大兴安岭森林火灾对森林生态系统的影响

Influence of forest fire disaster on forest ecosystem in Great Xing’anling.

198 7年春发生在大兴安岭北部的森林火灾 ,造成了巨大的损失 .人们关心火灾对森林生态系统的影响 .我们通过较全面的调查研究 ,得出一些基本的结论 :①经重度火烧的林地 ,兴安落叶松 (Larixgemelinii)与樟子松 (Pinussylves trisvar.mongolica)的大径级树木未被烧死 ,而山杨 (Populusdavidiana)、白桦 (Betulaplatyphylla)在中度火烧情况下就全部死亡 .②火灾后 ,形成了大面积的天然幼龄林 ,主要是白桦的萌芽更新 .白桦的实生苗虽也很多 ,但生长慢、难成林 .而落叶松因缺少种源则难以更新 .樟子松在各种火灾等级的樟子松林地上都有良好的更新 .③落叶松林火烧后的 1 0年中 ,生长率降低 ,以后恢复到正常状态 ,但生长量有所提高 .樟子松林重度火烧后生长率明显降低 ,但生长量显著提高 .④火烧对森林群落的植物多样性影响不大 .⑤火烧后的 3年内 ,斜陡坡与阳坡土薄处 ,植被恢复慢 ,水土保持能力大为降低 ,侵蚀强度大 ,后来形成较多荒山 .而水分条件好的大面积谷地、缓坡地植被恢复较快、环境变化不大 .⑥火烧迹地的土壤有机质大为降低 ,矿质养分也明显降低 ,坡度越大的地段 。

A serious fire disaster took place in the northern forest region of the Great Xing'anling in northeastern China in the spring of 1987 and this forest fire resulted in serious losses. Now the effect of the heavy fire on forest ecosystem has been widely concerned, while this problem was seldom discussed in the past years. After the all round investigations from 1987, some conclusions are summarized as follows: (1) In the forest lands suffered from the serious fire, large diameter trees of Larix gemelinii and Pinus syvestris var. mongolica have not been burned to death, but all of Populus davidiana and Betule platyphylla died in the mid degree fire. (2) After the fire disaster, large areas of natural young forests were developed, which mainly originated from the sprouts of Betula platyphylla , and there was good natural regeneration in the Betula platyphylla and Pinus syvestris var. mongolica stands. (3) After Larix gemelinii stands were burned, the growth rate decreased firstly, and then restored to the normal level, but the growth volume increased. After the Pinus syvestris var. mongolica stands suffered from the serious fire, growth rate always decreased but the growth volume increased obviously. (4) Effect of the fire on plant diversity was very slight. (5) During the three years after fire disaster, vegetation in the thin soil of steep and southern slopes was restored slowly, and soil and water conservation ability reduced sharply. The soil erosion on these slopes was intensive and these slopes mostly developed into barren mountains later. Vegetation restored quickly in the flat and gentle slopes with good water condition, but environment has little changes. (6) Organic matter and mineral nutrition in the forest soil where fire has happened reduced greatly. The steeper the slope is, the poorer the soil is.