The Physiological And Ecological Acclimation Of Introduced Canadian Sugar Maple

Global climate change is affecting terrestrial ecosystems,with particular emphasis on the survival and growth of plants in high latitudes.The introduction of commercially valuable species to new habitats has been applied for centuries,given the anticipated increases in warming by the end of the century,the climate range change of transplanted species needs to be further extended.Relying on the Canadian sugar maple(Acer saccharum)introduction project,our study will introduce one important economic temperate forest tree species to subtropical China.The large-scale and long distance assisted migration,using space instead of time,to study the main ecological factors(temperature,precipitation,light intensity)caused by global climate change effect on the physiological and ecological responses of Canadian sugar maple.We use actual biological data to help build the species distribution model to respond to global climate change and guide anthropogenically assisted migration.The results of the study are as follows:We employed a provenance trial by introducing a temperate sugar maple of three provenances with a mean annual temperature of 3.0? in Manitoba,4.2? in Quebec and 9.4? in Ontario,Canada,to 15.8? at an introduced site in subtropical China.We measured survival,growth,summer photosynthesis in the field and stress-resistance responses under a temperature gradient in growth chambers with first-year seedlings.We found that the Ontario provenance had the highest propensity for survival and growth(48.4± 0.4 cm and 10.1 ± 0.4 mm for height and collar diameter),followed by the Quebec provenance,while the Manitoba provenance had the lowest(33.4±1.4 cm,6.5±0.6 mm).The photosynthetic parameters of the seedlings changed over time of the day,with the Ontario provenance having a higher photosynthesis rate and stomatal conductance than the Quebec and Manitoba provenances.Furthermore,the growth chamber results revealed that the Ontario provenance had the best physiological adjustment for self-protection from heat stress,followed by the Quebec and Manitoba provenances.Our results suggested that the change in climate range drove the survival and growth of introduced seedlings and that the tolerance to summer heat stress through physiological mechanisms was responsible for the success of species introduction,from a cold to a warm climate.We studied the southern Ontario provenance sugar maple at four precipitation gradient test area in Anhui province.After four years acclimation,we measured the leaf morphological and physiological traits,as well as the survival and growth rate.We found that with the increase of annual precipitation,sugar maple presents a tendency of increasing survival rate and growth rate,reach the highest when 40%(420.0± 14.2 cm and 52.1 ± 2.1 mm for height and collar diameter),but when precipitation increases to 80%,the survival rate and growth began to drop dramatically(72.2 ± 0.38 cm,7.92± 0.32 mm).The foliar shape and soluble sugar content were significantly positively related to the precipitation,and the main vein density,the stomatal density and size,moisture content and specific leaf weight and starch content were a negatively significant correlation to precipitation.Also,the increment of the Canadian maple sugar and stomatal density was significantly positively related,and the sugar content was a significant negative correlation.In conclusion that the increase of rainfall in a certain degree can alleviate the high-temperature stress,but beyond range,the combination of high humidity and high-temperature function will mainly affect stomatal density and soluble sugar content,caused serious constraints of plant's survival and growth in the physiological mechanism.We investigated the effect of light intensity in a different layer of sugar maple on autumn foliar color change.The increase in autumn temperature after introduction leads to an insufficient temperature difference between day and night,leading to poor discoloration effect.Through the studies of leaf pigments,soluble sugars and metabolic pathways in different forest layers,the following conclusions are drawn.Canopy leaves are more discolored than sub-forest leaves due to their more exposed to high light intensity.Both red and yellow leaves reach the effect of color leaves through the way of breaking down chlorophyll and carotene,as well as improving the contents of carbohydrate and anthocyanin.However,the chlorophyll decomposition and anthocyanin increase of red leaves' pigments have a greater degree of variation(1.33 ± 0.16 mg g-1 and 13.17±0.48 mg g-1 respect for upper story;0.73± 0.05 mg g-1 and 7.26 ± 0.25 mg g-1 respect for under story),making the leaves bright red.The anthocyanin synthesis pathway of sugar maple is cyanthrin,and a small amount of petunidin and delphinidin.Fructose,glucose,and sucrose as the prerequisites,increase before the rapid increase of anthocyanin synthesis.Finally,the increase of light intensity can compensate for the poor color change effect in autumn caused by insufficient temperature difference.Through the study of the color change mechanism,it can guide superior plant selection and molecular breeding of improved leaf color.In conclusion,our paper are not only studied the physiological and ecological acclimation of introduced Canadian sugar maple sugar to subtropical China but also the effects of global climate change on species in high latitudes.The introduction of "north tree and south planting" further foresaw its performance and environmental constraints,providing strong guidance for anthropogenically assisted migration and providing important insights for tackling global climate change.In future studies,we hope that there will be more actual experimental data to study the response of plants under global climate,to comprehensively analyze various data and come up with more reliable evaluation systems or models to guide the response to global climate change.