Distribution Of Trees Research Articles

Selectivity of Perch Diameter by Green Anole (Anolis carolinensis) for Trapping in Ogasawara

In the Ogasawara Islands adhesive traps are the primary means of controlling non-native Anolis carolinensis. If the types of tree trunks most frequently used by this lizard are identified, trapping efficiency can be improved by concentrating traps at such points. To analyze selectivity by trunk diameter, the diameters of 270 tree trunks used by the lizards and 1,024 tree trunks in the study area were measured. The analysis indicated the lizards avoided trunks of 1 cm or less in diameter. On the other hand, trunks with diameters over 2 cm appeared to be used randomly, regardless of diameter size. The diameter class distribution of trees varies by region and by forest. The range of tree trunk diameters commonly used by lizards is thus expected to vary by location. It would be advantageous to develop a capture technique that is effective for trunks and branches of various diameters.

The Dynamics of Tropical Forests of Western Ghats, Kerala, India, with Special Reference to Growth, Structure, Species Distribution and Fragmentation

The tropical forest is always changing gradually through interaction of the living ecosystem and the environment; though seems to be static at a given period of time. These changes can be accelerated by anthropogenic effects and the resultant formations are normally unpredictable, but definitely towards the degraded succession stages. The stratification concept in forest is based on difference in tree heights. This difference in heights may be due to site qualities, geographical features, but more prominent due to intrinsic nature of species. The distribution of trees by diameter classes is basic to study tropical forests and is the most accessible and studied information. It is rarely analyzed in detail; in particular, the influence of soils, topography, and altitude has not been studied systematically. It makes possible the assessment of the effects of the main environmental factors on forest architecture. The management and modification of tropical rainforest environments, though aimed at controlling dynamic process within a human life span, must take account of the damage of long term regression or face ultimate catastrophe. The forest dynamics in tropical forest ecosystems are highlighted in the paper.  One liner: The forest dynamics with respect to growth, stratification and floristics of tropical forests are highlighted.

New insights into the formation of biodiversity hotspots of the Kenyan flora

AbstractAimThis study aimed to investigate the distribution patterns of plant diversity in Kenya, how climatic fluctuations and orogeny shaped them, and the formation of its β‐diversity.LocationKenya, East Africa.TaxonAngiosperms.MethodsWe quantified patterns of turnover and nestedness components of phylogenetic β‐diversity for angiosperm species among neighbouring sites using a well‐resolved phylogenetic tree and extensive distribution records from public databases and other published sources. We applied clustering methods to delineate biota based on pairwise similarities among multiple sites and used a random assembly null model to assess the effects of species abundance distribution on phylogenetic β‐diversity.ResultsThe phylogenetic turnover of the Kenyan flora, intersecting with the biodiversity hotspots Eastern Afromontane, Coastal Forests of Eastern Africa, and Horn of Africa, shows a non‐monotonic pattern along a latitudinal gradient that is strongly structured into volcanic and coastal areas. The other areas are mainly dominated by phylogenetic nestedness, even in the eastern part of the equatorial region parallel to the volcanic area. Phylogenetic diversity and phylogenetic structure analyses explain the mechanism of the observed phylogenetic turnover and nestedness patterns. We identified five phytogeographical regions in Kenya: the Mandera, Turkana, Volcanic, Pan Coastal and West Highland Regions.ConclusionsVariations in turnover gradient and coexistence are highly dependent on the regional biogeographical history resulting from climatic fluctuations and long‐lasting orogeny, which jointly shaped the biodiversity patterns of the Kenyan flora. The nestedness component dominated climatically unstable regions and is presumed to have been caused by heavy local species extinction and recolonization from the Volcanic Region. The high turnover component in climatically stable regions may have preserved old lineages and the prevalence of endemic species within narrow ranges.

Biomass distribution, allocation and growth efficiency in European beech trees of different ages in pure even-aged stands in northeast France

Abstract Determination of the biomass and biomass increment of trees in managed stands is a pre-requisite for estimating the carbon stocks and fluxes, in order to adapt the forests to new climatic requirements, which impose to maximize the CO2 retained by forests. Tree biomass and biomass increment equations were formerly developed in two young experimental beech stands in the Hesse forest (NE France). To extend such a study to beech stands of different age classes, it was necessary to build biomass and biomass increment equations that could be used for any age, called generalized biomass equations. For that, trees were sampled in plots covering a large age range in Hesse forest, and in each plot several trees were chosen to represent the different social classes. Compatible biomass and biomass increment equations for the different tree compartments and their combination in above and belowground tree parts were developed and fitted, allowing the analysis of the variations of the biomass distribution and allocation with tree age. Stem growth efficiency (stem growth per unit of leaf area) appeared dependent on tree age and tree social status. The biomass and biomass increment equations established for beech allow the estimation of the biomass and carbon stocks and fluxes (NPP) for the even-aged beech stands of the Hesse forest, whatever their age. These equations could also be used to analyze the effects of silvicultural treatments on the biomass and carbon stocks and fluxes of beech stands, using the available stand growth and yield models of beech.

Enhancing forest resilience: Advances in Ontario’s wild tree seed transfer policy

Climate is a critical driver in shaping patterns of tree distribution and productivity in Canadian forests. Canada’s climate is changing and, as a result, tree populations may become maladapted to the climate at their current growing locations. In 2020, Ontario updated its tree seed transfer policy to respond to the evolving natural, operational, scientific, and policy environments, including a changing climate. Collaboration among federal and provincial science, operations, and policy staff was essential to update the policy, which involved a custom climate similarity analysis, a related assessment of critical seed transfer distances, various engagement efforts to assess end-user receptivity, and the development of an online interactive tool to allow users to explore seed transfer options under climate change. Here we describe several factors considered during the policy update, major steps in the update process, and highlights of the outcome. The intent of this effort is to support other jurisdictions considering similar changes and to emphasize the need for a changing culture in seed procurement and management.

Urban Tree Classification Based on Object-Oriented Approach and Random Forest Algorithm Using Unmanned Aerial Vehicle (UAV) Multispectral Imagery

Timely and accurate information on the spatial distribution of urban trees is critical for sustainable urban development, management and planning. Compared with satellite-based remote sensing, Unmanned Aerial Vehicle (UAV) remote sensing has a higher spatial and temporal resolution, which provides a new method for the accurate identification of urban trees. In this study, we aim to establish an efficient and practical method for urban tree identification by combining an object-oriented approach and a random forest algorithm using UAV multispectral images. Firstly, the image was segmented by a multi-scale segmentation algorithm based on the scale determined by the Estimation of Scale Parameter 2 (ESP2) tool and visual discrimination. Secondly, spectral features, index features, texture features and geometric features were combined to form schemes S1–S8, and S9, consisting of features selected by the recursive feature elimination (RFE) method. Finally, the classification of urban trees was performed based on the nine schemes using the random forest (RF), support vector machine (SVM) and k-nearest neighbor (KNN) classifiers, respectively. The results show that the RF classifier performs better than SVM and KNN, and the RF achieves the highest accuracy in S9, with an overall accuracy (OA) of 91.89% and a Kappa coefficient (Kappa) of 0.91. This study reveals that geometric features have a negative impact on classification, and the other three types have a positive impact. The feature importance ranking map shows that spectral features are the most important type of features, followed by index features, texture features and geometric features. Most tree species have a high classification accuracy, but the accuracy of Camphor and Cinnamomum Japonicum is much lower than that of other tree species, suggesting that the features selected in this study cannot accurately distinguish these two tree species, so it is necessary to add features such as height in the future to improve the accuracy. This study illustrates that the combination of an object-oriented approach and the RF classifier based on UAV multispectral images provides an efficient and powerful method for urban tree classification.

Distribution models calibrated with independent field data predict two million ancient and veteran trees in England.

Large, citizen-science species databases are powerful resources for predictive species distribution modeling (SDM), yet they are often subject to sampling bias. Many methods have been proposed to correct for this, but there exists little consensus as to which is most effective, not least because the true value of model predictions is hard to evaluate without extensive independent field sampling. We present here a nationwide, independent field validation of distribution models of ancient and veteran trees, a group of organisms of high conservation importance, built using a large and internationally unique citizen-science database: the Ancient Tree Inventory (ATI). This validation exercise presents an opportunity to test the performance of different methods of correcting for sampling bias, in the search for the best possible prediction of ancient and veteran tree distributions in England. We fitted a variety of distribution models of ancient and veteran tree records in England in relation to environmental predictors and applied different bias correction methods, including spatial filtering, background manipulation, the use of bias files, and, finally, zero-inflated (ZI) regression models, a new method with great potential to investigate and remove sampling bias in species data. We then collected new independent field data through systematic surveys of 52 randomly selected 1-km2 grid squares across England to obtain abundance estimates of ancient and veteran trees. Calibration of the distribution models against the field data suggests that there are around eight to 10 times as many ancient and veteran trees present in England than the records currently suggest, with estimates ranging from 1.7 to 2.1 million trees compared to the 200,000 currently recorded in the ATI. The most successful bias correction method was systematic sampling of occurrence records, although the ZI models also performed well, significantly predicting field observations and highlighting both likely causes of undersampling and areas of the country in which many unrecorded trees are likely to be found. Our findings provide the first robust nationwide estimate of ancient and veteran tree abundance and demonstrate the enormous potential for distribution modeling based on citizen-science data combined with independent field validation to inform conservation planning.

Patterns and drivers of recent land cover change on two trailing-edge forest landscapes

Climate change is altering the distribution of woody plants by influencing demographic processes and modifying disturbance regimes. Trailing-edge forests may be particularly vulnerable to these effects because they exist at warm, dry margins of tree distributions. To better understand recent climate-driven changes in trailing-edge forests, we used Landsat time series and 1558 field reference plots to develop annual land cover maps from 1985 to 2020 in two large, biodiverse landscapes in central Arizona, USA. We then combined annual land cover maps with tree ring records and spatial data describing interannual climate, terrain, bark beetle (Curculionidae: Scolytinae) activity, wildfire, and harvest to quantify drivers of forest change. Throughout the two landscapes, forest extent declined by 0.3 % and 0.8 % from 1985 to 2020. However, considerable variation occurred within the study period, with abrupt (ca. 1–2 years) declines in forest extent followed by gradual (ca. 10 years) recovery on each landscape. Pinyon-juniper (Pinus edulis, Pinus monophylla, and/or Juniperus spp.) cover increased from 1985 to ca. 2000 but declined after 2000, a period of extreme drought and regional tree die-off. In contrast, pine-oak (Pinus ponderosa and Quercus spp.) cover increased from 2000 to 2020, primarily due to declines in ponderosa pine and mixed conifer cover over the same period. Wildfire was a key driver of transitions from forest to non-forest cover in our study area, with the occurrence of multiple compounded drought years playing an important role in unburned areas. By driving transitions to alternative forest types or non-forest cover, disturbance and drought will increasingly shape forest dynamics and ecosystem transformations throughout the southwestern US.

Investigation of electrical tree stress using colour techniques

Treeing is one of the severe problems which cause the deterioration and breakdown of electrical insulation materials. Different approaches have been used to characterise this phenomenon, from experiments to analysis. The results of both methods were criticised for their dependence on the assumptions and applied conditions. In this work, the role of colours in understanding the characteristics of electrical treeing in composite insulation was employed. The relationship between the induced strain, associated with the electrical tree, and the change of colour parameters, represented by hue, saturation, and value indicators, was presented. The images were created by relative retardation orthogonal components of the polarised white light used to illuminate the specimens in the microscope. An image-editing software was used to analyse the tree colours, whereas the MATLAB program was written to determine the colour mapping of examined image. The variation of each colour parameter was linked with the tree distribution. It was then introduced as an indicator of stress at each examined point. Therefore, the contribution of the present paper is summarised as an introduction of a new tool to characterise stress in insulation materials by converting a treed image into a numerical array of data without the need to follow a complex mathematical procedure. Finally, this paper can better assess the treeing phenomenon by correlating the direction of tree growth to the rate of change for each colour parameter in that direction.

Flexible drought deciduousness in a neotropical understory herb.

PremiseAdaptive divergence across environmental gradients is a key driver of speciation. Precipitation seasonality gradients are common in the tropics, yet drought adaptation is nearly unexplored in neotropical understory herbs. Here, we examined two recently diverged neotropical spiral gingers, one adapted to seasonal drought and one reliant on perennial water, to uncover the basis of drought adaptation.MethodsWe combined ecophysiological trait measurements in the field and greenhouse with experimental and observational assessments of real‐time drought response to determine how Costus villosissimus (Costaceae) differs from C. allenii to achieve drought adaptation.ResultsWe found that drought‐adapted C. villosissimus has several characteristics indicating flexible dehydration avoidance via semi‐drought‐deciduousness and a fast economic strategy. Although the two species do not differ in water‐use efficiency, C. villosissimus has a more rapid growth rate, lower leaf mass per area, lower stem density, higher leaf nitrogen, and a strong trend of greater light‐saturated photosynthetic rates. These fast economic strategy traits align with both field‐based observations and experimental dry‐down results. During drought, C. villosissimus displays facultative drought‐deciduousness, losing lower leaves during the dry season and rapidly growing new leaves in the wet season.ConclusionsWe revealed a drought adaptation strategy that has not, to our knowledge, previously been documented in tropical herbs. This divergent drought adaptation evolved recently and is an important component of reproductive isolation between C. villosissimus and C. allenii, indicating that adaptive shifts to survive seasonal drought may be an underappreciated axis of neotropical understory plant diversification.

Potential impacts of the invasive Agrilus planipennis on various demographics in Winnipeg, Canada

The hardiness of Fraxinus spp. (ash) makes them a common municipal tree in adverse growing conditions. In Winnipeg, Manitoba, the impacts of Dutch elm disease resulted in increased reliance on Fraxinus, resulting in a monoculture of Fraxinus across the city. Emerald ash borer (EAB) (Agrilus planipennis) poses substantial risk to Winnipeg's urban forest, forecasted to result in the total loss of Fraxinus in Winnipeg. With a lens of distributional equity, this study examines associations between Fraxinus abundance and distribution and human population demographics at the Dissemination Area and Census Tract levels. There are positive correlations with Fraxinus abundance and distribution and median household income and proportion of the population that self-identifies as a visible minority. Population density was positively associated with Fraxinus abundance and distribution at the Census Tract level. These results underscore the importance of assessing the distribution of vulnerable trees as a component of green equity. Using information on urban forest management in response to EAB, potential issues and possible opportunities are discussed.

Importance of climate‐induced tree species composition changes in forecasting the amount of reachable habitat for forest birds

AbstractAimBird and tree species distributions will shift along with future climatic conditions through direct effects related to species responses to bioclimatic variables. In addition, tree species composition changes should indirectly drive changes in forest bird habitats. Here, we predicted the effects of climate changes on the amount of reachable habitat for forest birds and teased apart the role of the indirect effects.LocationFrance.MethodsWe projected tree and bird species distributions (2020 and 2050) using generalized additive models which accounted for climatic conditions at a large scale (France) and local environmental conditions at regional scale. The projections combined two scenarios of climate changes (RCP 2.6 and 8.5) and two scenarios of forest management (increase in either deciduous or coniferous stands). We modelled the amount of reachable habitat with landscape graphs and the equivalent connectivity index (EC) for five birds associated to the main forest types of the study area. To differentiate the sources of EC change between 2020 and 2050, we compared two future landscape graphs including only the indirect effect, or the direct and indirect effects of climate changes.ResultsFor birds with low and intermediate thermal maxima, climate‐based distributions were nearly stable over time (absence of direct effects), EC change was only attributed to indirect effects. In contrast, for bird species with high thermal maximum, EC change was mostly driven by direct effects (more favourable climatic conditions) and little by indirect effects.Main conclusionsUsing an innovative modelling framework that bind species distribution and connectivity models with climate and land use changes in forest, we showed that EC dynamics could be completely due to climate‐driven changes in tree species composition. Our results highlight the importance of accounting for the indirect effects of climate changes, especially in forests where major shifts in tree species composition are expected.

Branching pattern of flexible trees for environmental load mitigation

Wind-induced stress is the primary mechanical cause of tree failures. Among different factors, the branching mechanism plays a central role in the stress distribution and stability of trees in windstorms. A recent study showed that Leonardo da Vinci’s original observation, stating that the total cross section of branches conserved across branching nodes is the optimal configuration for resisting wind-induced damage in rigid trees, is correct. However, the breaking risk and the optimal branching pattern of trees are also a function of their reconfiguration capabilities and the processes they employ to mitigate high wind-induced stress hotspots. In this study, using a numerical model of rigid and flexible branched trees, we explore the role of flexibility and branching patterns of trees in their reconfiguration and stress mitigation capabilities. We identify the robust optimal branching mechanism for an extensive range of tree flexibility. Our results show that the probability of a tree breaking at each branching level from the stem to terminal foliage strongly depends on the cross section changes in the branching nodes, the overall tree geometry, and the level of tree flexibility. Three response categories have been identified: the stress concentration in the main trunk, the uniform stress level through the tree’s height, and substantial stress localization in the terminal branches. The reconfigurability of the tree determines the dominant response mode. The results suggest a very similar optimal branching law for both flexible and rigid trees wherein uniform stress distribution occurs throughout the tree’s height. An exception is the very flexible branched plants in which the optimal branching pattern deviates from this prediction and is strongly affected by the reconfigurability of the tree.

Trunk detection in tree crops using RGB-D images for structure-based ICM-SLAM

Agricultural environments with tree plantations usually present a regular structure that can be used by SLAM systems to improve self-location, and therefore, facilitate the autonomous navigation. In this context, tree trunks are natural landmarks that can be used to incorporate the environment structure into the problem modeling. This article presents a trunk detector solely based on RGB-D data obtained from a frontal-view stereo camera, and a SLAM system that incorporates the regular tree distribution of these crops. The trunk detector can be adapted to similar agricultural environments because its parameters have specific geometric meanings, which differentiates it from black box-type procedures. The structure-based SLAM system has theoretical and practical advantages over the well-known SLAM procedures in the mentioned context. This proposal can be executed on-line and is experimentally tested with databases obtained from a challenging agricultural environment. Results show a good performance and robustness when the database is spatially or temporally subsampled, even under adverse lighting conditions.

THE POPULATION AND DISTRIBUTION OF AGARWOOD PRODUCING TREE (AQUILARIA MALACCENSIS) IN RIAU PROVINCE

YULIZAH, RAHAJOE, J. S., FEFIRENTA, A. D. & NUGROHO, A. D. 2022. The population and distribution of agarwood producing tree (Aquilaria malaccensis) in Riau Province. Reinwardtia 21(1): 1–11. — Riau Province is one of the largest agarwood producers and supplier of Aquilaria malaccensis species in Indonesia, based on the data of trade quota that was issued by the Ministry of Environment and Forestry in 2018. The quota data will be used for monitoring the sustainability of the population agarwood producing trees in the wild. The aimed of the study were to determine the natural population distribution and habitat preference of wild agarwood-producing trees in Riau Province. The agarwood population census carried out by making random plots in the study sites, soil moisture, soil pH, temperature and the humidity recorded, and the macronutrients data also used to support the habitat preferences for the agarwood producing taxa tree. Seven locations of agarwood producing trees were selected for the study sites including Taman Hutan Raya (TAHURA: Forest Park Garden) Sultan Syarif Hasyim (SSH), three community forests in Siak Sri Indapura District (Gosib, Perincit and Dosan), and three community forests in Bengkalis District (Langkat, Pangkalan Jambi, and Duri Km 13). The density of agarwood producing trees in TAHURA SSH recorded for about 38 plants ha-1, with an average diameter distribution was 15 cm, and the tree height was 9.51 m. Perincit data showed the highest density, with 8.13 plants ha-1 with an average distribution of tree diameters was recorded for 20.8 cm and the tree height was 9.11 m. While the lowest tree density was recorded for 0.58 plant ha-1 in Gosib, the average diameter and tree height were recorded for 40.15 cm and 14.70 m, respectively. Environmental parameters and soil chemistry were the main factors to support the tree growth of agarwood. The result was necessary for the conservation program of A. Malaccensis, and support data for providing potential seeds source and seedling. The nutrient content preference from the finding of this research will also be used as the necessary information of the needs of nutrient content in the natural habitat of agarwood plantations.

Changes in tree layer and altitudinal distribution of herbaceous species in temperate old-growth forests over 30 years

Temperate forest ecosystems, including old-growth fragments, are subject to increasing pressures, both from biotic and abiotic factors. Frequent disturbance events, rising mean annual temperatures and longer-lasting droughts are causing changes in tree species composition, probably shifting the altitudinal distribution of herbaceous species as well. Our goal was to examine whether such shifts can be observed even in old-growth temperate forests, and if the changes in the species composition and spatial distribution of trees is reflected in the herbaceous layer. Our study was based on a survey of several old-growth forests from the 1970s that was repeated after 30 years. Using spatial point pattern methods and generalized linear mixed effect models, repeated measurements of mapped phytosociological relevés and detailed maps of tree positions from two survey periods allowed us to examine how the species composition of the herb layer and the spatial distribution of trees ≥ 10 cm DBH (diameter at breast height) changed over 30 years. On most of the studied sites, the total number of trees declined and the proportion of broadleaves increased between the two surveys. Analyses of tree spatial distribution showed a general shift from a regular spatial distribution in the 1970s to a clustered spatial distribution of trees in the 2000s. In the 2000s, herbaceous species showed an upwards shift in their distribution compared to the 1970s, even after accounting for the effect of changing tree spatial distributions in both survey periods. These effects could be an outcome of warmer and drier weather conditions during the past decades. Further investigation is needed to examine whether this trend is related to changes in climatic conditions.

Assessing Sustainable Green Areas based on Ecological Niche Role in Urban Education Institute

Green areas are so critical in urban communities for making environments healthier and more livable. The objectives of this study were to assess sustainable green areas and to study their ecological niches in an urban education institute. Rajamangala University of Technology Isan (RMUTI) at Nakhonratchasima City Municipality (NCM) was selected as the study area. The spatial assessment of sustainable green areas used guidelines of the policy action plan for sustainable urban green area management by the Office of Natural Resources and Environmental Policy and Planning (ONEP) and then sustainable green areas were analyzed by the Ecological Niche Model (ENM) in Biomapper to check the distribution and durability of the existing trees to the current environment.The study found that sustainable green area in RMUTI at NCM is about 54.23% with 1,176 trees, which is in accordance with the policy action plan of ONEP that has suggested at least 30% of the land parcel being the sustainable green area in urban education institute. In the area of RMUTI, we mostly found type 2 (multiple-use) and type 3 (environmental preservation), respectively. Such two-green type was not only confirmed by assessing the highest accuracy of ENM (AVI and CVI =1.00) but they also preferred niche factors: annual precipitation for type 2 and annual temperature for type 3. Consequently, tree distribution in type 2 and 3 will have more ability of highly sustainable green areas than other green types. These results are explicitly showed that if green type has many distributions of studied trees, it will be a possibility of sustainable green areas. Furthermore, knowledge of ENM will help to plan the suitable tree species to right green areas and their current environment. Consequently, this study can be an example for assessing sustainable green areas-based ENM and implementing in other urban education institutes.

Sustainable Oil Palm Resource Assessment Based on an Enhanced Deep Learning Method

Knowledge of the number and distribution of oil palm trees during the crop cycle is vital for sustainable management and predicting yields. The accuracy of the conventional image processing method is limited for the hand-crafted feature extraction method and the overfitting problem occurs due to the insufficient dataset. We propose a modification of the Faster Region-based Convolutional Neural Network (FRCNN) for palm tree detection to reduce the overfitting problem and improve the detection accuracy. The enhanced FRCNN (EFRCNN) leads to improved performance for detecting objects (in the same image) when they are of multiple sizes by using a feature concatenation method. Transfer learning based on a ResNet50 model is used to extract the features of the input image. High-resolution images of oil palm trees from a drone are used to form the data set, containing mature, young, and mixed oil palm tree regions. We train and test the EFRCNN, the FRCNN, a CNN used recently for oil palm image detection, and two standard methods, namely, the support vector machine (SVM) and template matching (TM). The results reveal an overall accuracy of ≥96.8% for the EFRCNN on the three test sets. The accuracy is higher than the CNN and FRCNN and substantially higher than SVM and TM. For large-scale plantations, the accuracy improvement is significant. This research provides a method for automatically counting the oil palm trees in large-scale plantations.

A Simple Optical Sensor Based on Multimodal Interference Superimposed on Additive Manufacturing for Diameter Measurement.

In many areas, the analysis of a cylindrical structure is necessary, and a form to analyze it is by evaluating the diameter changes. Some areas can be cited: pipelines for oil or gas distribution and radial growth of trees whose diameter changes are directly related to irrigation and the radial expansion since it depends on the water soil deficit. For some species, these radial variations can change in around 5 mm. This paper proposes and experimentally investigates a sensor based on a core diameter mismatch technique for diameter changes measurement. The sensor structure is a combination of a cylindrical piece developed using a 3D printer and a Mach–Zehnder interferometer. The pieces were developed to assist in monitoring the diameter variation. It is formed by splicing an uncoated short section of MMF (Multimode Fiber) between two standard SMFs (Singlemode Fibers) called SMF-MMF-SMF (SMS), where the MMF length is 15 mm. The work is divided into two main parts. Firstly, the sensor was fixed at two points on the first developed piece, and the diameter reduction caused dips or peaks shift of the transmittance spectrum due to curvature and strain influence. The fixation point (FP) distances used are: 5 mm, 10 mm, and 15 mm. Finally, the setup with the best sensitivity was chosen, from first results, to develop another test with an optimization. This optimization is performed in the printed piece where two supports are created so that only the strain influences the sensor. The results showed good sensitivity, reasonable dynamic range, and easy setup reproduction. Therefore, the sensor could be used for diameter variation measurement for proposed applications.

Density effect on decline of Cedrus atlantica Manetti Ex Carriere in national park of Theniet El Had, Algeria

This study focuses on the study of the causal factors of Atlas cedar decline in the Theniet el Had national park, once classified as the first park in Algeria and the most beautiful cedar forest in northern Africa. Although severalstudies have been done on the causative agent of decline, none of them have confirmed the predisposing factors, thus weakening its vigor. Therefore, in this study, the search for possible relationship between dieback and ecological, dendrometric characteristics as well as the spatial distribution of trees were taken into consideration. 40 concentric circular plots of 200, 400, 500 and 1,000 m² were installed in the northern part of the park for dendrometric and edaphic surveys, in addition to rectangular plots of 200 m2 installed in the center of the concentric plots were measured of distance between trees and of the four radii of the crown. The results obtained showed that the circumference in the reduced areas (the circular plots of 200m²) declined significantly. The spatial distribution of the trees, schematized by the AutoCAD software, was chaotic and the crowns showed deterioration influenced by their overlapping. In 76% of the rectangular plots, the maximum area of the crowns had an overlap of more than 90%. The application of Schütz's inter-individual competition index also indicated that competition between trees was very important. This situation only explains the chaotic distribution of the trees, due to the lack of forestry work, imposes a competition between the trees causing, thus, the weakening of their vigor. Therefore, the establishment of a short- and longterm Atlas cedar decline management plan is of high recommended importance, in which adjusting the spatial distribution can promote the future strength and vitality of Atlas cedars.