THE PHYSICAL ENVIRONMENT Prepared by: Azlinda Abdul Ghani

1. THE PHYSICAL ENVIRONMENT Prepared by: Azlinda Abdul Ghani

2. Seasonal Variation and day length • Equator = exactly 12 hours of daylight and night every day • Vernal equinox = solar radiation falls directly on the equator - Equatorial region is heated most intensely - Every place on earth receive the same twelve hours each, day and night

3. Summer solstice - day are longest in Northern Hemisphere - sun heats the surface most intensely -Southern Hemisphere experience winter • Winter solstice - Summer in Southern Hemisphere - Northern Hemisphere is enduring shorter days and colder temperature

4. LIGHT • Light has a major effect on almost all living organisms. • Visible light, that part of the electromagnetic spectrum between the wavelengths of 400 to 700 nm, is known as photosynthetically active radiation (PAR) • Short wavelengths longer than 280 and 380 nm are ultraviolet light • Wavelengths longer than 740 nm are infrared

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6. Plant cover intercepts light • The amount of light that does penetrate a stand of vegetation to reach the ground varies with both the quantity and position of the leaves • As you move down through the canopy, the number of leaves above you increase, so the amount of light decreases • To quantify the changes in light environment with increasing area of leaves, we need to define the area of leaves per unit ground area (m2 leaf area/m2 ground area). This measure is the leaf area index, or LAI for short • As you move from the top of the canopy to the ground in a forest stand, the cumulative leaf area and LAI increase

7. Light and organism movement • Phototropism: The directional growth of plants in response to light. • Phototaxis: The movement of an organism either towards or away from a source of light. • Photokinesis – Movement based on the intensity of light

8. Light varies with depth in aquatic environment • Amount of light entering water surface will reduced further by • Suspended particles • Absorb by water • Organism of deeper ocean (200-1000 m deep) • Typically silvery gray or deep black • Lack pigment • Large eyes • Distribution of light in terrestrial • Vertical gradient of light influenced by • Absorption • Reflection

9. Absorption and reflection of light.

10. Daily and seasonal patterns of light govern life’s activities • Human activity quickens with daylight • Human activity changes as evening begins • The period of the circadian rhythm, the number of hours from the beginning of activity one day to beginning of activity on the next, is its free-running cycle • The activities of plants and animals are geared to the changing seasonal rhythms of night and day

11. Critical daylength =the signal for the responses of day and night • Critical daylength varies among organisms, but it usually fall somewhere between 10 and 14 hours • Some organisms can be classified as day-neutral, they are not controlled by daylength, but by some other influence such as rain-fall or temperature • Short-day organisms are those whose reproductive or other seasonal activity is stimulated by daylengths shorter than their critical daylength • Long-day organisms are those whose seasonal responses, such as flowering and reproduction, are stimulated by daylengths longer than the critical daylength

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13. Soil is difficult to define. There are a lot of definition of soil: • Soil is a natural product formed and synthesized by the weathering of rocks and the action of living organism • Soil is a collection of natural bodies of earth, composed of mineral and organic matter and capable of supporting plant growth • Soil is not just an abiotic environment for plant. It is teeming with life – billion of minute and not so minute animals, bacteria, and fungi. This make soil a living organism

14. Foundation which all terrestrial life depends • Medium for plant growth • Habitat for animal life • Formation of soil • Begins with weathering of rocks and minerals • Weathering • Mechanical • From interaction of several forces • Exposed to combine action of water, wind, temp • Chemical • Water, oxygen, acids from activities of soil organisms • Continual addition of organic matter

15. Soil formation • Involves five interdependent factors 1. Parent material 2. Climate 3. Biotic factors 4. Topography 5. Time

16. Parent material • Unconsolidated mass from which solid form • It is derived from parent rock or from transported material • Types of parent material - igneous =formed by cooling of volcanic flow - sedimentary = formed by deposition of mineral particles (sediments) - metamorphic = either igneous or sedimentary rock that have been altered by heat and pressure

17. Wind, water, glaciers and gravity transport other parent materials. • Because of the diversity of the materials, transported soils are commonly more fertile than soil derived from in place parents material

18. Climate • Shape the development of the soil through temperature, precipitation • Influences the plant and animal life, which important in soil development Biotic factors • Plants, animals, bacteria and fungi, contribute to the formation of soil • Vegetation responsible to reduce erosion and influences the nutrient content

19. Topography • Contour of the land, influences both the intensity of radiant energy and the amount of water that enters the soil • More water runs of and less enters the soil on steep slopes than on level land Time • A crucial element in soil formation • All the formation process require time • Soil develop slowly in dry regions than in humid ones • Young soil are more fertile than old soil • Old soil experience a long time leaching without replacement by fresh material

20. Mechanical weathering • Rock break down into loose material • Loess = material transported by wind • Alluvial deposits = material transport by water • Till = material transport by glacial ice • Pat = soil material come form accumulated organic matter • Residual = material remaining • Regolith = mantle of unconsolidated material

21. Chemical weathering • The activities of soil organisms such as lichens mosses, the acid they produce and rain water break down the primary minerals • The chemical and physical processes in the parent material result in the development of layer in the soil

22. Living organisms influence soil development • Plants rooted in weathering break it down, extract nutrient from its depths and add all important organic material and nutrient to the surface • The decomposition of organic matter turns organic compounds into in organic nutrients • Soil organisms act on organic matter to produce humus • Humus is a dark – coloured organic material made up of many complex compounds • Humus affects soil structure and fertility

23. Soil profile

24. The O horizon is the surface layer formed or forming above the mineral layer. - It consists of fresh or partially decomposed organic material that has not been mixed into mineral soil. -This layer and the upper part of the next horizon, A, constitute the zone of maximum biological activity. -The O layer fluctuates seasonally. In temperate regions, it is thickest in the fall, when new leaf litter accumulates on the surface. It is thinnest in the summer after decomposition has taken place.

25. The A horizon is the upper layer of mineral soil with the high content of organic matter. • It is characterized by an accumulation of organic matter and by the loss of some clay, inorganic minerals, and soluble matter.

26. The B horizon is the zone of illuviation, a collector leached material. • It accumulates silicates, clay , iron, aluminum, and humus. It develops a characteristic physical structure involving blocky, columnar, or prismatic shapes. • When moist it tends to erupt suddenly if pressure is applied.

27. The C horizon contains weathered material, either like or unlike the material from which the soil is presumed to have developed. • Some active weathering takes place in this horizon, but it litter affected by soil formation.

28. Soil profile • Consist of 4 horizons • Organic layer (O) • Dominated by organic material • Consist of undecomposed or partially decomposed plant • Topsoil (A) • Largely mineral soil • Dark colour • Subsoil (B) • Accumulation of mineral particles • Unconsolidated material (C) • Derived from the original parent material from which soil is developed

29. Physical characteristics • Colour = the most useful characteristics for the identification of soil • In temperate regions, brownish-black and dark brown colour, generally indicated organics matter • Dark brown and blackish colours, especially in the lower horizons, indicate poor drainage • Dark soil are high in organic matter • The bright colours indicating good drainage and good aeration

30. Soil texture = proportion of different sized soil particles • Particles are classified on the basic of size into gravel, sand, silt and clay • Gravel = >2.0mm • Sand = 0.05 – 2.0mm • Silt = 0.002 – 0.05mm • Clay = <0.002mm • Plasticity - the ability to change shape when pressure is applied and retain the shape when pressure is removed • Cation exchange – the exchange of ions between soil particles and soil solution

31. Soil texture affects pore space in the soil, which plays a major role in the movement of air and water in the soil, penetration of roots • Particles make up 50 percent of the total volume of the soil; the other 50 is soil gases • The finer the texture, the smaller the pores, and the greater the availability of active surface for water adhesion and chemical activity • Soil particles are held together in cluster or shapes of various sized called aggregates or peds

32. The arrangement of these aggregates is called soil structure • They are many types of structure, including prismatic, columnar, blocky, platelike, granular • Structure is influenced by texture, plants growing in the soil, other organisms, and the soil’s chemical status.

33. Soil depth • Soil develop under forests are shallow, with an A horizon of about 15 cm and a B horizon of about 60 cm • On level ground at the bottom of slopes and on alluvial plains, soils tend to be deep • Soil on ridge tops and steep slopes tend to be shallow, with bedrock close to the surface. • The natural fertility and water-holding capacity of such soil are low

34. Feature of soil • Field capacity is generally expressed as the percentage of the weight or volume of soil occupied by water compared to the oven-dried weight of the soil at the standard temperature • The amount of water and soil holds at field capacity varies with the soil’s texture • Water held between soil particles by capillary forces is capillary water

35. As plants and evaporation extract capillary water, the amount of water decline and reaches a level which a plant can no longer withdraw water = wilting point • The amount of water retained by the soil between field capacity and wilting point (FC-WP) = available water capacity • AWC provide an estimate of the water available for uptake by plants • If the soil dries even further, the only moisture remaining adheres tightly to soil particles as a thin film known as hygroscopic water , which unavailable to plants

36. Drainage classes 1)Very excessively drained soils 2)Excessively drained soils = plants roots are restricted to the upper layer of the soil because of water deficiencies 3)Well-drained soils, = plant roots can grow to a depth of 90 cm without restriction due to excess water 4)Moderately well-drained soils, = plant roots can grow to a depth of 50 cm without restriction

37. 5)Somewhat poorly drained soils, = restrict the growth of plant roots beyond the depth of 36 cm 6)Poorly drained soils, which are wet most of the time and are usually characterized by alders, willows and sedges 7)Very poorly drained soils, which water stands on or near the surface most of the year

38. Cation exchange • An ion is a charged particle. Ions carrying a positive charge are cations • In soils ions are limited in their mobility (mostly cations) because they are closely held to particles of clay and humus • The most important features of clay minerals, this substitution results in net negative charges that must be balanced by positively charged cations • The edges and sides, negatively charged, act as highly charged anions • They attract cation, water molecules and organic substances

39. The total number of negatively charged exchange sites on clay and humus particles that attract positively charged cation is called the cation exchange capacity (CEC) • CEC represent the net negative charges possessed by the soil • The percentage of sites occupied by basic cations, primarily Ca2+, Mg2+, Na+ and K+, is called percent base saturation • Soils with a high CEC are potentially fertile • Soil high in both CEC and base saturation are fertile unless they are saline or contain toxic heavy metals

40. Soil supports diverse and abundant life • Without the presence and intense activity of living organisms, soil development could not proceed • Soil inhabitants from bacteria and fungi to earthworm convert inert mineral matter into a living system • Water in the pore spaces is essential • The majority of soil organisms are active only in water • Soil water is usually present as a thin film coating the surfaces of soil particles • This film contains, among other thing, bacteria, unicellular algae, protozoa, rotifers, and nematodes

41. When water fills pore spaces after heavy rains, conditions are disastrous for some soil inhabitants • If earthworm cannot evade flooding by digging deeper, they come to the surface, where they often die from ultraviolet radiation and desiccation or are eaten • Dominant among the soil organisms are bacteria, fungi, protozoans, and nematodes. Flagellated protozoans range from 100,000 to 1,000,000, amoebas from 50,000 to 500,000 and ciliated up to 1000 pergram of soil • The mites (Acarina) and springtails feed on fungi or search for prey in the dark interstices and pores of the organic and mineral mass

42. The mites, tiny eight-legged arthropods from 0.1 to 2.0 mm in size attack dead vegetation • Collembolae are the most widely distributed all insects, from 0.3 to 1.0 mm in size, consume decomposing plant material, • Earthworm ingest soil and fresh litter and egest both and improve the soil environment for other organisms

43. Milipedes feeds on the surface litter. They eat leaves • Snails and slugs process the widest range of enzymes to hydrolyze cellulose and other plant polysaccharides, even the highly indigestible lignin • Termites, wingless, social insects. The only larger soil inhabitants that can break down the cellulose of wood • Detrital-feeding organisms support predators. Small arthropods are the principal prey of spiders, beetles, pseudoscorpions, predaceous mites, and centipedes • Various predaceous fungi live on bacteria-feeders and algae-feeders

44. Soil erosion • Soils have been depleted by erosion in which topsoil loss exceeds formation • Deforestation, poor agricultural practices, urbanization, road building, and other disturbances expose the soil to the erosive forces of water and wind • Soil erosion destroys natural and agricultural ecosystem and fills rivers, lakes, reservoirs and navigation channels with silt • Wind erosion carries soil far from its source in clouds of dust and increases particulate air pollution • Soil erosion in all its forms impoverishes regions and nations, reduces food production, and causes extensive economic losses

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