In vascular plants, the root is the organ of a plant that lies below the surface of the soil. Roots can be aerial or aerating, that is, growing up above the ground or above water. Furthermore, a stem occurring below ground is not exceptional either. Therefore, the root is best defined as the non-nodes bearing parts of the plant's body. However, important internal structural differences between stems and roots exist; the fossil record of roots—or rather, infilled voids where roots rotted after death—spans back to the late Silurian, about 430 million years ago. Their identification is difficult, because casts and molds of roots are so similar in appearance to animal burrows, they can be discriminated using a range of features. The first root that comes from a plant is called the radicle. A root's four major functions are: absorption of inorganic nutrients. In response to the concentration of nutrients, roots synthesise cytokinin, which acts as a signal as to how fast the shoots can grow. Roots function in storage of food and nutrients.
The roots of most vascular plant species enter into symbiosis with certain fungi to form mycorrhizae, a large range of other organisms including bacteria closely associate with roots. When dissected, the arrangement of the cells in a root is root hair, epiblem, endodermis, pericycle and, the vascular tissue in the centre of a root to transport the water absorbed by the root to other places of the plant; the most striking characteristic of roots is that, roots have an endogenous origin, i.e. it originates and develops from an inner layer of the mother axis. Whereas Stem-branching and leaves are exogenous, i.e. start to develop from the cortex, an outer layer. In its simplest form, the term root architecture refers to the spatial configuration of a plant’s root system; this system can be complex and is dependent upon multiple factors such as the species of the plant itself, the composition of the soil and the availability of nutrients. The configuration of root systems serves to structurally support the plant, compete with other plants and for uptake of nutrients from the soil.
Roots grow to specific conditions. For example, a root system that has developed in dry soil may not be as efficient in flooded soil, yet plants are able to adapt to other changes in the environment, such as seasonal changes. Root architecture plays the important role of providing a secure supply of nutrients and water as well as anchorage and support; the main terms used to classify the architecture of a root system are: Branch magnitude: the number of links. Topology: the pattern of branching, including:Herringbone: alternate lateral branching off a parent root Dichotomous: opposite, forked branches Radial: whorl of branches around a rootLink length: the distance between branches. Root angle: the radial angle of a lateral root’s base around the parent root’s circumference, the angle of a lateral root from its parent root, the angle an entire system spreads. Link radius: the diameter of a root. All components of the root architecture are regulated through a complex interaction between genetic responses and responses due to environmental stimuli.
These developmental stimuli are categorised as intrinsic, the genetic and nutritional influences, or extrinsic, the environmental influences and are interpreted by signal transduction pathways. The extrinsic factors that affect root architecture include gravity, light exposure and oxygen, as well as the availability or lack of nitrogen, sulphur and sodium chloride; the main hormones and respective pathways responsible for root architecture development include: Auxin – Auxin promotes root initiation, root emergence and primary root elongation. Cytokinins – Cytokinins regulate root apical meristem size and promote lateral root elongation. Gibberellins -- Together with ethylene they promote elongation. Together with auxin they promote root elongation. Gibberellins inhibit lateral root primordia initiation. Ethylene – Ethylene promotes crown root formation. Early root growth is one of the functions of the apical meristem located near the tip of the root; the meristem cells more or less continuously divide, producing more meristem, root cap cells, undifferentiated root cells.
The latter become the primary tissues of the root, first undergoing elongation, a process that pushes the root tip forward in the growing medium. These cells differentiate and mature into specialized cells of the root tissues. Growth from apical meristems is known as primary growth. Secondary growth encompasses all growth in diameter, a major component of woody plant tissues and many nonwoody plants. For example, storage roots of sweet potato are not woody. Secondary growth occurs at the lateral meristems, namely the vascular cork cambium; the former forms secondary phloem, while the latter forms the periderm. In plants with secondary growth, the vascular cambium, originating between the xylem and the phloem, forms a cylinder of tissue along the stem and root; the vascular cambium forms new cells on both the inside and outside of the cambium cylinder, with those on the inside forming secondary xylem cells, those on the outside forming secondary phloem cells. As
An arborist, tree surgeon, or arboriculturist, is a professional in the practice of arboriculture, the cultivation and study of individual trees, shrubs and other perennial woody plants in dendrology and horticulture. Arborists focus on the health and safety of individual plants and trees, rather than managing forests or harvesting wood. An arborist's scope of work is therefore distinct from that of either a logger. To work near power wires either additional training is required for arborists or they need to be Qualified Line Clearance Arborist or Utility Arborists. There is a variety of minimum distances that must be kept from power wires depending on voltage, however the common distance for low voltage lines in urban settings is 10 feet. Arborists who climb can use a variety of techniques to ascend into the tree; the least invasive, most popular technique used is to ascend on rope. There are two common methods of Single Rope System and Moving Rope System; when personal safety is an issue, or the tree is being removed, arborists may use'spikes', attached to their chainsaw boots with straps to ascend and work.
Spikes wound the tree. An arborist's work may involve large and complex trees, or ecological communities and their abiotic components in the context of the landscape ecosystem; these may require monitoring and treatment to ensure they are healthy and suitable to property owners or community standards. This work may include all of the following: planting. Arborists may plan, write reports and give legal testimony. While some aspects of this work are done on the ground or in an office, much of it is done by arborists who perform tree services and who climb the trees with ropes and other equipment. Lifts and cranes may be used too; the work of all arborists is not the same. Some may just provide a consulting service. Arborists gain qualifications to practice arboriculture in a variety of ways and some arborists are more qualified than others. Experience working safely and in and around trees is essential. Arborists tend to specialize in one or more disciplines of arboriculture, such as diagnosis and treatment of pests and nutritional deficiencies in trees and pruning, cabling and lightning protection, or consultation and report writing.
All these disciplines are related and some arborists are well experienced in all areas of tree work, but not all arborists have the training or experience to properly practice every discipline. Arborists choose to pursue formal certification, available in some countries and varies somewhat by location. An arborist who holds certification in one or more disciplines may be expected to participate in rigorous continuing education requirements to ensure continuous improvement of skills and techniques. In Australia arboricultural education and training are streamlined countrywide through a multi-disciplinary vocational education and qualification authority called the Australian Qualifications Framework, which offers varying levels of professional qualification. Government institutions including Technical and Further Education TAFE offer Certificate III or a diploma in arboriculture as well as some universities. There are many private institutions covering similar educational framework in each state.
Recognition of prior learning is an option for practicing arborists with 10 or more experience with no prior formal training. It allows them to fast track their certification. In France a qualified arborist must hold a Management of Ornamental Trees certificate, a qualified arborist climber must hold a Pruning and Care of Trees certificate. In the UK an arborist can gain qualifications up to and including a master's degree. College-based courses include further education qualifications, such as national certificate, national diploma, while higher education courses in arboriculture include foundation degree, bachelor's degree and master's degree. In the USA a Certified Arborist is a professional who has over three years of documented and verified experience and has passed a rigorous written test from the International Society of Arboriculture. Other designations include Municipal Specialist, Utility Specialist and Board Certified Master Arborist; the USA and Canada have college-based training which if passed will give the certificate of Qualified Arborist.
The Qualified Arborist can be used to offset partial experience towards the Certified Arborist. Tree Risk Assessment Qualified credential designed by the International Society of Arboriculture was launched in 2013. At that time people holding the TRACE credential were transferred over to the TRAQ credential. In Canada there are provincially governed apprenticeship programs that allow arborists' to work near power lines upon completion; these apprenticeship program have to meet the provincial regulations, individuals must ensure they meet the requirements of the owner of the power system. Trees in urban landscape settings are subjec
Plant pathology is the scientific study of diseases in plants caused by pathogens and environmental conditions. Organisms that cause infectious disease include fungi, bacteria, viroids, virus-like organisms, protozoa and parasitic plants. Not included are ectoparasites like insects, vertebrate, or other pests that affect plant health by eating of plant tissues. Plant pathology involves the study of pathogen identification, disease etiology, disease cycles, economic impact, plant disease epidemiology, plant disease resistance, how plant diseases affect humans and animals, pathosystem genetics, management of plant diseases. Control of plant diseases is crucial to the reliable production of food, it provides significant problems in agricultural use of land, water and other inputs. Plants in both natural and cultivated populations carry inherent disease resistance, but there are numerous examples of devastating plant disease impacts such as Irish potato famine and chestnut blight, as well as recurrent severe plant diseases like rice blast, soybean cyst nematode, citrus canker.
However, disease control is reasonably successful for most crops. Disease control is achieved by use of plants that have been bred for good resistance to many diseases, by plant cultivation approaches such as crop rotation, use of pathogen-free seed, appropriate planting date and plant density, control of field moisture, pesticide use. Across large regions and many crop species, it is estimated that diseases reduce plant yields by 10% every year in more developed settings, but yield loss to diseases exceeds 20% in less developed settings. Continuing advances in the science of plant pathology are needed to improve disease control, to keep up with changes in disease pressure caused by the ongoing evolution and movement of plant pathogens and by changes in agricultural practices. Plant diseases cause major economic losses for farmers worldwide; the Food and Agriculture Organization estimates indeed that pests and diseases are responsible for about 25% of crop loss. To solve this issue, new methods are needed to detect diseases and pests early, such as novel sensors that detect plant odours and spectroscopy and biophotonics that are able to diagnose plant health and metabolism.
Most phytopathogenic fungi belong to the Ascomycetes and the Basidiomycetes. The fungi reproduce both sexually and asexually via the production of other structures. Spores may be spread long distances by air or water. Many soil inhabiting fungi are capable of living saprotrophically, carrying out the part of their life cycle in the soil; these are facultative saprotrophs. Fungal diseases may be controlled through the use of other agriculture practices. However, new races of fungi evolve that are resistant to various fungicides. Biotrophic fungal pathogens colonize living plant tissue and obtain nutrients from living host cells. Necrotrophic fungal pathogens infect and kill host tissue and extract nutrients from the dead host cells. Significant fungal plant pathogens include: Fusarium spp. Thielaviopsis spp. Verticillium spp. Magnaporthe grisea Sclerotinia sclerotiorum Ustilago spp. smut of barley Rhizoctonia spp. Phakospora pachyrhizi Puccinia spp. Armillaria spp; the oomycetes are fungus-like organisms.
They include some of the most destructive plant pathogens including the genus Phytophthora, which includes the causal agents of potato late blight and sudden oak death. Particular species of oomycetes are responsible for root rot. Despite not being related to the fungi, the oomycetes have developed similar infection strategies. Oomycetes are capable of using effector proteins to turn off a plant's defenses in its infection process. Plant pathologists group them with fungal pathogens. Significant oomycete plant pathogens include: Pythium spp. Phytophthora spp. including the potato blight of the Great Irish Famine Some slime molds in Phytomyxea cause important diseases, including club root in cabbage and its relatives and powdery scab in potatoes. These are caused by species of Spongospora, respectively. Most bacteria that are associated with plants are saprotrophic and do no harm to the plant itself. However, a small number, around 100 known species, are able to cause disease. Bacterial diseases are much more prevalent in tropical regions of the world.
Most plant pathogenic bacteria are rod-shaped. In order to be able to colonize the plant they have specific pathogenicity factors. Five main types of bacterial pathogenicity factors are known: uses of cell wall–degrading enzymes, effector proteins and exopolysaccharides. Pathogens such as Erwinia species use cell wall–degrading enzymes to cause soft rot. Agrobacterium species change the level of auxins to cause tumours with phytohormones. Exopolysaccharides are produced by bacteria and block xylem vessels leading to the death of the plant. Bacteria control the production of pathogenicity factors via quorum sensing. Significant bacterial plant pathogens: Burkholderia Proteobacteria Xanthomonas spp. Pseudomonas spp. Pseudomonas syringae pv. tomato causes tomato plants to produce less fruit, it "continues to adapt to the tomato by minimizing its recognition by the tomato immune system." Phytoplasma and Spiroplasma are genera of bacteria that lack cell walls and are related to the mycoplasmas, which are human pathogens.
Together they are referred to
Tree topping is the practice of removing whole tops of trees or large branches and/or trunks from the tops of trees, leaving stubs or lateral branches that are too small to assume the role of a terminal leader. Other common names for the practice include hat-racking, rounding over, tipping; some species of trees are more to recover from topping than others. There are alternatives to topping. Hundreds of large trees are topped each year, which causes significant stress and future safety issues, it has been shown through survey. Another popular misconception is; the removal of a large portion of a tree's canopy can have detrimental effects. When a tree is topped, newly formed bark may be susceptible to sun scald. Prolonged exposure can damage the bark, thus creating an attractive home for decay-causing organisms. Evidence of decay may be the presence of conks on the outer tree bark; the loss of leaves reduces a tree's ability to produce food. If a large tree is unable to produce enough sugars to feed the roots, it will die from starvation.
Some people have been known to top trees. When a tree is topped, many adventitious known as suckers begin to grow from the wound; this is the tree's response to the sudden loss of leaves. Although the tree is able to produce an abundance of suckers, they are susceptible to numerous problems. Firstly, this adventitious growth is succulent and susceptible to attacks by insects such as aphids and caterpillars, pathogens like fire blight. Secondly, the branch-stubs that the suckers emerge from are able to form a complete callus; this means that any pathogen that attacks a sucker may enter the tree directly though the open wound. If wood begins to rot it could create a weak branch connection between the developing suckers and the main tree leading to a possible branch failure. If a tree is unable to compartmentalize the fungi, it may reach the trunk and kill the tree. Aesthetics is another reason. A tree may be blocking the mountain view, shading the garden, or interfering with solar energy collection.
As a result, the tree never returns to its initial natural form. Large pruning wounds, such as those left behind in trees after topping, may become entry points for pathogens and may result in extensive decay. Decay undermines, to lesser extent, the long-term health and physical stability of trees. Should a tree survive topping, tissue regrowth at the site of the original topping wound is profuse; these new multiple leaders are less well-attached than was the original treetop due to the effect of advancing decay at the wound site. As these weakly attached trunks increase in size, they become more prone to fall from the tree. Wind can increase this potential. Topped trees can present significant hazards and should be inspected by a qualified arborist, who can recommend possible solutions, such as removal, bracing, or ongoing inspection. Aesthetic appeal is compromised by topping, as the natural shapes of trees are lost. Alternatives based on scientific research are replacing tree topping. For example, size reduction can maintain the aesthetics and structural integrity of a tree without damage.
Spiral thinning and other forms of canopy thinning can decrease wind resistance and allow wind to pass through trees, reducing the potential for branch failure due to wind-throw. Thinning allows more light penetration and air circulation, both important to tree health. Other cultural practices include choosing plant material that will fit in the desired location at its mature size. Ulmus parviflora – Chinese Elm Arboriculture Coppicing Pollarding Plant Amnesty Topping International Society of Arboriculture
A chainsaw is a portable, mechanical saw which cuts with a set of teeth attached to a rotating chain that runs along a guide bar. It is used in activities such as tree felling, bucking, cutting firebreaks in wildland fire suppression and harvesting of firewood. Chainsaws with specially designed bar and chain combinations have been developed as tools for use in chainsaw art and chainsaw mills. Specialized chainsaws are used for cutting concrete. Chainsaws are sometimes used for cutting ice, for example for ice sculpture and in Finland for winter swimming. Someone who uses a saw is a sawyer; the origin is debated, but a chainsaw-like tool was made around 1830 by the German orthopaedist Bernhard Heine. This instrument, the osteotome, had links of a chain carrying small cutting teeth with the edges set at an angle; as the name implies, this was used to cut bone. The prototype of the chain saw familiar today in the timber industry was pioneered in the late 18th century by two Scottish doctors, John Aitken and James Jeffray, for symphysiotomy and excision of diseased bone respectively.
The chain hand saw, a fine serrated link chain which cut on the concave side, was invented around 1783-1785. It was illustrated in Aitken's Principles of Midwifery or Puerperal Medicine and used by him in his dissecting room. Jeffray claimed to have conceived the idea of the chain saw independently about that time but it was 1790 before he was able to have it produced. In 1806, Jeffray published Cases of the Excision of Carious Joints by H. Park and P. F. Moreau with Observations by James Jeffray M. D. In this communication he translated Moreau's paper of 1803. Park and Moreau described successful excision of diseased joints the knee and elbow. Jeffray explained that the chain saw would allow a smaller wound and protect the adjacent neurovascular bundle. Symphysiotomy had too many complications for most obstetricians but Jeffray's ideas became accepted after the development of anaesthetics. Mechanised versions of the chain saw were developed but in the 19th Century, it was superseded in surgery by the Gigli twisted wire saw.
For much of the 19th century, the chain saw was a useful surgical instrument. The earliest patent for a practical "endless chain saw" was granted to Samuel J. Bens of San Francisco on January 17, 1905, his intent being to fell giant redwoods. The first portable chainsaw was patented in 1918 by Canadian millwright James Shand. After he allowed his rights to lapse in 1930 his invention was further developed by what became the German company Festo in 1933; the company now operates as Festool producing portable power tools. Other important contributors to the modern chainsaw are Andreas Stihl. In 1927, Emil Lerp, the founder of Dolmar, developed the world's first gasoline-powered chainsaw and mass-produced them. World War II interrupted the supply of German chain saws to North America, so new manufacturers sprang up including Industrial Engineering Ltd in 1947, the forerunner of Pioneer Saws. Ltd and part of Outboard Marine Corporation, the oldest manufacturer of chainsaws in North America. McCulloch in North America started to produce chainsaws in 1948.
The early models were two-person devices with long bars. Chainsaws were so heavy that they had wheels like dragsaws. Other outfits used driven lines from a wheeled power unit to drive the cutting bar. After World War II, improvements in aluminum and engine design lightened chainsaws to the point where one person could carry them. In some areas the skidder crews have been replaced by harvester. Chainsaws have entirely replaced simple man-powered saws in forestry, they come in many sizes, from small electric saws intended for home and garden use, to large "lumberjack" saws. Members of military engineer units are trained to use chainsaws as are firefighters to fight forest fires and to ventilate structure fires. There are three main types of chainsaw sharpeners - Handheld File, Electric Chain Saw and Bar Mounted. A chainsaw consists of several parts: Chainsaw engines are traditionally either a two-stroke gasoline internal combustion engine or an electric motor driven by a battery or electric power cord.
Combustion engines today are supplied through a traditional carburetor or an electronically adjustable carburetor. The traditional carburetor needs to be adjusted, i. e. when operating in high or low altitudes, or their fuel oil-to-gasoline ratios must be adjusted to run properly. Electrically influenced; these systems are provided by most large chain saw producers. Husqvarna calls its "Autotune," and it is standard on most saws of the 5XX saw series. To reduce user fatigue problems, traditional carburetors can be de-vibrated or they can be heated as well. Many saws offer a Summer mode of operation. Winter mode applies in temperatures below 0 °C / 32 °F where inside the cover a hole is opened leaving warm air to the air filter and carburetor to prevent icing. In warmer environment the hole is closed and both units are not ventilated with warm air. To ensure clean air supply to the carburetor, chainsaw producers offer different filters with fine or less fine mesh. In clean surrounding air a less fine filter can be used, in dusty environment the other.
The fine filter keeps the air clean to its o
Pollarding, a pruning system involving the removal of the upper branches of a tree, promotes a dense head of foliage and branches. In ancient Rome, Propertius mentioned pollarding during the 1st century BCE; the practice occurred in Europe since medieval times, takes place today in urban areas worldwide to maintain trees at a determined height. Traditionally, people pollarded trees for one of two reasons: for fodder to feed livestock or for wood. Fodder pollards produced "pollard hay" for livestock feed. Wood pollards were pruned at longer intervals of eight to fifteen years, a pruning cycle tending to produce upright poles favored for fence rails and posts and boat construction. Supple young willow or hazel branches may be harvested as material for weaving baskets and garden constructions such as bowers. Nowadays, the practice is sometimes used for ornamental trees, such as crepe myrtles in southern states of the USA, although the resulting tree has a stunted form rather than a natural-looking crown.
Pollarding tends to make trees live longer by maintaining them in a juvenile state and by reducing the weight and windage of the top part of the tree. Older pollards become hollow, so can be difficult to age accurately. Pollards tend to grow with denser growth-rings in the years after cutting. Pollarding began with walled cities in Europe; the smaller limbs that resulted could be used for cooking. As in coppicing, pollarding is to encourage the tree to produce new growth on a regular basis to maintain a supply of new wood for various purposes for fuel. In some areas, dried leafy branches are stored as winter fodder for stock. Depending on the use of the cut material, the length of time between cutting will vary from one year for tree hay or withies, to five years or more for larger timber. Sometimes, only some of the regrown stems may be cut in a season – this is thought to reduce the chances of death of the tree when recutting long-neglected pollards. Pollarding was preferred over coppicing in wood-pastures and other grazed areas, because animals would browse the regrowth from coppice stools.
The right to pollard or "lop" was granted to local people for fuel on common land or in royal forests. An incidental effect of pollarding in woodland is the encouragement of underbrush growth due to increased light reaching the woodland floor; this can increase species diversity. However, in woodland where pollarding was once common but has now ceased, the opposite effect occurs, as the side and top shoots develop into trunk-sized branches. An example of this can be seen in Epping Forest in London/Essex, UK, the majority of, pollarded until the late 19th century. Here, the light that reaches the woodland floor is limited owing to the thick growth of the pollarded trees. Pollards cut at about a metre above the ground are called stubs; these were used as markers in coppice or other woodland. Stubs cannot be used where the trees are browsed by animals, as the regrowing shoots are below the browse line. Although people who migrated to the United States from Europe continued the practice, experts have come to believe that pollarding older trees harms the tree.
The smaller limbs grow from wood, not as strong, the weaker trees will not live as long and can be more damaged by storms. As with coppicing, only species with vigorous epicormic growth may be made into pollards. In these species, removal of the main apical stems releases the growth of many dormant buds under the bark on the lower part of the tree. Trees without this growth will die without their branches; some smaller tree species do not form pollards, because cutting the main stem stimulates growth from the base forming a coppice stool instead. Examples of trees that do well as pollards include broadleaves such as beeches, maples, black locust or false acacia, hornbeams and limes, horse chestnuts, Eastern redbud, tree of heaven, a few conifers, such as yews; the technique is used in Africa for moringa trees to bring the nutritious leaves into easier reach for harvesting. Pollarding is used in urban forestry in certain areas for reasons such as tree size management and health concerns, it removes rotting or diseased branches to support the overall health of the tree and removes living and dead branches that could harm property and people, as well as increasing the amount of foliage in spring for aesthetic and air quality reasons.
Some trees may be rejuvenated by pollarding — for example, Bradford pear, a beautiful flowering species when young that becomes brittle and top-heavy when older. Oaks, when old, can form new trunks from the growth of pollard branches, i.e. surviving branches which have split away from the main branch naturally. "Poll" was a name for the top of the head, "to poll" was a verb meaning "to crop the hair". This use was extended to similar treatment of the horns of animals. A pollard meant someone or something, polled; the noun "pollard" came to be used as a verb: "pollarding". Pollarding has now replaced polling as the verb in the forestry sense. Pollard can be used as an a
In agriculture and gardening transplanting or replanting is the technique of moving a plant from one location to another. Most this takes the form of starting a plant from seed in optimal conditions, such as in a greenhouse or protected nursery bed replanting it in another outdoor, growing location; this is common in market gardening and truck farming, where setting out or planting out are synonymous with transplanting. In the horticulture of some ornamental plants, transplants are used infrequently and because they carry with them a significant risk of killing the plant. Transplanting has a variety of applications, including: Extending the growing season by starting plants indoors, before outdoor conditions are favorable. Different species and varieties react differently to transplanting. In all cases, avoiding transplant shock—the stress or damage received in the process—is the principal concern. Plants raised in protected conditions need a period of acclimatization, known as hardening off.
Root disturbance should be minimized. The stage of growth at which transplanting takes place, the weather conditions during transplanting, treatment after transplanting are other important factors. Commercial growers employ what are called non-containerized transplant production. Containerized transplants or plugs allow separately grown plants to be transplanted with the roots and soil intact. Grown in peat pots, soil blocks, or multiple-cell containers such as plastic packs or larger plug trays made of plastic or styrofoam. Non-containerized transplants are grown in greenhouse ground beds or benches, outdoors in-ground with row covers and hotbeds, in-ground in the open field; the plants are pulled with bare roots for transplanting, which are less-expensive than containerized transplants, but with lower yields due to poorer plant reestablishment. Containerized planting stock is classified by the size of container used. A great variety of containers has been used, with various degrees of success.
Some containers are designed to be planted with the tree e.g. the tar paper pot, the Alberta peat sausage, the Walters square bullet, paper pot systems, are filled with rooting medium and planted with the tree. Planted with the tree are other containers that are not filled with rooting medium, but in which the container is a molded block of growing medium, as with Polyloam®, Tree Start®, BR-8 Blocks®. Designs of containers for raising planting stock have been various. Containerized white spruce stock is now the norm. Most containers are tube-like. White spruce grown in a container having a 1:1 height:diameter produced greater dry weight than those in containers of 3:1 and 6:1 height:diameter configurations. Total dry weight and shoot length increased with increasing container volume; the larger the container, the fewer deployed per unit area. However, the biological advantage of size has been enough to influence a pronounced swing towards larger containers in British Columbia; the number of PSB211 styroblock plugs ordered in British Columbia decreased from 14,246,000 in 1981 to zero in 1990, while orders for PSB415 styroblock plugs increased in the same period from 257 000 to 41 008 000, although large stock is more expensive than small to raise and plant.
Other containers are not planted with the tree, e.g. Styroblock®, Superblock®, Copperblock®, Miniblock® container systems, produce Styroplug® seedlings with roots in a cohesive plug of growing medium; the plug cavities vary in volume by various combinations of top diameter and depth, from 39 to 3260 mL, but those most used, at least in British Columbia, are in the range 39 mL to 133 mL. The BC-CFS Styroblock® plug, developed in 1969/70, has become the dominant stock type for interior spruce in British Columbia. Plug sizes are indicated by a 3-figure designation, the 1st figure of which gives the top diameter and the other 2 figures the depth of the plug cavity, both dimensions approximations in centimetres; the demand for larger plugs has been increasing strongly. Stock raised in some sizes of plug can vary in age class. In British Columbia, for example, PSB 415 and PSB 313 plugs are raised as 1+0 or 2+0. PSB 615 plugs are raised other than as 2+0; the intention was to leave the plugs in situ in the Styroblocks until before planting.
But this reduced the efficiency of planting operations. Studies to compare the performance of extracted, packaged stock versus in situ stock seem not to have been carried out, but packaged stock has performed well and given no indication of distress; as advocated by Coates et al. thawed planting stock taken to the field should optimally be kept cool at 1°C to 2°C in relative humidities over 90%. For a few days, storage temperatures around 4.5°C and humidities about 50% can be tolerated. Binder and Fielder recommended that boxed seedlings retrieved from cold storage should not be exposed to temperatures above 10°C. Refrigerator vans used for transportation and on-site storage ‘maintain seedlings at 2°C to 4°C (Mitchell et al