The Photosynthesis Of Casuarina Equisetifolia Plantation In Different Coastal Gradients

Casuarina equisetifolia was originated from Australia ,East-South Asia and the Pacific. Tt play important role in wind break and sand fixation,ameliorating ecological environment and offering timber along the southeast coast in China.To some extent, it has become one of the irreplaceable plantations in protecting plantation, particularly on the wind gap site. In this study, 20-year-old coastal sand forest plantations of Casuarina for the experimental materials, according to the distance from the coastline is divided into four different gradient, with LI-6400 portable photosynthesis measurement system observing the characteristics of Casuarina photosynthesis parameters, system Casuarina plantation of diurnal and seasonal photosynthesis and related physiological changes in the relationship between ecological factors, for predicting the coastal sand of the photosynthetic productivity of casuarina plantations to estimate its carbon balance and understanding of forest response to global change and Casuarina artificial conservation and management of forests to provide theoretical basis.The main results are as following:1.Casuarina equisetifolia's Pn daily variation are different among four gradient.The first gradient is the single-peaked curve.The highest value is about 10 o'clock.Other gradient'Pn are the typical double high value curve which is lower at noon.The highest value is also around 10 o'clock,the second is around 14 o'clock,and the lowest is around 12 o'clock.It expresses the lunch break phenomenon obviously.In total,the second gradient has better performance than others in the morning. The diurnal variation of the Light use efficiency is high in the morning and at evening,but low at noon, show a"u"curve change, the second gradient is the highest. Photosynthetic active radiation, temperature changes in the day showed a single peak curve, the peak period in between 11:00-13:00. Air relative humidity, atmospheric CO2 concentration, stomatal conductance and intercellular CO2 concentration diurnal variation was dropped after the first rise. Diurnal variation of the indicators, temperature, PAR and the daily change of Pn was very significant positive correlation, relative humidity, intercellular CO2 concentration showed significant negative correlation.2.Casuarina equisetifolia's Pn season variation is double high value curve.The first high value is in June,and the second is in September.From June to September is Casuarina equisetifolia's photosynthesis production prosperous period. The change of environment term has effective in the Pn season variation. The second gradient has better photosynthesis performance. The Pn at different layers in the seasonal variation are different curves, the peak is different, the fourth gradient is single-peak curve, the peak in about August. The rest of the gradient curve was bimodal. The first peak of the second gradient is in June, second peak in August, after declining gradually. From June to September period is a strong production during photosynthesis. Comparison of view, the second strong gradient of photosynthetic capacity. Changes in PAR and air temperature was single-peak curve, the temperature fell slightly in July, may be related to rain. CO2 concentration in the air was varied from 360-400μmolCO2?mol-1.3.Casuarina equisetifolia's LCP is between 10-60μmol?m-2?s-1,LSP is between 70-500μmol?m-2?s-1. Casuarina photosynthesis on light intensity response curve may vary due to the gradient. The available range of light intensity and photosynthetic in efficiency are different among gradients, the use width of the second gradient is the most, the gradient of the first use of the narrowest scope, the LCP of the first gradient is the lowest, and the LSP of second gradient is the highest on their ability to adapt to higher light.Determination of apparent quantum efficiency results show that the sprig of Casuarina in the quantum yield is different in different layers . The first gradient of the quantum yield is the highest.The second gradient is the lowest, which energy utilization efficiency for the use of low-light ability is small.The Pn of the third gradient is the highest when light-saturated, the photosynthetic potential is the largest; the first gradient is the lowest.4.Casuarina equisetifolia's CCP is between 13-19μmol?m-2?s-1,CSP is between 1500-1800μmol?m-2?s-1. The available capacity and utilization of the capacity of light intensity are different in different gradients. The use of CO2 for the third and the fourth gradient are wider;the second and the first gradient are narrower. The third and fourth gradient have a higher CSP and the ability to adapt for CO2 concentration. The first gradient has lower CCP, and its adaptation to low CO2 concentration ability is aslo weak.Carboxylation efficiency (CE) of the first gradient and its utilization of low CO2 concentration are the highest, and the second and third gradient are following, the fourth gradient is the lowest.The regeneration rate of RuBP of second gradient is the highest, the fourth gradient is the lowest. The results from the tests can be seen, the photosynthetic capacity of second gradient is the highest, the fourth gradient is the lowest.5.The variation of the Chl of different gradients is consistence Chlorophyll content at different gradient in the season is basically the same curve, showing a downward trend after September,and seasonal variation of Chl is similar to the variation of the Pn, and its mean of gradient chlorophyll content of Casuarina are between 1.2-1.4mg. g-1. The chlorophyll content of the first gradient was significantly lower than other gradients.