Tree information

Local name: 

khote salla (खोटे सल्ला)

English name: 

Chir pine

Genus: 

Pinus

Species: 

roxburghii

Author: 

Sarge

Family: 

Pinaceae

A three-needled pine, with long needles forming spherical pompom-like clusters at the ends of the branches, especially in young trees. Cones ovoid. 10-18 cm by 6-9 cm when mature. with scales curved upwards at the apex.

Characteristics

Pinus roxburghii is capable of growing to a large size, and trees over 50 m high and 1 m in diameter have been recorded from India. Although evergreen, it sheds a large proportion of its needles towards the end of the dry season, from March to May. It is a strong light-demander, and the seedlings should be given full light from about three weeks after the seed has germinated. The seedlings are reasonably frost-hardy, but some protection against frost may be needed in high altitude nurseries. The tree is very tolerant of poor soil conditions and will grow even on hard, eroded red clay loams if tended properly. In some places it occurs naturally on soils derived from limestone, and so can be assumed to be able to tolerate a wide range of pH values. It does not grow well on badly drained sites.

It is a very fire-resistant species; in many parts of its range fires are a regular annual occurrence, and provided they are not too intense do little damage to mature trees. Even young trees have a considerable resistance to fire, partly because the dense almost spherical crown protects the stem from the direct action of the flames. According to Troup (1921) seedlings over one year old may be killed back to ground level by fire, but then will send up new shoots. Cattle and sheep do not graze P. roxburghii pine very much, but browsing by buffaloes and especially goats may do considerable damage.

Over much of its range P. roxburghii pine forms pure stands with practically no woody undergrowth, and often not even much grass, but with the ground covered in a carpet of dead needles. This is partially the result of fil;e and grazing, though Dobremez (1976) considers the almost pure Pinus forest to be in many places a natural climax, and not entirely dependent on fire for its formation. Pure Pinus plantations without undergrowth may be an erosion hazard on steep slopes, and this should be borne in mind in afforestation programmes. A light understorey of naturally occurring shrubs and small trees should be encouraged where possible. In many plantations colonization by hardwood species is so profuse that eventually a natural hardwood stand largely replaces the Pinus; in many places this is a good thing, as the hardwood species are more valuable to local people, particularly for fodder, than the Pinus they replace.

Unlike most Pinus species, P. roxburghii has a certain ability to coppice, especially when the trees are small, though this is of little practical importance except in the recovery of the trees after fire damage. One feature of P. roxburghii in plantations is its great ability to withstand a degree of neglect and bad treatment which would kill many other species, though, of course, increment suffers. This is one of the main reasons why it is planted so extensively.

Occurrence

The main area of occurrence of P. roxburghii in Nepal is between 900 and 1950 m, but in sheltered valleys in the foothills it sometimes extends to as low as 450 m, and in the dry upper valleys of the Karnali and Bheri it reaches 2700 m in a few localities. In the west of Nepal it forms large areas of almost pure pine forest on both north-facing and south-facing slopes, and is also found in places associated with hill Shorea robusta forest. In central Nepal it is largely confined to drier areas such as south-facing slopes, and in areas of particularly heavy rainfall, such as in the hills north and east of Pokhara, it is absent altogether. In eastern Nepal it is very localized, occurring in the lower parts of the Arun and Tamur valleys, but it is absent in wetter areas even from south-facing slopes. Thus it is characteristic of sites which are either climatically or ecologically rather dry, and apparently cannot compete with other vegetation in wetter areas. Outside Nepal it extends fairly continuously as far west as Afghanistan. East of Nepal its occurrence is more sporadic; it is found in Sikkim and Bhutan, but only in drier areas.

Natural regeneration

The seed is shed mostly from April to June, and is spread by the wind. It germinates best on bare ground, such as abandoned cultivation or burnt areas, but the seedlings are often able to establish themselves where there is a moderately dense grass cover. A dense ground cover of needles is however harmful, as even if the seeds germinate the seedling roots are unable to reach mineral soil.

The young seedlings need light and will often not be able to establish themselves even under an open canopy; this however varies with the site, and on hot, dry slopes they will withstand more shade than in cooler areas. Because of this strong demand for light, management by selection of individual trees is unsuitable for Pinus forests, if natural regeneration is needed. Either the mature trees need to be felled in groups large enough to allow seedlings to establish themselves, or a form of the uniform or shelterwood compartment system is used. The latter is the simplest method if large areas are to be dealt with, but for village forests group fellings may be preferable.

Artificial regeneration

Properly dried seed can be stored in sealed plastic bags in the nursery for more than a year, but for storage for longer than two years refrigeration is preferable. Germination of good seed is usually high, 70-90 per cent; it usually begins 8-10 days after sowing, and is complete in another 10-20 days. In Nepal nurseries, up to 10,000 plants have been raised from 1 kg of seed, but the median figure is about half this number. In nurseries below 1000 m seed sown in February-March should produce plantable stock by the onset of the monsoon, provided that the potting mixture is satisfactory, and there is good mycorrhizal development At higher altitudes the seed should be sown in August-September; the Nepal-Australia Forestry Project rule of sowing before Dasain (mid-September-mid-October) is a good one. Above 2000 m P. roxburghii may need more than a year in the nursery; but there are probably better species for such altitudes.

In a species that occurs over such a wide range of altitude and climate considerable variation between provenances is to be expected Among factors which are genetically controlled are the occurrence of twisted fibre, branch angle and needle length (Sagwal, 1981; 1982). Growth rates and adaptation to different climatic and ecological conditions will vary between provenances, and there is some evidence that resistance to brown needle disease may also vary.

So far only a limited number of provenance trials have been planted and often from these only very early results are available. They show better growth from Nepal provenances than from those from India or especially Pakistan. One difficulty of interpreting very early provenance trials is the period of 4-5 years before rapid height growth begins, and differentiation between the provenances takes place. For example in a trial at Lumle, three provenances were included, from Kusma, Tilhar and Sanno (near Pakhribas). After four years mean heights were 106, 114 and 115 cm respectively, i.e. there was a difference of 9 cm between the best and the worst. However after one more year the mean heights had increased to 621, 754, and 824 cm, and the difference between the best and the worst was now over 2 m (Lumle Agricultural Centre, n.d.).

In the meantime a good deal can be done to improve the quality of plantations by collecting seed locally from trees of good growth and form. In particular the large-scale import of seed from India and elsewhere, which is often supplied by contractors and hence may be of doubtful origin, should be abandoned as soon as possible, and seed should be collected from good stands within Nepal. This will not only save foreign exchange but should result in a better type of tree being planted.

Pinus roxburghii is very susceptible to brown needle disease, which is not confined to nursery plants, but can attack trees up to 20 years old (S. Singh, 1982). Thus particular care needs to be taken to prevent this disease becoming established in nurseries where P. roxburghii is raised. It is also susceptible to needle rust In parts of its range P. roxburghii is subject to twisted fibre, in which the fibres form a spiral up the stem, instead of running parallel to it This is not a disease, but is due to hereditary and possibly environmental factors.

Management of plantations will depend a great deal on the objects of management and local demands. In some places where broadleaved species have come in under the Pinus species the aim may be to encourage these species by thinning out the Pinus to favour them. The early prunings are not essential silviculturally, though they would improve the timber quality of the trees; they are important, however, in providing fuel and cattle bedding for the local villagers at an early stage in the life of the plantation. Future thinnings will depend very much on the objects of management, whether the main object is to produce fuel, poles or sawmill timber.

The early growth of P. roxburghii pine is slow. During its first year it makes little height growth but sends out a number of shoots from the base of the stem. This slow height growth, during which the tree develops a dense, very bushy, almost spherical form and reaches about 1 m in height, continues to the fourth or fifth year after planting. There follows a period of rapid height growth.

Best height growth recorded so far is from the experiments at Lumle Agricultural Centre, referred to above, where at 1460 m altitude the mean height of the Sanno provenance, at five years old, was 8.2 m. Near Chautara. Sindhupalchok District (1500 m) Applegate et al. (1988a; 1988b) recorded a predominant height of 8.7 m and dbh of 11.4 cm at the age of nine years, in what they regard as a high quality stand, found to correspond to Site Quality I of the Indian yield tables for P. roxburghii. Their low quality site at the same age had a mean height of 4.7 m and a mean dbh of 4.8 cm. The current annual increment was the mean for the three years before the measurements were made. Wood includes stem and branchwood, 56 per cent and 44 per cent respectively. The mean annual increment of stem wood is equivalent, very approximately, to about 4 m3 ha-1, though this may be expected to increases the trees grow larger. In India, according to Howard (1941), the mean annual increment of Quality I natural P. roxburghii culminates at slightly under 13 m3 ha-1, at about 50 years of age, including the yields from thinnings. The only trial from which figures have been seen in which the growth rates exceed the high-quality site at Chautara is the one at Lumle, described above. On the other hand a number of trials have produced results worse than the low-quality site.

At this stage no obvious correlations with altitude or other site factors can be seen, though there may be a tendency for plantations at low altitude, in the Bhabar Terai, to grow faster than those in the hills. Pinus roxburghii has failed in some trials at high altitudes, but at others reasonable growth has been obtained. For instance in a trial 82 months old at Tistung (about 1900 m) there were 94 per cent survivors, with a mean height of 4.0 metres and a dbh of 5.6 cm. In Baitadi in the Far Western Development Region plantations at 1760 m on a southeast-facing slope were successful, but at 1580 m on a northwest-facing slope results were poor (Margolis, 1982). In Solukhumbu District the most common cause for failure in P. roxburghii plantations has been planting it on sites that are too cold; however 75 per cent survival and good growth was obtained in a plantation at 2200 m on an east-facing slope in this district (J. Stewart, 1984). In the Far Western Development Region winters are colder than in the Solukhumbu area.

Some of the poor results in trials may be due to such factors as poor maintenance and the effects of brown needle disease, rather than the conditions at the particular site.

The seed ripens between January and March; the dates tend to be earlier in the east than in the west The cones only open in dry weather, and close again if there is rain, so the period during which seeds can be collected is often quite long. Good seed years occur irregularly. In India it is estimated that one out of every two or three years is a fair to good seed year; in Nepal the period may be even longer. In Darchula District three consecutive years of almost no seed production have been recorded. This does not mean that good seed years occur in a regular cycle; four bad seed years may be followed by two good or fair years, and so on. As good seed years occur irregularly, when they do occur as much seed as possible should be collected and stored for further use. In good years a single tree can produce 200-800 cones. There are 8000-12,300 seeds kg-1 and 100 cones will produce about 450 g of seed.

Importance in Nepal

It is by far the most widely planted forest tree in Nepal. In 1981 and 1982, 57 per cent of all trees planted by the Community Forestry Development Project were P. roxburghii (J.G. Campbell and Bhattarai, 1983); this proportion was reduced to 46 per cent in 1983, but was still four times as great as that of the next commonest species planted (Community Forestry Development Project, 1984).

The main reason for this preponderance is that it is one of the few species which will survive and grow well on the areas of very poor soil which are often the only sites available for forestry plantations in the hills; it is also a robust species which can be raised in small nurseries under less than optimum conditions. The very widespread use of P. roxburghii has, indeed, been often criticized, as it is of no value for fodder and is regarded in many places as an indifferent fuel. However no species has so far been found that will perform as well under community forestry conditions. One of its most important functions is as a pioneer species; once it is established other species more valuable for fuel and fodder regenerate naturally between the trees and may eventually in some cases form the most valuable part of the forest crop. Also a number of fodder species which have failed on exposed sites in the open have succeeded when planted under the shelter of Pinus species.

It is also a species which has been quite widely planted by individual farmers. In 1981-82 it amounted to 44 per cent of all species planted by them, but in 1983 this was reduced to 15 per cent. A good deal of this difference, however, is accounted for by increased planting of another species, P. wallichiana, which increased from one per cent in 1981/82 to 22 per cent in 1983. Part of the reason it has been widely planted by individuals is that seedlings are readily available in most nurseries. However it is obviously regarded by farmers as having some value.

Pinus roxburghii produces a useful constructional timber, and in former times was the main species used for house-building in Kathmandu. Nowadays Shorea robusta, which is more durable, is brought in from the Terai and has tended to replace Pinus (K.B. Shrestha, 1975) but this trend may well be reversed as the S. robusta forests become exhausted. Pine timber is still important for building in the hilly areas. The wood weighs about 650 kg m-3, air dry, and has a calorific value of about 21,200 kJ kg-1 (Hawkins, 1982). It bums rapidly and produces a lot of smoke; nevertheless it is widely used, as fuel of all sorts is very scarce in many areas, and even branches removed in pruning are assiduously collected for fuel by local villagers. Pinus roxburghii produces a very valuable resin, used in the manufacture of turpentine, rosin, and other products. Resin is mainly tapped in the Far Western Development Region of Nepal; at one time Baitadi District was the main centre, but nowadays much is being tapped in the southwestern parts of Doti District. Most used to be exported to India, but one large and one small distillation plants have been established in Nepal, and there are plans for more. Annual capacity will be 9000 t of rosin and 1985 t of turpentine, requiring a total input of 12,000 t of raw resin. Resin collection could provide a useful source of income for the local people, and export revenue for the country. It needs, however, to be carefully regulated to prevent over-tapping and consequent injury to the trees. Resin tapping also increases the fire risk, owing to the accumulation of highly inflammable resin at the base of the trees.

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