In vitro Competition of Betula alnoides Pollens from Two Types of Habitats in a Heterogeneous Landscape in South China

Pollens of Betula alnoides were collected in its natural forests at two types of sites with soils originated from limestone (Site L) and granite (Site G) in a heterogeneous landscape at Jingxi County, Guangxi in 2010 to 2012 to investigate whether nutritional differences between the sites influenced its pollen competition. In vitro pollen germinations were conducted separately and in pairs for these samples as well as nutrient contents of pollens and soils were measured. There was no significant difference in total nitrogen, phosphorus, potassium and calcium contents of dried pollen and in efficient ones of aqueous extracts of pollens between two types of sites although the soil nutrient contents were quite different between them, and less remarkable correlation was found between these nutrient contents of soil and pollen. The results of pollen competition of B. alnoides were much diverse among three years, it seemed that pollen-pollen interaction did not depend on site type, and might vary according to genotype and/or combination of genotypes.