冀北山地亚高山地区阴坡白桦中幼龄林生长状况分析

Analysis young forest growth conditions in northern Hebei subalpine mountain birch in shady areas

为进一步提高林分质量，实现森林可持续经营的目的，在野外调查的基础上，采用对优势木和平均木解析的方法，研究了冀北山地亚高山地区阴坡中幼龄白桦林不同发育阶段的生长变化规律。结果表明：在0～20a间，树高、胸径、材积均处于高速生长的时期，并且从3个指标来看，优势木均比平均木达到最快生长的时期早，并通过对3个指标的平均生长量和连年生长量的对比分析，得出白桦优势木在10～15a间生长速度最快，平均木在15～20a间生长速度最快。速生期后，林分进入平稳生长的时期，连年生长量逐渐降低，平均生长量趋于平缓，并继续进入慢生期。

To further improve forest quality and achieve the purpose of sustainable forest management, on the basis of field investigation, the young birch growth variation at different developmental stages in the shady northern Hebei Mountain subalpine regions was studied by using the average and superior tree analytical method. The results showed that. in 0- 20 years, tree height, diameter breast height and volume remain a high-speed growth period and based on the three indicators, the superior tree enter the fastest growth period earlier than the average tree, and through contrastive analysis of the average growth of three growth indicators with that of successive years, it is found that the superior tree grows fastest during 10-15 years, while the average tree gvrows fastest during 15-20 years. After the fast-growing period, birch stand enters a stable growth period, with the annual increment decreased, and the average increment leveled off, and continues into a slow-growing period.