**4.2. Bamboo natural distribution**

The use of native plant species is inherent to the bioengineering work approach and philosophy. Moreover, the use of indigenous species is a compulsory feature of the living material used in these works. Hence, the knowledge of bamboo natural distribution is necessary for its use.

Published literature notes approx. 1400 different species (grouped in one herbaceous and three woody types) identified and designated as bamboo (https://www.eeob.iastate.edu/ research/bamboo/index.html).

**4. Biotechnical properties of bamboo**

112 Bamboo - Current and Future Prospects

and effectiveness of the bioengineering work.

according to the different species and locations [8].

**4.2. Bamboo natural distribution**

**4.1. Biomass growth: aerial and root system characteristics**

The plants' biotechnical properties are those plant traits contributing to a good performance

Bamboo belongs to the grass family and has an aerial part characterized by a jointed stem called a culm. The culms are typically hollow with the exception of certain bamboo species which have solid culms. Each culm segment begins and ends with a solid joint called a node. It is in these nodes that the vegetative parts of the culm able to develop the culm vertically, produce branches and develop roots and stems if stacked or laying in the ground can be found. The underground part of the plant is built from rhizomes growing normally at a shallow depth (up to a maximum of 150 mm) from where the roots develop. These roots can grow deep into the soil up to 500 mm. The rhizomes are the main form of spreading of the plant by growing horizontally away from the plant and, because they have a similar structure as the culm with vegetative nodes developing either roots or buds, originate new shoots and new individuals. Bamboo is the fastest growing perennial, evergreen, arborescent plant with a resulting high productivity: the dry weight yield per hectare could total as much as 32–38 or even 47 tons of biomass per hectare per year but averaging 8–18 tons per ha per year in normal conditions

This productivity, expressed both for the aerial and the root parts of the plant, illustrates the ability of bamboo to cover the terrain very rapidly, to develop a dense network of subsuperficial rhizome and root system which would structure and consolidate the upper soil layer. The growth rate of each plant varies, but there are references of a 900 mm culm elongation in 1 day. The growth rate (both of the culm, the rhizome and root system, buds and shots) corresponds to a vegetative cycle that varies with the species and the climatic conditions. The growth factors (like starch reserves on the culm and the rhizome) vary with the evolution of the growth season but are maximal before sprouting, meaning a high resilience to disturbance and regeneration ability. The biomass production is very intensive both above and below ground with values of

above ground dry weight varying between 0.8 and 1 tons per ha in some references [9].

solidation and stabilization, preventing erosion and reducing infiltration [10].

The bamboo stands act as an important factor in water and nutrient conservation, as well as soil protection and runoff control. There are references of reduction in nutrient loss higher than 50% and similar values for runoff retention. This shows that bamboo stands, although having little geotechnical ability in terms of slope stabilization (due to the low depth of rooting), could have a very important role in local water cycle regulation and, therefore, soil con-

The use of native plant species is inherent to the bioengineering work approach and philosophy. Moreover, the use of indigenous species is a compulsory feature of the living material used in these works. Hence, the knowledge of bamboo natural distribution is necessary for its use.

Bamboo is globally distributed between 51°N and 47°S, particularly in subtropical, tropical and equatorial regions. It also covers a high altitude range, reaching up to 4000 m above sea level and thriving at temperatures as low as −20°C. The main area of occurrence is Asia where the largest number of species can be found.

This wide distribution does not mean that all species or even natural stands thrive without problems. Many forest stands are being intensively exploited, endangering a high number of species, namely, several mammal, bird and even bamboo species all classified as 'endangered' by IUCN. Several hundred species of bamboo occupy remaining natural forest stands not bigger than 2500 km<sup>2</sup> [11].

Due to its versatility, physical characteristics, rapid growth, and easy establishment, it is intensively exploited, not only in terms of harvesting natural forests but also in growing areas of cultivation, where there is a selection of the economically more attractive species (few dozens). The exploitation is mainly located in China, India and Southeast Asia (but also, with increasing importance, in Central and South America) and predominantly aimed at species with applicability in construction or other industries (e.g. paper pulp or laminated and other composite productions, biomass production) [12].

There is also a growing interest for bamboo as an ornamental plant, which brought the spread of several species to areas outside their natural ecological areas. This also raised some problems such as turning into invasive species and threatening natural habitats [13].
