Collaborative studies in tropical Asian dendrochronology: addressing challenges in climatology and forest ecology

Team Philippines investigated 452 trees spread in 226 indigenous tree species from 54 families of seed plants and, out of this, 898 corewood samples representing indigenous tree species are filed in the new UPLB xylaria. There were 40 species with distinct growth rings out of 226 tree species while those with indistinct and absent rings numbered, 134 and 52, respectively. There were also 13 exotic tree species (introduced or non-active), 6 of them had clear distinct rings. Initial results from pine and teak ring patterns show evidence of synchrony with EL Niño and La Niña events. Team Malaysia investigated 64 trees from 13 indigenous tree species. A total of 126 corewood samples have been filed in xylaria. All 4 coniferous tree species studied have distinct rings. Of the 9 lowland tree species investigated 2 had distinct rings. Hence, out of 13 tree species 6 registered with distinct growth rings. Team Thailand found 28 species with distinct growth rings out of 91 tree species, while 21 and 42 represent tree species with indistinct and absent rings, respectively. Team Sri Lanka investigated 142 trees spread in 65 tree species from 29 families. A total of 263 corewood samples were filed in xylaria. Team Sri Lanka found 16 species with distinct rings out of 65 tree species, 34 with indistinct rings and 15 absent rings. Team India found 12 species with distinct rings out of 29 total tree species investigated. This team had 257 corewood samples and 28 discs. Being advanced in the cross dating, the team emphasized on replicated sampling and drawing chronologies from Anogeissus latifolia, Albizia lebbeck, and Dalbergia latifolia. It is interesting that the chronologies from Team India and those from ring patterns of Philippine Benguet pine Pinus kesiya and of teak Tectona grandis in Carrangalan, Nueva Ecija [Philippines] agree with the Southern Oscillation Index. This means that the El Niño Southern Oscillation teleconnection can be reflected by crossmatching tree species in spite of the fact that these tree species are widely separated geographically.