Growth performance and its influence of Fraxinus mandshurica after 20 years of introduction and planting

  Objective  This study was conducted to clarify the adaptability and growth performance of Fraxinus mandshurica after 20 years of introduction and planting and its impact on species diversity of the community, so as to provide scientific basis for the introduction and site environment selection of Fraxinus mandshurica, and the biodiversity protection of the introduced site.

  Method  By the method of typical sample investigation, 3 types of Fraxinus mandshurica (scattered individuals, pure forest and mixed forest) and 2 other community types (broadleaved mixed forests and gully meadows) were investigated in Labagoumen Nature Reserve in Beijing to analyze the individual adaptability, growth performance of Fraxinus mandshurica and the species diversity of different community types. The sampled Fraxinus mandshurica had been introduced and planted for 20 years in the study site.

  Result  (1) The survival and preservation rate (Sp) of Fraxinus mandshurica was greater than 90% in different sampling types, and some individuals had begun to grow and blossom normally; (2) morphological indexes such as DBH, tree height, crown width, trunk straightness and crown length ratio of Fraxinus mandshurica individuals were different in varied sampling types, the order of vigorous degree (B) was as follows: Fraxinus mandshurica scattered individuals > Fraxinus mandshurica mixed forest > Fraxinus mandshurica pure forest; (3) the species diversity of Fraxinus mandshurica pure forest and Fraxinus mandshurica mixed forest was lower than that of broadleaved forest and gully meadow community types.

  Conclusion  (1) Fraxinus mandshurica has entered the middle-age stage and shows strong environmental adaptability and high survival rate after 20 years of introduction and planting. The growth performance of scattered individuals at the forest edge and roadside was better than that of individuals in mixed forest and pure forest due to higher canopy density and individual competition of the latter; (2) Fraxinus mandshurica has strong shade tolerance and competitiveness. After entering the middle age, it forms a high canopy density in the pure and mixed Fraxinus mandshurica forests, resulting in the reduction of species in the shrub and grass layer, which is not conducive to the protection of local species diversity; (3) when introducing and planting Fraxinus mandshurica in Labagoumen Nature Reserve, the abandoned farmland in the lower part of the gully or the greening land on both sides of the road should be selected, the gully meadows and other secondary forest environments are not suitable for planting Fraxinus mandshurica.