Higher Geography Paper one Physical and Human environment Biosphere Model answers

Higher Geography Paper one Physical and Human environment Biosphere Model answers

Soil profile model answer Podzol Select one of the following soil types: 1. Podzol 2. Brown Earth 3. Gley With the aid of an annotated diagram of a soil profile, explain how the major soil forming factors have contributed to its formation. Past papers 91, 93, 95, 98, 99, 02, 04, 06, 07, 09 Climate Podzols are found in a belt of the Northern Hemisphere associated with coniferous forests. Cold, cool climates lead to a lack of soil biota and slow decomposition of leaf-litter. Spring snow-melt and precipitation, although low, exceeds evapotranspiration. Coniferous forests create small amounts of pine cone and needle litter. Thin, acidic humus (mor) develops from needle litter. Natural vegetation Precipitation and snow melt leads to a rapid leaching of iron and aluminium oxides (eluviation) from the A horizon which leaves it rich in silica and ash-grey in colour. The decomposition of iron oxides into the B horizon (illuviation) which then creates a red-brown colouring which may concentrate to form a thin solid layer called an iron pan. This can impede drainage and can cause water logging in the topsoil. Soil Biota Clearly defined horizons are created, by limited soil biota and slow activity due to the cold climate which restricts soil mixing. Parent materialweathering of parent material contributes only slightly to soil forming processes.

Soil profile model answer Brown Earth Select one of the following soil types: 1. Podzol 2. Brown Earth 3. Gley With the aid of an annotated diagram of a soil profile, explain how the major soil forming factors have contributed to its formation. Past papers 91, 93, 95, 98, 99, 02, 04, 06, 09 Climate Brown Earths are found in the areas to the south of Podzols, in deciduous forest. Although precipitation levels and spring snowmelt are less than podzol areas, precipitation still exceeds evaporation (pedalfer). Due to the warm/cool climate it encourages abundant soil biota and activity. Natural Vegetation Deciduous forests provide plentiful supplies of broad leafed litter. The resulting humus is very deep and only slightly acidic (mull). The annual leaf fall returns bases to the soil. Relief and Drainage The A horizons texture may be quite greasy due to the high organic content. The light brown colour as humus replaces leaching minerals. Leaching is a significant process, but is moderate compared to Podzols. The iron pan may develop where leaching is more active and iron and aluminium oxides are deposited in the B horizon. The B horizon deepens when developing. Soil Biota More of the biota results in rapid decomposition of leaf-litter. This then leads to the less distinctive soil horizons due to the mixing and aeration by biota. Parent Material The weathering of the parent material contributes to the soil forming process.

Soil profile model answer Gley Select one of the following soil types: 1. Podzol 2. Brown Earth 3. Gley With the aid of an annotated diagram of a soil profile, explain how the major soil forming factors have contributed to its formation. Past papers 91, 93, 95, 98, 99, 02, 04, 07 Climate The brief, mild summers and severe winter temperatures restrict the soil biota activity. With the continual seasonal freezing and thawing with consequent expansion and contraction leads to vertical mixing of the soil particles and poorly defined horizons. The permafrost impedes drainage. Natural Vegetation There is limited variety of tough grasses ad ground hugging plants (e.g. mosses and lichens) due to cold climate. This then produces dark, acidic humus (mor). Relief and Drainage Poor drainage is the key soil forming factor. The damp, waterlogging soils is due to the poor drainage from permafrost layer a short distance below the surface. The waterlogging removes the oxygen from the soil which creates anaerobic (absence of free oxygen) conditions. This then leads to gleying, as the iron compounds turn blue-grey in colour. The texture is greasy to touch. Soil Biota The soil biota activity is restricted due to waterlogging and climatic factors. Little soil mixing and slow rates of humus decomposition result.

Parent Material Weathered fragments of parent material are pushed up by freeze thaw into blue-grey and peaty clays of B horizon.

Climax vegetation Model answer. Explain fully what is meant by the term climax vegetation? Past papers 92, 94, 97, 99, 05, 11 ü Pioneer plants (mosses, lichens) colonize bare ground e.g. sand dune, mudflats, derelict sites ü The pioneers weather the surface, retain water in their roots and bind the soil. This gradually alters the area s environmental conditions. ü Pioneers die and decay to form a richer, deeper soil suitable for more complex plant species to colonize. ü Succession begins when environmental conditions begin to favour certain plant species. These species can compete more effectively for available nutrients, light, space and water. They shade out the ground from sunlight, thus succeeding (replacing) the pioneers which are now less well equipped to compete and survive. ü When the ecosystem becomes stable and relatively unchanging the climax stage is reached. This is the final stage of succession and the plant community is in a state of dynamic equilibrium (i.e. continuous small changes occur but overall stability is maintained.) ü The climax vegetation is the most complex group of plants in an area and develops over a long period of time.

Sand dunes model answer Describe and explain the changes in vegetation along a coastal sand dune Past papers 92, 94, 96, 98, 00, 01, 03, 05, 08, 10, 11 Strandline/embryo dune ü Sea Twitch/ Sea Rocket dominant species close to water s edge as they can withstand the o Desiccating (drying) effect of on-shore winds. o High salinity o Lack of humus o High alkalinity levels (from calcium carbonate in shell fragments) o ü Some species e.g. sea couch grass can withstand short periods of immersion in salt water. ü These early colonisers help stabilise the embryo dune and decay to provide humus for the next stage. Fore Dune ü Salinity decreases with increasing distance from the sea. ü Humus content increases slightly from colonisers. ü Soil acidity increases slightly due to less calcium carbonate. ü Plants e.g. Sea Holly continue to stabilise the dune, allowing the key establishment of marram grass. ü Marram grass succeeds Couch grass. It thrives on fresh supplies of sand and its long roots stabilise the dune further and help the dune build up.

Yellow Dune/Main Dune ü Alkalinity decreasing further and fresh water increasing both due to increasing humus content from decay of vegetation on the fore dune. ü Salinity continuing to decrease with increasing distance from sea. ü As a result, marram grass now thriving together with wider variety of plants e.g. Ragwort, Sea Bindweed. Semi-fixed Dune ü Once yellow dune over 10m high, less sand builds up behind it. Marram grass dies out and forms thin humus layer. ü Other plants able to grow here e.g. Dandelions. Dune Slacks ü Behind dunes, water collects in damp, sheltered hollows called dune slacks. ü The water table is near the surface which encourages the establishment of cotton grass, reeds, creeping willow. Grey dune/fixed dune ü Damper soils with higher humus content ü More acidic due to leaching of carbonates by rain ü Shelter increases, so sand and salinity decreases ü Wider variety of plants develop e.g. healthier, grasses, lichens Climax vegetation ü Grassland develops on alkaline soils, heathland on more acidic soils ü High humus and water content allows these plants to succeed previous vegetation. ü Eventually, tree species e.g. oak, spruce are establish to give the climax vegetation.