Seasonal dynamics of photosynthesis and spectral characteristics of natural regeneration Pinus koriensis in the Changbai Mountains
To explore the physiological and spectral characteristics of Pinus koriensis needles of different ages in different seasons,we measured the gas exchange parameters and spectral reflectance of needles of four ages in mid-June (early growing season),late July (mid-growing season),and early September (late growing season),using the Li-6400 portable photosynthesis analyzer and Unispec-SC spectral analysis system.The experimental subjects were 20 to 30 year-old young trees of Pinus koriensis,all natural regeneration in the basically same growth environment.The results showed that the maximum net photosynthetic rate (Pmax) and stomatal conductance (Cond) increased gradually from June to September.When the current needles were fully grown,the maximum net photosynthetic rate of 1-year-old needles was lower than that of 2-year-old ones,probably due to the metastasis elements required for photosynthesis.Except for l-year-old needles in early September,the transpiration rates decreased with the needle age but increased with time.The trend of dark respiration rate (Rd) was not regular.In different seasons,photosynthetic parameters of 3-year-old needles were always at a lower level,with no significant variation.Photosynthetic parameters of current-year,1-year and 2-year-old needles all changed significantly.Chlorophyll normalized difference index (ChlNDI),photochemical reflectance index (PRI) increased with the season but decreased with the leaf age.Structure-independent pigment index (SIPI) showed opposite tendency.A two-factor analysis of variance on photosynthesis and spectral parameters showed that except for the insignificant effect of needle age on dark respiration rate (Rd),and time on the chlorophyll normalized difference index (ChlNDI),the leaf age and season had significant effect on the other parameters,but with no significant interaction between themselves.The growth of Pinus koriensis throughout the growing season is mainly attributed to the 1-year and 2-year-old needles,very little to the 3-year-old ones; the fully-grown current needles also make great contribution to the growth of the young trees.
NETL
NSTL
万方数据
维普
