جستجوی مقالات مرتبط با کلیدواژه « A.fragrans » در نشریات گروه « کشاورزی »

The purpose of this research was to model the spatial distribution of Artemisia fragrans and A. chamaemelifolia in Ghezelozen-Aghdagh elevation profile rangelands of Khalkhal city. For modeling, information about species and habitat factors such as topography, soil, and climatic factors were used, and habitat distribution modeling was performed by a logistic regression method. All parameters affecting the distribution of species were prepared as a raster map. Then, by combining the maps of the factors affecting the species distribution, the distribution map was predicted through the logistic regression method. The results showed that the most important factor in spatial prediction of A. fragrans in the region was altitude and with each meter of elevation, the presence of this species decreased by 0.88%. The results also showed that the presence of A. chamaemelifolia species was inversely related to altitude, mean temperature, and soil potassium. The Kappa index was used to determine the agreement between the prediction models with ground truth. The kappa coefficient was 0.91 for A.fragrans and 0.62 for A. chamaemelifolia, which indicates the excellent agreement of the model with reality. According to the prepared forecast map, A. fragrans and A. Chamaemelifolia species can be considered for lowland and higher altitude rangelands.

This study was aimed to determine the feasibility of spatial statisticsin studying the spatial variations of density, canopy cover, and production for Artemisia fragrans in the southeast slopes of Sabalan. Initially, the normality test was conducted using SPSS16 software. Then, spatial statistical analysis including studying the spatial variability of density, canopy cover, and production of the studied species were conducted through the variograms of data and mapping the parameters using different interpolation and spatial statistical methods in the GS and ArcGIS10 software. The accuracy assessment of maps was done using cross validation and three methods including: Root Mean Squared Error (RMSE), Mean Bias Error (MBE), and Mean Absolute Error (MAE). Results showed that the exponential model was the best-fitted variogram model and the data had high spatial structure. Among spatial statisticalmethods, the ordinary and universal co-kiriging were the best methods for the three parameters studied. According to the maps produced from these methods, A. fragrans is mostly distributed on the central and northeast parts and in low altitudes. Overall, spatial statistical techniques could be applied to zone the perennial key species of rangelands with proper sampling units.

The purpose of this study was to identify the effects of environmental factors on distribution of Artemisia fragrans and Artemisia austriaca in southeastern rangelands of Sabalan. For this purpose، 140 sites were selected based on a random- systematic approach. The density of selected plant species were measured in five plots of 1m2، established along a 40 meters transect in each site. Soil samples were collected from 0 to 30 cm of soil surface in the beginning، middle and end part of each transect and their EC، OC، K، P، Lime، pH، TNV، sand، clay and silt content were measured. Litter and bare soil percentage were also measured in each site. One way ANOVA was performed to explore the relationships between the environmental factors characteristics and presence and absence of the selected species. Duncan's test was used to compare the mean values of the measured variables. Discriminant analysis was used to determine the importance of measured variables on the distribution of A. fragrans and A. austriaca and grouping the sampling sites. According to the results، the two produced functions were explained 86 % and 14% of the variances. The results indicated that 94/2% of grouped sites were classified correctly. Litter، elevation، precipitation، temperature، OC، bare soil، gravel، K، sand، silt، slope and aspect were identified as the most important factors، influencing the distribution of A. fragrans and A. austriaca in the study area.

Livestock Grazing is as the most effective factor in changing dimensional characteristics and plant biomass in rangelands that affected different aspects of ecosystem production. Regarding to the fact that Artemisia fragranus is the main species of mountainous rangeland in Khoy and the limited quantitative information about the effect of different grazing intensities on structural characteristics, aerial biomass and especially underground biomass is available, so in the present study the effect of different grazing intensities (light, intermediate and heavy) on structural characteristics, aerial and underground biomass was assessed. Therfore, three rangeland sites with various grazing intensities are selected and 60 plots of 1 m2 along 100 m transects were established. Thus, structural characteristics, litter, aerial and undergrlound biomass of Artemisia fragrans were measured in the study sites. To compare the means of dimensions and biomass components of species in three study areas, analysis of variance and multiple Duncan mean comparison test were used. The results proved that there are significant differences among studied parameters (except for collar diameter and collar area) of studied species among three grazing intensities. The most and the lowest means of aerial biomass in 2 places with low and heavy grazing intensity were 18.5 and 42.76 gr. also, the most amount of ground biomass was 32.95gr and the lowest amount of ground biomass was 56.46gr that belong to places with low and high grazing intensity. Calculating of variation percent of the parameters in each sites of moderate and heavy intensity in relation to light grazing showed that all parameters have declined and the most variation percent of study species parameters belongs to heavy grazing site. Generally, decline amount for collar diameter and collar area is the lowest and also for aerial and underground and litter parameters is the highest.ý