Study On Reproductive Phenology Of Woody Plants In Gutianshan And Botanical Garden Of The Institute Of Botany, Chinese Academy Of Sciences

Ecologists often attribute environmental factors such as rainfall, temperature, and day length as proximate mechanisms shaping plant phenology. However, it is still disputed whether climatic variables are exclusive triggers of phenological events. Recently, an increasing number of studies showed that flowering patterns can be also affected by phylogeny, and/or functional traits. Those studies on plant phenology mostly focus on temperate areas and tropical areas, but few investigated sub-tropical forest. Besides, phenological studies usually focused on higher taxonomic levels, such as families and genera, less publications concentrated on specific level. On the other hand, botanical garden always brings in artificial factors, which is distinct from natural forest, but drew less attention. To better understand the effect of different factors on reproductive phenology of woody plants, phenological data were employed from subtropical evergreen broad-leave forest in Gutianshan and Botanical Garden of the Institute of Botany, Chinese Academy of Sciences to discuss the correlates of three factors, including climatic variables(temperature, precipitation, irradiance), phylogeny and plant functional traits(dispersal mode, seed mass, maximum tree height, flower color, pollinator groups), with reproductive phenology. Phylogenetically Independent Contrasts(PIC), Blomberg K-values and phylogenetic generalized least-squares regression(PGLS) were employed for subsequent analyses. With comparison of data from GTS and CAS, workers can better understand the differentiation of phenology of temperate and sub-tropical forest in China. Our results showed that:(1) Woody plants in CAS and GTS flowered seasonally, most of them flowered at April and May. Fruiting time in CAS was also seasonal, a majority of them fruited at August and September;(2) There were significant correlations between the number of species flowering per month and climatic variables, including rainfall and temperature, but not irradiance;(3) Phylogeny on the specific level significantly influenced the reproductive phenology. Taxa with close relationship tend to show similar reproductive time, but this impact was weak in CAS. The relationship between fruit type and fruiting time changed with the phylogeny was taken into consideration. It indicates that phylogeny plays an important role in plant reproductive phenology and cannot be ignored in phenological comparisons between groups(fleshy- vs. nonfleshy-). Our results supported the phylogenetic hypothesis;(4) The impacts of plant functional traits on reproductive phenology of woody plants varied across regions. There were significant associations between the flowering time and maximum tree height, indicating that species with lower tree height tend to flower later than that of canopy trees. To the species in CAS, wind-pollinated species flowered and fruited earlier than insect-pollinated species. However, none significant correlation was found between flowering time and pollination mode in GTS. Other functional traits, including seed mass, dispersal modes, pollinator group and flower color had no significant effects on flowering time.In conclusion, flowering time of woody plants in temperate regions(represented by CAS) and sub-tropical forest(represented by GTS) is seasonal, most plants flowered in spring or early summer. Reproductive patterns of sub-tropical forest are usually associated with climatic variables, including temperature and rainfall, plant functional traits, and with their phylogeny. However some correlations between functional traits and flowering time varied with regions, which indicated that botanical garden may have different phenological responses because of the impacts of human activities. Whereas, it is difficult to clearly disentangle the effects of different factors on reproductive phenology due to all those factors interact with each other. Additionally, short duration of phenological data and the low-resolution phylogentic trees could reduce the reliability and accuracy. Present study can offer reference to future phenological investigations in China, and provide support to agriculture and forestry. Besides, we suggest an application of controlled experimental approaches, which can be helpful to resolve the different climatic factors from each other. In addition, further studies should be conducted globally in more forest sites of different latitude with long series phenological data.