Moselm Rostampour
Abstract
This study compared of univariate outlier detection methods among vegetation data in a study of the effect of grazing intensity in the rangelands of arid regions. For this purpose, after measuring the vegetation cover in the rangeland and before the statistical analysis, the presence of outlier data ...
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This study compared of univariate outlier detection methods among vegetation data in a study of the effect of grazing intensity in the rangelands of arid regions. For this purpose, after measuring the vegetation cover in the rangeland and before the statistical analysis, the presence of outlier data was examined as the assumption of parametric comparison tests. In this study, eight methods including the boxplot and IQR (Tukey method), standard deviation of the mean (three-sigma rule), median absolute deviation (Hampel method), trimmed mean, 1st percentile and 99th percentile, The Chi Square test (χ²), the Grubbs Test (ESD) and the Rosner test (generalized ESD) were used. The results showed that the vegetation cover of rangelands with light and moderate grazing intensity was not normally distributed (Shapiro-Wilk test: p≤0.05). Even deletion of outliers did not lead to a normal distribution, but it resulted in the homogeneity of variances (Levene's test: p≥0.05). The modified Z-score and the Grubbs and Rosner tests (p≥0.05) did not identify outliers from the vegetation cover data. Among the methods evaluated, the boxplot and MAD method, which are not dependent on the mean, are more suitable for the vegetation cover. Therefore, before performing any comparison test, a combination of visual and statistical methods is recommended to evaluate the presence of outliers.
Ali Asghar Naghipour; Maedeh Sharifi; Ataollah Ebrahimi; Elham Ghesareh Ardestani; Sina Nabizadeh
Abstract
Fire is one of the important ecological factors that affect the dynamics of rangeland vegetation. In recent decades, the incidence of wildfires in semi-steppe rangelands has increased significantly, challenging the adaptive capacity of plants for post-fire regeneration. In the present study, the germination ...
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Fire is one of the important ecological factors that affect the dynamics of rangeland vegetation. In recent decades, the incidence of wildfires in semi-steppe rangelands has increased significantly, challenging the adaptive capacity of plants for post-fire regeneration. In the present study, the germination response of eight annual and perennial herbaceous species of semi-steppe rangelands of Chaharmahal va Bakhtiari province to fire products treatments including heat (60, 80 and 100° C), smoke, ash, and the combined effect of heat and smoke treatments were investigated. Also, percentage cover change of studied species, one year after the fire were measured in the field. The results showed that the germination of seeds of eight studied plant species showed a significant positive or negative reaction to at least one of the fire product treatments. Combined treatment of smoke and 60° C caused a significant increase in the mean germination percentage of Heteranthelium piliferum. This treatment also significantly reduced the mean germination time of Cousinia cylindracea. Ash treatment also increased the mean germination percentage of Alyssum linifolium and Stachys lavandulifolia. Vegetation sampling results also showed that among the eight species studied, H. piliferum and Taeniatherum crinitum were fire adapted and six species were tolerant. The results of this study can be used as a potential factor to understand the dynamics of vegetation and restoration of degraded rangelands.
moslem yazdani; reza erfanzadeh; Asghar Mosleh Arani
Abstract
Study of the effect of woody plant species on the production, diversity and richness of substratum herbaceous species, especially in the arid and semiarid regions, is essential for the proper management of these ecosystems. Therefore, the rangelands of Chenarnaz region in Khatam city in Yazd province ...
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Study of the effect of woody plant species on the production, diversity and richness of substratum herbaceous species, especially in the arid and semiarid regions, is essential for the proper management of these ecosystems. Therefore, the rangelands of Chenarnaz region in Khatam city in Yazd province were selected and then, using 0.5m×0.5m quadrats, vegetation sampling was performed under the selected 15 sites from Daphne mezerum, Amygdalus scoparia and Ebenus stellate (growing in equal topographical conditions) canopies, and outside of the canopies (as control). In each quadrat, the cover percentage of each plant species was visually estimated and the productions were measured by clipping and weighing method. The species diversity and richness indices were calculated using Past software through introducing the plant covers into the software. The results showed that the most values of Shannon-Weaner and Simpson diversity indices were found under A. scoparia (2.07 and 0.80, respectively) and the lowest values were found under E. stellata (1.010 and 055, respectively). In addition, the highest values of Menhinik and Margalef richness indices were found under A. scoparia (4.90 and 3.43, respectively) and D. mezerum (4.25 and 3.12, respectively), while the highest production was found under E. stellata (64.76 g/m2). The results of this study showed that different woody species had the desired but different effects on the herbaceous species, in such, A. scoparia and D. mezerum had significant positive effects on species diversity and E. stellata increased significantly species production; therefore, conservation of all woody species is emphasized in the region.
