บทคัดย่อ :
The major objective of this study was to investigate biology and factors affecting tree-ring formation of the selected species at Sakaerat Environmental Research Station (SERS) and Wang Nam Khiao Forestry Student Practice Station of the Faculty of Forestry (WNKFSPS). From 92 species, 6 tree species with one or both of the characteristics of presenting marginal parenchyma, showing distinct or abrupt anatomical changes at the growth ring boundary and composing of ring porous or semi-ring porous vessel arrangement were selected for the studies. The selected tree species composed of 4 deciduous species (Tectona grandis, Afzelia xylocarpa, Melia azedarach and Lagerstroemia duperreana) and 2 evergreen species (Aglaia odoratissima and Hydnocarpus ilicifolia). Monthly investingations of (1) tree phenology, (2) outside bark diameter increment from band dendrometer, and (3) wood increment and wood anatomy from cambial marking samples were done and related with climate and soil moisture contents to investigate biology and factors affecting tree-ring formation. False ring and annual ring characteristics of teak (Tectona grandis L.f.) were also investigated to explain major factors affecting their occurrences. Axial parenchyma and/or vessel size variation were the marked points of annual ring boundaries of T. grandis, A. xylocarpa, L. duperreana and M. azedarach while fiber cell wall thickness and flatted fiber were useful to identify the annual ring boundaries of L. duperreana, A. odoratissima and H. ilicifolia. Monthly wood increment of 4 deciduous trees initiated on the same periods of leaf flushing at the beginning of rainy season or a month later and cessation occurred during leaf abscission in dry and cold season at the end of the year. Wood increments of 2 evergreen trees were dormancy in dry periods at the end of the year, while leaf phenologies were abundantly found throughout the year. Outside bark diameters in all species rapidly increased in rainy season and illustrated the shrinkage in dry season. The climatic data of monthly temperature, rainfall, relative humidity and soil moisture which were transformed to the components of moisture (rainfall, relative humidity and soil moisture content) and temperature (maximum, minimum and mean monthly emperature) illustrated both of direct and indirect relationship with wood increment of all tree species, except A. odoratissima. The abundances of mature dark green leaves showed the significant relationship with outside bark diameter increment of all selected deciduous species and illustrated the insignificant relationship with the selected evergreen species. In case of teak trees, the potential species for tree ring analysis in the tropics, vessel size variation was useful to define annual ring boundaries and identify false rings. Rainfall and temperature in pre monsoon (January till April) and during monsoon (May till August) were important to induce both of ring width variation and false ring formation. Declined rainfall associated with increased temperature in pre-monsoon was the causation of false ring formation in earlywood zone (false ring-type I), while high temperature (especially in August) and lower rainfall during monsoon period following with heavy rainfall in post monsoon stimulated false ring formation in latewood zone (false ring-type II).
เอกสารอ้างอิง :
Palakit, K. (2013). Biology and Factors Affecting Tree-Ring Formation of Some Tree Species at Sakaerat Environmental Research Station (Doctoral dissertation, Kasetsart University).
