Forest Naturalness Evaluation Based On Relative Quantitative Reference Approach

Forest naturalness is an important indicator of forest health status and also an important foundation of close-to-nature forestry management.As a new research field,there are some deficiencies in evaluation index and methods.This study was carried out in Dasi forest region of Culai mountain to assess naturalness of seven main forest types. Nine indicators that reflected the stand characteristics were selected and the weight of each indicator was determined by principle component analysis(PCA). The naturalness of each indicator and the integrate index value of seven different forest types were calculated by means of the relative quantitative reference approach.The evaluation results of different forest types were compared to provide some theoretical reference for the close-to-nature forestry management.The main conclusions are as follows:(1) According to the scientific, objective, measurable,and sensitive principles,nine indicators of horizontal structural diversity, vertical structural diversity, Gleason index in shrub layer, Gleason index in shrub layer, cover of shrub, cover of herb, canopy density of arbor, forest regeneration and thickness of organic debris that reflected the stand characteristics were selected to to establish a scientific and reasonable index system. The combination of multiple indicators fully describes the difference between different forest types(2) The application of the relative quantitative reference approach to evaluate forest naturalness overcomes the lack of natural vegetation as a reference and eleminate the regional restrictions. Even if the forest is interfered by external factors such as climate change and its naturalness has been dynamic, this method is still applicable. The calculated forest naturalness is relative and can not exactly illustrate the naturalness of forest,The evaluation results are not universal and are comparable only to a certain research area.We can get different evaluation results if we use different indicators or have different understandings of forest naturalness.(3) The pure Larix gmelinii plantation with less human interference was selected as the reference stand and by means of the relative quantitative reference approach we got that the naturalness of different forest types from high to low was pure Larix gmelinii plantation(100%), Pinus tabuliformis and Robinia pseudoacacia mixed plantation(85.38%), pure Pinus densiflora plantation(81.74%), pure Pinus tabuliformis plantation(79.45%), pure Robinia pseudoacacia plantation(78.69%), Pinus tabuliformis and Quercus dentata mixed plantation(74.20%), Pinus densiflora and Platycladus orientalis mixed plantation(68.02%). Among the seven different forest types the pure Larix gmelinii plantation has the highest integrate naturalness index value,the Pinus densiflora and Platycladus orientalis mixed plantation has the lowest integrate naturalness index value and the integrate naturalness index value of other five forest types is around 80%.Therefore the naturalness of mixed forest is not always higher than pure forest,for example,the high stand density and the intense competition between trees in the Pinus densiflora and Platycladus orientalis mixed plantation leads to poor growth status,incomplete stand structure and low naturalness degree.(4) The nine indicators of forest naturalness in seven different forest types were compared and analysed and by exploring the differences between the natural status of seven forest types,we can provide a basis for close-to-nature forest management.To sum up,this research studied the establishment of naturalness evaluation,the evaluation methods and close-to-nature forestry.The relative quantitative reference approach is scientific and easy to operate.It provedes a new study perspective in forest naturalness evaluation and has Certain practical value.