Agriculture and Forestry
Which country has the highest ratio of suspicious timber supply
Indonesia
Biome
Terrestrial region with characteristic types of natural, undisturbed plant communities adapted to the climate of the area.
Why do different places have different forms of forestry and agriculture?
a) Differences of climate (eg. rainfall quantity and variability) b) Differences in land attributes (eg. soil type, altitude) c) Socio economic factors that affect which crops farmers choose to grow
The primary controls on the speed of flow in a river are:
slope, hydraulic radius and bed roughness
Salinity
- Australia is an old continent, where many parts used to be submerged under oceans. Therefore many soils are saline. - Dryland salinity- Removing deep rooted trees allows the water table to move towards the surface, bringing salt with it. This is because evapotranspiration is reduced, allowing more water to enter the system. - Irrigation Salinity - Water table moves towards the surface because more water is being applied by irrigation. Remedies - In WA, it is estimated a third of the landscape will need to be replanted. - Revegetation on slopes to keep the water table down. - Difficult issue to solve... farmer affected is often not the person who can fix the issue.
Soil acidification
- Many Australian soils have been leached of their basic cations. - Use of nitrogen fertiliser, use of legumes, removal of crop products causes soil acidification. - Plants struggle to grow - ~29 million ha of agricultural land has been acidified. Remedies - Apply lime to neutralise acidity. - Appropriately use nitrogen fertilisers. - Use soil tests to determine how much fertilisers you should apply.
Soil erosion
- Reduced soil cover from land clearing can cause higher instances of erosion. - You loose the most fertile topsoil, degrading the land severely. - The steepness, length of slope, site characteristics and energy in rainfall are all factors that impact the severity/ type of soil erosion. Remedies - Contour banks - Minimum tillage and strip cropping. Leave crop stubble to reduce soil exposure and erosion. - Zero tillage. Allows farmers to make more money, because ploughing is avoided. New crops are sown between old crop stubble.
What percentage of incidental sunlight is used for photosynthesis?
0.023%
What percentage of the Earth's total land area is used for arable cropping?
10%
In Australia, how much soil is moved by water each year?
14 billion tonnes
How much rainforest and total forest area has Australia lost since 1788?
75% rainforest, 40% total forest
What is a pull factor?
A factor that draws or attracts people to another location
Which planetary boundaries have been exceeded?
Climate change, rate of biodiversity loss, nitrogen cycle
Shield volcano
Contains mafic lava, low viscosity and little gas, rounded domes with gentle slopes
Cultural energy
Cultural energy is the human energy expended to produce something. It includes human labour, and energy used in the production of fuel for machinery, production of chemicals, production of the machinery used to farm and transport the product etc. A measure of cultural energy is relevant to calculating the efficiency of agricultural outputs, and also of alternate energy sources such as biofuels, to ensure they produce more energy than is required in their production.
What are the major differences between agricultural land use in developed and developing countries?
Developing countries: Diets are predominantly plant-based diets, using the primary productions of agriculture, which makes these diets more efficient, and requires less land for food production. There is more subsistence and low-impact farming, although countries may rapidly undergo industrialization to begin high-impact farming. Developed countries: As populations of countries become wealthier and have increased disposable income, their consumption of animal products increases. Recalling the affluence factor of the I = f(PAT) equation, these dietary changes have an increased environmental impact. Food production is less efficient because a large proportion of the primary food production is fed to animals before being eaten by humans.
What characteristics of exotic pasture make them good weeds?
Easily propagated, persistent, extended growth period, wide adaptation to a range of climates and soils.
Which is the order for nitrogen-fixing methods responsible for the most nitrogen to the least?
Haber-Bosch process, legumes, lightning, volcanic activity Nitrogen is required by plants to make protein and was historically the most limiting nutrient in agricultural production. The earth's atmosphere is 70% nitrogen gas, but in its gaseous state this is inaccessible to plants and so must be fixed to ammonium in the soil, by lightning or volcanic activity by mainly by bacteria. Legumes are important for this because they have a symbiotic relationship with the bacteria rhizobium. The industrial Haber-Bosch process fixes nitrogen with hydrogen from natural gas using high temperature and pressure and has globally doubled the rate of nitrogen input into the terrestrial Nitrogen cycle.
Sead-tree cutting
Harvest nearly all the trees in one cutting, but leave a few to produce seeds, which are harvested later
Urbanisation in less developed countries is generally characterised by:
High rural to urban migration
Match the energy efficiency of farming practices: (output:input)
Hunting gathering 50:1 Village agriculture 17:1 Mechanised farming 2:1
Selective Cutting
Intermediate age or mature trees cut singly or in small groups Advantages Growth of young trees encouraged by decreased crowding Soil is protected from erosion Disadvantages Not profitable - investment in harvesting (construction of logging roads, identification of trees) is high for the amount of timber logged. High grading - all of the highest value timber is removed from a forest
Erosion
Movement of weathered material
Developing world animal production systems are characterised by:
Poor genetics; poor nutrition; animal diseases
Clear felling
Remove all trees in a single cutting Advantages: Trees may be cut in a strip or in a series of patches (allows regeneration) Huge areas may be felled Efficient and profitable Disadvantages: Loss of forest ecosystems Detrimental effects on indigenous people Decreased species diversity Changed hydrology - flooding, erosion and siltation Decreased organic carbon and nutrients in soil Increased weeds
Shelterwood cutting
Removes all mature trees over 2-3 year periods (10 years) Advantages: Leaves enough mature trees for seeding Allows best trees to be left to produce seeds Disadvantages: Not profitable - investment in harvesting (construction of logging roads, identification of trees) is high for the amount of timber logged.
Explain the limiting factor principle, with an example
The limiting factor principle states that too little or too much of any abiotic factor limits or prevents growth of a population, even if all other factors are near optimal. Abiotic factors include light, water, oxygen, heat and nutrients. Examples include: - fertile soils in desert regions which are not suitable for agriculture due to lack of water - water with high turbidity from suspended sediment that prevents aquatic plants and algae growing due to lack of sunlight - alpine areas where trees cannot grow due to lack of moisture or low temperatures - forests without undergrowth where the canopy is too dense for light to penetrate It should be noted that many biotic factors can also affect the growth of a population, such as population size.
What are the planetary boundaries and what is their significance?
The planetary boundaries are a concept which developed in response to human interference with the Earth's natural processes. They establish nine categories; climate change, rate of biodiversity loss, biogeochemistry divided into the nitrogen cycle and the phosphorus cycle, stratospheric ozone depletion, ocean acidification, global freshwater use, change in land use, atmospheric aerosol loading and chemical pollution. The planetary boundaries establish a safe operating space, in which the earth's process will continue as they have throughout the Holocene. The planet's biosphere subsystems often react in nonlinear, often abrupt ways, as they reach thresholds and so the planetary boundaries include a zone of uncertainty, within which the threshold is unknown. The interconnected slow and fast feedback between biosphere systems means that changes may not be felt immediately, and so means there is a risk of a false sense of security.
If the base level of a river drops, what will occur?
The river will degrade to achieve an equilibrium profile
What three cereals supply 50% of the energy requirement of the human population?
Wheat, rice and maize
Physical water scarcity
When there is too little water to meet all the demands upon it. Competing water uses include agricultural crops for export or local consumption, industry, urban water supply, environmental water.
Features of Australian Agriculture during the 1800-1850s
a) Focus on livestock (sheep for wool) b) Harsh Australian environments c) Private farming on small grants d) 'Tyranny of distance' (long distances to get goods to market)
Which factors influence forest systems?
a) Latitude (tropical, temperate, boreal forests - temperature influences plant growth) b) Rainfall (rainforest, deciduous - rain supports more biomass, plants keep leaves year-round) c) Topography (affects temperature and rainfall)
Fundamental processes which sustain an agricultural ecosystem are
a) Nutrient cycling b) Predator and prey interactions (eg. parasites and pest species) c) Competition
What is a push factor?
induces people to move out of their present location
In Darcy's Law to determine how much ground water discharge (Q = flow rate) you have available you don't need to know
the porosity of the rocks
