Showing 5 results for Environmental Factors
Sh. Shokrollahi, H. R. Moradi, Gh. A. Dianati Tilaki,
Volume 3, Issue 7 (6-2014)
Abstract
The aim of the present study was investigating some ecological factors in the habitats of four species and determining the most significant variables affecting the presence and distribution of these species. Study area, which was about 4600 ha, was located at Polur, Mazandaran province. For this purpose, after primary survey and selection of main plant species, 3 transects 150 meter in length were laid down systematically and 10 random plots (1m×1m) were established in each vegetation type. The investigated plant species included Festuca ovina, Astragalus gossypinus, Poa bulbosa and Dactylis glomerata.Then, 3 soil samplings were taken from 0-30 cm in starting, mean and ending points of each transect. Soil factors such as N, P, organic material, pH, EC and texture were determined. The software SHAZAM 10 package was used to find the logical relationship between plant species and environmental variables. The statistical pattern for this research was based on qualitative function. Therefore, logic function was evaluated. The results showed that soil acidity and nitrogen were the main limiting factors affecting the presence and absence probability of Festuca ovina and Poa bulbosa but, in the habitats of Astragalus depressus, organic matter and electrical conductivity were the most important variables affecting the presence and absence probability of this species. Elevation and nitrogen were the main limiting factors in the habitats of Dactylis glomerata.
Z. Jafarian, M. Kargar,
Volume 6, Issue 1 (6-2017)
Abstract
For this study, Polour rangelands were chosen with an area of about 2017 ha in Mazandaran province. The purpose of this study was prediction of dominant species of the rangeland using random forest (RF) and boosting regression trees (BRT) models in the study area. Equal random sampling of vegetation and soil was carried out. 12 work units were obtained in the region that climatic, topography and soil factors were measured at each sampling unit. Five dominant species in the area were Astragalus ochrodeucus, Ferula gumosa, Thymus kotschyanus, Onobrychis cornata and Agropyron repens. The Ten-fold method was used to evaluate the models in the package (caret). Also the statistical coefficients AUC, Kappa and TSS were used for evaluating the model prediction.The results showed that in the RF model of variables K and CaCO3, the presence of the plant species had the highest importance. Also in BRT model, the silt and aspect had the most importance in the model. The results of the function of the models RF and BRT showed that the highest AUC in the BRT model was related to the species Agropyron repens for 0.76 and in the RF model, it was related to the species Onobrychis cornata. The proposed models RF and BRT can be used for introduction of suitable species in range improvement programs.
Abdolah Salehi Ardali, Mohammad Reza Vahabi, Mostafa Tarkesh Isfahani, Saeid Pourmanafi, Elham Ghehsareh Ardestani, Hamid Reza Farhang,
Volume 6, Issue 3 (12-2017)
Abstract
Vegetation is the most important factor influencing the sustainability of rangeland ecosystems. Therefore, it is important to understand the environmental factors and their effect on vegetation and restoration of rangeland ecosystems. The aim of this study was to identify factors influencing on Gundelia tournefortii L. distribution. Accordingly, the information of Gundelia tournefortii L. was determined in six habitats in Isfahan province. Random- systematic sampling was conducted to calculate canopy and density of the species. In each rangeland place, climate, physiography and soil factors were identified. RDA ordination analysis using CANOCO software was used to investigate the vegetation relationship with environmental factors. In the cluster analysis and RDA ordination analysis, six main habitats of the species were classified into three groups. The first axis of ordination showed a very strong correlation with canopy cover and density and the second axis showed a very strong correlation with soil depth. According to study of the habitats of this species, annual precipitation about 250 to 500 mm, altitude 2300 to 2500 meter, slope about 10 to 40 percent and average of annual temperature about 10 ̊C to 12 ̊C are appropriate for presence of this species.
Javad Mirzaei, Mostafa Naderi, Asghar Mosleh Arani, Mehdi Heidari, Aliakbar Jaafarzadeh,
Volume 6, Issue 4 (3-2018)
Abstract
The effects of some environmental factors on distribution of Lonicera nummulariifolia were studied in Manesht-Ghalarang protected area in Ilam Province. Vegetation, physiographic characteristics and soil (texture, Ph, EC, SP, Cao, OC, P, N, K and bulk density, depth of 0-30 cm) was investigated in 125 plots. Totally, 166 plant species belong to 121 genus and 44 families were identified in this study area. The families of Asteraceae (21 species), Labiateae (20), Poaceae (15 species), Papilionaceae (13 species) had the highest number of plant species. Multi-variant analysis showed that Lonicera nummulariifolia had positive relationship with organic matter, nitrogen, altitude and formation of Asmary and negative relationship with lime, EC, clay and silt. Also, Amygdalus elaeagnifolia, Cotoneaster luristanica, Daphne mucronata, Rhamnus Pallasii, and Cerasus microcarpa has the most ecological similarity with L. nummulariifolia. The results can be a useful for the development of L. nummulariifolia in areas with similar ecological conditions.
F. Rafiee, M. R. Kamjoo, H. Ejtehadi, M. Farzam,
Volume 12, Issue 2 (9-2023)
Abstract
Safe sites are microhabitats that provide the basic requirements for seed dormancy breaking, germination, and seedling establishment. They reduce threats from seed predators, herbivores, pests, and competitors. We identified and assessed living and non-living safe sites in the rocky outcrops and their effects on species diversity at six sites along a rainfall gradient in the north of Iran. Four dominant plant species were considered as living safe sites, but crevices and rocks were attributed as the non-living safe sites. Ten transects of 10 meters long were established at each site, along the rainfall gradient. Plant abundance and canopy cover were measured for all species along the transects. Soil physiochemical properties, moisture and temperature were recorded at the safe sites along the transects and their adjacent open areas. Rainfall had a significant effect on species diversity in non-living and living safe sites. Abundance and evenness increased in all safe sites; diversity indices increased in living safe sites and decreased in non-living safe sites. Soil nitrogen, carbon, potassium, and clay were significantly higher under the nurse shrubs. Results of this research indicate the crucial role of safe sites in maintaining the diversity of plant species under the harsh conditions of stressful environments on the limestone outcrops.
