Flowering Phenology and Floral Distribution of Castanopsis fargesii in Tiantong, Zhejiang Province

Abstract

Forested areas of eastern China are predominatly evergreen broad_leave d forests which are typically zonal or climatic climax vegetation in subtropical areas, dominated by Castanopsis fargesii Franch. (Fagaceae),a shade_toler ant an d long_lived species. The observation and study of its reproductive characterist ics in the field still remain poorly understood. Based on the methods of Randomi zed Branch Sampling and observation of labeled individuals, the flowering phen ol ogy, flower number and spatial distribution of Castanopsis fargesii Franch. from the Schimeto_Castanopsietum fargesii Association in the Tiantong National F ores t Park (TNFP) were studied in this paper. The results showed that the floral bud flushing and inflorescence elongation of C. fargesii emerged at end of Apri l an d the trees flowered after leaf emergence. The onset of mass flowering occurred at late May, and its duration within population could last more or less eight d ays, while the flowering time among individuals experienced less difference. The refore C. fargesii displays synchronous flowering. Given the lower precipit ation and gradually increasing temperature during April_May, synchronous floweri ng and therefore pollination in C. fargesii is a beneficial adaptation. Floral buds commonly located at the first_order branch, which made up 91. 92% of all the reproductive branch, nearly 7.07% and 1.01% at the second and th e third branch, respectively. There was an apparent difference between the flora l bud initiation at the toward_sun reproductive branch and the toward_shade ones within a crown (p0.01) and the floral bud initiation were 78%±5.7% and 67 %±5.7% respectively. Within a crown, there were about 4.89±1.82 panicles per reproductive branch at sun_side and 3.08±2.08 at shade_side. The number of male inflorescence of C. fargesii is more than that of the fem ale and male inflorescence occupied 77.9% of the total and female inflorescence 22.1 % respectively. There were 67.9±16.7 staminate at one male inflorescence and 2 6.1±5.08 pistillate at one female inflorescence. Furthermore, the flower number s were male biased during spring censuses and the ratio of staminate to pistilla te was about 9.2∶1. Mass staminate could produce higher pollen concentration du r ing synchronous period and should increase the pollination efficiency. Therefore flowering in spring exerted great influence on the reproductive output of C. fargesii.