Study On Photosynthetic Characteristics Of Larix Olgensis Henry Plantation

The research object of this paper is 14 years old larix olgensis Henry plantation of Maoer mountain forest farm in ShangZhi. Based on the tree’s photosynthetic data in August 2014, studied the relation, daily variation, spatial distribution variation and photoresponse curve of photosynthetic characteristics which including net photosynthetic rate (Pr), intercellular CO2 concentration (Ci), stomatal conductance (Cond), Transpiration rate (Tr) and photosynthetic available radiation (PAR) and constructed leaf area model of the larix olgensis Henry plantation. The following is detailed research content:1. Used the tree’s photosynthetic characteristics data which measured by LI-6400 photosynthesis system, analyzed daily variations of larix olgensis Henry plantation. The results showed that the daily variations had difference in different crown height, the daily variation of Pr in up crown was "bimodal curve" and in middle crown was "unimodal curve" but in low crown had no peak. There was a high consistency of the daily variation between Cond and Tr. The regularity of daily variation in up crown was decrease-stable-increase, on the contrary the regularity of daily variation of middle crown and low crown were increase-stable-decrease; The regularity of daily variation for PAR in whole crown was almost the same as that increased firstly then decreased. The time of the maximum of PAR appeared was hysteresis with the reduction of crown height; The regularity of daily variation of Ci was completely opposite to Pr, they were trading off and taking turns.2. The results of analyzed the regularity of the spatial distribution variation of photosynthetic characteristics showed that the Pr, Cond, Tr and PAR were decreased with the reduction of crown height in longitudinal level and in the transverse level, the regularity was outside> middle> inside and the difference in the transverse level was decreased with the reduction of crown height then tend to stable. The spatial distribution of Ci was obviously different from above, in the longitudinal level, the Ci was increased with the reduction of crown height and in the transverse level, the regularity was outside< middle< inside. The Transverse difference of Ci was decreased with the reduction of crown height.3. The modified model of rectangular hyperbola was the best model to fitting the photoresponse curve which compared with other light responsive models. The Maximum Pr (Pmax), dark respiration rate (Rd) and light compensation point (LCP) in up crown was the highest, the light saturation point (LSP) and apparent quantum efficiency (φ) was the highest in low crown.4. The results of analyzed the correlation between leaf area and leaf fresh weight and leaf dry weight was that the leaf area had obviously linear correlation with the leaf weight. In order to avoid the impact of moisture content of leaf, the paper choose leaf dry weight as the independent variables to constructed the leaf area model of the larix olgensis Henry. The results of analyzed the goodness of fit and tested of model independence showed that the leaf area model can estimate the leaf area of larix olgensis Henry well.