Sacred forests play a valuable role in the conservation of local biodiversity and provide numerous ecosystem services in Cameroon. The aim of this study was to estimate floristic diversity, stand structures and carbon...Sacred forests play a valuable role in the conservation of local biodiversity and provide numerous ecosystem services in Cameroon. The aim of this study was to estimate floristic diversity, stand structures and carbon stocks in the sacred forests of Bandrefam and Batoufam (western Cameroon). The floristic inventory and the stand structures were carried out in 25 m × 25 m plots for individuals with diameters greater than 10 cm;5 m × 5 m for individuals with diameters less than 10 cm. Carbon stocks were estimated using the non-destructive method and allometric equations. The floristic inventory identified 65 species divided into 57 genera and 30 families in the Bandrefam sacred forest and 45 species divided into 42 genera and 27 families in the Batoufam sacred forest. In the Bandrefam, the most important families are Phyllanthaceae (53.98%), Moraceae (21.69%), Lamiaceae (20.15%). At Batoufam, the most important families are Phyllanthaceae (39.73%), Fabaceae (28.47%), Araliaceae (23.77%). Malacantha alnifolia (55.14%), Vitex grandifolia (18.43%), Bosqueia angolensis (15.06%) were the most important species in Bandrefam. Otherwise, Malacantha alnifolia (28%), Polyscias fulva (22.73%), Psychotria sp. (21.28%) were the most important in Batoufam. The Bandrefam sacred forest has the highest tree density (2669 stems/ha). Total carbon stock is 484.88 ± 2.28 tC/ha at Batoufam and 313.95 ± 0.93 tC/ha at Bandrefam. The economic value varies between 5858.04 ± 27.62 USD/ha in Batoufam sacred forest and 3788.51 ± 11.26 USD/ha in Bandrefam sacred forest. The number of individuals and small-diameter trees has little influence on the carbon stocks in the trees. Medium-diameter trees store the most carbon, and very large-diameter trees, which are very poorly represented, store less carbon. In another way, wood density and the basal areas influence the carbon storage of the trees.展开更多
The distance from the river is a crucial factor that affects the structure and function of desert riparian forests,impeding their regeneration and biodiversity due to water conditions.However,few studies have confirme...The distance from the river is a crucial factor that affects the structure and function of desert riparian forests,impeding their regeneration and biodiversity due to water conditions.However,few studies have confirmed the long-term variation in structure and function of this azonal riparian forest type caused by water stress.We hypothesize that a complex and diverse stand structure is associated with the distance from the river,and tree size plays a crucial role in establishing random frameworks for stability in forest stands.Our investigation was conducted in the lower Trim River.Based on long-term observation from 2005 to 2023,both stand structure parameters and diversity index were used.The variation in stand structure was analyzed using the least significant difference,and stand stability was assessed using Gaussian distribution and bivariate regression methods.Our study indicated that there were no significant differences in the response of size differentiation and crowding to distance from the river.However,a significant divergence in spatial pattern was observed at greater distances from the river,which became more pronounced over time.Regardless of the distance from the river or time-scale,there were significant differences in DBH,crown diameter and length.Furthermore,structural diversity exhibited varying trends with distance from the river and time-scale,indicating a diverse and complex pattern in stand structure due to water stress.The proportion of random frameworks for stability is influenced by the distance from the river,and tree size,especially crown diameter and length,plays an important role.Our research examines the multiple relationships among water conditions,forest structure,and function in an arid region,highlighting the significance of water conditions in the natural restoration of desert riparian forest ecosystems.The findings provide new insights for further exploration of the relationship between stand structure and stability,enhancing our understanding of the theory of random frameworks-stability.Overall,the study provides scientific guidance for sustainable forest management and conservation in the context of a changing climate,particularly regarding water stress.展开更多
This study examined size inequality and size-growth relationships as essential aspects of stand structure in loblolly pine plantations(Pinus taeda L.),particularly focusing on a critical stage with strong competition ...This study examined size inequality and size-growth relationships as essential aspects of stand structure in loblolly pine plantations(Pinus taeda L.),particularly focusing on a critical stage with strong competition from mid-rotation to rotation age and changes due to thinning.Data were from a loblolly pine thinning study of multiple sites in the western Gulf region,USA,which were thinned around age 14.Four treatments were evaluated:three thinning intensities(TIs:residual densities of 740,555,and 370 trees·ha^(-1))and an unthinned control.An operational thinning method was implemented,involving the removal of every fifth row and selective thinning from below to achieve the desired intensity.The Gini index(GI)for diameter at breast height(DBH),height(H),and volume was computed annually for the first five years since thinning and at year seven,while growth dominance(GD)of these traits was calculated by growth interval.The control exhibited increasing trends over the year in GIs and greater inequality in DBH compared to height(GI=0.10 vs.0.04),and thinning reduced both GIs.Competition for DBH growth in the control was weakly asymmetric(GD=0.06),and thinning decreased GD,fostering weaker asymmetric competitive environments.The control displayed reverse asymmetric competition for height(GD=-0.10),and thinning strengthened reverse dominance.The thinning effects on reducing GIs and GD increased with TI.The observed patterns of competition appear to stem from adaptive resource allocation strategies rather than being influenced by neighboring tree sizes.The tree volume(VOLT)-based GI and GD might overestimate size inequality for DBH or height,and misinterpret GD for height.Stand volume growth in the control is linearly related to GD,being negative for DBH and positive for height,indicating GD offers valuable insights into stand growth dynamics.Thinning did not change the relationships but slowed the rates of change.The decline in stand growth associated with reduced DBH GD by thinning suggests that GD itself may not be the primary causal factor behind growth changes by thinning.展开更多
The optimum models of harvesting yield and net profits of large diameter trees for broadleaved forest were developed, of which include matrix growth sub-model, harvesting cost and wood price sub-models, based on the d...The optimum models of harvesting yield and net profits of large diameter trees for broadleaved forest were developed, of which include matrix growth sub-model, harvesting cost and wood price sub-models, based on the data from Hongshi Forestry Bureau, in Changbai Mountain region, Jilin Province, China. The data were measured in 232 permanent sample plots. With the data of permanent sample plots, the parameters of transition probability and ingrowth models were estimated, and some models were compared and partly modified. During the simulation of stand structure, four factors such as largest diameter residual tree （LDT）, the ratio of the number of trees in a given diameter class to those in the next larger diameter class （q）, residual basal area （RBA） and selective cutting cycle （C） were considered. The simulation results showed that the optimum stand structure parameters for large diameter trees are as follows： q is 1.2, LDT is 46cm, RBA is larger than 26 m^2 and selective cutting cycle time （C） is between 10 and 20 years.展开更多
As the premise and foundation conditions of stand growth and management visualization,stand structure visualization is a key part of stand visualization.Considering the particularity of stand structure data,we filter ...As the premise and foundation conditions of stand growth and management visualization,stand structure visualization is a key part of stand visualization.Considering the particularity of stand structure data,we filter and standardize the necessary factors.To intuitively simulate the spatial and attributive structure of the stand,our objective was to transfer the field coordinates into screen coordinates and to render two-dimensional abridged general view of every single tree one by one.This essay takes GDI ＋ technology as basis and uses C# in.NET Framework to generate two-dimensional spatial structure diagram which can show the stand density,crown density,spatial distribution pattern and so on.Meanwhile,it generates the histogram to reflect the distribution of stand structure attributes and finally achieves the goal of the visualization of stand structure.展开更多
Understanding stand structure and height-diameter relationship of trees provides very useful information to establish appropriate countermeasures for sustainable management of endangered forests. Populus euphratica, a...Understanding stand structure and height-diameter relationship of trees provides very useful information to establish appropriate countermeasures for sustainable management of endangered forests. Populus euphratica, a dominant tree species along the Tarim River watershed, plays an irreplaceable role in the sustainable development of regional ecology, economy and society. However, as the result of climate changes and human activities, the natural riparian ecosystems within the whole river basin were degraded enormously, particularly in the lower reaches of the river where about 320 km of the riparian forests were either highly degraded or dead. In this study, we presented one of the main criteria for the assessment of vitality of P. euphrafica forests by estimating the defoliation level, and analyzed forest structure and determined the height-diameter （height means the height of a tree and diameter means the diameter at breast height （DBH） of a tree） relationship of trees in different vitality classes （i.e. healthy, good, medium, senesced, dying, dead and fallen）. Trees classified as healthy and good ac- counted for approximately 40% of all sample trees, while slightly and highly degraded trees took up nearly 60% of total sample trees. The values of TH （tree height） and DBH ranged from 0-19 m and 0-125 cm, respectively. Trees more than 15 m in TH and 60 cm in DBH appeared sporadically. Trees in different vitality classes had different distribution patterns. Healthy trees were mainly composed more of relatively younger trees than of degraded tress. The height-diameter relationships differed greatly among tress in different vitality classes, with the coefficients ranging from 0.1653 to 0.6942. Correlation coefficients of TH and DBH in healthy and good trees were higher than those in trees of other vitality classes. The correlation between TH and DBH decreased with the decline of tree vitality. Our results suggested that it might be able to differentiate degraded P. euphratica trees from healthy trees by determining the height-diameter correlation coefficient, and the coefficient would be a new parameter for detecting degradation and assessing sustainable management of floodplain forests in arid regions. In addition, tree vitality should be taken into account to make an accurate height-diameter model for tree height prediction.展开更多
Tree species diversity and population structure at different community types were described and analyzed for primary and secondary lowland moist deciduous forests in Tripura. Overall 10,957 individual trees belonging ...Tree species diversity and population structure at different community types were described and analyzed for primary and secondary lowland moist deciduous forests in Tripura. Overall 10,957 individual trees belonging to 46 family, 103 genera and 144 species were counted at ≥30 cm DBH （diameter at breast height） using 28 permanent belt transects with a size of 1 ha （10 m × 1000 m）. Four different tree communities were identified. The primary forests was dominated by Shorea robusta （mean density 464.77 trees.ha^-1, 105 species） and Schima wallichii （336.25 trees.ha^-1, 82 species）, while the secondary forests was dominated by Tectona grandis （333.88 trees.ha^-1, 105 species） and Hevea brasiliensis （299.67 trees.ha^-1, 82 species）. Overall mean basal area in this study was 18.01m2.ha^-1; the maximum value was recorded in primary Shorea forest （26.21 m2.ha^-1）. Mean density and diversity indices were differed significantly within four different communities. No significant differences were observed in number of species, genera, family and tree basal cover area. Significant relationships were found between the species richness and different tree population groups across the communities. Results revealed that species diversity and density were increased in those forests due to past disturbances which resulted in slow accumu- lation of native oligarchic small tree species. Seventeen species were recorded with 〈2 individuals of which Saraca asoka （Roxb.） de Wilde and Entada phaseoloides （L.） Men＇. etc. extensively used in local ethnomedicinal formulations. The present S. robusta Gaertn dominated forest was recorded richer （105 species） than other reported studies. Moraceae was found more speciose family instead of Papilionaceae and Euphorbiaceae than other Indian moist deciduous forests. Seasonal phenological gap in such moist deciduous forests influenced the population of Trachypithecus pileatus and capped langur. The analysis of FIV suggested a slow trend of shifting the population of Lamiaceae group by Moraceae species in secondary T. grandis L. dominated community.展开更多
A study was carried out to evaluate the effect of shelterwood cutting methods on stand structure and regeneration density. Data were collected from a northern hardwood forest stands in Iran with Fagus orientalis Lipsk...A study was carried out to evaluate the effect of shelterwood cutting methods on stand structure and regeneration density. Data were collected from a northern hardwood forest stands in Iran with Fagus orientalis Lipsky as dominant species, with/without shelterwood cutting operation. Results clearly demonstrate that the management of Fagus orientalis Lipsky with shelterwood cutting system affected the frequency and diversity of the understory herbaceous species. The frequency of Viola silvestris Lam., Asperula odorata L., Carex spp. and Rubus hyr-canus Juz increased significantly after shelterwood cutting. The DBH （diameter at breast height） of commercial species in control stands （57.50±2.15 cm） was greater than that in treated stands （50.67±1.88 cm）, whereas the total height of trees was similar between treated and control plots （21±0.5 m）. The number of Parrotia persica seedlings increased by 13.2% from 1995 to 2005 whereas the number of Fagus orientalis and Carpinus betulus seedlings significantly decreased from 1995 to 2005. In conclusion, it confirms that instead of shelterwood cutting method other silvicultural practices such as selection cutting method should be applied for the mountainous beech stands of Hyrcanian forests.展开更多
Structural diversity is the key attribute of a stand. A set of biodiversity measures in ecology was introduced in forest management for describing stand structure, of which Shannon information entropy (Shannon index) ...Structural diversity is the key attribute of a stand. A set of biodiversity measures in ecology was introduced in forest management for describing stand structure, of which Shannon information entropy (Shannon index) has been the most widely used measure of species diversity. It is generally thought that tree size diversity could serve as a good proxy for height diversity. However, tree size diversity and height diversity for stand structure is not completely consistent. Stand diameter cannot reflect height information completely. Either tree size diversity or height diversity is one-dimensional information entropy measure. This paper discussed the method of multiple-dimensional information entropy measure with the concept of joint entropy. It is suggested that joint entropy is a good measure for describing overall stand structural diversity.展开更多
We studied relationships between stand structure and stand stability according to thinning intensity in an afforested oriental beech stand. Various thinning intensities were applied in sample stands. We sampled eight ...We studied relationships between stand structure and stand stability according to thinning intensity in an afforested oriental beech stand. Various thinning intensities were applied in sample stands. We sampled eight plots in stands that were lightly thinned, eight plots in heavily thinned stands and eight plots in unthinned stands as a control. Height and diameter distributions of the stands were measured to assess stand structure. We quantified individual tree stability and collective stability. Heavy thinning during the first thinning operation damaged the storied structure of the stand in thicket stage and affected collective structuring ability. While most control plots had multi-storied stands, after light and heavy thinning two-storied structure became more common.Large gaps occurred in the canopy after heavy thinning. On average, nine tree collectives were formed per sampling plot in the untreated stand, seven collectives after thinning in 2008 and four collectives after thinning in 2009. Stable trees accounted for 17 % of trees in control plots, 24 % in lightly thinned plots, and 15 % in heavily thinned plots. Collective stability values were 83 % in control plots, 82 % in lightly thinned plots and 36 % in heavily thinned plots. We conclude that it is necessary to retain collective structuring capacity during thinning operations for sustaining stand stability.展开更多
Background： Forest ecosystem functioning is strongly influenced by the absorption of photosynthetically active radiation （APAR）, and therefore, accurate predictions of APAR are critical for many process-based fores...Background： Forest ecosystem functioning is strongly influenced by the absorption of photosynthetically active radiation （APAR）, and therefore, accurate predictions of APAR are critical for many process-based forest growth models. The Lambert-Beer law can be applied to estimate APAR for simple homogeneous canopies composed of one layer, one species, and no canopy gaps. However, the vertical and horizontal structure of forest canopies is rarely homogeneous. Detailed tree-level models can account for this heterogeneity but these often have high input and computational demands and work on finer temporal and spatial resolutions than required by stand-level growth models. The aim of this study was to test a stand-level light absorption model that can estimate APAR by individual species in mixed-species and multi-layered stands with any degree of canopy openness including open-grown trees to closed canopies. Methods： The stand-level model was compared with a detailed tree-level model that has already been tested in mixed-species stands using empirical data. Both models were parameterised for five different forests, including a wide range of species compositions, species proportions, stand densities, crown architectures and canopy structures. Results： The stand-level model performed well in all stands except in the stand where extinction coefficients were unusually variable and it appears unlikely that APAR could be predicted in such stands using （tree- or stand-level） models that do not allow individuals of a given species to have different extinction coefficients, leaf-area density or analogous parameters. Conclusion： This model is parameterised with species-specific information about extinction coefficients and mean crown length, diameter, height and leaf area. It could be used to examine light dynamics in complex canopies and in stand-level growth models.展开更多
Diversity-biomass relationships(DBRs)in terrestrial ecosystems tend to vary across spatial scales,but,particularly in hyperdiverse forests,the mechanisms driving these trends remain uncertain.Until now,few have simult...Diversity-biomass relationships(DBRs)in terrestrial ecosystems tend to vary across spatial scales,but,particularly in hyperdiverse forests,the mechanisms driving these trends remain uncertain.Until now,few have simultaneously investigated the connections between tree species diversity,stand structural diversity,mycorrhizal associations,and ecosystem functioning.In addition,DBRs have only been studied at limited spatial scales,with limited focus on the direct and indirect effects of environmental factors.We addressed these research gaps using a 30-ha forest dynamics plot located in Pu'er City,Southwest China.Through piecewise structural equation models,we quantified the direct effects of tree species diversity(α,β,γ),stand structural diversity,mycorrhizal associations(AM,EcM),and the environmental factors(soil fertility and topography),as well as the indirect effects of the environmental factors on aboveground tree biomass across spatial scales ranging from 400 to 230,400 m^(2).We hypothesized that complex interactions among these factors underpin the variation in DBRs in natural ecosystems across spatial scales.Our results showed that environmental conditions indirectly affected the tree biomass via changes in tree species diversity,and these effects became stronger as the spatial scale increased.At small to moderate spatial scales,environmental factors were more predictive of tree biomass than tree species diversity(or its components);the effects of stand structural diversity on biomass also gradually increased with spatial scale.Conversely,from the intermediate to the largest spatial scales,mycorrhizal associations gradually became the best predictors of DBR dynamics.Our research offers novel empirical evidence demonstrating the importance of environmental conditions,structural diversity,and mycorrhizal associations in shaping cross-scale DBRs.Future comprehensive studies should consider these factors to assess the mechanisms shaping scale-dependent DBRs in complex natural ecosystems.展开更多
Stand structure dynamics are considered as major happenings in any forest as a response to environmental changes.However,this important topic is underrepresented in the treeline studies in the Nepal Himalayas.We aimed...Stand structure dynamics are considered as major happenings in any forest as a response to environmental changes.However,this important topic is underrepresented in the treeline studies in the Nepal Himalayas.We aimed to investigate site-as well as species-specific changes in morphometric features(basal diameter,crown cover,density,and height)along the elevational gradient across treeline ecotones in response to recent environmental changes.The stand structure characteristics of Abies spectabilis,Pinus wallichiana,and Betula utilis across the treeline ecotone of three study sites in Eastern(Barun),Central(Manang),and Western(Dhorpatan)Nepal were analyzed to elucidate structural heterogeneities.Altogether,eight transects(20 m×(60–250 m))across the treeline ecotone were established.Trees of all life forms,trees(>2 m),saplings(0.5–2 m),and seedlings(<0.5 m),within each transect were enumerated and sampled for the morphometric features and age.Site-specific and species-specific stand structure dynamics were found.The rate of basal area increment was higher in Barun,but the Manang treeline,despite profound regeneration in recent years,had a low annual basal area increment.Moreover,the altitudinal distribution of age and morphometry were not consistent among those ecotones.Furthermore,intra-specific competition was not significant.The site-specific stand structure dynamics explain why treelines do not respond uniformly to increasing temperature.It invokes,in further studies,the incorporation of the tree’s morphometric adaptation traits,phenotypic plasticity,and interactions between species genotype and the environment.展开更多
On an agrosilvopastoral farm in central Italy where Maremmana cattle graze in Turkey oak forests,we evaluated the impact of different livestock densities on stand structure,tree diversity and natural regeneration in f...On an agrosilvopastoral farm in central Italy where Maremmana cattle graze in Turkey oak forests,we evaluated the impact of different livestock densities on stand structure,tree diversity and natural regeneration in four types of grazed areas based on the grazing regime adopted:calf-grazed,high-intensity-grazed,low-intensity-grazed,ungrazed control.For each area,we set up three permanent circular plots(radius of 15 m)to survey the structural and dasometric characteristics of the overstorey,understorey,and regeneration layer.The results showed that grazing negatively affected the complexity of the forest structure and its potential to regenerate and maintain a high level of biodiversity.The differences in stand structure observed between the grazing areas were closely related to livestock density.The most sensitive components of the system were the understorey and the regeneration layers.Contrarily,the current grazing management did not affect the dominant tree structure or its composition.Our findings identified medium-term monitoring and regeneration management as the two significant aspects to consider when assessing sustainable livestock.New forests can be established by excluding graz-ing for about 20–25 years.展开更多
Savanna woodlands in Sudan host great biodiversity, provide a plethora of ecosystem goods and services to local communities, and sustain numerous ecological functions. Although the importance of the Acacia trees in th...Savanna woodlands in Sudan host great biodiversity, provide a plethora of ecosystem goods and services to local communities, and sustain numerous ecological functions. Although the importance of the Acacia trees in these areas is well known, up-to-date information about these woodlands' diversity is limited and changes in their woody vegetation composition, density, diversity and relative frequency are not monitored over time. This study explored tree diversity and stand stage structure in Nuara Reserved Forest, a typical savanna woodland ecosystem in southeastern Sudan. A total of 638 circular sample plots(1000 m^2 for each) were established using a systematic sampling grid method. The distance between plots was 200 m. In each plot, all living trees with diameter at breast height(DBH) ≥5.00 cm were identified and counted, and their DBH values were recorded. From these data, tree composition, diversity, density and stage structure were assessed. There were 12,259 individual trees representing four species(Acacia seyal, Balanites aegyptiaca, Acacia Senegal and Acacia mellifera) that belong to two families. The dominant species was Acacia seyal. Average tree density was 191 trees/hm^2 and the Shannon-Weiner index for trees diversity was 0.204. Overall, young trees comprised 86.30% of the forest. The state of tree richness and density in the study area was low compared to other similar environments in the region and around the world. We recommended adoption of a proper management system that includes monitoring of woody vegetation diversity in this forest, and management actions to enhance tree diversity and sustain ecosystem services to local communities. In addition to care for the dominant Acacia seyal stands, more attention and conservation should be devoted to reestablishing Acacia senegal and Acacia mellifera trees because of their high ecological and economic values for local communities.展开更多
Background:Forest management affects the habitat conditions for many forest-dwelling species.Among them,the capercaillie(Tetrao urogallus)is a rare forest grouse inhabiting old,mature forests.We compared the structure...Background:Forest management affects the habitat conditions for many forest-dwelling species.Among them,the capercaillie(Tetrao urogallus)is a rare forest grouse inhabiting old,mature forests.We compared the structure of forest habitat among 9 active and 9 abandoned leks in the Augustow Forest(North-Eastern Poland),within a radius of 1 km of the leks,defined as the Key Areas for the capercaillie in lowland temperate forest.Habitat measurements were conducted on 1779 circular plots.Assessments made on all plots related to 13 habitat variables measured or noted in the field,including stand structure,canopy closure,stand developmental stage,percentage of Scots pine(Pinus sylvestris),soil fertility and soil moisture,the share of undergrowth,the cover of shrubs,the cover of bilberry(Vaccinium sp.),and the presence of certain habitat elements important to the capercaillie.Results:To compare the still-occupied and the abandoned KAs for the capercaillie,a logistic regression model was developed.The variables best explaining differences between these two categories were:the occurrence of undergrowth layers,canopy closure in the second canopy layer,and stand age.According to the model,with the increase of the shrub-layer cover as well as the density of trees,the probability of the presence of the capercaillie decreased.The capercaillie in the area of the Augustow Forest occupy mainly dry and poor,middle-aged,pinedominated forests,with a moderate extent of stand canopy closure and only weakly-developed layers of undergrowth.Conclusions:The filling-in of mature stands with sub-canopy trees and shrubs(the process which is stimulated by climate change and site eutrophication)causes structural changes,which are unfavourable to the capercaillie.This might explain why in the course of the recent decades the capercaillie has abandoned the oldest stands,distinguished by the presence of bigger shares of undergrowth.The capercaillie has shifted to younger stands,which reveal a lesser extent of canopy closure and a more limited development of understorey vegetation.展开更多
The artificial pure and mixed Korean pine (Pinus koraiensis) forests were investigated at Dailing Forestry Bureau in Xiaoxing'an mountains from 1990 to 1992. Depending on the distance between the samplings of Kore...The artificial pure and mixed Korean pine (Pinus koraiensis) forests were investigated at Dailing Forestry Bureau in Xiaoxing'an mountains from 1990 to 1992. Depending on the distance between the samplings of Korean pine and their neighbor trees, the neighbor tree height, the size of neighbor tree canopy, and dimension of neighbor tree. The forest structure was classified into three types: (1) prowth of a tree in the light (open), (2) Growth of a tree in the canopy gap (Gap), (3)Growth of a tree under broad-leaved tree canopy. The frequeney, height, and age of stem divergence of Korean pine tree were investigated by sampling trees. The temporal and spatial model of the tree growth was applied on basis of the height of stem divergence, ratio of height and DBH, and character of tree stem.The morphology and growth character of Korean pine trees during different development stage were forecasted.展开更多
The present study aimed to contribute to the sustainable management of the Ngambe-Ndom-Nyanon communal forest in Cameroon. Thus, an evaluation of the floristic diversity and stand structure of the forest was carried o...The present study aimed to contribute to the sustainable management of the Ngambe-Ndom-Nyanon communal forest in Cameroon. Thus, an evaluation of the floristic diversity and stand structure of the forest was carried out. By using systematic sampling, a diverse inventory of the plant species was carried out, taking into account the dendrometric measurements of all the species present in the forest (trees, shrubs, herbs). Data were analyzed with Microsoft Excel software to bring out curves and histograms. This software also made it possible to produce tables and also to come up with different diversity indexes. A total of 19,007 individuals from 395 plant species grouped into 99 families were identified in the area. The family Euphorbiaceae was the most represented. Species dominated in this stand were Uapaca guineensis and Pycnanthus angolensis with 9% and 6% of individuals identified. The result of the Shannon index showed that all the strata in the forest are diversified with the highest values in the adult secondary forest (FSA) with indices of 4.74, followed by young secondary forest (FSJ) and the secondary forest (FS) with indice respectively 4.68 and 4.61. The values of the Sorensen index show that 100% of species are common in the young secondary forest (FSJ) and the adult secondary forest (FSA). In the same forest, the FSA and Swamp with FSJ and Swamp have just 15% of species in common respectively. This diversified forest stand projects an inverted J structure, thus testifying to its strong potential for stems of the future. According to the research objectives, some measures were proposed for sustainable management of this forest, such as the reforestation of areas degraded by agricultural activities and the promotion of agroforestry practices by using trees with the high fertilizing potential to improve agricultural yields while preserving the trees in place.展开更多
In order to understand the stand structure and growth of phellodendron amurense plantation in limestone mountain, 11-year-old phellodendron amurense plantation with good growth was selected in Da'an Township, Long...In order to understand the stand structure and growth of phellodendron amurense plantation in limestone mountain, 11-year-old phellodendron amurense plantation with good growth was selected in Da'an Township, Longshan County, Hu’nan Province. A temporary sample plot of 3000m2 was set up to investigate factors such as DBH, tree height, branch height and crown width of each tree. The results showed that the average diameter at breast height, tree height, height to diameter ratio, branch height, crown width, crown height ratio and crown width area of 11-year-old phellodendron amurense plantation with density of 1483-2500 plants /hm2 in limestone mountain area were 8.63cm, 8.74m, 105.4, 4.05m, 2.79m, 0.52 and 6.62m2 respectively;The main factors affecting the height growth of phellodendron amurense are soil fertility and soil physical and chemical properties. The DBH structure of stand approaches normal distribution;The height structure of the stand tree presents typical normal distribution;The above range of stand density had no significant effect on stand growth;The 11-year-old phellodendron amurense forest has obvious differentiation and needs thinning and tending. The 11-year-old phellodendron amurense plantation has entered the beginning stage of middle forest.展开更多
The paper deals with the stand structure and yield of black locust (Robinia pseudoacacia L.) forests mixed with white (Populus alba L.) in various proportions, partly applying a new methodological approach. The main s...The paper deals with the stand structure and yield of black locust (Robinia pseudoacacia L.) forests mixed with white (Populus alba L.) in various proportions, partly applying a new methodological approach. The main stand structure and yield factors were determined separately for each species, measured stem by stem, using the volume functions prepared for each species. The ratio of the volumes of the species (A and B) in mixed and in pure stands (based on volume tables) was determined. A close relationship has been found between the ratio by relative total volume and the proportion (by the number of stems) of the species. The relative surplus in the volume of the mixed stands varied between 1.24-1.55 at the age of 16 compared to the control, i.e. the yield of pure stands of the species concerned. The trial has also proven that if two species have a fast initial growth rate and a similar rotation age, they can be planted in mixed stands resulting in mutual advantages.展开更多
文摘Sacred forests play a valuable role in the conservation of local biodiversity and provide numerous ecosystem services in Cameroon. The aim of this study was to estimate floristic diversity, stand structures and carbon stocks in the sacred forests of Bandrefam and Batoufam (western Cameroon). The floristic inventory and the stand structures were carried out in 25 m × 25 m plots for individuals with diameters greater than 10 cm;5 m × 5 m for individuals with diameters less than 10 cm. Carbon stocks were estimated using the non-destructive method and allometric equations. The floristic inventory identified 65 species divided into 57 genera and 30 families in the Bandrefam sacred forest and 45 species divided into 42 genera and 27 families in the Batoufam sacred forest. In the Bandrefam, the most important families are Phyllanthaceae (53.98%), Moraceae (21.69%), Lamiaceae (20.15%). At Batoufam, the most important families are Phyllanthaceae (39.73%), Fabaceae (28.47%), Araliaceae (23.77%). Malacantha alnifolia (55.14%), Vitex grandifolia (18.43%), Bosqueia angolensis (15.06%) were the most important species in Bandrefam. Otherwise, Malacantha alnifolia (28%), Polyscias fulva (22.73%), Psychotria sp. (21.28%) were the most important in Batoufam. The Bandrefam sacred forest has the highest tree density (2669 stems/ha). Total carbon stock is 484.88 ± 2.28 tC/ha at Batoufam and 313.95 ± 0.93 tC/ha at Bandrefam. The economic value varies between 5858.04 ± 27.62 USD/ha in Batoufam sacred forest and 3788.51 ± 11.26 USD/ha in Bandrefam sacred forest. The number of individuals and small-diameter trees has little influence on the carbon stocks in the trees. Medium-diameter trees store the most carbon, and very large-diameter trees, which are very poorly represented, store less carbon. In another way, wood density and the basal areas influence the carbon storage of the trees.
基金supported by the Third Xinjiang Scientific Expedition and Research Program of the Ministry of Science&Technology of China(Grant No:2022xjkk0300)National Science Foundation of China(Grant No:32260285)+1 种基金Graduate Research Innovation Project of the Xinjiang Uygur Autonomous Region(Grant No:XJ2024G049)Excellent Doctoral Innovation Program of Xinjiang University(Grant No:XJU2024BS121).
文摘The distance from the river is a crucial factor that affects the structure and function of desert riparian forests,impeding their regeneration and biodiversity due to water conditions.However,few studies have confirmed the long-term variation in structure and function of this azonal riparian forest type caused by water stress.We hypothesize that a complex and diverse stand structure is associated with the distance from the river,and tree size plays a crucial role in establishing random frameworks for stability in forest stands.Our investigation was conducted in the lower Trim River.Based on long-term observation from 2005 to 2023,both stand structure parameters and diversity index were used.The variation in stand structure was analyzed using the least significant difference,and stand stability was assessed using Gaussian distribution and bivariate regression methods.Our study indicated that there were no significant differences in the response of size differentiation and crowding to distance from the river.However,a significant divergence in spatial pattern was observed at greater distances from the river,which became more pronounced over time.Regardless of the distance from the river or time-scale,there were significant differences in DBH,crown diameter and length.Furthermore,structural diversity exhibited varying trends with distance from the river and time-scale,indicating a diverse and complex pattern in stand structure due to water stress.The proportion of random frameworks for stability is influenced by the distance from the river,and tree size,especially crown diameter and length,plays an important role.Our research examines the multiple relationships among water conditions,forest structure,and function in an arid region,highlighting the significance of water conditions in the natural restoration of desert riparian forest ecosystems.The findings provide new insights for further exploration of the relationship between stand structure and stability,enhancing our understanding of the theory of random frameworks-stability.Overall,the study provides scientific guidance for sustainable forest management and conservation in the context of a changing climate,particularly regarding water stress.
基金supported by the McIntire-Stennis program and ETPPRP.
文摘This study examined size inequality and size-growth relationships as essential aspects of stand structure in loblolly pine plantations(Pinus taeda L.),particularly focusing on a critical stage with strong competition from mid-rotation to rotation age and changes due to thinning.Data were from a loblolly pine thinning study of multiple sites in the western Gulf region,USA,which were thinned around age 14.Four treatments were evaluated:three thinning intensities(TIs:residual densities of 740,555,and 370 trees·ha^(-1))and an unthinned control.An operational thinning method was implemented,involving the removal of every fifth row and selective thinning from below to achieve the desired intensity.The Gini index(GI)for diameter at breast height(DBH),height(H),and volume was computed annually for the first five years since thinning and at year seven,while growth dominance(GD)of these traits was calculated by growth interval.The control exhibited increasing trends over the year in GIs and greater inequality in DBH compared to height(GI=0.10 vs.0.04),and thinning reduced both GIs.Competition for DBH growth in the control was weakly asymmetric(GD=0.06),and thinning decreased GD,fostering weaker asymmetric competitive environments.The control displayed reverse asymmetric competition for height(GD=-0.10),and thinning strengthened reverse dominance.The thinning effects on reducing GIs and GD increased with TI.The observed patterns of competition appear to stem from adaptive resource allocation strategies rather than being influenced by neighboring tree sizes.The tree volume(VOLT)-based GI and GD might overestimate size inequality for DBH or height,and misinterpret GD for height.Stand volume growth in the control is linearly related to GD,being negative for DBH and positive for height,indicating GD offers valuable insights into stand growth dynamics.Thinning did not change the relationships but slowed the rates of change.The decline in stand growth associated with reduced DBH GD by thinning suggests that GD itself may not be the primary causal factor behind growth changes by thinning.
基金This paper was supported by National Strategy Key Project, Research and Paradigm on Ecological Harvesting and Regeneration Tech-nique for Northeast Natural Forest (2001BA510B07-02)
文摘The optimum models of harvesting yield and net profits of large diameter trees for broadleaved forest were developed, of which include matrix growth sub-model, harvesting cost and wood price sub-models, based on the data from Hongshi Forestry Bureau, in Changbai Mountain region, Jilin Province, China. The data were measured in 232 permanent sample plots. With the data of permanent sample plots, the parameters of transition probability and ingrowth models were estimated, and some models were compared and partly modified. During the simulation of stand structure, four factors such as largest diameter residual tree （LDT）, the ratio of the number of trees in a given diameter class to those in the next larger diameter class （q）, residual basal area （RBA） and selective cutting cycle （C） were considered. The simulation results showed that the optimum stand structure parameters for large diameter trees are as follows： q is 1.2, LDT is 46cm, RBA is larger than 26 m^2 and selective cutting cycle time （C） is between 10 and 20 years.
基金Supported by Key Project of Special Fund from Central Public Welfare Scientific Research Institution(IFRIT200904)948 Imported Project by State Forestry Administration(2008-4-61)~~
文摘As the premise and foundation conditions of stand growth and management visualization,stand structure visualization is a key part of stand visualization.Considering the particularity of stand structure data,we filter and standardize the necessary factors.To intuitively simulate the spatial and attributive structure of the stand,our objective was to transfer the field coordinates into screen coordinates and to render two-dimensional abridged general view of every single tree one by one.This essay takes GDI ＋ technology as basis and uses C# in.NET Framework to generate two-dimensional spatial structure diagram which can show the stand density,crown density,spatial distribution pattern and so on.Meanwhile,it generates the histogram to reflect the distribution of stand structure attributes and finally achieves the goal of the visualization of stand structure.
基金supported by International Science & Technology Cooperation Program of China (2010DFA92720-12)the National Natural Science Foundation of China (31360200)+1 种基金the German Volkswagen Foundation Eco CAR Project (Az88497)the German Federal Ministry of Education and Research (BMBF) within the framework of the Su Ma Ri O Project (01LL0918D)
文摘Understanding stand structure and height-diameter relationship of trees provides very useful information to establish appropriate countermeasures for sustainable management of endangered forests. Populus euphratica, a dominant tree species along the Tarim River watershed, plays an irreplaceable role in the sustainable development of regional ecology, economy and society. However, as the result of climate changes and human activities, the natural riparian ecosystems within the whole river basin were degraded enormously, particularly in the lower reaches of the river where about 320 km of the riparian forests were either highly degraded or dead. In this study, we presented one of the main criteria for the assessment of vitality of P. euphrafica forests by estimating the defoliation level, and analyzed forest structure and determined the height-diameter （height means the height of a tree and diameter means the diameter at breast height （DBH） of a tree） relationship of trees in different vitality classes （i.e. healthy, good, medium, senesced, dying, dead and fallen）. Trees classified as healthy and good ac- counted for approximately 40% of all sample trees, while slightly and highly degraded trees took up nearly 60% of total sample trees. The values of TH （tree height） and DBH ranged from 0-19 m and 0-125 cm, respectively. Trees more than 15 m in TH and 60 cm in DBH appeared sporadically. Trees in different vitality classes had different distribution patterns. Healthy trees were mainly composed more of relatively younger trees than of degraded tress. The height-diameter relationships differed greatly among tress in different vitality classes, with the coefficients ranging from 0.1653 to 0.6942. Correlation coefficients of TH and DBH in healthy and good trees were higher than those in trees of other vitality classes. The correlation between TH and DBH decreased with the decline of tree vitality. Our results suggested that it might be able to differentiate degraded P. euphratica trees from healthy trees by determining the height-diameter correlation coefficient, and the coefficient would be a new parameter for detecting degradation and assessing sustainable management of floodplain forests in arid regions. In addition, tree vitality should be taken into account to make an accurate height-diameter model for tree height prediction.
基金supported by DBT Network Project (BT/PR7928/NDB/52/9/2006)Department of Biotechnology(DBT),Govt. of India
文摘Tree species diversity and population structure at different community types were described and analyzed for primary and secondary lowland moist deciduous forests in Tripura. Overall 10,957 individual trees belonging to 46 family, 103 genera and 144 species were counted at ≥30 cm DBH （diameter at breast height） using 28 permanent belt transects with a size of 1 ha （10 m × 1000 m）. Four different tree communities were identified. The primary forests was dominated by Shorea robusta （mean density 464.77 trees.ha^-1, 105 species） and Schima wallichii （336.25 trees.ha^-1, 82 species）, while the secondary forests was dominated by Tectona grandis （333.88 trees.ha^-1, 105 species） and Hevea brasiliensis （299.67 trees.ha^-1, 82 species）. Overall mean basal area in this study was 18.01m2.ha^-1; the maximum value was recorded in primary Shorea forest （26.21 m2.ha^-1）. Mean density and diversity indices were differed significantly within four different communities. No significant differences were observed in number of species, genera, family and tree basal cover area. Significant relationships were found between the species richness and different tree population groups across the communities. Results revealed that species diversity and density were increased in those forests due to past disturbances which resulted in slow accumu- lation of native oligarchic small tree species. Seventeen species were recorded with 〈2 individuals of which Saraca asoka （Roxb.） de Wilde and Entada phaseoloides （L.） Men＇. etc. extensively used in local ethnomedicinal formulations. The present S. robusta Gaertn dominated forest was recorded richer （105 species） than other reported studies. Moraceae was found more speciose family instead of Papilionaceae and Euphorbiaceae than other Indian moist deciduous forests. Seasonal phenological gap in such moist deciduous forests influenced the population of Trachypithecus pileatus and capped langur. The analysis of FIV suggested a slow trend of shifting the population of Lamiaceae group by Moraceae species in secondary T. grandis L. dominated community.
文摘A study was carried out to evaluate the effect of shelterwood cutting methods on stand structure and regeneration density. Data were collected from a northern hardwood forest stands in Iran with Fagus orientalis Lipsky as dominant species, with/without shelterwood cutting operation. Results clearly demonstrate that the management of Fagus orientalis Lipsky with shelterwood cutting system affected the frequency and diversity of the understory herbaceous species. The frequency of Viola silvestris Lam., Asperula odorata L., Carex spp. and Rubus hyr-canus Juz increased significantly after shelterwood cutting. The DBH （diameter at breast height） of commercial species in control stands （57.50±2.15 cm） was greater than that in treated stands （50.67±1.88 cm）, whereas the total height of trees was similar between treated and control plots （21±0.5 m）. The number of Parrotia persica seedlings increased by 13.2% from 1995 to 2005 whereas the number of Fagus orientalis and Carpinus betulus seedlings significantly decreased from 1995 to 2005. In conclusion, it confirms that instead of shelterwood cutting method other silvicultural practices such as selection cutting method should be applied for the mountainous beech stands of Hyrcanian forests.
基金National Natural Science Foundation of China (Grant No. 30371157)
文摘Structural diversity is the key attribute of a stand. A set of biodiversity measures in ecology was introduced in forest management for describing stand structure, of which Shannon information entropy (Shannon index) has been the most widely used measure of species diversity. It is generally thought that tree size diversity could serve as a good proxy for height diversity. However, tree size diversity and height diversity for stand structure is not completely consistent. Stand diameter cannot reflect height information completely. Either tree size diversity or height diversity is one-dimensional information entropy measure. This paper discussed the method of multiple-dimensional information entropy measure with the concept of joint entropy. It is suggested that joint entropy is a good measure for describing overall stand structural diversity.
基金supported by Karadeniz Technical University Research Fund,Project number 2010.113.001.11
文摘We studied relationships between stand structure and stand stability according to thinning intensity in an afforested oriental beech stand. Various thinning intensities were applied in sample stands. We sampled eight plots in stands that were lightly thinned, eight plots in heavily thinned stands and eight plots in unthinned stands as a control. Height and diameter distributions of the stands were measured to assess stand structure. We quantified individual tree stability and collective stability. Heavy thinning during the first thinning operation damaged the storied structure of the stand in thicket stage and affected collective structuring ability. While most control plots had multi-storied stands, after light and heavy thinning two-storied structure became more common.Large gaps occurred in the canopy after heavy thinning. On average, nine tree collectives were formed per sampling plot in the untreated stand, seven collectives after thinning in 2008 and four collectives after thinning in 2009. Stable trees accounted for 17 % of trees in control plots, 24 % in lightly thinned plots, and 15 % in heavily thinned plots. Collective stability values were 83 % in control plots, 82 % in lightly thinned plots and 36 % in heavily thinned plots. We conclude that it is necessary to retain collective structuring capacity during thinning operations for sustaining stand stability.
基金part of the Lin~2 Value project(project number 033 L049) supported by the Federal Ministry of Education and Research(BMBF, Bundesministerium fr Bildung und Forschung)
文摘Background： Forest ecosystem functioning is strongly influenced by the absorption of photosynthetically active radiation （APAR）, and therefore, accurate predictions of APAR are critical for many process-based forest growth models. The Lambert-Beer law can be applied to estimate APAR for simple homogeneous canopies composed of one layer, one species, and no canopy gaps. However, the vertical and horizontal structure of forest canopies is rarely homogeneous. Detailed tree-level models can account for this heterogeneity but these often have high input and computational demands and work on finer temporal and spatial resolutions than required by stand-level growth models. The aim of this study was to test a stand-level light absorption model that can estimate APAR by individual species in mixed-species and multi-layered stands with any degree of canopy openness including open-grown trees to closed canopies. Methods： The stand-level model was compared with a detailed tree-level model that has already been tested in mixed-species stands using empirical data. Both models were parameterised for five different forests, including a wide range of species compositions, species proportions, stand densities, crown architectures and canopy structures. Results： The stand-level model performed well in all stands except in the stand where extinction coefficients were unusually variable and it appears unlikely that APAR could be predicted in such stands using （tree- or stand-level） models that do not allow individuals of a given species to have different extinction coefficients, leaf-area density or analogous parameters. Conclusion： This model is parameterised with species-specific information about extinction coefficients and mean crown length, diameter, height and leaf area. It could be used to examine light dynamics in complex canopies and in stand-level growth models.
基金funded by Fundamental Research Funds of Chinese Academy of Forestry(No.CAFYBB2021ZA002).
文摘Diversity-biomass relationships(DBRs)in terrestrial ecosystems tend to vary across spatial scales,but,particularly in hyperdiverse forests,the mechanisms driving these trends remain uncertain.Until now,few have simultaneously investigated the connections between tree species diversity,stand structural diversity,mycorrhizal associations,and ecosystem functioning.In addition,DBRs have only been studied at limited spatial scales,with limited focus on the direct and indirect effects of environmental factors.We addressed these research gaps using a 30-ha forest dynamics plot located in Pu'er City,Southwest China.Through piecewise structural equation models,we quantified the direct effects of tree species diversity(α,β,γ),stand structural diversity,mycorrhizal associations(AM,EcM),and the environmental factors(soil fertility and topography),as well as the indirect effects of the environmental factors on aboveground tree biomass across spatial scales ranging from 400 to 230,400 m^(2).We hypothesized that complex interactions among these factors underpin the variation in DBRs in natural ecosystems across spatial scales.Our results showed that environmental conditions indirectly affected the tree biomass via changes in tree species diversity,and these effects became stronger as the spatial scale increased.At small to moderate spatial scales,environmental factors were more predictive of tree biomass than tree species diversity(or its components);the effects of stand structural diversity on biomass also gradually increased with spatial scale.Conversely,from the intermediate to the largest spatial scales,mycorrhizal associations gradually became the best predictors of DBR dynamics.Our research offers novel empirical evidence demonstrating the importance of environmental conditions,structural diversity,and mycorrhizal associations in shaping cross-scale DBRs.Future comprehensive studies should consider these factors to assess the mechanisms shaping scale-dependent DBRs in complex natural ecosystems.
文摘Stand structure dynamics are considered as major happenings in any forest as a response to environmental changes.However,this important topic is underrepresented in the treeline studies in the Nepal Himalayas.We aimed to investigate site-as well as species-specific changes in morphometric features(basal diameter,crown cover,density,and height)along the elevational gradient across treeline ecotones in response to recent environmental changes.The stand structure characteristics of Abies spectabilis,Pinus wallichiana,and Betula utilis across the treeline ecotone of three study sites in Eastern(Barun),Central(Manang),and Western(Dhorpatan)Nepal were analyzed to elucidate structural heterogeneities.Altogether,eight transects(20 m×(60–250 m))across the treeline ecotone were established.Trees of all life forms,trees(>2 m),saplings(0.5–2 m),and seedlings(<0.5 m),within each transect were enumerated and sampled for the morphometric features and age.Site-specific and species-specific stand structure dynamics were found.The rate of basal area increment was higher in Barun,but the Manang treeline,despite profound regeneration in recent years,had a low annual basal area increment.Moreover,the altitudinal distribution of age and morphometry were not consistent among those ecotones.Furthermore,intra-specific competition was not significant.The site-specific stand structure dynamics explain why treelines do not respond uniformly to increasing temperature.It invokes,in further studies,the incorporation of the tree’s morphometric adaptation traits,phenotypic plasticity,and interactions between species genotype and the environment.
基金This research is related to the project GO NEWTON“Agroforestry Network in Tuscany”,financed by the Tuscany Region through the Measure 16.2 of Rural Development Plan 2014-2020 to promote agroforestry systems by spreading knowledge to farmers and promoting innovation in the Tuscan territory.
文摘On an agrosilvopastoral farm in central Italy where Maremmana cattle graze in Turkey oak forests,we evaluated the impact of different livestock densities on stand structure,tree diversity and natural regeneration in four types of grazed areas based on the grazing regime adopted:calf-grazed,high-intensity-grazed,low-intensity-grazed,ungrazed control.For each area,we set up three permanent circular plots(radius of 15 m)to survey the structural and dasometric characteristics of the overstorey,understorey,and regeneration layer.The results showed that grazing negatively affected the complexity of the forest structure and its potential to regenerate and maintain a high level of biodiversity.The differences in stand structure observed between the grazing areas were closely related to livestock density.The most sensitive components of the system were the understorey and the regeneration layers.Contrarily,the current grazing management did not affect the dominant tree structure or its composition.Our findings identified medium-term monitoring and regeneration management as the two significant aspects to consider when assessing sustainable livestock.New forests can be established by excluding graz-ing for about 20–25 years.
文摘Savanna woodlands in Sudan host great biodiversity, provide a plethora of ecosystem goods and services to local communities, and sustain numerous ecological functions. Although the importance of the Acacia trees in these areas is well known, up-to-date information about these woodlands' diversity is limited and changes in their woody vegetation composition, density, diversity and relative frequency are not monitored over time. This study explored tree diversity and stand stage structure in Nuara Reserved Forest, a typical savanna woodland ecosystem in southeastern Sudan. A total of 638 circular sample plots(1000 m^2 for each) were established using a systematic sampling grid method. The distance between plots was 200 m. In each plot, all living trees with diameter at breast height(DBH) ≥5.00 cm were identified and counted, and their DBH values were recorded. From these data, tree composition, diversity, density and stage structure were assessed. There were 12,259 individual trees representing four species(Acacia seyal, Balanites aegyptiaca, Acacia Senegal and Acacia mellifera) that belong to two families. The dominant species was Acacia seyal. Average tree density was 191 trees/hm^2 and the Shannon-Weiner index for trees diversity was 0.204. Overall, young trees comprised 86.30% of the forest. The state of tree richness and density in the study area was low compared to other similar environments in the region and around the world. We recommended adoption of a proper management system that includes monitoring of woody vegetation diversity in this forest, and management actions to enhance tree diversity and sustain ecosystem services to local communities. In addition to care for the dominant Acacia seyal stands, more attention and conservation should be devoted to reestablishing Acacia senegal and Acacia mellifera trees because of their high ecological and economic values for local communities.
文摘Background:Forest management affects the habitat conditions for many forest-dwelling species.Among them,the capercaillie(Tetrao urogallus)is a rare forest grouse inhabiting old,mature forests.We compared the structure of forest habitat among 9 active and 9 abandoned leks in the Augustow Forest(North-Eastern Poland),within a radius of 1 km of the leks,defined as the Key Areas for the capercaillie in lowland temperate forest.Habitat measurements were conducted on 1779 circular plots.Assessments made on all plots related to 13 habitat variables measured or noted in the field,including stand structure,canopy closure,stand developmental stage,percentage of Scots pine(Pinus sylvestris),soil fertility and soil moisture,the share of undergrowth,the cover of shrubs,the cover of bilberry(Vaccinium sp.),and the presence of certain habitat elements important to the capercaillie.Results:To compare the still-occupied and the abandoned KAs for the capercaillie,a logistic regression model was developed.The variables best explaining differences between these two categories were:the occurrence of undergrowth layers,canopy closure in the second canopy layer,and stand age.According to the model,with the increase of the shrub-layer cover as well as the density of trees,the probability of the presence of the capercaillie decreased.The capercaillie in the area of the Augustow Forest occupy mainly dry and poor,middle-aged,pinedominated forests,with a moderate extent of stand canopy closure and only weakly-developed layers of undergrowth.Conclusions:The filling-in of mature stands with sub-canopy trees and shrubs(the process which is stimulated by climate change and site eutrophication)causes structural changes,which are unfavourable to the capercaillie.This might explain why in the course of the recent decades the capercaillie has abandoned the oldest stands,distinguished by the presence of bigger shares of undergrowth.The capercaillie has shifted to younger stands,which reveal a lesser extent of canopy closure and a more limited development of understorey vegetation.
文摘The artificial pure and mixed Korean pine (Pinus koraiensis) forests were investigated at Dailing Forestry Bureau in Xiaoxing'an mountains from 1990 to 1992. Depending on the distance between the samplings of Korean pine and their neighbor trees, the neighbor tree height, the size of neighbor tree canopy, and dimension of neighbor tree. The forest structure was classified into three types: (1) prowth of a tree in the light (open), (2) Growth of a tree in the canopy gap (Gap), (3)Growth of a tree under broad-leaved tree canopy. The frequeney, height, and age of stem divergence of Korean pine tree were investigated by sampling trees. The temporal and spatial model of the tree growth was applied on basis of the height of stem divergence, ratio of height and DBH, and character of tree stem.The morphology and growth character of Korean pine trees during different development stage were forecasted.
文摘The present study aimed to contribute to the sustainable management of the Ngambe-Ndom-Nyanon communal forest in Cameroon. Thus, an evaluation of the floristic diversity and stand structure of the forest was carried out. By using systematic sampling, a diverse inventory of the plant species was carried out, taking into account the dendrometric measurements of all the species present in the forest (trees, shrubs, herbs). Data were analyzed with Microsoft Excel software to bring out curves and histograms. This software also made it possible to produce tables and also to come up with different diversity indexes. A total of 19,007 individuals from 395 plant species grouped into 99 families were identified in the area. The family Euphorbiaceae was the most represented. Species dominated in this stand were Uapaca guineensis and Pycnanthus angolensis with 9% and 6% of individuals identified. The result of the Shannon index showed that all the strata in the forest are diversified with the highest values in the adult secondary forest (FSA) with indices of 4.74, followed by young secondary forest (FSJ) and the secondary forest (FS) with indice respectively 4.68 and 4.61. The values of the Sorensen index show that 100% of species are common in the young secondary forest (FSJ) and the adult secondary forest (FSA). In the same forest, the FSA and Swamp with FSJ and Swamp have just 15% of species in common respectively. This diversified forest stand projects an inverted J structure, thus testifying to its strong potential for stems of the future. According to the research objectives, some measures were proposed for sustainable management of this forest, such as the reforestation of areas degraded by agricultural activities and the promotion of agroforestry practices by using trees with the high fertilizing potential to improve agricultural yields while preserving the trees in place.
文摘In order to understand the stand structure and growth of phellodendron amurense plantation in limestone mountain, 11-year-old phellodendron amurense plantation with good growth was selected in Da'an Township, Longshan County, Hu’nan Province. A temporary sample plot of 3000m2 was set up to investigate factors such as DBH, tree height, branch height and crown width of each tree. The results showed that the average diameter at breast height, tree height, height to diameter ratio, branch height, crown width, crown height ratio and crown width area of 11-year-old phellodendron amurense plantation with density of 1483-2500 plants /hm2 in limestone mountain area were 8.63cm, 8.74m, 105.4, 4.05m, 2.79m, 0.52 and 6.62m2 respectively;The main factors affecting the height growth of phellodendron amurense are soil fertility and soil physical and chemical properties. The DBH structure of stand approaches normal distribution;The height structure of the stand tree presents typical normal distribution;The above range of stand density had no significant effect on stand growth;The 11-year-old phellodendron amurense forest has obvious differentiation and needs thinning and tending. The 11-year-old phellodendron amurense plantation has entered the beginning stage of middle forest.
基金Part of the work was financed by OTKA support(Ref.No.T 029021)
文摘The paper deals with the stand structure and yield of black locust (Robinia pseudoacacia L.) forests mixed with white (Populus alba L.) in various proportions, partly applying a new methodological approach. The main stand structure and yield factors were determined separately for each species, measured stem by stem, using the volume functions prepared for each species. The ratio of the volumes of the species (A and B) in mixed and in pure stands (based on volume tables) was determined. A close relationship has been found between the ratio by relative total volume and the proportion (by the number of stems) of the species. The relative surplus in the volume of the mixed stands varied between 1.24-1.55 at the age of 16 compared to the control, i.e. the yield of pure stands of the species concerned. The trial has also proven that if two species have a fast initial growth rate and a similar rotation age, they can be planted in mixed stands resulting in mutual advantages.
