Diameter At The Breast Height Research Articles

Exploring Genetic Diversity and Variability of Tamarind (Tamarindus indica L.): A Comprehensive Study in the Bilaspur Region of Chhattisgarh, India

The genetic diversity and variability of Tamarindus indica L., a valuable multipurpose tree species, was investigated through a comprehensive study conducted in the Bilaspur region. This research aimed to assess the morphological variations and growth responses of T. indica under contrasting environments, specifically agroforestry and natural forest systems. The study employed a rigorous scientific approach, encompassing field surveys, statistical analyses, and morphological assessments. The results indicated pronounced morphological differences between T. indica trees in the agroforestry and natural forest systems. T. indica trees in the natural forest exhibited significantly greater average height and diameter at the breast height (DBH) compared to those in agroforestry settings, highlighting the influence of the environment on growth parameters. Here, the crown diameter displayed homogeneity across both environments, suggesting a potential level of adaptability in this trait. The findings show the importance of considering environmental conditions when assessing the growth and development of T. indica, providing valuable insights for both scientific research and practical applications in agroforestry and conservation efforts.

Simultaneous Models for the Estimation of Main Forest Parameters Based on Airborne LiDAR Data

This study aimed to develop simultaneous models with universal applicability for the estimation of the main factors of forest stands based on airborne LiDAR data and to provide a reference for standardizing the approach and evaluation indices of main forest factor modeling. Using airborne LiDAR and field survey data from 190 sample plots in spruce (Picea spp.), fir (Abies spp.), and spruce–fir mixed forests in Northeast China, the simultaneous models for estimating the main factors of forest stands were developed. To develop the models, the relationships between mean tree height, stand basal area, stand volume, and the main metrics of the LiDAR data and the correlations between eight quantitative factors of forest stands were considered, and the error-in-variable simultaneous equations approach was employed to fit the models. The results showed that the mean prediction errors (MPEs) of eight forest stand factors estimated by the simultaneous models were mostly within 5%, and only the MPE of the number of trees per hectare exceeded 5%. The mean percentage standard errors (MPSEs) of the estimates, including the mean diameter at the breast height (DBH), mean tree height, and mean dominant tree height, were within 15%; the MPSEs of the estimates of the stand basal area, volume, biomass, and carbon stock per hectare were within 25%; and only the MPSE of the estimated number of trees per hectare exceeded 30%. The coefficients of determination (R2) of the core prediction models for the volume, biomass, and carbon storage were all greater than 0.7. It can be concluded that estimating the main factors of forest stands based on the combination of LiDAR and field survey data is technically feasible, and the simultaneous models developed in this study for the estimation of the eight main stand factors of spruce–fir forests can meet the precision requirements of forest resource inventory, except for the number of trees, indicating that the models can be applied in practice.

Accuracy of two LiDAR-based augmented reality apps in breast height diameter measurement

Accurate measurement of the diameter at the breast height (DBH) is essential in forestry-related science and practice, but its measurement is currently done by labor-intensive tools such as calipers or devices designed to measure the girth. With the development in light detection and ranging (LiDAR) and augmented reality (AR) technologies, and their integration in low-cost mobile platforms, affordable proximal measurement applications were released on the market. This study examines the accuracy in DBH measurement of Arboreal Forest (hereafter DA) and Measure (hereafter DM) apps, by taking as a reference the measurements done by an accurate forestry caliper (hereafter DC). A number of 615 trees were considered, of which 395 were broadleaved (DBH between 10 and 73 cm, averaging 39.73 ± 9.91 cm) and 220 were coniferous (DBH between 25 and 89 cm, averaging 52.47 ± 12.81 cm), and measurements were taken under sunny, cloudy and rainy weather. Comparison was done in terms of agreement (Bland and Altman's method), dependence (least square simple ordinary and regression through origin), correlation (Spearman's, Pearson's and Kendall's tests), and difference (mean absolute error - MAE, root mean squared error - RMSE, and bias - BIAS). Besides a close-to-perfect fit, strong association in data, and a good degree of agreement, the results indicated the presence of centimeter-level differences when comparing DM against DC (MAE = 0.715 cm, RMSE = 0.879 cm, BIAS = 0.333 cm) and DA against DC (MAE = 0.953 cm, RMSE = 1.246 cm, BIAS = -0.108 cm). When comparing DA against DM the differences were slightly higher (MAE = 1.175 cm, RMSE = 1.531 cm, BIAS = –0.446 cm). The magnitude in differences found is rather caused by the application used and not by the environmental conditions. Further studies may consider larger data samples to provide better estimates as well as checking the limits in measurement capabilities of these apps.

Responses of the Crown Shape of Larix kaempferi Plantations to Site Index in Subtropical Areas of China

This study addresses how site index may affect crown shape by developing a crown shape regression model for the planted L. kaempferi at high altitudes in the subtropical climate of China. A total of 9241 branches from 78 trees, including 39 dominant trees and 39 intermediate trees, were measured in Hubei Province, southern China. The branch characteristics, including branch length, branch angle, and branch chord length of all living branches, were measured by felling trees. The models that showed good performance in crown shape modeling were used and compared in the present study. The goodness of fit statistics and stability of parameter estimation of the modified Kozak equation were better than those of the segmented polynomial equation. A nonlinear mixed-effect crown shape model was developed based on the modified Kozak equation. In addition to the tree level variables of diameter at the breast height (DBH), crown ratio (CR), and tree height-to-DBH ratio, an attempt was made to incorporate the site index into the crown shape model for the planted L. kaempferi. However, the site index was not a significant variable in the crown shape model. The purpose of our study was to lay the foundation for further study of the growth of the trees and the effects of crown morphology on stem growth in the future.

Nesting-tree preferences of the black woodpecker—the biggest cavity excavator in a conifer-dominated forests in Poland

The black woodpecker Dryocopus martius is an ecologically disproportionately important forest species owing to its abundance. Its large cavities provide breeding sites and shelter for many species—large birds, mammals, and social insects. I evaluated the nest tree preferences of black woodpeckers in the Augustów Forest, northeast Poland. Approximately 400 black woodpecker cavities were observed. The Scots pine, Pinus sylvestris, was the most commonly selected tree species, accounting for 90%. The cavity trees were 55–225 years old. All trees younger than 90 years were broadleaved tree species. The trees used to excavate the cavities had a larger diameter at the breast height (DBH) than the average of the stand. The trees selected by black woodpeckers were significantly shorter than the average height of the stands. Over 60% of the cavities were excavated 10–16 m above ground level. I found that the DBH and the first branch height were critical factors affecting the cavity entrance height. In pine-dominated forests, black woodpeckers preferred dead trees. Approximately 44% of new cavities were excavated from dead trees. Leaving dead or dying large trees in commercial forests benefits black woodpeckers and large secondary cavity nesters that depend on it and promotes biodiversity conservation. Birds excavate new cavities at a high rate yearly, in contrast with beech-dominated forests.

A novel geometric feature-based wood-leaf separation method for large and crown-heavy tropical trees using handheld laser scanning point cloud

ABSTRACT As the prerequisite of non-destructively measuring structural parameters and leaf distribution, wood-leaf separation plays an essential role in forest inventories. However, fewer studies focus on the separation and measurement of large tropical trees with heavy crowns and complex branch structures. This study proposed a novel method to automatically separate the leaf and wood points of large tropical trees based on geometric features. Instead of identifying all wood points using the same rules, we used different methods to separate small and large wood components, respectively. The identification of small wood components was implemented mainly by the differences in point density and linear distribution pattern between leaf and wood points, while the identification of large wood components was implemented through the comprehensive analysis of verticality, linearity, anisotropy, as well as point density. To improve the separation accuracy and implementation effectiveness, the segment-wise and point-wise methods were combined in this study. The robustness and generalization of the proposed method were tested using two datasets, i.e. twenty large tropical trees with heavy crowns and twenty-four general tropical trees without heavy crowns. The separation results verified that the proposed method could achieve good separation of wood and leaf points of large crown-heavy tropical trees with the accuracy of up to 91.5%. The highest separation accuracy of general tropical trees was about 95.03%. The examination of the tropical trees without heavy crowns demonstrated that the proposed method has promising robustness and generalization ability. In addition, to fill the gap in the large tropical tree point clouds, an open-source dataset library was built for the wood-leaf separation research, including manually labelled 20 large crown-heavy tropical trees with different types of branch structures and basic structural parameters of each tree (tree height, crown spread, and diameter at the breast height (DBH)).

Stronger wind, smaller tree: Testing tree growth plasticity through a modeling approach.

Plants exhibit plasticity in response to various external conditions, characterized by changes in physiological and morphological features. Although being non-negligible, compared to the other environmental factors, the effect of wind on plant growth is less extensively studied, either experimentally or computationally. This study aims to propose a modeling approach that can simulate the impact of wind on plant growth, which brings a biomechanical feedback to growth and biomass distribution into a functional-structural plant model (FSPM). Tree reaction to the wind is simulated based on the hypothesis that plants tend to fit in the environment best. This is interpreted as an optimization problem of finding the best growth-regulation sink parameter giving the maximal plant fitness (usually seed weight, but expressed as plant biomass and size). To test this hypothesis in silico, a functional-structural plant model, which simulates both the primary and secondary growth of stems, is coupled with a biomechanical model which computes forces, moments of forces, and breakage location in stems caused by both wind and self-weight increment during plant growth. The Non-dominated Sorting Genetic Algorithm II (NSGA-II) is adopted to maximize the multi-objective function (stem biomass and tree height) by determining the key parameter value controlling the biomass allocation to the secondary growth. The digital trees show considerable phenotypic plasticity under different wind speeds, whose behavior, as an emergent property, is in accordance with experimental results from works of literature: the height and leaf area of individual trees decreased with wind speed, and the diameter at the breast height (DBH) increased at low-speed wind but declined at higher-speed wind. Stronger wind results in a smaller tree. Such response of trees to the wind is realistically simulated, giving a deeper understanding of tree behavior. The result shows that the challenging task of modeling plant plasticity may be solved by optimizing the plant fitness function. Adding a biomechanical model enriches FSPMs and opens a wider application of plant models.

Modeling Primary Branch Diameter and Length for Planted Pinus koraiensis by Incorporating Neighbor Competition in Northeast China

Korean pine (Pinus koraiensis Sieb. et Zucc.) is the most important forest vegetation in northeast China. The timber quality of this tree species is largely driven by branch growth and distribution within the crown. Thus, developing branch diameter and length models, especially those that include competition indices, is essential. A total of 48 Korean pine trees were selected to conduct destructive measurements of branch characteristics. This was carried out on all live branches, and a branch diameter and length model was developed. Various indices, including the absolute depth into the branch base (DINC) from tree tip, were used. The equation with the largest Radj2 and smallest root mean square error (RMSE) values was selected as the best model. Each parameter from the best model was reparameterized to the tree variables and competition indices. Finally, the branch diameter model that included diameter at the breast height (DBH), tree height (HT), and the crown length index (CLI), and the branch length model that included DBH and HT exhibited the best performance. The Radj2 and RMSE values were 0.42 and 4 mm, respectively, for the branch diameter model, and 0.77 and 63 cm, respectively, for the branch length model. Branch diameter and length increased as DBH increased and decreased as HT increased. Furthermore, branch diameter decreased as the CLI increased.

Spatial distribution of tree species composition and carbon stock in Tozi tropical dry forest, Sinnar State, Sudan

Abstract. Yasin EHE, Mulyana B. 2022. Spatial distribution of tree species composition and carbon stock in Tozi tropical dry forest, Sinnar State, Sudan. Biodiversitas 23: 2359-2368. Dryland forest ecosystem in Sudan plays an important role, either ecologically or economically, for the community around the forest areas. However, land-use change, illegal logging and grazing have caused dryland forests in the country to degrade. The research aimed to investigate the species composition and carbon stock in a Tozi tropical dry forest (TTDF), a typical dryland forest ecosystem in Sinnar state, Sudan. A total of 306 circular sample plots (1000 m2 for each) were established using a systematic sampling grid method. The distance between plots was 400 m and between survey lines 500 m. In each plot, all living trees were identified and counted, and their diameter at the breast height (DBH) was recorded. Research findings showed that there were 2,339 individual trees representing four species (Acacia seyal, Balanites aegyptiaca, Acacia senegal and Acacia mellifera) that belong to two families. The B. aegyptiaca and A. seyal were the dominant species widely distributed in the TTDF. The average tree density was 175 trees/ha and the Shannon-Weiner index for trees diversity was 0.264. For the seedlings stage, A. mellifera showed a high value of frequency and density, followed by B. aegyptiaca and A. seyal. The structure of seedlings, saplings, and adults trees formed a reverse J-shape in which the density of seedlings was the highest and followed by saplings and adult trees. Carbon stock of A. seyal, B. aegyptiaca, A. senegal, and A. mellifera were 990.95, 2602.78, 1085.82, and 249.20 kg C/ha, respectively. Spatial analysis showed that sites composed of three species resulted in the highest above ground carbon stock compared to single species, two species, and four species compositions.

Fuelwood Harvest and No Harvest Effects on Forest Composition, Structure, and Diversity of Arasbaran Forests—A Case Study

The impact of fuelwood harvesting on forest structure and composition is not clear, especially on the understudied and scarce Arasbaran forests in Iran. This research compared woody species density, species diversity, forest composition, and regeneration status in areas of continuous and ceased fuelwood harvesting in Arasbaran forests. We expected fuelwood harvesting to decrease stem density, species diversity, tree size (diameter at the breast height (DBH) and height), and shift composition away from preferred fuelwood species. We measured woody species size and frequency and identified species in three fuelwood harvest and three no harvest sites, with six sample plots (100 m × 50 m) per site. Results tended to show differences in composition, diversity, woody species height, and density. Carpinus orientalis, a preferred fuelwood species, tended to be more dominant in no harvest (importance values index (IVI) = 173.4) than harvest areas (IVI = 4.4). The diversity or richness of woody species tended to be higher in harvest (20 ± 1 species per ha) than in no harvest (14 ± 2 species per ha) areas, and other measures of diversity supported this trend as well. Harvest areas tended to also be characterized by shorter tree height and lower density of trees, a higher density of regeneration, and fewer small pole-sized trees than no harvest areas. Ongoing fuelwood harvests may further shift composition and structure away from no harvest area, compromising future fuelwood availability, but further detailed research is needed. Close to nature practices may be useful in sustaining fuelwood harvest areas and diversifying areas where fuelwood harvesting has ceased.

Allometric equation for aboveground biomass estimation of Galiniera saxifraga (Hochst.) Bridson in Gesha-Sayilem forest, southwestern Ethiopia

Abstract. Bareke T, Addi A. 2021. Allometric equation for aboveground biomass estimation of Galiniera saxifraga (Hochst.) Bridson in Gesha-Sayilem forest, southwestern Ethiopia. Asian J For 5: 76-82. There is limited information about the precise quantification of Aboveground Biomass (AGB) of species-specific allometric equations for shrubs and small trees. Thirty Galiniera saxifraga plants were selected to develop species-specific allometric biomass equations. Biometric parameters, including the diameter at the Breast Height (DBH), height and crown area were predictive variables that were measured for each individual plant. AGB was measured through a destructive method. The AGB was correlated to biometric variables using regression analysis. The species-specific allometric models, with DBH and crown area as predictors (DBH-crown area models), accounted for 90% of the variation in the AGB of G. saxifraga. The DBH-crown area model was adequate for predicting the AGB for G. saxifraga with the adjusted R2 value 0.9 and AIC values was 47.37. The specific allometric equation developed for the Gesha-Sayilem Afromontane forest can be used in similar moist forests in Ethiopia to implement Reduced Emission from Deforestation and Degradation (REDD+) activities to benefit the local communities from carbon trade.

Estimation of Biomass Increase and CUE at a Young Temperate Scots Pine Stand Concerning Drought Occurrence by Combining Eddy Covariance and Biometric Methods

The accurate estimation of an increase in forest stand biomass has remained a challenge. Traditionally, in situ measurements are done by inventorying a number of trees and their biometric parameters such as diameter at the breast height (DBH) and height; sometimes these are complemented by carbon (C) content studies. Here we present the estimation of net primary productivity (NPP) over a two years period (2019–2020) at a 25-year-old Scots pine stand. Research was based on allometric equations made by direct biomass analysis (tree extraction) and carbon content estimations in individual components of sampled trees, combined with a series of stem diameter increments recorded by a network of band dendrometers. Site-specific allometric equations were obtained using two different approaches: using the whole tree biomass vs DBH (M1), and total dry biomass-derived as a sum of the results from individual tree components’ biomass vs DBH (M2). Moreover, equations for similar forest stands from the literature were used for comparison. Gross primary productivity (GPP) estimated from the eddy-covariance measurements allowed the calculation of carbon use efficiency (CUE = NPP/GPP). The two investigated years differed in terms of the sum and patterns of precipitation distribution, with a moderately dry year of 2019 that followed the extremely dry 2018, and the relatively average year of 2020. As expected, a higher increase in biomass was recorded in 2020 compared to 2019, as determined by both allometric equations based on in situ and literature data. For the former approach, annual NPP estimates reached ca. 2.0–2.1 t C ha−1 in 2019 and 2.6–2.7 t C ha−1 in 2020 depending on the “in situ equations” (M1-M2) used, while literature-derived equations for the same site resulted in NPP values ca. 20–30% lower. CUE was higher in 2020, which resulted from a higher NPP total than in 2019, with lower summer and spring GPP in 2020. However, the CUE values were lower than those reported in the literature for comparable temperate forest stands. A thorough analysis of the low CUE value would require a full interpretation of interrelated physiological responses to extreme conditions.

Review of studies on motor-manual felling productivity in eucalypt stands

AbstractGlobally, about 20 million ha of land area is occupied by plantations of Eucalyptus. Motor-manual tree harvest-ing techniques (using chainsaws) are still applied in eucalypt plantations, especially in difficult terrains or for large- sized trees where mechanised felling may not be an effective and safe possible option to apply. There is little information available on motor-manual felling in eucalypt stands. This article reviewed available literature on the productivity of motor-manual felling. The results were classified into four regions, including Africa, Asia/Oceania, America and Europe. Results of international studies indicate that the main factors impacting the productivity of motor-manual felling include diameter at the breast height (DBH), travelling distance to trees, understory density and terrain slope. Operator experience also plays a key role in felling operations. The range of reported productivity varied from 0.6 m3/PMH0 to 48.9 m3/PMH0 in different regions. This article provides key recommendations on improving motor-manual felling productivity, which can provide a guide for sustainable harvesting planning purposes. 

The Growth Pattern of <i>Chamaecyparis obtuse</i> Stand along Longevity in Gyeongnam Province, South Korea

Tree growth is affected by environmental factors, climate condition and tree age. The objective of this study was to evaluate the growth patterns of Chamaecyparis obtusa (C. obtusa) stand in the Gyeongnam province. Data was collected from two cities and one county by using sample quadrats of 20 * 20 m. A total of 11 quadrats were used to collect tree height, diameter at the breast height (DBH), annual growth rings and soil data. The data analysis of soil moisture content, pH, organic matter (%), EC (cmol + /kg of soil), and available phosphorous was conducted. Growth ring was analyzed by using computer based software and the ages of the trees were identified. Average growth of height and DBH was computed from the surveyed data and annual growth of each tree was assessed by computer based reading of annual growth rings. The results of the study revealed that tree growth showed a reducing trend along the longevity. It was identified that soil pH, age, variation in annual average temperature, and altitude were the main factors related with growth of C. obtusa trees along the life of the stand.

Interspecific variations in tree allometry and functional traits in subtropical plantations in southern China.

Mechanical stability against buckling and water transport resistance through xylem vary with increasing tree height. To explore interspecific allometry based on morphological and physiological traits can play a crucial role in revealing their ecological adaptation. Four architectural traits (tree height, diameter at the breast height (DBH), crown width and crown depth) and seven functional traits (specific leaf area (SLA), leaf total carbon concentration (TC), midday leaf water potential, leaf δ13C and δ18O, wood density and xylem water transport efficiency) were measured in Schima superba, Acacia auriculiformis and Eucalyptus citriodora plantations in the subtropical region of China. The mechanical stability declined in the order of S. superba > A. auriculiformis > E. citriodora. Taller species at a given DBH had slender stems and narrower crowns. Smaller leaf δ18O and more efficient xylem water transport were observed in two taller tree species, A. auriculiformis and E. citriodora. Smaller SLA, higher leaf TC and larger leaf area indicated more carbon allocation to leaves of S. superba. The variations in architectural and functional traits with tree allometry among tree species may provide a more complete understanding of species-specific growth strategies in this subtropical region.

BEECH TREE DENSITY ESTIMATION USING SENTINEL-2 DATA (CASE STUDY: KHYROUD FOREST)

Abstract. Obtaining information about forest attributes is essential for planning, monitoring, and management of forests. Due to the time and cost consuming of Tree Density (TD) using field measurements especially in the vast and remote areas, remote sensing techniques have gained more attention in scientific community. Khyroud forest, a part of Hyrcanian forest of Iran, with a high species biodiversity and growing volume stock plays an important role in carbon storage. The aim of this study was to assess the capability of Sentinel-2 data for estimating the tree density in the Khyroud forest. 65 square sample plots with an area of 2025 m2 were measured. In each sample plot, trees with diameter at the breast height (DBH) higher than 7.5-cm were recorded. The quality of Sentinel-2 data in terms of geometric correction and cloud effect were investigated. Different processing approaches such as vegetation indices and Tasseled Cap transformation on spectral bands in combination with an empirical approach were implemented. Also, some of biophysical variables were computed. To assess the model performance, the data were randomly divided into parts, 70% of sample plots were used for modelling and 30% for validation. The results showed that the SVR algorithm (linear kernel) with a relative RMSE of 23.09% and a R2 of 0.526 gained the highest performance for tree density estimation.

Modeling Tree Mortality for Eucalyptus camaldulensis (Dehnh) Stands in Afaka Forest Reserve, Kaduna-Nigeria

This research was conducted to investigate mortality using logistic regression (Models) for River red-gum (Eucalyptud camaldulensis Dehnh) in Afaka Forest Reserve, Kaduna, Nigeria. Stratified random sampling and proportional sampling allocation were used in selecting plots and individual trees for measurements. Data on live and dead trees were recorded, variables measured are diameter, total tree heights, spacing and age of the stands within the plots. Diameter at the breast height (DBH) was measured using diameter tape while Haga Altimeter was used in taking the total height of the sampled stands. The Data collected were divided into four portions. Three portions (75%) for model calibration adopting logistic regression model, 25% were used for model validation of logistic model generated. Chi square test of goodness-of-fit, Negelkerke R2, Cox and snell R2 values were used for model evaluation. The positive regression coefficients (16.737, 49.266 and 1.992) showed by Dbh, Height and age (as independent variables) indicated positive future mortality effects on the stands; as the trees ages and increases in size and height, the chances of mortality will increase. At the present age and sizes of the stands the fitted model shows no significant relationship between the current age, height and size of the stands, as such the notion held by the management of the plantation that Eucalyptus cannot grow for many years and in large sizes is not true. There is therefore, need for periodic re-measurement of the stands to evaluate future effect of the variables (Age, Dbh and height) on mortality.

Forest protection policy: Lesson learned from Arasbaran biosphere reserve in Northwest Iran

Protection policy of forests is an important strategy to improve quantitative and qualitative characteristics of forest stands and their services. In addition, the concurrence of global climate change and the decline in natural resources has led scientists to focus on the sustainable development of forest land use. Unfortunately, the allocation of different uses to land has led to urbanization, industrialization, and environmental risks. Forty-five years of forest protection policy in Arasbaran Biosphere Reserve, Northwest of Iran, has created a venue to assess the effectiveness of forest conservation-based management. For this purpose, by using random systematic sampling methodology, 132 samples (66 sample plots in the protected area and 66 sample plots in the unprotected area) with a total area of 300 square meters were collected in the northern slopes. Quantitative and qualitative characteristics of woody species in each plot, as well as regeneration frequency, were recorded. Topsoil samples were also collected, and some soil characteristics were measured. Biodiversity indices were calculated for tree species using the inventory collected data. Results revealed that parameters such as diameter at the breast height (DBH), basal area (BA), proportions of seed-origin stems, total height, crown’s height, and canopy area were significantly higher in the protected area (p < 0.05). In addition, the status of soil parameters in the protected area was better. In addition, tree regeneration (number per hectare) is higher in the unprotected area in comparison to the protected area. In conclusion, the forest protection policy in Arasbaran biosphere was evaluated 'successful' in terms of amending some forest characteristics indicative of the stand sustainability in forest land via reduction of and/or compensation for anthropogenic damages to the environment.

Estimating individual- and stand-level stem CO2 efflux in a subalpine forest: assessment of different extrapolation methods

Accurate evaluation of the carbon release by stems is an important objective of many forest carbon cycling studies. However, few studies have assessed the applicability of different extrapolation methods of stem CO2 efflux. Therefore, a reliable estimation method that considers both temporal and vertical variations is required. To overcome this problem, we conducted a field experiment to measure the stem CO2 efflux rate of Abies fabri in subalpine forests, and evaluated the effect of three extrapolation methods (area-based estimation, volume-based estimation and integral method) on accurate estimation of stem respiration at the individual and stand levels. First, we calculated the stem carbon loss at the individual level using the three extrapolation methods, and discovered that the diameter at the breast height (DBH) played a major role in determining the magnitudes of stem respiration. Second, we summarized the relationship between the stem CO2 efflux rate (Es) and the DBH from previous studies. The Es for small diameter stems tended to increase with height, but remained constant in trees with large DBH, implying a role of DBH threshold in determination of the Es effect. Our calculations from three estimation methods supported the hypothesis that a threshold accounted for the different vertical variations in Es. Specifically, the vertical variation of Es primarily presented as two categories: Es decreased with the stem height for small diameters (DBH 60 cm). Based on these trends, we suggest a two-part approach to scale the individual tree stem CO2 efflux, in which a volume-based scaling method is recommended for trees with small DBH (0–30 or 40 cm) and an area-based estimation is suitable for stems with large DBH (> 30 or 40 cm). Using this approach, the annual amount of stem carbon release for an immature forest and a mature forest were estimated as 1.80 and 4.81 t C ha−1 year−1, respectively.

Edge Effects on Tree Growth and Species Diversity in Forests of Different Types and Ages

Edge to interior gradients in forest ecosystems can influence the species composition and community structure as a result of variations in micro-environment. In this study, the edge effects on stand productivity and plant species diversity were investigated in two adjacent types of forests in central-southern China: Chinese fir adjacent with pine forests and Chinese fir adjacent with broad-leaved forests. A total of 48 sample plots for overstory and 240 sample quadrates for understory in different stand ages were set up. The tree growth parameters were measured in the overstory while the plant species diversity was measured in both overstory and understory of the examined forests. The results showed that DBH (tree diameter at the breast height), tree height and stand volume in overstory increased from the central areas (CA) of forests to the edge areas (EA), and the plant species richness and diversity in understory were greater in EA than in CA. The edge effect was greater in Chinese fir paired with broad-leaved forests than in Chinese fir paired with pine forests. The edge effect decreased in an order as young aged stands > middle aged stands > mature aged stands in the studied forests. The changes in tree growth and species diversity in the edge area compared to the interior were mainly attributed to the alteration of micro-environmental factors such as light density, temperature and moisture. Our results suggest increasing forest productivity and plant species diversity could be achieved by making more edges in the forests.