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Bamboo
Bamboo About this sound listen (help·info) is a group of perennial evergreens in the true grass family Poaceae, subfamily Bambusoideae, tribe Bambuseae. Giant bamboos are the largest members of the grass family.
In bamboo, the internodal regions of the stem are hollow and the vascular bundles in the cross section are scattered throughout the stem instead of in a cylindrical arrangement. The dicotyledonous woody xylem is also absent. The absence of secondary growth wood causes the stems of monocots, even of palms and large bamboos, to be columnar rather than tapering.[1]
Bamboos are some of the fastest growing plants in the world.[2] They are capable of growing 60 cm (24 in.) or more per day due to a unique rhizome-dependent system. However, the growth rate is dependent on local soil and climatic conditions.
Bamboos are of notable economic and cultural significance in East Asia and South East Asia, being used for building materials, as a food source, and as a versatile raw product.
Genus and geography
There are more than 70 genera divided into about 1,450 species.[3] Bamboo are found in diverse climates, from cold mountains to hot tropical regions. They occur across East Asia, from 50°N latitude in Sakhalin[citation needed] through to Northern Australia, and west to India and the Himalayas.[4] They also occur in sub-Saharan Africa, and in the Americas from the Mid-Atlantic United States[5] south to Argentina and Chile, reaching their southernmost point anywhere, at 47°S latitude. Continental Europe is not known to have any native species of bamboo.[6]
There have recently been some attempts to grow bamboo on a commercial basis in the Great Lakes region of eastern-central Africa, especially in Rwanda.[7][8]
Ecology
Growth
Bamboo plants growing in the Philippines
Bamboo is one of the fastest-growing plants on Earth; it has been measured surging skyward as fast as 100 cm (39 in) in a 24-hour period,[2] and can also reach maximal growth rate exceeding one metre (39 inches) per hour for short periods of time. Many prehistoric bamboos exceeded heights of 85 metres (279 ft)[citation needed]. Primarily growing in regions of warmer climates during the Cretaceous period, vast fields existed in what is now Asia.
Unlike trees, all bamboo have the potential to grow to full height and girth in a single growing season of 3–4 months. During this first season, the clump of young shoots grow vertically, with no branching. In the next year, the pulpy wall of each culm or stem slowly dries and hardens. The culm begins to sprout branches and leaves from each node. During the third year, the culm further hardens. The shoot is now considered a fully mature culm. Over the next 2–5 years (depending on species), fungus and mould begin to form on the outside of the culm, which eventually penetrate and overcome the culm. Around 5 – 8 years later (species and climate dependent), the fungal and mold growth cause the culm to collapse and decay. This brief life means culms are ready for harvest and suitable for use in construction within 3 – 7 years.
Mass flowering
Although some bamboos flower every year, most species flower infrequently. In fact, many bamboos only flower at intervals as long as 60 or 120 years. These taxa exhibit mass flowering (or gregarious flowering), with all plants in the population flowering simultaneously. The longest mass flowering interval known is 130 years, and is found for all the species Phyllostachys bambusoides (Sieb. & Zucc.). In this species, all plants of the same stock flower at the same time, regardless of differences in geographic locations or climatic conditions, then the bamboo dies. The lack of environmental impact on the time of flowering indicates the presence of some sort of “alarm clock” in each cell of the plant which signals the diversion of all energy to flower production and the cessation of vegetative growth.[9] This mechanism, as well as the evolutionary cause behind it, is still largely a mystery.
One theory to explain the evolution of this semelparous mass flowering is the predator satiation hypothesis. This theory argues that by fruiting at the same time, a population increases the survival rate of their seeds by flooding the area with fruit so that even if predators eat their fill, there will still be seeds left over. By having a flowering cycle longer than the lifespan of the rodent predators, bamboos can regulate animal populations by causing starvation during the period between flowering events. Thus, according to this hypothesis, the death of the adult clone is due to resource exhaustion, as it would be more effective for parent plants to devote all resources to creating a large seed crop than to hold back energy for their own regeneration.[10]
A second theory, the fire cycle hypothesis, argues that periodic flowering followed by death of the adult plants has evolved as a mechanism to create disturbance in the habitat, thus providing the seedlings with a gap in which to grow. This hypothesis argues that the dead culms create a large fuel load, and also a large target for lightning strikes, increasing the likelihood of wildfire.[11] Because bamboos are very aggressive as early successional plants, the seedlings would be able to outstrip other plants and take over the space left by their parents.
However, both have been disputed for different reasons. The predator satiation theory does not explain why the flowering cycle is 10 times longer than the lifespan of the local rodents, something not predicted by the theory. The bamboo fire cycle theory is considered by a few scientists to be unreasonable; they argue[12] that fires only result from humans and there is no natural fire in India. This notion is considered wrong based on distribution of lightning strike data during the dry season throughout India. However, another argument against this theory is the lack of precedent for any living organism to harness something as unpredictable as lightning strikes to increase its chance of survival as part of natural evolutionary progress.[13]
The mass fruiting also has direct economic and ecological consequences, however. The huge increase in available fruit in the forests often causes a boom in rodent populations, leading to increases in disease and famine in nearby human populations. For example, there are devastating consequences when the Melocanna bambusoides population flowers and fruits once every 30–35 years[1] around the Bay of Bengal. The death of the bamboo plants following their fruiting means the local people lose their building material, and the large increase in bamboo fruit leads to a rapid increase in rodent populations. As the number of rodents increase, they consume all available food, including grain fields and stored food, sometimes leading to famine. These rats can also carry dangerous diseases such as typhus, typhoid, and bubonic plague, which can reach epidemic proportions as the rodents increase in number.
Bamboo in animal diets
Bamboo is the main food of the Giant Panda; it makes up 99% of the Panda's diet.
Soft bamboo shoots, stems, and leaves are the major food source of the Giant Panda of China and the Red Panda of Nepal. Rats will eat the fruits as described above. Mountain Gorillas of Africa also feed on bamboo and have been documented consuming bamboo sap which was fermented and alcoholic;[14] chimps and elephants of the region also eat the stalks.
Commercial timber
Timber is harvested from cultivated and wild stands and some of the larger bamboos, particularly species in the genus Phyllostachys, are known as "timber bamboos".
[edit] Harvesting
Bamboo used for construction purposes must be harvested when the culms reach their greatest strength and when sugar levels in the sap are at their lowest, as high sugar content increases the ease and rate of pest infestation.
Harvesting of bamboo is typically undertaken according to the following cycles.
1) Life cycle of the clump: As each individual culm goes through a 5-7 year life cycle, culms are ideally allowed to reach this level of maturity prior to full capacity harvesting. The clearing out or thinning of culms, particularly older decaying culms, helps to ensure adequate light and resources for new growth. Well maintained clumps may have a productivity 3-4 times that of an unharvested wild clump.
2) Life cycle of the culm: As per the life cycle described above, bamboo is harvested from 2–3 years through to 5–7 years, depending on the species.
3) Annual cycle: As all growth of new bamboo occurs during the wet season, disturbing the clump during this phase will potentially damage the upcoming crop. Also during this high rain fall period, sap levels are at their highest and then diminish towards the dry season. Picking immediately prior to the wet/growth season may also damage new shoots. Hence harvesting is best at the end of the dry season, a few months prior to the start of the wet.
4) Daily cycle: During the height of the day, Photosynthesis is at its peak producing the highest levels of sugar in sap, making this the least ideal time of day to harvest. Many traditional practitioners believe that the best time to harvest is at dawn or dusk on a full moon. This practice makes sense in terms of both moon cycles, visibility and daily cycles.
[edit] Leaching
Leaching is the removal of sap post-harvest. In many areas of the world the sap levels in harvested bamboo are reduced either through leaching or post-harvest photosynthesis. Examples of this practice include:
1. Cut bamboo is raised clear of the ground and leant against the rest of the clump for 1–2 weeks until leaves turn yellow to allow full consumption of sugars by the plant
2. A similar method is undertaken but with the base of the culm standing in fresh water, either in a large drum or stream to leach out sap
3. Cut culms are immersed in a running stream and weighted down for 3–4 weeks
4. Water is pumped through the freshly cut culms forcing out the sap (this method is often used in conjunction with the injection of some form of treatment)
In the process of water leaching, the bamboo is dried slowly and evenly in the shade to avoid cracking in the outer skin of the bamboo, thereby reducing opportunities for pest infestation.
Durability of bamboo in construction is directly related to how well it is handled from the moment of planting through harvesting, transportation, storage, design, construction and maintenance. Bamboo harvested at the correct time of year and then exposed to ground contact or rain, will break down just as quickly as incorrectly harvested material.
Ornamental bamboos
There are two general patterns for the growth of bamboo: "clumping" (sympodial) and "running" (monopodial). Clumping bamboo species tend to spread slowly, as the growth pattern of the rhizomes is to simply expand the root mass gradually, similar to ornamental grasses. "Running" bamboos, on the other hand, need to be taken care of in cultivation because of their potential for aggressive behavior. They spread mainly through their roots and/or rhizomes, which can spread widely underground and send up new culms to break through the surface. Running bamboo species are highly variable in their tendency to spread; this is related to both the species and the soil and climate conditions. Some can send out runners of several metres a year, while others can stay in the same general area for long periods. If neglected, over time they can cause problems by moving into adjacent areas.
Bamboo foliage with black stems (probably Phyllostachys nigra)
Bamboos seldom and unpredictably flower, and the frequency of flowering varies greatly from species to species. Once flowering takes place, a plant will decline and often die entirely. Although there are always a few species of bamboo in flower at any given time, collectors desiring to grow specific bamboo typically obtain their plants as divisions of already-growing plants, rather than waiting for seeds to be produced.
Regular maintenance will indicate major growth directions and locations. Once the rhizomes are cut, they are typically removed; however, rhizomes take a number of months to mature and an immature, severed rhizome will usually cease growing if left in-ground. If any bamboo shoots come up outside of the bamboo area afterwards, their presence indicates the precise location of the missed rhizome. The fibrous roots that radiate from the rhizomes do not produce more bamboo if they stay in the ground.
Bamboo growth can also be controlled by surrounding the plant or grove with a physical barrier. Typically, concrete and specially-rolled HDPE plastic are the materials used to create the barrier, which is placed in a 60–90 cm (2.0–3.0 ft) deep ditch around the planting, and angled out at the top to direct the rhizomes to the surface. (This is only possible if the barrier is installed in a straight line.) This method is very detrimental to ornamental bamboo as the bamboo within quickly becomes rootbound—showing all the signs of any unhealthy containerized plant. Symptoms include rhizomes escaping over the top, down underneath, and bursting the barrier. The bamboo within generally deteriorates in quality as fewer and fewer culms grow each year, culms live shorter periods, new culm diameter decreases, fewer leaves grow on the culms, and leaves turn yellow as the unnaturally contained rootmass quickly depletes the soil of nutrients, and curling leaves as the condensed roots cannot collect the water they need to sustain the foliage. Strong rhizomes and tools can penetrate plastic barriers with relative ease, so great care must be taken. Barriers usually fail sooner or later, or the bamboo within suffers greatly. Casual observation of many failed barriers has shown bursting of 60-mil (1.5 mm) HDPE in 5–6 years, and rhizomes diving underneath in as few as 3 years post install. In small areas regular maintenance is the only perfect method of controlling the spreading bamboos. Bamboo contained by barriers is much more difficult to remove than free-spreading bamboo. Barriers and edging are unnecessary for clump-forming bamboos. Clump-forming bamboos may eventually need to have portions removed if they become too large.
The ornamental plant sold in containers and marketed as "lucky bamboo" is actually an entirely unrelated plant, Dracaena sanderiana. It is a resilient member of the lily family that grows in the dark, tropical rainforests of Southeast Asia and Africa. Lucky Bamboo has long been associated with the Eastern practice of Feng Shui. On a similar note, Japanese knotweed is also sometimes mistaken for a bamboo but it grows wild and is considered an invasive species.
Culinary
The shoots (new bamboo culms that come out of the ground) of bamboo are edible. They are used in numerous Asian dishes and broths, and are available in supermarkets in various sliced forms, both fresh and canned version. The shoots of the giant bamboo contain cyanide. Despite this, the Golden Bamboo Lemur ingests many times the quantity of toxin that would kill a human.
The bamboo shoot in its fermented state forms an important ingredient in cuisines across the Himalayas. In Assam, for example, it is called khorisa. In Nepal, a delicacy popular across ethnic boundaries consists of bamboo shoots fermented with turmeric and oil, and cooked with potatoes into a dish that usually accompanies rice (alu tama in Nepali).
In Indonesia, they are sliced thin and then boiled with santan (thick coconut milk) and spices to make a dish called gulai rebung. Other recipes using bamboo shoots are sayur lodeh (mixed vegetables in coconut milk) and lun pia (sometimes written lumpia: fried wrapped bamboo shoots with vegetables). The shoots of some species contain toxins that need to be leached or boiled out before they can be eaten safely.
Pickled bamboo, used as a condiment, may also be made from the pith of the young shoots.
The sap of young stalks tapped during the rainy season may be fermented to make ulanzi (a sweet wine) or simply made into a soft drink. Bamboo leaves are also used as wrappers for steamed dumplings which usually contains glutinous rice and other ingredients.
Edible bamboo shoots in a Japanese market
In Sambalpur, India, the tender shoots are grated into juliennes and fermented to prepare kardi. The name is derived from the Sanskrit word for bamboo shoot, "karira". This fermented bamboo shoot is used in various culinary preparations, notably "amil", a sour vegetable soup. It is also made into pancakes using rice flour as a binding agent. The shoots that have turned a little fibrous are fermented, dried, and ground to sand sized particles to prepare a garnish known as "hendua". It is also cooked with tender pumpkin leaves to make sag green leaves.
The empty hollow in the stalks of larger bamboo is often used to cook food in many Asian cultures. Soups are boiled and rice is cooked in the hollows of fresh stalks of bamboo directly over a flame. Similarly, steamed tea is sometimes rammed into bamboo hollows to produce compressed forms of Pu-erh tea. Cooking food in bamboo is said to give the food a subtle but distinctive taste.
In addition, bamboo is frequently used for cooking utensils within many cultures and used in the manufacture of chopsticks. In modern times, some see bamboo tools as an eco-friendly alternative to other manufactured utensils.
Medicine
Bamboo is used in Chinese medicine for treating infections and healing.
It is a low-calorie source of potassium. It is known for its sweet taste and as a good source of nutrients and protein.
In Ayurveda, the Indian system of traditional medicine, the silicious concretion found in the culms of the bamboo stem is called banslochan. It is known as tabashir or tawashir in Unani-Tibb the Indo-Persian system of medicine. In English it is called "bamboo manna". This concretion is said to be a tonic for the respiratory diseases. It was earlier obtained from Melocanna bambusoides and is very hard to get; it has been largely replaced by synthetic silicic acid. In most Indian literature, Bambusa arundinacea is described as the source of bamboo manna
Construction
Bamboo scaffolding can reach great heights.
house from Bambou Habitat
House made entirely of bamboo
In its natural form, bamboo as a construction material is traditionally associated with the cultures of East Asia and the South Pacific, to some extent in Central and South America and by extension in the aesthetic of Tiki culture. In China, bamboo was used to hold up simple suspension bridges, either by making cables of split bamboo or twisting whole culms of sufficiently pliable bamboo together. One such bridge in the area of Qian-Xian is referenced in writings dating back 960 A.D. and may have stood since as far back as the 3rd century B.C., due largely to continuous maintenance.[16] It has long been used as scaffolding; the practice has been banned in China for buildings over six storeys but is still in continuous use for skyscrapers in Hong Kong.[17] In the Philippines, the Nipa Hut is a fairly typical example of the most basic sort of housing that bamboo is used for; the walls are split and woven bamboo and bamboo slats and poles may be used as its support. In Japanese architecture, bamboo is used primarily as a supplemental and/or decorative element in buildings such as fencing, fountains, grates and gutters, largely due to the ready abundance of quality timber.[18]
Various structural shapes may be made by training the bamboo to assume them as it grows. Squared sections of bamboo are created by compressing the growing stalk within a square form.[19] Arches may similarly be created by forcing the bamboo's growth with the desired form and costs many times less than it would to assume the same shape in regular wood timber. More traditional forming methods such as the application of heat and pressure may also be used to curve or flatten the cut stalks.[20]
Bamboo can be cut and laminated into sheets and planks. This process involves cutting stalks into thin strips, planing them flat, boiling and drying the strips which are then glued, pressed and finished.[21] Generally long used in China and Japan, entrepreneurs started developing and selling laminated bamboo flooring in the West during the mid 1990s;[21] products made from bamboo laminate including flooring, cabinetry, furniture and even decorative use are currently surging in popularity, transitioning from the boutique market to mainstream providers such as Home Depot. The bamboo goods industry (which also includes small goods, fabric, etc.) is expected to be worth $25 billion by the year 2012.[22] The quality of bamboo laminate varies between manufacturers and the maturity of the plant from which it was harvested (6 years being considered the optimum); the sturdiest products fulfill their claims of being up to three times harder than oak hardwood but others may be softer than standard hardwood.[21]
Bamboo intended for use in construction should be treated to resist insects and rot. The most common solution for this purpose is a mixture of borax and boric acid.[23] Another process involves boiling cut bamboo in order to remove the starches that attract bugs.[21]
Bamboo pavilion in the Shenzhen Biennale.
Bamboo has been used as reinforcement for concrete in those areas where it is plentiful, though dispute exists over its effectiveness in the various studies done on the subject. Bamboo does have the necessary strength to fulfil this function, but untreated bamboo will swell from the absorption of water from the concrete, causing it to crack. Several procedures must be followed to overcome this shortcoming.[24]
Several institutes, businesses, and universities are working on the bamboo as an ecological construction material. In the United States and France, it is possible to get houses made entirely of bamboo, which are earthquake and cyclone-resistant and internationally certified. In Bali Indonesia there is an International primary school, named the Green School, which is constructed entirely of bamboo, due to its beauty, and advantages as a sustainable resource. There are three ISO standards for bamboo as a construction material.
In parts of India, bamboo is used (- apart from common uses like making ladders, which in addition to all other uses for ladders are also used for carrying bodies in funerals -) for drying clothes indoors, both as the rod high up near the ceiling to hang clothes on as well as the stick that is wielded with acquired expert skill to hoist, spread, and to take down the clothes when dry. In Maharashtra the bamboo groves and forests are called VeLuvana, the name VeLu for Bamboo most likely from Sanskrit, while Vana is forest.
Furthermore, bamboo is also used to create flagpoles for saffron coloured, Hindu religious flags, which can be seen fluttering across India, especially Bihar and Uttar Pradesh, as well as in Guyana and Suriname.
Textiles
There are two methods by which bamboo may be processed into fiber for fabric, both developed in China. The first is a mechanical process similar to that used to process flax or hemp; the stalks are crushed and natural enzymes break them down further, allowing fibers to be combed out.[25] The other follows the process by which rayon is made where the fibers are broken down with chemicals and extruded through mechanical spinnerets; the chemicals include lye, carbon disulfide and strong acids.[21] Retailers have sold both end products as "bamboo fabric" to cash in on bamboo's current eco-friendly cachet, however the Canadian Competition Bureau[26] and the US Federal Trade Commission[27], as of mid-2009, are cracking down on the practice of labeling bamboo rayon as natural bamboo fabric. Under the guidelines of both agencies these products must be labeled as rayon with the optional qualifier "from bamboo". Bamboo fabric is known for its softness and boasts strong absorbency and anti-microbial properties, though the chemical process in bamboo rayon destroys any anti-microbial quality.[27]
In addition, the fiber of bamboo has been used to make paper in China since early times. A high quality hand-made paper is still produced in small quantities. Coarse bamboo paper is still used to make spirit money in many Chinese communities.[28]
Musical instruments
Bamboo's natural hollow form makes it an obvious choice for many instruments, particularly wind and percussion. There are numerous types of bamboo flute made all over the world, such as the dizi, xiao, shakuhachi, palendag, jinghu, angklung. In India it is a very popular and highly respected musical instrument, available even to the poorest and the choice of many highly venerated maestros of classical music. It is known and revered above all as the divine flute forever associated with Lord Krishna, who is always portrayed holding a bansuri in sculptures and paintings. The Bamboo Organ of Las Piñas, Philippines has pipes made of bamboo culms. Four of the instruments used in Polynesia for traditional hula are made of bamboo: nose flute, rattle, stamping pipes and the Jew's harp. Bamboo may be used in the construction of the Australian didgeridoo instead of the more traditional eucalyptus wood. In Indonesia, bamboo has been used for making various kinds of musical instruments including the kolintang and the angklung. The modern amplified string instrument the Chapman Stick is also constructed using bamboo. The khene (also spelled "khaen", "kaen" and "khen"; Lao: ແຄນ, Thai: แคน) is a mouth organ of Lao origin whose pipes, which are usually made of bamboo, are connected with a small, hollowed-out hardwood reservoir into which air is blown, creating a sound similar to that of the violin. In the Indian Ocean island of Madagascar, the valiha, a long tube zither made of a single bamboo stalk, is considered the national instrument.
Water processing
Bamboo as a versatile material is demonstrated by its use in water desalination. A Bamboo filter is used to remove the salt from saltwater.
Transportation
Several manufacturers offer bamboo bicycles.
In bamboo, the internodal regions of the stem are hollow and the vascular bundles in the cross section are scattered throughout the stem instead of in a cylindrical arrangement. The dicotyledonous woody xylem is also absent. The absence of secondary growth wood causes the stems of monocots, even of palms and large bamboos, to be columnar rather than tapering.[1]
Bamboos are some of the fastest growing plants in the world.[2] They are capable of growing 60 cm (24 in.) or more per day due to a unique rhizome-dependent system. However, the growth rate is dependent on local soil and climatic conditions.
Bamboos are of notable economic and cultural significance in East Asia and South East Asia, being used for building materials, as a food source, and as a versatile raw product.
Genus and geography
There are more than 70 genera divided into about 1,450 species.[3] Bamboo are found in diverse climates, from cold mountains to hot tropical regions. They occur across East Asia, from 50°N latitude in Sakhalin[citation needed] through to Northern Australia, and west to India and the Himalayas.[4] They also occur in sub-Saharan Africa, and in the Americas from the Mid-Atlantic United States[5] south to Argentina and Chile, reaching their southernmost point anywhere, at 47°S latitude. Continental Europe is not known to have any native species of bamboo.[6]
There have recently been some attempts to grow bamboo on a commercial basis in the Great Lakes region of eastern-central Africa, especially in Rwanda.[7][8]
Ecology
Growth
Bamboo plants growing in the Philippines
Bamboo is one of the fastest-growing plants on Earth; it has been measured surging skyward as fast as 100 cm (39 in) in a 24-hour period,[2] and can also reach maximal growth rate exceeding one metre (39 inches) per hour for short periods of time. Many prehistoric bamboos exceeded heights of 85 metres (279 ft)[citation needed]. Primarily growing in regions of warmer climates during the Cretaceous period, vast fields existed in what is now Asia.
Unlike trees, all bamboo have the potential to grow to full height and girth in a single growing season of 3–4 months. During this first season, the clump of young shoots grow vertically, with no branching. In the next year, the pulpy wall of each culm or stem slowly dries and hardens. The culm begins to sprout branches and leaves from each node. During the third year, the culm further hardens. The shoot is now considered a fully mature culm. Over the next 2–5 years (depending on species), fungus and mould begin to form on the outside of the culm, which eventually penetrate and overcome the culm. Around 5 – 8 years later (species and climate dependent), the fungal and mold growth cause the culm to collapse and decay. This brief life means culms are ready for harvest and suitable for use in construction within 3 – 7 years.
Mass flowering
Although some bamboos flower every year, most species flower infrequently. In fact, many bamboos only flower at intervals as long as 60 or 120 years. These taxa exhibit mass flowering (or gregarious flowering), with all plants in the population flowering simultaneously. The longest mass flowering interval known is 130 years, and is found for all the species Phyllostachys bambusoides (Sieb. & Zucc.). In this species, all plants of the same stock flower at the same time, regardless of differences in geographic locations or climatic conditions, then the bamboo dies. The lack of environmental impact on the time of flowering indicates the presence of some sort of “alarm clock” in each cell of the plant which signals the diversion of all energy to flower production and the cessation of vegetative growth.[9] This mechanism, as well as the evolutionary cause behind it, is still largely a mystery.
One theory to explain the evolution of this semelparous mass flowering is the predator satiation hypothesis. This theory argues that by fruiting at the same time, a population increases the survival rate of their seeds by flooding the area with fruit so that even if predators eat their fill, there will still be seeds left over. By having a flowering cycle longer than the lifespan of the rodent predators, bamboos can regulate animal populations by causing starvation during the period between flowering events. Thus, according to this hypothesis, the death of the adult clone is due to resource exhaustion, as it would be more effective for parent plants to devote all resources to creating a large seed crop than to hold back energy for their own regeneration.[10]
A second theory, the fire cycle hypothesis, argues that periodic flowering followed by death of the adult plants has evolved as a mechanism to create disturbance in the habitat, thus providing the seedlings with a gap in which to grow. This hypothesis argues that the dead culms create a large fuel load, and also a large target for lightning strikes, increasing the likelihood of wildfire.[11] Because bamboos are very aggressive as early successional plants, the seedlings would be able to outstrip other plants and take over the space left by their parents.
However, both have been disputed for different reasons. The predator satiation theory does not explain why the flowering cycle is 10 times longer than the lifespan of the local rodents, something not predicted by the theory. The bamboo fire cycle theory is considered by a few scientists to be unreasonable; they argue[12] that fires only result from humans and there is no natural fire in India. This notion is considered wrong based on distribution of lightning strike data during the dry season throughout India. However, another argument against this theory is the lack of precedent for any living organism to harness something as unpredictable as lightning strikes to increase its chance of survival as part of natural evolutionary progress.[13]
The mass fruiting also has direct economic and ecological consequences, however. The huge increase in available fruit in the forests often causes a boom in rodent populations, leading to increases in disease and famine in nearby human populations. For example, there are devastating consequences when the Melocanna bambusoides population flowers and fruits once every 30–35 years[1] around the Bay of Bengal. The death of the bamboo plants following their fruiting means the local people lose their building material, and the large increase in bamboo fruit leads to a rapid increase in rodent populations. As the number of rodents increase, they consume all available food, including grain fields and stored food, sometimes leading to famine. These rats can also carry dangerous diseases such as typhus, typhoid, and bubonic plague, which can reach epidemic proportions as the rodents increase in number.
Bamboo in animal diets
Bamboo is the main food of the Giant Panda; it makes up 99% of the Panda's diet.
Soft bamboo shoots, stems, and leaves are the major food source of the Giant Panda of China and the Red Panda of Nepal. Rats will eat the fruits as described above. Mountain Gorillas of Africa also feed on bamboo and have been documented consuming bamboo sap which was fermented and alcoholic;[14] chimps and elephants of the region also eat the stalks.
Commercial timber
Timber is harvested from cultivated and wild stands and some of the larger bamboos, particularly species in the genus Phyllostachys, are known as "timber bamboos".
[edit] Harvesting
Bamboo used for construction purposes must be harvested when the culms reach their greatest strength and when sugar levels in the sap are at their lowest, as high sugar content increases the ease and rate of pest infestation.
Harvesting of bamboo is typically undertaken according to the following cycles.
1) Life cycle of the clump: As each individual culm goes through a 5-7 year life cycle, culms are ideally allowed to reach this level of maturity prior to full capacity harvesting. The clearing out or thinning of culms, particularly older decaying culms, helps to ensure adequate light and resources for new growth. Well maintained clumps may have a productivity 3-4 times that of an unharvested wild clump.
2) Life cycle of the culm: As per the life cycle described above, bamboo is harvested from 2–3 years through to 5–7 years, depending on the species.
3) Annual cycle: As all growth of new bamboo occurs during the wet season, disturbing the clump during this phase will potentially damage the upcoming crop. Also during this high rain fall period, sap levels are at their highest and then diminish towards the dry season. Picking immediately prior to the wet/growth season may also damage new shoots. Hence harvesting is best at the end of the dry season, a few months prior to the start of the wet.
4) Daily cycle: During the height of the day, Photosynthesis is at its peak producing the highest levels of sugar in sap, making this the least ideal time of day to harvest. Many traditional practitioners believe that the best time to harvest is at dawn or dusk on a full moon. This practice makes sense in terms of both moon cycles, visibility and daily cycles.
[edit] Leaching
Leaching is the removal of sap post-harvest. In many areas of the world the sap levels in harvested bamboo are reduced either through leaching or post-harvest photosynthesis. Examples of this practice include:
1. Cut bamboo is raised clear of the ground and leant against the rest of the clump for 1–2 weeks until leaves turn yellow to allow full consumption of sugars by the plant
2. A similar method is undertaken but with the base of the culm standing in fresh water, either in a large drum or stream to leach out sap
3. Cut culms are immersed in a running stream and weighted down for 3–4 weeks
4. Water is pumped through the freshly cut culms forcing out the sap (this method is often used in conjunction with the injection of some form of treatment)
In the process of water leaching, the bamboo is dried slowly and evenly in the shade to avoid cracking in the outer skin of the bamboo, thereby reducing opportunities for pest infestation.
Durability of bamboo in construction is directly related to how well it is handled from the moment of planting through harvesting, transportation, storage, design, construction and maintenance. Bamboo harvested at the correct time of year and then exposed to ground contact or rain, will break down just as quickly as incorrectly harvested material.
Ornamental bamboos
There are two general patterns for the growth of bamboo: "clumping" (sympodial) and "running" (monopodial). Clumping bamboo species tend to spread slowly, as the growth pattern of the rhizomes is to simply expand the root mass gradually, similar to ornamental grasses. "Running" bamboos, on the other hand, need to be taken care of in cultivation because of their potential for aggressive behavior. They spread mainly through their roots and/or rhizomes, which can spread widely underground and send up new culms to break through the surface. Running bamboo species are highly variable in their tendency to spread; this is related to both the species and the soil and climate conditions. Some can send out runners of several metres a year, while others can stay in the same general area for long periods. If neglected, over time they can cause problems by moving into adjacent areas.
Bamboo foliage with black stems (probably Phyllostachys nigra)
Bamboos seldom and unpredictably flower, and the frequency of flowering varies greatly from species to species. Once flowering takes place, a plant will decline and often die entirely. Although there are always a few species of bamboo in flower at any given time, collectors desiring to grow specific bamboo typically obtain their plants as divisions of already-growing plants, rather than waiting for seeds to be produced.
Regular maintenance will indicate major growth directions and locations. Once the rhizomes are cut, they are typically removed; however, rhizomes take a number of months to mature and an immature, severed rhizome will usually cease growing if left in-ground. If any bamboo shoots come up outside of the bamboo area afterwards, their presence indicates the precise location of the missed rhizome. The fibrous roots that radiate from the rhizomes do not produce more bamboo if they stay in the ground.
Bamboo growth can also be controlled by surrounding the plant or grove with a physical barrier. Typically, concrete and specially-rolled HDPE plastic are the materials used to create the barrier, which is placed in a 60–90 cm (2.0–3.0 ft) deep ditch around the planting, and angled out at the top to direct the rhizomes to the surface. (This is only possible if the barrier is installed in a straight line.) This method is very detrimental to ornamental bamboo as the bamboo within quickly becomes rootbound—showing all the signs of any unhealthy containerized plant. Symptoms include rhizomes escaping over the top, down underneath, and bursting the barrier. The bamboo within generally deteriorates in quality as fewer and fewer culms grow each year, culms live shorter periods, new culm diameter decreases, fewer leaves grow on the culms, and leaves turn yellow as the unnaturally contained rootmass quickly depletes the soil of nutrients, and curling leaves as the condensed roots cannot collect the water they need to sustain the foliage. Strong rhizomes and tools can penetrate plastic barriers with relative ease, so great care must be taken. Barriers usually fail sooner or later, or the bamboo within suffers greatly. Casual observation of many failed barriers has shown bursting of 60-mil (1.5 mm) HDPE in 5–6 years, and rhizomes diving underneath in as few as 3 years post install. In small areas regular maintenance is the only perfect method of controlling the spreading bamboos. Bamboo contained by barriers is much more difficult to remove than free-spreading bamboo. Barriers and edging are unnecessary for clump-forming bamboos. Clump-forming bamboos may eventually need to have portions removed if they become too large.
The ornamental plant sold in containers and marketed as "lucky bamboo" is actually an entirely unrelated plant, Dracaena sanderiana. It is a resilient member of the lily family that grows in the dark, tropical rainforests of Southeast Asia and Africa. Lucky Bamboo has long been associated with the Eastern practice of Feng Shui. On a similar note, Japanese knotweed is also sometimes mistaken for a bamboo but it grows wild and is considered an invasive species.
Culinary
The shoots (new bamboo culms that come out of the ground) of bamboo are edible. They are used in numerous Asian dishes and broths, and are available in supermarkets in various sliced forms, both fresh and canned version. The shoots of the giant bamboo contain cyanide. Despite this, the Golden Bamboo Lemur ingests many times the quantity of toxin that would kill a human.
The bamboo shoot in its fermented state forms an important ingredient in cuisines across the Himalayas. In Assam, for example, it is called khorisa. In Nepal, a delicacy popular across ethnic boundaries consists of bamboo shoots fermented with turmeric and oil, and cooked with potatoes into a dish that usually accompanies rice (alu tama in Nepali).
In Indonesia, they are sliced thin and then boiled with santan (thick coconut milk) and spices to make a dish called gulai rebung. Other recipes using bamboo shoots are sayur lodeh (mixed vegetables in coconut milk) and lun pia (sometimes written lumpia: fried wrapped bamboo shoots with vegetables). The shoots of some species contain toxins that need to be leached or boiled out before they can be eaten safely.
Pickled bamboo, used as a condiment, may also be made from the pith of the young shoots.
The sap of young stalks tapped during the rainy season may be fermented to make ulanzi (a sweet wine) or simply made into a soft drink. Bamboo leaves are also used as wrappers for steamed dumplings which usually contains glutinous rice and other ingredients.
Edible bamboo shoots in a Japanese market
In Sambalpur, India, the tender shoots are grated into juliennes and fermented to prepare kardi. The name is derived from the Sanskrit word for bamboo shoot, "karira". This fermented bamboo shoot is used in various culinary preparations, notably "amil", a sour vegetable soup. It is also made into pancakes using rice flour as a binding agent. The shoots that have turned a little fibrous are fermented, dried, and ground to sand sized particles to prepare a garnish known as "hendua". It is also cooked with tender pumpkin leaves to make sag green leaves.
The empty hollow in the stalks of larger bamboo is often used to cook food in many Asian cultures. Soups are boiled and rice is cooked in the hollows of fresh stalks of bamboo directly over a flame. Similarly, steamed tea is sometimes rammed into bamboo hollows to produce compressed forms of Pu-erh tea. Cooking food in bamboo is said to give the food a subtle but distinctive taste.
In addition, bamboo is frequently used for cooking utensils within many cultures and used in the manufacture of chopsticks. In modern times, some see bamboo tools as an eco-friendly alternative to other manufactured utensils.
Medicine
Bamboo is used in Chinese medicine for treating infections and healing.
It is a low-calorie source of potassium. It is known for its sweet taste and as a good source of nutrients and protein.
In Ayurveda, the Indian system of traditional medicine, the silicious concretion found in the culms of the bamboo stem is called banslochan. It is known as tabashir or tawashir in Unani-Tibb the Indo-Persian system of medicine. In English it is called "bamboo manna". This concretion is said to be a tonic for the respiratory diseases. It was earlier obtained from Melocanna bambusoides and is very hard to get; it has been largely replaced by synthetic silicic acid. In most Indian literature, Bambusa arundinacea is described as the source of bamboo manna
Construction
Bamboo scaffolding can reach great heights.
house from Bambou Habitat
House made entirely of bamboo
In its natural form, bamboo as a construction material is traditionally associated with the cultures of East Asia and the South Pacific, to some extent in Central and South America and by extension in the aesthetic of Tiki culture. In China, bamboo was used to hold up simple suspension bridges, either by making cables of split bamboo or twisting whole culms of sufficiently pliable bamboo together. One such bridge in the area of Qian-Xian is referenced in writings dating back 960 A.D. and may have stood since as far back as the 3rd century B.C., due largely to continuous maintenance.[16] It has long been used as scaffolding; the practice has been banned in China for buildings over six storeys but is still in continuous use for skyscrapers in Hong Kong.[17] In the Philippines, the Nipa Hut is a fairly typical example of the most basic sort of housing that bamboo is used for; the walls are split and woven bamboo and bamboo slats and poles may be used as its support. In Japanese architecture, bamboo is used primarily as a supplemental and/or decorative element in buildings such as fencing, fountains, grates and gutters, largely due to the ready abundance of quality timber.[18]
Various structural shapes may be made by training the bamboo to assume them as it grows. Squared sections of bamboo are created by compressing the growing stalk within a square form.[19] Arches may similarly be created by forcing the bamboo's growth with the desired form and costs many times less than it would to assume the same shape in regular wood timber. More traditional forming methods such as the application of heat and pressure may also be used to curve or flatten the cut stalks.[20]
Bamboo can be cut and laminated into sheets and planks. This process involves cutting stalks into thin strips, planing them flat, boiling and drying the strips which are then glued, pressed and finished.[21] Generally long used in China and Japan, entrepreneurs started developing and selling laminated bamboo flooring in the West during the mid 1990s;[21] products made from bamboo laminate including flooring, cabinetry, furniture and even decorative use are currently surging in popularity, transitioning from the boutique market to mainstream providers such as Home Depot. The bamboo goods industry (which also includes small goods, fabric, etc.) is expected to be worth $25 billion by the year 2012.[22] The quality of bamboo laminate varies between manufacturers and the maturity of the plant from which it was harvested (6 years being considered the optimum); the sturdiest products fulfill their claims of being up to three times harder than oak hardwood but others may be softer than standard hardwood.[21]
Bamboo intended for use in construction should be treated to resist insects and rot. The most common solution for this purpose is a mixture of borax and boric acid.[23] Another process involves boiling cut bamboo in order to remove the starches that attract bugs.[21]
Bamboo pavilion in the Shenzhen Biennale.
Bamboo has been used as reinforcement for concrete in those areas where it is plentiful, though dispute exists over its effectiveness in the various studies done on the subject. Bamboo does have the necessary strength to fulfil this function, but untreated bamboo will swell from the absorption of water from the concrete, causing it to crack. Several procedures must be followed to overcome this shortcoming.[24]
Several institutes, businesses, and universities are working on the bamboo as an ecological construction material. In the United States and France, it is possible to get houses made entirely of bamboo, which are earthquake and cyclone-resistant and internationally certified. In Bali Indonesia there is an International primary school, named the Green School, which is constructed entirely of bamboo, due to its beauty, and advantages as a sustainable resource. There are three ISO standards for bamboo as a construction material.
In parts of India, bamboo is used (- apart from common uses like making ladders, which in addition to all other uses for ladders are also used for carrying bodies in funerals -) for drying clothes indoors, both as the rod high up near the ceiling to hang clothes on as well as the stick that is wielded with acquired expert skill to hoist, spread, and to take down the clothes when dry. In Maharashtra the bamboo groves and forests are called VeLuvana, the name VeLu for Bamboo most likely from Sanskrit, while Vana is forest.
Furthermore, bamboo is also used to create flagpoles for saffron coloured, Hindu religious flags, which can be seen fluttering across India, especially Bihar and Uttar Pradesh, as well as in Guyana and Suriname.
Textiles
There are two methods by which bamboo may be processed into fiber for fabric, both developed in China. The first is a mechanical process similar to that used to process flax or hemp; the stalks are crushed and natural enzymes break them down further, allowing fibers to be combed out.[25] The other follows the process by which rayon is made where the fibers are broken down with chemicals and extruded through mechanical spinnerets; the chemicals include lye, carbon disulfide and strong acids.[21] Retailers have sold both end products as "bamboo fabric" to cash in on bamboo's current eco-friendly cachet, however the Canadian Competition Bureau[26] and the US Federal Trade Commission[27], as of mid-2009, are cracking down on the practice of labeling bamboo rayon as natural bamboo fabric. Under the guidelines of both agencies these products must be labeled as rayon with the optional qualifier "from bamboo". Bamboo fabric is known for its softness and boasts strong absorbency and anti-microbial properties, though the chemical process in bamboo rayon destroys any anti-microbial quality.[27]
In addition, the fiber of bamboo has been used to make paper in China since early times. A high quality hand-made paper is still produced in small quantities. Coarse bamboo paper is still used to make spirit money in many Chinese communities.[28]
Musical instruments
Bamboo's natural hollow form makes it an obvious choice for many instruments, particularly wind and percussion. There are numerous types of bamboo flute made all over the world, such as the dizi, xiao, shakuhachi, palendag, jinghu, angklung. In India it is a very popular and highly respected musical instrument, available even to the poorest and the choice of many highly venerated maestros of classical music. It is known and revered above all as the divine flute forever associated with Lord Krishna, who is always portrayed holding a bansuri in sculptures and paintings. The Bamboo Organ of Las Piñas, Philippines has pipes made of bamboo culms. Four of the instruments used in Polynesia for traditional hula are made of bamboo: nose flute, rattle, stamping pipes and the Jew's harp. Bamboo may be used in the construction of the Australian didgeridoo instead of the more traditional eucalyptus wood. In Indonesia, bamboo has been used for making various kinds of musical instruments including the kolintang and the angklung. The modern amplified string instrument the Chapman Stick is also constructed using bamboo. The khene (also spelled "khaen", "kaen" and "khen"; Lao: ແຄນ, Thai: แคน) is a mouth organ of Lao origin whose pipes, which are usually made of bamboo, are connected with a small, hollowed-out hardwood reservoir into which air is blown, creating a sound similar to that of the violin. In the Indian Ocean island of Madagascar, the valiha, a long tube zither made of a single bamboo stalk, is considered the national instrument.
Water processing
Bamboo as a versatile material is demonstrated by its use in water desalination. A Bamboo filter is used to remove the salt from saltwater.
Transportation
Several manufacturers offer bamboo bicycles.
Monday, October 11, 2010
ชนิดของปลวก
ปลวก (Termites) แมลงที่ว่าร้ายนัก ในประเทศไทยปลวกเป็นแมลงที่นับว่าเป็นศัตรูสำคัญต่อเศรษฐกิจของประเทศทั้งโดยทางตรงและทางอ้อม โดยเฉพาะอย่างยิ่งทางด้านการเกษตร ป่าไม้ เช่น การทำลายต้นไม้ ที่ยังไม่ตัดโค่นและที่โค่นแล้ว ทำความเสียหายแก่อาคารบ้านเรือน สิ่งก่อสร้าง เครื่องเรือน วัสดุต่างๆ ที่ทำด้วยไม้และฝ้าย เป็นต้น
จากผลการสำรวจความเสียหายดังกล่าวข้างต้น ประมาณได้ว่ามีมูลค่าไม่ต่ำกว่าหนึ่งร้อยล้านบาทต่อปี นับ ว่าปลวกเป็นแมลงที่ทำลายเศรษฐกิจที่สำคัญชนิดหนึ่ง จึงควรทำความรู้จักถึงชนิดและความเป็นอยู่ของปลวก เพื่อใช้เป็นข้อมูลประกอบการป้องกันกำจัดต่อไป ปลวกเป็นแมลงที่มีชื่อเรียกภาษาอังกฤษว่า เทอร์ไมต์ (Termite) หรือบางทีเรียกว่ามดสีขาว (White ant)จัดเป็นแมลงในอันดับไอสอปเทอรา (Order Isoptera) ในอันดับนี้มีปลวกวงศ์ใหญ่อยู่ 3 วงศ์ คือ วงศ์ Kalotermitidae วงศ์ Termitidae และวงศ์ Rhinotermitidae ซึ่งมีความสำคัญทางเศรษฐกิจ ในโลกใบนี้เราพบปลวกประมาณ 2,000 ชนิด เฉพาะในภูมิภาคเอเชียตะวันออกเฉียงใต้มีประมาณ 270 ชนิด พบในประเทศไทยประมาณ 90 ชนิด ปลวกที่มีความสำคัญทางเศรษฐกิจในประเทศมีเพียง 11 ชนิด
สำหรับพวกที่เป็นภัยร้ายแรงต่อสิ่งก่อสร้างและส่วนประกอบของอาคารบ้านเรือนที่ทำด้วยวัสดุไม้คือ
1. ปลวกไม้แห้ง (Drywood termites) เป็น ปลวกที่สามารถดำรงชีวิตได้ในเนื้อไม้ที่แห้งสนิท เมื่อปลวกกัดกินเนื้อไม้จะทิ้งมูลมีลักษณะเป็นเม็ดเล็กๆ คล้ายเมล็ดฝิ่นออกจากรูที่มีขนาดเล็กในประเทศไทยพบชนิดสำคัญ 2 ชนิด คือ Cryptotermes thailandis และCryptotermes domesticus ซึ่งทำลายวัสดุที่ทำด้วยไม้ในอาคารบ้านเรือน
2. ปลวกใต้ดิน (Subterranean termites) เป็นปลวกที่อาศัยอยู่ใต้ดินเกือบตลอดอายุของมันและนับเป็นประเภทที่เป็นภัยร้ายแรงต่ออาคาร และสิ่งก่อสร้าง เพราะความเสียหายที่เกิดจากปลวกพวกนี้มีถึง 95% ชนิดที่สำคัญ 2 ชนิด คือ Coptotermes gestroi และ Globitermes sulphureus ปลวกจะขึ้นมาหาอาหารโดยการทำท่อทางเดินหรืออุโมงค์ด้วยดินเพื่อใช้เป็นทางเดินไปยังแหล่งอาหาร เช่น ตามผิวไม้ คอนกรีต สิ่งปลูกสร้างอื่นๆ ตามรอยแตกหรือช่องระหว่างพื้นบ้านกับพื้นดิน ถ้าระยะไม่ห่างเกินไปปลวกจะสร้างท่อทางเดินข้ามไปได้ ในเนื้อไม้ที่ปลวกใต้ดินเจาะทำลายภายในแล้ว จะเหลือส่วนนอกไว้เป็นแผ่นบางๆ ตอนในที่กลวงมันจะใช้ดินอุดตามช่องว่างไว้ไม่ให้ผิวไม้ยุบ
ปลวกอาศัยอยู่รวมกันเป็นสังคม ในแต่ละสังคมแบ่งออกได้เป็น 3 แบบ ตามรูปร่างและหน้าที่การทำงาน คือ ปลวกแม่รังและพ่อรัง (ปลวกราชินี-ราชา หรือปลวกตัวเมียและตัวผู้) ปลวกทหารและปลวกกรรมกร
ปลวกตัวเมียและตัวผู้ คือปลวกที่มีปีกบินได้ เราเรียกว่า แมลงเม่าซึ่งจะออกมาบินเล่นไฟในช่วงก่อนฝนตก มีหน้าที่กระจายพันธุ์และจัดตั้งสังคมหรือรังใหม่ เมื่อแมลงเม่าผสมพันธุ์กันแล้วสลัดปีกหลุดจะมุดตัวลงในดินเพื่อวางไข่และสร้างรังต่อไป ปลวก ตัวเมียจะพัฒนาตัวเองเป็นปลวกแม่รัง ทำหน้าที่ผสมพันธุ์และวางไข่เพียงอย่างเดียวปลวกคู่แรกที่ทำหน้าที่เป็น ราชินีและราชาของรังบางตัวมีอายุได้นานเกือบ 25 ปี และวางไข่ได้มากถึงวันละ 30,000 ฟอง ความสามารถในการวางไข่จะขึ้นอยู่กับจำนวนปลวกกรรมกร
ในขณะที่ไข่เจริญเป็นตัวอ่อนและตัวแก่ภายในระยะ 30-50 วันนั้นปลวก ราชินีจะเป็นตัวควบคุมตัวอ่อนให้พัฒนาบทบาทเป็นแบบต่างๆ คือ เป็นตัวผู้-ตัวเมีย เป็นปลวกกรรมกร หรือทหารปลวกกรรมกร มีปริมาณมากที่สุดกว่า 90% นั้น ลักษณะไม่มีปีก ส่วนปากมีขากรรไกรแบบฟันเลื่อยเหมาะสำหรับตัดไม้ เจาะไม้ สิ่งก่อสร้างต่างๆ มีหน้าที่สร้างซ่อมแซมรัง หาอาหารเลี้ยงดู ปลวก อื่นๆ ปลวกกรรมกรเป็นหมัน ผสมพันธุ์และสืบพันธุ์ไม่ได้ ปลวกทหาร ซึ่งมีจำนวนน้อยมากสังเกตเห็นลักษณะที่แตกต่างจากปลวกกรรมกร คือ มีหัวโตผิดปกติ ไม่มีตาที่มองเห็นได้ ส่วนของปากมีขากรรไกรขนาดใหญ่รูปลักษณะคล้ายคีมหรือดาบ เหมาะสำหรับใช้ในการต่อสู้แต่ไม่สามารถใช้ตัดหรือเจาะได้จึงมีหน้าที่ต่อสู้ เพื่อป้องกันอันตรายให้ปลวกภายในรัง โดยเฉพาะศัตรูสำคัญ คือ มด เมื่อศัตรูทำลายทางเดินหรือรัง มันจะเอาส่วนหัว ที่โตอุดช่องโหว่หรือขับไล่ศัตรูจนกว่าจนกว่าปลวกกรรมกรจะทำการซ่อมรังเรียบ ร้อยปลวกทหารบางชนิดสามารถกลั่นของเหลวที่มีพิษเป็นกรดเหนียวๆ ออกจากส่วนหัวของมัน เมื่อมดมาถูกจะเหนียวติดและหมดกำลัง นอก จากนี้กรดที่ปลวกทหารกลั่นออกมายังใช้ในการเจาะโลหะและหินปูนได้ดีอีกด้วย จึงเห็นได้ว่า ปลวกจะแบ่งแยกหน้าที่กันอย่างชัดเจนในลักษณะแมลงสังคมชนิดหนึ่ง
ปลวกมีการแพร่พันธุ์อย่างรวดเร็ว ปลวกตัวผู้และตัวเมียในรัง ที่มีอายุ 3 ปี จะกระจายพันธุ์ไปนอกรังเพื่อจัดตั้งรังใหม่ปีละ 1-2 ครั้ง ระหว่างต้นฤดูฝนหลังฝนตกใหม่ๆโดยบินจากรังเก่าในลักษณะแมลงเม่า ผสมพันธุ์แล้วสลัดปีกมุดลงดินเพื่อสร้างรังใหม่ วน เวียนกันเช่นนี้ ดังนั้นปลวกจึงมีจำนวนมากมายและเป็นปัญหาใหญ่ยากที่จะกำจัดให้หมดไปได้โดย ง่าย วิธีการที่ทำได้คือการป้องกันไม่ให้ปลวกก่อความเสียหายแก่ทรัพย์สินต่างๆ เท่านั้น อาหารหลักของปลวก คือ เซลลูโลสที่ได้จากเนื้อไม้ การกัดทำลายสิ่งของที่มี เซลลูโลสเป็นส่วนประกอบก็เพื่อนำมาใช้เป็นอาหารและที่อยู่อาศัย นอกจากนี้ซากปลวกหรือวัตถุเหลวๆ ตามตัวปลวกยังใช้กินเป็นอาหารได้ นิสัยของปลวกใช้การสื่อสารโดยสัมผัสกันตลอดเวลาจึงเป็นช่องทางหนึ่งในการ กำจัดปลวก หากปลวกได้สัมผัสสารพิษที่ใช้กำจัด จะถ่ายทอดสารพิษติดต่อถึงกันโดยง่ายและจะทำให้ปลวกตายทั้งหมดได้
จากผลการสำรวจความเสียหายดังกล่าวข้างต้น ประมาณได้ว่ามีมูลค่าไม่ต่ำกว่าหนึ่งร้อยล้านบาทต่อปี นับ ว่าปลวกเป็นแมลงที่ทำลายเศรษฐกิจที่สำคัญชนิดหนึ่ง จึงควรทำความรู้จักถึงชนิดและความเป็นอยู่ของปลวก เพื่อใช้เป็นข้อมูลประกอบการป้องกันกำจัดต่อไป ปลวกเป็นแมลงที่มีชื่อเรียกภาษาอังกฤษว่า เทอร์ไมต์ (Termite) หรือบางทีเรียกว่ามดสีขาว (White ant)จัดเป็นแมลงในอันดับไอสอปเทอรา (Order Isoptera) ในอันดับนี้มีปลวกวงศ์ใหญ่อยู่ 3 วงศ์ คือ วงศ์ Kalotermitidae วงศ์ Termitidae และวงศ์ Rhinotermitidae ซึ่งมีความสำคัญทางเศรษฐกิจ ในโลกใบนี้เราพบปลวกประมาณ 2,000 ชนิด เฉพาะในภูมิภาคเอเชียตะวันออกเฉียงใต้มีประมาณ 270 ชนิด พบในประเทศไทยประมาณ 90 ชนิด ปลวกที่มีความสำคัญทางเศรษฐกิจในประเทศมีเพียง 11 ชนิด
สำหรับพวกที่เป็นภัยร้ายแรงต่อสิ่งก่อสร้างและส่วนประกอบของอาคารบ้านเรือนที่ทำด้วยวัสดุไม้คือ
1. ปลวกไม้แห้ง (Drywood termites) เป็น ปลวกที่สามารถดำรงชีวิตได้ในเนื้อไม้ที่แห้งสนิท เมื่อปลวกกัดกินเนื้อไม้จะทิ้งมูลมีลักษณะเป็นเม็ดเล็กๆ คล้ายเมล็ดฝิ่นออกจากรูที่มีขนาดเล็กในประเทศไทยพบชนิดสำคัญ 2 ชนิด คือ Cryptotermes thailandis และCryptotermes domesticus ซึ่งทำลายวัสดุที่ทำด้วยไม้ในอาคารบ้านเรือน
2. ปลวกใต้ดิน (Subterranean termites) เป็นปลวกที่อาศัยอยู่ใต้ดินเกือบตลอดอายุของมันและนับเป็นประเภทที่เป็นภัยร้ายแรงต่ออาคาร และสิ่งก่อสร้าง เพราะความเสียหายที่เกิดจากปลวกพวกนี้มีถึง 95% ชนิดที่สำคัญ 2 ชนิด คือ Coptotermes gestroi และ Globitermes sulphureus ปลวกจะขึ้นมาหาอาหารโดยการทำท่อทางเดินหรืออุโมงค์ด้วยดินเพื่อใช้เป็นทางเดินไปยังแหล่งอาหาร เช่น ตามผิวไม้ คอนกรีต สิ่งปลูกสร้างอื่นๆ ตามรอยแตกหรือช่องระหว่างพื้นบ้านกับพื้นดิน ถ้าระยะไม่ห่างเกินไปปลวกจะสร้างท่อทางเดินข้ามไปได้ ในเนื้อไม้ที่ปลวกใต้ดินเจาะทำลายภายในแล้ว จะเหลือส่วนนอกไว้เป็นแผ่นบางๆ ตอนในที่กลวงมันจะใช้ดินอุดตามช่องว่างไว้ไม่ให้ผิวไม้ยุบ
ปลวกอาศัยอยู่รวมกันเป็นสังคม ในแต่ละสังคมแบ่งออกได้เป็น 3 แบบ ตามรูปร่างและหน้าที่การทำงาน คือ ปลวกแม่รังและพ่อรัง (ปลวกราชินี-ราชา หรือปลวกตัวเมียและตัวผู้) ปลวกทหารและปลวกกรรมกร
ปลวกตัวเมียและตัวผู้ คือปลวกที่มีปีกบินได้ เราเรียกว่า แมลงเม่าซึ่งจะออกมาบินเล่นไฟในช่วงก่อนฝนตก มีหน้าที่กระจายพันธุ์และจัดตั้งสังคมหรือรังใหม่ เมื่อแมลงเม่าผสมพันธุ์กันแล้วสลัดปีกหลุดจะมุดตัวลงในดินเพื่อวางไข่และสร้างรังต่อไป ปลวก ตัวเมียจะพัฒนาตัวเองเป็นปลวกแม่รัง ทำหน้าที่ผสมพันธุ์และวางไข่เพียงอย่างเดียวปลวกคู่แรกที่ทำหน้าที่เป็น ราชินีและราชาของรังบางตัวมีอายุได้นานเกือบ 25 ปี และวางไข่ได้มากถึงวันละ 30,000 ฟอง ความสามารถในการวางไข่จะขึ้นอยู่กับจำนวนปลวกกรรมกร
ในขณะที่ไข่เจริญเป็นตัวอ่อนและตัวแก่ภายในระยะ 30-50 วันนั้นปลวก ราชินีจะเป็นตัวควบคุมตัวอ่อนให้พัฒนาบทบาทเป็นแบบต่างๆ คือ เป็นตัวผู้-ตัวเมีย เป็นปลวกกรรมกร หรือทหารปลวกกรรมกร มีปริมาณมากที่สุดกว่า 90% นั้น ลักษณะไม่มีปีก ส่วนปากมีขากรรไกรแบบฟันเลื่อยเหมาะสำหรับตัดไม้ เจาะไม้ สิ่งก่อสร้างต่างๆ มีหน้าที่สร้างซ่อมแซมรัง หาอาหารเลี้ยงดู ปลวก อื่นๆ ปลวกกรรมกรเป็นหมัน ผสมพันธุ์และสืบพันธุ์ไม่ได้ ปลวกทหาร ซึ่งมีจำนวนน้อยมากสังเกตเห็นลักษณะที่แตกต่างจากปลวกกรรมกร คือ มีหัวโตผิดปกติ ไม่มีตาที่มองเห็นได้ ส่วนของปากมีขากรรไกรขนาดใหญ่รูปลักษณะคล้ายคีมหรือดาบ เหมาะสำหรับใช้ในการต่อสู้แต่ไม่สามารถใช้ตัดหรือเจาะได้จึงมีหน้าที่ต่อสู้ เพื่อป้องกันอันตรายให้ปลวกภายในรัง โดยเฉพาะศัตรูสำคัญ คือ มด เมื่อศัตรูทำลายทางเดินหรือรัง มันจะเอาส่วนหัว ที่โตอุดช่องโหว่หรือขับไล่ศัตรูจนกว่าจนกว่าปลวกกรรมกรจะทำการซ่อมรังเรียบ ร้อยปลวกทหารบางชนิดสามารถกลั่นของเหลวที่มีพิษเป็นกรดเหนียวๆ ออกจากส่วนหัวของมัน เมื่อมดมาถูกจะเหนียวติดและหมดกำลัง นอก จากนี้กรดที่ปลวกทหารกลั่นออกมายังใช้ในการเจาะโลหะและหินปูนได้ดีอีกด้วย จึงเห็นได้ว่า ปลวกจะแบ่งแยกหน้าที่กันอย่างชัดเจนในลักษณะแมลงสังคมชนิดหนึ่ง
ปลวกมีการแพร่พันธุ์อย่างรวดเร็ว ปลวกตัวผู้และตัวเมียในรัง ที่มีอายุ 3 ปี จะกระจายพันธุ์ไปนอกรังเพื่อจัดตั้งรังใหม่ปีละ 1-2 ครั้ง ระหว่างต้นฤดูฝนหลังฝนตกใหม่ๆโดยบินจากรังเก่าในลักษณะแมลงเม่า ผสมพันธุ์แล้วสลัดปีกมุดลงดินเพื่อสร้างรังใหม่ วน เวียนกันเช่นนี้ ดังนั้นปลวกจึงมีจำนวนมากมายและเป็นปัญหาใหญ่ยากที่จะกำจัดให้หมดไปได้โดย ง่าย วิธีการที่ทำได้คือการป้องกันไม่ให้ปลวกก่อความเสียหายแก่ทรัพย์สินต่างๆ เท่านั้น อาหารหลักของปลวก คือ เซลลูโลสที่ได้จากเนื้อไม้ การกัดทำลายสิ่งของที่มี เซลลูโลสเป็นส่วนประกอบก็เพื่อนำมาใช้เป็นอาหารและที่อยู่อาศัย นอกจากนี้ซากปลวกหรือวัตถุเหลวๆ ตามตัวปลวกยังใช้กินเป็นอาหารได้ นิสัยของปลวกใช้การสื่อสารโดยสัมผัสกันตลอดเวลาจึงเป็นช่องทางหนึ่งในการ กำจัดปลวก หากปลวกได้สัมผัสสารพิษที่ใช้กำจัด จะถ่ายทอดสารพิษติดต่อถึงกันโดยง่ายและจะทำให้ปลวกตายทั้งหมดได้
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