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Forest Inventory
Forest inventory is the systematic collection of data and forest information for assessment or analysis. An estimate of the value and possible uses of timber is an important part of the broader information required to sustain ecosystems. When taking forest inventory the following are important things to measure and note: species, diameter at breast height (DBH), height, site quality, age, and defects. From the data collected one can calculate the number of trees per acre, the basal area, the volume of trees in an area, and the value of the timber. Inventories can be done for other reasons than just calculating the value. A forest can be cruised to visually assess timber and determine potential fire hazards and the risk of fire. The results of this type of inventory can be used in preventive actions and also awareness. Wildlife surveys can be undertaken in conjunction with timber inventory to determine the number and type of wildlife within a forest. The aim of the statistical for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Timber
Lumber is wood that has been processed into uniform and useful sizes (dimensional lumber), including beams and planks or boards. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, window frames). Lumber has many uses beyond home building. Lumber is referred to as timber in the United Kingdom, Australia, and New Zealand, while in other parts of the world, including the United States and Canada, the term ''timber'' refers specifically to unprocessed wood fiber, such as cut logs or standing trees that have yet to be cut. Lumber may be supplied either rough- sawn, or surfaced on one or more of its faces. ''Rough lumber'' is the raw material for furniture-making, and manufacture of other items requiring cutting and shaping. It is available in many species, including hardwoods and softwoods, such as white pine and red pine, because of their low cost. ''Finished lumber'' is supplied in standard sizes, mostly for the construction ind ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Line Plot Survey
Line plot survey is a systematic sampling technique used on land surfaces for laying out sample plots within a rectangular grid to conduct forest inventory or agricultural research. It is a specific type of systematic sampling, similar to other statistical sampling methods such as random sampling, but more straightforward to carry out in practice.Aver,T.E. and H.E. Burkhart. 2002. Forest Measurements. 5th Ed. McGraw-Hill. New York. 456 p. This survey methodology is typically used to collect information about seedlings, shrubs, invasive species, signs of wildlife, need for fertilization, timber species count, and other similar types of data. For statistical control, all sample plots are a precise radius, typically , and must not include features outside each sampling circle. Method The method is commonly used for forest inventories. It makes it possible to accurately estimate the volume standing in a forested tract without counting every single item. Inventory specialists set up a l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quadratic Mean Diameter
In forestry, quadratic mean diameter or QMD is a measure of central tendency which is considered more appropriate than arithmetic mean for characterizing the group of trees which have been measured. For ''n'' trees, QMD is calculated using the quadratic mean formula: \sqrt where is the diameter at breast height of the ''ith'' tree. Compared to the arithmetic mean, QMD assigns greater weight to larger trees – QMD is always greater than or equal to arithmetic mean for a given set of trees. QMD can be used in timber cruises to estimate the standing volume of timber in a forest, because it has the practical advantage of being directly related to basal area Basal area is the cross-sectional area of trees at breast height (1.3m or 4.5 ft above ground). It is a common way to describe stand density. In forest management, basal area usually refers to merchantable timber and is given on a per hectare ..., which in turn is directly related to volume. QMD can also be calculate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Girard Form Class
Girard form class is a form quotient calculated as the ratio of diameter inside bark at the top of the first 16 foot log to the diameter outside bark at breast height ( DBH). Its purpose is to estimate board-foot volume of whole trees from measurement of DBH, estimation of the number of logs, and estimation of the taper of the first log, based on the general relationships identified between the taper of the first log and the taper of subsequent logs. Girard form class is the primary expression of tree form in the United States. To allow for log trimming and a 1-foot stump height the diameter inside bark is measured at 17.3 feet above the ground. The closer the form class value to 100 the closer the log resembles a cylinder, where a value of 100 means the log is very nearly a cylinder. Volume tables using Girard form class are composite tables and are created independently of tree species. The volume tables may be corrected where systemic errors are identified, and modified GFC ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diameter At Breast Height
Diameter at breast height, or DBH, is a standard method of expressing the diameter of the trunk or bole of a standing tree. DBH is one of the most common dendrometric measurements. Tree trunks are measured at the height of an adult's breast, which is defined differently in different countries and situations. In many countries, DBH is measured at approximately above ground. Global variation and scientific precision The height can make a substantial difference to the measured diameter. In the United States, DBH is typically measured at above ground. In some countries, such as Australia, New Zealand, Burma, India, Malaysia, and South Africa, breast height diameter has historically been measured at a height of , but because of much active research into allometrics that are being applied to trees and forests, the convention of is more appropriate. Ornamental trees are usually measured at 1.5 metres above ground. Some authors have argued that the term DBH should be abolish ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basal Area
Basal area is the cross-sectional area of trees at breast height (1.3m or 4.5 ft above ground). It is a common way to describe stand density. In forest management, basal area usually refers to merchantable timber and is given on a per hectare or per acre basis. If one cut down all the merchantable trees on an acre at off the ground and measured the square inches on the top of each stump (πr*r), added them all together and divided by square feet (144 sq inches per square foot), that would be the basal area on that acre. In forest ecology, basal area is used as a relatively easily-measured surrogate of total forest biomass and structural complexity, and change in basal area over time is an important indicator of forest recovery during succession . Estimation from diameter at breast height The basal area (BA) of a tree can be estimated from its diameter at breast height Diameter at breast height, or DBH, is a standard method of expressing the diameter of the trunk or bol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cohort (statistics)
In statistics, epidemiology, marketing and demography, a cohort is a group of research subject, subjects who share a defining characteristic (typically subjects who experienced a common event in a selected time period, such as birth or graduation). Comparison with period data Cohort data can oftentimes be more advantageous to Demography, demographers than period data. Because cohort data is honed to a specific time period, it is usually more accurate. It is more accurate because it can be tuned to retrieve custom data for a specific study. In addition, cohort data is not affected by tempo effects, unlike period data. However, cohort data can be disadvantageous in the sense that it can take a long amount of time to collect the data necessary for the cohort study. Another disadvantage of cohort studies is that it can be extremely costly to carry out, since the study will go on for a long period of time, demographers often require sufficient funds to fuel the study. Demography ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transect
A transect is a path along which one counts and records occurrences of the objects of study (e.g. plants). It requires an observer to move along a fixed path and to count occurrences along the path and, at the same time (in some procedures), obtain the distance of the object from the path. This results in an estimate of the area covered and an estimate of the way in which detectability increases from probability 0 (far from the path) towards 1 (near the path). Using the raw count and this probability function, one can arrive at an estimate of the actual density of objects. The estimation of the abundance of populations (such as terrestrial mammal species) can be achieved using a number of different types of transect methods, such as strip transects, Line-intercept sampling, line transects, belt transects, point transects, Gradsect, gradsects and curved line transects.Line Lex Hiby, M. B. Krishna 2001. "Transect Sampling from a Curving Path". ''Biometrics''. 57(3):727–73 See al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relascope
The relascope, invented by Walter Bitterlich, is a multi-use instrument for forest inventory. It is primarily used to find the height of a tree, the basal area of a tree, and the diameter of a tree anywhere along the bole. This instrument is used mostly for applications involving variable radius sample plots in a forest survey. Method of operation The relascope has a sight hole on the back and a clear window at the front to allow the user to sight through the tool. There are three light inlet holes which are used to light the scale. This is one of the major problems with the relascope, the way this instrument is designed it cannot be used in low light. This is not a problem with the electronic laser based version, called a tele-relascope. Use The Relascope is used by looking through the hole in the front of the instrument. When users look through this hole they will see several scales that are used for different measurements on the bottom half of their view, and on the top h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wedge Prism
The wedge prism is a prism with a shallow angle between its input and output surfaces. This angle is usually 3 degrees or less. Refraction at the surfaces causes the prism to deflect light by a fixed angle. When viewing a scene through such a prism, objects will appear to be offset by an amount that varies with their distance from the prism. Deflection angle For a wedge prism in air, rays of light passing through the prism are deflected by the angle δ, which is approximately given by :\delta \approx (n - 1) \alpha\ , where ''n'' is the index of refraction of the prism material, and α is the angle between the prism's surfaces. Applications The term "optical wedge" refers to any shallow angle between two plane surfaces of a window. This wedge may range from a few millionths of a degree of perfect parallelism to as much as three degrees of angle. Even though high-precision optics, such as optical flats, may be lapped and polished to extremely high levels of parallelism ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angle Gauge
An angle gauge is a tool used by foresters to determine which trees to measure when using a variable radius plot design in forest inventory. Using this tool a forester can quickly measure the trees that are in or out of the plot. An angle gauge is similar to a wedge prism though it must be held a fixed distance from the eye to work properly. Unlike the wedge prism, which is held over the plot center, the surveyor's eye is kept over plot-center when using an angle gauge. Use When using an angle gauge the user must count trees that are larger than the width of the angle gauge, as viewed from the center of the plot. The angle gauge is held a set distance from the eye of the surveyor. Most angle gauges have a string or chain that lets the user know the set distance. Each angle gauge is set at a certain basal area factor (BAF). Each tree that is in the plot represents this number, the BAF, of square footage. It is multiplied by the number of trees on the plot to give basal area ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Random Sample
In this statistics, quality assurance, and survey methodology, sampling is the selection of a subset or a statistical sample (termed sample for short) of individuals from within a statistical population to estimate characteristics of the whole population. The subset is meant to reflect the whole population, and statisticians attempt to collect samples that are representative of the population. Sampling has lower costs and faster data collection compared to recording data from the entire population (in many cases, collecting the whole population is impossible, like getting sizes of all stars in the universe), and thus, it can provide insights in cases where it is infeasible to measure an entire population. Each observation measures one or more properties (such as weight, location, colour or mass) of independent objects or individuals. In survey sampling, weights can be applied to the data to adjust for the sample design, particularly in stratified sampling. Results from probabil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
