Horizontal Zonality of Genera and Its Reasons in Fagaceae of China
Tthere is horizontal zonality in Castanea,Castanopsis,Cyclobalanopsis,Fagus,Lithocar-pus,Quercus.Castanopsis,Lithocarpus,Cyclobalanopsis,Fagus mainly distribute in subtropical zone.Western area and eastern area are divided by 107°~109°E in longitude zone.They are mainly affected by winter precipitation.Winter precipitation is below 52 mm in western area and above 167 mm in east-ern area.Western area is obviously drier than eastern area.Southern area,central area and northern area are separated by 23°~25°N,28°~33°N in latitude zone according to Lithocarpus,Castanopsis,Cyclo-balanopsis,Fagus,Castanea.They are mainly affected by mean temperature of winter.Mean tempera-ture of winter is above 11 ℃ in southern area,6~10.5 ℃ in central area,below 5 ℃ in northern area.The border of Quercus is 486 mm in annual precipitation,11.4 mm in winter precipitation and-9.4 ℃ in winter mean temperate.