Pollen Morphology Of Fagaceae From Subtropics Of China

Fagaceae is one of the most important families composed of subtropical and temperate forests, and distributed widely in northern hemisphere. It has about900species of6-11genera. China homes about300species of7genera, namely Quercus, Cyclobalanopsis, Castanea, Castanopsis, Fagus, Lithocarpus, and Trigonobalanus. Quercus has widest distribution areas in subtropics, followed by Cyclobalanopsis, while Castanopsis can be dominant community in subtropical forests.This thesis uses light microscopy(LM) and scanning electron microscopy (SEM) to observe and study the pollen morphology of28species from above mentioned seven genera. Pollen keys are made based on pollen morphology and statistic results. This paper established criteria for distinguishing recent Fagaceae pollen, especially to identify the evergreen and deciduous Quercus. How to identify Castanopsis, Castanea, Lithocarpus is a big challenge due to morphlogical overlaps among them, and the limitations are discussed for these pollen types. Recent pollen keys are essentials for fossil pollen determination, upon which fossil pollen grains can be identified.Quercus fossil pollen grains frequently occur in Quaternary sediments, and pollen analysis is an effective eay to reconstruct past vegetation and palaeoclimate. To identify Quercus pollen between evergreen and deciduous is very important in the interpretation of parent vegetation, palaeobiogergraphy and palaeoclimatic conditions., since these two important taxa are representative of strong information of climate signalsAccording to pollen observation and morphological dimenstions statistics, Quercus pollen grains often3colpus and3colporated; endoaperture not distinctive or without endoaperture; colpi long; ornamentation nodular under SEM. In general, evergreen Quercus pollen types are smaller than29.47μm, with3colporate, fine granular under LM, while variable under SEM, namely rod-like, spiny, crisped, verrucous, flat verrucous. The deciduous Quercus pollen typses are larger than33.54μm,3colpus, ornamentation coarse granular under LM. SEM verrucous, crisped.Cyclobalanopsis pollen grains are spherical. Equatorial view is spherical, polar view is3lobed round,3colpate-poroid. The ornamentation fine granular under LM, and nodular under SEM. The pollen morphology of this genus shows close linkage to evergreen QuercusCastanea, Castanopsis, Lithocarpus pollen grains are tricolporated and smaller than other genera of Fagaceae, with average size between (16.97-11.51) μm.Fagus pollen grains are the biggest in Fagaceae, with3-4colporate, short, endoaperture big and distinctive. Pollen sculptures are variable from species to species. from short rod-like to rugulated.Trigonobalanus pollen grains is oval-shaped, equatorial view oval, polar view obtuse triangle, different from the other genera.3colporated, endoaperture square and large, granulate-rugulated under LM and verruculate under SEM.According to pollen morphology and quantitative statistic results, Cyclobalanopsis is treated as a subgenus of Quercus. This thesis also presents pollen keys to genus level based on pollen morphology and numerical analysis for pollen dimensions, and proposes the keys to evergreen and deciduous Quercus as well. Notably, evergreen Quercus pollen and Cyclobalanopsis identification needs special care. This thesis also suggests that the two pollen types of evergreen Quercus-Castanopsis type can be differtiated but with limitations as well. Castanea, Castanopsis, Lithocarpus pollen morphological characteristics overlap more than other genera, thus it is still difficult to accurately distinguish them. Fagus pollen grain is relatively possible to identify. These basis of modern pollen keys can provide imporant criteria for the identification of fossil pollen, upon which past vegetation,palaeoclimatic changes, palaeobiogeography, paleoecology and paleoenvironmental research in Quaternary are possilbe.