Report Yashwant S. Rawat, Santaram S. Oinam, Subhash C. R. Vishvakarma, Chandra P. Kuniyal and Jagdish C. Kuniyal Willow (Salix fragilis Linn.): A Multipurpose Tree Species under Pest Attack in the Cold Desert of Lahaul Valley, Northwestern Himalaya, India Salix fragilis is the most common willow species grown extensively under the indigenous agroforestry system in the cold desert of Lahaul valley located in the northwestern Himalayas, India. Presently, this tree is under severe pest attack, and other infections have made its survival in the area questionable. This deciduous multipurpose tree species provides vegetation cover to the barren landscape of Lahaul and is a significant contributor of fuel and fodder to the region. This study is a detailed profile of the plant in three villages within this region: Khoksar, Jahlma, and Hinsa. The willow provided 69.5%, 29%, and 42% of the total fuelwood requirements of Jahlma, Khoksar, and Hinsa respectively. A striking observation was that only 30.0 6 20.1% trees were healthy: 55.2 6 16.1% of the willows have dried up and 14.8 6 6.1% were in drying condition due to a combination of pest infestation and infection. To sustain this cultivation of willow under the existing agroforestry system in the region, we recommend that locally available wild species and other established varieties of willow growing in similar regions of the Himalayas be introduced on a trial basis. INTRODUCTION About 350–500 species of willow (Salix spp.), mainly growing in the Northern Hemisphere, currently exist worldwide (1).Willow is very rarely found in the tropics and in the Southern Hemisphere; it is completely absent in Australia and the Pacific region (2). In the Indian Himalayan region, 24 species of Salix are found (3). Out of these, 10 shrubby, indigenous species are Salix acmophylla Boiss., Salix daphnoides Vill., Salix denticulata Anderss., Salix flagellaris Anderss., Salix karelinii Turcz., Salix lindleyana Wall., Salix oxycarpa Anderss., Salix pycnostachya Anderss., Salix tetrasperma Roxb., and Salix wallichiana Anderss. Most of these are found growing wild in the moist places of the cold desert of Lahaul valley (4). S. denticulata, being an exception, is found along dry slopes. Willow is the main source of fuelwood, fodder, and minor timber (agricultural implements, handles of tools, poles, and roofing material). It also provides raw material for basketry (S. denticulata Andress.) The dry leaves of the plant are used for cushioning the floor of cowsheds. Not too long ago, utensils made of willow were quite common in a Lahauli’s kitchen. In the typically xeric, cold desert conditions, with high fluctuations of temperature (high in short summers and subzero during winters), very scanty rainfall, and high snowfall, only two species each of willow (Salix alba Linn. and Salix fragilis Linn.) and poplar (Populus balsamifera Linn. and Populus nigra Linn.) have adapted well to the climate of Lahaul and thrive better than all other species. S. fragilis, in particular, is cultivated extensively under the indigenous agroforestry and Ambio Vol. 35, No. 1, February 2006 forestry systems around settlements (5, 6). Traditionally, propagation is done through the shoot plantation method. The trees are pollarded during winter for fuelwood and fodder after an interval of 3–4 y. Bark of the branch cuttings is peeled off and given to cattle during winter as a substitute for green fodder. A large number of sprouts, called coppices, appear on the head of pollarded trunk during spring. Willow (S. fragilis), a deciduous, multipurpose plant, is most suitable for the dry temperate region because it grows gregariously along the riverbanks and the fields and also on steep slopes and erosion prone areas. This plant, as a source of renewable energy under cold desert climatic conditions, was supposed to be one of the best tree species for forestry programs, but the drying up of these trees, particularly above an altitude of 3000 m, has put a big question mark on its suitability. The present study examined the production of fodder and fuelwood from willow (S. fragilis) and the causes of its drying up in the cold desert of Lahaul valley. MATERIAL AND METHODS Study Area and Climate The cold desert of Lahaul and Spiti districts extends between 31844’34’’ N and 32859’57’’ N latitude and 76846’29’’ E and 78841’34’’ E longitude. The northern and southern boundaries of Lahaul valley are demarcated by the Great Himalayan range in the north and the Pir Panjal range of the Lesser Himalaya in the south. The total geographical area of the Lahaul valley is 6244 km2, and its population is 22,545. An average of 4 people km
2 inhabit the Lahaul valley (7). During winters, the Lahaul valley remains cut off from the rest of the country due to heavy deposits of snow on the Rohtang Pass (3978 m). The valley is accessible only during summers after the clearing of the snow from the pass. The Lahaul valley extends from Khoksar in the southeast to Tindi, near Udaipur town, in the northwest. Geographically, the Lahaul valley is made of three major subvalleys: Chandra, Bhaga, and Pattan. The width of the valley varies from 0.5 km to 2.0 km and the expansion of the rivers is 20 to 75 m. The Lahaul valley has a barren landscape (Fig. 1) with about 68.7% of the total geographical area falling under the nonreported category. That land category includes high hills, stony outcrops, and snowbound areas (8). The remaining 31.3% of the area comes under the reported category and includes the following subcategories of land use: forests (17.55%), land not available for agriculture (0.32%), permanent pastures (13.05%), area under tree plantations (0.01%), barren land (0.04%), currently fallow (0.01%), and net sown area (0.33%). Only 0.39% of the land is devoted to agriculture/ forestry use (i.e. forestry, barren land, current fallow, and net sown area). The valley has very few patches of relict pencil cedar (Juniperus macropoda Boiss) forests on the south-facing slopes. The north-facing slopes, on the other hand, have smaller Ó Royal Swedish Academy of Sciences 2006 http://www.ambio.kva.se 43 Figure 1. Willow plantation near Jahlma village, the Lahaul valley. Photo: S.C.R. Vishvakarma. patches of birch (Betula utilis D. Don), blue pine (Pinus wallichiana A.B. Jackson), and cedar [Cedrus deodara (Roxb. Ex D. Don) G. Don] growing along with different species of willow, particularly in the moist places. The permanent pastures serve as summer grazing grounds for the cattle, sheep, and goats of locals and gaddis (migratory shepherds). The elevation of this geographical entity ranges from 2400 to 6400 m above mean sea level. The high-altitude mountains remain covered with snow throughout the year. Some alpine pastures and a few scattered tree species are found in areas below the snow line. Agriculture, in the valley, is done on terraced fields. In large parts of the valley, willows and occasionally poplar trees are cultivated along the margins of the terraces under the indigenous agroforestry system. In the Pattan subvalley, however, fruit trees, such as walnut, plum, and peach, are also cultivated. Seabuckthorn bushes and understory are also found in smaller patches on the interspaces of the terraces, particularly in those parts of the fields through which the irrigation channel passes. In villages like Khoksar, which are above 3000 m, pollarding of the willow is done after an interval of 4 y, whereas for villages below 3000 m, it is done after 3 y. Tender branches, up to the thickness of 1 cm, along with the peelings of bigger branches are given to the cattle, sheep, and goats as green fodder. In the Lahaul valley, cash crops, such as peas (Pisum sativum Linn.), potatoes (Solanum tuberosum Linn.), and hops (Humulus lupulus Linn.), introduced some years back, are cultivated in large areas. Only a small area is devoted to the less-preferred, traditional food crops like barley (Hordeum vulgare Linn.), wheat (Triticum aestivum Linn), maize (Zea mays Linn.), varieties of buckwheat (Fagopyrum esculentum Moench. and Fagopyrum tataricum Linn.), and medicinal plants such as kuth [Saussurea costus (Falc.) Lipsch.] and manu (Inula racemosa Hk.f.) (9–12). The agricultural activities begin in April each year, soon after snow melts from the fields. The snow and avalanches cause much damage to the terraced fields and also cause heavy leaching of the soil nutrients every year. As a result, for sustained cropping in the region, a large quantity of organic manure is required. But with fodder scarce in the area, it is not possible to raise a large number of domestic animals that can produce an adequate supply of organic manure; therefore, the locals recycle night soil as manure to meet the large demand for manure in the fields. The traditional toilets, which are attached to the living rooms in the second floor of the house are specially designed to facilitate the collection of night soil for subsequent use as manure (10). 44 The participation of the tribal women in the agricultural activities is far greater than that of men. Except for plowing, which falls in the male domain, all other tasks are performed by the women. In the extremely dry soil conditions, ensured irrigation is a must for successful cropping. The inhabitants have, for this purpose, developed a community-based irrigation system that is very effective. Each family puts in 15 person–days of work each year to make this system a success. To this end, water is carried from the snowbound peaks to the fields below through kuhl channels of mud that are locally called kuhls (10). The extreme climatic conditions of the valley allow only one cropping season in a year, during the short summer. Cash crops, like potatoes, peas, and hops, and mixed local cultivars are cultivated during this season. Cash crops are harvested and exported from the valley between September and November. The farmers sell their pea crop to the merchants from New Delhi, India. Similarly, hops are sold to the breweries through intermediaries who are also nonlocals (from outside the region). Potatoes are harvested late and are sold through the Lahaul Potato Society (LPS), a farmers’ cooperative society in Manali, India, which sells the entire collected produce throughout the country. It pays the farmers after the sale is completed. The LPS also ensures the supply of provisions and other essentials to the farmers before the onset of winters and the closure of the Rohtang Pass. In some of the villages situated at lower altitudes, two crops are sometimes harvested. For instance, in Jahlma and Hinsa village, immediately after the pea harvest, in early September, buckwheat, mustard, and winter peas are sown. These crops are then harvested in late November. The yield from these off-season crops is very small and is meant only for domestic consumption. In fact, the main aim behind this offseason cropping is to get much-needed winter fodder for the livestock population. Climatically, the Lahaul valley is in the cold arid zone. It has very low rainfall and high snowfall; the winters are long and very severe. At the district headquarters, Keylong, the average annual rainfall during the months of June and July, is 25 mm, and the average snowfall, recorded between November and May, is 4500 mm. The average annual maximum temperature is 18.48C with a high of 26.78C in July and a low of 6.18C in February (Fig. 2). The average annual minimum temperature is
4.78C. The highest temperature was recorded in August, whereas the lowest temperature (
17.88C) was in February. In Khoksar, the lowest recorded minimum temperature during severe winters was
408C. Traditional Shoot Plantation Techniques Heavy snow deposits, the resulting frostbite, and the sliding of snow do not allow sapling plantations to survive in the cold valley of Lahaul. The traditional shoot propagation technique is, therefore, the most suitable method in such situations. Shoot cuttings of 3 to 4 y old, 2.4 to 3.0 m in length, and 5.6 to 6.3 cm in diameter are selected for this purpose. Three to five such shoots are tied together and planted in March and April as a single planting material in a pit 75 cm deep by 45 cm wide. These newly planted shoots, called pombut in the local dialect, start sprouting within a month. Some shoots that fail to sprout, are taken out and kept aside for making arthi (a bier, i.e. a ladder-like wooden frame used to carry a dead body for cremation). To protect planted cuttings from grazing animals, the shoots are either wrapped in gunny sacks or covered with the thorns from locally growing bushes such as the seabuckthorn (Hippophae rhamnoides) and the wild roses (Rosa macrophylla and Rosa webbiana) (Fig. 3). To protect the new plantation from sliding snow, a support of stones is erected at ground level in the lower part (downslope) of the pit. The new Ó Royal Swedish Academy of Sciences 2006 http://www.ambio.kva.se Ambio Vol. 35, No. 1, February 2006 Figure 2. Temperature and precipitation, the Lahaul valley, a cold desert in the northwestern Himalayas, plantations are irrigated regularly by watering them for 2–5 hr at weekly intervals; this is done at least 15–20 times during the summer season. If the plantation is on steeper slopes, a circular pit (about 75 cm in diameter and about 30 cm deep) is prepared upslope at a distance of 50 cm from the plantation. This helps keep the soil moist for longer periods by harvesting water from the snow melting uphill. The first pollarding of the planted willows is done after 3–4 y; in the high altitude villages like Khoksar, pollarding is done in the fourth year of planting, whereas in the rest of the villages, it is done in the third year. Pollarding is done at a height of 2.5 m above ground level to prevent the grazing animals from causing damage to the new sprouts. Pollarding is done in the winter months between November and December and provides precious fuelwood and fodder (Fig. 4). Farmers who have many trees, pollard their trees in two cycles; first in the beginning of winter (November–December) and again at the end of winter (February–March). When pollarding healthy trees, four to five coppices are left on top of the main trunk. These are harvested later, between March to April, for raising new plantations. The annual pruning of the branches on the lower part of the trunk is a common, widespread feature in the valley during summer. Smaller twigs are separated for fodder, and thicker branches are kept for fuelwood. All these branches are stacked close to the houses. The bark from thicker branches is peeled off and used to feed the livestock. New sprouts on the pollarded trees appear in March–April, depending on the age of the tree, its size, and Figure 3. Traditional willow shoot-cutting plantation. Photo: S.C.R. Vishvakarma. Ambio Vol. 35, No. 1, February 2006 Figure 4. Pollarding of willow trees, Jahlma village. Photo: Y.S. Rawat. its altitude, and the number of coppices range from 150 to 500 coppices tree
1. The maximum number of coppices emerges in the first year after pollarding; their number progressively declines over the subsequent years. Once a tree develops a large head (the apical part of the trunk where coppices emerge), only very few coppices are produced. After 10–15 y of pollarding, the large head is removed, in the months of February–March, for use as fuelwood. A large head not only produces very few coppices, which dry quickly, but also accumulates much snow and, thereby, becomes prone to uprooting. The life span of a willow tree, in this cold desert region, is about 150 y. However, the trunk starts becoming hollow after 60–80 y, and the resulting fodder and fuelwood production begins to decline. Data Collection The area under the traditional agroforestry systems at Khoksar, Jahlma, and Hinsa villages was divided into quadrates of 10 3 10 m using the line transect method. Three line transects were laid along the slopes, and the vegetation in each was analyzed. The number of trees, their diameter, and their occurrence was recorded. Density, basal area, and the importance value indices (IVI) were calculated for all the species growing therein. The production of fuelwood and fodder from willow trees was obtained immediately after pollarding by the direct weighing method. Oven dried weight at 808C was considered final. The percentage contribution of willow toward the total fuelwood and fodder requirements of the villagers was estimated by dividing total fuelwood production from the willow by the total requirement of fuelwood at the village level and multiplying the result by 100. Similarly, the contribution of the willow toward fodder was also estimated. It was observed that the drying up of the willow trees was more common in the villages located above an altitude of 3000 m. Therefore, the data for drying willow trees were collected for Ropsang (3160 m), Khorpani (3160 m), and Khoksar (3200 m) villages. The willow trees of each individual village were counted and grouped into three categories: green, drying, and dry. To identify the agents causing the drying up of the willows, samples of insects and dry branches were collected. The scientists at Dr. Y.S Parmar Ó Royal Swedish Academy of Sciences 2006 http://www.ambio.kva.se 45 University of Horticulture and Forestry in Nauni, Solan, India, provided help in identifying the causal organisms. RESULTS AND DISCUSSION The important agroforestry species in the Lahaul valley are S. fragilis, H. rhamnoides, Juglans regia, Populus nigra, Prunus armeniaca, Prunus cornuta, and Prunus communis (Table 1). At Khoksar, S. fragilis and P. nigra are grown extensively. The density and IVI of S. fragilis were 2.90 and 272.26, respectively; these values for P. nigra were 0.30 and 27.54, respectively. In Jahlma, the trees, in order of their importance, were H. rhamnoides, S. fragilis, P. nigra, J. regia, and P. armeniaca. In Hinsa village, S. fragilis was relatively higher in density (0.60) than H. rhamnoides (0.40). The density of all other plants, Crataegus songarica, J. regia, P. nigra, P. armeniaca, P. communis, and P. cornuta, was quite low. In Hinsa region total density (43.78%) and IVI (40.06%) of Salix fragilis were higher than H. rhamnoides. In general, at Jahlma and Hinsa, S. fragilis and H. rhamnoides were important species, whereas at Khoksar, S. fragilis and P. nigra were the important species. The average fuelwood production per tree was highest at Hinsa (240 kg tree
1). That was followed by Jahlma (213 kg tree
1), and the lowest production was at Khoksar village (110 kg tree
1) (Table 2). Fodder from the bark of willow and its tender twigs was also highest at Hinsa (21.5 kg tree
1), followed by Jahlma (20.5 kg tree
1), and Khoksar (15.3 kg tree
1). Khoksar, being the highest village, is colder than either Hinsa or Jahlma; its lower temperature and shorter growth period are the reasons for the relatively lesser biomass production. S. fragilis is a major contributor of fuelwood and fodder under the agroforestry system at Khoksar. The willow trees are also cultivated under the forestry system around the villages. The fuelwood obtained from willow varies from village to village depending on the number of the trees and the village’s climatic conditions. At Khoksar village, 29% of the total annual fuelwood requirement of the villages comes from the willow. At Jahlma and Hinsa, willow’s contribution to the total fuel use was 69.5% and 42%, respectively (Table 3). Khoksar village is situated in a narrow valley and, as compared with Jahlma and Hinsa villages, has a smaller area under agroforestry and forestry systems. Therefore, unlike Jahlma and Hinsa villages, there are fewer willow trees at Khoksar. The remaining 71% of the fuelwood requirement at Khoksar is met from locally grown poplar trees and fuelwood supplied by the Depot of the Forest Corporation situated in the adjoining district of Kullu. Some wood obtained illegally from the relict patches of birch (Betula utilis) and bushy Juniper (Juniperus communis Linn. var. saxatilis) also contributes to the fuelwood requirement of the villagers at Khoksar. Jahlma village, however, has a large area of willow cultivated under the forestry and agroforestry systems; therefore, the contribution of willow to the fuelwood and fodder at Jahlma was very high in comparison with other species. Only 31.5% of fuelwood requirement of the Jahlma village came from sources other than willow such as seabuckthorn, poplar, pencil cedar, or the Depot of the Forest Corporation. The north-facing slopes of Hinsa village have a good forest cover of cedar (C. deodara), blue pine (P. wallichiana), Rai (Abies pindrow), and birch (B. utilis). Some wild willows, growing in the moist patches, are also found here. People in this village, therefore, harvest fuelwood from the forests. The contribution of willow toward the fodder requirement of the villagers was the highest for Hinsa village, where it was 24.5% of the total requirement, which was followed by Jahlma (23.7%) and Khoksar (13.3%) villages. The remaining portion of the fodder requirement was met with hay obtained from the cultivated grasslands, the husk of grains and the vegetative parts of the pea, potato, and hop crops. After the crops are harvested, the cattle, sheep, and goats are allowed to graze openly in the fields, which ensures that all consumable plant parts are fully used in this fodder-scarce region, before the fields are covered with winter snow. In the villages situated above an altitude of 3000 m, fungal infection of Cystospora chrysosperma (Pers.:Fr.) Fr. is quite Table 1. Diversity and density (10x10 m2) of tree species found under indigenous agroforestry system of cold desert of the Lahaul valley in northwestern Himalaya. Scientific name Crataegus songarica C.Koch Hippophae rhamnoides L. Juglans regia L. Populus nigra L. Prunus armeniaca L. Prunus communis Huds. Prunus cornuta (Wall ex. Royle) Steud. Salix fragilis L. Vernacular name Khoksar (3200 m) Jahlma (3000 m) Hinsa (2700 m) Ramjak Chharma Akhrot Safeda Khubani Plum Kurun Beli — — — 0.30 — — — 2.90 — 1.93 0.03 0.03 0.02 — — 1.22 0.07 0.40 0.07 0.10 0.07 0.03 0.03 0.60 Table 2. Density of Salix fragilis and its fodder and fuelwood production under indigenous agroforestry systems in the cold desert of the Lahaul valley. Attributes 1. Total number of species 2. Total density (10 3 10 m2) 3. Density of Salix fragilis 4. IVIz of Salix fragilis 5. Fuelwood production  Per tree (kg tree
1)  Per hectare (t ha
1) 6. Fodder production  Per tree (kg tree
1)  Per hectare (t ha
1) Khoksar* Jahlma Hinsa 2 3.20 2.90 272.26 5 3.23 1.22 146.80 8 1.44 0.66 120.20 110.00 6 20.8 31.90 6 6.04 213.30 6 20.5 26.02 6 2.26 240.0 6 15.8 14.40 6 1.58 15.30 6 1.60 4.44 6 0.46 20.5 6 1.9 2.50 6 0.23 21.5 6 2.1 1.29 6 0.13 * Pollarded after a 4-y interval. Pollarded after a 3-y interval. z IVI ¼ importance value indices. 46 Ó Royal Swedish Academy of Sciences 2006 http://www.ambio.kva.se Ambio Vol. 35, No. 1, February 2006 Table 3. Contribution (%) of Salix fragilis to the total fodder and fuelwood requirements at village level in the cold desert of the Lahaul valley. Attributes Khoksar Jahlma Hinsa 1. Fuelwood  Agroforestry  Forestry  Total 18.5 10.5 29.0 20.0 49.5 69.5 14.4 27.6 42.0 2. Fodder  Agroforestry  Forestry  Total 8.5 4.8 13.3 6.8 16.9 23.7 8.4 16.1 24.5 rampant in the willow. The infection is causing large-scale drying up of the willow trees (13). In the villages of the Chandra subvalley, the drying of the trees was most devastating in the year 2003. At Ropsang, 80% of the trees have dried up. For in the willow Khoksar and Khorpani villages, 60% and 25%, respectively of the trees were dried out (Table 4, Fig. 5). A dried tree neither sprouts nor recovers. On average, nearly 14.8% of the total trees were drying up, and only 30% were in a healthy state. Few trees were infected by the fungus below an altitude of 3000 m. Pattan and Bhaga subvalleys of Lahaul, which are below 3000 m, recorded very few cases of the fungal infections. Willow trees become susceptible to infection by Cytospora chrysosperma when they are cultivated outside their normal Figure 5. Dried willow trees at Khoksar village. Photo: S.C.R. Vishvakarma. range and also when they are exposed to unfavorable conditions, which include extremely severe winters causing frost damage, poor sites, long periods of drought, heavy pollarding or other such mechanical injury, damage by root-feeding nematodes and other insects, and damage or infection by other pathogenic fungi (14). The wild species of willow, growing in the Khoksar area, were found to be free of this fungal infection. These plants, such as S. lindleyana, a creeping shrub; S. karelinii, a shrub found along with birch trees; and a few trees of S. acmophila, were absolutely healthy. These wild species are not only free from Cytospora chrysosperma infection but also free of any aphid infection. Obviously, these wild species are well adapted to the extreme climatic conditions of the valley and have developed resistance to the infections. Disease was found only in the cultivated willows (S. fragilis). This species was introduced about 150 y ago; the present plantations, obtained by repeated shoot propagation, trace their ancestry back to these first plants. The physiological system of these trees, over the years, has weakened considerably, and they have become prone to attack from insects and pests, particularly under the extremely harsh climatic conditions of the valley (extremely xeric, with prolonged subzero temperatures down to
408C). Infestation by giant willow aphids and scale insects increase the trees’ susceptibility to quick and massive infections of Cytospora chrysosperma; and the result is the large-scale drying up of the trees. Giant willow aphid [Tuberolachnus salignus (Gmelin)], a sapsucking aphid, is a severe pest on cultivated willows and has infested 70–80% of the total trees found between 3000 and 3500 m of altitude, particularly those growing in moist areas. Debilitation or death of 5–10% of the aphid-infested trees, every year, is quite common (15) (Table 5). In the month of October, 60-80% of the trees infested with aphids produced 3.87 6 0.9 kg of edible raw honeydew, which is sometimes consumed by the children in the villages (16). As reported by Choudhury (17), under the moderate infestation and subsequent honeydew production, nutrient mineralization is enhanced. Continuous attack during the second and third years, however, reduces the Table 4. Status of willow trees in the cold desert of the Lahaul valley, northwestern Himalayas in 2003. Attributes Khoksar (3200 m) Ropsang (3160 m) Khorpani (3160 m) Average 502 13.6 26.1 60.4 17 650 6.5 13.3 80.2 2000 70.0 5.0 25.0 30.0 6 20.1 14.8 6 6.1 55.2 6 16.1 Total trees (nos.) Green (%) Drying (%) Dried (%) Table 5. Insect and pathogen attack on willow trees in the cold desert of the Lahaul valley in the northwestern, Himalayas. Pathogen/Insect Tuberolachnus salignus (Gmelin) Quadraspidiotus perniciosus (Comstock) Cytospora chrysosperma (Pers.:Fr.) Fr. Ambio Vol. 35, No. 1, February 2006 English name Nature of damage Giant willow aphid San Jose scale insect Fungus Sap loss and honeydew leaching. Causes rapid fungal infections. Sap loss under heavy infestation. Young trees die. Tree death under severe infection. Ó Royal Swedish Academy of Sciences 2006 http://www.ambio.kva.se 47 growth and vigor of the plants, and the trees become susceptible to fungal infections, snow injuries, and canker due to the fungus (Nectria sp.). Plants under repeated attack by aphids and canker die after 3–5 y of the infection (15). Trunks of heavily infested trees appear white because of the heavy deposit of eggs, and all such trees die very quickly. CONCLUSION Willow is a highly useful tree both for fodder and fuelwood in the cold deserts and high altitude locations of the Himalaya. Because the drying up of the trees is more common in the areas above an altitude of 3000 m, selection of a proper replacement species that is well adapted to the extreme climatic conditions is important. Disease-free species of willow growing in the wild state and Salix babylonica can be introduced on a trial basis. S. babylonica is well-established as a species used for fodder and fuelwood and is cultivated in the temperate regions of Bhutan Himalaya (18). Some trees of this species, found in the Lahaúl valley, are in a healthy state. Therefore, this species has a better chance of becoming a successful replacement for S. fragilis. But before a final decision is made, the tree should be introduced on a trial basis in different parts of the valley under the varying climatic conditions of the different altitudes. References and Notes 1. Argus, G.W. 1999. Classification of Salix in the New World. Bot. Electron. News 227, 6 p. 2. Hooker, J.D. 1885. The Flora of British India. Vol. V. 1992, Reprint 1992. Bishen Singh Mahendra Pal Singh (BSMPS), Dehradun, pp. 1–910. 3. Troupe, R.S. 1986. The Silviculture of Indian Trees. Vol. III. Ravendrapal Singh Gahlot, International Book Distributors, Dehradun, pp. 951–957. 4. Aswal, B.S. and Mehrotra, B.N. 1994. Flora of Lahual-Spiti: A Cold Desert in North West Himalaya. Bishen Singh Mahendra Pal Singh (BSMPS), Dehradun, pp. 10–15. 5. Singh, G.S., Ram, S.C. and Kuniyal, J.C. 1997. Changing traditional land use patterns in the Great Himalayas: a case study of Lahaul Valley. J. Environ. Sys. 25, (2), 195–211. 6. Kuniyal, J.C., Vishvakarma, S.C.R. and Singh, G.S. 1997. Ecological impacts of cash crops in Cold Desert of Lahaul Valley in North West Himalaya. Envis Bull. Himalayan Ecol. Devel. 5, (2), 6–9. 7. Anonymous. 2001. Census of India 2001. Provisional Populations Totals, Part 2. Director of Census Operations, Government of Himachal Pradesh, Shimla. 8. Anonymous 1995. Statistical Handbook: Tribal Area, Himachal Pradesh, Department of Economics and Statistics, Government of Himachal Pradesh, Shimla, India, pp. 1–70 (In Hindi). 9. Kuniyal, C.P., Vishvakarma, S.C.R., Kuniyal, J.C. and Singh, G.S. 2002. Seabuckthorn (Hippophae L.)—a promising plant for land-restoration in the cold desert Himalayas. In: Proceeding of International Workshop on Seabuckthorn. Singh, V. and Khosla, P.K. (eds.). 18–21 February, New Delhi. pp. 1–6. 10. Kuniyal, J.C., Vishvakarma, S.C.R. and Singh, G.S. 2004. Changing crop biodiversity and resource use efficiency of traditional versus introduced crops in cold desert of northwestern Indian Himalaya: a case of Lahaul valley. Biodivers. Conserv. 13, (7), 1271–1304. 11. Rawat, Y.S., Oinam, S. S., Vishvakarma, S.C.R. and Kuniyal, J.C. 2004. Saussurea costus (Falc.) Lipsch: a promising medicinal crop under cold desert agro-ecosystem in northwestern Himalaya. Indian J. For. 27, (3), 297–303 12. Kuniyal, C.P., Rawat, Y.S., Oinam, S.S, Kuniyal, J.C. and Vishvakarma, S.C.R. 2005. Kuth (Saussurea lappa) cultivation in the cold desert environment of the Lahaul Valley, northwestern Himalaya, India: arising threats and need to revive socio-economic values. Biodivers. Conserv. 14, (5), 1035–1045. 13. Khosla, K., Sharma, I.M. and Kumar, M. 2003. Occurrence of Cytospora canker on willow in the Lahaul valley and its management. In: International Conference on World Perspectives on Short-Rotation Forestry for Industrial and Rural Development. 7–13 September. Dr. Y.S. Parmar University of Horticulture and Forestry and Indian Society of Tree Scientists, Himachal Pradesh, p. 203. 14. Anonymous 1990. Cytospora Canker of Poplar and Willows: Report on Plant Disease, RPD No. 661, Department of Crop Sciences, University of Illinois at UrbanaChampaign, Urbana, pp. 1–5. 15. Sharma, G.C. and Thakur, J.R. 1995. The giant willow aphid, Tuberolachnus salignus (Gmelin), a serious pest of Salix sp. in Spiti valley of Himachal Pradesh. J. Aphidology. 5, (1–2), 86–89. 16. Sharma, G.C., Thakur, J.R., Kashyap, A.S. and Joshi, V.K. 1995. Giant willow aphid, Tuberolachnus salignus (Gmelin), a producer of nutritious honey food in dry temperate zone of Himachal Pradesh. J. Insect Sci. 8, (1), 110–111. 17. Choudhury, D. 1988. Herbivore induced changes in leaf litter resource quality: a neglected aspect of herbivory in ecosystem nutrient dynamics. Oikos 51, (3), 389–393. 18. Roder, W. 1992. Experiences with tree fodders in the temperate regions of Bhutan. Agrofor. Sys. 17, 263–270. 19. The authors are thankful to the Director, G.B. Pant Institute of Himalayan Environment and Development, Kosi-Katarmal, Almora, for providing necessary facilities. The authors are grateful to two anonymous referees for their valuable comments and suggestions, which helped a lot in improving the quality of this research paper. The financial support for the present work was provided by the Ministry of Environment and Forests, Government of India, New Delhi. 20. First submitted 15 March 2004. Accepted for publication 21 March 2005. 48 Yashwant S. Rawat is a Senior Research Fellow at G. B. Pant Institute of Himalayan Environment and Development. His research interests include cold desert agroforestry, forestry systems, and socio-cultural aspects of people of cold desert area. His address: G. B. Pant Institute of Himalayan Environment and Development, Himachal Unit, Mohal-Kullu, 175 126, Himachal Pradesh, India. yas_rawat@yahoo.com Santaram S. Oinam is a Senior Research Fellow at G. B. Pant Institute of Himalayan Environment and Development. His research interests include geomorphology and agriculture geography. His address: G. B. Pant Institute of Himalayan Environment and Development, Himachal Unit, Mohal-Kullu, 175 126, Himachal Pradesh, India. oinamsantaram1@rediffmail.com Subhash C. R. Vishvakarma is a senior scientist at G. B. Pant Institute of Himalayan Environment and Development. His research interests include agroforestry, forest management, tourism in hilly environment, indigenous irrigation systems, and natural resource management. His address: G. B. Pant Institute of Himalayan Environment and Development, KosiKatarmal, Almora 263 643 Uttaranchal, India. scrvishvakarma@hotmail.com. Chandra P. Kuniyal is a scientist at the Herbal Research and Development Institute. His research interests include ecophysiology and biochemistry of medicinal herbs. His address: Herbal Research and Development Institute, GopeshwarChamoli, 246 401, Uttaranchal, India. cpkuniyal@@rediffmail.com. Jagdish C. Kuniyal is a scientist at G. B. Pant Institute of Himalayan Environment and Development. His research interests include agriculture geography, solid waste management, and tourist and air pollution in hilly environment. His address: G. B. Pant Institute of Himalayan Environment and Development, Himachal Unit, Mohal-Kullu, 175 126, Himachal Pradesh, India. jckuniyal@hotmail.com. Ó Royal Swedish Academy of Sciences 2006 http://www.ambio.kva.se Ambio Vol. 35, No. 1, February 2006