Bamboo fibre - Cultivation,Ecology,Genus & Geography

Bamboo 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. There are many types of bamboo, such as ‘Fargesia Qinlingensis’ in the Qinling Mountains in China.

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.

Bamboos are some of the fastest growing plants in the world.

They are capable of growing 100 cm (39 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.

Cultivation

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”.

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.

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:

• 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.
• 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.
• Cut culms are immersed in a running stream and weighted down for 3–4 weeks.
• 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.

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.

Ecology

Growth

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.

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 about 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. 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.

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.

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 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.

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 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

Soft bamboo shoots, stems, and leaves are the major food source of the Giant Panda of China, the Red Panda of Nepal and the Bamboo lemurs of Madagascar. 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; chimps and elephants of the region also eat the stalks.

Genus and geography

There are more than 70 genera divided into about 1,450 species.

Bamboo are found in diverse climates, from cold mountains to hot tropical regions. They occur across East Asia, from 50°N latitude in Sakhalin through to Northern Australia, and west to India and the Himalayas.

They also occur in sub-Saharan Africa, and in the Americas from the Mid-Atlantic United States 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.

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.