مجله بوم شناسی کاربردی
پیاپی 43 (بهار 1402)

Recognition of the influential environmental factors in natural ecosystems plays a significant role in the success of the life cycle of existing plant species. This study was conducted to investigate some of the dominant ecological features affecting the morphological alterationsof the reproductive organs of Gundelia tournefortii L. in 11 major habitats of this species in the central Zagros region, Iran. Two influential features of vegetation (canopy cover percentage and density per unit area), 14 environmental factors in three groups of physiography, soil and climate along with nine morphological features related to reproductive organs of G. tournefortii L. (inflorescence and seed) were assessed in its major habitats, following the relevant assessment methods. Results were analyzed using Pearson's correlation test, Principal Component Analysis (PCA) and cluster analysis. The environmental factors, including absorbable potassium, soil shear strength, electrical conductivity, length of dry period, average annual temperature, average number of frost days and average altitude were the most important dominant ecological features in the morphological variations of plant reproductive organs.  Identifying the relationship between vegetation and the affecting ecological features plays  a very efficient role in achieving accurate information sources in the management of natural habitats.

The current research aimed to assess the fluctuations of Soil Organic Carbon (SOC) variations in different types of forest stands along the gradient of altitude, and identify the influential factors for the its variations. Based on the random design, four plots with the surface area of 400 m2 in different stand types were established. Soil sampling up to 15cm depth in center and the corners of the each plots were taken. The biophysical attributes of trees as well as physiographical units were measured and recorded within each plot. The results of one-way ANOSIM analysis indicated the lack of similarity of SOC between pure and mixed beech stands (R≅ 0.5) and no significant difference between other stands. The results of the two-way PERMANOVA test also showed that the amount of SOC is independent of the effects of slope and the elevation gradient. The SIMPER test illustrated that the trends of soil organic carbon and soil bulk density were inverse among the stands and the gradient of altitude. However, their trends were not symmetric based on the pairwise comparisons. As a general conclusion, the fluctuations of soil organic carbon in the different types of forest stands are independent of the altitude gradient, stand type and biophysical factors, and the relative abundance of various tree species did not have a significant contribution to the variability of the soil carbon storage of the studied stands.

In order to make decisions for regional planning and achieve sustainable development, it is necessary to quantify land use and land cover changes. In this study, the land use and land cover maps of the Zayandehrood Dam watershed were prepared for the period of 1991 to 2021, using Landsat satellite images, and the changes that occurred in this period were revealed. Using the land change modeler (LCM), land use and land cover and their future changes for 2051 were modeled and predicted. The results showed that in the period between 1991 and  2021, the coverage of poor rangelands with 51,871 hectares of change had the largest decreasing trend, and the agricultural class had the largest increasing trend with 71,478 hectares of change. The largest decline in the period from 2021 to 2051 is related in the coverage of the fair rangelands class with 66192 hectares, and the agricultural class potentially has the largest increasing trend with 70328 hectares of change. The findings of this research will be useful for policymakers and planners. They can use the findings of this study for spatial planning in the region, managing the process of land use and land cover changes for sustainable development.

The present study was carried out to assess the risk of non-native Nile tilapia (Oreochromis niloticus L.) in Iran. The common invasive risk assessment protocols of non-native species were examined according to specific criteria, and the invasive risk assessment of this species was applied based on the selected method and auxiliary tools of species distribution models. The Aquatic Species Invasiveness Screening Kit (AS-ISK) received the highest score for assessing the invasive risk of non-native fishes in the freshwaters of Iran. The results showed that the risk of the species in Iran is high, and its impacts are significant. The mean scores of the Basic Risk Assessment (BRA) and the total risk assessment (BRA+Climate Change Assessment) were obtained as 41.5 and 53.5, respectively, which are much higher than the threshold values of the model for Iran (i.e., 21). Also, according to the results of other protocols used, the species has a high risk. Overall, the Nile tilapia possess a high potential invasive risk in the country, and unfortunately, its control is complicated, costly and mostly impossible in the recipient ecosystems. Therefore, as the best management measure, preventing the introduction of this species should be considered.

Competition is an interaction between a species’ members or different species under the ecological needs to use the same resources. The present research aimed to quantify the competition in a mixed stand in the Arasbaran forest. Sampling was a distance method. The diameter at breast height, total tree height, two diameters of the tree's crown, and the distance of the trees were measured (one tree as the target and four neighboring as the competing trees). Data was analyzed using the distance-dependent and distance-independent competition indices. The results showed that the distance indices value were 0.29 to 31.71 and distance-independent indices were 0.94 to 4.43. There was a significant negative correlation between the stand quantitative characteristics and the distance between trees with the value of distance indices in most cases. The correlation between canopy diameter and area with distance indices was positive and significant, but with distance-independent indices was slight and not significant. Competition quantification in mixed stands will provide to know the relationship between the amount of competition and the quantitative characteristics. Consequently, and can provide knowledge for silvicultural treatments, and forest management strategies to balance the competition level in natural stands to reach the desired mixed structure.

This study aimed the investigating the structure of energy production and the global warming potential of wheat production in Mehran and Dehloran regions. Information about the consumption of inputs and outputs was collected through questionnaires and interviews with local farmers. The results of the research showed that the total energy consumptions in these areas were equal to 6715.3and 68988.4 MJ/ha, and the energy outputs were calculated as 81820 and 94390 MJ/ha, respectively. Economic analysis showed that the profit-to-cost ratios in Mehran and Dehloran regions were equal to 1.42 and 1.58, and the economic productivity of productions were 3.17 and 3.52 kg /Rial, respectively. Based on the Cobb-Douglas function, the coefficients of determination (R2) in Mehran and Dehloran regions were 0.93 and 0.96 respectively. The amount of total emissions of carbon dioxide, nitrogen oxide and methane from wheat cultivation in Mehran was 1328.73, 8228.67 and 33.35 kg/ha, respectively, and in Dehloran was equal to 1431.26, 8503.67 and 36.08 kg/ha, respectively. The global warming potential value of production in Mehran region was at about 9590.75 and in Dehloran region equaled to 9971.01 kg equivalent of carbon dioxide per hectare.