guadua

The 'Guadua', which was first identified as 'Bambusa guadua' by Humboldt and later defined by Kunth as genus 'Guadua' (including eight subspecies of 'Guadua angustifolia'), usually grows from sea level up to 2.000 m altitude in little woods along brooks, but also on meadows or sloping sites. Each stem grows out of a reticular root system, the rhizomes.

The tips of the rhizomes curve upwards from the root network and form the new culms. This superimposition of root systems over several hectares provides good protection against erosion. Moreover, it works as moisture storage and can be used as sewage treatment plant for settlements and farmsteads.
Due to its high growing speed, bamboo is suitable for reforestation of former rain forest areas in developing countries. Besides that, the ability to bind large quantities of CO₂ says much for the ecological advantages.

Each sprouting shoot already contains all nodes, internodes and diaphragms, which are telescope-like compressed.
Bamboo culms are normally hollow and have a circular cross-section. With increasing culm height the wall diameter and wall thickness decrease, while strength properties increase.

Harvesting takes place after three to six years, harvest maturity is recognized by the lichens on the culm. Bamboo can also be called a 'lignifying giant grass' (Graminae) - harvesting by picking out the mature culms therefore does not lead to the death of the entire plant.
The strength of the Guadua culms increases with higher altitude, as well as with drier ground. The reason is a lower average temperature, thus it grows slower. The ground type also is important for physical and mechanical properties of the bamboo; scientific studies on this topic are executed at present by Juan Carlos Camargo at the Universidad Tecnológica de Pereira.

It does not grow at locations with high soil wetness, but for example at bluffs of rivers. It transports moisture by means of its tight and widely ramified root system to the culms that are higher - and therefore drier - situated.
Guadua is known as persevering pioneer plant, which is even capable to break through an ash layer of approximately 20 cm thickness after a volcanic eruption, while other plants have to settle again. This may be one of the reasons for the dominance of this plant in the Zona Cafétera / Colombia.
An exact botanical study on 'Guadua angustifolia' published Dr. Walter Liese of the 'German Research Institution for Forest and Wood Economy'.
The leading scientist in Colombia on the botany of Guadua is Dra. Ximena Londoņo

The bamboo material consists of a basic substance that holds together the fibres. These fibres run strictly axial and condense in the upper part of the culm, as well as to the outer edge. Therefore the strongest fibre lines are situated in the edge zone, where the highest static requirement lies, similar to steel reinforcement in concrete construction. These reinforced materials are called fibre composite materials in modern materials engineering. At the nodes, the fibres bend into the diaphragm and there crosslink themselves. Radial fibre structures don't exist.

The mass of the bamboo is mainly composed of 50 percent of cellulose and up to 30 percent of lignin, the cell glue. Bamboo culms taper upwards, the wall thickness decreases while the internodes get shorter.
The bamboo culm is a classic example of vegetable lightweight construction. In the outermost silicified zone run high-elastic fibres parallel to the culm axis with a tensile strength up to 40 kN/cm².
For comparison: Timber fibres approximately 5 kN/cm², steel (St 37) 36 kN/cm² and glass fibres bis zu 700 kN/cm².

The unlimited longitudinal fissility of the bamboo culm wall in the internodes is due to the strictly parallel fibres. The nodes with the strongly silicified diaphragms increase interlaminar and buckling strength of the tube. From mechanics we know that a cylindrical tube has four times the bending strength of a full cylinder with the same cross section area.
The bamboo tissue does not have any radial fibres like the rays of timber. Nor is there cambium, therefore the thickness growth stops above soil. The whole culm cross-section is 'one single annual ring'.
Oscar Hidalgo found out in a statistic study that the perimeter of a bamboo sprout in breast height multiplied with 52 corresponds approximately to the total height of the Guadua-culm.