Soil classification

1 Soil classification The sub-discipline of soil science which deals with the systematic categorization of soils based on distinguishing characteristics developed during soil genesis as well as criteria that dictate choices in land use and soil management. It is also true that Pakistan’s soil can be classified regionally, or according to where it is found in the county. From that perspective, there are also six soil types: 1. Indus basin soils: The soils found along the current course of the Indus River are due to alluvial deposits made by that river depositing sediments every spring. 2. Bongar Soils: These soils are found in the historic Indus plain and are the best soils for agriculture in the country. Usually they’re far from the present-day bed of the Indus River. 3. Khaddar Soils: Also found along Pakistan’s rivers is this soil. It formed when, every year during flood, a new layer of salty clay was deposited. 4. Indus Delta Soils: These soils cover the current Indus River delta. Most of this soil is very clayey and was developed under seasonal floodwaters. 5. Mountain Soils: These rocky soils mostly cover the highlands of northern and western areas of Pakistan. 6. Sandy Desert Soils: These soils are made by the deposition of sand, layer by layer, year after year, for thousands of years. They’re found in the arid and semi-arid areas of Pakistan. Soil The upper layer of the earth which is composed of different thin rock particles is helpful in the growth of vegetation and plants that is called soil. Basic Components of Soil Soil has three basic components. 1. Solid particles like salt, mineral and organic matter. 2. Air. 3. Water. Importance of Soil The kind of soil totally depends upon climate, location, vegetation and rock material. The agriculture of a country depends upon her soil’s structure and kinds. Soil is a gift of nature. Alluvium Those materials which are transported from one place to another by rivers and deposited at other places are called alluvium. Aeolian Soil Similarly wind also transports the material from one place to another which is deposited over the surface that is called Aeolian Soil. Classification of Soils The soil of Pakistan may be classified according to the regional basis. Indus basin Soils

2 The indus plain is made with the deposition of alluvium by the indus river its tributaries. For the last thousands of years rivers have been depositing the soil in the form of layers. These soils have more calcium carbonate and less organic matter. These soils are divided into three main categories. Bongar Soils Bongar soils cover a vast area of indus plain. The area includes most of the part of Punjab, Peshawar, Mardan, Bannu and Kachhi plain. A major part of the province of sindh is also comprised of these soils. Some of these soils are rich and irrigated give very good production. Usually these soils are far from the present rivers beds. Khaddar Soils Khaddar soils are also formed along the rivers. So every year new layer of salt clay is deposited. These soils have low content of organic matter and salt. Indus Delta Soils These soils cover the river Indus Delta. They extent from Hyderabad to the south coastal area. Most of the soils is clay and developed under floodwater. Rice is cultivated in the major part of these soils. Mountain Soils These soils mostly cover the highlands of northern and western areas of Pakistan. The soils of northern mountainous areas have high content of organic matters because the climate is moist. Whereas the soils of western mountainous areas have high content of calcium carbonate and low content of organic matter because the climate of these areas is arid and semi-arid. The soils of Pothwar plateau have high lime content. They are productive when plenty of water is available. Sandy Desert Soils The soils cover the western areas of Balochistan, Cholistan and the desert of Thar in Pakistan. They are formed by layers of sand particles. They have moderate quantity of calcium carbonate. They are made of disposition of sandy soil layer by layer Arid and semi-arid type of climate effect these soils. So the economic activities are very low in deserts. From a variety of sources: About 60% of Pakistan's total land area is classified as unusable for forestry or agriculture because it consists of deserts and mountains. Pakistan’s soils are mostly dry and have high concentrations of calcium carbonate and a low content of organic matter. The major soil groupings are Indus basin soils, mountain soils, and sandy desert soils. 74.3% of Pakistan’s soils are composed of these six types of soil: 1. 30.6% Mountain/Valley: Patchy soils that are a loamy-gravelly mix 2. 14.7% Rolling/hilly sandy soils 3. 11.4% Loamy-clayey soils 4. 6.6% Rock out-crop and loamy soils, very shallow 5. 5.8% Mainly loamy to partly gravelly soils

3 6. 5.2% Loamy soils Various factors are involved in soil formation: time, geology, relief, drainage, climate, vegetation and people. Time It takes about 1000 years for one centimetre of soil to form. In many parts of Britain we have had only 10,000 years since the last Ice Age stripped the original surface soils away. Geology Minerals from the parent material are added to the soil by physical and chemical weathering. Relief Different soils will form on different degrees of slope and aspect. Gravity and temperatures will affect the degree of slope movement and weathering. Drainage Whether water can or cannot move through the soil easily will affect the development of the soil profile. Climate How much water and air enter the soil - and their temperatures - will affect the organic life of the soil and evaporation rates on the surface. Vegetation The type and quantity of plant cover will affect the amount of organic material added to the soil (humus). People When people change the angle of a slope through construction, or change the vegetation cover and/or drainage in an area, the soil will also change. FACTORS OF SOIL FORMATION Soils are natural expressions of the environment in which they were formed. They are derived from an infinite variety of materials that have been subjected to a wide spectrum of climatic conditions. Soil development is influenced by the topography on which soils occur, the plant and animal life which they support and the amount of time which they have been exposed to these conditions. Soi1 scientists recognize five major factors that influence soil formation: 1) parent material, 2) climate, 3) living organisms (especially native vegetation), 4) topography and 5) time. The combined influence of these soil-forming factors determines the properties of a soil and their degree of expression (fig. 2). Time Time is required for horizon formation. The longer a soil surface has been exposed to soil forming agents like rain and growing plants, the greater the development of the soil profile. Soils in recent alluvial or windblown materials or soils on steep slopes where erosion has been active may show very little horizon development.

4 Soils on older, stable surfaces generally have well defined horizons because the rate of soil formation has exceeded the rate of geologic erosion or deposition. As soils age, many original minerals are destroyed and many new ones are formed. Soils become more leached, more acid, and more clayey. In many well drained soils, the B horizons tend to become redder with time. Living organisms Plants affect soil development by supplying upper layers with organic matter, recycling nutrients from lower to upper layers, and helping to prevent erosion. In general, deep rooted plants contribute more to soil development than shallow rooted plants because the passages they create allow greater water movement, which in turn aids in leaching. Leaves, twigs, and bark from large plants fall onto the soil and are broken down by fungi, bacteria, insects, earthworms, and burrowing animals. These organisms eat and break down organic matter releasing plant nutrients. Some change certain elements, such as sulfur and nitrogen, into usable forms for plants. Microscopic organisms and the humus they produce act as a kind of glue to hold soil particles together in aggregates. Well-aggregated soil is ideal for providing the right combination of air and water to plant roots. Animals living in the soil affect decomposition of waste materials and how soil materials will be moved around in the soil profile. Climate Climate is a major factor in determining the kind of plant and animal life on and in the soil. It determines the amount of water available for weathering minerals, transporting the minerals and releasing elements. Climate, through its influence on soil temperature, determines the rate of chemical weathering. Warm, moist climates encourage rapid plant growth and thus high organic matter production. The opposite is true for cold, dry climates. Organic matter decomposition is also accelerated in warm, moist climates. Under the control of climate freezing, thawing, wetting, and drying break parent material apart. Rainfall causes leaching. Rain dissolves some minerals, such as carbonates, and transports them deeper into the soil. Some acid soils have developed from parent materials that originally contained limestone. Rainfall can also be acid, especially downwind from industrial processes. Parent Material Parent material refers to organic (such as fresh peat) and mineral material in which soil formation begins. Mineral material includes partially weathered rock, ash from volcanos, sediments moved and deposited by wind and water, or ground up rock deposited by glaciers. The material has a strong effect on the type of soil developed as well as the rate at which development takes place. Soil development may take place quicker in materials that are more permeable to water. Dense, massive, clayey materials can be resistant to soil formation processes.

5 Bedrock such as limestone, sandstone, shale, granite, gneiss and schist, slate, marble and many others break down into residuum (residue) through the weathering process. It is this residuum that becomes the parent material of soil and imparts some of the parent characteristics into the resulting soil profile. Soil material and rock fragments may fall, roll or slide downslope under the influence of gravity and water. This incoherent mass of material that generally accumulates on the lower portion of slopes and in depressions is called colluvium. Rock fragments in colluvium generally are angular in contrast to the rounded waterworn cobbles and stones found in alluvium and glacial outwash. Streams and rivers commonly overflow their banks and deposit fresh materials on the floodplains. These fresh or recent deposits, commonly topsoil, comprise the parent materials for the soils developed on these floodplains. Since there is new material added almost annually, the soils never have time to form well-developed horizons. Therefore, these young soils have poorly developed profiles, and most of their character is inherited from the parent material. This type of parent material exceeds 0.5 m (20 in.) in depth, and it is referred to on the scorecard as recent alluvium. Soils located on stream terrace positions that contain water worn coarse fragments have parent materials referred to as old alluvium. These soils were originally deposited by water and commonly have had time to form well-developed horizons. They never or rarely flood, and thus are not influenced by deposition of fresh materials. In the Mid-Atlantic region, large areas are underlain by the complex series of water-deposited sediments left by previous geologic events. These older sediments comprise the Coastal Plain along the Atlantic seaboard. In Maryland, these materials occupy half of the land area, and they comprise nearly all the parent material for Delaware soils and large segments of New Jersey. These Coastal Plain sediments, although much older than the recent alluvium along streams, have not been cemented and consolidated into bedrock--thus, the name unconsolidated sediments. Often these sediments have been capped or coated with a thin (several cm to several m) veneer or sheet of material consisting mainly of silt (loess). The wind may have carried this material from the glacial outwash areas before the rise in sea level that formed the Chesapeake Bay. The Coastal Plain soils are formed in these sediments and silt-cap parent materials. Therefore, soils occurring on the upland portions of the Coastal Plain are considered to have Coastal Plain sediments as their parent materials on the scorecard. Recent alluvium can and does occur on the Coastal Plain in the same landscape positions (along streams and rivers) as in other sections of the state. Landscape position Landscape position causes localized changes in moisture and temperature. When rain falls on a landscape, water begins to move downward by the force of gravity, either through the soil or across the surface to a lower elevation. Even though the landscape has the same soil-forming factors of climate, organisms, parent material, and time, drier soils at higher elevations may be quite different from the wetter soils where water accumulates. Wetter areas may have reducing conditions that will inhibit proper root growth for plants that require a balance of soil oxygen, water, and nutrients. Steepness, shape, and length of slope are important because they influence the rate at which water flows into or off the soil. If unprotected, soils on slopes may erode leaving a thinner surface layer. Eroded soils tend to be less fertile and have less available water than uneroded soils of the same series.

6 Aspect affects soil temperature. Generally, for most of the continental United States, soils on northfacing slopes tend to be cooler and wetter than soils on south-facing slopes. Soils on north-facing slopes tend to have thicker A and B horizons and tend to be less droughty. Position Position generally refers to the point on the landscape where the soil is located. Most soil series have a rather limited range of position and land form. In figure 3, the landscape is divided into (1) upland, (2) upland depression, (3) terrace, and (4) floodplain. Most soils can be classified into one of these landscape positions by observing the general surroundings in respect to streams or natural drainage systems. The floodplains refer to areas near streams that flood periodically. These soils may be quite productive, but they have a flooding hazard that seriously limits their use for urban development or agriculture. Terrace refers to soils developed in older alluvial materials above the zone of current flooding. Upland depressions or waterways refer to soils developed on concave land forms or at the heads of drainage ways and along waterways where surface drainage is retarded. Water tends to pond in these depressions, and the soils commonly have a darker and thicker surface horizon because of organic matter accumulations. Areas unaffected by stream activity in recent geologic time, and ordinarily lying at higher elevations (than alluvial plains) on rolling and convex positions, are designated upland.

1. Factors in Soil Formation 2. Soil is defined as that part of the unconsolidated material covering the surface of the earth which supports plant growth. It has three major constituents: solid particles (salts, minerals and organic matter), air and water. The type of soil formed is a function of topography, climate, vegetation, and the parent rocks from which the soil material is derived. Soil material transported and deposited by running water is termed alluvium, while that transported and deposited by winds forms aeolian soil. Soils formed in situ are termed residual. Soil texture varies with the size of the soil particles. Coarse textured soils are sandy, fine textured soils are clayey, and a mixture of sand and clay is called loam. The organic content of the soil also varies, being largely dependent of the extent and type of the vegetative cover. Soils of high organic content are darker in colour, and have more nutrients for plant growth than those of low organic content. Since most of Pakistan is arid or semi-arid, the soils contain little organic matter. Soil-forming processes are complex and continuous. As a result, soils vary in their chemical composition, colour, texture, and organic content from place to place, even within small areas. The ensuing discussion describes only the major soil-groupings of Pakistan. Soils of Pakistan Indus Basin Soils

7 The Indus Basin comprises a vast area of alluvial plains deposited by the Indus and its tributaries, and a small area of loess plains. Most of the material is sub-recent or recent in origin, calcareous, and low in organic content. The soils can be divided into three major categories: Bangar Soils (old alluvium); Khaddar Soils (new alluvium); and Indus Delta Soils. Bangar Soils cover a vast area in the Indus Plain, including most of the Punjab, Pewahwar, Mardan, Bannu and Kachhi plains, and the greater part of the Sind Plain. These soils are deep, calcareous, of medium to fine texture, low in organic matter, but very productive when irrigated and fertilized. In some ill-drained areas, these soils have become waterlogged, and capillary action has carried salts to the surface. Some areas show a puffy salt layer at the surface, but these can be reclaimed by simple leaching, if supplied with plenty of irrigation water. Over very small areas, strongly alkaline soil of patches have developed, and these, being non-porous are difficult to reclaim. In the Upper Chaj and Rechna Doabs, the submontane area bordering the Peshawar-Mardan Plain, and in the eastern Potwar, the Bangar soils have developed under sub-humid conditions. Because of the higher rainfall, they have been leached of lime and are non-calcareous, medium to fine textured, and have a slightly higher organic content. These soils are also fertile when supplied with plenty of water and manure. Khaddar soils are formed from recent and present-day deposits along the rivers. Part of these soils are flooded each year, adding depositional layers of silt loam and silty clay loam. The organic content of these soils is low, but they are usually free of salts. Indus Delta Soils are formed of sub-recent alluvium and estuarine deposits. They cover the entire area of the Indus Delta from south of Hyderabad to the coat. Clayey soils, developed under flood water conditions, cover about one-third of the area. With irrigation, these soils are used for rice cultivation. Saline loamy soils cover most of the delta. Some with salt crust at the surface, have been reclaimed by simple leaching and better drainage. Extremely saline patches can be used only for poor grazing. Coastal estuarine deposits form the lower part of the Delta, which is a maze of tidal flats, basins, and sea-water creeks. The soils are extremely saline and barren, except for a weedy vegetation. Mountain SoilsMountain soils occur in the highland areas of the north and west, and are residual as well as transported. Along the steep crests and slopes, and in the broken hill country, shallow residual soils have developed. Under arid and semi-arid conditions, these soils are usually strongly calcareous, with low organic content. Further north, under sub-humid conditions, there is more leaching, and a higher organic content. In the mountain valleys, soils are formed from the alluvial infills of the streams. These soils are calcareous silt loams and sandy loams of low organic content. They are cultivated in patches only. In the sub-montane area of the Potwar Plateau, shallow residual soils and silty eroded loess have been formed. In places these soils are massive, susceptible to erosion, and strongly gullied, producing a dissected landscape. Lime content is high, and organic content low, but, with plenty of water, these soils are relatively productive. In the lowest parts of the inter-montane valleys and interior basins of the arid and semi-arid regions,

8 strongly saline soils develop. Excess of evaporation over precipitation leaves a thick crust of salts at the surface of the intermittent lakes. For the most part, these soils are barren. The margins carry low shrubs and salt bush, used for poor grazing. Sandy Desert Soils The soils extend over some parts of western Baluchistan, and the Cholistan and Thar Deserts. Thal desert soils occur in large sections of the Sind Sagar Doab. Desert soils include rolling to hilly sandy soils, and clayey flood plain soils. Where the soils are formed of deep sand, as in much of Baluchistan, they are moderately calcareous, and largely aeolian. In places, the windblown material is mixed with old alluvium. The arid and semi-arid desert sand areas have few possibilities for improvement, beyond very poor grazing

Makin' The Soil The process of soil formation happens in many ways. Here are five of the most important factors involved in soil formation. There are others, but these are the biggies. (1) It can be created because of the shape of the landscape. That shape is called the topography. When you have mountains, the sides of the mountains are said to have a slope. When you have a slope and it rains, there will be drainage. The runoff carries away small rocks and minerals. This runoff winds up in valleys or in the ocean. It slowly builds up and the small pieces make soil. (2) There are climatic effects that create soil. Moisture and rain combine with the temperature to do amazing things to rocks. We just explained that when it rains you have runoff and erosion. Those physical activities break down the rocks and hard surfaces. Temperature plays a role when you move below and above the freezing point. When water freezes, it expands. Rocks and soil that hold water can be cracked when the water freezes and expands. They pop open with a cracking sound! (3) What's in the soil is dependent on geologic factors. The type of soil under your feet is dependent on the bedrock deep below the surface. As the bedrock breaks down, smaller pieces move to the surface and mix with the existing soil. (4) In the same way that there are large geologic factors, chronological factors play an important part in the process. Chronological means time. You need time to make soil. That's it. Sediment can move around quickly but it takes a long time to break down bedrock. We can't just sit and watch this process happen. We have to study it over many years. Also, if we pollute our soil we can't renew it in our lifetime. It takes hundreds to thousands of years. (5) Soil is also created by biological factors. You'll find that soil is half minerals/rocks and half air/water. All sorts of biological things are happening in the air/water space. The organic material is most important. There are tiny living organisms (like bacteria) that break down organic stuff. The "stuff" could be dead leaves or dead animals. The organic stuff is called humus. There are also roots and tunneling creatures that work like the microbes. They turn the soil around and move it. They churn the pieces of soil.

9 Reasons For Low Organic Matter Content of Pakistan Soils The low organic matter content of Pakistan soils can be attributed to the following reasons. Climatic Conditions The mean annual temperature influences the processes of decomposition of organic matter. At high temperatures the decomposition proceeds very quickly. That is why high temperatures prevailing in Pakistan are conducive for a rapid decomposition and loss of organic matter. Soil Orders The differences of organic matter content among soil orders also play key role in determining the potential of a soil to keep a certain level of organic matter. The largest soil orders in Pakistan are Aridisol and Entisol, which are known to have lowest organic matter content among all the soil orders. So our soils naturally have lesser capacity to hold higher organic matter content. Soil Classification 1. Factors of Soil Formation 1.1. Parent material 1.2. Climate 1.3. Biota 1.4.Topography 1.5. Time Interactions of Soil Formation Factors Soil forms as a result of five soil formation factors. Differences in soil type within and between regions are a result of the interactions between these factors. 1) Parent material : unconsolidated material in which soil development occurs 2) Climate: particularly precipitation and temperature 3) Biota: living organisms including vegetation, microbes, soil animals, and human beings 4) Topography: slope, aspect, and elevation 5) Time: period that parent materials are subjected to soil formation 1.1. Parent material Parent material is the material from which a soil forms. It consists of unconsolidated and more or less chemically weathered mineral or organic material.

Numerous landform features were formed following glaciation and deposition of morainal (till) material. The animation below illustrates formation of outwash deposits formed by meltwater streams that issued from a glacier.

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The nature of the parent material influences both texture and the mineral composition of the soil. Soil parent material consists of rocks, which can be classified as: 1) Residual or sedentary: sediments developed in place (in situ) from underlying rock over a long period of intense weathering. 2) Cumulose: organic deposits developed in place from plant residues that have been preserved by a high water table, or some other factor that inhibits decomposition. Examples are peat (undecomposed or slightly decomposed organic matter) and muck (highly decomposed organic matter) 3) Transported: loose sediments or surficial material that were transported and deposited by gravity, water, ice, or wind. The following table lists transported parent materials and their modes of deposition. 1.2. Climate Climate determines the nature (physical, chemical or biological) and rate of weathering (that acts on parent material to form soil). The most important elements of climate for soil formation are precipitation and temperature. For example, the amount of precipitation determines the extent of leaching through a soil profile and seasonal temperature fluctuations influence the number and rate of chemical reactions and overall biological activity. 1.3. Biota Living organisms, including plants, microbes, soil animals, and humans, are collectively referred to as biota. Soil development is affected by both the type and number of organisms that live in and on the soil. Plants influence the amount of organic matter buildup in the soil. For example, soil developed under grassland vegetation has organic matter incorporated into the rooting zone, while in forest soils organic matter accumulates on the surface. Human activity also influences soil formation. Destruction of natural vegetation by changing the frequency and extent of natural fires or by soil tillage abruptly modifies the soil forming factors. These changes have influenced the relative distribution of forests and grasslands in many areas of British Columbia . 1.4.Topography There is a strong interaction between topography and vegetation and their influence on soil formation. Depressions in dry grassland areas are usually occupied by trees due to greater soil water content. As a result, these depressions have different soil types than adjacent areas. Aspect influences the angle at which the sun�s rays strike the earth�s surface. Slope and aspect together influence soil temperature, soil water content and vegetation, which in turn affects soil formation. For example, in the Northern Hemisphere cooler north-facing slopes are usually forested with slower soil development than on warmer south-facing grasslands . Consequently, a north-facing slope has a thinner soil than a south-facing slope on the same ridge.

11 Elevation influences vegetation and soil type. In the interior of British Columbia climate becomes cooler and more wet as elevation increases from valley bottoms to mountain tops. Such climate gradients are usually reflected in a shift from grassland to forest and alpine plant communities. There is a strong interaction between topography and vegetation and their influence on soil formation. The figure below illustrates how in a grassland-forest transition zone, trees occupy slight depressions where soil moisture accumulates. These depressions have different soil types than adjacent upland areas. This photo is from the Nicola Valley in interior British Columbia. 1.5. Time Soil formation is a slow process that takes hundreds or even thousands of years. A younger soil will reflect characteristics of the parent material better than an older soil, since insufficient time has elapsed to permit significant development. Canadian soils, including British Columbia�s, are relatively young when compared to soils of the southern United States. They have been developing since the recession of the last ice age 10,000 years ago. �The Oldest Life on Land�. Fossilized remnants of a microbial mat provide evidence that life existed on land as early as 2.6 to 2.7 billion years ago. The findings suggest that an oxygen atmosphere and a protective ozone layer were in place around Earth by that time. Review website for details. Interactions of Soil Formation Factors The formation of soil is a complex process, and the five soil formation factors are active simultaneously and interdependently. Individual factors are of interest because they help us simplify and explain soil formation. They are particularly useful for soil survey and mapping, since soils are stratified on the basis of individual formation factors.

Soils Pakistan’s soils are classified as pedocals, which comprise a dry soil group with high concentrations of calcium carbonate and a low content of organic matter; they are characteristic of a land with low and erratic precipitation. The major soil groupings are Indus basin soils, mountain soils, and sandy desert soils. However, the very mode of soil formation gives rise to their diversification even within small areas. These soils vary in texture, chemical composition, colour, and organic content from place to place. The Indus basin soils are mostly thick alluvium deposited by rivers and are of recent origin. Soils in the vicinity of river courses are the most recent and vary in texture from sand to silt loam and silty clay loams. They have a low organic content and are collectively known as the khaddar soils. Away from the river, toward the middle of the doabs, older alluvial soils (called bangar) are widely

12 distributed. These soils are medium to fine in texture, have low organic content, and are highly productive under conditions of irrigation and fertilization. In some waterlogged areas, however, these soils are salinized. Strongly alkaline soils are localized in some small patches. In the submontane areas under subhumid conditions these soils are noncalcareous and have slightly higher organic content. In the delta the estuarine soils are excessively saline and barren. Mountain soils are both residual (i.e., formed in a stationary position) and transported. Shallow residual soils have developed along the slopes and in the broken hill country. Those soils generally are strongly calcareous and have low organic content, but under subhumid conditions their organic content increases. Sandy desert soils cover the Cholistan part of Sind Sagar Doab and western Balochistan. They include both shifting sandy soils and clayey floodplain soils. These include moderately calcareous and eolian (wind-borne) soils. Climate Aridity is the most pervasive aspect of Pakistan’s climate, and its continental nature can be seen in the extremes of temperature. Pakistan is situated on the edge of a monsoonal (i.e., wet-dry) system. Precipitation throughout the country generally is erratic, and its volume is highly variable. The rainy monsoon winds, the exact margins of which vary from year to year, blow in intermittent bursts, and most moisture comes in the summer. Tropical storms from the Arabian Sea provide precipitation to the coastal areas but are also variable in character. The efficiency of the monsoonal precipitation is poor, because of its concentration from early July to mid-September, when high temperatures maximize loss through evaporation. In the north the mean annual precipitation at Peshawar is 13 inches (330 mm), and at Rawalpindi it reaches 37 inches (950 mm). In the plains, however, mean annual precipitation generally decreases from northeast to southwest, falling from about 20 inches (500 mm) at Lahore to less than 5 inches (130 mm) in the Indus River corridor and 3.5 inches (90 mm) at Sukkur. Under maritime influence, precipitation increases slightly to about 6 inches (155 mm) at Hyderabad and 8 inches (200 mm) at Karachi. The 20-inch (500-mm) precipitation line, which runs northwest from near Lahore, marks off the Potwar Plateau and a part of the Indus plain in the northeast; these areas receive enough rainfall for dry farming (farming without irrigation). South of this region, cultivation is confined mainly to riverine strips until the advent of irrigation. Most of the Balochistan plateau, especially in the west and south, is exceptionally dry.

13 Pakistan’s continental type of climate is characterized by extreme variations of temperature, both seasonally and daily. High elevations modify the climate in the cold, snow-covered northern mountains; temperatures on the Balochistan plateau are somewhat higher. Along the coastal strip, the climate is modified by sea breezes. In the rest of the country, temperatures reach great extremes in the summer; themean temperature during June is 100 °F (38 °C) in the plains, where the highest temperatures can exceed 117 °F (47 °C). Jacobabad, in Sind, has recorded the highest temperature in Pakistan, 127 °F (53 °C). In the summer, hot winds called loos blow across the plains during the day. Trees shed their leaves to avoid excessive moisture loss. The dry, hot weather is broken occasionally by dust storms and thunderstorms that temporarily lower the temperature. Evenings are cool; the diurnal variation in temperature may be as much as 20 to 30 °F (11 to 17 °C). Winters are cold, with minimum mean temperatures of about 40 °F (4 °C) in January. Plant and animal life Differences of latitude, elevation, soil type, and climate have favoured a variety ofplant growth. Drought-resistant vegetation in the desert consists of stunted thorny scrub, mostly acacia. The plains present a parkland view of scattered trees. Dry scrub forests, called rakhs, grow in parts of the arid plain. In the northern and northwestern foothills and plains, shrub forests, principally acacia, and wild olive are found. In the wetter parts of the northern and northwestern mountains, evergreen coniferous softwood forests, with some broad-leaved species, grow. Fir, deodar, blue pine (Pinus wallichiana), and spruce are the principal coniferous trees. At lower elevations, below 3,000 feet (900 metres), broad-leaved oaks, maples, birches, walnuts, and chestnuts predominate. Conifers are an important source of commercial timber. In the arid landscape of the Potwar Plateau, some hills are only thinly wooded. In the northern ranges of the Balochistan plateau are some groves of pine and olive. The babul tree(Acacia arabica) is common in the Indus River valley, as are many species of fruit trees. The country’s forest cover is naturally sparse, but it has been diminished further by excessive timber cutting and overgrazing. Destruction of natural habitats and excessive hunting have led to a reduction in the range of animal life in large parts of the country, but wildlife can still be found in abundance in some areas. The variety of large mammals in the northern mountains includes brown bears,Asiatic black bears (Ursus thibetanus, also known as the Himalayan bear), leopards, rare snow leopards, Siberian ibex (Capra ibex sibirica), and wild sheep, including markhors, Marco Polo sheep (Ovis ammon polii, a type of argali), and Chiltan wild goats (Capra aegagrus chialtanensis).

14 Manchhar Lake in Sind has many aquatic birds, including mallards, teals, shovelers, spoonbills, geese, pochards, and wood ducks. Crocodiles, gavials (crocodile-like reptiles), pythons, and wild boars inhabit the Indus River delta area. The Indus River itself is home to the Indus river dolphin, a freshwater dolphin whose habitat has been severely stressed by hunting, pollution, and the creation of dams and barrages. At least two types of sea turtles, the green and olive ridley, nest on the Makran coast. Desert gazelles are widely distributed, including nilgais, chinkaras (Gazella gazella bennetti), and muntjacs. Jackals, foxes, and various wild cats (including Eurasian lynxes, caracals, fishing cats, and jungle cats [Felis chaus]) are also found throughout the country. Despite occasional reported sightings of the Asiatic cheetah, that species is likely extinct in Pakistan. A series of national parks and game preserves was established beginning in the 1970s. However, a number of species have been declared endangered, including the Indus river dolphin,snow leopard, and gavial. Topography The up and down changes in hills and mountains of a particular location is referred to by scientists as topography. Topography has an important influence in how soils form. The first topographic factor is steepness of hill and mountain slopes. All soils around the Earth are slowly getting deeper and deeper, as lower levels of dirt are being turned into soil. At the same time wind and water carry the surface soil away through erosion. In areas which are flat, the soil typically tends to get deeper quicker than the surface erodes away. On steep slopes erosion is usually quicker than the formation of new soil beneath. The result is that flat locations typically have a deeper more mature soil layer than do locations with a steep slope. The second topographic factor effecting soil formation is drainage, or in other words, how well is the soil able to get rid of extra water via draining it. Most locations have excellent drainage, but some locations do not. Some locations become water logged. This water blocks oxygen, which is important to soil formation. Thus in these locations soil formation can become seriously hindered.