共查询到17条相似文献,搜索用时 0 毫秒
1.
The effect of heating on the hygroscopicity of Japanese cedar wood was investigated as a simple evaluation of thermal degradation
in large-dimension timber being kiln-dried at high temperatures (>100°C). Small wood pieces were heated at 120°C in the absence
of moisture (dry heating) and steamed at 60°, 90°, and 120°C with saturated water vapor over 2 weeks, and their equilibrium
moisture contents (M) at 20°C and 60% relative humidity (RH) were compared with those of unheated samples. No significant change was induced by
steaming at 60°C, while heating above 90°C caused loss in weight (WL) and reduction in M of wood. The effects of steaming were greater than those of dry heating at the same heating temperature. After extraction
in water, the steamed wood showed additional WL and slight increase in M because of the loss of water-soluble decomposition residue. The M of heated wood decreased with increasing WL, and such a correlation became clearer after the extraction in water. On the basis of experimental correlation, the WL of local parts in large-dimension kiln-dried timber was evaluated from their M values. The results indicated that the thermal degradation of inner parts was greater than that of outer parts. 相似文献
2.
Eiichi Obataya Sakae Shibutani Kensuke Hanata Shuichi Doi 《Journal of Wood Science》2006,52(2):111-114
Japanese cedar wood specimens were steamed at 80°, 100°, and 120°C over 14 days, and their equilibrium moisture content (M)
at 20°C and 60% relative humidity, longitudinal dynamic Young’s modulus (E), bending strength (σ
max), and breaking strain (ε
max) were compared with those of unheated specimens. Steaming for a longer duration at a higher temperature resulted in a greater
reduction in M, σ
max, and ε
max. The E of wood was slightly enhanced by steaming at 100°C for 1–4 days and 120°C for 1–2 days, and thereafter it decreased. The
slight increase in the E of sapwood was attributable to the reduction in hygroscopicity, while sufficient explanation was not given for a greater
increase in the heartwood stiffness. Irrespective of the steaming temperature, the correlations between M and the mechanical properties of steamed wood were expressed in terms of simple curves. M values above 8% indicated a slight reduction in E and s max, whereas M values below 8% indicated a marked decrease in the mechanical performances. In addition, the e max decreased almost linearly
with a decrease in the value of M. These results suggest that hygroscopicity measurement enables the evaluation of degradation in the mechanical performances
of wood caused by steaming at high temperatures. 相似文献
3.
Luciano Rodrigo Lanssanova Sebastião do Amaral Machado Alexandre Techy de Almeida Garrett Izabel Passos Bonete Allan Libanio Pelissari Afonso Figueiredo Filho 《Southern Forests》2019,81(2):167-173
This study evaluated the efficiency of taper functions and the application of mixed-effect modelling for diameter estimation along the stems of Tectona grandis. We sampled 266 trees of Tectona grandis, measuring the diameter at relative heights for volume determination, grouping the data according to three form-factor classes. Six taper functions were fitted, selecting the function with better fit performance. Six taper functions were fitted, selecting the function with better fit performance. The selected function was fitted in its basic formulation, and with the mixed non-linear modelling technique in different scenarios, and for the stem stratified in three portions of the total height. The precision and selection of the adjusted models were evaluated regarding the coefficient of determination, standard error of estimate, the Akaike information criterion, bias, quadratic error and absolute bias. According to the statistical criteria used, the model of Kozak was selected for the adjustments. For diameter estimation, the scenario with two coefficients as random effects provided an accuracy increase of 11.91%, and the mixed non-linear modelling better estimated the stem diameter for the stratified stems. In conclusion, the model of Kozak can be used to describe the stem shape of Tectona grandis, and the mixed-effect non-linear model approach was the best technique to estimate diameter along the stem of Tectona grandis. 相似文献
4.
Kotaro Zushi 《Journal of Forest Research》2006,11(5):351-358
Digital terrain modeling was used to evaluate landscape-level spatial variation of soil C and N storage and site productivity
in Japanese cedar (Cryptomeria japonica D. Don) stands. Soil C and N storage were measured in samples from surface soils (0–25 cm depth) of 29 Japanese cedar stands
in the 205-ha Myougodani watershed, Toyama Prefecture. The site index (C. japonica tree height at age 40 years) was used as a measure of forest productivity. Seven terrain attributes (elevation, slope gradient,
aspect, profile curvature, plan curvature, openness, and wetness index) were calculated from a digital elevation model. Soil
C and N storage were negatively correlated with slope gradient and positively correlated with openness. Variation in the site
index was closely related to the wetness index. The prediction models using terrain attributes as explanatory variables explained
50% of the variability in soil C storage, 53% of the variability in soil N storage, and 75% of the variability in site index.
This result demonstrated that this technique is useful for estimating the spatial distribution of soil properties and productivity
in forest landscapes. On the other hand, there was no correlation between site index and soil C and N storage. Use of the
prediction models in a geographic information system revealed that the spatial distribution of forest productivity differed
considerably from those of soil C and N storage. 相似文献
5.
We investigated the short-term and long-term mitigation of Al toxicity by Ca and Mg in pot trials of Japanese cedar (Cryptomeria japonica D. Don). We found that in the initial stages of treatment, Al toxicity at high Al concentration (5mM) was mitigated by Ca and Mg through the stimulation of antioxidant enzyme activities in needles. However, growth reduction occurred after 11 months exposure to Al despite the coexistence of Ca and Mg. Growth reduction was related to Al3+ activity in solution rather than the concentration of Ca and Mg. Therefore, when considering the influence of soil acidification on Al toxicity in forest ecosystems, it is important to consider not only the potential for mitigation of Al toxicity by base cations, but also the potential for factors in the soil solution to change the chemical form of Al. 相似文献
6.
Terumasa Takahashi Akiko Minami Yoshito Asano Tatsuaki Kobayashi 《Journal of Forest Research》1999,4(4):299-302
In order to clarify the effects of tree species on organic matter dynamics in soil, we investigated the amount of forest floor
material, leaf litter decomposition rate, soil chemical characteristics, soil respiration rate and cellulose decomposition
rate in a Japanese cedar forest (cedar plot) and an adjacent Japanese red pine forest (pine plot) established on a flatland.
The amount of forest floor material in the cedar plot was 34.5 Mg ha−1 which was greater than that in the pine plot. Because the leaf litter decomposition rate was higher in the pine plot than
in the cedar plot, it is likely that the difference in the amount of forest floor material between the plots is caused by
the difference in the leaf litter decomposition rate. The C concentrations of soil in the cedar plot were 1.2–2.1 times higher
than those in the pine plot. Soil pH(H2O)s in the cedar plot were significantly higher than those in the pine plot. The soil respiration rates and the rates of mineralized
C in the cedar plot byin vitro incubation were higher than those in the pine plot. From this result, it is assumed that soil organic matter in the cedar
plot was decomposed relatively faster compared with the pine plot. Furthermore, microbial activities, which were reflected
as cellulose decomposition rates in the cedar plot, were higher than those in the pine plot.
A part of this paper was presented at the 109th Annual Meeting of the Japanese Forestry Society (1998). 相似文献
7.
Kotaro Zushi 《Journal of Forest Research》2007,12(4):289-297
Digital terrain modeling and spatial climatic data have been used to estimate the spatial distribution of Japanese cedar (Cryptomeria japonica D. Don) forest productivity on a regional-scale. The study was conducted on Japanese cedar forests in Himi city, Oyabe city,
Takaoka city, and Imizu city (a total area of 683 km2) in northwestern Toyama Prefecture. On the basis of data from 146 sample stands, above-ground net primary productivity (ANPP)
was calculated from tree height, age, and density using existing ANPP conversion equations for Japanese cedar stands. Six
topographic factors (slope, profile curvature, plan curvature, openness, wetness index, and topographic radiation index) were
calculated from a 10-m cell size digital elevation model. Three climatic factors (annual mean temperature, annual total precipitation,
and annual maximum snow depth) were obtained from an existing spatial data set. Relationships between ANPP and environmental
factors were analyzed by regression tree models. For the tree model with ANPP as a dependent variable, four environmental
factors (annual mean temperature, wetness index, openness, topographic radiation index) were adopted as independent variables.
Annual mean temperature was the first split variable in this model and explained 25.5% of the total deviance in ANPP. Wetness
index, which represents soil moisture variation caused by lateral flow, explained 11.5% of the total deviance in ANPP. The
resulting tree model explained approximately half of the total deviation in ANPP and indicated that the spatial distribution
of Japanese cedar productivity was controlled by regional-scale interactions between climatic and topographic processes. A
high-resolution map of productivity was prepared by use of the ANPP prediction model and vegetation information obtained from
satellite data. 相似文献
8.
《Scandinavian Journal of Forest Research》2012,27(6):495-500
The leaves and leaf litter of Cryptomeria japonica D. Don was collected from April 1994 to March 1995 to describe the seasonal changes in nutrient concentrations in leaves and leaf litter. Nitrogen (N), phosphorus (P) and potassium (K) concentrations were in the order new leaves > old leaves > leaf litter, whereas calcium (Ca) concentration was in the order leaf litter > old leaves > new leaves during the whole year. N, P and K concentrations were at their highest during the new leaf growth phase, and then decreased as a result of the diluting effect and translocation, whereas Ca increased with time. Magnesium did not show any clear seasonal trend compared with other nutrients. N resorption efficiency was lower than P resorption efficiency. There were two nutrient resorption peaks, which could be attributed to high nutrient translocation to new leaves in the spring and to translocation from old leaves before senescence in the autumn. A significant correlation between N and P resorption was observed. 相似文献
9.
10.
Tomohiro Nishizono Kunihiro Tanaka Kazuo Hosoda Yoshio Awaya Yasuhiko Oishi 《Journal of Forest Research》2008,13(5):264-274
We analyzed data from 28 long-term experimental monitoring plots installed in Japanese cedar (Cryptomeria japonica D. Don) plantations in northeastern Japan to examine how site productivity and thinning practices relate to culmination in
stand growth. Site productivity and thinning practices in the plots were evaluated by site index (dominant tree height at
40-years old) and by cumulative thinning rate (cumulative thinning volume divided by cumulative gross production during the
entire period of measurement). Culmination of stand growth was evaluated by culmination age of the mean annual increment (MAI)
and its maximum value (Max MAI). Max MAI for the mean annual gross increment (MAIgross) and mean annual net increment (MAInet)
increased with increasing site index, but did not change with cumulative thinning rate. Culmination age for MAIgross decreased
with increasing site index, but did not change with cumulative thinning rate. Culmination age for MAInet decreased with increasing
site index. Additionally, culmination age for MAInet increased with increasing cumulative thinning rate in sites with a high
site index (>19.3 m) but not in those with a low site index (<19.3 m). These results indicate that thinning extends the culmination
age without changing Max MAInet under high site productivity. Therefore, thinning increases total net yield in sites with
high productivity based on a long-term perspective. 相似文献
11.
Estimation of the fine root biomass in a Japanese cedar (Cryptomeria japonica) plantation using minirhizotrons 总被引:1,自引:0,他引:1
Noguchi Kyotaro Sakata Tadashi Mizoguchi Takeo Takahashi Masamichi 《Journal of Forest Research》2004,9(3):261-264
We estimated fine root biomass in a Japanese cedar (Cryptomeria japonica) plantation using a min-irhizotron technique. Since data obtained from minirhizo-trons are limited to the length and diameter of fine roots observed on minirhizotron tubes, data conversion is necessary to determine the fine root biomass per unit soil volume or unit stand area. We first examined the regression between diameter squared and weight per unit length of fine roots in soil core samples, and calculated the fine root biomass on minirhizotron tubes from their length and diameter. Then we determined conversion factors based on the ratio of the fine root biomass in soil core samples to that on minirhizotron tubes. We examined calculation methods, using a single conversion factor for total fine root biomass in the soil for depths of 0–40cm (Cal1), or using four conversion factors for fine roots in the soil at 10-cm intervals (Cal2). Cal1 overestimated fine root biomass in the lower soil or underestimated that in the upper soil, while fine root biomass calculated using Cal2 better matched that in soil core samples. These results suggest that minirhizotron data should be converted separately for different soil depths to better estimate fine root biomass. 相似文献
12.
13.
Junji Matsumura Yoko Yamasaki Kazuyuki Oda Yoshitake Fujisawa 《Journal of Wood Science》2005,51(4):328-333
Nine trees of Cryptomeria japonica from six elite tree clones with a broad range of heartwood colors were selected. The profiles of pit aspiration percentage (ASP) of earlywood and latewood from pith to bark for green and air-dry conditions were determined to study the relationship between heartwood color and pit aspiration. Confocal laser scanning microscopy (CLSM) observations showed that the ASP of earlywood was low in sapwood and high in heartwood in the green condition. Pit aspiration increased in intermediate wood when compared with sapwood. On the other hand, latewood pits did not aspirate during heartwood formation. Comparing the air-dry condition with the green condition, sapwood pits aspirated during drying in both earlywood and latewood; however, there was no significant difference in pit aspiration of heartwood. There was no significant difference between samples with red and black heartwoods for ASP. The difference in ASP between individual trees was larger than that by heartwood color. The general advantage of CLSM over light microscopy is that serial optical sections along the Z axis can be obtained for any moisture condition, without the need for thin sectioning or embedding. 相似文献
14.
基于叶重的桉树单叶面积估计模型 总被引:5,自引:0,他引:5
叶面积是树木生长模型和树木的生理过程的一个重要参数。根据叶重量估计叶面积。本文以我国南方主要树种桉树为对象,实测了从25株桉树上摘取的455片桉树叶子的重量和面积,分别建立了基于叶鲜重的嫩叶与成熟叶单叶面积预测模型。其中80%的数据用于建模,20%的数据用于模型验证。基于模型拟合效果、误差和残差分布,确定了成熟叶和嫩叶的叶面积模型分别为幂函数和线性方程。经检验,模型精度均达95%以上。建立的模型为估计单叶面积提供了一个简单可靠的方法,并且在桉树的结构-功能模型研究中有应用潜力。 相似文献
15.
Tomoaki Takahashi Kazukiyo Yamamoto Yoshimichi Senda Masashi Tsuzuku 《Journal of Forest Research》2005,10(2):135-142
Recently, it was shown that individual tree heights could be accurately estimated using small-footprint airborne light detection and ranging (LiDAR) remote sensing. Because most of the areas studied previously were limited to flat terrain, we investigated the accuracy of LiDAR-derived individual tree height estimates for different types of topographical features in mountainous forests with a steeper and more complex topography. Several middle-aged (40–50 years old) sugi (Cryptomeria japonica D. Don) plantations are found in the mountainous regions in Japan; hence, we chose 48-year-old sugi plantations to investigate the accuracy of these estimates. The surveyed area was divided into three types of topographical features; steep slope (mean slope ± SD; 37.6° ± 5.8°), gentle slope (15.6° ± 3.7°), and gentle yet rough terrain (16.8° ± 7.8°). Before estimating tree heights, the number of detected trees within each topographical feature was researched. In each of these terrains, the percentage of trees detected correctly was 74%, 86%, and 92%; the average error between LiDAR-derived and field-measured tree heights was 0.227m, –0.473m, and –0.183m; and the accuracy of the LiDAR-derived tree height estimates, given as root mean square error (RMSE), was 0.901m, 0.846m, and 0.576m, respectively. Consequently, the procedure presented in this study could detect most canopy trees and estimate individual tree heights with an accuracy better than 1m, even in a forest with a mean slope angle of approximately 38°; thus, indicating that small-footprint airborne LiDAR will be a useful tool for accurately estimating the heights of individual canopy trees in sugi plantations in mountainous areas. 相似文献
16.
Tomoaki Takahashi Kazukiyo Yamamoto Yoshimichi Senda Masashi Tsuzuku 《Journal of Forest Research》2005,10(4):305-312
This study investigated which predictor variables with respect to crown properties, derived from small-footprint airborne light detection and ranging (LiDAR) data, together with LiDAR-derived tree height, could be useful in regression models to predict individual stem volumes. Comparisons were also made of the sum of predicted stem volumes for LiDAR-detected trees using the best regression model with field-measured total stem volumes for all trees within stands. The study area was a 48-year-old sugi (Cryptomeria japonica D. Don) plantation in mountainous forest. The topographies of the three stands with different stand characteristics analyzed in this study were steep slope (mean slope ± SD; 37.6° ± 5.8°), gentle slope (15.6° ± 3.7°), and gentle yet rough terrain (16.8° ± 7.8°). In the regression analysis, field-measured stem volumes were regressed against each of the six LiDAR-derived predictor variables with respect to crown properties, such as crown area, volume, and form, together with LiDAR-derived tree height. The model with sunny crown mantle volume (SCV) had the smallest standard error of the estimate obtained from the regression model in each stand. The standard errors (m3) were 0.144, 0.171, and 0.181, corresponding to 23.9%, 21.0%, and 20.6% of the average field-measured stem volume for detected trees in each of these stands, respectively. Furthermore, the sum of the individual stem volumes, predicted by regression models with SCV for the detected trees, occupied 83%–91% of field-measured total stem volumes within each stand, although 69%–86% of the total number of trees were correctly detected by a segmentation procedure using LiDAR data. 相似文献
17.
Kyotaro Noguchi Tadashi Sakata Takeo Mizoguchi Masamichi Takahashi 《Journal of Forest Research》2005,10(6):435-441
Fine roots are a key component of forested ecosystems, but available information is still limited. This study examined the
production and mortality of fine roots less than 1 mm in diameter in a Japanese cedar (Cryptomeria japonica D. Don) plantation located on the Kanto Plain in central Japan. We used a minirhizotron technique in combination with soil
coring, and collected data for 1 year (May 2002–May 2003). Fine root production and mortality were determined from changes
in the lengths of individual fine roots on minirhizotron tubes. Both fine root production and mortality rates were greater
in the upper soil than in lower soil levels. Both rates were seasonal, with higher values in summer than in winter; this trend
was more pronounced in upper soil levels. These results suggest that environmental conditions, such as temperature or soil
properties, affect the production and mortality rates of fine roots. Fine root production and mortality occurred simultaneously,
and their rates were similar, which may have led to unclear seasonal changes in fine root standing crop estimates. Soil coring
indicated that the fine root biomass of this stand was about 120 g m−2, of which 40% was from Japanese cedar. The estimated rates of dry matter production and mortality of total fine roots, including
understory plants, were both approximately 300 g m−2 year−1. 相似文献