Comparative Study On Seasonal Changes Of Physiological And Biochemical Characteristics Of Eucalyptus,Broad-leaved And Coniferous Tree Species

This study used three evergreen broad-leaved tree species(Eucalyptus GL9,Castanopsis fissa,Castanopsis hystrix)and two evergreen coniferous species(Pinus massoniana,Cunninghamia lanceolata)as the research objects which had grown in Eucalyptus plantation and mixed forests in Lingtian County,Guilin,Guangxi,China,by measuring the diurnal variation of photosynthetic characteristic(Pn,Gs,Ci,ect)of Eucalyptus,Pinus massoniana and Cunninghamia lanceolata all the year round,and calculating the corresponding seasonal WUE,LUE and CUE.The light-response curve of Eucalyptus,Castanopsis fissa and Castanopsis hystrix would be quantitatively simulated by Farqular model,and extracted the main light response curve parameters at the same time.In outdoor experiments,the works included determining the physiology and biochemical indexes(water content,SLA,SS,SP,Chl,POD,NRA,APA).The purpose of this study is to carry out the seasonal variations about photosynthetic and transpiration characteristic,the nutritive substance,nitrogen and phosphorus nutrition metabolize indexes of 5 evergreen tree species.The results were as follows:1.Daily variation of Pn of Eucalyptus,Pinus massoniana and Cunninghamia lanceolata presented "double curve" in spring and summer,but "single curve" in autumn and winter.When it presented "double curve",the noon rest of Pn occurred.There were significant differences among 3 tree species,Eucalyptus was higher than the other 2 tree species.The changing trend of average Pn of 3 tree species in different seasons was:spring>summer>autumn>winter.Both Pn and PAR present great synchronicity in four seasons,and this phenomenon resulted LUE in a peak in winter.2.Diurnal and seasonal variations of Tr,Gs and Vpdl of 3 tree species were the same,showed summer>spring>autumn>winter,but different seasons had obviously affected on these tree species.Comparing the average of these indexes above,Eucalyptus was the highest,but Cunninghamia lanceolata was lowest.The tend of Tr,Gs and CUE were similar to the tend of Pn,but contrary to tend of Ci,and this phenomenon could explain that the influencing factor of photosynthetic rate was stomatal limitation.At the beginning,WUE decreased,but increased lastly in winter.Comparing the average of WUE and LUE,WUE of Eucalyptus was the highest among 3 tree species,but CUE fell to lowest in autumn.3.The result of light response curves which were simulated by Farqular model showed that there were differences among the characteristic parameters of Eucalyptus,Castanopsis fissa and Castanopsis hystrix.in different seasons.Q of 3 tree species reached the maximum in winter,which could verify that LUE of Eucalyptus was the highest in winter.Comparing the average Q of 3 tree species,Eucalyptus was the highest.The differences of Pmax among 3 tree species in different seasons were larger,the overall change trend was:spring>summer>autumn>winter.The the highest value of RD appeared in winter,but the lowest value occurred in spring or summer.Lcp was the highest in winter,otherwise Lsp reached the lowest point all the year round.4.The seasonal change patterns of main physiology and biochemical indexs which investigated in laboratory of 5 tree species(Eucalyptus,Castanopsis fissa,Castanopsis hystrix,Pinus massoniana,Cunninghamia lanceolata)were different,and the same with leaves water content.The average leaves water content of Cunninghamia lanceolata was higher than the other trees species in spring,and coniferou tree species was higher than broad-leaved tree species.On the contrary,the average SLA of broad-leaved tree species was higher than coniferous tree species,and the average SLA of Eucalyptus was the highest in summer among 5 tree species.5.The Chlorophyll Content of evergreen tree species reached a peak in summer,but lowest in winter,taken as a whole,the average chlorophyll content of broad-leaved species was significantly higher than coniferous species.For the same plant,chlorophyll content had some relation with Pn,but the different Genetic made chlorophyll content can not reflect the photosynthetic rate completely.For example,Pn of Pinus massoniana was just lower than Eucalyptus,but the chlorophyll content was the lowest.6.The seasonal change patterns of the main nutritive substance of 5 tree species were different,and the trend of soluble sugar content was summer>spring>winter>autumn.Soluble protein content of broad-leaved species especially Eucalyptus was significantly higher than coniferous species in spring.7.POD,NR and APA are the major factors of plant growth and development as well as nitrogen phosphorus nutrition metabolize.The seasonal change patterns of POD of 5 tree species had the order of spring>winter>summer>autumn,but the average POD of broad-leaved species was significantly lower than coniferous species.The trend of NR was summer>spring>winter>autumn,and the average NR of Eucalyptus was the highest among 5 tree species.The average APA of 5 tree species rose to the highest level in spring.But in the same growing environment,the average APA of these tree species made significant difference,and it also turned out that different trees species have their own phosphorus use efficiency.In conclusion,the response mechanism on the physiology biochemical indexs of these 5 tree species in four seasons was different.