Bahan kuliah PR (4): Rangeland

Rangeland refers to expansive, mostly unimproved lands on which a significant proportion of the natural vegetation is native grasses, grass-like plants, forbs, and shrubs. Rangeland also consists of areas seeded to native or adapted introduced species that are managed like native vegetation. Rangelands include natural grasslands, savannas, shrublands, many deserts, tundra, alpine communities, coastal marshes, and wet meadows. Rangeland is generally arid, semi-arid, sub-humid or otherwise unsuitable for cultivation.

arid

In general terms, the climate of a locale or region is said to be arid when it is characterized by a severe lack of available water, to the extent of hindering or even preventing the growth and development of plant and animal life. As a result, environments subject to arid climates tend to lack vegetation and are called xeric or desertic.

Semi arid

Semi-arid climate or steppe climate generally describes climatic regions that receive low annual rainfall (250-500 mm or 10-20 in). A more precise definition is given by the Köppen climate classification that treats steppe climates (BS) as intermediates between the desert climates (BW) and humid climates in ecological characteristics and agricultural potential. The Köppen climate classification allows adjustments for temperature and for seasonality of precipitation, effectively excluding forested regions (such as those in most of Canada and Siberia)

Tillage

Tillage, or cultivation is the agricultural preparation of the soil by digging it up. Tillage can also mean the land that is tilled the process of fostering the growth of something; "the cultivation of bees for honey" : the act of raising or growing plants (especially on a large scale) The process of promoting the growth of a biological culture.

Tillage systems

intensive tillage

Intensive tillage systems leave less than 15% crop residue cover or less than 500 pounds per acre (560 kg/ha) of small grain residue. These types of tillage systems are often referred to as conventional tillage systems but as reduced and conservation tillage systems have been more widely adopted, it is often not appropriate to refer to this type of system as conventional. These systems involve often multiple operations with implements such as a mold board plow, disk, and/or chisel plow. After Moldboard plowing, a disk is often used to break clods. Then a a finisher .....with a harrow, rolling basket, and cutter head can be used ..... can be used to prepare the seed bed. There are many variations.

Reduced tillage

Reduced tillage systems leave between 15 and 30% residue cover on the soil or 500 to 1000 pounds per acre (560 to 1100 kg/ha) of small grain residue during the critical erosion period. This may involve the use of a chisel plow, field cultivators, or other implements. See the general comments below to see how they can effect the amount of residue.

Conservation tillage

Conservation tillage systems are methods of soil tillage which leave a minimum of 30% of crop residue on the soil surface or at least 1,000 lb/ac (1,100 kg/ha) of small grain residue on the surface during the critical soil erosion period. This slows water movement, which reduces the amount of soil erosion; it also warms the soil, enabling the next year’s crop to be planted earlier in the spring. Conservation tillage systems also benefit farmers by reducing fuel consumption and soil compaction. By reducing the number of times the farmer travels over the field, farmers realize significant savings in fuel and labor. Conservation tillage was used on about 38%, 109,000,000 acres (440,000 km²), of all US cropland, 293,000,000 acres (1,190,000 km²) planted as of 2004 according to the USDA.

• No-till
• Strip-Till
• Mulch-Till
• Ridge-Till

Definitions

Primary tillage loosens the soil and mixes in fertilizer and/or plant material, resulting in soil with a rough texture.

Secondary tillage produces finer soil and sometimes shapes the rows. It can be done by a using various combinations of equipment: plough, disk plough, harrow, dibble, hoe, shovel, rotary tillers, subsoiler, ridge or bed forming tillers, roller.

Weed plants (seeds, tubers, etc.) may be exhausted by repeated tilling. The weeds expend energy to reach the surface, and then get turned into the soil by tilling. The cycle is repeated until the weeds are dead.

History of tilling

Tilling was first performed via human labor, sometimes involving slaves. Hoofed animals could also be used to till soil via trampling. The wooden plough was then invented. It could be pulled by mule, ox, elephant, water buffalo, or similar sturdy animal. Horses are generally unsuitable, though breeds such as the Clydesdale could work. The steel plough allowed farming in the American Midwest, where tough prairie grasses and rocks caused trouble. Soon after 1900, the farm tractor was introduced, which eventually made modern large-scale agriculture possible.

alternatives to tilling

Modern agricultural science has greatly reduced the use of tillage. Crops can be grown for several years without any tillage through the use of herbicides to control weeds, genetically modified crops that tolerate packed soil, and equipment that can plant seeds or fumigate the soil without really digging it up. This practice, called no-till farming, reduces costs and environmental change by reducing soil erosion and diesel fuel usage (although it does require the use of pesticides). Most organic farming tends to require extensive tilling, as did most farming throughout history, although researchers are investigating farming in polyculture that would eliminate the need for both tillage and pesticides, such as no-dig gardening.

In the United States, around 399 million acres (1,610,000 km²) of rangeland are privately owned. The Bureau of Land Management manages about 167 million acres (676,000 km²) of publicly owned rangeland, with the United States Forest Service managing approximately 95 million acres (380,000 km²) more. Ranchers may lease portions of this public rangeland and pay a fee based on the number and type of livestock and the period for which they are on the land. Many western states have open range laws. In these states, all land, both public and private, is designated as open range unless it is within city limits. In open range, it becomes the responsibility of the land owner to keep unwanted livestock off their land and the livestock owner is not liable for any damage caused by the livestock.

In Kenya, Rangelands make up for 75% of the land surface area,and are largely inhabited by nomadic pastrolists who are largely dependent on livestock. This movement often brings along an incursion of different diseases with the common one being the rinderpest virus in the Kenyan wildlife population from the Somalian ecosystem.

Rangeland is a prominent feature of rural Canada. A provincial jurisdiction, administration and policy regarding range use varies across the country. Like many Commonwealth countries, public tenures on crown land for the purpose of range activities is common in geographically compatible areas. Reconciling the economic needs of ranchers and the need for environmental conservation is one of the primary themes in modern range discourse.

In Australia, pastoral leases may be held over crown land and beef cattle or sheep grazed on large holdings called Sheep stations or Cattle stations.

The Society for Range Management (rangelands.org) is an international organization of natural resource scientists, researchers, educators, land management agency officials, and public and private land managers devoted to the conservation and sustainable stewardship of the world's diverse rangelands. The Society is open to anyone engaged in or interested in any aspect of the study, management, or use of rangelands, and publishes both a scientific journal, Rangeland Ecology and Management, and Rangelands, a journal of practical applied ecology, perspective and contemporary rangelands issues.

Bahan kuliah PR (3): Savanna

savanna or savannah is a grassland ecosystem with scattered trees or shrubs. In savannas trees are small or widely spaced so that the canopy does not close. It is often believed that savannas are characterized by widely spaced, scattered trees, however in many savanna communities tree densities are higher and trees are more regularly spaced than in forest communities. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.^[1] Savannas are also characterised by seasonal water availability, with the majority of rainfall being confined to one season of the year. Savannas can be associated with several types of biomes. Savannas are frequently seen as a transitional zone, occurring between forest and desert or prairie.

Although the term savanna is believed to have originally come from a Native American word describing "land which is without trees but with much grass either tall or short" (Oviedo y Valdes, 1535), by the late 1800s it was used to mean "land with both grass and trees". It now refers to land with grass and either scattered trees or an open canopy of trees.

Threats to savannas

Changes in fire management

Savannas are subject to regular fires and the ecosystem appears to be the result of human use of fire. For example Native Americans created subtropical savannas by periodic burning in some areas of the US southeastern coast where fire-resistant Longleaf Pine was the dominant species.^[2] Aboriginal burning appears to have been responsible for the widespread occurrence of savanna in tropical Australia and New Guinea^[3] and savannas in India are a creation of human fire use.^[4] The maquis shrub savannas of the Mediterranean region were likewise created and maintained by anthropogenic fire.^[5]

These fires are usually confined to the herbaceous layer and do little long term damage to mature trees. However, these fires do serve to either kill or suppress tree seedlings, thus preventing the establishment of a continuous tree canopy which would prevent further grass growth. Prior to European settlement aboriginal land use practices, including fire, influenced vegetation^[6] and may have maintained and modified savanna flora.^[7][8] It has been suggested by many authors^[9][6] that aboriginal burning created a structurally more open savanna landscape. Aboriginal burning certainly created a habitat mosaic that probably increased biodiversity and changed the structure of woodlands and geographic range of numerous woodland species.^[6][10] It has been suggested by many authors^[9][11] that with the removal or alteration of traditional burning regimes many savannas are being replaced by forest and shrub thickets with little herbaceous layer.

The consumption of herbage by introduced grazers in savanna woodlands has led to a reduction in the amount of fuel available for burning and resulted in fewer and cooler fires.^[12] The introduction of exotic pasture legumes has also led to a reduction in the need to burn to produce a flush of green growth because legumes retain high nutrient levels throughout the year, and because fires can have a negative impact on legume populations which causes a reluctance to burn.^[13]

Grazing and browsing animals

The closed forests types such as broadleaf forests and rainforests are usually not grazed owing to the closed structure precluding grass growth, and hence offering little opportunity for grazing.^[14] In contrast the open structure of savannas allows the growth of a herbaceous layer and are commonly used for grazing domestic livestock.^[15] As a result much of the world's savannas have undergone change as a result of grazing by sheep, goats and cattle, ranging from changes in pasture composition to woody weed encroachment.^[16]

The removal of grass by grazing affects the woody plant component of woodland systems in two major ways. Grasses compete with woody plants for water in the topsoil and removal by grazing reduces this competitive effect, potentially boosting tree growth.^[17] In addition to this effect the removal of fuel reduces both the intensity and the frequency of fires which may control woody plant species.^[18] Grazing animals can have a more direct effect on woody plants by the browsing of palatable woody species. There is evidence that unpalatable woody plants have increased under grazing in savannas.^[19] Grazing also promotes the spread of weeds in savannas by the removal or reduction of the plants which would normally compete with potential weeds and hinder establishment.^[6] In addition to this cattle and horses are implicated in the spread of the seeds of weed species such as Prickly Acacia (Acacia nilotica) and Stylo (Stylosanthes spp.).^[20] These alterations in savanna species composition brought about by grazing can alter ecosystem function, and are exacerbated by overgrazing and poor land management practices.

Introduced grazing animals can also affect soil condition through physical compaction and break-up of the soil caused by the hooves of animals and through the erosion effects caused by the removal of protective plant cover. Such effects are most likely to occur on land subjected to repeated and heavy grazing.^[21] The effects of overstocking are often worst on soils of low fertility and in low rainfall areas below 500 mm, as most soil nutrients in these areas tend to be concentrated in the surface so any movement of soil can lead to severe degradation. Alteration in soil structure and nutrient levels affects the establishment, growth and survival of plant species and in turn can lead to a change in woodland structure and composition.

Tree clearing

Large areas of savanna have been cleared of trees, and this clearing is continuing today. For example until recently 480,000 ha of savanna were cleared annually in Australia alone primarily to improve pasture production.^[6] Substantial savanna areas have been cleared of woody vegetation and much of the area that remains today is vegetation that has been disturbed by either clearing or thinning at some point in the past.

Clearing is carried out by the grazing industry in an attempt to increase the quality and quantity of feed available for stock and to improve the management of livestock. The removal of trees from savanna land removes the competition for water from the grasses present, and can lead to a two to fourfold increase in pasture production, as well as improving the quality of the feed available.^[22] Since stock carrying capacity is strongly correlated with herbage yield there can be major financial benefits from the removal of trees.^[23] The removal of trees also assists grazing management. For example in sheep grazing regions of dense tree and shrub cover harbours predators, leading to increased stock losses^[24] while woody plant cover hinders mustering in both sheep and cattle areas.^[25]

A number of techniques have been employed to clear or kill woody plants in savanna. Early pastoralists used felling and ringbarking, the removal of a ring of bark and sapwood, as a means of clearing land^[26]). In the 1950’s arboricides suitable for stem injection were developed. War-surplus heavy machinery was made available, and these were used for either pushing timber, or for pulling using a chain and ball strung between two machines. These two new methods of timber control, along with the introduction and widespread adoption of several new pasture grasses and legumes promoted a resurgence in tree clearing. The 1980’s also saw the release of soil-applied arboricides, notably tebuthiuron, that could be utilised without cutting and injecting each individual tree.

In many ways ‘artificial’ clearing, particularly pulling, mimics the effects of fire and, in savannas adapted to regeneration after fire as most Queensland savannas are, there is a similar response to that after fire.^[27] Tree clearing in many savanna communities, although causing a dramatic reduction in basal area and canopy cover, often leaves a high percentage of woody plants alive either as seedlings too small to be affected or as plants capable of re-sprouting from lignotubers and broken stumps. A population of woody plants equal to half or more of the original number often remains following pulling of eucalypt communities, even if all the trees over 5 metres are uprooted completely.

Exotic plant species

A number of exotic plants species have been introduced to the savannas around the world. Amongst the woody plant species are serious environmental weeds such as Prickly Acacia (Acacia nilotica), Rubbervine (Cryptostegia grandiflora), Mesquite (Prosopis spp.), Lantana (Lantana camara and L. montevidensis) and Prickly Pear (Opuntia spp.) A range of herbaceous species have also been introduced to these woodlands, either deliberately or accidentally including Rhodes grass and other Chloris species, Buffel grass (Cenchrus ciliaris), Giant rats tail grass (Sporobolus pyramidalis) parthenium (Parthenium hysterophorous) and stylos (Stylosanthes spp.) and other legumes. These introductions have the potential to significantly alter the structure and composition of savannas worldwide, and have already done so in many areas through a numbers of processes including altering the fire regime, increasing grazing pressure, competing with native vegetation and occupying previously vacant ecological niches.^[27][28]

Climate change

There exists the possibility that human induced climate change in the form of the greenhouse effect may result in an alteration of the structure and function of savannas. Some authors^[29] have suggested that savannas and grasslands may become even more susceptible to woody plant encroachment as a result of greenhouse induced climate change. A recent case described involved a savanna increasing its range at the expense of forest in response to climate variation, and potential exists for similar rapid, dramatic shifts in vegetation distribution as a result of global climate change, particularly at ecotones such as savannas so often represent.^[30]

Savanna Ecoregion

· Tropical and subtropical savannas are classified with tropical and subtropical grasslands and shrublands as the tropical and subtropical grasslands, savannas, and shrublands biome. The savannas of Africa, including the Serengeti, famous for its wildlife, are typical of this type.

· Temperate savannas are mid-latitude savannas with wetter summers and drier winters. They are classified with temperate savannas and shrublands as the temperate grasslands, savannas, and shrublands biome.

· Mediterranean savannas are mid-latitude savannas in Mediterranean climate regions, with mild, rainy winters and hot, dry summers, part of the Mediterranean forests, woodlands, and shrub biome. The oak tree savannas of California, part of the California chaparral and woodlands ecoregion, fall into this category.

· Flooded savannas are savannas that are flooded seasonally or year-round. They are classified with flooded savannas as the flooded grasslands and savannas biome, which occurs mostly in the tropics and subtropics.

· Montane savannas are high-altitude savannas, located in a few spots around the world's high mountain regions, part of the montane grasslands and shrublands biome. The highland savannas of the Angolan scarp savanna and woodlands ecoregion are an example.

Bahan kuliah PR (2): Ranch

A ranch is an area of landscape, including various structures, given primarily to the practice of ranching, the practice of raising grazing livestock such as cattle or sheep for meat or wool. The word most often applies to livestock-raising operations in the western United States and Canada, though there are ranches in other areas. People who own or operate a ranch are called stockgrowers or ranchers. Ranching is also a method used to raise less common livestock such as elk, American Bison or even ostrich and emu.

Ranches generally consist of large areas, but may be of nearly any size. In the western United States, many ranches are a combination of privately owned land supplemented by grazing leases on land under the control of the federal Bureau of Land Management. If the ranch includes arable or irrigated land, the ranch may also engage in a limited amount of farming, raising crops for feeding the animals, such as hay and feed grains.

Ranches that cater exclusively to tourists are called dude ranches. Most working ranches do not cater to guests, though they may allow private hunters or outfitters onto their property to hunt native wildlife. However, in recent years, a few struggling smaller operations have added some dude ranch features, such as horseback rides, cattle drives or guided hunting, in an attempt to bring in additional income. Ranching is part of the iconography of the "Wild West" as seen in Western movies.

Origins of ranching

Ranching and the cowboy tradition originated in Spain, out of the necessity to handle large herds of grazing animals on dry land from horseback. During the Reconquista, members of the Spanish nobility and various military orders received large land grants that the kingdom of Castile had conquered from the Moors. These landowners were to defend the lands put into their control and could use them for earning revenue. In the process it was found that open-range breeding of sheep and cattle (under the Mesta system) was the most suitable use for vast tracts, particularly in the parts of Spain now known as Castilla-La Mancha, Extremadura and Andalusia.

History in North America

Spanish North America

When the Conquistadors came to the Americas in the 16th century, followed by settlers, they brought their cattle and cattle-raising techniques with them. Huge land grants by the Spanish (and later Mexican) government, part of the hacienda system, allowed large numbers of animals to roam freely over vast areas. A number of different traditions developed, often related to the original location in Spain from which a settlement originated. For example, many of the traditions of the Jalisco charros in southern Mexico come from the Salamanca charros of Castile. The Vaquero tradition of Northern Mexico was more organic, developed to adapt to the characteristics of the region from Spanish sources by cultural interaction between the Spanish elites and the native and mestizo peoples.^[1]

United States of America

As settlers from the United States moved west, they brought cattle breeds developed on the east coast and in Europe along with them, and adapted their management to the drier lands of the west by borrowing key elements of the Spanish vaquero culture. Deep Hollow Ranch, 110 miles (180 km) east of New York City in Montauk, New York, claims to be the first ranch in the United States, having continuously operated since 1658.

The Open Range

The prairie and desert lands of what today is Mexico and the western United States were well-suited to "open range" grazing. For example, American bison had been a mainstay of the diet for the Native Americans in the Great Plains for centuries. Likewise, cattle and sheep, descended from animals brought over from Europe, were simply turned loose in the spring after their young were born and allowed to roam with little supervision and no fences, then rounded up in the fall, with the mature animals driven to market and the breeding stock brought close to the ranch headquarters for greater protection in the winter. The use of livestock branding allowed the cattle owned by different ranchers to be identified and sorted. Beginning with the settlement of Texas in the 1840s, and expansion both north and west from that time, through the Civil War and into the 1880s, ranching dominated western economic activity.

Along with ranchers came the need for agricultural crops to feed both humans and livestock, and hence many farmers also came west along with ranchers. Many operations were "diversified," with both ranching and farming activities taking place. With the Homestead Act of 1862, more settlers came west to set up farms. This created some conflict, as increasing numbers of farmers needed to fence off fields to prevent cattle and sheep from eating their crops. Barbed wire, invented in 1874, gradually made inroads in fencing off privately owned land, especially for homesteads. There was some reduction of land on the Great Plains open to grazing.

End of the Open Range

he end of the open range was not brought about by a reduction in land due to arable farming, but by overgrazing. Cattle stocked on the open range created a tragedy of the commons as each rancher sought increased economic benefit by grazing too many animals on public lands that "nobody" owned. However, being a non-native species, the grazing patterns of ever-increasing numbers of cattle slowly reduced the quality of the rangeland, in spite of the simultaneous massive slaughter of American bison that occurred. The winter of 1886-1887 was one of the most severe on record, and livestock that were already stressed by reduced grazing died by the thousands. Many large cattle operations went bankrupt, and others suffered severe financial losses. Thus, after this time, ranchers also began to fence off their land and negotiated individual grazing leases with the American government so that they could keep better control of the pasture land available to their own animals.

Ranching in Hawaii

Ranching in Hawaii developed independently of that in the continental United States. In colonial times, Capt. George Vancouver gave several head of cattle to the Hawaiian king, Pai`ea Kamehameha, monarch of the Hawaiian Kingdom, and by the early 1800s, they had multiplied considerably, to the point that they were wreaking havoc throughout the countryside. About 1812, John Parker, a sailor who had jumped ship and settled in the islands, received permission from Kamehameha to capture the wild cattle and develop a beef industry.

The Hawaiian style of ranching originally included capturing wild cattle by driving them into pits dug in the forest floor. Once tamed somewhat by hunger and thirst, they were hauled out up a steep ramp, and tied by their horns to the horns of a tame, older steer (or ox) and taken to fenced-in areas. The industry grew slowly under the reign of Kamehameha's son Liholiho (Kamehameha II). When Liholiho's son, Kauikeaouli (Kamehameha III), visited California, then still a part of Mexico, he was impressed with the skill of the Mexican vaqueros. In 1832, he invited several to Hawaii to teach the Hawaiian people how to work cattle.

The Hawaiian cowboy came to be called the paniolo, a Hawaiianized pronunciation of español. Even today, the traditional Hawaiian saddle and many other tools of the ranching trade have a distinctly Mexican look, and many Hawaiian ranching families still carry the surnames of vaqueros who made Hawaii their home.

Ranching in South America

In Argentina, ranches are known as estancias, and in Brazil, they are called fazendas. In much of South America , including Ecuador and Colombia, the term hacienda may be used. Ranchero or Ranchos are also generic term used throughout Latin America.

In the colonial period, Pampas regions of South America, particularly the Semi-arid Pampas of Argentina, were often well-suited to ranching and a tradition developed that largely paralleled that of Mexico and the United States. However, in the 20th century, cattle raising expanded into less-suitable areas. Particularly in Brazil, the 20th century marked the rapid growth of deforestation as rain forest lands were cleared by slash and burn methods that allowed grass to grow for livestock, but also led to the depletion of the land within only a few years. Many of Indigenous peoples of the rain forest opposed this form of cattle ranching and protested the forest being burnt down to set up grazing operations and farms. This conflict is still a concern in the region today.

Ranches outside the Americas

In Spain, where the origins of ranching can be traced, there are ganaderías operating on dehesa-type land, where fighting bulls are raised.

In Australia, ranches are known as 'stations' usually in the context of what stock they carry - usually referred to as Cattle stations or Sheep stations. They exist mainly on dry rangeland in the outback and many were originally administered as pastoral leases by state governments. Owners and employees are known as Stockmen, jackaroos, and drovers rather than ranchers or cowboys. Australian sheep and cattle stations are larger than ranches in the United States. For example, one of the largest is Anna Creek station at 34,000 km².

New Zealanders use the term runs.

The term "ranch" and the need for vast grazing area is not used in British agriculture. The nation has far less land area, and sufficient rainfall to allow the raising of cattle on much smaller areas. From medieval times, cattle were traditionally raised in the small-area bocage. For similar reasons, the concept of a "ranch" is also not seen to any significant degree in most of western Europe. The only stock-raising properties in the British Isles that are anywhere close to the size of the smaller ranches in other nations are the largest hill farms in the upland areas of the United Kingdom.

Bahan Kuliah Padang Rumput (1): Grassland

Grasslands are areas where the vegetation is dominated by grasses (Poaceae) and other herbaceous (non-woody) plants (forbs). Plants of the sedge (Cyperacae) and rush (Juncaceae) families can also be frequent in grasslands. Grasslands occur naturally on all continents except Antarctica, and in many other areas they have replaced the natural vegetation due to human influence. In temperate latitudes, such as north-west Europe, grasslands are dominated by perennial species, whereas in warmer climates annual species form a greater component of the vegetation.^[1]

Grasslands can be found in most terrestrial climates. Grassland vegetation can vary in height from very short, as in chalk downland where the vegetation may be less than 30 cm high, to quite tall, as in the case of North American tallgrass prairie, South American grasslands and African savannah. Woody plants, shrubs or trees, may occur on some grasslands - forming wooded, scrubby or semi-wooded grassland, such as the African savannahs or the Iberian dehesa. Such grasslands are sometimes referred to as wood-pasture or savannah woodland. Grasslands cover nearly fifty percent of the land surface of the continent of Africa.^[2] While grasslands in general support diverse wildlife, given the lack of hiding places for predators, the African Savannah regions support a much greater diversity in wildlife than do temperate grasslands.^[3]

The appearance of mountains in the western United States during the Miocene and Pliocene epochs, a period of some 25 million years, created a continental climate favorable to the evolution of grasslands. Existing forest biomes declined, and grasslands became much more widespread. Following the Pleistocene Ice Ages, grasslands expanded in range in the hotter, drier climates, and began to become the dominant land feature worldwide.^[4]

As flowering plants, grasses grow in great concentrations in climates where annual rainfall ranges between 500 mm and 900 mm (approximately 20 to 35 inches).^[5] The root systems of perennial grasses and forbs form complex mats that hold the soil in place. Mites, insect larvae, nematodes and earthworms inhabit deep soil, which can reach 20 feet underground in undisturbed grasslands on the richest soils of the world. These invertebrates, along with symbiotic fungi, extend the root systems, break apart hard soil, enrich it with urea and other natural fertilizers, trap minerals and water and promote growth (Chadwick 1995). Some types of fungi make the plants more resistant to insect and microbial attacks.

Climate and grasslands

Grasslands receive about 380 to 900 mm (15 to 36 in) of rain per year, as compared with deserts, which receive less than 300 mm (12 in) and tropical rainforests, which receive more than 2,000 mm (80 in).^[6] While extreme temperatures may occur in some grasslands, normally they range between -20 to 30 degrees Celsius.^{[citation needed]} Tropical grasslands have dry and wet seasons, but remain warm all the time.^{[citation needed]} Temperate grasslands have cold winters and warm summers with rain or some snow. Since some grasses die back above ground annually,^{[citation needed]} the soil and the sod protect the roots and the new buds from the cold of winter or dry conditions.

Grassland biodiversity and conservation

Grasslands dominated by unsown wild-plant communities ("unimproved grasslands") can be called either natural or 'semi-natural' habitats. The majority of grasslands in temperate climates are 'semi-natural', although their plant communities are natural, their maintenance depends upon anthropogenic activities such as low-intensity farming. Farming maintains these grasslands through grazing and cutting regimes. These grasslands contain many species of wild plants - grasses, sedges, rushes and herbs - 25 or more species per square metre is not unusual.^{[citation needed]} Chalk downlands in England can support over 40 species per square metre. In many parts of the world, few examples have escaped agricultural improvement (fertilising, weed killing, ploughing or re-seeding). For example, original North American prairie grasslands or lowland wildflower meadows in the UK are now rare and their associated wild flora equally threatened. Associated with the wild-plant diversity of the "unimproved" grasslands is usually a rich invertebrate fauna; also there are many species of birds that are grassland "specialists" - for example snipe, or the Great Bustard. Agriculturally improved grasslands, which dominate modern intensive agricultural landscapes, are usually poor in wild plant species due to the original diversity of plants having been destroyed by cultivation,^{[citation needed]} the original wild-plant communities having been replaced by sown monocultures of cultivated varieties of grasses and clovers, such as Perennial ryegrass and White Clover.^{[citation needed]} In many parts of the world "unimproved" grasslands are one of the most threatened habitats, and a target for acquisition by wildlife conservation groups or for special grants to landowners who are encouraged to manage them appropriately.

Human impact and economic importance

Grasslands are of vital importance for raising livestock for human consumption and for milk and other dairy products.

Grassland vegetation remains dominant in a particular area usually due to grazing, cutting (such as for hay), or natural or man-made fires, all discouraging colonisation by and survival of tree and shrub seedlings.^{[citation needed]} Fire was used in North America by the Native Americans as a means of maintaining grassland.^{[citation needed]} Some of the world's largest expanses of grassland are found in African savannah, and these are maintained by wild herbivores as well as by nomadic pastoralists and their cattle, sheep or goats.^{[citation needed]}

Grasslands may occur naturally or as the result of human activity. Grasslands created and maintained by human activity are called anthropogenic grasslands. Hunting peoples around the world often set regular fires to maintain and extend grasslands, and prevent fire-intolerant trees and shrubs from taking hold. The tallgrass prairies in the American Midwest may have been extended eastward into Illinois, Indiana, and Ohio by human agency. Much grassland in north-west Europe developed after the Neolithic Period, when people gradually cleared the forest to create areas for raising their livestock.

Types of grassland

Tropical and subtropical grasslands

These grasslands are classified with tropical and subtropical savannas and shrublands as the tropical and subtropical grasslands, savannas, and shrublands biome. Notable tropical and subtropical grasslands include the Llanos grasslands of northern South America.

Temperate grasslands

Mid-latitude grasslands, including the Prairie of North America, the Pampa of Argentina, calcareous downland, and the steppes of Europe. They are classified with temperate savannas and shrublands as the temperate grasslands, savannas, and shrublands biome. Temperate grasslands are the home to many large herbivores, such as bison, gazelles, zebras, rhinoceroses, and wild horses. Carnivores like lions, wolves and cheetahs are also found in temperate grasslands. Other animals of this region include: deer, prairie dogs, mice, jack rabbits, skunks, coyotes, snakes, fox, owls, badgers, blackbirds, grasshoppers, meadowlarks, sparrows, quails, and hawks.

Flooded grasslands

Grasslands that are flooded seasonally or year-round, like the Everglades of Florida or the Pantanal of Brazil, Bolivia and Paraguay. They are classified with flooded savannas as the flooded grasslands and savannas biome and occur mostly in the tropics and subtropics.

Montane grasslands

High-altitude grasslands located on high mountain ranges around the world, like the Páramo of the Andes Mountains. They are part of the montane grasslands and shrublands biome, and also constitute alpine tundra.

Polar grasslands

Similar to montane grasslands, arctic tundra can have grasses. However high soil moisture means that few tundras are grass-dominated today. However, during the Pleistocene ice ages, a polar grassland known as steppe-tundra occupied large areas of the Northern hemisphere.

Xeric grasslands

Also called desert grasslands, these are sparse grasslands located in deserts and xeric shrublands ecoregions.