THE POTENTIALS AND LIMITATIONS OF DICOTYLEDONOUS WOOD ANATOMY FOR CLIMATIC RECONSTRUCTIONS

The incidences of selected features of dicotyledonous wood that are be lieved to be of ecologic and/or phylogenetic significance (distinct gr owth rings, narrow and wide vessel diameter, high and low vessel frequ encies, scalariform perforations, tangential vessel arrangement, ring porosity, and helical wall thickenings) were plotted through time (Cre taceous-Recent). There are marked differences between the Cretaceous a nd Tertiary in the frequency of all wood anatomical features. Incidenc es of features that are associated with markedly seasonal climates in extant floras do not approach modern levels until the Neogene. Correla tions of wood anatomical features with ecology do not appear to have b een constant through time, because in the Cretaceous different feature s provide conflicting information about the climate. Throughout the Te rtiary the southern hemisphere/tropical and the northern hemisphere/te mperate regions differed in the incidences of ecologically significant features and these differences are similar to those in the Recent flo ra. Possibilities for reliably using dicotyledonous wood for climatic reconstructions appear restricted to the Tertiary and Quaternary. Howe ver, at present the fossil wood record for most epochs and regions is too limited to permit detailed reconstructions of their past climate.