Forestry is the science and craft of creating, using and repairing forests and associated resources for human and environmental benefits. Forestry is practiced in natural stands; the science of forestry has elements that belong to the biological, social and managerial sciences. Modern forestry embraces a broad range of concerns, in what is known as multiple-use management, including the provision of timber, fuel wood, wildlife habitat, natural water quality management, recreation and community protection, aesthetically appealing landscapes, biodiversity management, watershed management, erosion control, preserving forests as "sinks" for atmospheric carbon dioxide. A practitioner of forestry is known as a forester. Other common terms are: a silviculturalist. Silviculture is narrower than forestry, being concerned only with forest plants, but is used synonymously with forestry. Forest ecosystems have come to be seen as the most important component of the biosphere, forestry has emerged as a vital applied science and technology.
Forestry is an important economic segment in various industrial countries. For example, in Germany, forests cover nearly a third of the land area, wood is the most important renewable resource, forestry supports more than a million jobs and about €181 billion of value to the German economy each year; the preindustrial age has been dubbed by Werner Sombart and others as the'wooden age', as timber and firewood were the basic resources for energy and housing. The development of modern forestry is connected with the rise of capitalism, economy as a science and varying notions of land use and property. Roman Latifundiae, large agricultural estates, were quite successful in maintaining the large supply of wood, necessary for the Roman Empire. Large deforestations came with after the decline of the Romans; however in the 5th century, monks in the Byzantine Romagna on the Adriatic coast, were able to establish stone pine plantations to provide fuelwood and food. This was the beginning of the massive forest mentioned by Dante Alighieri in his 1308 poem Divine Comedy.
Similar sustainable formal forestry practices were developed by the Visigoths in the 7th century when, faced with the ever-increasing shortage of wood, they instituted a code concerned with the preservation of oak and pine forests. The use and management of many forest resources has a long history in China as well, dating back to the Han dynasty and taking place under the landowning gentry. A similar approach was used in Japan, it was later written about by the Ming dynasty Chinese scholar Xu Guangqi. In Europe, land usage rights in medieval and early modern times allowed different users to access forests and pastures. Plant litter and resin extraction were important, as pitch was essential for the caulking of ships and hunting rights and building, timber gathering in wood pastures, for grazing animals in forests; the notion of "commons" refers to the underlying traditional legal term of common land. The idea of enclosed private property came about during modern times. However, most hunting rights were retained by members of the nobility which preserved the right of the nobility to access and use common land for recreation, like fox hunting.
Systematic management of forests for a sustainable yield of timber began in Portugal in the 13th century when Afonso III of Portugal planted the Pinhal do Rei near Leiria to prevent coastal erosion and soil degradation, as a sustainable source for timber used in naval construction. His successor Dom Dinis continued the forest exists still today. Forest management flourished in the German states in the 14th century, e.g. in Nuremberg, in 16th-century Japan. A forest was divided into specific sections and mapped; as timber rafting allowed for connecting large continental forests, as in south western Germany, via Main, Neckar and Rhine with the coastal cities and states, early modern forestry and remote trading were connected. Large firs in the black forest were called "Holländer ``. Large timber rafts on the Rhine were 200 to 400m in length, 40m in width and consisted of several thousand logs; the crew consisted of 400 to 500 men, including shelter, bakeries and livestock stables. Timber rafting infrastructure allowed for large interconnected networks all over continental Europe and is still of importance in Finland.
Starting with the sixteenth century, enhanced world maritime trade, a boom in housing construction in Europe and the success and further Berggeschrey of the mining industry increased timber consumption sharply. The notion of'Nachhaltigkeit', sustainability in forestry, is connected to the work of Hans Carl von Carlowitz, a mining administrator in Saxony, his book Sylvicultura oeconomica, oder haußwirthliche Nachricht und Naturmäßige Anweisung zur wilden Baum-Zucht was the first comprehensive treatise about sustainable yield forestry. In the UK, and, to an extent, in continental Europe, the enclosure movement and the clearances favored enclosed private property; the Agrarian reformers, early economic writers and scientists tried to get rid of the traditional commons. At the time, an alleged tragedy of the commons together with fears of a Holznot, an imminent wood shortage played a watershed role in the controversies about cooperative land use patterns; the practice of establishing tree plantations in the British Isles was promoted by John Evelyn, though it had acquired some populari
Sustainable forest management
Sustainable forest management is the management of forests according to the principles of sustainable development. Sustainable forest management has to keep the balance between three main pillars: ecological and socio-cultural. Achieving sustainable forest management will provide integrated benefits to all, ranging from safeguarding local livelihoods to protecting the biodiversity and ecosystems provided by forests, reducing rural poverty and mitigating some of the effects of climate change; the "Forest Principles" adopted at The United Nations Conference on Environment and Development in Rio de Janeiro in 1992 captured the general international understanding of sustainable forest management at that time. A number of sets of criteria and indicators have since been developed to evaluate the achievement of SFM at the global, regional and management unit level; these were all attempts to codify and provide for independent assessment of the degree to which the broader objectives of sustainable forest management are being achieved in practice.
In 2007, the United Nations General Assembly adopted the Non-Legally Binding Instrument on All Types of Forests. The instrument was the first of its kind, reflected the strong international commitment to promote implementation of sustainable forest management through a new approach that brings all stakeholders together. A definition of SFM was developed by the Ministerial Conference on the Protection of Forests in Europe, has since been adopted by the Food and Agriculture Organization, it defines sustainable forest management as: The stewardship and use of forests and forest lands in a way, at a rate, that maintains their biodiversity, regeneration capacity and their potential to fulfill, now and in the future, relevant ecological and social functions, at local and global levels, that does not cause damage to other ecosystems. In simpler terms, the concept can be described as the attainment of balance – balance between society's increasing demands for forest products and benefits, the preservation of forest health and diversity.
This balance is critical to the survival of forests, to the prosperity of forest-dependent communities. For forest managers, sustainably managing a particular forest tract means determining, in a tangible way, how to use it today to ensure similar benefits and productivity in the future. Forest managers must assess and integrate a wide array of sometimes conflicting factors – commercial and non-commercial values, environmental considerations, community needs global impact – to produce sound forest plans. In most cases, forest managers develop their forest plans in consultation with citizens, businesses and other interested parties in and around the forest tract being managed; the tools and visualization have been evolving for better management practices. The Food and Agriculture Organization of the United Nations, at the request of Member States and launched the Sustainable Forest Management Toolbox in 2014, an online collection of tools, best practices and examples of their application to support countries implementing sustainable forest management.
Because forests and societies are in constant flux, the desired outcome of sustainable forest management is not a fixed one. What constitutes a sustainably managed forest will change over time as values held by the public change. Criteria and indicators are tools which can be used to conceptualise and implement sustainable forest management. Criteria define and characterize the essential elements, as well as a set of conditions or processes, by which sustainable forest management may be assessed. Periodically measured indicators reveal the direction of change with respect to each criterion. Criteria and indicators of sustainable forest management are used and many countries produce national reports that assess their progress toward sustainable forest management. There are nine international and regional criteria and indicators initiatives, which collectively involve more than 150 countries. Three of the more advanced initiatives are those of the Working Group on Criteria and Indicators for the Conservation and Sustainable Management of Temperate and Boreal Forests, Forest Europe, the International Tropical Timber Organization.
Countries who are members of the same initiative agree to produce reports at the same time and using the same indicators. Within countries, at the management unit level, efforts have been directed at developing local level criteria and indicators of sustainable forest management; the Center for International Forestry Research, the International Model Forest Network and researchers at the University of British Columbia have developed a number of tools and techniques to help forest-dependent communities develop their own local level criteria and indicators. Criteria and Indicators form the basis of third-party forest certification programs such as the Canadian Standards Association's Sustainable Forest Management Standards and the Sustainable Forestry Initiative Standard. There appears to be growing international consensus on the key elements of sustainable forest management. Seven common thematic areas of sustainable forest management have emerged based on the criteria of the nine ongoing regional and international criteria and indicators initiatives.
The seven thematic areas are: Extent of forest resources Biological diversity Forest health and vitality Productive functions and forest resources Protective functions of forest resources Socio-economic functions Legal and institutional framework. This consensus on common thematic areas provides a common, implicit definition of sus
Soil is a mixture of organic matter, gases and organisms that together support life. Earth's body of soil, called the pedosphere, has four important functions: as a medium for plant growth as a means of water storage and purification as a modifier of Earth's atmosphere as a habitat for organismsAll of these functions, in their turn, modify the soil; the pedosphere interfaces with the lithosphere, the hydrosphere, the atmosphere, the biosphere. The term pedolith, used to refer to the soil, translates to ground stone in the sense "fundamental stone". Soil consists of a solid phase of minerals and organic matter, as well as a porous phase that holds gases and water. Accordingly, soil scientists can envisage soils as a three-state system of solids and gases. Soil is a product of several factors: the influence of climate, relief and the soil's parent materials interacting over time, it continually undergoes development by way of numerous physical and biological processes, which include weathering with associated erosion.
Given its complexity and strong internal connectedness, soil ecologists regard soil as an ecosystem. Most soils have a dry bulk density between 1.1 and 1.6 g/cm3, while the soil particle density is much higher, in the range of 2.6 to 2.7 g/cm3. Little of the soil of planet Earth is older than the Pleistocene and none is older than the Cenozoic, although fossilized soils are preserved from as far back as the Archean. Soil science has two basic branches of study: pedology. Edaphology studies the influence of soils on living things. Pedology focuses on the formation and classification of soils in their natural environment. In engineering terms, soil is included in the broader concept of regolith, which includes other loose material that lies above the bedrock, as can be found on the Moon and on other celestial objects as well. Soil is commonly referred to as earth or dirt. Soil is a major component of the Earth's ecosystem; the world's ecosystems are impacted in far-reaching ways by the processes carried out in the soil, from ozone depletion and global warming to rainforest destruction and water pollution.
With respect to Earth's carbon cycle, soil is an important carbon reservoir, it is one of the most reactive to human disturbance and climate change. As the planet warms, it has been predicted that soils will add carbon dioxide to the atmosphere due to increased biological activity at higher temperatures, a positive feedback; this prediction has, been questioned on consideration of more recent knowledge on soil carbon turnover. Soil acts as an engineering medium, a habitat for soil organisms, a recycling system for nutrients and organic wastes, a regulator of water quality, a modifier of atmospheric composition, a medium for plant growth, making it a critically important provider of ecosystem services. Since soil has a tremendous range of available niches and habitats, it contains most of the Earth's genetic diversity. A gram of soil can contain billions of organisms, belonging to thousands of species microbial and in the main still unexplored. Soil has a mean prokaryotic density of 108 organisms per gram, whereas the ocean has no more than 107 procaryotic organisms per milliliter of seawater.
Organic carbon held in soil is returned to the atmosphere through the process of respiration carried out by heterotrophic organisms, but a substantial part is retained in the soil in the form of soil organic matter. Since plant roots need oxygen, ventilation is an important characteristic of soil; this ventilation can be accomplished via networks of interconnected soil pores, which absorb and hold rainwater making it available for uptake by plants. Since plants require a nearly continuous supply of water, but most regions receive sporadic rainfall, the water-holding capacity of soils is vital for plant survival. Soils can remove impurities, kill disease agents, degrade contaminants, this latter property being called natural attenuation. Soils maintain a net absorption of oxygen and methane and undergo a net release of carbon dioxide and nitrous oxide. Soils offer plants physical support, water, temperature moderation and protection from toxins. Soils provide available nutrients to plants and animals by converting dead organic matter into various nutrient forms.
A typical soil is about 50% solids, 50% voids of which half is occupied by water and half by gas. The percent soil mineral and organic content can be treated as a constant, while the percent soil water and gas content is considered variable whereby a rise in one is balanced by a reduction in the other; the pore space allows for the infiltration and movement of air and water, both of which are critical for life existing in soil. Compaction, a common problem with soils, reduces this space, preventing air and water from reaching plant roots and soil organisms. Given sufficient time, an undifferentiated soil will evolve a soil profile which consists of two or more layers, referred to as soil horizons, that differ in one or more properties such as in their texture, density, consistency, temperature and reactivity; the horizons differ in thickness and gene
A national park is a park in use for conservation purposes. It is a reserve of natural, semi-natural, or developed land that a sovereign state declares or owns. Although individual nations designate their own national parks differently, there is a common idea: the conservation of'wild nature' for posterity and as a symbol of national pride. An international organization, the International Union for Conservation of Nature, its World Commission on Protected Areas, has defined "National Park" as its Category II type of protected areas. While this type of national park had been proposed the United States established the first "public park or pleasuring-ground for the benefit and enjoyment of the people", Yellowstone National Park, in 1872. Although Yellowstone was not termed a "national park" in its establishing law, it was always termed such in practice and is held to be the first and oldest national park in the world. However, the Tobago Main Ridge Forest Reserve, the area surrounding Bogd Khan Uul Mountain are seen as the oldest protected areas, predating Yellowstone by nearly a century.
The first area to use "national park" in its creation legislation was the U. S.'s Mackinac, in 1875. Australia's Royal National Park, established in 1879, was the world's third official national park. In 1895 ownership of Mackinac National Park was transferred to the State of Michigan as a state park and national park status was lost; as a result, Australia's Royal National Park is by some considerations the second oldest national park now in existence. Canada established Parks Canada in 1911, becoming the world's first national service dedicated to protecting and presenting natural and historical treasures; the largest national park in the world meeting the IUCN definition is the Northeast Greenland National Park, established in 1974. According to the IUCN, 6,555 national parks worldwide met its criteria in 2006. IUCN is still discussing the parameters of defining a national park. National parks are always open to visitors. Most national parks provide outdoor recreation and camping opportunities as well as classes designed to educate the public on the importance of conservation and the natural wonders of the land in which the national park is located.
In 1969, the IUCN declared a national park to be a large area with the following defining characteristics: One or several ecosystems not materially altered by human exploitation and occupation, where plant and animal species, geomorphological sites and habitats are of special scientific and recreational interest or which contain a natural landscape of great beauty. In 1971, these criteria were further expanded upon leading to more clear and defined benchmarks to evaluate a national park; these include: Minimum size of 1,000 hectares within zones in which protection of nature takes precedence Statutory legal protection Budget and staff sufficient to provide sufficient effective protection Prohibition of exploitation of natural resources qualified by such activities as sport, fishing, the need for management, etc. While the term national park is now defined by the IUCN, many protected areas in many countries are called national park when they correspond to other categories of the IUCN Protected Area Management Definition, for example: Swiss National Park, Switzerland: IUCN Ia - Strict Nature Reserve Everglades National Park, United States: IUCN Ib - Wilderness Area Victoria Falls National Park, Zimbabwe: IUCN III - National Monument Vitosha National Park, Bulgaria: IUCN IV - Habitat Management Area New Forest National Park, United Kingdom: IUCN V - Protected Landscape Etniko Ygrotopiko Parko Delta Evrou, Greece: IUCN VI - Managed Resource Protected AreaWhile national parks are understood to be administered by national governments, in Australia national parks are run by state governments and predate the Federation of Australia.
In Canada, there are both national parks operated by the federal government and provincial or territorial parks operated by the provincial and territorial governments, although nearly all are still national parks by the IUCN definition. In many countries, including Indonesia, the Netherlands, the United Kingdom, national parks do not adhere to the IUCN definition, while some areas which adhere to the IUCN definition are not designated as national parks. In 1810, the English poet William Wordsworth described the Lake District as a sort of national property, in which every man has a right and interest who has an eye to perceive and a heart to enjoy; the painter George Catlin, in his travels through the American West, wrote during the 1830s that the Native Americans in the United States might be preserved...in a magnificent park... A nation's Park, containing man and beast, in all the wild and freshness of their nature's beauty! The first effort by the U. S. Federal government to set aside such protected lands was on 20 April 1832, when President Andrew Jackson signed legislation that the 22nd United States Congress had enacted to set aside four sections of land around what is now Hot Springs, Arkansas, to protect the natural, thermal springs and adjoining mountainsides for the futur
A dehesa is a multifunctional, agrosylvopastoral system and cultural landscape of southern and central Spain and southern Portugal. Its name comes from the Latin'defensa', referring to land, fenced, destined for pasture. Dehesas may be communal property. Used for grazing, they produce a variety of products, including non-timber forest products such as wild game, honey and firewood, they are used to raise the Spanish fighting bull and the Iberian pig. The main tree component is oaks holm and cork. Other oaks, including melojo and quejigo, may be used to form dehesa, the species depending on geographical location and elevation. Dehesa is an anthropogenic system that provides not only a variety of foods, but wildlife habitat for endangered species such as the Spanish imperial eagle. By extension, the term can be used for this style of rangeland management on estates; the dehesa is derived from the Mediterranean forest ecosystem, consisting of grassland featuring herbaceous species, used for grazing cattle and sheep, tree species belonging to the genus Quercus, such as the holm oak, although other tree species such as beech and pine trees may be present.
Oaks are protected and pruned to produce acorns, which the famous black Iberian pigs feed on in the fall during the montanera. Ham produced from Iberian pigs fattened with acorns and air-dried at high elevations is known as Jamón ibérico, sells for premium prices if only acorns have been used for fattening. In a typical dehesa, oaks are managed to persist for about 250 years. If cork oaks are present, the cork is harvested about every 9 to 12 years, depending on the productivity of the site; the understory is cleared every 7 to 10 years to prevent the takeover of the woodland by shrubs of the rock rose family referred to as "jara", or by oak sprouts. Oaks are spaced to maximize overall productivity by balancing light for the grasses in the understory, water use in the soils, acorn production for pigs and game. There is debate about the origins and maintenance of the dehesa, whether or not the oaks can reproduce adequately under the grazing densities now prevailing; the dehesa system has great economic and social importance on the Iberian Peninsula because of both the large amount of land involved and its importance in maintaining rural population levels.
The major source of income for dehesa owners is cork, a sustainable product that supports this ancient production system and old growth oaks. High end black iberian pigs and sale of hunting rights represent significant income sources. Periodic hunts in the dehesa are known as the monteria. Groups attend a hunt at a private estate and wait at hunting spots for game to be driven to them with dogs, they pay well for the privilege, hunting wild boar, red deer and other species. The area of dehesa coincides with areas that could be termed "marginal" because of both their limited agricultural potential and a lack of local industry, which results in isolated agro-industries and low capitalization. Dehesa covers nearly 20,000 square kilometers on the Iberian Peninsula in: PortugalAlentejo The AlgarveSpainCórdoba Extremadura Salamanca Sierra Morena Sierra Norte de Sevilla Sierra de Aracena Cabañeros National Park List of types of formally designated forests Satoyama Silvopasture Wood pasture Fra. Paleo, Urbano..
"The dehesa/montado landscape". Pp. 149–151 in Sustainable Use of Biological Diversity in Socio-ecological Production Landscapes, eds. Bélair, C. Ichikawa, K. Wong, B. Y. L. and Mulongoy, K. J. Montreal: Secretariat of the Convention on Biological Diversity. Technical Series no. 52. Huntsinger, Lynn. "Oak woodland ranchers in California and Spain: Conservation and diversification". In Advances in Geoecology, ed. S. F. A. Schnabel. Joffre, R. "The dehesa system of southern Spain and Portugal as a natural ecosystem mimic," Journal of Agroforestry 45: 57-79. McGrath, Susan.. "Corkscrewed," Audubon magazine, January–February. Media related to Dehesas at Wikimedia Commons Plataforma integralDehesa - Página web de agentes del sector Proyecto Biodehesa Foro encinal Acción por la dehesa Dehesas ibéricas Observatorio de la dehesa y el montado
An epicormic shoot is a shoot growing from an epicormic bud, which lies underneath the bark of a trunk, stem, or branch of a plant. Epicormic buds lie dormant beneath the bark, their growth suppressed by hormones from active shoots higher up the plant. Under certain conditions, they develop into active shoots, such as when damage occurs to higher parts of the plant, or light levels are increased following removal of nearby plants. Epicormic buds and shoots occur in many woody species, but are absent from many others, such as most conifers. Human horticultural practices that exploit epicormic growth rely on plants that have epicormic budding capabilities for regenerative function in response to crown damage, such as through wind or fire. Epicormic shoots are the means by which trees regrow after coppicing or pollarding, where the tree's trunk or branches are cut back on a regular cycle; these forestry techniques cannot be used on species which do not possess strong epicormic growth abilities.
Pruning leads to growth of suppressed shoots below the cut – these may be from epicormic buds, but they may be other growth, such as normal buds or small shoots which are only suppressed. As one of their responses to frequent bushfires which would destroy most other plants, many Eucalypt trees found throughout Australia have extensive epicormic buds which sprout following a fire, allowing the vegetative regeneration of branches from their trunks; these epicormic buds are protected, set deeper beneath the thick bark than in other tree species, allowing both the buds and vascular cambium to be insulated from the intense heat. It should however be noted that not all eucalypt trees possess this means of vegetative recovery, the ability of a tree to survive and re-sprout depends on many factors, such as fire intensity, scorch height, tree height, species and size. Jarrah trees, found in the south-west of Western Australia, have epicormic buds which are activated after a bushfire or other extreme conditions.
The mediterranean Quercus suber resprouts from epicormic buds after fire. Dogwood trees – which are susceptible to a fungal infection known as dogwood anthracnose – will sometimes send out epicormic shoots when they are dying from the disease. Ash trees may develop epicormic shoots when infested by the emerald ash borer. Epicormic shoots can be used in mass propagation of oak trees; the long-lived Pseudotsuga menziesii forms epicormic shoots not in response to damage but as a means of forming growth on existing branches. The epicormic branching pattern has been observed to six iterations. Epicormic roots on a Norway Maple video Epicormic shoots on oak and larch
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals have mouthparts adapted to rasping or grinding. Horses and other herbivores have wide flat teeth that are adapted to grinding grass, tree bark, other tough plant material. A large percentage of herbivores have mutualistic gut flora that help them digest plant matter, more difficult to digest than animal prey; this flora is made up of cellulose-digesting bacteria. Herbivore is the anglicized form of a modern Latin coinage, cited in Charles Lyell's 1830 Principles of Geology. Richard Owen employed the anglicized term in an 1854 work on fossil skeletons. Herbivora is derived from the Latin herba meaning a small plant or herb, vora, from vorare, to eat or devour. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants and photosynthesizing bacteria.
More organisms that feed on autotrophs in general are known as primary consumers. Herbivory is limited to animals that eat plants. Fungi and protists that feed on living plants are termed plant pathogens, while fungi and microbes that feed on dead plants are described as saprotrophs. Flowering plants that obtain nutrition from other living plants are termed parasitic plants. There is, however, no single exclusive and definitive ecological classification of consumption patterns. In zoology, an herbivore is an animal, adapted to eat plant matter. Our understanding of herbivory in geological time comes from three sources: fossilized plants, which may preserve evidence of defence, or herbivory-related damage. Although herbivory was long thought to be a Mesozoic phenomenon, fossils have shown that within less than 20 million years after the first land plants evolved, plants were being consumed by arthropods. Insects fed on the spores of early Devonian plants, the Rhynie chert provides evidence that organisms fed on plants using a "pierce and suck" technique.
During the next 75 million years, plants evolved a range of more complex organs, such as roots and seeds. There is no evidence of any organism being fed upon until the middle-late Mississippian, 330.9 million years ago. There was a gap of 50 to 100 million years between the time each organ evolved and the time organisms evolved to feed upon them. Further than their arthropod status, the identity of these early herbivores is uncertain. Hole feeding and skeletonisation are recorded in the early Permian, with surface fluid feeding evolving by the end of that period. Herbivory among four-limbed terrestrial vertebrates, the tetrapods developed in the Late Carboniferous. Early tetrapods were large amphibious piscivores. While amphibians continued to feed on fish and insects, some reptiles began exploring two new food types and plants; the entire dinosaur order ornithischia was composed with herbivores dinosaurs. Carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation.
In contrast, a complex set of adaptations was necessary for feeding on fibrous plant materials. Arthropods evolved herbivory in four phases, changing their approach to it in response to changing plant communities. Tetrapod herbivores made their first appearance in the fossil record of their jaws near the Permio-Carboniferous boundary 300 million years ago; the earliest evidence of their herbivory has been attributed to dental occlusion, the process in which teeth from the upper jaw come in contact with teeth in the lower jaw is present. The evolution of dental occlusion led to a drastic increase in plant food processing and provides evidence about feeding strategies based on tooth wear patterns. Examination of phylogenetic frameworks of tooth and jaw morphologes has revealed that dental occlusion developed independently in several lineages tetrapod herbivores; this suggests that evolution and spread occurred within various lineages. Herbivores form an important link in the food chain because they consume plants in order to digest the carbohydrates photosynthetically produced by a plant.
Carnivores in turn consume herbivores for the same reason, while omnivores can obtain their nutrients from either plants or animals. Due to a herbivore's ability to survive on tough and fibrous plant matter, they are termed the primary consumers in the food cycle. Herbivory and omnivory can be regarded as special cases of Consumer-Resource Systems. Herbivores come in all sizes in the animal kingdom, they include aquatic and non-aquatic vertebrates. They can be large, like an elephant. Many herbivores found living in close proximity to humans, such as rodents, cows and camels. Two herbivore feeding strategies are browsing. For a terrestrial mammal to be called a grazer, at least 90% of the forage has to be grass, for a browser at least 90% tree leaves and/or twigs. An intermediate feeding strategy is called "mixed-feeding". In their daily need to take up energy from forage, herbivores of different body mass may be selective in choosing their food. "Selective" means that herbivores may choose their forage source depending on, e.g. season or food avail