帽儿山地区杂木林更新演替趋势分析

采用大数量小样方网格分层取样法和分层株数法,对帽儿山地区杂木林林地4种主要树种土壤种子库储量及种群结构进行了调查分析。结果表明:水曲柳(Fraxinus mandshurica)、五角槭(Acer mono)、蒙古栎(Quer-cus mongolica)和胡桃楸(Juglans mandshurica)种子分别占种子总储量的86.3%,7.3%、4.1%和2.4%。水曲柳、五角槭种子在Oe层中的储量显著高于Oi层和A层(P<0.05),完整种子比例随土壤深度的增加而减少;蒙古栎种子在Oe层的储量显著高于A层(P<0.05),Oi层和A层无显著差异;各层土壤中胡桃楸种子储量之间无显著差异。水曲柳和五角槭种子储量能够满足天然更新的需要,蒙古栎和胡桃楸种子储量对天然更新有限制作用。杂木林中除山杨胸高断面积占2成外,其它树种(蒙古栎、水曲柳、胡桃楸)所占比例均在1成左右。水曲柳、蒙古栎分层株数比为:更新层>主林层>演替层;五角槭分层株数比为:更新层>演替层>主林层。水曲柳、蒙古栎和胡桃楸幼苗向幼树转化困难,是其更新受限的原因之一。如果不加人工干预,该地区杂木林将演替为以五角槭占优势的林分。

Natural Regeneration and Succession in Natural Mixed Forests in Maoershan Region, Heilongjiang Province

Soil seed banks and population structure were surveyed by the methods of stratified sampling and layered counting to better understand the regeneration and succession in broad-leaved forests in Maoershan region,Heilongjiang Province.In the seed banks,the seeds of Fraxinus mandshurica,Acer mono,Quercus mongolica and Juglans mandshurica accounted for 86.3%,7.3%,4.1% and 2.4%,respectively.The seed storage of F.mandshurica and A.mono in decomposed organic layer were significantly higher than that in undecomposed organic layer and humus layer(P<0.05).The percentage of morphologically intact seeds reduced as the depth increased in the seed banks.The seed storage of Q.mongolica in decomposed organic layer were significantly higher than that in humus layer(P<0.05),and there was no obvious difference in seed storage between undecomposed organic layer and humus layer.An insignificant difference was observed in seed storage of J.mandshurica in different horizons.In the seed banks,the seed storage of F.mandshurica and A.mono could meet the requirements for natural regeneration,while the seed storage of Q.mongolica and J.mandshurica appeared to limit natural regeneration.The basal area of Populus davidiana accounted for 20% of the total of the mixed forest,while that of the other species accounted for 10% respectively.The ratios of the number of F.mandshurica and Q.mongolica in different layers were highest in regeneration layer,followed by upper layer and succession layer;those of A.mono exhibited regeneration layer,successive layer,and upper layer in descending order.The seedlings of F.mandshurica,Q.mongolica and J.mandshurica are hard to grow into successive layers,which is one of the reasons for limiting the nature regeneration.In the future,F.mandshurica and A.mono will become dominant species in the natural mixed forests in Maoershan region.