樟子松人工固沙林天然更新障碍因子分析

采用比较分析与野外试验的方法，对沙地樟子松人工林天然更新障碍因子进行了分析。结果表明，影响天然更新的环境因子主要有郁闭度、枯枝落叶层、植被盖度和立地条件。天然更新的障碍主要是由于引种地降雪覆盖少，温度偏高等原因，使土壤蒸发大、苗木蒸腾大，造成水分的亏缺，从而导致1－2年生更新幼苗死亡。针对樟子松人工固沙林天然更新障碍及其更新特点，提出在适宜立地上采取人工促进措施，如埋土、灌水等方法，以保证天然更新有效进行。

Analysis of natural regeneration barriers of Pinus sylvestris var.mongolica plantation on sandy land

By employing comparison analysis, and field experiment of watering and soil-covering before overwintering for seedlings, the barriers of natural regeneration for Mongolian pine plantations on sandy soil were identified. The experimental area was divided into 3 parts according to the state of natural regeneration. Crown closure, litter, understory coverage, and site condition were the factors which affect natural regeneration. Water deficit, but not low temperature during overwintering, is the key factor that limits survival for 1-2 years old seedlings in plantation area. The water deficit is due to higher air temperature, less accumulated snow, higher soil evaporation, higher plant transpiration in plantation area than in the area in which Mongolian pine is naturally distributed. Based on the above research, it is necessary to take effective artificial measures to promote its natural regeneration so as to guarantee its successful development. The following measures are recommended: 1) covering the 1-2 years old seedlings with soil before wintering, 2) irrigating seedlings before wintering, 3) suitable forest harvest, e.g., belt clear-cutting, or patch cutting, 4) planting the pine with broadleaf species, 5) protecting forest stands from livestock grazing, seed collecting and litter gathering.