Mohadeseh Amiri; Mohammad Shafiezadeh; Mostafa Tarkesh; Seyyed Mostafa Moslemi
Abstract
Introduction: Invasive species are currently the concern of ecologists, conservationists and natural resource managers, and decrease biodiversity due to their rapid spread. These species cause changes in ecological processes, function and structure of community in natural ecosystems. The most obvious ...
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Introduction: Invasive species are currently the concern of ecologists, conservationists and natural resource managers, and decrease biodiversity due to their rapid spread. These species cause changes in ecological processes, function and structure of community in natural ecosystems. The most obvious change in the invaded areas is the reduction of biodiversity and the creation of a pure community of invasive plants. One of the invasive species in our country is Prosopis juliflora, which is important in the field of combat desertification, biological control and stabilization of quicksand dunes in the southern regions of Iran due to its resistance to adverse environmental conditions. Material and methods: In the present study, the efficiency of five discrimination group models (GLM, GBM, ANN, SRE, RF) and a profile model (MAXENT) and their ensemble with the weighted average approach in spatial distribution of this species in Makuran region and determining the most important environmental factors affecting the invasion distribution were investigated. By recording 63 occurrence points and 100 absence points, using climatic, physiographic and human variables as environmental variables, and evaluating the performance of models by Area under Curve (AUC), True Skill Statistics (TSS), Sensitivity and Specificity, the species invasion potential was determined. Results and discussion: Among the single algorithms, according to the threshold-independent and threshold-dependent evaluation criteria, two machine learning techniques, i.e. RF and GBM, predicted the climatic habitat of this invasive species with higher accuracy. Also, the evaluation criteria in the ensemble prediction were higher than the average of all single modelling algorithms. According to the ensemble model, P. juliflora habitats occupy about 15% of the total study area. After generalization of the models to the geographical space, it was found that the invaded areas have spread in a uniform strip on the shores of Oman Sea and Persian Gulf. Evaluation of variable importance indicated that Altitude was the most important independent variable justifying about half of the changes in the ensemble model and has the greatest effect on species distribution. The variable of distance from road was the next important variable. But, aspect was mentioned the least important environmental variable affecting the scattering of the invasion. Based on response curves, the maximum probability of the species presence was observed at the altitude of 50 m above sea level and a distance less than 50 m from the road. Also, the species is most likely to be present, if the temperature in the warmest month and the coldest season of the year is more than 34 and 14 °C, respectively, and the precipitation seasonality is 100-150. Conclusion: It was found that the integrated algorithms in the framework of ensemble modelling showed higher accuracy and the maps derived from potential distribution of species invasion make it possible to restrict and manage the distribution range of invasive species by providing management solution and conserving plans to protect native species. In fact, the results of this study can be used as a basis for subsequent monitoring to prevent further spread of invasive species and to create a balance between the native vegetation protection programs of the region and desertification management measures.
َAmin Mahmoodian Chooplu; Hamid Niknahad
Abstract
Introduction: Determining the response of plant species to environmental gradients is an important issue in the analyses of vegetation communities. The purpose of the present study was to investigate the most important environmental factors shaping the occurrence of Dactylis glomerata in Takab ...
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Introduction: Determining the response of plant species to environmental gradients is an important issue in the analyses of vegetation communities. The purpose of the present study was to investigate the most important environmental factors shaping the occurrence of Dactylis glomerata in Takab rangelands. Material and methods: Eighty four plots (1m2) were placed random-systematically along the azimuth of the studied area. In each plot, the presence of the species was recorded and one soil sample at the depth of 0–20 cm was collected. Some soil physical and chemical properties including soil moisture, texture, pH, electrical conductivity, organic carbon percentage, and the percentage of total nitrogen were measured in the laboratory. Data analysis was performed by Rver.3.0.2 statistical software. The binomial distribution of the Huisman – Olff - Fresco (HOF) function was used to fit the curve of species response to environmental gradients. Results and discussion: The results demonstrated that the altitude variable is the most important environmental factor affecting D. glomerata distribution. Moreover, the optimal ecological amount of this variable for D. glomerata is 2100 m above sea level. After altitude, slope (%), soil organic carbon (%), soil total nitrogen (%), and soil moisture content were the most effective factors on the distribution of D. glomerata. Conclusion : In general, D. glomerata was more distributed in the lower slope of mountainous areas with high soil organic matter and moisture content.
Asghar Mobaraki; Malihe Erfani; Elham Abtin; Farhad Ataie
Volume 16, Issue 4 , January 2019, , Pages 47-62
Abstract
Introduction:
The mugger crocodile is one of the most vulnerable species in the recent IUCN Red list classification. Most of the populations of the species are in decline and extirpation due to the threats caused by human activities. Nowadays, species distribution modeling plays an essential role in ...
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Introduction:
The mugger crocodile is one of the most vulnerable species in the recent IUCN Red list classification. Most of the populations of the species are in decline and extirpation due to the threats caused by human activities. Nowadays, species distribution modeling plays an essential role in their conservational biology and ecological studies. However, considering the lack of such data on the mugger crocodile in Iran, this study was conducted to evaluate the suitability of the crocodile habitats in the country.
Material and methods:
The watersheds of the Sarbaz and Kaju rivers in the Makran area are the westernmost part of the distribution range of the mugger crocodile, located in the southern part of Sistan and Baluchestan Province. Modeling the suitability of the crocodile habitats in this area was conducted using maximum entropy. The environmental variables of elevation, Normalized Difference Vegetation Index (NDVI), temperature, rainfall, and the distance from urban and rural settlements, roads, and rivers were included in the study. To eliminate high correlation variables (<0.70), Pearson correlation test was used. By using Moran’s I, the lack of spatial autocorrelation between the presence data of the species was assured. Sensitivity and evaluation of the relative importance of each variable were done by the percent contribution and permutation importance of each variable. Also, the response curves of the variables and the jackknife test were calculated. Maximum training sensitivity plus specificity (MTSS) and equal training sensitivity and specificity (ETSS) were used as thresholds to classify the suitable regions.
Results and discussion:
The amount of AUC was more than 0.8, indicating excellent performance of the model. Based on the percent of contribution and permutation importance of each variable and the results of the jackknife test, the distance from the rivers, temperature and elevation were the most important variables. The threshold values of ETSS and MTSS were 0.52 and 0.18, respectively. According to the thresholds, the suitability of the habitat was classified into two suitable and unsuitable classes with an area of 312 and 1629 km2, respectively. Comparison of the thresholds in classification showed that ETSS is more accurate. Considering that the major part of the suitable habitats is located outside of the Gandou Protected Area, revision of the borders of the protected area is proposed as a suggestion for management for the conservation of this species. The study of the effect of dams on the crocodile habitat suitability in the area showed that dams increased the habitat suitability, but their negative impacts, like the loss of nesting sites, should be noted. Also, the fragmentation of the suitable habitats was obvious in the study, and considering the migration behavior of the species, corridors should also be included in conservation plans.
Conclusion:
Distance from the river, as the main variable determining the suitability of the mugger crocodile habitat, is affected by climatic fluctuations and the water amount. Conflicts between the crocodiles and local people for resources (water and food) as well as the immigration of crocodiles between separate habitat patches would be more severe in the warm seasons and drought situations. Therefore, in addition to revising the area of the protected area and conservation of the habitats, increasing species monitoring, public education and participation of local communities in the conservation actions would be essential.
Shahram Jafarnia; Seyed Mohammad Hojjati; Yahya Kooch
Volume 9, Issue 4 , July 2012
Abstract
In this study, a statistical survey of the mangrove habitat of Qeshm Island was carried out for better public recognition and its structure and the vegetative mangrove forest components as well as their relationship to the physical and chemical characteristics of soil and water were examined. In order ...
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In this study, a statistical survey of the mangrove habitat of Qeshm Island was carried out for better public recognition and its structure and the vegetative mangrove forest components as well as their relationship to the physical and chemical characteristics of soil and water were examined. In order to do this, six transects were chosen in three regions of mangrove with closed, medium, and low canopy density, respectively. In 60 sample plots, the vegetative parameters, tree density per hectare, canopy percentage, aerial root density and height, regeneration, and tree height were measured per unit area. In the center of each sample, fifteen physical and chemical soil and water parameters were measured. Finally, the relationship between the various vegetative characteristics at different cover densities and soil-water characteristic levels was studied using principal component analysis (PCA). The results of PCA on fifteen recorded environmental variables showed that the first and second principal components explain 86.63% and 13.36% of the evaluated parameter changes, respectively. Generally, the soil organic matter and clay percentage as well as the sodium level in areas with high densities of cover are considered to be factors impacting on the vegetative characteristics of Hara trees.
