0146-B1

Mitigating Wood Shortages Through a People Friendly Tree - Poplar

D.K. Khurana^[1]

Abstract

Many countries are facing the prospects of wood shortages due to over-exploitation of their wood resources. This has led to planting of various fast-growing tree species that can yield wood at shorter rotations. One species, which has been found suitable to mitigate these shortages, is the poplar tree of the genus Populus. Many countries are planting poplars, prominent among these are China, South Korea, United States and India. In India, about 150 small and big plywood manufacturing units depend upon poplar wood in the absence of availability of other hard and soft woods. More than 30 million poplar trees have been planted during the last decade in the non-forest areas. The current plantation rate in India is approximately 23,000 ha per year both for forest species as well as for poplars. Average productivity of poplars is between 20-30 m³ ha^-1 yr^-1, but the recently developed improved clones can enhance the productivity. Where the average production of the commonly planted clones is about 0.3 m³ tree^-1, this can be improved to 0.9 m³ tree^-1 with the improved clones. Therefore, the productivity can be tripled within the same period of time with farmers getting three times more return from the same area of land.

Introduction

Many countries ever since World War II to the present day have felt wood shortages. It were there, perhaps earlier too, but were significantly noticed during and after the war period. This lead to wide scale efforts to overcome these shortages through plantations for economically important fast growing species. Almost every country went through the planning and implementation process to mitigate the wood shortages during this half a century period which saw many alteration in perceptions of many countries since the time wood shortages were first noticed. In the process many species were adopted or abandoned after few trials but the one species that has stuck with the planners and foresters for planting is - poplar. This forest species being planted on non-forest areas has outperformed any other non-forest species in its adoption by the farmers and people.

No doubt there are an estimated 3,870 million ha forest worldwide, of which 95 per cent are natural forest and only 5 per cent are the forest plantations. But at the same time it is also estimated that a substantial afforestation programme could increase the amount of tree plantations by the year 2050 to equivalent of 5 per cent of world's land-base. But the increase in the pastureland globally has been substantial which is pegged at 1 billion ha, while the increase in tree plantations has been only about 0.1 billion ha. Notwithstanding this many countries are loosing their forests at a very rapid pace due to over exploitation. Leaving aside the forest rich countries like Canada, USA, Scandinavia, Siberian Russia and some tropical countries, the remaining countries of the world with 5 billion population have less than 25 per cent of the forest wealth. About 20.4 million ha of tropical forests are lost every year (Houghton 1990). India is also not left out of this grim scenario where rapid decline in the forest area (up to about 35 per cent) has taken place between 1900 to 2000 (Chandra 2001).

This calls for that the non-forest areas where species like poplars can be planted should form the source of overcoming shortages, since they have already been performing well above average than the other species. The area being planted with poplars is rapidly increasing, particularly in China, South Korea and the United States. The International Poplar Commission listed seven countries with atleast 1,000,000 ha of area planted with poplars, whereas 12 countries were reported to have area between 10, 000 to 100,000 ha under poplars. This is far above the estimates of 1980 (Anon. 1980) when France was the country with largest area under poplar plantations (0.25 million ha) followed by Argentina (0.1 million ha) and the USA (56,000 ha).

India is another country where this poplar tree has found large acceptance with farmers and is being planted on extensive scale in the non-forest areas. In just about a quarter century, when large scale efforts in popularizing the plantations of this species were taken up by a private company (M/S Wimco Ltd.) with the active help of State Forest Departments, the plantations of this tree have gone up from 50, 000 plants in 1976 to about 10 million trees during 2001 (Anon. 1978, Chandra 2001). The rapid increase in the poplar plantations after initial hiccups have mainly been due to its extensive use by the plywood industry. Where when these plants were planted they were thought to be suitable for match sticks, paper and pulp and may be small furniture, but as the wood sources became scarce, the plywood industry started using poplar wood which could be easily veneered, and this jacked up its demand. With time the prices of poplar wood went up and farmers started planting more and more number of trees. Now more than 150 small and big plywood units are dependent on this poplar wood. This not only saves the precious forest woods but at the same time allows for the conservation of forests by taking pressure off the forests.

An estimate shows that in the northern regions of India where this poplar trees are mainly being planted by the people on non-forest areas their plantation rate is almost equal to the area being planted with conventional forest species. The area planted with the conventional forest species in part of northern India was ca23, 314 ha during the period 1990-95, in the same states during the same period more than 23,000 ha area was also planted with poplars. But if we compare the productivity of poplars it is conventionally three to four times more than the forest species. The productivity of poplar plantations are between the range of 20-30 m³ ha^-1 yr^-1 in comparison to 4.5 m³ ha^-1 yr^-1 from forest plantations. But there are plantations of poplars that yield as high productivity as 50 m³ ha^-1 yr^-1.

Selection of suitable genotypes

Poplars are found to be the ideal trees both for the farmers and foresters. Their fast growing and deciduous nature, multipurpose use and compatibility with agricultural crops have made them all the more important for inter-cropping and for plantations on non-forest areas. Poplars have been successfully grown in plantations in northern India since1980 (Chaturvedi 1982). Fast growing clones of Populus deltoides Marsh. and P. x euramericana (Dode) Guinier, extensively planted in northern India were not suitable for the temperate region of the hill states. Viart (1982) indicated the desirability of developing indigenous cultivars of poplars for all situations varying from sub-tropical to temperate regions. While the clones for the sub-tropical zone were easy to choose from the vast era of clones available from various poplar breeding and improvement centers the world over, the job was difficult for indigenous poplar where almost no information about the species was available. However, the utility of the indigenous Himalayan poplar (Populus ciliata) as a nurse crop in reforesting the temperate clear felled areas was shown in the trials conducted by the State Forest Department with silver fir (Abies pindrow) regeneration. Therefore, need was felt for identification of suitable fast growing provenances in the species.

Generally the greatest variation and the first level of selection occurs between and among species with initial attention limited to those having widest economic importance. Identification of the species having the greatest usefulness may not be always obvious. In natural forests, the forester has little control of its genetic diversity in the course of one or two generations, although diversity may be affected (usually negatively) during longer periods of forest management. The genetic diversity of plantations can be substantially increased or decreased, compared to that found in nature, depending on the species mix and the genetic architecture of the populations used in plantations (Kleinschmit et al., 1992).

The work on Populus ciliata was started in the year 1976 and up to 1979 clonal material from the natural distribution zone of the species from parts of western Himalaya were collected. These collections were repeated from a much wider area during 1984-86. With the generous help of the IDRC (International Development Research Centre, Canada) during 1989-1993 additional collections were made in P. ciliata and open pollinated seed of P. deltoides collected from the states of Louisiana, Texas and Mississippi in the USA. The selections from these material have lead to the development of new clones which are performing much better than the previously planted clones 'G-3', 'G-48', S7C15, 'Udai' and 'Kranti'.

Productivity

The normal rotation of poplars in India is about 8-10 years when a harvestable diameter of 30 cm above bark is obtained. However this diameter growth is variable and is dependant on various factors like soils, water availability and rooting behaviour (Dhanda and Verma 2001, Khurana 1994). The total above ground biomass of poplar stands normally is in the order of 26.9, 52.4, 65.8, 76.0 and 192 kg ha^-1 at age 3, 5, 7, 9 and 11 years, respectively (Table 1).

Table 1: Total standing biomass (kg ha^-1) of component plant parts for different aged poplar plantations at a density of 400 trees ha^-1.

The major important component of the wood is, however, the above ground biomass. Here too the woody biomass which can be converted into logs which can be easily veneered are the commercial parts used. The perusal of the table 2 shows that the productivity of different clones at the same site varies greatly. Whereas one clone of P. deltoides can give the productivity of almost 1 cubic meter of wood in about 7 years (clones'40-G' and '55-1'), at the same time other clones ('51-4') can give as low a yield as 0.1 m^-3. Therefore is all the more important that the clones being planted must be suitable selected and only those clones with a suitable productivity levels be planted.

Table 2: Shows the growth parameters and volume production of UHF selected new clones of Populus deltoides after 7 years in Shiwalik foothills.

If we look at the present plantations of poplars in India they number around 30 million trees covering approximately 0.06 million ha area (Chandra 2001). Their productivity is estimated to be around 0.3 cubic meter per tree on an average, but if the same trees were of a superior genotype the productivity would have tripled within the same period of time of harvest.

Literature Cited:

Anon., 1978. Plant poplars for rural prosperity. Handout of M/S Wimco Ltd., Bombay, India

Anon., 1980. Poplars and Willows. FAO, Rome, Italy

Chandra, J.P., 2001. Scope of poplar cultivation. Indian For. 127: 51-60

Chaturvedi, A.N., 1982. Poplar for farm forestry in Uttar Pradesh. Indain For. 107: 661-664

Dhanda, R.S. and R.K. Verma, 2001. Growth performance o Populus dltoides bartr. In agroforestry planataions in Punjab. In: D.K. Khurana (Ed.). Poplars in India: Recent Research Trends. IDRC-UHF publication.: 41-56 pp (Available from Dept. of Tree Improvement, College of Forestry, UHF, Nauni-Solan-173 230, India)

Houghton, R. A., 1990. The global effects of tropical deforestation. Environment Science & Technology.

Khurana, D.K., 1994. Preliminary selection of poplar genotypes for agroforestry systems. In: Panjab Singh, P.S. Pathak and M.M. Roy (Eds.). Agroforestry Systems for Degraded Lands Vol. I. RMSI, Jhansi: 279-285 pp

Kleinschmit, J., D.K. Khurana, H. D. Gerhold and W. J. Libby, 1992. Chapter 16: Past, present and anticipated applications of clonal forestry. In: W.J.Libby & R. Ahuja (Ed). Clonal Forestry: Genetics, Biotechnology and Applications. Springer-Verlag, New York, U.S.A.:

Viart, M., (1982). Usefulness of forest genetics to extension of poplar farming in India. J. Tree Sci. 1: 8-16.