Abstract
Establishing the tree volume table is an important aspect of forest inventory for managing the forest ecosystem. The traditional volume models used to build tree volume tables are time consuming and expensive, demanding huge labor and material resources. Aiming at the improvement of the current destructive, costly and time-consuming volume model, we propose a new non-destructive, low-cost and efficient method for calculating the tree volume model with high precision by using the electronic theodolite. For testing and comparing the accuracy of our model with the traditional model, we collected data of three main tree taxa including Platycladus orientalis (L.) Franco, Larix principis-rupprechtii Mayr and Populus spp. L. from different districts and counties of Beijing, China. We collected a total of 1750 tree samples (250 Platycladus orientalis, 300 Larix principis-rupprechtii, and 1200 Populus spp.) to establish our models; 721 pieces of accurate data (94 Platycladus orientalis, 149 Larix principis-rupprechtii, and 478 Populus spp.) were used as test samples, to evaluate the accuracy of the newly established volume models of three tree species (group). After that, the established volume models (unary/binary models) were compared and analyzed with the corresponding ministerial models for applicability and accuracy. The results showed that the difference between the data observed by the new method and the measurement data of parsing trees was not significant. The total relative error (TRE) and the mean system error (MSE) of the newly established unary/binary volume models were all within ±3%, satisfying the accuracy standard specified by the technical indicators. Compared with the ministerial models applied to the same data, our models’ performance and accuracy were higher (close to the field measurements). Our results also showed that the accuracy of ministerial models was lower than the required standards. It is a promising methodology to use the electronic theodolite non-destructive observation method to establish tree volume tables in the future, especially in areas where cutting is prohibited or restricted and there is a lack of tree volume tables. In addition, this method has also shown a great potential of applicability in forest ecology and environmental protection.
Highlights
Forest resources inventory plays an important supporting role in understanding the status quo of forests, changing laws, formulating forestry management plans, promoting the development of a green national economy and improving the establishment of a healthy ecological environment [1,2].Forests 2019, 10, 92; doi:10.3390/f10020092 www.mdpi.com/journal/forestsIdeally, the forest resource inventory requires the data of each individual tree, it is almost impossible to collect measurement data of each tree, especially over a large scale
A unary volume table is based on the regression relationship between the factor of diameter at breast height (DBH) and volume, while binary volume table is based on the DBH and tree height
Our method provides a scientific basis for objectively evaluating the current status of the three-tree species volume models
Summary
Forest resources inventory plays an important supporting role in understanding the status quo of forests, changing laws, formulating forestry management plans, promoting the development of a green national economy and improving the establishment of a healthy ecological environment [1,2].Forests 2019, 10, 92; doi:10.3390/f10020092 www.mdpi.com/journal/forestsIdeally, the forest resource inventory requires the data of each individual tree, it is almost impossible to collect measurement data of each tree, especially over a large scale. Forest resources inventory plays an important supporting role in understanding the status quo of forests, changing laws, formulating forestry management plans, promoting the development of a green national economy and improving the establishment of a healthy ecological environment [1,2]. Establishing volume tables and sampling theory has become important in forestry sciences. The standing tree volume table has become an important forestry basic meter [5]. In China, the standing tree volume usually includes a unary volume table and binary volume table [11]. The volume table used in Beijing (China) is basically established at the beginning of the continuous forest inventory system in China in the late 1970s
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