1987年大兴安岭特大火灾后北坡森林景观生态恢复评价

Evaluation of landscape restoration in the northern slopes of Great Xing'an Mountains after the 1987 catastrophic fire

通过空间直观景观模型(LAND IS)来探讨大兴安岭北坡1987年特大森林火灾后,在目前这种恢复方案下以及完全依靠天然更新下森林景观的长期动态,通过对比研究来评价目前所采取的恢复措施是否能够有效地恢复森林资源。研究结果表明:1987年大火后所采取的恢复措施可以在很大程度上增加针叶树种在该区所占的比例,而相应地降低阔叶树种的比重。由于在目前的恢复措施下,不仅大面积地种植针叶树种,同时也采伐了大量的成、过熟林,使落叶松和樟子松的蓄积量在开始阶段不仅没有增加,反而有大幅度的下降。但最终,所更新的幼苗逐渐成材,落叶松和樟子松的蓄积量逐渐超过天然更新下的。在演替前期,白桦的蓄积量在这2种模拟方案下相差不大;而在演替后期,白桦在天然更新方案下的蓄积量要高于在目前恢复措施下的蓄积量。另外,物种在不同的区域的变化动态又有较大的差异。在重度火烧区,由于人为种植大量的针叶树种,使它们所占的面积比例明显高于完全依靠天然更新下其在重度火烧区所占的比例;而阔叶树种则相反,在完全依靠天然更新方案下所占的面积百分比明显高于在目前恢复方案下的比例。而在未火烧和轻中度火烧区,由于火后人为采伐大量的落叶松和樟子松,使这2个树种在该区所占的比例在开始100多年里要低于完全依靠天然更新下的比例,随后逐渐高于天然更新下所占的比例,但相差不大;阔叶树种则正好相反。另外,目前恢复方案不仅极大地改变了主要物种在该区所占的比例,而且还明显的影响了它们的空间分布格局。

We used the LANDIS model to study the effects of two management scenarios （current restoration strategy and natural regeneration） on the long-term forest dynamics in the northern slopes of Great Xing＇an Mountains after the catastrophic fire in 1987. The results showed that current restoration strategy increased the abundance of coniferous species （larch （Larix gmelinii） and Mongolian Scotch pine （Pinus sylvestris var. mongolica）） in the study landscape due to large quantity of coniferous seedlings planted, and the amount of broad-leaved species （white birch （Betula platyphylla）） decreased. Under current restoration strategy, plenty of matured coniferous forest was harvested within 10 years after the 1987 fire, which resulted in significant decline in the timber volume. As these coniferous seedlings planted soon after the 1987 fire grew older with simulation years, the total volume of coniferous species increased and exceeded that under natural regeneration after about 60-80 years. In addition, white birch （B. platyphylla） had a similar proportion in the early stage of succession under the two management scenarios. However, the abundance was lower under current restoration strategy than that under the natural regeneration strategy in the later stage of succession. Furthermore, vegetation dynamics differed significantly between the severely burned areas and other areas. In severely burned areas, since coniferous seedlings were planted under the current restoration strategy, the abundance of larch （L. gmelinii） and Mongolian Scotch pine （P. sylvestris var. mongolica） was higher than that under the natural regeneration strategy. Conversely, the abundance of white birch （B. platyphylla） was lower under the current restoration strategy. In other areas, due to timber harvesting under current strategy, the abundance of larch and Mongolian Scotch pine was lower than that under the natural regeneration strategy in the first 100 simulation years, and then became slightly higher than that under natural regeneration. However, white birch was more abundant in the early stage of simulation and less abundant in the later stage under the current restoration strategy than that under the natural regeneration strategy in other areas. In addition, the current restoration strategy not only changed species abundance, but also had great influence on species distribution.