Lumber
Lumber or timber is a type of wood, processed into beams and planks, a stage in the process of wood production. Lumber is used for structural purposes but has many other uses as well. There are two main types of lumber, it may be surfaced on one or more of its faces. Besides pulpwood, rough lumber is the raw material for furniture-making and other items requiring additional cutting and shaping, it is available in many species hardwoods. Finished lumber is supplied in standard sizes for the construction industry – softwood, from coniferous species, including pine and spruce, hemlock, but some hardwood, for high-grade flooring, it is more made from softwood than hardwoods, 80% of lumber comes from softwood. In the United States milled boards of wood are referred to as lumber. However, in Britain and other Commonwealth nations, the term timber is instead used to describe sawn wood products, like floor boards. In the United States and Canada timber describes standing or felled trees. In Canada, lumber describes cut and surfaced wood.
In the United Kingdom, the word lumber is used in relation to wood and has several other meanings, including unused or unwanted items. Referring to wood, Timber is universally used instead. Remanufactured lumber is the result of secondary or tertiary processing/cutting of milled lumber, it is lumber cut for industrial or wood-packaging use. Lumber is cut by ripsaw or resaw to create dimensions that are not processed by a primary sawmill. Resawing is the splitting of 1-inch through 12-inch hardwood or softwood lumber into two or more thinner pieces of full-length boards. For example, splitting a ten-foot 2×4 into two ten-foot 1×4s is considered resawing. Structural lumber may be produced from recycled plastic and new plastic stock, its introduction has been opposed by the forestry industry. Blending fiberglass in plastic lumber enhances its strength and fire resistance. Plastic fiberglass structural lumber can have a "class 1 flame spread rating of 25 or less, when tested in accordance with ASTM standard E 84," which means it burns slower than all treated wood lumber.
Logs are converted into timber by being hewn, or split. Sawing with a rip saw is the most common method, because sawing allows logs of lower quality, with irregular grain and large knots, to be used and is more economical. There are various types of sawing: Plain sawn – A log sawn through without adjusting the position of the log and the grain runs across the width of the boards. Quarter sawn and rift sawn – These terms have been confused in history but mean lumber sawn so the annual rings are reasonably perpendicular to the sides of the lumber. Boxed heart – The pith remains within the piece with some allowance for exposure. Heart center – the center core of a log. Free of heart center – A side-cut timber without any pith. Free of knots – No knots are present. Dimensional lumber is lumber, cut to standardized width and depth, specified in inches. Carpenters extensively use dimensional lumber in framing wooden buildings. Common sizes include 2×4, 2×6, 4×4; the length of a board is specified separately from the width and depth.
It is thus possible to find 2×4s that are four and twelve feet in length. In Canada and the United States, the standard lengths of lumber are 6, 8, 10, 12, 14, 16, 18, 20, 22 and 24 feet. For wall framing, "stud" or "precut" sizes are available, are used. For an eight-, nine-, or ten-foot ceiling height, studs are available in 92 5⁄8 inches, 104 5⁄8 inches, 116 5⁄8 inches; the term "stud" is used inconsistently to specify length. Under the prescription of the Method of Construction issued by the Southern Song government in the early 12th century, timbers were standardized to eight cross-sectional dimensions. Regardless of the actual dimensions of the timber, the ratio between width and height was maintained at 1:1.5. Units are in Song Dynasty inches. Timber smaller than the 8th class were called "unclassed"; the width of a timber is referred to as one "timber", the dimensions of other structural components were quoted in multiples of "timber". The dimensions of timbers in similar application show a gradual diminution from the Sui Dyansty to the modern era.
The length of a unit of dimensional lumber is limited by the height and girth of the tree it is milled from. In general the maximum length is 24 ft. Engineered wood products, manufactured by binding the strands, fibers, or veneers of wood, together with adhesives, to form composite materials, offer more flexibility and greater structural strength than typical wood building materials. Pre-cut studs save a framer much time, because they are pre-cut by the manufacturer for use in 8-, 9-
Temperature
Temperature is a physical quantity expressing hot and cold. It is measured with a thermometer calibrated in one or more temperature scales; the most used scales are the Celsius scale, Fahrenheit scale, Kelvin scale. The kelvin is the unit of temperature in the International System of Units, in which temperature is one of the seven fundamental base quantities; the Kelvin scale is used in science and technology. Theoretically, the coldest a system can be is when its temperature is absolute zero, at which point the thermal motion in matter would be zero. However, an actual physical system or object can never attain a temperature of absolute zero. Absolute zero is denoted as 0 K on the Kelvin scale, −273.15 °C on the Celsius scale, −459.67 °F on the Fahrenheit scale. For an ideal gas, temperature is proportional to the average kinetic energy of the random microscopic motions of the constituent microscopic particles. Temperature is important in all fields of natural science, including physics, Earth science and biology, as well as most aspects of daily life.
Many physical processes are affected by temperature, such as physical properties of materials including the phase, solubility, vapor pressure, electrical conductivity rate and extent to which chemical reactions occur the amount and properties of thermal radiation emitted from the surface of an object speed of sound is a function of the square root of the absolute temperature Temperature scales differ in two ways: the point chosen as zero degrees, the magnitudes of incremental units or degrees on the scale. The Celsius scale is used for common temperature measurements in most of the world, it is an empirical scale, developed by a historical progress, which led to its zero point 0 °C being defined by the freezing point of water, additional degrees defined so that 100 °C was the boiling point of water, both at sea-level atmospheric pressure. Because of the 100-degree interval, it was called a centigrade scale. Since the standardization of the kelvin in the International System of Units, it has subsequently been redefined in terms of the equivalent fixing points on the Kelvin scale, so that a temperature increment of one degree Celsius is the same as an increment of one kelvin, though they differ by an additive offset of 273.15.
The United States uses the Fahrenheit scale, on which water freezes at 32 °F and boils at 212 °F at sea-level atmospheric pressure. Many scientific measurements use the Kelvin temperature scale, named in honor of the Scots-Irish physicist who first defined it, it is a absolute temperature scale. Its zero point, 0 K, is defined to coincide with the coldest physically-possible temperature, its degrees are defined through thermodynamics. The temperature of absolute zero occurs at 0 K = −273.15 °C, the freezing point of water at sea-level atmospheric pressure occurs at 273.15 K = 0 °C. The International System of Units defines a scale and unit for the kelvin or thermodynamic temperature by using the reliably reproducible temperature of the triple point of water as a second reference point; the triple point is a singular state with its own unique and invariant temperature and pressure, along with, for a fixed mass of water in a vessel of fixed volume, an autonomically and stably self-determining partition into three mutually contacting phases, vapour and solid, dynamically depending only on the total internal energy of the mass of water.
For historical reasons, the triple point temperature of water is fixed at 273.16 units of the measurement increment. There is a variety of kinds of temperature scale, it may be convenient to classify them theoretically based. Empirical temperature scales are older, while theoretically based scales arose in the middle of the nineteenth century. Empirically based temperature scales rely directly on measurements of simple physical properties of materials. For example, the length of a column of mercury, confined in a glass-walled capillary tube, is dependent on temperature, is the basis of the useful mercury-in-glass thermometer; such scales are valid only within convenient ranges of temperature. For example, above the boiling point of mercury, a mercury-in-glass thermometer is impracticable. Most materials expand with temperature increase, but some materials, such as water, contract with temperature increase over some specific range, they are hardly useful as thermometric materials. A material is of no use as a thermometer near one of its phase-change temperatures, for example its boiling-point.
In spite of these restrictions, most used practical thermometers are of the empirically based kind. It was used for calorimetry, which contributed to the discovery of thermodynamics. Empirical thermometry has serious drawbacks when judged as a basis for theoretical physics. Empirically based thermometers, beyond their base as simple direct measurements of ordinary physical properties of thermometric materials, can be re-calibrated, by use of theoretical physical reasoning, this can extend their range of adequacy. Theoretically-based temperature scales are based directly on theoretical arguments those of thermodynamics, kinetic theory and quantum mechanics, they rely on theoretical properties of idealized materials. They are more or less comparable with feasible physical devices and materials. Theoretically based temperature scales are used to provide calibrating standards for practi
Canada
Canada is a country in the northern part of North America. Its ten provinces and three territories extend from the Atlantic to the Pacific and northward into the Arctic Ocean, covering 9.98 million square kilometres, making it the world's second-largest country by total area. Canada's southern border with the United States is the world's longest bi-national land border, its capital is Ottawa, its three largest metropolitan areas are Toronto and Vancouver. As a whole, Canada is sparsely populated, the majority of its land area being dominated by forest and tundra, its population is urbanized, with over 80 percent of its inhabitants concentrated in large and medium-sized cities, many near the southern border. Canada's climate varies across its vast area, ranging from arctic weather in the north, to hot summers in the southern regions, with four distinct seasons. Various indigenous peoples have inhabited what is now Canada for thousands of years prior to European colonization. Beginning in the 16th century and French expeditions explored, settled, along the Atlantic coast.
As a consequence of various armed conflicts, France ceded nearly all of its colonies in North America in 1763. In 1867, with the union of three British North American colonies through Confederation, Canada was formed as a federal dominion of four provinces; this began an accretion of provinces and territories and a process of increasing autonomy from the United Kingdom. This widening autonomy was highlighted by the Statute of Westminster of 1931 and culminated in the Canada Act of 1982, which severed the vestiges of legal dependence on the British parliament. Canada is a parliamentary democracy and a constitutional monarchy in the Westminster tradition, with Elizabeth II as its queen and a prime minister who serves as the chair of the federal cabinet and head of government; the country is a realm within the Commonwealth of Nations, a member of the Francophonie and bilingual at the federal level. It ranks among the highest in international measurements of government transparency, civil liberties, quality of life, economic freedom, education.
It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many other countries. Canada's long and complex relationship with the United States has had a significant impact on its economy and culture. A developed country, Canada has the sixteenth-highest nominal per capita income globally as well as the twelfth-highest ranking in the Human Development Index, its advanced economy is the tenth-largest in the world, relying chiefly upon its abundant natural resources and well-developed international trade networks. Canada is part of several major international and intergovernmental institutions or groupings including the United Nations, the North Atlantic Treaty Organization, the G7, the Group of Ten, the G20, the North American Free Trade Agreement and the Asia-Pacific Economic Cooperation forum. While a variety of theories have been postulated for the etymological origins of Canada, the name is now accepted as coming from the St. Lawrence Iroquoian word kanata, meaning "village" or "settlement".
In 1535, indigenous inhabitants of the present-day Quebec City region used the word to direct French explorer Jacques Cartier to the village of Stadacona. Cartier used the word Canada to refer not only to that particular village but to the entire area subject to Donnacona. From the 16th to the early 18th century "Canada" referred to the part of New France that lay along the Saint Lawrence River. In 1791, the area became two British colonies called Upper Canada and Lower Canada collectively named the Canadas. Upon Confederation in 1867, Canada was adopted as the legal name for the new country at the London Conference, the word Dominion was conferred as the country's title. By the 1950s, the term Dominion of Canada was no longer used by the United Kingdom, which considered Canada a "Realm of the Commonwealth"; the government of Louis St. Laurent ended the practice of using'Dominion' in the Statutes of Canada in 1951. In 1982, the passage of the Canada Act, bringing the Constitution of Canada under Canadian control, referred only to Canada, that year the name of the national holiday was changed from Dominion Day to Canada Day.
The term Dominion was used to distinguish the federal government from the provinces, though after the Second World War the term federal had replaced dominion. Indigenous peoples in present-day Canada include the First Nations, Métis, the last being a mixed-blood people who originated in the mid-17th century when First Nations and Inuit people married European settlers; the term "Aboriginal" as a collective noun is a specific term of art used in some legal documents, including the Constitution Act 1982. The first inhabitants of North America are hypothesized to have migrated from Siberia by way of the Bering land bridge and arrived at least 14,000 years ago; the Paleo-Indian archeological sites at Old Crow Flats and Bluefish Caves are two of the oldest sites of human habitation in Canada. The characteristics of Canadian indigenous societies included permanent settlements, complex societal hierarchies, trading networks; some of these cultures had collapsed by the time European explorers arrived in the late 15th and early 16th centuries and have only been discovered through archeological investigations.
The indigenous population at the time of the first European settlements is estimated to have been between 200,000
Northern California
Northern California is the northern portion of the U. S. state of California. Spanning the state's northernmost 48 counties its main population centers include the San Francisco Bay Area, the Greater Sacramento area, the Metropolitan Fresno area. Northern California contains redwood forests, along with the Sierra Nevada, including Yosemite Valley and part of Lake Tahoe, Mount Shasta, most of the Central Valley, one of the world's most productive agricultural regions; the 48-county definition is not used for the Northern California Megaregion, one of the 11 megaregions of the United States. The megaregion's area is instead defined from Metropolitan Fresno north to Greater Sacramento, from the Bay Area east across Nevada state line to encompass the entire Lake Tahoe-Reno area. Native Americans arrived in northern California at least as early as 8,000 to 5,000 BC and even much earlier, successive waves of arrivals led to one of the most densely populated areas of pre-Columbian North America; the arrival of European explorers from the early 16th to the mid-18th centuries did not establish European settlements in northern California.
In 1770, the Spanish mission at Monterey was the first European settlement in the area, followed by other missions along the coast—eventually extending as far north as Sonoma County. Northern California is not a formal geographic designation. California's north-south midway division is around 37° latitude, near the level of San Francisco. Popularly, though, "Northern California" refers to the state's northernmost 48 counties; because of California's large size and diverse geography, the state can be subdivided in other ways as well. For example, the Central Valley is a region, distinct both culturally and topographically from coastal California, though in northern versus southern California divisions, the Sacramento Valley and most of the San Joaquin Valley are placed in northern California; the state is considered as having an additional division north of the urban areas of the San Francisco Bay Area and Sacramento metropolitan areas. Extreme northern residents have felt under-represented in state government and in 1941 attempted to form a new state with southwestern Oregon to be called Jefferson, or more to introduce legislation to split California into two or three states.
The coastal area north of the Bay Area is referred to as the North Coast, while the interior region north of Sacramento is referred by locals as the Northstate. Northern California is the name of a proposed new state on the 2018 California ballot created by splitting the existing state into three parts. Since the events of the California Gold Rush, Northern California has been a leader on the world's economic and cultural stages. From the development of gold mining techniques and logging practices in the 19th century that were adopted around the world, to the development of world-famous and online business models, northern California has been at the forefront of new ways of doing business. In science, advances range from being the first to isolate and name fourteen transuranic chemical elements, to breakthroughs in microchip technology. Cultural contributions include the works of Ansel Adams, George Lucas, Clint Eastwood, as well as beatniks, the Summer of Love, the cradle of the international environmental movement, the open, casual workplace first popularized in the Silicon Valley dot-com boom and now in use around the world.
Other examples of innovation across diverse fields range from Genentech to CrossFit as a pioneer in extreme human fitness and training. It is home to one of the largest Air Force Bases on the West Coast, the largest of California, Travis Air Force Base. Northern California's largest metropolitan area is the San Francisco Bay Area which includes the cities of San Francisco, San Jose and their many suburbs. In recent years the Bay Area has drawn more commuters from as far as Central Valley cities such as Sacramento, Fresno and Modesto. With expanding development in all these areas, the San Francisco Bay Area, Monterey Bay Area, central part of the Central Valley and Sierra Nevada foothills may now be viewed as part of a single megalopolis; the 2010 U. S. Census showed that the Bay Area grew at a faster rate than the Greater Los Angeles Area while Greater Sacramento had the largest growth rate of any metropolitan area in California; the state's larger inland cities are considered part of Northern California in cases when the state is divided into two parts.
Important cities in the region not in major metropolitan areas include Eureka on the far North Coast, Redding, at the northern end of the Central Valley and Yuba City in the mid-north of the Valley, as well as Fresno and Visalia on the southern end. Though smaller in every case except for Fresno than the larger cities of the vast region, these smaller regional centers are of historical, inflated economic importance for their respective size, due to their locations, which are rural or otherwise isolated. Inhabited for millennia by Native Americans, from the Shasta tribe in the north, to the Miwoks in the central coast and Sierra Nevada, to the Yokuts of the southern Central Valley, northern California was among the most densely populated areas of pre-Columbian North America; the first European to explore the coast was Juan Rodríguez Cabrillo, sailing for the Spanish
Sonoma County, California
Sonoma County is a county in the U. S. state of California. As of the 2010 United States Census, its population was 483,878, its county seat and largest city is Santa Rosa. It is to the south of Mendocino County, it is west of Lake County. Sonoma County comprises the Santa Rosa, CA Metropolitan Statistical Area, included in the San Jose-San Francisco-Oakland, CA Combined Statistical Area, it is the northwesternmost county in the nine-county San Francisco Bay Area region. Sonoma is the southwestern county and largest producer of California’s Wine Country region, which includes Napa and Lake counties, it possesses thirteen approved over 250 wineries. In 2002, Sonoma County ranked as the 32nd county in the United States in agricultural production; as early as 1920, Sonoma County was ranked as the eighth most agriculturally productive US county and a leading producer of hops, prunes and dairy and poultry products due to the extent of available, fertile agricultural land in addition to the abundance of high quality irrigation water.
More than 7.4 million tourists visit each year, spending more than $1 billion in 2006. Sonoma County is the home of Santa Rosa Junior College. Sonoma County is home to several Native American tribes. By the 1830s, European settlement had set a new direction that would prove to radically alter the course of land use and resource management of this region. Sonoma County has rich agricultural land, albeit divided between two nearly monocultural uses as of 2007: grapes and pasturage; the voters have twice approved open space initiatives that have provided funding for public acquisition of natural areas, preserving forested areas, coastal habitat, other open space. The Pomo, Coast Miwok and Wappo peoples were the earliest human settlers of Sonoma County, between 8000 and 5000 BC living within the natural carrying capacity of the land. Archaeological evidence of these First people includes a number of occurrences of rock carvings in southern Sonoma County. Spaniards and other Europeans claimed and settled in the county from the late 16th to mid-19th century, seeking timber and farmland.
The Russians were the first newcomers to establish a permanent foothold in Sonoma County, with the Russian-American Company establishing Fort Ross on the Sonoma Coast in 1812. This settlement and its outlying Russian settlements came to include a population of several hundred Russian and Aleut settlers and a stockaded fort with artillery. However, the Russians abandoned it in 1841 and sold the fort to John Sutter and Mexican land grantee of Sacramento; the Mission San Francisco Solano, founded in 1823 as the last and northernmost of 21 California missions, is in the present City of Sonoma, at the northern end of El Camino Real. El Presidio de Sonoma, or Sonoma Barracks, was established in 1836 by Comandante General Mariano Guadalupe Vallejo, his duties included keeping an eye on the Russian traders at Fort Ross, secularizing the Mission, maintaining cooperation with the Native Americans of the entire region, doling out the lands for large estates and ranches. The City of Sonoma was the site of the Bear Flag Revolt in 1846.
Sonoma was one of the original counties formed when California became a state in 1850, with its county seat the town of Sonoma. However, by the early 1850s, Sonoma had declined in importance in both commerce and population, its county buildings were crumbling, it was remote; as a result, elements in the newer growing towns of Petaluma, Santa Rosa, Healdsburg began vying to move the county seat to their towns. The dispute was between the bigger, richer commercial town of Petaluma and the more centrally located, growing agricultural center of Santa Rosa; the fate was decided following an election for the state legislature in which James Bennett of Santa Rosa defeated Joseph Hooker of Sonoma and introduced a bill that resulted in Santa Rosa being confirmed as county seat in 1854. Several Santa Rosans, not caring to wait, decided to take action and, one night, rode down the Sonoma Valley to Sonoma, took the county seals and records, brought them to Santa Rosa; some of the county's land was annexed from Mendocino County between 1850 and 1860.
Early post-1847 settlement and development focused on the city of Sonoma the region's sole town and a common transit and resting point in overland travel between the region and Sacramento and the gold fields to the east. However, after 1850, a settlement that soon became the city of Petaluma began to grow near the farthest navigable point inland up the Petaluma River. A hunting camp used to obtain game to sell in other markets, by 1854 Petaluma had grown into a bustling center of trade, taking advantage of its position in the river near a region of productive agricultural land, being settled. Soon, other inland towns, notably Santa Rosa and Healdsburg began to develop due to their locations along riparian areas in prime agricultural flatland. However, their development lagged behind Petaluma which, until the arrival of railroads in the 1860s, remained the primary commercial and break-of-bulk point for people and goods in the region. After the arrival of the San Francisco and North Pacific Railroad in 1870, Santa Rosa began to boom, soon equalling and surpassing Petaluma as the region's population and commercial center.
The railroad bypassed Petaluma for southern connections to ferries of San Francisco Bay. Six nations have claimed Sonoma County fro
Pinaceae
The Pinaceae are trees or shrubs, including many of the well-known conifers of commercial importance such as cedars, hemlocks, larches and spruces. The family is included in the order Pinales known as Coniferales. Pinaceae are supported as monophyletic by their protein-type sieve cell plastids, pattern of proembryogeny, lack of bioflavonoids, they are the largest extant conifer family in species diversity, with between 220 and 250 species in 11 genera, the second-largest in geographical range, found in most of the Northern Hemisphere, with the majority of the species in temperate climates, but ranging from subarctic to tropical. The family forms the dominant component of boreal and montane forests. One species, Pinus merkusii, grows just south of the equator in Southeast Asia. Major centres of diversity are found in the mountains of southwest China, central Japan, California. Members of the family Pinaceae are trees growing from 2 to 100 m tall evergreen, monoecious, with subopposite or whorled branches, spirally arranged, linear leaves.
The embryos of Pinaceae have three to 24 cotyledons. The female cones are large and woody, 2–60 cm long, with numerous spirally arranged scales, two winged seeds on each scale; the male cones are small, 0.5–6.0 cm long, fall soon after pollination. Seed dispersal is by wind, but some species have large seeds with reduced wings, are dispersed by birds. Analysis of Pinaceae cones reveals how selective pressure has shaped the evolution of variable cone size and function throughout the family. Variation in cone size in the family has resulted from the variation of seed dispersal mechanisms available in their environments over time. All Pinaceae with seeds weighing less than 90 mg are adapted for wind dispersal. Pines having seeds larger than 100 mg are more to have benefited from adaptations that promote animal dispersal by birds. Pinaceae that persist in areas where tree squirrels are abundant do not seem to have evolved adaptations for bird dispersal. Boreal conifers have many adaptions for winter.
The narrow conical shape of northern conifers, their downward-drooping limbs help them shed snow, many of them seasonally alter their biochemistry to make them more resistant to freezing, called "hardening". Classification of the subfamilies and genera of Pinaceae has been subject to debate in the past. Pinaceae ecology and history have all been used as the basis for methods of analyses of the family. An 1891 publication divided the family into two subfamilies, using the number and position of resin canals in the primary vascular region of the young taproot as the primary consideration. In a 1910 publication, the family was divided into two tribes based on the occurrence and type of long–short shoot dimorphism. A more recent classification divided the subfamilies and genera based on the consideration of features of ovulate cone anatomy among extant and fossil members of the family. Below is an example of; the 11 genera are grouped into four subfamilies, based on the microscopical anatomy and the morphology of the cones, wood and leaves: Subfamily Pinoideae: cones are biennial triennial, with each year's scale-growth distinct, forming an umbo on each scale, the cone scale base is broad, concealing the seeds from abaxial view, the seed is without resin vesicles, the seed wing holds the seed in a pair of claws, leaves have primary stomatal bands adaxial or on both surfaces.
Subfamily Piceoideae: cones are annual, without a distinct umbo, the cone scale base is broad, concealing the seeds from abaxial view, seed is without resin vesicles, the seed wing holds the seed loosely in a cup, leaves have primary stomatal bands adaxial or on both surfaces. Subfamily Laricoideae: cones are annual, without a distinct umbo, the cone scale base is broad, concealing the seeds from abaxial view, the seed is without resin vesicles, the seed wing holds the seed in a cup, leaves have primary stomatal bands abaxial only. Subfamily Abietoideae: cones are annual, without a distinct umbo, the cone scale base is narrow, with the seeds visible in abaxial view, the seed has resin vesicles, the seed wing holds the seed in a cup, leaves have primary stomatal bands abaxial only. External stresses on plants have the ability to change the structure and composition of forest ecosystems. Common external stress that Pinaceae experience are herbivore and pathogen attack which leads to tree death.
In order to combat these stresses, trees need to evolve defenses against these stresses. Pinaceae have evolved a myriad of mechanical and chemical defenses, or a combination of the two, in order to protect themselves against antagonists. Pinaceae have the ability to up-regulate a combination of constitutive mechanical and chemical strategies to further their defenses. Pinaceae defenses are prevalent in the bark of the trees; this part of the tree contributes a complex defensive boundary against external antagonists. Constitutive and induced defenses are both found in the bark. Constitutive defenses are the first line of defenses used against antagonists and can include sclerified cells, lignified periderm cells, secondary compounds such as phenolics and resins
Pinophyta
The Pinophyta known as Coniferophyta or Coniferae, or as conifers, are a division of vascular land plants containing a single extant class, Pinopsida. They are gymnosperms, cone-bearing seed plants. All extant conifers are perennial woody plants with secondary growth; the great majority are trees. Examples include cedars, Douglas firs, firs, kauri, pines, redwoods and yews; as of 1998, the division Pinophyta was estimated to contain eight families, 68 genera, 629 living species. Although the total number of species is small, conifers are ecologically important, they are the dominant plants over large areas of land, most notably the taiga of the Northern Hemisphere, but in similar cool climates in mountains further south. Boreal conifers have many wintertime adaptations; the narrow conical shape of northern conifers, their downward-drooping limbs, help them shed snow. Many of them seasonally alter their biochemistry to make them more resistant to freezing. While tropical rainforests have more biodiversity and turnover, the immense conifer forests of the world represent the largest terrestrial carbon sink.
Conifers are of great economic value for softwood paper production. The earliest conifers in the fossil record date to the late Carboniferous period arising from Cordaites, a genus of seed-bearing Gondwanan plants with cone-like fertile structures. Pinophytes and Ginkgophytes all developed at this time. An important adaptation of these gymnosperms was allowing plants to live without being so dependent on water. Other adaptations are pollen and the seed, which allows the embryo to be transported and developed elsewhere. Conifers appear to be one of the taxa that benefited from the Permian–Triassic extinction event, were the dominant land plants of the Mesozoic, they were overtaken by the flowering plants, which first appeared in the Cretaceous, became dominant in the Cenozoic era. They were the main food of herbivorous dinosaurs, their resins and poisons would have given protection against herbivores. Reproductive features of modern conifers had evolved by the end of the Mesozoic era. Conifer is a Latin word, a compound of conus and ferre, meaning "the one that bears cone".
The division name Pinophyta conforms to the rules of the International Code of Nomenclature for algae and plants, which state that the names of higher taxa in plants are either formed from the name of an included family, in this case Pinaceae, or are descriptive. A descriptive name in widespread use for the conifers is Coniferae. According to the ICN, it is possible to use a name formed by replacing the termination -aceae in the name of an included family, in this case preferably Pinaceae, by the appropriate termination, in the case of this division ‑ophyta. Alternatively, "descriptive botanical names" may be used at any rank above family. Both are allowed; this means that if conifers are considered a division, they may be called Coniferae. As a class they may be called Coniferae; as an order they may be called Coniferae or Coniferales. Conifers are the largest and economically most important component group of the gymnosperms, but they comprise only one of the four groups; the division Pinophyta consists of just one class, which includes both living and fossil taxa.
Subdivision of the living conifers into two or more orders has been proposed from time to time. The most seen in the past was a split into two orders and Pinales, but recent research into DNA sequences suggests that this interpretation leaves the Pinales without Taxales as paraphyletic, the latter order is no longer considered distinct. A more accurate subdivision would be to split the class into three orders, Pinales containing only Pinaceae, Araucariales containing Araucariaceae and Podocarpaceae, Cupressales containing the remaining families, but there has not been any significant support for such a split, with the majority of opinion preferring retention of all the families within a single order Pinales, despite their antiquity and diverse morphology; the conifers are now accepted as comprising seven families, with a total of 65–70 genera and 600–630 species. The seven most distinct families are linked in the box above right and phylogenetic diagram left. In other interpretations, the Cephalotaxaceae may be better included within the Taxaceae, some authors additionally recognize Phyllocladaceae as distinct from Podocarpaceae.
The family Taxodiaceae is here included in family Cupressaceae, but was recognized in the past and can still be found in many field guides. A new classification and linear sequence based on molecular data can be found in an article by Christenhusz et al; the conifers are an ancient group, with a fossil record extending back about 300 million years to the Paleozoic in the late Carboniferous period. Other classes and orders, now long extinct occur as fossils from the late Paleozoic and Mesozoic eras. Fossil conifers included many diverse forms, the most distinct from modern conifers being some herbaceous conifers with no woody stems. Major fossil orders of conifers or conifer-like plants include the Cordaitales, Vojnovskyales and also the Czekanowskiales (possibly
