In India, natural bamboo resources ate dwindling – due to over-exploitation, shifting cultivation practices and extensive forest fires. Only plantations can ensure sustained availability. Work done in India and elsewhere on growth and development of culms is very meager on plantation crop.
This article describes the results from first year to tenth year old plantation bamboo (Bambusa bambos) i.e., culm growth; development, annual and monthly recruitment of culms, culm height and diameter. The culm height was 1.4 m in first year, increased to 28.5 m at sixth year and starts to decrease only 7.4 m at tenth year.
Their corresponding diameter was 2.1 cm, 8.2 cm and 2.5 cm respectively. Culm recruitment was monsoon dependent. There was a linear increase in the total above ground biomass for all components with percentage contribution of culm maximum followed by branches and leaves.
Bamboo is used for, nearly every aspect of daily life. Though, a major portion of the requirements is met from the natural stands, the increasing demand can be met only through plantations. Research has increased rapidly in recent years. Studies on the effect of container size on seedling growth on a number of species point to the positive effect of using larger containers.
The supply of nutrients increases the growth and biomass production in seedlings. A survey of literature reveals that work on growth and organic productivity of bamboo in natural habitat and in plantations is very meager, and also scientific study on culm development and biomass productivity in an age series of plantation bamboo is lacking. In order to fill-up this lacuna, the present investigation is aimed to study the growth and development of culms, in plantations.
Materials and Methods Used in Growth of Culms in Bamboo Plantation:
(a) Study Area:
The study covered an area of plantations of Bambusa bambos located at Kallipatty, Tamil Nadu State lying at a latitude between 11o28’ and 12°E and longitude 76°59′ and 77°47′ N with an altitude of 540 m above mean sea level. This area has red soil with a pH of between 7.4 and 7.8. Soil nitrogen, phosphorus, potassium, calcium and magnesium were 3800, 360, 3600, 1600 and 1800 kg/ha respectively. The mean temperature is 31°C and the mean annual rainfall is 600 mm.
(b) Growth Measurement:
From the study area, fifteen clumps were randomly selected from the sixth year plantation and identified with paint marking. The numbers of culms in these selected clumps were counted. New culms sprouting from the selected clumps were taken for growth measurements.
In each clump, five newly sprouted culms were marked with paint, totaling 150 observations. On alternate days, the height of each culm was measured and after, it had reached 1.37 m height, the diameter at breast height (DBH) was recorded. All observations were made for the basal area girth, DBH and growth in height on all culms.
(c) Monthly and Annual Recruitment of Culms:
From the study area, another set of fifteen clumps was selected randomly from the sixth year, plantation for the assessment of monthly recruitment of culm. Every month, the number of newly sprouted culms and their survival were recorded. The observation continued for one full year. The year-wise production of culms per hectare for ten years has also been counted.
Discussion Related to Growth of Culms in Bamboo Plantation:
(a) Culm Growth and Development:
The appearance of the culm was very slender and the growth of the sprout was initially slow. The daily average increase in height of culm was approximately 30 cm. (Table 1).
Until, the 32nd day the internodes were wrapped with sheaths. Thereafter, during the next month the culms lost their sheaths. After 50 days, branch buds began to develop.
These branch buds increased two or three in number in a circle and were clearly visible after 60 days. Their length began to increase after a further 30 days (i.e. 90 days after their emergence), after which leaf buds began to appear on alternate nodes. These leaves began to mature in the 30 days following their appearance.
They varied in length from 15 to 20 cm attaining their full development around the 135th day. Thereafter, the culms began to change in hardness and color. The new culms produced were peripherally from the outer edge of the clump and tended to grow inwards and become entangled amongst the older culms.
The growth of the newly developing culm in the 6th year plantation was followed from a 6 year old clump starting from initiation till maturation on the days indicated above. Along with the growth measurement of the culm with its branches and leaves were brought to laboratory, dried and weighed as described under materials and methods. The values expressed are the average of three independent experiments.
(b) Monthly Recruitment of Culms:
The productivity of bamboo was assessed on the basis of the number of new culms produced annually. At a given site, the production of new culms depended mostly on the degree of congestion, the clump age and the rainfall of the previous year. The average monthly recruitment of culms presented in Table 2.
Sample Culm Number
It revealed that maximum recruitment of culms took place during September – November, which was the monsoon season. An average of, 17 culms were produced from one clump. However, their survival rate was reduced drastically due to white ants and other physiological causes. Monsoon dependency of the plantation was prominent since, the maximum recruitment of culms seems to be monsoon dependents rather than intermittent showers.
(c) Annual Recruitment of Culms:
Bambusa bambos species produced only 5 culms per clump in the first year. The average number of culms gradually increased in the subsequent years and became maximum (17 culms/clump) in the 6th year of clump age. Number of culm production slowly decreased from the 7th year and were only 6 in the 10th year, of clump age. Bambusa species up-to 6th year of age made crowded condition due to short (7 – 12 cm) neck pachymorph rhizome system.
This crowded and congested condition created a scarcity of room for the new emerging culms and also increased competition among them for survival. Probably due to this reason culm production – subsequently decreased from the 7th year in Bambusa species, in this study.
(d) Culm Height and Diameter:
Culms of all bamboo species complete their growth within 2 to 3 months after the emergence of sprouts from the ground, but their diameter and height do not increase after the growth is over. It has been observed that in Bambusa bambos, the culms were emerged in the first year were short in length (1.4 m) and narrow in diameter (2.3 cm).
Culms produced in subsequent years were distinctly taller and wider in diameter than those produced in the past years and such trend is continued up-to six years in Bambusa bambos. After these periods, it has been observed that clumps of these bamboos did not produce any taller and wider culms in the subsequent years.