Pinus wallichiana is capable of growing into a very large tree and heights of over 50 m have been recorded in India. Like all pines it is a strong light-demander. It prefers a well-drained, porous soil, and will grow on limestone provided the soil above the rock is deep enough. The seedlings are frost-hardy. Pinus wallichiana is considerably less fire-resistant than P. roxburghii, but young trees scorched by fire will sometimes shoot from the base. In India small seedlings may suffer from drought after the end of the monsoon, and again in April and May. They can withstand competition from shrubby growth, but dense, matted grass is harmful to them. They are very easily damaged by browsing.
It is found in Nepal between 1800 and 3600 m, and very occasionally to 4400 m. It is fairly widely distributed in the midland zone, between the foothills,and the main Himalayan range, where, at its lower altitude limits, it is often mixed with P. roxburghii, but in general at these altitudes P. roxburghii will be found on south-facing slopes and P. wallichiana on north-facing slopes. It tends to be absent from the wettest parts of the midland zone. It is very charactenstic of abandoned fields and grazing land. It is abundant in the inner dry valleys, such as in the Humla-Jumla, and the edges of the arid zone round Jomsom, where It is found under rainfall of 750 mm or less; it is also very common in the Solokhumbu area. Outside Nepal it extends as far as Afghanistan in the west, and Bhutan in the east, though it is absent from Sikkim.
Where conditions are favourable P. wallichiana regenerates profusely. The seeds are shed at the end of the monsoon, in October and November, and are spread over fairly large distances, up to 200 m or more, by the wind. They stay on the ground over winter and begin to germinate at the beginning of the rains. During this dormant period they are susceptible to being eaten by birds. Best regeneration is on newly exposed, loose, porous soil, such as abandoned cultivation and landslips. It also is profuse on recently burnt areas. The seedlings can grow through shrubs and fairly heavy weed growth; bracken (Pteridium aqulinum) indicates particularly good conditions for regeneration. Though the seedlings will persist for some years, under moderate shade growth is slow, and for good development full light is needed. Opening up oak forest by lopping for fodder is often followed by dense regeneration of P. wallichiana in the gaps.
The seed ripens in October to November; there are from 15,000 to 30,000 seeds kg-1. Dry seed can be stored for up to a year in scaled plastic bags. Napier and Robbins (1987) found that germination of seed thus stored was 54 per cent initially, 79 per cent after nine months, 62 per cent after a year, but only 29 per cent after 15 months; thus to store seed for more than a year refrigerated storage is desirable. Seed stored in cloth bags began to lose viability rapidly after six months.
In warm weather germination usually begins after about three weeks, and is complete about ten days later, but in high altitude nurseries seed sown in winter will frequently not germinate until March. The seedlings are rather slow growth, and at lower altitudes, say at 1500 m, will need 15-16 months in the nursery; that is, the seed should be sown at the end of the cold period, about March. Between 1500 and 2000 m 22-23 months will be needed in the nursery and above 2000 m 27-28 months.
Normal plantation techniques are used. Some trials have been made of the use of bare-transplants, but results from plants in polypots have been better; for instance at Tistung (1900 m) survival of bare-root, unpruned plants was 23 per cent; of bare-root plants root pruned m the nursery 44 per cent; and of plants in polypots 72 per cent. Plants removed from the polythene bags before being transported from the nursery to the field, an undesirable but by no means unknown practice, have survived very badly, as have natural seedlings collected from the forest and planted into polythene bags.
Trials of different planting dates at Pakhribas gave 100 per cent survival for seedlings planted from April to August, 67 per cent for September, 75 per cent for October and 92 per cent for November (L. Joshi and Sherpa, 1992). This indicates that the planting dates for P. wallichiana are more flexible than those for many other species. However during the early rains is still the safest time to plant; apart from survival, late planting is likely to result in lower rates of increment in the first year.
The susceptibility of P. wallichiana to brown needle disease has already been referred to. It can be severe in the nursery and on young seedlings, but once the trees have started to grow quickly, at about four years old, the damage caused becomes less serious. The needles are also attacked by Dothistrorno needle blight, caused by Mycosphaerella pini, but so far no reports of serious damage have been seen. Pinus wallichiana needle rust (Coleosporium barclayense) has also been recorded on seedlings and trees up to ten years old; it causes needle necrosis and needle cast, but again there have been no reports of serious damage. Although regeneration is often profuse on burnt areas, young P. wallichiana is very liable to be damaged by fire. It also suffers greatly from grazing. Another harmful practice is the removal of slivers of resinous wood from the stems for use as torches and for lighting fires.
Survival in trials has usually been good, especially at altitudes of over 2000 m; below 1600 m survival in some cases has been moderate to poor,though other reasons than altitude may have contributed to this. It is interesting that survival rates of 89 per cent have been recorded from Thulo Chaur, Mustang, at 2550 m an area of low rainfall (R.B. Joshi, 1985).
The rate of growth is slow, and in most comparative trials P. wallichiana has had the lowest rate of height growth of all pines tested. As in P. roxburghii growth for about the first four years after planting is very slow, after which it increases however in general, best height growth at the age of ten years is under 5 m. The recorded exceptions are at altitudes below the natural range for P. wallichiana; at Gharamdi, near Lumle (1450 m) mean height increased from 1 m at four years to 5.1 m at five years (Lumle Agricultural Centre, n.d.), and at Godavari (1520 m) a mean height of 6.3 m at eight years was recorded.
Raeside (1986) has produced yield and volume tables for P. wallichiana in Jumla District. These are for natural stands in an area of relatively low rainfall; plantations on better sites may be expected to grow rather faster. Raeside's thesis also includes biomass tables and branchwood yields. The yields are low; a good conifer plantation in the United Kingdom will have a maximum mean annual increment of 15 m3 ha-1 or more.
In a species growing in such a wide range of altitudes and rainfall considerable differences between provenances are to be expected; however very few comparative trials have been made. At Kharidunga (2400 m) the best three provenances, based on growth of young trees, were from Tashunga, in Solokhumbu; Daman in Makwanpur; and Rara, in Mugu District. At Tistung (1900 m) the best three were from Rasumwa; Melung, in Dolakha District; and Taplejung. In the Tistung trial provenances from Pakistan gave poorer results than those from Nepal, and suffered more from brown needle disease. It is not possible to draw many conclusions from these very limited trials.
The timber is of better quality and is more durable than that of P. roxburghii, and in the parts of Nepal where the tree is plentiful it is widely used for house building. It weighs about 480 kg m-3 and has a calorific value of about 20,900 kJ kg-1 (Hawkins, 1982). Where it occurs naturally it is highly valued as a fuelwood, and resin-impregnated spills from the trunk are used for lighting in remote areas. It produces a good resin, but the yield is less than that from P. roxburghii; it has not so far been tapped for resin in Nepal.
It is an important species for afforestation at higher altitudes, for though it is slower growing than P. roxburghii it is more cold-resistant and produces a better timber. From one per cent of the total number of seedlings planted by the Community Forestry Development Project in 1981-1982 it rose to 11 per cent in 1983, when it was the second most common species planted. The mean survival rate, however, declined from 81 per cent in 1981-1982, to 73 per cent in 1983 (J.G. Campbell and Bhattarai, 1983; Community Forestry Development Project, 1984).