Ecology 3

Ecology Lecture 3: 

Ecology Lecture 3 Ralph Kirby

What is soil: 

What is soil Before life invaded the land from the sea, there was probably little that looked like soil today Dust like Mars Little organic matter A few microorganisms perhaps However, soil is the basis of all terrestrial life and without soil, there would be no plants, no soil microorganism and no land animals Plants obtain many of their water and nutrients from soil and it provides an place to attach to.

Definition of soil: 

Definition of soil Soil is hard to define because it is so complex Soil is a natural product formed by the weathering of rocks and the action of living organism Does it include the ability to support life Soil is a collection of mineral and organic matter than can support plant growth Does this include soil like material that does not support life What if the climate at present does not support life The stratum below vegetation and above hard rock What if there is no vegetation

Slide4: 

Three dimensional matrix Soil is a living system made up of a matrix of minerals and organic matter that includes plants, both roots and stems Bacteria Fungi Protozoa Algae Small animals Larger animals A unit of soil large enough to define is called Pedon

Formation of soil: 

Formation of soil Proposed that five factors are involved in the formation of soil Parent Material Igneous rock Sedimentary rock Metamorphic rock Climate Temperature Rainfall Elevation Latitude Biotic Factors Input factors from living organisms Degradation by living organisms Topography Water runoff Draining Erosion Time Weathering, accumulation, decomposition and mineralization take time Initial differentiation can be within 30 years Formation of true soil, 2000 to 20000 years Soil can age

Slide6: 

Mechanical and Chemical Weathering Starting Point Mechanical Water Wind Temperature Creates loose material Sorted and moved Chemical Acids produced by lichens and mosses Addition of organic matter Oxidization etc

Living Organisms: 

Living Organisms Without living organism there would be no soil Mars does not have soil as we know it When plants colonized the land, they changed it by producing soil Plants introduce organic matter to soil Microorganisms and small animals recycle the organic matter to humus Humus can be on top of soil in some acidic environments Humus is usually mixed with the soil and changes it composition Many microorganisms have evolved to fill this niche Actinomycetales Lignin degrading fungi

Soil has many layers: 

Soil has many layers O Organic layer Fluctuates with season A Upper layer of mineralized soil Large amount of organic matter E Eluvial zone Maximum leaching B Illuvial zone Accumates leached material such as clays, silicates, etc C Unweathered starting material R Rock or parent material

Soils show a great deal of variation: 

Soils show a great deal of variation Color No direct effect on how soil function Allows classification Red Possibly oxides Black Possible high organic content Texture Variation in size and shape of soil particles Gravel >2mm Sand 0.05mm to 2mm Silt 0.002mm to 0.05mm Clay <0.002mm

Slide10: 

Structure Space for roots etc Pore space Amount of water held Rate of water movement Aeration Compaction Aggregation Aggegates or peds Depth Depends on Slope Weathering Parent material Vegetation Grasslands are deep Forests are shallow

Water is essential for soils: 

Water is essential for soils See lack (?) of water on Mars Soil can become saturated if all pores filled Normally at field capacity Capillary water is usually present Extracted by plants Available water capacity Hygroscopic water unavailable Drainage Low drainage results in low aeration All affected by soil texture Sand Lower capacity Clays Higher capacity

Plants need minerals in the form of ions: 

Plants need minerals in the form of ions Cationic exchange resin type structure Change in pH affects binding capacity for ions Immovable Hydrogen Aluminium Removable in order Calcium Magnesium Potassium Ammonium Sodium

Soils vary with climate and vegetation: 

Soils vary with climate and vegetation

Slide16: 

Entrisol Mountains Where soil making process has been interupted by flooding etc Inceptisol Mineral rich mountain soil Forests and pasture Aridisol Arid regions Low in humus Salinization due to low rainfall Andisol Volcanic in origin Can be very fertile Mollisol Dark organic rich A layer Deep fertile Spodosol Acidic Coniferous forest soil Alfisol Temperate forest Organically rich Ultisol Warm climate soil Redish or yellowish Low nutriant content Oxisol Wet subtropical/tropical soil\ Lots of water movement through soil Low nutrients Histosol High water table Poor drainage Peatlands Gelisol Permafrost Vertisol High % clay No B horizon Swell and shrink Pasture

Soil forms a biotic ecosystem on its own: 

Soil forms a biotic ecosystem on its own

Biotic System in soil: 

Biotic System in soil Needs Living space Varies with soil type Oxygen Varies with water saturation Food Varies with plant cover Water Can vary with climate Environment is relatively constant Water can change dramatically Mechanisms to survive drought Spores etc Only upper layer is really available Diversity is very very large The ecosystem is largely not understood in detail Particularly the microorganisms

Man has an effect on soil: 

Man has an effect on soil Changes in plant cover England 1000 BC Forest 2004 Cities, towns, villages, farm land, monoculture forests Erosion Deforestation in Africa Climate change Dams Roads and storm drains