ardashir pounrnemati; ardavan ghorbani; jaber sharifi; farzad mirzaie; masoume amirkhani; mahmoud goudarzi
Volume 24, Issue 1 , May 2017, , Pages 110-125
Abstract
The purpose of this study was to investigate the relationship between rangeland plants production based on total production and life forms of grasses, forbs, and shrubs with topographic factors (altitude, slope, and aspects) in Sabalan rangelands, Ardabil province. To determine the annual total production, ...
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The purpose of this study was to investigate the relationship between rangeland plants production based on total production and life forms of grasses, forbs, and shrubs with topographic factors (altitude, slope, and aspects) in Sabalan rangelands, Ardabil province. To determine the annual total production, the amount of production was estimated using harvesting method in one square meter plots (totally of 216 plots) under the altitude range of 1200 to 2900 meters a.s.l. Using topographic maps, the digital elevation model was derived and classified maps of elevation, slope, and aspect were derived. Then, in each plot, information such as elevation, slope, and aspect was extracted. The correlation between life forms and topographic factors was analyzed using multivariate regression method. The results showed that there was a significant relationship between the production of life forms such as grasses (P<0.01), forbs (P<0.01) and shrubs (P<0.05) with topographic factors; however, there was no significant relationship between total production and topographic factors (P>0.05). The production of grasses, forbs and total production had direct relationship with slope; however, the production of shrubs decreased with the increase of slope. The production of grasses increased with altitude, and in the east-faced slopes, it was estimated more than the other aspects. The production of forbs decreased with the increase of altitude and was higher in the east aspect in comparison with the other aspects. The production of shrubs and total production in the middle altitude and in north –faced slopes were more than the other classes and aspects according to the suitable ecological condition and low degradation. Although it is obvious that elevation, slope, and aspect can change and affect the production, this effect is unknown, especially in the connection with life forms and the process of change. Overall, it can be concluded that these results could be used in the management of these rangelands, particularly in the improvement and rehabilitation practices.
ardavan ghorbani; ardashir pournemati; mohsen panahande
Volume 24, Issue 1 , May 2017, , Pages 165-180
Abstract
The aim of this study was to estimate and map the plant group and total aboveground phytomass using Landsat 8 images in the rangelands of Sabalan Mountain. Images were selected on the 19th of July 2013 and field data were collected in April and July based on maximum matching with the phenology of the ...
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The aim of this study was to estimate and map the plant group and total aboveground phytomass using Landsat 8 images in the rangelands of Sabalan Mountain. Images were selected on the 19th of July 2013 and field data were collected in April and July based on maximum matching with the phenology of the study area and in the closest date to the time of image acquisition. Twenty-four sampling sites on six vegetation types were determined. In each site, 9 sampling plots, based on previous studies, which are required for minimum sample number according to the variance of vegetation distribution, were determined in a systematic-random method, and the aboveground phytomass of vegetation groups, such as grasses, forbs, shrubs and total, were determined using the harvesting method. Initially, to calculate vegetation indices, the averages of 16 pixel values of the location of sample units from the corrected images were derived and transferred to the software environment. The correlation matrices between the derived pixel values and field collected data for the 24 selected vegetation indices were calculated and used for the estimation of grasses, forbs, shrubs and total aboveground phytomass. The results showed that indices such as RVI, TNDVI and GNDVI had the highest correlation with the aboveground phytomass of grasses, PD312, IO and PD311 with the aboveground phytomass of forbs, RDVI, DVI and RVI with the shrubs, and PD311, PD321 and PD312 with the total aboveground phytomass (P <0.01). In the second stage, three of the indices, having the highest correlation with the aboveground phytomass of each group and entire previous stage, were selected, and Landsat8 images were used to calculate the aboveground phytomass of each vegetation group and the total aboveground phytomass was calculated. The aboveground phytomass maps of each group and the total aboveground phytomass were controlled with sampling points to assess the accuracy. The results of this study showed that the best maps were obtained using the TNDVI index for grasses aboveground phytomass, PD312 for forbs, RVI for shrubs groups and PD311 for the total aboveground phytomass. Moreover, some indices, such as PD311 and RVI, could be used for all growth forms and estimation of total aboveground phytomass (P<0.01) and (P<0.01). In general, Landsat 8 data could be used to estimate and map the aboveground phytomass of vegetation groups and to determine the carrying capacity of the total aboveground phytomass in Sabalan rangelands, having advantages based on cost, time and the ability to monitor large areas with repeatability potential in comparison with the ground-based methods.