Study On Leaf Phenology Pattern And Adaptive Strategies Of Greening Tree Species In Coastal Saline Land Of Shanghai

In recent years,a large number of coastal new cities were built on reclamation coastal areas with the fast urbanization process in China.There are very few plants can grow normally due to high concentration of salinity and greening is very difficult in coastal new cities.The ways of leaf development and leaf life span directly affect the photosynthetic capacity and material accumulation.Meanwhile,Leaves are very sensitive to the external environment changes and adversity conditions.Different ways of leaf development and leaf life span will affect the growth and adaptability of plants.In order to explore the adaptability of greening tree species to coastal saline land,28 tree species planted in coastal saline land were selected as the objects from March 2012 to January 2014 in Chongming Island,Shanghai.7 tree species which were the same with species in the study area in Chongming Island planted in non-saline land in Minhang District of Shanghai were selected as control.The leaf phenology pattern,the phenology difference among different tree species and possible adaptive strategies were studied.The main results were as follows:(1)Leaf budburst pattern:Leaf budburst of tree species in coastal saline land occurred from early of March to early of May.27 greening tree species were divided into the earliest beginning-longer duration,later beginning-the shortest duration,later beginning-the longest duration and the latest beginning-shorter duration four groups according to beginning and duration of leaf budburst.The leaf budburst types included unimodal type,bimodal type and multimodal type;mainly for unimodal type and bimodal type.The intraspecific synchrony of leaf budburst phenology was the highest in Melia azedarach,Wisteria sinensis,Zizyphus jujube and Albizia julibrissin,the lowest in Acer buergerianum and Ulmus parvifolia,and was in the middle in other 22 species.(2)Leaf emergence pattern:Leaf emergence of tree species in coastal saline land occurred from middle of March to late of May.28 greening tree species were divided into the earliest beginning-the longest duration,earlier beginning-the shortest duration,later beginning-shorter duration and the latest beginning-longer duration four groups according to beginning and duration of leaf emergence.The leaf emergence types included unimodal type,bimodal type and multimolal type.Most tree species belonged to unimodal type,followed by bimodal type,and the least species belonged to multimodal type.The intraspecific synchrony of leaf emergence phenology was the highest in 5 species such as Melia azedarach,Gleditsia sinensis,Celtis tetrarndra ssp.sinens s and so on,the lowest in Acer buergerianum,and was in the middle in other 22 species.(3)Leaf abscission pattern:Leaf abscission of tree species in coastal saline land occurred from early of October to late of December.28 greening tree species were divided into the earliest beginning-the longest duration,earlier beginning-the shortest duration,earlier beginning-shorter duration,later beginning-longer and the latest beginning-shorter duration five groups according to beginning and duration of leaf abscission.The leaf abscission types included unimodal type,bimodal type and multimodal type;mainly for bimodal type and multimodal type.The intraspecific synchrony of leaf abscission phenology was higher in 5 tree species such as Koelreuteria bipinnata,Alchornea davidii,Wisteria sinensis,Cercis chinensis and so on,lower in 5 tree species such as Acer buergerianum,Zizyphus jujube,Ginkgo biloba and son on,and was in the middle in other 18 species.(4)The overall pattern of leaf phenology:28 greening tree species were divided into the earliest time of leaf emergence-the latest time of leaf abscission,the latest time of leaf emergence-the latest time of leaf abscission,earlier time of leaf emergence-later time of leaf abscission,the latest time of leaf emergence-later time of leaf abscission,the latest time of leaf emergence-earlier time of leaf abscission,earlier time of leaf emergence-the earliest time of leaf abscission and later time of leaf emergence-the earliest time of leaf abscission seven groups according to time of leaf emergence and time of leaf abscission.The leaf phenology types of 27 greening tree species were divided into unimodal leaf budburst-unimodal leaf emergence-bimodal and multimodal leaf abscission,unimodal leaf budburst-bimodal and multimodal leaf emergence-bimodal and multimodal leaf abscission,bimodal and multimodal leaf budburst-unimodal leaf emergence-unimodal leaf abscission,bimodal and multimodal leaf budburst-unimodal leaf emergence-bimodal and multimodal leaf abscission,bimodal and multimodal leaf budburst-bimodal and multimodal leaf emergence-bimodal and multimodal leaf abscission five groups.The intraspecific synchrony of the total leaf phenology was the highest in Zizyphus jujube,Melia azedarach,Albizia julibrissin,the lower in 22 tree species such as Sophora japonica,Amorpha fruticose,Ginkgo biloba and so on,and the lowest in Acer buergerianum and Ulmus parvifolia of tree species.(5)Adaptive strategies or response ways:The possible adaptive strategies or responses of leaf phenology of greening tree species to the comprehensive environmental factors of coastal saline land were:delaying the time of leaf budburst and leaf emergence,prolonging the leaf budburst duration in spring,shedding leaves in advance and prolonging the leaf abscission duration in autumn and shortening leaf life span;bimodal or multimodal leaf budburst or leaf abscission types;lower intraspecific synchrony of leaf phenology to adapt to the unstable environmental conditions in coastal saline land.In summary,the results of this study can not only enrich the theoretical knowledge of plant adaptation ecology,but also have significance for the greening of saline-alkali land in Shanghai and surrounding areas.