174 P. D. DOGRA 



some trees at high altitudes (10,500 feet) bearing empty or half-filled 

 seeds. Seed-radiography, embryology, and chromosomal studies of higher 

 level blue pine may shed new light on the problem of half-filled or empty 

 seeds in dry or arid high-level blue pine populations (Dogra, 1967). 



PROVENANCES FROM EASTERN HIMALAYAS 



The eastern Himalayas experience the heaviest rainfall in India. 

 The blue pine in these regions can, therefore, be classed into three 

 provenances: wet lower- level, very heavy monsoon zone; moist upper- level 

 heavy monsoon zone; and dry high-level non-monsoon zone blue pine 

 provenances (Table 2) . 



WET LOWER-LEVEL, VERY HEAVY MONSOON ZONE BLUE PINE 



The wet lower-level, very heavy monsoon zone blue pine grows in 

 almost tropical to sub-tropical forests of approximately 4,000 to 6,000 

 feet altitude which experience an annual rainfall of 100 to 200 inches. 



These provenances are found in some regions of Assam. In Apa Tani 

 valley of Aka hills, blue pine experiences an annual rainfall of 200 inches 

 (Bor, 1938) as compared with 10 to 30 inches for blue pine of upper Sutlej 

 valley in the northwest. It grows in open forests on exposed grassy slopes 

 with bamboos and ferns. In Mishmi hills, it grows with Podocarpus nerii- 

 folius and bamboos {Arundinaria and Phyllostachys) on exposed grassy slopes 

 at approximately 4,920 feet altitude. Blue pine has been reported to 

 occur between the altitudes of 4,920 and 6,884 feet on grassy slopes of 

 Ngawchang, Taron, and Seinghku valleys in upper Irrawady of northern 

 Burma (Ward, 1944; Schweinfurth , 1957; Bor, 1953). In Bhutan the low- 

 level pine may be found at about 4,920 to 6,840 feet with an annual rain- 

 fall of over 100 inches. The blue pine of these regions therefore seems 

 to be well adapted to conditions of heavy summer rainfall. 



MOIST UPPER-LEVEL HEAVY MONSOON ZONE BLUE PINE 



Blue pine grows in the inner and comparatively drier valleys of 

 Bhutan and Assam in pure crop or mixed with Que reus 3 Juglans, Rhododendron^ 

 Cedrela } Larix> Taxus, Tsuga, and Vieea spp. Wallich (1832) mentions 

 blue pine growing in Bhutan to be larger in size than that of Nepal. Some 

 of these forests in Bhutan grow near the border regions of Bengal and 

 Assam from 8,500 to 10,500 feet altitude but they may descend to 7,000 

 feet. They form a belt from valleys of Amo to Manas in Bhutan and extend 

 slightly into West Assam. These areas show the best blue pine growth in 

 Eastern Himalayas (Fig. 1) . 



The moist higher-level heavy monsoon zone blue pine also appears to 

 grow from about 6,000 feet upwards in gorges of middle Po Tsangpo and Po 

 Yigrong which join Brahmaputra from the north and in the higher reaches 

 of its distribution in upper Irrawady region in Northern Burma (Ward, 

 1942, 1944; Schweinfurth, 1957). 



