陕北黄土高原油松人工种群结实与更新

通过野外调查和室内试验,调查了陕北黄土高原半干旱、半湿润地区油松人工种群的结实特性、种子生活力、幼苗更新和生长状况等基本特征,分析影响油松人工种群生殖及更新的因素,确定了油松人工种群的天然更新边界.结果表明八个地区的油松都具有结实能力.对不同地区种子生活力和发芽率测定表明地区间差异不显著.由北向南,随年降水量的增加,油松球果长、宽、单果种子数、种子长、宽、千粒重逐渐增加.有活力种子的数量可以满足天然更新的需要.北部地区,种子落地后不能萌芽成苗,中南部地区种子落地后能萌芽成苗,但只有南部地区幼苗幼树生长良好,林下更新有效.影响油松人工种群更新的环境因素分析表明降水最是最主要限制因素.油松人工种群天然更新分界线应该在年降水量550 mm的等降水线左右.未来油松人工林培育应立足于降雨量大于550 mm的南部湿润半湿润地区,半干旱地区不宜再扩大油松人工林面积.

Regeneration and fruiting of Pinus tabulaeformis Carr. artificial forest in Loess Plateau of northern Shaanxi

For the purpose of identifying the regeneration potential of the species, the fruiting, seed germination, seedling survival and seedling growth were investigated at eight regions established in Pinus tabulaeformis artificial forest in Loess Plateau. The main factors affecting the natural regeneration and reproduction of Pinus tabulaeformis were analyzed. The boundary of natural regeneration was confirmed. The results show that Pinus tabulaeformis has potential to produce seeds in the eight regions. There are no significant differences in the viability and the germination of seeds. Cone length, width, average seed number, seed length, width and the weight per 1000 seeds are lower in the north region; the quality and quantity of cone and seed are better in the mid and south region. The number of seeds can meet the needs of natural regeneration. Seeds do not germinate after falling to the ground in the north region, while they do in the mid and south regions. Seedling and sapling grow well in the south region, and regeneration is effective. Different environmental factors affecting the natural regeneration were analyzed, with the annual mean precipitation being the most limiting factor. In the future, the artificial population should be cultivated in the humid and semi-humid regions, while the artificial population should not be expanded in the arid and semi-arid regions.