天山中部天然林分中不同龄级天山云杉光合特性

Photosynthetic Characteristics of Picea schrenkiana var. tianschanica of Different Age Classes in a Natural Stand in the Central Part of Tianshan Mountains

采用LI-6400便携式光合测定系统对天山中部天山生态站天然林分中4个龄级(即Ⅰ(0～20年)、Ⅱ(20～40年)、Ⅲ(40～60年)及Ⅳ≥60年以上)天山云杉林木不同叶龄叶片的光合速率进行测定,分析在自然环境条件下天山云杉的基本光合特性。结果表明:在自然林分中,不同龄级不同叶龄天山云杉的光补偿点在10～25μmol.m-2s-1之间,光饱和点在870～1220μmol.m-2s-1之间;不同龄级不同叶龄天山云杉阳生叶的净光合速率日变化为单峰型曲线,分别在10:00—13:00时段内达到最大光合速率;相同叶龄不同龄级天山云杉的净光合速率大小顺序为Ⅲ龄级>Ⅳ龄级>Ⅱ龄级>Ⅰ龄级;阴生叶的净光合速率日变化除Ⅰ龄级为单峰曲线外,其他3个龄级的为双峰曲线;最大净光合速率值随着林木龄级的增加,表现出先增加后有所降低的趋势,Ⅲ龄级的最大净光合速率值最大;相同年龄不同叶龄的净光合速率值基本上为当年生叶>1年生叶>2年生叶。阳生叶的净光合速率与环境因子中的光照强度、温度、室中CO2浓度、空气相对湿度具有极显著的相关性,而阴生叶只与光照强度呈极显著的正相关性,与空气相对湿度成极显著的负相关。

The spruce stand was classified into four age classes i.e. age class Ⅰ （0 - 20 years）, Ⅱ （20 - 40 years）, Ⅲ （40 - 60 years）, and Ⅳ （ ≥ 60 years）. The basic photosynthetic characteristics of this species in the natural stands have never been studied. In this paper we investigated the variation of net photosynthetic rate among Picea schrenkiana var. tianschanica trees in the different age classes growing in its natural stand with a portable photosynthesis system of Li-6400. The result showed that the light compensation point of different age needles of trees in different age classes was in a range of 10 - 25 μmol·m^-2s^-1 , and the light saturation was 870 - 1220 μmol·m^-2s^-1 The diurnal change of net photosynthetic rate of sunny needles in the different ages all exhibited the uni-modal curves with their peak values occurring at 10：00, 12：00 and 13：00, respectively. There was variation in maximum net photosynthetic rate value of the same age needles among the different stand ages, and the order was： age class Ⅲ〉 age class Ⅳ 〉 age class Ⅱ 〉 age class Ⅰ . The diurnal changes of net photosynthetic rate of the shady needles revealed the bimodal curves in all stand ages except for the age Ⅰ , which had a uni-modal curve of change. The value of maximum net photosynthetic rate of the same age class was in an order of current year needles 〉 1-year-old needle 〉 2-year-old needle. The regression analysis indicated that Pn of sunny needles was positively correlated with PAR, Tair, Tleaf and H2O-S, while its correlations with CO2-S, RH-R and CO2-R were significantly negative. The Pn of shady needles had significantly positive correlation with PAR, and negative correlation with RH-R.