Study On Photosynthetic Characteristics And Potential Productivity Of Five Canopy Tree Species In The Broad-leaved Korean Pine Forest

This paper aims to predict the variation tendency of photosynthetic productivity in populations under globe warming environment in the future.In State-owned Forest Protection Center of Jilin Forestry Pilot Zone,five species of arbor plants in the canopy of MBKPFs,Ulmus davidiana,Tilia amurensis,Juglans mandshurica,Quercus mongolica and Pinus koraiensis,were selected as the research object to explore the intraspecific variability of photosynthetic characteristics,spectral reflection characteristics,morphological characteristics and stoichiometric characteristics among canopy position and diameters class,and to explore the response of photosynthetic capacity to different temperatures.The adaptability to light stress of five main species in different succession stages of broad-leaved pine forest was revealed from the physiological perspective and the interspecific correlations between photosynthetic parameter and spectral reflectance index was established.The photosynthesis potential productivity of the populations was estimated.The daily photosynthetic production rate of five species at different temperatures was compared to predict the influence of warming environment to the primary productivity of populations,which providing basic data for the study of forest primary productivity and the restoration of MBKPFs in northeast China.The main conclusions from this study were as follows:(1)The community succession were closely related to photosynthetic characteristics of species,and the difference of adaptability to light stress among tree species were manifested both in photosynthetic characteristics,spectral reflection characteristics,morphological characteristics and stoichiometric characteristics.Compared with P.koraiensis,the constructive species,higher apparent quantum efficiency,lower light compensation point and dark respiration rate was characterized in transitional species along with higher chlorophyll content,thinner layer of palisade cell and lager specific leaf area,which was more advantageous to accumulate organic matter underwood.P.koraiensis could accumulate more organic matter for growth with stronger photosynthetic capacity and higher primary production rate under strong light.(2)There were no significant differences showed in the photosynthetic characteristics,spectral reflectance characteristics,specific leaf area,leaf thickness,and leaf element content among sample positions within species(P>0.05).The difference of tree height below 15 m and canopy azimuth was not enough to cause adaptive changes in photosynthetic physiological characteristics.(3)Among broad-leaf species,dark respiration rate and light compensation point were significantly negatively correlated with photochemical reflection index(PRI)with Rsquared 0.96 and 0.94 respectively(P<0.05).(4)The contribution to community productivity was sorted as follows: U.davidiana < T.amurensis<J.mandshurica< Q.mongolica< P.koraiensis with U.pumila at 4.531 kg/s,T.amurensis at 1.428 kg/s,J.mandshurica at 1.139 kg/s,Q.mongolica at 0.497 kg/s and P.koraiensis at 0.207kg/s respectively.Individuals in the 20-40 cm diameter range contributed 51.46% of the population productivity in U.davidiana,while individuals in the 20-50 cm diameter range contributed 64.57% and 86.07% of the population productivity in T.amurensis and J.mandshurica respectively,individuals in the 30-40 cm diameter range of contributed 64.83% in Q.mongolica,and individuals in the 10-30 cm diameter range contributed 58.62% of the population productivity in P.koraiensis.(5)Evergreen plants showed greater temperature homeostasis of photosynthesis and the lowest sensitivity of the photosynthetic capacity to temperature with no significant difference in the four light response parameters measured at three temperature.The average daily productivity of P.koraiensis was stable at 2.923 g C/m2·day1.The optimal temperature for photosynthesis of other 4 broad-leaved tree species sorted as U.davidiana and Q.mongolica< T.amurensis<J.mandshurica.The optimum temperature of U.davidiana and Q.mongolica was close to 25 ?,with the maximum average daily productivity under light 3.211 g C/m2·day1 and 3.606 g C/m2·day1,respectively.T.amurensis had the maximum average daily productivity 4.106 g C/m2·day1 at 30? and J.mandshurica 5.701 g C/m2·day1 at 35?.By the end of 21 th century,the contribution of U.davidiana and Q.mongolica to community primary productivity would decrease with the global surface temperature increasing by 0.3-4.8?,while T.amurensis increase and P.koraiensis remained relatively stable.