Biological Resources (A2); Forest Resources (Complete) Flashcards
What percentage of the Earth’s land area do forests cover?
30%
What are the features of forests?
-Often climax community in ecological succession
-Found wherever conditions are suitable
-Usually involve presence of soil & climate that doesn’t involve prolonged dry periods/serious lire’s
What determines the type of forest found?
Temperature
Why are forests important for human survival?
They provide ecological services & resources that we need
The importance of forests- resources; how can resources be gained from forests?
-Some are extracted from existing natural forests
-Most are produced by cultivated plantations of species that were discovered in forests
The importance of forests- resources; why could the loss of wild forests result in?
Loss of valuable species that become extinct before their importance is understood, or even before they’re been discovered
The importance of forests- resources; why is wood important and what kind can be extracted from different forests?
-Is strong, has a high strength: weight ratio, flexibility & requires little processing for use, is often readily available
-Mahogany & teak from tropical forests
-Oak & beech from temperature deciduous forests
-Conifer timber from northern coniferous forests
The importance of forests- resources; what are the general uses of wood?
-Structural uses; building construction, telegraph poles, shuttering for concrete structures
-Furniture
-Tools
The importance of forests- resources; what are the uses of fibres extracted from different forest elements?
-Most paper is made from flattened sheets of interwoven cellulose fibres from pulped wood
-Cotton is made from fibres that surround seeds of cotton bush
-Viscose (rayon) textiles are made by chemical treatment of cellulose fibres extracted from wood
The importance of forests- resources; how is fuel provided by forests and why is this important?
-Fuelwood; before industrial revolution, wood was the main energy resource for almost everyone in the world
-Even though oil,coal, gas now provide more energy than wood, it still provides energy for the greatest number of people, esp LICs
The importance of forests- resources; in what different ways can forests provide food?
-Trees provide fodder for live stock & fruit + nuts for human food
-Animals living in forests can provide human food like bushmeat in LEDCs
-Many forest species are crucial in agriculture, eg coffee, cacao, bananas, papayas, Brazil nuts. Pigs & chickens were originally forest animals
-Wild varieties of cultivated species contain genes for new characteristics that maybe important in future selective breeding programmes
-May be many more species in forests that could be cultivated/domesticated
The importance of forests- resources; how can forests contribute to new medicines?
-Trees produce many chemicals that have medicinal uses
-Some are still extracted from tree tissues while others were identified in trees but are now synthesised artificially, eg quinine that was originally extracted from the Cinchona tree
-Most forest species haven’t yet been researched for medicinal compounds they may contain
The importance of forests- ecosystem services; how do forests contribute to atmospheric regulation?
-Balance of photosynthesis & respiration in forests is important in regulating atmospheric levels of carbon dioxide & oxygen
-Act as huge reservoir of carbon, mainly in carbohydrate cellulose; main component in wood. If it weren’t stored in wood, most would be in the atmosphere as CO². Cellulose is hard to digest so wood is a carbon reservoir w/ relatively long residence time compared w/ carbon in other living material
-Carbon sequestration to counteract global climate change by planting more trees. Photosynthesis also releases O²; essential for aerobic organisms & maintenance of ozone layer
The importance of forests- ecosystem services; why is the total mass of carbon in forests/forest soils significant?
-Total mass of carbon in forest soils is greater than in vegetation, especially in boreal forests
-Total mass of carbon in forests is roughly x2 mass in atmosphere
The importance of forests- ecosystem services; how do forests aid with the regulation of the hydrological cycle?
-Transpiration rates from forests are greater than from any other terrestrial ecosystem & is important in increasing precipitation rate downwind
-Interception by foliage of forests also increases evaporation rates but decreases infiltration
-Help soil formation & reduce soil erosion so soil depth may be greater than for other ecosystems. Soil will retain water after it has rained & moderate flow of water into rivers
The importance of forests- ecosystem services; how do forests absorb sun,ight and why is this important?
-Low albedo of forests increases absorption of sunlight & storage of heat in water in wood
-Forests absorb sunlight during day; much of this is connected to heat which is radiated at night → reduces extremes of temp between day & night
The importance of forests- ecosystem services; how do forests influence light absorption and what does this result in?
-Canopy vegetation absorbs a lot of solar insulation, esp red & blue wavelengths that are absorbed by chlorophyll
-Plants living below canopy have access to less light & much of this is green light not effectively absorbed by chlorophyll. So, these plants often have special adaptations like denser chlorophyll, additional pigments or growth periods when trees have lost their leaves
The importance of forests- ecosystem services; how do forests influence wind velocity and what does this result in?
Lower wind velocity produced by shelter of trees means plants below canopy layer use animals to help w/ pollination & seed dispersal rather than wind
The importance of forests- ecosystem services; how does the humidity in forests influence animals?
High humidity levels = animals like amphibians can survive more easily as skin doesn’t dry out
The importance of forests- ecosystem services; what are the reasons for forests being good habitat/wildlife refuges?
-Most diverse terrestrial ecosystems
-Each species of tree supports its own unique community of species so forests w/ greater variety of tree species are likely to have greater overall biodiversity
-Create v diverse habitats w/ large variety of possible ecological niches; increased by stratification within forest which is most obvious in forests w/ highest primary productivity
-Trees create variations in abiotic factors like light levels/wavelengths, humidity, temp, wind velocity
The importance of forests- ecosystem services; what does the high primary productivity of forests provide and why is this limited?
-A lot of energy to support higher trophic levels in food chain
-Energy isn’t always available to other organisms quickly, as much is stored in wood; released when tree dies & decomposes
The importance of forests- ecosystem services; in what different ways do forests aid soil conservation?
-Dead vegetation contributes humus & nutrients to soil & food energy for detritivores + decomposes that are involved in soil formation
-Trees help to prevent soil being washed/blown away by intercepting rainfall & reducing wind velocity
-Living trees & leaf litter on soil surface help reduce wind velocity & impact of rain drops
-Tree roots help hold soil together → reduces erosion by water running over surface
-Humus from decomposed vegetation binds soil together
-Forest soil w/ lots of organic matter will have lots of living organisms incl worms → increases ease w/ which water infiltrates into soil; reduces runoff & so amount of soil washed away
The importance of forests- ecosystem services; how are forests important for recreation/amenity uses?
-Important for recreational uses like walking, orienteering, cycling & camping
-Also important for educational activities
Forest exploitation & management; what did traditional forest management include?
-In pre-industrial societies, forests produced wood from wide variety of diff species, each having its own particular uses
-Traditional techniques involved management of existing woodland areas to maximise yields of forest products → rarely involved total removal of natural forest & often retained mixed-species forests w/ trees of diff ages
Forest exploitation & management; what are the uses of different tree species?
-Oak; timber-framed buildings, ship buildings
-Beech; furniture, tool handles
-Ash; furniture, roof timbers
-Holly; mathematical instruments, walking sticks
-Hazel; fencing panels, interwoven wall panels
Forest exploitation & management; what are standard trees?
Trees grown to maturity for production of large timbers for uses like construction of buildings & ships
Forest exploitation & management; what does coppicing involve?
-Cutting trees to ground level on cycle of 1-20 years depending on use of wood
-Branches that regrow were used for baskets, fencing, charcoal, wall panels & roof
Forest exploitation & management; what is pollarding?
Similar to coppicing but trees are cut above ground level so regrowing branches can’t be eaten by livestock
Forest exploitation & management; how does the demand and uses of timber change as a society develops?
-Demand for wood fuel may decline as people switch to fossil fuels/electricity
-Species-specific uses of wood from traditionally managed woodland are often replaced by large-scale uses like chipped wood for sheet construction material & plywood for concrete shuttering
-Harvesting methods changed from selective logging/cutting of small areas to large-scale clear-felling; reduces wildlife biodiversity of forest
-Existing natural woodland may be replaced w/ plantations of selected species
Forest exploitation & management- methods; why are non-indigenous species cultivated?
-Tree species selected for cultivation are often non-indigenous; may be better adapted to environmental conditions & are less likely to suffer damage due to pests/disease
-Growing non-indigenous species is less likely to support indigenous wildlife species as their inter-species needs for food, pollination, seed dispersal, habitats are less likely to be met
Forest exploitation & management- methods; what are examples of non-indigenous forestry plantations in different places?
-UK; Sitka Spruce & Douglas Fir (originally from N America)
-Corsican Pine (originally from S Europe)
-Central America; Teak (originally from Asia)
-E Africa; Eucalyptus (originally from Australia)
Forest exploitation & management- methods; what are the advantages of single-species plantations?
-Growing monoculture of one tree species can make management of plantation easier
-Activities like planting, thinning & felling can be carried out over large areas at same time
Forest exploitation & management- methods; why is close planting of trees used in forests and why can this be disadvantageous?
-Planting all seedlings close together makes trees compete w/ each other for light so grow tall & straight
-Low light levels at ground level inhibit growth of other plants that may compete w/ trees for water/nutrients
-Loss of these plants & species depending upon them reduces wildlife diversity of forest
Forest exploitation & management- methods; why is a simple age structure in forests used and why is this also disadvantageous?
-Planting large areas of trees at same time makes tree management easy
-Trees will all be similar sizes & need similar management activities at same time
-But, having trees of similar sizes reduces variety of abiotic factors compared w/ having plantation w/ trees of diff ages & sizes + reduces diversity of wildlife species that can survive
-Trees in commercial plantations are usually felled when income will be greatest; normally when they’re approaching full size a growth rate starting to ↓. This is v diff from natural forest; contain old trees w/ dead wood that supports many invertebrates & species feeding on them, like woodpeckers
Deforestation; how much of the world’s original forest area has been lost to human activities?
1/3
Deforestation; what are the two main causes?
-Deliberate removing of forests to make space for another land use, eg agriculture & urban development
-Unsustainable exploitation; above Maximum Sustainable Yield
Deforestation; how does agricultural expansion cause the loss of forests?
-Growth of local population increases demand for food, so more land must be cleared for farming
-Forest clearance for commercial cash crop agriculture where produce may be taken to cities/exported
Deforestation; what are examples of deforestation for agricultural expansion?
-Rainforest clearance in s America to grow sugar cane & soya beans/ranch cattle
-Rainforest clearance in SE Asia to grow palm oil
Deforestation; how can forest loss due to mineral extraction be impactful?
Forest clearance for mining & associated infrastructure affects relatively small total area but can have important local impacts
Deforestation; how can reservoirs cause forest loss + example?
-Reservoirs for public supply, irrigation, hydroelectric power (HEP) can replace forests
-Expansion of HEP in S America has caused loss of large areas of tropical rainforest
Deforestation; how can urbanisation cause forest loss?
-Expansion of urban areas con cause direct loss of forest
-Also increases demand for fuel & food which can cause further forest loss
Deforestation; what are the impacts of deforestation for transport infrastructure?
Area of forest lost by construction of roads, railways, airports isn’t large but can have other impacts;
-Roads + railways can create barriers to movement of wildlife & cause population fragmentation
-Improved transport systems increase accessibility & make it easier to take out resources like felled trees/agricultural produce that may increase rate of forest clearance
Deforestation- unsustainable exploitation; why may timber resources be exploited sustainably/unsustainably?
-Softwood made by conifers like pine & spruce is often made sustainably w/ replanting to replace harvested areas, eg in Scandinavia & Canada
-Hardwood species like teak & mahogany grow more slowly than conifers so it’s harder to commercially manage hardwood plantation as may take longer to make a saleable crop
-So, a lot of harvested hardwood come from mixed forests that are clear felled & may not be replanted
Deforestation- unsustainable exploitation; why is wood highly demanded as a fuel?
-Many people rely on wood as their domestic energy source than any other fuel
-It’s not necessarily fuel choice but many in LEDCs can’t afford alternative energy sources & have to use wood, even though its exploitation may be unsustainable
Deforestation- unsustainable exploitation; why is charcoal used as a fuel and why is this unsustainable?
-In towns & cities, there may be greater demand for charcoal which produces less smoke when burnt
-Production of charcoal involves partial combustion of wood w/ shortage of air
-Much of the energy value of wood is lost in this process which increases rate of forest clearance to satisfy demand for energy
Deforestation- unsustainable exploitation; why are forests cleared for livestock fodder and why is this unsustainable?
-It’s unusual for forest areas to be cleared to provide livestock food
-But, in LEDCs, in areas of mixed woodland & grassland, farmers may cut branches off trees if there’s a shortage of ground-level grazing
-If this exceeds growth of trees, then forest may gradually be degraded & disappear
Deforestation- effects; how does deforestation cause the loss of forest resources?
-Forest products are renewable but can be depleted; deforestation stops their production completely
-Timber, fuels, fibres, medicines
Deforestation- effects; what ecological impacts does deforestation cause?
-Reduced biodiversity
-Loss of species
-Fragmentation of remaining forest areas
Deforestation- effects; how does deforestation cause changes to hydrology?
-Reduced interception & transpiration
-Increased runoff
Deforestation- effects; in what ways does deforestation impact soils?
-Reduced soil formation
-Less dead organic matter
-Increased soil erosion
-Less protection of soil by vegetation & leaf litter
-Reduced soil organic matter
-Reduced root binding
Deforestation- effects; what are the climate impacts that deforestation causes?
-Increased albedo
-Reduced carbon sequestration & carbon reservoir
-Reduced rainfall downwind
Sustainable forest management; how can forests be exploited sustainably and what could this involve?
-If harvesting rates & environmental impacts are carefully managed
-May involve combo of environmentally beneficial methods used in traditional forest management w/ commercially productive methods of modern plantation forestry
Sustainable forest management; which countries have had large-scale tree planting projects?
China, Cuba & Bhutan
Features of sustainability managed forests; what should harvesting rates be like?
Rate of resource removal must be no greater than the Maximum Sustainable Yield
Features of sustainability managed forests; why are mixed species plantations important?
Wildlife biodiversity is increased by growing multiple species as there’s an increase in food choices, inter-species relationships & niches
Features of sustainability managed forests; why are indigenous species important?
If they’re cultivated, it’s more likely other indigenous species will benefit eg birds & insects
Features of sustainability managed forests; why is a mixed age structure of trees important?
-Having a plantation w/ trees of diff ages produces greater diversity of abiotic factors like light levels, temp, wind velocity
-This increases biodiversity of other species living in the forest
Features of sustainability managed forests; when is clear-felling vs selective logging done and why?
-Clear-felling a large area at one time is easy. It can be commercially advantageous if trees have been grown as single species monoculture as all trees may be ready for harvesting at same time
-In mixed-species plantations/natural forests, diff trees will be ready for felling at diff times; selective logging
Features of sustainability managed forests; what are the advantages and disadvantages of selective logging?
-More costly as it’s more labour-intensive
-But, it gains max benefit from forest timber resource over longer time periods
-It’s also good for wildlife as removal of individual trees leaves smaller clearings w/ smaller impact on survival of remaining wildlife populations
-Wildlife that’s lost its tree habitat won’t have to move too far to find a new habitat
