基于生物多样性保护的兴安落叶松与白桦最佳混交比例——以阿尔山林区为例

选取内蒙古阿尔山林区7种不同混交比例的松桦混交林,包括落叶松纯林、白桦纯林及5种不同比例的混交林为研究对象。对植物和昆虫种群丰富度、多样性进行了研究,并对种群在乔木层混交状况梯度下的分布进行了分析。结果表明:植物和昆虫种群分布受乔木层混交状况影响显著。同时,郁闭度能改变其分布状况及决定于松桦比例。兴安落叶松和白桦混交比例介于5∶5和7∶3之间时最有利于森林多样性,是进行林分疏伐的理想模式。

The optimum mixture ratio of larch and birch in terms of biodiversity conservation: a case study in Aershan forest area

To find the optimum mixture ratio of larch (Larix gmelinii) and birch (Betula platyphylla), seven forest types were set in Inner Mongolia, including pure larch stand, pure birch stand, and five mixed stands with various tree proportions. Each forest type had three stands as replicates. Species richness and diversity of plant and insect populations were investigated and analyzed by traditional community investigation and manual collection. For the plant community, 88 species were recorded and the dominant communities included Compositae, Rosaceae, Ranunculaceae, Papilionaceae, Ericaceae and Pinaceae. The dominant populations were Carex chingannensis Litw., Lolium perenne L., Fragaria orientalis Lozinsk., Equisetum palustre L., Geranium dahuricum DC., Galium boreale L. while the rare populations included Heracleum moelledorffi, Ligularia fischeri, Pedicularis rubens and Viola acuminate. For the insect community, 147 species were recorded. Lymantria dispar L., Loxostege sticticalis L., Chilo suppressalis (walker), Sidemia spilogramma Rambur, Chrysomelidae, Muscidae, Staphylinidae, Eusilpha sp., Nitidulidae, Ips subelongatus Motschulsky were found as the dominant populations while Tomicobia seitneri(Ruschka)and Sipyloides sipylus were classified as rare speices. As the birch mixture in mixed forests increased, the species richness of plant and arthropod first increased and then decreased and peaked in L70B30 forests. The diversity of them had similar pattern as species richness. The distribution status of plant and insect populations along the gradient of birch mixture was also examined by the application of canonical correspondence analysis (CCA). The explaining environmental factors included mixture proportion (quantified by the mixture of birch), canopy closure, stand slope and soil organic matter (%). The results showed that the distribution of plant communities was well reflected by the CCA analysis. 34.1% and 37% of the plant-environment relation was explained by axis 1 and 2, respectively. Birch mixture (BM) had significantly negative correlation with axis 1 while the canopy closure (CC) had a significantly positive correlation. In terms of the insect diversity, axis 1 and 2 explained 34.8% and 28.1% of the insect-environment relation while BM and CC also had similar correlations with axis 1 and 2. The results showed that most populations were significantly affected by the mixture status and canopy closure, which was also significantly decided by the composition status of canopy layer. In addition, the stand slope can also change their distribution status. These results also indicated that the diversity of plants and insects was highest when the mixture ratio of larch and birch was between 5: 5 and 7: 3, which should be the optimum mixture ratio in thinning practices. The present study is to provide theoretical base to improve the forest management, including how to quantify and control the thinning intensity. Generally, the relation of diversity and forest ecosystem stability was considered as positive which meant that the stability will increase with the diversity level. Therefore, the present study provides a new way to improve the health level of boreal forests in northeastern China. The forest manager could carry out various practices to transform the simple structure of forests, especially for the man-made forests and to keep and increase the forest health in this area.