樟子松人工固沙林衰退的主要特征

针对辽宁省章古台地区樟子松人工固沙林出现的衰退枯死现象，系统地研究了樟子松人工固沙林衰退的主要特征,结果表明，衰退的樟子松人工固沙林外貌景观呈灰绿色，针叶纤细，开花结实率低，平均单株球果数量为10．4～16．5个，成熟种子千粒重为6．96～7.39g，种子空粒、涩粒较多．生长季内2年生针叶营养元素季节变化规律相似，但N、P含量下降，K含量明显增高，表明养分循环失调；衰退林分2年生针叶叶绿素含量较高，健康林分1年生较高且增幅较大．松枯梢病的侵害是樟子松人工固沙林衰退的最明显标志．林分衰退后，树高和胸径生长量下降明显，林分胸径分布结构“左移”(径级小的株数增多)，衰弱(亡)木数量增加了15.9％～27．2％；根量分别减少了22．9％～28．9％。其中吸收根减少量最大。

Major features of decline of Pinus sylvestris var.mongolica plantation on sandy land

In view of the decline of man-made sand-fixation forest of Pinus sylvestris var. mongolica in Zhanggutai sand land of Liaoning Province, this paper studied the major characteristics of the decline. The appearance of the declining man-made sand-fixation forest of Pinus sylvestris var. mongolica was grey green, its needle leaf was very thin, the blooming and fruiting rate was low, the average quantity of cones per tree was only 10.4-16.5, with only 6.96 g to 7.39 g per thousand seeds, and there were many empty and astringent seeds. The seasonal dynamics of nutrients in 2-year-old pine needle leaf was similar, i.e., the N and P contents decreased, while K content increased, showing that the nutrient cycle was imbalance. The chlorophyll content in 2-year-old needle leaf of declined forest was high, while that in 1-year-old healthy forest was also high but with a wide increasing range. The infected harm of shoot blight was the clearest mark to the decline of man-made sand-fixation forest of Pinus sylvestris var. mongolica. After the forest declined, the height and the DBH of the pine trees decreased evidently, and the structure of DBH distribution moved "left". The quantity of weak pine trees increased by 15.9%-27.2%, the roots decreased by 22.9%-28.9%, and the absorbing roots (diameter < 0.5 cm) decreased most seriously.