Soils

Question 1

3 main important functions of soils

Answer 1

key ecosystem services, key biogeochemical services, human uses

Question 2

what two human factors are driving soil change

Answer 2

economic and population growth

Question 3

describe the initial stage of soil formation

Answer 3

bedrock is physically fragmented, minerals chemically decompose, minerals reconstituted to clays

Question 4

where do organic soils form

Answer 4

water-saturated environments

Question 5

what process leads to the breakdown of rock to form soils

Answer 5

mechanical weathering

Question 6

what are histosols, characteristics

Answer 6

organic soils, 40cm or more organic material in top 100cm. vulnerable to land use change

Question 7

how are histosols formed

Answer 7

nutrient runoff from the surrounding landscape leads to growth of aquatic veg. Organic debris fill water body and soil layers eventually form depending on the veg

Question 8

5 soil forming factors

Answer 8

time, parent materi. climate, topography, organisms

Question 9

what is the potential 6th factor for forming soils

Answer 9

human intervention

Question 10

how does climate impact soil formation

Answer 10

rates of physical and chemical weathering, leaching, deposition and precipitation of minerals

Question 11

how does parent mater. influence soil formation

Answer 11

residual soils develop in situ from bedrock but soil can be from transported mater. too. Specific physicochemical aspects of parent mater.

Question 12

how does topography impact soil formation

Answer 12

energy exchange and hydrological characteristics. Flatter usually = deeper

Question 13

how does organic matter impact soil formation

Answer 13

plants needed for accum. of organic matter, symbiotic relationships between lichens and fungi (primary colonisers) facilitate soil devel.

Question 14

how does biotic aspect influence soil formation

Answer 14

support of soil-based macroorganisms and microorganisms, mineralisation of organic matter to form humus

Question 15

name several ways that humans have disrupted soil

Answer 15

land use change, drainage pattern disruption, mechanical cultivation of topsoil breaks up peds, cropping patterns, application of irrigation, fertilisers and pesticides, salinisation, pollution

Question 16

3 stages of soil profile development

Answer 16

weathering of parent material, formation of soil particles and accumulation of organic matter, movement of mater. to different horizons

Question 17

O horizon

Answer 17

top horizon, organic matter

Question 18

A horizon

Answer 18

topsoil, lots of bio. activity, darker colour, most fertile usually,

Question 19

zone of eluviation

Answer 19

in podzols where the clay particles and nutrients are washed out of the A horizon

Question 20

B horizon

Answer 20

subsoil, thicker, high con. of clay, less water

Question 21

zone of illuviation

Answer 21

area of B zone in podzols where the clay particles are washed in

Question 22

C horizon

Answer 22

some parent mater. , transitional, partially weathered

Question 23

what phase forms the structural skeleton of mineral soils

Answer 23

solid phase= over 50% volume

Question 24

3 sizes of soil pores

Answer 24

micropores, mesopores, macropores

Question 25

5 types of soil particles in size order

Answer 25

``` stones/gravel coarse sand fine sand silt clay ```

Question 26

what is soil texture

Answer 26

the size range of particles in the soil qualitative= the feel quantitative= distribution of particle sizes ad mass of various size ranges

Question 27

how are soil types classified

Answer 27

proportion of sand, silt and clay

Question 28

what is the specific surface area of soil

Answer 28

total surface area of a soil per unit of mass-> can determine type and property of a material

Question 29

what is the cation exchange capacity

Answer 29

influences the retention and release of nutrients and salts within the soil solution high clay/organic matter= higher cation exchange capacity

Question 30

soil fertility

Answer 30

ability of soils to supply nutrients needed for plant growth

Question 31

how many elements are essential to plant growth

Answer 31

17

Question 32

how can changing water dynamics change soil processes and composition

Answer 32

swelling or shrinking, porosity, density, pore-size distribution

Question 33

which pore types allow the use of water by plants

Answer 33

macropores (rapid movement) and mesopores-> hold water against force of gravity which is key for plants

Question 34

cycle of carbon through soils

Answer 34

plants via photosynthesis, leaf litter, through roots, release of gas and dissolved carbon through respiration

Question 35

what percen. of terrestrial carbon stores is in soils

Answer 35

80%

Question 36

key cause of soil organic carbon loss?

Answer 36

land use and change

Question 37

aim of the 4 pour 1000 initiative

Answer 37

increase soil carbon storage by 4 parts per 1000, use soil carbon sequestration as a negative emission strategy

Question 38

4 key ecosystem services provided by soils

Answer 38

food security, water quality and provision, climate regulation, biodiversity

Question 39

what does SOC stand for

Answer 39

soil organic carbon

Question 40

5 ways rocks are eroded chemically to form soils

Answer 40

hydrolysis, carbonation, hydration, dissolution, oxidation and reduction

Question 41

how does hydrolysis occur

Answer 41

most common form of chemical weathering: water dissociates into hydrogen and a hydroxyl ion which attack the bonds holding minerals together

Question 42

what kind of change do minerals undergo to become oxidised or reduced

Answer 42

chemical change through an electrostatic charge