Robert Brown (botanist, born 1773)
Robert Brown FRSE FRS FLS MWS was a Scottish botanist and palaeobotanist who made important contributions to botany through his pioneering use of the microscope. His contributions include one of the earliest detailed descriptions of the cell nucleus and cytoplasmic streaming, he made numerous contributions to plant taxonomy, notably erecting a number of plant families that are still accepted today. Brown was born in Montrose on 21 December 1773, he was the son of James Brown, a minister in the Scottish Episcopal Church with Jacobite convictions so strong that in 1788 he defied his church's decision to give allegiance to George III. His mother was the daughter of a Presbyterian minister; as a child Brown attended the local Grammar School Marischal College at Aberdeen, but withdrew in his fourth year when the family moved to Edinburgh in 1790. His father died late the following year. Brown enrolled to study medicine at the University of Edinburgh, but developed an interest in botany, ended up spending more of his time on the latter than the former.
He attended the lectures of John Walker. He began corresponding with and collecting for William Withering, one of the foremost British botanists of his day. Highlights for Brown during this period include his discovery of a new species of grass, Alopecurus alpinus. Brown dropped out of his medical course in 1793. Late in 1794, he enlisted in the Fifeshire Fencibles, his regiment was posted to Ireland shortly after. In June 1795 he was appointed Surgeon's Mate, his regiment saw little action, however, he had a good deal of leisure time all of which he spent on botany. He was frustrated by his itinerant lifestyle, which prevented him from building his personal library and specimen collection as he would have liked, cut him off from the most important herbaria and libraries. During this period Brown was interested in cryptogams, these would be the subject of Brown's first, albeit unattributed, publication. Brown began a correspondence with James Dickson, by 1796 was sending him specimens and descriptions of mosses.
Dickson incorporated Brown's descriptions into his Fasciculi plantarum cryptogamicarum britanniae, with Brown's permission but without any attribution. By 1800, Brown was established amongst Irish botanists, was corresponding with a number of British and foreign botanists, including Withering, James Edward Smith and José Correia da Serra, he had been nominated to the Linnean Society of London. He had begun experimenting with microscopy. However, as an army surgeon stationed in Ireland there seemed little prospect of him attracting the notice of those who could offer him a career in botany. In 1798, Brown heard that Mungo Park had withdrawn from a proposed expedition into the interior of New Holland, leaving a vacancy for a naturalist. At Brown's request, Correia wrote to Sir Joseph Banks, suggesting Brown as a suitable replacement: Science is the gainer in this change of man, he is a Scotchman, fit to pursue an object with cold mind. He was not selected, the expedition did not end up going ahead as proposed, though George Caley was sent to New South Wales as a botanical collector for Banks.
In 1800, Matthew Flinders put to Banks a proposal for an expedition that would answer the question whether New Holland was one island or several. Banks approved Flinders' proposal, in December 1800 wrote to Brown offering him the position of naturalist to the expedition. Brown accepted immediately. Brown was told to expect to sail at the end of 1800, only a few weeks after being offered the position. A succession of delays meant the voyage did not get under way until July 1801. Brown spent much of the meantime preparing for the voyage by studying Banks' Australian plant specimens and copying out notes and descriptions for use on the voyage. Though Brown's brief was collect scientific specimens of all sorts, he was told to give priority to plants and birds, to treat other fields, such as geology, as secondary pursuits. In addition to Brown, the scientific staff comprised the renowned botanical illustrator Ferdinand Bauer. Brown was given authority over Bauer and Good, both of whom were instructed to give any specimens they might collect to Brown, rather than forming separate collections.
Both men would provide enthusiastic and hard-working companions for Brown, thus Brown's specimen collections contain material colle
A forest is a large area dominated by trees. Hundreds of more precise definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing and ecological function. According to the used Food and Agriculture Organization definition, forests covered 4 billion hectares or 30 percent of the world's land area in 2006. Forests are the dominant terrestrial ecosystem of Earth, are distributed around the globe. Forests account for 75% of the gross primary production of the Earth's biosphere, contain 80% of the Earth's plant biomass. Net primary production is estimated at 21.9 gigatonnes carbon per year for tropical forests, 8.1 for temperate forests, 2.6 for boreal forests. Forests at different latitudes and elevations form distinctly different ecozones: boreal forests near the poles, tropical forests near the equator and temperate forests at mid-latitudes. Higher elevation areas tend to support forests similar to those at higher latitudes, amount of precipitation affects forest composition.
Human society and forests influence each other in both negative ways. Forests serve as tourist attractions. Forests can affect people's health. Human activities, including harvesting forest resources, can negatively affect forest ecosystems. Although forest is a term of common parlance, there is no universally recognised precise definition, with more than 800 definitions of forest used around the world. Although a forest is defined by the presence of trees, under many definitions an area lacking trees may still be considered a forest if it grew trees in the past, will grow trees in the future, or was designated as a forest regardless of vegetation type. There are three broad categories of forest definitions in use: administrative, land use, land cover. Administrative definitions are based upon the legal designations of land, bear little relationship to the vegetation growing on the land: land, designated as a forest is defined as a forest if no trees are growing on it. Land use definitions are based upon the primary purpose.
For example, a forest may be defined as any land, used for production of timber. Under such a land use definition, cleared roads or infrastructure within an area used for forestry, or areas within the region that have been cleared by harvesting, disease or fire are still considered forests if they contain no trees. Land cover definitions define forests based upon the type and density of vegetation growing on the land; such definitions define a forest as an area growing trees above some threshold. These thresholds are the number of trees per area, the area of ground under the tree canopy or the section of land, occupied by the cross-section of tree trunks. Under such land cover definitions, an area of land can only be known as forest if it is growing trees. Areas that fail to meet the land cover definition may be still included under while immature trees are establishing if they are expected to meet the definition at maturity. Under land use definitions, there is considerable variation on where the cutoff points are between a forest and savanna.
Under some definitions, forests require high levels of tree canopy cover, from 60% to 100%, excluding savannas and woodlands in which trees have a lower canopy cover. Other definitions consider savannas to be a type of forest, include all areas with tree canopies over 10%; some areas covered in trees are defined as agricultural areas, e.g. Norway spruce plantations in Austrian forest law when the trees are being grown as Christmas trees and below a certain height; the word forest comes from Middle English, from Old French forest "forest, vast expanse covered by trees". A borrowing of the Medieval Latin word foresta "open wood", foresta was first used by Carolingian scribes in the Capitularies of Charlemagne to refer to the king's royal hunting grounds; the term was not endemic to Romance languages. The exact origin of Medieval Latin foresta is obscure; some authorities claim the word derives from the Late Latin phrase forestam silvam, meaning "the outer wood". Frankish *forhist is attested by Old High German forst "forest", Middle Low German vorst "forest", Old English fyrhþ "forest, game preserve, hunting ground", Old Norse fýri "coniferous forest", all of which derive from Proto-Germanic *furhísa-, *furhíþija- "a fir-wood, coniferous forest", from Proto-Indo-European *perkwu- "a coniferous or mountain forest, wooded height".
Uses of the word "forest" in English to denote any uninhabited area of non-enclosure are now considered archaic. The word was introduced by the Norman rulers of England as a legal term denoting an uncultivated area set aside for hunting by feudal nobility; these hunting forests were not neces
Sierra Nevada (U.S.)
The Sierra Nevada is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies in Nevada; the Sierra Nevada is part of the American Cordillera, a chain of mountain ranges that consists of an continuous sequence of such ranges that form the western "backbone" of North America, Central America, South America and Antarctica. The Sierra runs 400 miles north-to-south, is 70 miles across east-to-west. Notable Sierra features include the largest alpine lake in North America; the Sierra is home to three national parks, twenty wilderness areas, two national monuments. These areas include Yosemite and Kings Canyon National Parks; the character of the range is shaped by its ecology. More than one hundred million years ago during the Nevadan orogeny, granite formed deep underground; the range started to uplift four million years ago, erosion by glaciers exposed the granite and formed the light-colored mountains and cliffs that make up the range.
The uplift caused a wide range of elevations and climates in the Sierra Nevada, which are reflected by the presence of five life zones. Uplift continues due to faulting caused by tectonic forces, creating spectacular fault block escarpments along the eastern edge of the southern Sierra; the Sierra Nevada has a significant history. The California Gold Rush occurred in the western foothills from 1848 through 1855. Due to inaccessibility, the range was not explored until 1912; the Sierra Nevada lies in Central and Eastern California, with a small but important spur extending into Nevada. West-to-east, the Sierra Nevada's elevation increases from 1,000 feet in the Central Valley to heights of about 14,000 feet at its crest 50–75 miles to the east; the east slope forms the steep Sierra Escarpment. Unlike its surroundings, the range receives a substantial amount of snowfall and precipitation due to orographic lift; the Sierra Nevada's irregular northern boundary stretches from the Susan River and Fredonyer Pass to the North Fork Feather River.
It represents where the granitic bedrock of the Sierra Nevada dives below the southern extent of Cenozoic igneous surface rock from the Cascade Range. It is bounded on the west by California's Central Valley and on the east by the Basin and Range Province; the southern boundary is at Tehachapi Pass. Physiographically, the Sierra is a section of the Cascade-Sierra Mountains province, which in turn is part of the larger Pacific Mountain System physiographic division; the California Geological Survey states that "the northern Sierra boundary is marked where bedrock disappears under the Cenozoic volcanic cover of the Cascade Range." The range is drained on its western slope by the Central Valley watershed, which discharges into the Pacific Ocean at San Francisco. The northern third of the western Sierra is part of the Sacramento River watershed, the middle third is drained by the San Joaquin River; the southern third of the range is drained by the Kings, Kaweah and Kern rivers, which flow into the endorheic basin of Tulare Lake, which overflows into the San Joaquin during wet years.
The eastern slope watershed of the Sierra is much narrower. From north to south, the Susan River flows into intermittent Honey Lake, the Truckee River flows from Lake Tahoe into Pyramid Lake, the Carson River runs into Carson Sink, the Walker River into Walker Lake. Although none of the eastern rivers reach the sea, many of the streams from Mono Lake southwards are diverted into the Los Angeles Aqueduct which provides water to Southern California; the height of the mountains in the Sierra Nevada increases from north to south. Between Fredonyer Pass and Lake Tahoe, the peaks range from 5,000 feet to more than 9,000 feet; the crest near Lake Tahoe is 9,000 feet high, with several peaks approaching the height of Freel Peak. Farther south, the highest peak in Yosemite National Park is Mount Lyell; the Sierra rises to 14,000 feet with Mount Humphreys near Bishop, California. Near Lone Pine, Mount Whitney is at 14,505 feet, the highest point in the contiguous United States. South of Mount Whitney, the elevation of the range dwindles.
The crest elevation is 10,000 feet near Lake Isabella, but south of the lake, the peaks reach to only a modest 8,000 feet. There are several notable geographical features in the Sierra Nevada: Lake Tahoe is a large, clear freshwater lake in the northern Sierra Nevada, with an elevation of 6,225 ft and an area of 191 sq mi. Lake Tahoe lies between a spur of the Sierra. Hetch Hetchy Valley, Yosemite Valley, Kings Canyon, Kern Canyon are examples of many glacially-scoured canyons on the west side of the Sierra. Yosemite National Park is filled with notable features such as waterfalls, granite domes, high mountains and meadows. Groves of Giant Sequoia
Quercus agrifolia, the California live oak or coast live oak, is a variable shrubby evergreen oak tree, a type of live oak, native to the California Floristic Province. It grows west of the Sierra Nevada mountain range from Mendocino County, south to northern Baja California in Mexico, it is classified in the red oak section of oaks. This species is sympatric with canyon live oak, the two may be hard to distinguish because their spinose leaves are superficially similar. Coast live oak has a much-branched trunk and reaches a mature height of 10–25 meters; some specimens may attain an age exceeding 250 years, with trunk diameters up to three or four meters, such as those on the Filoli estate in San Mateo County. The trunk for older individuals, may be contorted and gnarled; the crown is broadly rounded and dense when aged 20 to 70 years. The leaves are dark green, oval convex in shape, 2–7 cm long and 1–4 cm broad; the outer layers of leaves are designed for maximum solar absorption, containing two to three layers of photosynthetic cells.
These outer leaves are deemed to be small in size to more efficiently re-radiate the heat gained from solar capture. Shaded leaves are broader and thinner, having only a single layer of photosynthetic cells; the convex leaf shape may be useful for interior leaves which depend on capturing reflected light scattered in random directions from the outer canopy. The flowers are produced in early-to-mid spring; the fruit is a slender reddish brown acorn 2–3.5 cm long and 1–1.5 cm broad, with the basal quarter enclosed in a cupule. There are two varieties of Quercus agrifolia: Quercus agrifolia var. agrifolia. Throughout the range of the species. Leaves that are glabrous to hairy on the abaxial side near the leaf vein axils. Hybrids with Q. kelloggii, Q. parvula var. shevei, Q. wislizenii are known. Quercus agrifolia var. oxyadenia. Southwesternmost California, Baja California. Leaves that are tomentose abaxially, with densely interwoven hairs, it prefers granitic soils. Several hybrids between coast live.
Hybrids with interior live oak are known in many areas in northern California. Coast live oak hybridizes with Shreve oak. All these oak species show evidence of introgression with one another. In naming the species, Née compared it to a species illustrated in Leonard Plukenet’s Phytographia under the descriptive name “Ilex folio agrifolii americana, forte agria, vel aquifolia glandifera” which Plukenet had compared, in his Almagestum botanicum, to Luigi Anguillara’s “Agrifolia glandifera,” the noun “Agrifolia” being a Medieval Latin form of “Aquifolium” meaning a holly or holly-leaved oak, related to the Modern Italian “Agrifoglio,” meaning “holly.” Coast live oak is the only California native oak that thrives in the coastal environment, although it is rare on the immediate shore. The coastal fog supplies relief from the rainless California summer heat, it is the dominant overstory plant of the coast live oak woodland habitat joined by California bay laurel and California buckeye north of Big Sur.
Associated understory plants include various manzanitas and western poison-oak. The tree is found on well drained soils of coastal hills and plains near year round or perennial streams, it may be found in several natural communities including coast live oak woodland, Engelmann oak woodland, valley oak woodland and both northern and southern mixed evergreen forests. While found within 100 kilometers of the Pacific Ocean at elevations less than 700 meters, in southern California it occurs at up to 1,500 meters in altitude; the California oak moth caterpillar subsists on living and fallen leaves of the Coast Live Oak. In 8–10 year cycles, the caterpillar will appear in sufficient abundance to denude healthy trees; the trees recover, botanists speculate that the species provide mutual benefit in the form of fertilizer for the oak. The coast live oak is the only known foodplant of Chionodes vanduzeei caterpillars. Coastal live. Pollination: Occurs in following seasons depending on latitude and elevation: Spring.
At least twelve distinct cultures of Native Americans are known to have consumed the acorns as a dietary staple. In the 18th century Spaniards in the San Fernando Valley used the wood for charcoal to fire kilns in making adobe; this form of charcoal would be utilized in the baking and electric power industries. In the 18th and 19th centuries shipbuilders sought out the odd angular branches to make special joints. Pioneers moving west would harvest small amounts for making farm implements and wagon wheels, but the greatest impact was the wholesale clearing of oak woodlands to erect sprawling cities such as San Diego and San Francisco; the irregular s
An acid is a molecule or ion capable of donating a hydron, or, capable of forming a covalent bond with an electron pair. The first category of acids is the proton donors or Brønsted acids. In the special case of aqueous solutions, proton donors form the hydronium ion H3O+ and are known as Arrhenius acids. Brønsted and Lowry generalized the Arrhenius theory to include non-aqueous solvents. A Brønsted or Arrhenius acid contains a hydrogen atom bonded to a chemical structure, still energetically favorable after loss of H+. Aqueous Arrhenius acids have characteristic properties which provide a practical description of an acid. Acids form aqueous solutions with a sour taste, can turn blue litmus red, react with bases and certain metals to form salts; the word acid is derived from the Latin acidus/acēre meaning sour. An aqueous solution of an acid has a pH less than 7 and is colloquially referred to as'acid', while the strict definition refers only to the solute. A lower pH means a higher acidity, thus a higher concentration of positive hydrogen ions in the solution.
Chemicals or substances having the property of an acid are said to be acidic. Common aqueous acids include hydrochloric acid, acetic acid, sulfuric acid, citric acid; as these examples show, acids can be solutions or pure substances, can be derived from acids that are solids, liquids, or gases. Strong acids and some concentrated weak acids are corrosive, but there are exceptions such as carboranes and boric acid; the second category of acids are Lewis acids. An example is boron trifluoride, whose boron atom has a vacant orbital which can form a covalent bond by sharing a lone pair of electrons on an atom in a base, for example the nitrogen atom in ammonia. Lewis considered this as a generalization of the Brønsted definition, so that an acid is a chemical species that accepts electron pairs either directly or by releasing protons into the solution, which accept electron pairs. However, hydrogen chloride, acetic acid, most other Brønsted-Lowry acids cannot form a covalent bond with an electron pair and are therefore not Lewis acids.
Conversely, many Lewis acids are not Brønsted-Lowry acids. In modern terminology, an acid is implicitly a Brønsted acid and not a Lewis acid, since chemists always refer to a Lewis acid explicitly as a Lewis acid. Modern definitions are concerned with the fundamental chemical reactions common to all acids. Most acids encountered in everyday life are aqueous solutions, or can be dissolved in water, so the Arrhenius and Brønsted-Lowry definitions are the most relevant; the Brønsted-Lowry definition is the most used definition. Hydronium ions are acids according to all three definitions. Although alcohols and amines can be Brønsted-Lowry acids, they can function as Lewis bases due to the lone pairs of electrons on their oxygen and nitrogen atoms; the Swedish chemist Svante Arrhenius attributed the properties of acidity to hydrogen ions or protons in 1884. An Arrhenius acid is a substance that, when added to water, increases the concentration of H+ ions in the water. Note that chemists write H+ and refer to the hydrogen ion when describing acid-base reactions but the free hydrogen nucleus, a proton, does not exist alone in water, it exists as the hydronium ion, H3O+.
Thus, an Arrhenius acid can be described as a substance that increases the concentration of hydronium ions when added to water. Examples include molecular substances such as acetic acid. An Arrhenius base, on the other hand, is a substance which increases the concentration of hydroxide ions when dissolved in water; this decreases the concentration of hydronium because the ions react to form H2O molecules: H3O+ + OH− ⇌ H2O + H2ODue to this equilibrium, any increase in the concentration of hydronium is accompanied by a decrease in the concentration of hydroxide. Thus, an Arrhenius acid could be said to be one that decreases hydroxide concentration, while an Arrhenius base increases it. In an acidic solution, the concentration of hydronium ions is greater than 10−7 moles per liter. Since pH is defined as the negative logarithm of the concentration of hydronium ions, acidic solutions thus have a pH of less than 7. While the Arrhenius concept is useful for describing many reactions, it is quite limited in its scope.
In 1923 chemists Johannes Nicolaus Brønsted and Thomas Martin Lowry independently recognized that acid-base reactions involve the transfer of a proton. A Brønsted-Lowry acid is a species. Brønsted-Lowry acid-base theory has several advantages over Arrhenius theory. Consider the following reactions of acetic acid, the organic acid that gives vinegar its characteristic taste: CH3COOH + H2O ⇌ CH3COO− + H3O+ CH3COOH + NH3 ⇌ CH3COO− + NH+4Both theories describe the first reaction: CH3COOH acts as an Arrhenius acid because it acts as a source of H3O+ when dissolved in water, it acts as a Brønsted acid by donating a proton to water. In the second example CH3COOH undergoes the same transformation, in this case donating a proton to ammonia, but does not relate to the Arrhenius definition of an acid because the reaction does not produce hydronium. CH3COOH is