科尔沁沙地黄柳再生枝与现存枝形态和光合特征的比较

A Comparative Study on Photosynthesis and Morphological Characteristics of Salix gordejevii Between Regenerated Shoots and Standing Shoots

对黄柳经平茬后形成的再生枝和未平茬的现存枝的光合作用、株高、基径、叶片大小等形态特征进行了比较研究 ,结果表明再生枝比现存枝具明显的生长优势 :再生枝高度及高度频度分布均与现存枝十分接近 ;再生枝基径显著大于现存枝 ,前者过细和过粗枝条的比例均较低 ,基径频度分布趋于正态分布 ,后者细枝条比例较高 ,基径频度分布符合对数正态分布 ;同时再生枝叶片更长、更宽 ,叶长和叶宽接近于平均值的叶子所占比例更大。在上午时段内叶片温度和光合有效辐射随气温同步上升 ,黄柳叶片的净光合速率总体上都比较高 。

Salix gordejevii is a kind of pioneer shrub on moving and semi-moving dunes in Horqin Sandy Land, Inner Mongolia. It is also widely cultivated there for soil conservation or as fuel source. In this paper, the regenerated shoots and standing shoots of Salix gordejevii were investigated on leaf photosynthesis, leaf blade size, plant height and diameter, and some other related growth parameters. The plots for experiment were on two semi-fixed dunes with a slope of 5～10 degrees. Salix gordejevii in plot I was planted with cuttage in spring 1999 and root sprouts formed in that growing season were then cut at base in spring 2000, so that shoots under observation were all regenerated shoots. Salix gordejevii in plot II were planted in the same way in spring 1999 but the root sprouts were kept as they were afterwards, so that they were all standing shoots at the time of observation. Field experiments were carried out from the last ten days of July to the first ten days of August. The regenerated shoots had an advantage over the standing shoots in growth. Height of the regenerated shoots was similar to that of the standing ones, and the height frequency distribution for both kinds of shoots followed Logarithmic Normal Distribution Model. The regenerated shoots were also greater than the standing shoots in diameter at base. The diameter frequency distribution of the regenerated shoots followed Normal Distribution Model while the standing shoots followed Logarithmic Normal Distribution Model, which indicated that the thickness of most of the regenerated shoots was statistically closer to the means than that of the standing shoots and that the regenerated shoot population was at developing stage while the standing shoot population tended to decline. Advantages of the regenerated shoots also lay in leaf dimension. The leaves of the regenerated shoots were longer and wider than those of the standing shoots. The leaf blade length frequency distribution of the regenerated shoots followed Normal Distribution Model while that of the standing shoots followed Weibull Distribution Model. With regard to leaf blade width frequency distribution, the regenerated shoots followed Weibull Distribution Model while the standing shoots followed Logarithmic Normal Distribution Model. All these indicated that length and width of most of the regenerated shoot leaves were statistically closer to the means than those of the standing shoot leaves. The diurnal photosynthesis rate curves of Salix gordejevii were closely related to environmental factors such as temperature, humidity, PAR, measured on the corresponding day. During three days of measurement, net photosynthesis rate of Salix gordejevii all culminated at 11:00am, and the only difference between the two classes was in the peak values. The time when other peaks appeared was largely affected by environmental factors of the corresponding days. With regard to the peak value appeared at 11:00 am, the regenerated shoots were lower than the standing ones. This phenomenon might be a result of greater respiration rate of the regenerated shoots. It may be noteworthy that population photosynthesis ability of the regenerated shoots was higher than that of the standing shoots, though net photosynthesis rate of a single leaf of the regenerated shoots was lower than that of the standing ones at a certain time, because the regenerated shoots had an advantage statistically over the standing shoots in leaf blade area as well as total number of leaves.