Determining the Optimal Harvesting Period of Melia dubia by Expression of Cellulose and Lignin Biosynthesis Genes for Improved Pulpwood Quality

This study was conducted to suggest the necessity of regulated stand density control in order to maintain the ratio of height to diameter at breast height (H/D ratio) of Hinoki cypress (Chamaecyparis obtusa) and Japanese cedar (Cryptomeria japonica) in South Korea. A total of 2,000 (1,000 each) Hinoki cypress and Japanese cedar were cut from various regions of South Korea, and their diameter at breast height (DBH), height and clear length were measured. The two species’ regional means of H/D ratio and crown ratio were then computed and compared to find the relationship with tree growth. The result of analyzing the relationship between the H/D ratio and tree growth by DBH class is as follows, 77.0% for small DBH class, 62.5% for medium DBH class, and 45.9% for large DBH class, with overall mean of 61.8%. The annual means of DBH growth were 4.6 mm, 7.4 mm, and 8.2 mm respectively for small, medium, and large DBH classes. As the DBH class went up, the H/D ratio decreased, showing a negative correlation (p < 0.0001) with the tree growth rate. However, the crown ratio showed a significant correlation with tree growth. Japanese cedar’s H/D ratios by DBH class were 100.5% for small, 74.9% for medium, and 53.6% for large, while its mean annual DBH growth were 5.1 mm, 7.6 mm, and 10.0 mm, from small to large DBH class respectively. Similar to that of Hinoki cypress, Japanese cedar’s H/D ratio showed a negative correlation with the growth rate (p < 0.0001), but no significant relationship could be established between the crown ratio and the tree growth. In both arboreal species, the correlation between the H/D ratio and growth rate is negative, and no significant correlation could be formulated between crown ratio and tree growth. In conclusion, both tree species tended to have a higher H/D ratio and a lower growth rate in small DBH class, while H/D ratio decreased and growth rate increased As DBH class got larger.

This is the second part of a large research initiative aimed at characterizing Changbai larch (Larix olgensis Henry) for veneer and high-valued product potential. The objective of this work was to investigate the effect of the tree growth characteristics, particularly diameter at breast height (DBH) and radial growth from pith (or peeler core) to bark on clear wood and veneer properties. A population of 36 trees was chosen and classified into three DBH classes, namely 20, 25, and 30 cm, and crosscut into six segments each along the vertical stem. With the entire veneer ribbon peeled from the pith to bark for each segment, the effect of sapwood and heartwood on wood properties was revealed. The tree DBH and height were moderately and positively correlated. The tree DBH significantly affected properties of both clear wood and veneer in a similar pattern. For the larch veneer population, veneer mean ultrasonic propagation time (UPT) and density decreased but veneer mean dynamic modulus of elasticity (MOE) increased from the heartwood to sapwood or from the pith to bark. Among the three DBH classes, the 25 cm DBH yielded the highest mean veneer density and MOE, followed by the 20 cm DBH and 30 cm DBH. This was found to be caused by the radial evolution of veneer properties from the pith to bark in combination with the variation of veneer yield and stem position.

The plant biomass is an important ecosystem function of forests and plays a fundamental role in the material cycle and energy flow. The diameter at breast height (DBH) and height of plants with DBH ≥1 cm were surveyed in tropical cloud forests in Jianfengling Mt., Bawangling Mt., and Limushan Mt. with forest aboveground biomass (AGB) being calculated with an allometric model. We assessed variations in AGB across different plot sizes, DBH classes, and plant height classes in the three tropical cloud forests. The results showed that AGB in the three tropical cloud forests consistently changed across plot sizes, with the AGB being significantly higher in Jianfengling Mt. and Limushan Mt. than the Bawangling Mt., due to the influences of precipitation and air temperature. AGB of Jianfengling Mt., Bawangling Mt., and Limushan Mt. was mainly distributed in trees with DBH ≥ 30 cm, accounting for 33.0%, 32.1%, and 52.8%, respectively. For the patterns of AGB across height classes, AGB was mainly distributed in plants with height ≥7 m in Jianfengling Mt. and Bawangling Mt. accounting for 79.9% and 70.1% of the total AGB. The ABG in Limushan Mt. was mainly distributed in plants with a height ≥9 m, accounting for 87.7% of the total AGB. Changes in AGB across the three tropical cloud forests were consistent at different DBH and height classes with an AGB being mainly distributed in large trees.KeywordsTropical cloud forestAboveground biomassDBH classHeight class

BackgroundThe purpose of this study was to predict culm height development and to evaluate biomass accumulation and carbon storage in the initial growth stage of moso bamboos (Phyllostachys pubescens). A total of 30 bamboos were sampled based on their diameter at breast height (DBH). I predicted the culm heights daily based on the Richards growth function for these bamboo samples. After they reached their maximum heights, the biomass and carbon storage were determined.ResultsThe results showed that the Richards function accurately simulated the height growth of bamboos and that the growth potential of culm heights increased with increasing DBH classes. In contrast, the time when the maximum growth rate occurred (tmax) appeared to not be influenced by DBH classes and was close to 20 days for all DBH classes. The culms arrived at their maximum heights in about 40 days regardless of DBH class. In addition, astonishing biomass accumulation and carbon storage was found during this period, and the aboveground biomass and carbon storage were predicted to be 3.44–17.33 and 1.58–8.04 kg culm−1 for moso bamboos, respectively. The allometric model was used to predict the relationships between DBH and aboveground biomass in this stage.ConclusionsI compared the biomass accumulation between this stage and the entire yield period (5 years) and found that the bamboos accumulated three-fourths of their biomass for the entire yield period in only 40 days. This revealed that biomass accumulation and carbon storage mainly occurs in the initial growth stage for individual moso bamboos.

In view of the important role played by roots against shallow landslides, root tensile force was evaluated for two widespread temperate tree species within the Caspian Hyrcanian Ecoregion, i.e., Fagus orientalis L. and Carpinus betulus L. Fine roots (0.02 to 7.99 mm) were collected from five trees of each species at three different elevations (400, 950, and 1350 m a.s.l.), across three diameter at breast height (DBH) classes (small = 7.5–32.5 cm, medium = 32.6–57.5 cm, and large =57.6–82.5 cm), and at two slope positions relative to the tree stem (up- and down-slope). In the laboratory, maximum tensile force (N) required to break the root was determined for 2016 roots (56 roots per each of two species x three sites x three DBH classes x two slope positions). ANCOVA was used to test the effects of slope position, DBH, and study site on root tensile force. To obtain the power-law regression coefficients, a nonlinear least square method was used. We found that: 1) root tensile force strongly depends on root size, 2) F. orientalis roots are stronger than C. betulus ones in the large DBH class, although they are weaker in the medium and small DBH classes, 3) root mechanical resistance is higher upslope than downslope, 4) roots of the trees with larger DBH were the most resistant roots in tension in compare with roots of the medium or small DBH classes, and 5) the root tensile force for both species is notably different from one site to another site. Overall, our findings provide a fundamental contribution to the quantification of the protective effects of forests in the temperate region.

抚育间伐对蒙古栎次生林生长的影响

Background: Dracaena cinnabari is a monocot species that does not form annual tree rings; thus, its age can only be estimated. This species is threatened by low natural regeneration, with an evident absence of younger individuals most likely caused by overgrazing; therefore, knowing trees’ ages is important for possible conservation strategies; Methods: Data collection was conducted on the Firmihin Plateau on Socotra Island (Yemen) in 2021, and the diameter at breast height (DBH) of 1077 individuals was measured, the same as those established on monitoring plots 10 years before the current measurement. The 10-year radial stem increment and DBH obtained in 2011 served as a basis for the linear model from which the equations for the age calculation were derived. Results and Conclusions: A direct model of age estimation for D. cinnabari was developed. According to the fit model, the age in the first (10.1–15 cm) DBH class was estimated to be 111 years, while that in the last DBH class (90.1–95 cm) was estimated to be 672 years. The results revealed that the previously used indirect methods for D. cinnabari age estimation were accurate.

Increasing anthropogenic nitrogen (N) deposition from agricultural and industrial use, legume cultivation, combustion of fossil fuels, and biomass burning has until recently been a problem of industrialized countries in Europe, North America and East Asia. Consequently, most studies so far investigating the response of natural ecosystems to this threat originate from these temperate regions. With the ongoing development of economically-emerging countries, the most substantial increase in anthropogenic N deposition will occur in tropical regions of Asia and Latin America but knowledge about how tropical ecosystems will respond to this upcoming threat is greatly lacking. As net primary production (NPP) in many terrestrial ecosystems is N-limited and tropical rain forests generating one-third of global terrestrial NPP exert a considerable influence on the world s carbon (C) budget, human alterations of the N constraints on possibly N-limited NPP of some tropical ecosystems might have a drastic influence on the global C cycle. The present thesis assessed how N fertilization affected different aspects of NPP in a tropical lower montane rain forest in western Panama with the objectives 1) to identify differences among components of above-ground net primary production (ANPP; stem growth, litterfall), 2) to determine the response of fine root productivity and turnover, and 3) to estimate the potential of the vegetation to serve as a sink for N and C. An N fertilization experiment was set up with four control and N-fertilized replicate plots of 40 × 40 m, the latter receiving 125 kg urea-N ha-1 year-1 in four applications per year. Stem diameter growth was analyzed by diameter at breast height (DBH) classes and also for the three most abundant species (Oreomunnea mexicana, Eschweilera panamensis, Vochysia guatemalensis). Litterfall was collected every other week from four litter traps per plot. In three soil depths (organic layer, 0-10 cm and 10-20 cm mineral soil), fine root production and turnover were measured by sequential coring and fine root biomass allocation by the ingrowth core approach. Analyses of the N and C content of different tissues (fresh leaves, wood and bark, leaf litter, and fine roots) were used to estimate N and C sequestration by NPP. The responses of stem growth and litter production to N fertilization were highly variable as well within these components (DBH classes, species; litter categories) as in time, since the different ANPP components were not uniformly limited by N supply and subject to inter-annual climatic variation. N fertilization led to an increase in ANPP in the first year of the experiment driven by the response of its most important component which is litterfall. Total litterfall and leaf litterfall were higher under N fertilization also for the two years combined. Above-ground woody biomass was unresponsive to N addition as was stem growth of most DBH classes and species, the only exception being E. panamensis 10-30 cm DBH in the first year. The ability of a species to increase its stem growth in response to N addition seemed to depend on the N costs of stem growth expressed as wood C:N ratios. E. panamensis with a low wood C:N ratio was stronger limited by N than O. mexicana and V. guatemalensis with relatively high wood C:N ratios, and hence, a lower N demand for wood C sequestration. Fine root production and turnover were not affected by N fertilization. Fine root biomass allocated to the 10-20 cm mineral soil in the N-fertilized plots increased two-fold compared to the control, probably because the changed vertical distribution of mineral N allows fine roots to forage for other limiting nutrients, e.g. phosphorus, in the mineral soil without being constrained by the low N availability of the unamended mineral soil. N addition increased C sequestration in the first year. This increase can be attributed to an increased total NPP as tissue C concentrations did not change under N fertilization. Also the increase in C and N return to the forest floor with leaf litter is attributable to the increased leaf litter production. 16.5% of the added N were returned by this pathway. Leaf litter and fine root production were the most important C and N sinks. C and N sink strength of the vegetation is dependent on whether an increase in NPP will occur and also on the C:N stoichiometry of the responsive NPP component(s).

Stem form variations in the natural stands of major commercial softwoods in eastern Canada

Pinus roxburghii is dominant timber species in Nepal. However, there is not any model showing correlation of Diameter at breast height (DBH) with Volume and Carbon Stock. Therefore, this study was objectively conducted to show the correlation of diameter with volume and carbon stock. Gaumati community forest was selected as study site for this research. Total 214 sample trees were taken into account for the study. DBH classes were categorized into s 0-10, 11-20, 21-30, and 31-40, 41-50, and DBH &gt; 50 cm to represent the most of the diameter classes. Height and DBH were measured using Clinometer and Diameter tape. Four types of models were developed for volume and carbon stock with DBH viz. linear, logarithmic, power, and exponential. The models were tested, out of which the power equation was found to be the most accurate for both carbon and volume calculations. Power volume and carbon stock equations are y = 0.00004 x2.8404 (y=volume, x=DBH) and y = 0.0125x2.8404 (y=carbon stock, x=DBH) respectively. The estimated values of R2, MAD, MSE, RMSE and AIC were 0.9817, 0.178, 0.093, 0.305 and -41.58 respectively for power volume model and these values of R2, MAD, MSE, RMSE and AIC were 0.9817, 21.92, 1379.01, 37.13 and 1194.18 respectively for carbon stock calculation. Study shows that, there is a strong correlation between DBH vs. volume and DBH vs. carbon stock. Thus, the volume equation and carbon stock equation will be useful for forest science to calculate the volume and carbon stock of standing plants.

Competition and facilitation co-regulate the spatial patterns of boreal tree species in Kanas of Xinjiang, northwest China

Understanding the maintenance of diversity and the assembly of communities is a primary concern in community ecology. This study explored the phylogenetic structure of an evergreen broadleaved tree community in Con Dao National Park, Vietnam. The survey, conducted in December 2023, encompassed all tree individuals with a diameter at breast height (DBH) ≥ 2.5 cm within a 4-ha study plot. These individuals were identified by species name, and their DBH was measured. Subsequently, a community phylogenetic tree was constructed using the Phylomatic online platform. The 4-ha study plot was subdivided into there different subplots based on three spatial scales (25 m × 25 m, 50 m × 50 m, and 100 m × 100 m) and all trees were classified into three different DBH classes (2.5 cm ≤ DBH &lt; 10 cm representing small trees; 10 cm ≤ DBH &lt; 20 cm as medium trees; and DBH ≥ 20 cm as large trees). The net relatedness index (NRI) and net nearest taxon index (NTI) were utilized to evaluate the phylogenetic structure and infer ecological processes. Our findings revealed a consistent decrease in both NRI and NTI with increasing spatial scales and tree sizes. These results suggest an overdispersed phylogenetic structure within the community across different spatial scales and tree sizes. Additionally, negative density dependence was found to have a pronounced effect on the phylogenetic structure, with a more significant impact on tree individuals from small and medium DBH classes than large ones. This study underscores the significance of phylogenetic density dependence as a primary mechanism governing species diversity and shaping the community structure of evergreen broadleaved forests in Vietnam.

In this study, a method for estimating the stand diameter at breast height (DBH) classes in a South Korea forest using airborne lidar and field data was proposed. First, a digital surface model (DSM) and digital terrain model (DTM) were generated from the lidar data that have a point density of 4.3 points/m2, then a tree canopy model (TCM) was created by subtracting the DTM from the DSM. The tree height and crown diameter were estimated from the rasterized TCM using local maximum points, minimum points and a circle fitting algorithm. Individual tree heights and crown diameters were converted into DBH using the allometric equations obtained from the field survey data. We calculated the proportion of the total number of individual trees belonging to each DBH class in each stand to determine the stand DBH class according to the standard guidelines. More than 60% of the stand DBH classes were correctly estimated by the proposed method, and their area occupied over 80% of the total forest area. The proposed method generated more accurate results compared to the digital forest type map provided by the government.

A study was conducted in the forest area of Chittagong (South) Forest Division, Chittagong, Bangladesh for developing allometric models to estimate biomass organic carbon stock in the forest vegetation. Allometric models were tested separately for trees (divided into two DBH classes), shrubs, herbs and grasses. Model using basal area alone was found to be the best predictor of biomass organic carbon stock in trees because of high coefficient of determination (r^2 is 0.73697 and 0.87703 for＞ 5 cm to≤15 cm and ＞ 15 cm DBH (diameter at breast height) rang, respectively) and significance of regression (P is 0.000 for each DBH range) coefficients for both DBH range. The other models using height alone; DBH alone; height and DBH together; height, DBH and wood density; with liner and logarithmic relations produced relatively poor coefficient of determination. The allometric models for dominant 20 tree species were also developed separately and equation using basal area produced higher value of determination of coefficient. Allometric model using total biomass alone for shrubs, herbs and grasses produced higher value of determination of coefficient and significance of regression coefficient (r^2 is 0.87948 and 0.87325 for shrubs, herbs and grasses, respectively and P is 0.000 for each). The estimation of biomass organic carbon is a complicated and time consuming research. The allometric models developed in the present study can be utilized for future estimation of organic carbon stock in forest vegetation in Bangladesh as well as other tropical countries of the world.

Modeling height–diameter relationships is an important component in estimating and predicting forest development under different forest management scenarios. In this paper, ten widely used candidate height–diameter models were fitted to tree height and diameter at breast height (DBH) data for Populus euphratica Oliv. within a 100 ha permanent plots at Arghan Village in the lower reaches of the Tarim River, Xinjiang Uyghur Autonomous Region of China. Data from 4781 trees were used and split randomly into two sets: 75 % of the data were used to estimate model parameters (model calibration), and the remaining data (25 %) were reserved for model validation. All model performances were evaluated and compared by means of multiple model performance criteria such as asymptotic t-statistics of model parameters, standardized residuals against predicted height, root mean square error (RMSE), Akaike’s information criterion (AIC), mean prediction error (ME) and mean absolute error (MAE). The estimated parameter a for model (6) was not statistically significant at a level of α = 0.05. RMSE and AIC test result for all models showed that exponential models (1), (2), (3) and (4) performed significantly better than others. All ten models had very small MEs and MAEs. Nearly all models underestimated tree heights except for model (6). Comparing the MEs and MAEs of models, model (1) produced smaller MEs (0.0059) and MAEs (1.3754) than other models. To assess the predictive performance of models, we also calculated MEs by dividing the model validation data set into 10-cm DBH classes. This suggested that all models were likely to create higher mean prediction errors for tree DBH classes >20 cm. However, no clear trend was found among models. Model (6) generated significantly smaller mean prediction errors across all tree DBH classes. Considering all the aforementioned criteria, model (1): $$ {\text{TH}} = 1.3 + {\text{a}}/\left( {1 + {\text{b}} \times {\text{e}}^{{ - {\text{c}} \times {\text{DBH}}}} } \right) $$ and model (6): $$ {\text{TH}} = 1.3 + {\text{DBH}}^{2} /\left( {{\text{a}} + {\text{b}} \times {\text{DBH}} + {\text{c}} \times {\text{DBH}}^{2} } \right) $$ are recommended as suitable models for describing the height–diameter relationship of P. euphratica. The limitations of other models showing poor performance in predicting tree height are discussed. We provide explanations for these shortcomings.