Effects of planting density and mixed proportion on growth form quality and spatial utilization ability of Fraxinus mandshurica

Objective By exploring the changing principle of growth, form quality and spatial utilization ability under different planting densities and mixed species proportions of Fraxinus mandshurica plantations, this paper aims to provide theoretical basis for cultivating big diameter wood of Fraxinus mandshurica plantations.

Method Taking pure Fraxinus mandshurica plantations with 10 000, 4 400, 2 500 and 2 200 tree/ha planting density, and mixed Fraxinus mandshurica plantations of 1 line Larix olgensis ∶ 1 line Fraxinus mandshurica and 3 line Larix olgensis ∶ 3 line Fraxinus mandshurica with 2 500 tree/ha planting density, which was planted in 1998 from Maoershan Forest Farm of northeastern China as materials, growth index, form quality index and spatial utilization ability index were investigated and comprehensive evaluation value was calculated by improved hierarchical analysis method.

Result The growth index, form quality index and spatial utilization ability index of pure Fraxinus mandshurica plantation with 4 400 and 10000 tree/ha density reduced by 3.15%, 2.58% and 8.62%, 2.58%, respectively than that of pure Fraxinus mandshurica plantation with 2500 tree/ha density, and that of Fraxinus mandshurica plantation with 2 200 tree/ha density increased by 21.89%, 7.41% and 2.94%, respectively than that of pure Fraxinus mandshurica plantation with 2 500 tree/ha density. The growth index, form quality index and spatial utilization ability index of mixed plantations with 1 line Larix olgensis ∶ 1 line Fraxinus mandshurica and 3 line Larix olgensis ∶ 3 line Fraxinus mandshurica increased by 12.18%, 9.05%, 17.92% and 22.98%, 12.14%, 25.77%, respectively than that of pure Fraxinus mandshurica plantation with 2 500 tree/ha density. The rank of comprehensive evaluation value of Fraxinus mandshurica from big to small was mixed plantation of 3 line Larix olgensis ∶ 3 line Fraxinus mandshurica, pure plantation with 2 200 tree/ha density, mixed plantation of 1 line Larix olgensis ∶ 1 line Fraxinus mandshurica, pure plantation with 2 500 tree/ha density, pure plantation with 4 400 tree/ha density and pure plantation with 10 000 tree/ha density.

Conclusion The individual quality of Fraxinus mandshurica improves significantly with the decrease of density in pure Fraxinus mandshurica, and raised significantly in Larix olgensis-Fraxinus mandshurica mixed plantation, it should be suggested to plant the mixed plantation of 3 line Larix olgensis ∶ 3 line Fraxinus mandshurica with 2 500 tree/ha density.