Final Added Vol 15-2.pmd 19 Monitoring growth of Uttis (Alnus nepalensis) at a plantation cite at Dhankuta, Nepal T. P. Barakoti1 A long-term growth monitoring experiment on Uttis (Alnus nepalensis) was conducted in the permanent sample plots of the Agricultural Research Station (ARS) Pakhribas, Dhankuta for 10 years (1992-2001). The average annual increment was diameter at breast height 2.14 cm in 8th year, and was 0.13 cm at 16th year of planting. The trees grew 44 cm to 130 cm per year irrespective of the age. The highest growth rate correspondend with higher rainfall during summer (March-April). Estimated biomass of stem and branches increased by 2-2.5 times within the 10 years period. Thinning and felling every year indicated need for timely management of the plantation to provide better growing environment. The data would be useful for growth modelling and proper management of Uttis plantation in Nepal . Key words: Nepalese alder vs Uttis, height, diameter, biomass, Pakhribas. Alnus nepalensis commonly known as Uttis inNepal, few par ts of India, Pakistan and Bangladesh, is an important multipurpose tree species. It grows in the cooler and moist areas of the northern temperate region of South-East Asia, China, Japan, and in South America. In Nepal, it is distributed from 900 to 2700 m (Lamichhaney, 1995) above sea level associated mainly with Prunus and Saurauria sp. in higher elevation and with Schima and Castanopsis sp. in the lower elevation. It is a pioneer species of degraded lands and is moderately shade tolerant (Storrs and Storrs, 1984) and colonizes well in gravel slip prone slopes (Jackson, 1987). As a nodule- for ming non-legume, it has the ability to fix atmospheric nitrogen and improve soil. Its leaf alone can add 100 kg N ha-1yr-1 to the soil (Postgate, 1978). Endemic to Nepal (Burley and Stewart, 1985) and other mountain countries, Uttis is one of the most preferred forest tree species by the hill communities. It is fast growing, commonly used for fuel-wood, timber, furniture and leaf litter. It is also used for fodder and shade to large cardamom (Ghimire, 1985) and teas (PAC, 1985) in the eastern hills and for industrial purposes (ply, match, tanning, chest for tea etc). According to PAC (currently ARSP) annual record (1995), Uttis accounted for more than 50 per cent of the tree seedlings distributed from Pakhribas forest nursery for planting in the Koshi hills. Over the past 25 years, this species has been extensively planted throughout Nepal (Lamichhaney, 1984 and 1995). In spite of extensive plantings, there is little information on silvicultural management of this species. There is no record on thinning regimes or appropriate final plant spacing (Lamichhaney, 1995). Therefore, to quantify growing rates on yearly basis, need of a long-term growth monitoring trial was felt and that was established for regular measurements. The information is useful for community forest users and forest managers in planning and management of Uttis in private and community forests. Such information will enable estimation of current annual increment, mean annual increment and to derive suitable rotations. Materials and methods The permanently established (planted in 1984 at 2x2m in collaboration of Forest Research Division) sample plots of Uttis (Alnus nepalensis, D. Don) in the north farm of ARS Pakhribas, Dhankuta at the elevation of 1900 m was used for growth monitoring trial. Three squared plots of 32 m x 32 m (0.1 ha) were selected and laid-out in February 1992. Block I and block III were located in slops, south facing, in upper and lower part or elevation respectively. Block II was in moderately slop between the above blocks but it was facing southeast. The trees within the boundaries and edge trees in the plots were marked and demarcated. Location map and plot chart showing each tree and identity number, site description (altitude, topography, slope, drainage, soil texture, natural vegetation etc.) of each plot developed. 1 Senior Scientist, Agricultural Research Station Pakhribas, Dhankuta. 20 Periodic measurements (once every year in January) of diameter, and tree height were carried out in the trial blocks. Diameter at breast height (DBH) measured over bark for all trees in each block (replication), while top heights were measured in 10 fattest selected trees/ block. DBH was measured before felling. The number of standing trees and felled trees are given in Annex 1. Height of trees and girth of logs were measured and wood yield was estimated. Volume was calculated on the basis of mid-diameter of 3m logs. The biomass of the harvested trees was also recorded. The data on major parameters were taken since 1992 and continued for 10 years. Fresh weight was converted into dry weight by multiplying with 0.41-a relationship derived by Levenson (1979): Y = 3.87 + 0.26 a, Where, y = dry weight yield (kg), and a = dbh2 (cm). Similarly, volume of stem was calculated according to volume equation (Sharma and Pukkala, 1990): Ln (V) = (a+b) ln (dbh) + c x Ln (h), Where V is total stem volume with bark (dm3 ), a = -2.7761, b = 1.9006, and c = 0.9428 d is diameter (in cm) and h is height (in m). The number of stock trees and removed trees in each block was recorded every year. Up to 50% trees based on height, canopy close, DBH and density were thinned. Permanent ring was painted in each tree at the breast height. Renumbering was also done where necessary. The tree growth rate and ratio were calculated every year. In 1995, the bushes were partially cleared as there was difficult to move and take measurements. Tree height and DBH were measured that year in mid February only. In 1999, data were taken one week later than previously (first week of February). Results and discussion The major growth parameters like diameter and height were recorded from 1992 to 2001 and presented in Table 1 and Table 2 respectively. Diameter at breast height-The average DBH increased from 17.23 to 28.00 cm over the ten years period (Table 1). The DBH was measured in all trees selected in each block. The average increment rate was from 0.13 to 2.14 cm (Table 1). The higher rates were during the initial period, when the trees were small. The data showed that Uttis trees had gradual increase up to the final year of observation (2001), however the differences were found in decreasing trend. Average tree height - The average height of Uttis varied from 15.73 to 22.40 m over the 10 years. Likewise, the average increment rates or differences were 0.44-1.30 m for different years (Table 2). The trees attained 5 to 6m during the 9 years period. Unlike diameter, growth rates found higher during later period than the initial period. The heights were measured in the same 10 fattest trees, where the DBH were measured. The detail of measurement record is given in Annex 2. According to 1995 records, average number of trees ha-1 after thinning was 673.8, 546.9 and 439.5 in Block I, II and III respectively. Normal stand is considered to 900 trees ha-1 after thinning. A closer spacing might give a higher yield. The biomass was calculated based on the given table (Kharel and Mulder, 1984). Biomass of stem, branch and leaf are estimated separately (Table 3). The data revealed that stem and branches could produce similar yield (around 40 kg tree-1 each at 8th year and above 100 kg tree-1 in 16th year of planting). Leaves had Table 1. Average diameter increment from 1992 to 2001 North Farm, ARS Pakhribas, Dhankuta DW� WKH� EUHDVW� KHLJKW�� 5HQXPEHULQJ� ZDV� DOVR� GRQH� ZKHUH� QHFHVVDU\�� 7KH� '%+� WDNHQ� LQ� PLOOLPHWHU� SUHYLRXVO\� ZHUH� FRQYHUWHG� LQWR� FHQWLPHWHU� DV� YHUEDOO\� VXJJHVWHG� E\� 'U� $PDW\D� �������� 7KH� WUHH� JURZWK�UDWH�DQG�UDWLR�ZHUH�FDOFXODWHG�HYHU\�\HDU��,Q�������WKH�EXVKHV�ZHUH�SDUWLDOO\�FOHDUHG�DV�WKHUH� ZDV�GLIILFXOW�WR�PRYH�DQG�WDNH�PHDVXUHPHQWV��7UHH�KHLJKW�DQG�'%+�ZHUH�PHDVXUHG�WKDW�\HDU�LQ�PLG� )HEUXDU\�RQO\��,Q�������GDWD�ZHUH�WDNHQ�RQH�ZHHN�ODWHU�WKDQ�SUHYLRXVO\��ILUVW�ZHHN�RI )HEUXDU\��� 5HVXOWV�DQG�GLVFXVVLRQ 7KH�PDMRU�JURZWK�SDUDPHWHUV�OLNH�GLDPHWHU�DQG�KHLJKW�ZHUH�UHFRUGHG�IURP������WR������DQG�SUHVHQWHG� LQ�7DEOH���DQG�7DEOH���UHVSHFWLYHO\� 'LDPHWHU�DW�EUHDVW�KHLJKW�7KH�DYHUDJH�'%+�LQFUHDVHG�IURP�������WR�������FP�RYHU�WKH�WHQ�\HDUV� SHULRG���7DEOH�����7KH�'%+�ZDV�PHDVXUHG�LQ�DOO�WUHHV�VHOHFWHG�LQ�HDFK�EORFN��7KH�DYHUDJH�LQFUHPHQW� UDWH�ZDV�IURP������WR������FP��7DEOH�����7KH�KLJKHU�UDWHV�ZHUH�GXULQJ�WKH�LQLWLDO�SHULRG��ZKHQ�WKH�WUHHV� ZHUH�VPDOO��7KH�GDWD�VKRZHG�WKDW�8WWLV�WUHHV�KDG�JUDGXDO�LQFUHDVH�XS�WR�WKH�ILQDO�\HDU�RI�REVHUYDWLRQ� ��������KRZHYHU�WKH�GLIIHUHQFHV�ZHUH�IRXQG�LQ�GHFUHDVLQJ�WUHQG� 7DEOH����$YHUDJH�GLDPHWHU�LQFUHPHQW�IURP������WR����� 1RUWK�)DUP��$56�3DNKULEDV��'KDQNXWD� 'LDPHWHU��FP