of last glacial maximum (US), mostly in east. 2. acidification and application of pesticides gets rid of earthworms 3. water availability 4. higher amount in forest soil than arable (cropping) soil

Answer 84

Earth mounts = sandier, more moist, more organic matter make earth mounts that have more sandy soil stuck together with mucus. higher water availability in mounds because mucus helps with retention of water. Organic matter brought in through transport system of termites. decomposed litter enriches the nutrients of mounds. Abondoned termite mounds can become islands of soil fertility in savannah landscapes and allow photosynthetic activity to persist even in drought.

Answer 85

Ph and soil nutrients is higher closer to entrance of prairie dog colony because of excretion of droppings and mixing of soils.

soils Flashcards

(110 cards)