Historic wooden buildings are a symbol of China’s “culture of wood” and require extraction of forest resources for their renovation. In the 21st century, natural resources are limited globally, and sustainable solutions are needed. In this study, we established a new method to connect building and forest sites for efficient utilization of limited forest resources for the renovation of historic buildings. We obtained measurements of large wooden components from Shenyang Imperial Palace. We also performed morphometric analyses on 47 thinned, old-growth larch trees to determine the relative taper curve, and selected 108 standing trees for simulation of the tree-height curve in the Mt. Changbai area, Jinlin Province, Northeast China. On the basis of forest metrology, we established an upper tree prediction method. By measuring the diameter at breast height (DBH) alone, we could compare size information (
Environmental protection has become one of the most urgent contemporary issues. Understanding the relationship between humans and nature requires that the wooden heritage buildings, a global concern, be considered the most important wealth for individuals who constantly reflect on their roles in nature (
As of 2010, 29 world cultural heritage sites have been approved in China, including 14 timber-frame buildings. China includes 1080 historic building complexes that are listed as protected sites, more than half of which are timber-frame buildings. The International Council on Monuments and Sites (ICOMOS) under the auspices of the United Nations Educational, Scientific and Cultural Organization (UNESCO) established the “principles for the preservation of historic timber structures” that include the preservation of the “same tree species”, “tree quality” and “building techniques” (
Recently, there has been a precipitous decrease in the production of large-diameter, high-quality wood due to social and economic changes. In 1998, the Chinese government implemented the Natural Forest Conservation Projects (NFCP) policy in an effort to promote forest management activities that prevent further deterioration of these resources (
Efficient utilization of natural forest resources is the key issue in renovating historic wooden buildings, and the amount of wood required from standing trees needs to be accurately assessed. Methods for estimating the upper stem diameter have been used by many researchers (
The objective of this research was to develop a method for the identification of standing tree branches using the forest measurement techniques to obtain the large wood components required for the renovation of the Shenyang Imperial Palace. By using this method and the data acquired from the measurements of the building sites, we could predict the required standing tree size for the renovation of the Shenyang Imperial Palace. Such prediction will facilitate compatibility between building conservation and forest management and help promote sustainable management of historic wooden buildings in China.
Two steps were taken to ensure consistency between the types of wooden structures that comprised the Shenyang Imperial Palace and the tree species present in the Mt. Changbai forest site: (1) measurement of wood structures and data collection from Shenyang Imperial Palace (building site); and (2) field work in the natural forest in the Mt. Changbai area (forest site).
The Shenyang Imperial Palace is located in northeast China. Built in 1624-1625 (Qing Dynasty), the palace was catalogued as the 28th cultural heritage site of the UNESCO World Heritage Committee’s Ming and Qing Imperial Palace expansion projects, comparable to the Forbidden City in Beijing. The total land area occupied by the palace is approximately 0.6 km2 and includes 67 buildings (
Three-dimensional information (length, width, height) of wooden components was measured to determine the size of timbers that would be necessary for the renovation of Shenyang Imperial Palace. According to different architectural types, 28 representative buildings, including 4 major categories (column, beam, purlin, and tie-beam) were selected in this research. The remaining buildings having the same architectural features and forms of the 28 representative buildings were not measured.
Morphometric measurements of each large wooden component were obtained on the basis of the following sources (
The building plans, including the floor plan, building-section plan, and cross-section plan (scale: 1:30, 1:40, and 1:50, respectively), drawn by Tianjin University.
On-site measurement of the bottom diameter of the eave column of each of the 28 buildings in the palace complex to verify the accuracy of the data measured on the plan (
Assuming that each large wooden building component was constructed using a single raw wooden column, and that the cross-sections of some wood components were square or polygonal, the maximum diagonal cross-section was calculated for each wooden component to estimate the diameter of the raw timber required.
Old-growth larch (
As per the UNESCO guidelines, sites at Huang Songpu Forest Farm in the Baihe Forest District of Jilin Province (lat. 42°08’21”N, long. 128°16’53”E) were selected for allometric measurement. These sites are located 10 km north of the Mt. Changbai Biosphere Reserve area (
Two adjacent sub-compartments with a total area of 6.57 ha were selected due to the first thinning activities conducted by Huang Songpu Forest Farm. Both the sub-compartments were representatives of natural, old-growth, multi-storied coniferous forest in northeast China. These forested areas are dominated by Changbai larch (
Forty-seven trees were felled, and the total height of each was measured to the nearest 0.03 m. Diameter outside bark (DOB) was measured at breast height (DBH, 1.3 m). DOB was also measured at intervals of 2 m along the length of the stem, beginning at 0.3 m. The DOB at 1/10 tree height was recorded to create a relative taper curve. The maximum tree height (34.7 m), maximum DBH (67.8 cm), and maximum diameter at 1/10 tree height (58.2 cm) of the 47 trees sampled were recorded. In addition to the 47 thinned trees, the DBH and height of 61 standing trees in the same field area were measured. In total, 108 standing old-growth larch trees were measured to calculate the tree height curve.
The relationship between tree height and DBH is considered to define the tree height curve (H-D). The Henricksen equation was applied to simulate the tree height curve (
where
The tree-height curve of
Relative taper curve is the mathematical expression of the change in stem diameter as a function of stem height, which is calculated on the basis of tree conditions (
where
where
Measured field data (
where
Assuming that wooden tree parts are cylindrical, the length of a trunk can be considered to be equal to the height from the ground, and the diameter can be considered to be equal along the length of the tree. Tree mensuration data were converted into 2 variables of a standing tree. The variables DBH,
DBH and
Total tree height and
The relative tree height at 1.3 m and
DBH and relative diameter at breast height were used to deduce
Relative tree height at
Known
The information on wooden components from the building site and trees from the forest site were well connected; however, for renovation purposes, sapwood with bark could not be included as their physical and chemical properties are not suitable for construction. Therefore, the values of sapwood and bark were recorded together. For each sample, two perpendicular lines intersecting at the centre were measured in order to derive four sapwood with bark values; corresponding stem diameter values were also recorded. In all, 52 sets of paired data were measured.
The criteria for model evaluation in this research followed recommendations by
where
Statistical results (
The basic criteria for the selection of large wooden components used for the statistical analyses in this study were length ≥ 4 m and diameter ≥ 50 cm. A total of 368 large wooden components were calculated from the study materials, and these data were segregated and tallied by length and diameter in 1-m and 2-cm intervals, respectively (
The relationship between stem diameter value and sapwood with bark value is shown in
where
The range of sample DBH values varied from 23.6 to 67.8 cm, and tree height ranged from 21.7 to 36.8 m (
where
The third- through sixth-order equations were expressed as (
Segmented polynomial models appear to be more accurate than other model formulations for estimating tree diameter (
Overall statistics of fit (
The diameter of a tree’s upper section could be considered as a desirable size for wooden building components, because the upper diameter is considered to produce the maximum timber size. The derivation process presented in the methods (using
For example, when the DBH of a standing tree is 50 cm (
By using the information presented in
Tree samples collected from the forest had some limitations. For example, the largest tree had a length of 34.7 m and DBH of 67.8 cm. Thus, the diameter class under 67.8 cm can be estimated accurately, but estimation of larger trees may be of limited accuracy. We separated 47 tree samples into 2 groups based on
According to our experimental results, availability of large-size timber material in China is unlikely to be sufficient to meet the requirements of historic renovation. This problem is not exclusive to China; it is relevant in other countries where wooden buildings play an important historical role. In Japan, obtaining good-quality wood from natural forests is a serious problem. Former conservators used alternative tree species that could be obtained easily when the preferred tree was not available (
Our results (
This research developed an efficient method for identifying upper tree diameter based on natural forests in the Mt. Changbai area, northeast China. By applying this method, we transferred the information on wooden components from a historic building site into DBH information on standing trees and estimated available standing tree resources for the renovation of the Shenyang Imperial Palace. Nevertheless, further attempts to bridge the sometimes-contrasting interests of building renovation and forest management are required.
This study was funded by a Grant-in-Aid for Scientific Research, Scientific Research-A, No. 20240074 (2008-2010) and No. 23240113 (2011-2013) from the Japan Society for the Promotion of Science. We would like to thank Sun Chen, Marcin, and Yang Jian for their efforts on this paper; Sato Juri and Assist. Prof. Terada for their kind advices; and Prof. Yin Mingfang and their collegues for support in the field work.
Relationship between stem diameter and sapwood with bark value.
Tree height curve.
Comparison of different relative taper curves.
Number of
Number of large-sized wooden components from Shenyang Imperial Palace.
Diameterclass (cm) | Length (m) | Total | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
4-5 | 5-6 | 6-7 | 7-8 | 8-9 | 9-10 | 10-11 | 11-12 | 12-13 | 13-14 | ||
50-52 | 12 | - | 4 | 10 | - | 8 | - | - | - | - | 34 |
52-54 | 32 | 8 | - | 2 | - | - | - | - | - | - | 42 |
54-56 | 20 | - | 8 | 4 | - | - | - | - | - | - | 32 |
56-58 | - | 6 | 4 | - | - | - | - | - | - | 12 | 22 |
58-60 | - | 12 | 32 | - | - | - | - | - | - | - | 44 |
60-62 | - | - | - | - | - | - | - | - | - | - | 0 |
62-64 | - | - | 12 | 14 | - | - | - | - | - | - | 26 |
64-66 | - | 16 | - | - | - | - | - | - | - | - | 16 |
66-68 | 6 | - | - | - | - | - | - | - | - | - | 6 |
68-70 | - | - | - | 26 | - | - | - | - | - | - | 26 |
70-72 | - | 6 | - | - | - | - | 12 | - | - | - | 18 |
72-74 | - | - | - | 8 | 6 | - | 2 | - | - | - | 16 |
74-76 | - | - | 6 | 12 | - | 16 | - | - | - | - | 34 |
76-78 | - | - | 8 | - | - | - | - | - | - | - | 8 |
78-80 | - | - | - | - | - | - | 18 | - | - | 6 | 24 |
80-82 | - | - | - | - | 18 | - | - | - | - | - | 18 |
82-84 | - | - | - | - | - | - | - | - | - | - | 0 |
84-86 | - | - | - | - | - | 2 | - | - | - | - | 2 |
Total | 70 | 48 | 74 | 76 | 24 | 26 | 32 | 0 | 0 | 18 | 368 |
Segmented stem-fit statistics of for relative taper curve simulations.
Equation | B | SEE | FI |
---|---|---|---|
Third-order | -0.019 | 0.0694 | 0.8271 |
Fourth-order | -0.0071 | 0.0602 | 0.8441 |
Fifth-order | -0.0081 | 0.0531 | 0.8411 |
Sixth-order | -0.0046 | 0.0465 | 0.858 |
Upper diameter prediction for a given tree height.
DBH(cm) | Upper tree diameter prediction (m) | ||||||
---|---|---|---|---|---|---|---|
h = 3 | h = 4 | h = 5 | h = 6 | ... | h = 19 | h = 20 | |
40 | 33.4 | 31.6 | 30.6 | 30 | … | 18.8 | 17.6 |
42 | 35.1 | 33.2 | 32.1 | 31.4 | … | 20.1 | 18.9 |
44 | 36.8 | 34.7 | 33.5 | 32.9 | … | 21.4 | 20.2 |
46 | 38.5 | 36.3 | 35 | 34.3 | … | 22.7 | 21.5 |
48 | 40.2 | 37.9 | 36.5 | 35.8 | … | 24 | 22.7 |
50 | 41.9 | 39.5 | 38 | 37.2 | … | 25.3 | 24 |
… | … | … | … | … | … | … | … |
70 | 59.1 | 55.5 | 53.2 | 51.8 | … | 38.4 | 36.8 |
80 | 67.8 | 63.6 | 60.8 | 59.1 | … | 45 | 43.3 |
90 | 76.5 | 71.7 | 68.5 | 66.5 | … | 51.7 | 49.9 |
100 | 85.2 | 79.8 | 76.2 | 73.8 | … | 58.4 | 56.4 |