江西大岗山常绿阔叶林优势种丝栗栲和苦槠栲光合日动态特征研究

Diurnal Photosynthetic Change Characteristics of the Dominant Species Castanopsis fargesii and Castanopsis sclerophylla in Evergreen Broad-leaved Forest in Dagangshan Mountain, Jiangxi Province

利用美国LI-COR公司的LI-6400便携式光合作用测量系统,研究了江西省亚热带常绿阔叶林主要优势种丝栗栲和苦槠栲的光合日动态特征。结果表明,丝栗栲和苦槠栲叶片的净光合速率(Pn)日变化均呈现“双峰型”,有明显的光合“午休”现象。两者的净光合速率均在上午11:00达到最大值,分别为11.84μmol/(m2.s)和9.54μmol/(m2.s);两者的净光合速率均在15:00达到次高值,分别为9.09μmol/(m2.s)和5.13μmol/(m2.s)。造成丝栗栲叶片和苦槠栲叶片光合“午休”的主要原因为气孔限制。在一天中,丝栗栲叶片的净光合速率(Pn)均高于苦槠栲叶片的净光合速率(Pn)。

The LI -6400 portable photosynthesis system was used to study the diurnal photosynthetic change of the dominant species Castanopsis fargesii and Castanopsis sclerophyUa in a subtropical evergreen broadleaved forest in Dagangshan Mountain, Jiangxi Province. The results showed that the diurnal change of C. fargesii and C. sclerophylla leave presented a bimodal curve and an obvious ＇ midday depression＇ phenomenon occurred. The first photosynthetic peak value of C. fargesii and C. sclerophylla which occurred at about 11：00 am was 11.84 μmol/（m^2 · s） and 9.54 μmol/（ m^2 · s） respectively. The second photosynthetic peak value of C. fargesii and C. sclerophyUa was 9.09 μmol/（ m^2 · s） and 5.13 μmol/（m2 · s） , which occurred at 15：00 pm. The main reason for the midday depression of photosynthesis was stomatal factors. The net photosynthetic rate （Pn） of C. fargesii was higher than that of C. sclerophylla during the whole day.