Diameter At Breast Height Classes Research Articles

Woody Species Composition, Stand Structure and Regeneration Status of Londiani Forest in Kenya

Tropical forests provide habitats for diverse flora and fauna, in addition to playing a crucial role in climate regulation. They are being recognized for their roles as nature-based solutions to many sustainable development challenges, as shown by increased political commitment and global promises to reduce the rates of deforestation and boost the restoration of degraded forest ecosystems. Understanding tropical forest dynamics and their conservation status is therefore important. This study analysed the forest stand structure, the tree species composition and the regeneration status of Londiani Forest. In the three blocks of Londiani Forest, which are Kedowa, Chebewor and Londiani, belt transects that were 25 m wide and 1 km long were established. At every 200 m along the transects, 25 m × 25 m quadrats were set up in which an inventory of all the tree species was determined. Diameter tape was used to measure the diameter at breast height (DBH) 1.3 m above the ground. With the use of a Suunto angular clinometer, the tree height was measured. A nested 5 m × 5 m quadrat within the 25 m × 25 m quadrat was used to sample the saplings, while a 1m × 1 m quadrat was used to sample the seedlings. The quantities of seedlings and saplings were used to determine the state of regeneration. The data were entered into Microsoft Excel. The total stem density, species density, basal area, species basal area, relative density and species diversity were determined and extrapolated per hectare. A total of 1308 distinct trees from 34 different species and 24 families were counted. Kedowa recorded the highest (27) species richness, followed by Chebewor (19) and then Londiani (14). There was a statistically significant difference in the species richness among the three forest blocks (p < 0.05). Within the three forest blocks, there were no statistically significant variations in the basal area distribution (p > 0.005) or in the mean DBH (F = 0.560; p = 0.729) or height class distribution (F = 0.821; p = 0.558). There was a statistically significant difference in the stem density (F = 12.22; p = 0.005) and woody species diversity (F = 0.32; p = 0.001) within the three forests blocks. The similarity index ranged from 0.34–0.47. The presence of substantial numbers of seedlings and saplings in all forest blocks was an indication that there was regeneration.

Biodiversity and Structural Analysis of Woody Plant Species of Home Gardens in Basona Worana District, North Shoa Zone of Central Ethiopia.

The purpose of this study was to investigate the biodiversity and structure of woody plants of HGs in the Basona Worana district (BWD). For this, six kebeles and 138 HGs from three agroecologies of BWD were selected using various sampling techniques. The plot size used per HG was 400 m2. Diversity and important value indices (IVIs) were computed. For their structural analysis, the diameter at breast height (DBH) and height were also measured for trees and shrubs fulfilling the standards (diameters at breast height (DBH) ≥2.5 cm and height >2 m). Thus, a total of 42 woody species belonging to 37 genera and 26 families were identified. Fabaceae was the most abundant family, followed by Euphorbiaceae. Trees were the dominant habit. The richness in Kola HGs (33) was higher than Dega (14) and Woinadega (19) HGs, with an overall mean richness of 4.14 per HG of BWD. The Shannon, Simpson, and evenness indices for HGs in the district were 1.05, 0.55, and 0.75, respectively, showing their moderate diversity with even distribution. The Sorenson's similarity of HGs between Dega and Woinadega, Kola and Dega, and Kola and Woinadega were 40%, 28%, and 32%, respectively. The multiple site similarities of woody species among three ecological zones (36%) were still <50%, showing no similarity. The overall DBH and height classes' patterns of the woody species individuals abruptly decreased towards their highest classes. Similar DBH and height classes' patterns of woody species individuals were also observed in Kola and Woinadega agroecologies, indicating their selective tree cutting. The mean values of DBH, height, basal, and crown areas of the woody species in the district were ∼14 cm, ∼6 m, ∼29 m2·ha-1, and 5 m2, respectively. Based on IVI, most of the HGs were dominated by Eucalyptus globules (93.35), followed by Eucalyptus camaldulensis (45.04), Rhamnus prinoides (22.4), and Cupressus lusitanica (22.33). Hence, actions should be taken to promote the diversity and managing of HGs' woody species of BWD.

Modelling diameter at breast height distribution of jack pine and black spruce natural stands in eastern Canada

Individual tree diameter at breast height (DBH) distribution is an important information for forest management planning. Forest managers obtain the DBH data either by field measurements or estimations using predictive models. However, probability distribution models are still lacking or need improvement. Therefore, we aimed to construct and fit diameter distribution models that reflect forest structure and composition change. We evaluated gamma, log-normal, and Weibull probability distribution functions (PDFs) for two commercially important tree species, black spruce ( Picea mariana (Mill) B.S.P.) and jack pine ( Pinus banksiana Lamb), grown in natural stands across Ontario, Canada. We modelled the parameters of the distributions as a function of stand-level variables for these species. We used DBH data from 735 permanent sample plots. Our results showed that all three evaluated PDFs reflected observed DBH distribution. We demonstrated that the moment-based recovered parameters could represent the maximum likelihood-estimated parameters precisely, and parameters of the PDFs can be modelled as a function of stand-level dynamic covariates. The models unbiasedly predicted the PDF parameters DBH means and DBH classes. The R2 of the model fit ranged between 0.35 and 0.98 for the predicted parameters and 0.90 and 0.97 for the predicted DBH.

EFFECT OF THINNING ON GROWTH AND WOOD PRODUCTION OF NATURALLY REGENERATED 8-YEAR-OLD ACACIA MANGIUM WILLD. PLANTATION ON ABANDONED MINING AREA, SOUTHERN THAILAND

Thinning is an important practice for promoting growth and maintaining forest plantation for wood production from the remaining trees. In this study, thinning was carried out in a naturally regenerated 8-year-old Acacia mangium plot in the Phangnga Forestry Research Station. Three thinning schemes, with 175 (T1), 300 (T2) and 600 (T3) remaining trees/ha, were compared with the control (no thinning) of 831 trees/ha. The diameter at breast height (DBH) and height (H) of the trees were measured. The differences in growth, current annual increment (CAI), aboveground biomass, and stem volume (V) were analyzed. We observed that the thinning of A. mangium increased the growth rate, with the DBH being clearly affected by thinning. CAIDBH increased significantly, with the DBH class of thinned A. mangium plots also improving after thinning. The stem volume and aboveground biomass of T3 plot was similar to the control plot after thinning. In addition, the number of large saw logs was the highest in T3 plot. The large saw logs can be used for multi-utilization and have a high value. These results suggest that thinning can promote stem growth, and increase the proportion of large saw logs in naturally regenerated A. mangium stands.

Current practices of conducting forest management plans in the Amazon may risk the survival of timber species.

Measurement of the recovery of wood stocks in logging areas in the Amazon helps to understand the efficiency of policies for the use and conservation of native forests. This work evaluated the effects of logging on the dynamics and production of commercial species in the short and medium term in a conservation unit in the state of Rondônia. Structural patterns of the species as a function of mortality and recruitment rates, patterns of average increment in diameter, and estimates of forest production in the short and medium term were analyzed. The study was carried out in an area designated as Annual Production Unit 2 of Forest Management Unit III of Jamari National Forest. In addition to legalized harvesting, there are reports of illegal logging in the area as of 2015. Inventory data from 2011, 2015, and 2018 were used, considering trees of commercial value with a diameter at breast height (DBH) greater than 10cm. Mortality rate, recruitment, periodic annual increment, absolute tree density, basal area, and commercial volume, by species and DBH classes, as well as the similarity of the species regarding the growth pattern. The population structure of species over the years was affected by tree mortality, mainly due to damage caused by illegal logging. Mean increment values varied by species and diameter classes, and six species represented 72% of the total volume of wood stock. It is important to review the criteria for sustainable forest production in the long term. Thus, it is necessary to promote species diversity and improve public authorities' capacity to enforce and of the private sector to comply with legislation. This, in turn, will enable the development of strategies to make the consumption of legal wood more rational.

Age Estimation of Dracaena cinnabari Balf. f. on Socotra Island: A Direct Method to Determine Its Lifespan

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.

Greenwood regeneration status in community forests of Chiti Lamjung Nepal

Forest regeneration is the process by which new tree seedlings become entrenched after forest trees have been harvested or destroyed by fire, insects, or diseases. The process is key to sustainable forestry and can be accomplished through natural regeneration, which occurs when new seedlings or sprouts are produced by trees left on or near the site. The study is to calculate the regeneration status of the tree species in community-managed forests. The sampling points were generated by using the random table. The sample quadrate size was taken 20m×20m for a tree, 5m×5m for a sapling, and 1m×1m for the seedling. In five community forests, altogether 30 quadrates were taken for a tree, 60 nested quadrates were taken for a sapling and 120 nested quadrates were taken for a seedling. The tree layer, sapling layer and seedling layer were differentiated by taking reference tothe Diameter at Breast Height (DBH) class. An individual having DBH ≥ 5cm is considered a tree, an individual having DBH value between 1cm to &lt; 5cm is considered a sapling, and individuals having 1cm to &lt; 5cm DBH are considered as a seedling. The DBH distribution curve was obtained by plotting diameter class in x- axis and density on y- axis. All studied community forests are mixed forest dominated by tree species Castanopsis indica, Diospyros embryopteris (Diospyros malabarica), Shorea robusta, and Schima wallichii (Schima wallichii choisy). The regeneration potential of the Tilahar community forest(CF) is found high despite high grazing and other human intervention. The DBH class distribution curve of tree species is found as inverse J-shape, indicating that the overall forest has a sustainable regeneration.

Assessing the Best Fit Volume and Carbon Stock Equation of Pinus Roxburghii with Respect to Diameter at Breast Height Using Non-Destructive Method

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.

Forest structure and carbon stock of Suan Phueng Nature Education Park in Ratchaburi Province, Western Thailand

Abstract. Chanlabut U, Nahok B. 2022. Forest structure and carbon stock of Suan Phueng Nature Education Park in Ratchaburi Province, Western Thailand. Biodiversitas 23: 4314-4321. Forests play an important role in the global carbon budget. Yet, carbon stocks in tropical forests are uncertain depending on many factors. This study aims to study forest structures and carbon stocks in Suan Phueng Nature Education Park, Ratchaburi, Western Thailand. In 12 plots of 20 × 20 m, an inventory of trees ? 4.5 cm diameter at breast height (DBH) was carried out. Soil samples were also collected in sampling plots. To describe forest structures, ecological parameters were analyzed (IVI, diversity indices, basal area, and DBH size classes). Forest carbon stocks were calculated based on biomass and soils. Allometric equations were used to calculate aboveground biomass and converse to carbon stock. The soil carbon was analyzed using the wet oxidation method. The result showed that the lower montane forest (493.74 ± 90.20 Mg C ha-1) had the highest forest carbon stock, followed by the dry evergreen + mixed deciduous forest (203.83 ± 82.74 Mg C ha-1), and mixed deciduous forest (145.46 ± 47.90 Mg C ha–1). In the three forests, there were atotal of 637 trees belonging to 70 species in 29 families. Shannon’s diversity index was 3.59 with a range of 2.17-3.21, indicating a moderate to high diversity. Tree density was 1,137.50 stems ha-1 with a range of 737.50-1,581.25 stems ha-1. The basal area had a range of 5.82-11.11 m2 ha-1. The DBH classes exhibited J-shaped distribution. The large trees (?71 cm) had a greater aboveground carbon stock, despite their lower density. This indicates their importance as carbon sinks in the forest. This study highlights that the forests in Suan Phueng Nature Education Park not only have the potential to be carbon stocks but also contain a high diversity of tree species.

Floristic composition, structure and regeneration status of woody plant species in Northwest Ethiopia

Most of the natural forests in Awi Zone of Northwest Ethiopia exist as patches due to increasing human disturbance. The Bradi forest in this zone was assessed for its floristic composition, structure and regeneration status of woody plant species to better understand the natural dynamics and suggest appropriate conservation strategies. A total of 60 quadrats (20mx20m) were established along transect lines running parallel to each other using systematic sampling for vegetation sampling. Height and diameter at breast height (DBH) were measured for those woody plant species >2 m in height and >2 cm in DBH. Seventy-one woody plant species that belong to 64 genera and 40 families were identified, of which 36 (50.7%), 13 (18.3%), 13 (18.3%) and 9 (12.7%) were trees, lianas, shrubs and trees/shrubs, respectively. A total of 1838 stems ha−1 with DBH >2 cm and height >2 m were recorded. Albizia shimperiana, Paveta abyssinica, Croton macrostachyus, Discopodium penninervium, Teclea nobilis were the most abundant and frequently-occurrring species in the forest. The forest had a Shannon species diversity index score of 3.84 and an evenness of 0.89. Furthermore, the forest had an average basal area of 90.03m2/ha. Woody species with high basal area value such as Ekebergia capensis, A. shimperiana, Prunus africana, and C. macrostachyus were found to have greater importance value index (IVI). According to the DBH and height class distribution, the forest had an inverted J-shaped distribution pattern. However, analysis of regeneration status at species level revealed that 27.5%, 10%, 40% and 22.5% of the woody plants had good, fair, poor regeneration and not regenerating, respectively. This calls for enrichment planting and area exclosures of the study forest.

Floristic Composition of Trees in the Lowland Dipterocarp Forest of Kuala Keniam, Taman Negara, Pahang, Peninsular Malaysia

Abstract A study was conducted to determine the floristic composition and community structure of trees in lowland dipterocarp forest in Kuala Keniam, Taman Negara, Pahang. This forest is classified as a primary forest and among the oldest rain forest in the world. Five experimental plots with the dimension of 25 m x 20 m each (0.25 ha in total) had been established. The census was carried out for all trees with diameter at breast height (DBH) 5 cm and above. Species composition comprised of 244 individuals from 141 species, 94 genera and 36 families. The total number of taxa is varying across the five plots with the highest total number of families and species recorded in plot 5 with 21 and 43 taxa each. The lowest total number of families and species were recorded in plot 1 with only 14 families and 23 species. Euphorbiaceae is the most speciose family with 20 taxa and 66 individuals followed by Annonaceae with 14 taxa and 19 individuals. These two families are common in the lowland dipterocarp forests in Peninsular Malaysia. Main canopy and understorey and group were recorded with the highest number of species and individuals with 52 and 45 of species and 91 and 75 of individuals, respectively. Pioneer is very rare and was only represented by a single stem of Cratoxylum formosum and Sapium baccatum. Three species, namely Koompassia malaccensis, Elateriospermum tapos and Mallotus leucodermis were represented as the highest total number of individuals for DBH classes of ≥ 5 cm, ≥ 10 cm, ≥ 15 and ≥ 20 cm.

Population Structure and Regeneration Status of Woody Species in Kenech Forest, Southwest Ethiopia

Understanding the structural pattern and regeneration status of tree species is an important measure taken to assess the vegetation dynamics and their destruction factors species as well as management history and ecology of the forest. This study was conducted with the objective to assess the species diversity, structure, and regeneration status of woody species in Kenech natural forest, Ethiopia. Systematic random sampling method was employed as a sampling design for the collection of vegetation data. Accordingly, 40 plots of 20 m × 20 m were laid at every 100 m along four parallel transect lines following altitudinal gradient. Any woody species of trees and shrubs with the diameter at breast height (DBH) ≥2.5 cm was measured at 1.5 m from the ground. In each sample plots, all woody species seedling, sapling, and mature woody species were counted and recorded. A total of 80 plant species categorized into 67 genera and 28 families were recorded and identified, for description and analysis of vegetation structure. Structural analysis of the Kenech natural forest revealed a density of 840 stems/ha and a total basal area of 56.8 m2/ha. About 80.36% of the individuals are found in the first two classes (2.5–10 and 10–20 cm). The general pattern of DBH class distribution of woody species in the study area revealed an inverted J shape indicating the presence of a high density of trees in the lower DBH class than in the higher. The most dominant tree species relatively with the highest importance values recorded in the area were Pouteria adolfi-friedericii, Podocarpus falcatus, Celtis africana, Mimusops kummel, Pyschotria orophila, and Olea capensis subsp. macrocarpa. Forty-two species (64.61%) were represented by both seedling and sapling class, whereas 9 species (13.84%) were not regenerating.

Sustainable regeneration in uneven-aged mixed deciduous forests managed by selection silviculture: the role of demographic structure

Abstract Selection silviculture aims to create and maintain uneven-aged forests with a diameter at breast height (DBH) structure that is balanced at small spatial scales such that the stem number in each DBH class is high enough to replace the harvested and outgrowing trees over time by ingrowth from the next lower class. In these forests, natural regeneration of shade-tolerant species is at an advantage over shade-intolerant species. This is particularly pronounced in continuous-cover stands dominated by European beech (Fagus sylvatica L.), which develops its crown laterally as a reaction to release events. The conditions necessary to sustain a mixture with less shade-tolerant species, e.g. sycamore (Acer pseudoplatanus L.), have been little studied. Therefore, we explored growth patterns and stand structures in mixed deciduous forests with light availability quantified using vegetation height models. Harvesting and growth patterns were derived from inventory data of beech-dominated selection forests in Thuringia, Germany and long-term forest monitoring plot data from four stands in Switzerland. Based on these data, models of stem number distributions confirmed that stand basal area in deciduous forests dominated by beech should not exceed 21–25 m2 ha−1 to maintain a sustainable structure. In these forests, a total of ~90–120 stems per ha are needed in the ingrowth DBH class (DBH 8–11.9 cm) to ensure demographic sustainability. At canopy light transmittance &amp;lt;10 per cent, total stem number required in the thicket stage (DBH &amp;lt; 8 cm) is 800–1700 ha−1. Under such shady conditions, only a small proportion of sycamore was observed (&amp;lt;25 per cent) in the thicket stage, as the species is likely to require canopy gaps &amp;gt;400 m2 (gap diameter &amp;gt; 22.5 m) to recruit successfully. Selection silviculture with shade-intolerant species therefore requires much lower stocking volume and larger canopy openings created by group selection cutting than what is routinely applied in practical forest management using single-tree selection principles.

Growth Assessment of Tree Species Growing in the Amhara Region in Ethiopia

ABSTRACT Ethiopian mixed forests have multipurpose benefits and services. However, there is a gap of information in the entire Ethiopian highlands on forest growth needed for implementation of sustainable forest management and provision of ecosystem services. Therefore, main aim of this study was to identify main factors deriving tree growth in forest and woodland in Amhara Regional State of Ethiopia and to provide an individual tree basal area increment (BAI) model based on increment cores. The data came from 170 sampling plots in study area and cover 51 tree species. For each tree species, diameter at breast height (DBH), height, increment core measurement, tree location, and distance from subject tree measurements were recorded. Because of large number of trees species, it is difficult to develop growth functions for each individual tree species. Thus, classification of species groups provided a framework to organize information that differs between vegetation types. Our classification resulted in three groups. For each tree species group, an individual tree BAI model was calibrated. The tree species group of BAI differs by DBH class. The response to BAI depends on competitive condition of a tree. This growth model can be used to predict tree growth for Ethiopian mixed-species forests.

Relationship of H/D and crown ratio and tree growth for Chamaecyparis obtusa and Cryptomeria japonica in Korea

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.

Wood density and wood shrinkage in relation to initial spacing and tree growth in black spruce (Picea mariana)

This study has quantified basic wood density and various types of wood shrinkage in relation to initial spacing (or initial planting density) and tree growth based on a 48-year-old black spruce (Picea mariana) spacing trial in eastern Canada. A total of 139 sample trees were collected from four initial spacings (3086, 2500, 2066, 1372 trees/ha) for this study. Analyses of variance (ANOVA) show that initial spacing is the most important parameter affecting wood density significantly, followed by tree diameter at breast height (DBH) class. With increasing spacing, wood density, radial and volumetric shrinkage tend to decrease, whereas longitudinal shrinkage tends to increase gradually. The largest spacing has the lowest wood density, the smallest transverse shrinkage and the largest longitudinal shrinkage. Path analysis indicates that wood density is the most important parameter affecting transverse shrinkage, followed by the distance from the pith. Furthermore, much of the variation of the transverse shrinkage with wood density may be due to the initial spacing and tree DBH class. Path analysis also reveals that longitudinal shrinkage is mainly related to log height and tree DBH class. With increasing log height, longitudinal shrinkage tends to increase, and transverse shrinkage tends to decrease. With increasing DBH class, the trees tend to have an increasing longitudinal shrinkage and a decreasing transverse shrinkage. Overall, this study suggests that a large increase in the initial spacing (e.g., 1372 trees/ha) might lead to a significant reduction in both wood density and transverse shrinkage, and a significant increase in longitudinal shrinkage in black spruce.

Prediction and model-assisted estimation of diameter distributions using Norwegian national forest inventory and airborne laser scanning data

Diameter at breast height (DBH) distributions offer valuable information for operational and strategic forest management decisions. We predicted DBH distributions using Norwegian national forest inventory and airborne laser scanning data and compared the predictive performances of linear mixed-effects (PPM), generalized linear-mixed (GLM), and k nearest-neighbor (NN) models. While GLM resulted in smaller prediction errors than PPM, both were clearly outperformed by NN. We therefore studied the ability of the NN model to improve the precision of stem frequency estimates by DBH classes in the 8.7 Mha study area using a model-assisted (MA) estimator suitable for systematic sampling. MA estimates yielded greater than or approximately equal efficiencies as direct estimates using field data only. The relative efficiencies (REs) associated with the MA estimates ranged between 0.95–1.47 and 0.96–1.67 for 2 and 6 cm DBH class widths, respectively, when dominant tree species were assumed to be known. The use of a predicted tree species map, instead of the observed information, decreased the REs by up to 10%.

Comperative study of aboveground biomass and carbon storage between Tembawang and conventional rubber agroforestry in West Kalimantan Indonesia

In the era of intensive oil palm and rubber plantations in Kalimantan, some local communities of Dayak's tribe in West Kalimantan preserved the traditional agroforestry system "Tembawang". In the last two decades, rubber has been planted traditionally by local communities since the expansion of rubber industries. This study aimed to compare tree above ground biomass (AGB) distribution and carbon storage in different DBH (diameter at breast height) classes between Tembawang and conventional rubber plantation in West Kalimantan, Indonesia. Vegetation transect analysis was carried out on two types of traditional agroforestry namely Tembawang and conventional rubber. AGB estimation was based on the existing allometric, carbon storage was estimated from the percentage of biomass. Total AGB of Tembawang was higher than conventional rubber plantation and significantly different (p &lt; 0.01). The highest AGB accumulation both Tembawang and conventional rubber was found at above 50 cm diameter class. The aboveground carbon storage from Tembawang and conventional rubber plantation were 90.26 and 42.01 Mg C ha-1, respectively. The highest contribution to carbon storage was found at above 50 cm diameter class, estimated 62.58 % from Tembawang and 49.24 % from conventional rubber. AGB and carbon storage at traditional agroforestry in West Kalimantan were greater than varied different agroforestry system, also the estimated value was closed to tropical secondary forests. Tembawang agroforestry has good potential contribution to carbon storage and conservation of native fruit trees of Kalimantan.

Effects of standing culm density and fertilizer regimes on Dendrocalamus brandisii (Munro) Kurz shoot production at Simao District, southwestern China

Optimum shoot production in Dendrocalamus brandisii (Munro) Kurz depends on either standing culm density (SCD) or application of fertilizer. However, silvicultural application through the combined effect of SCD and fertilizer regimes is not fully understood. In this study, effects of SCD and fertilizer regimes, relationships between silvicultural treatments and growth parameters and model prediction on shoot production were conducted. A split-plot factorial design was applied in three blocks consisting of two main factors (SCD and fertilizer regimes). These were three SCD levels (2-1, 2-2 and control) and six fertilizer regimes (15 kg clump−1 compost; 0.25 kg clump−1 NPK mixed with 7.5 kg clump−1 compost; 0.5 kg clump−1 NPK; 0.75 kg clump−1 NPK; 1 kg clump−1 NPK; and control). Data collection on culms height, Diameter at breast height (DBH), soil properties and total number of shoots and shoot yield) was conducted from early July to mid-October. A total of 3,380 edible shoots ha−1 and 7.1 ton ha−1 shoot yield were harvested. Higher available nutrients (P and K) and total soil organic carbon (SOC) were associated by favorable soil pH, higher cation exchange capacity (CEC) and lower exchangeable acidity (EA) after fertilizer application. The largest shoot yield (12.04 ton ha−1) was recorded in 2-2 SCD responded to 0.75 kg clump−1 NPK. Shoot production further improved from 0.5 kg clump−1 NPK to 0.75 kg clump−1 and eventually declined to 1 kg. Linear mixed-effects model (LMM) showed that shoot yield had a positive and significant correlation (p<0.05) among D. brandisii silvicultural treatments and culm DBH classes. Our finding indicates that silvicultural application (SCD and fertilizer regimes) in relation to culm DBH classes could be a key factor for higher D. brandisii shoot production.

How evergreen and deciduous trees coexist during secondary forest succession: Insights into forest restoration mechanisms in Chinese subtropical forest

Deciduous broadleaved forests and evergreen broadleaved forests constitute the majority of global subtropical forests. Subtropical vegetation has faced strong anthropogenic pressures, and many natural forests destroyed throughout history have been restored to secondary forests due to various government conservation policies. In early forest restoration, deciduous and evergreen species with significantly different functional traits play different roles and jointly determine secondary forest successional trends, questioning how coexistence and competition between evergreen and deciduous trees profoundly impact community assembly and forest restoration. Although subtropical forest has been seriously threatened, scientific information on how these important ecological processes influence secondary forest regrowth is lacking. We established a 6-ha plot in a subtropical evergreen broadleaved forests in Guanshan National Nature Reserve, southeastern China. All trees individual were stem-mapped, identified to species and measured for diameter at breast height (DBH) and height. Pair-correlation and marked correlation functions indicated that deciduous species are comparatively more vulnerable to density-dependent regulation and size reduction in adjacent individuals during secondary forest succession. The interspecific association between deciduous and evergreen trees in the same DBH class gradually changes from significantly positive to negative as DBH increases, indicating seedling coexistence and competition between large late successional trees at a fine scale. Our results indicate that self-thinning caused by conspecific density-dependent regulation in deciduous trees and interspecific repulsion between evergreen and deciduous trees lead to forest gaps where clustered offspring naturally regenerate to coexist, embodying the important coexistence mechanisms facilitating secondary forest recovery to the zonal climax vegetation types dominated by evergreen species in this region. These findings improve our understanding of the self-recovery mechanisms of subtropical forests in secondary succession and provide important theoretical support to accelerate the future recovery of secondary forests.