The Bud And Cambium Phenology And Its Influence Factors In Three Picea Species

Phenology is the growth and development rule of tree formed by long-term adaptation to seasonal climate change,and is the key factor determined adaptability and distribution of tree species.Most of the current research focuses on bud or leaf phenology,but other tissue structures(cambium,etc.)and systematic research on activity characteristics during bud burst are still lack.As an important component of dark coniferous forest in the world,the genus Picea species has a large heterogeneity of distribution environment and high sensitivity to environmental changes,which is an ideal material for studying the trees phenological response to environmental changes.Therefore,in this study,the 12 year old P.koraiensis,P.crassifolia and P.wilsonii with obvious regional differences in distribution in common garden were selected to monitor the bud and cambium activities,and combined with the original habitat environment factors,to explore the reason of phenological differences between bud and cambium.The main research results are as follows:(1)Bud burst of the three tree species followed the process of cracking-elongation-swollen-transparency-leaf-developing-leaf-spreading,but the morphological characteristics of the three tree species were different at each stage.Bud burst began in early April and ended in early May,lasted for nearly a month.The beginning time of P.wilsonii was significantly later than that of the P.koraiensis and P.crassifolia,the ending time was not significantly different among the three species,and the duration of the P.wilsonii was significantly shorter(23 days)than that of the other two species.(2)The cambium activities of the three species began in early April and completed in late September,and the cell division phase ended in late July.The whole process lasted for nearly 6 months.ANOVA showed that there were no significant differences among the three species in the beginning,ending and duration of cambium activities,but the duration of the activity of the whole cambium was more than 20 days longer than that of the other two species.(3)The effective accumulated temperature based on 0 ? of P.wilsonii bud burst was significantly higher than other two species,but not different based on 5 ?.Therefore,0 ? as the biology zero temperature is more suitable for conifers.Combined with the climate data of the three species distribution area,it was found that higher early spring temperature in the experimental site may lead to the early bud burst of P.koraiensis and P.crassifolia.Moreover,the average temperature threshold of three species cambium activity were within the scope of 13 ? to 15 ?,suggested that there may be a consensus of conifer cambium activity threshold temperature.(4)Bud burst of P.koraiensis and P.crassifolia was earlier than that of cambium activity,but there was no significant difference between them of P.wilsonii.There was no significant difference between the end of bud burst and the thickening stage of secondary cell wall after cambium activity in the three species.In early spring,tree used the stored resources mainly for bud growth,and then,the stored resources and photosynthate produced by new leaves were mainly used to build the cell wall of the newly generated xylem,indicating that there was a resource allocation mechanism to balance the activities of buds and cambium.All in all,by monitoring the whole process of bud and cambium activity of the three species,we accurately divided each stage of bud and cambium phenology that could provide reference for future phenological monitoring.At the same time,the result indicated that habitat temperature is the main factor leading to the different time of bud burst,but effect little to cambium activity.Therefore,it should be considered the effects of environmental factors on the growth and development of different tree tissues fully when predicts tree growth and distribution under future climatic conditions.