Elham Banihashemi; Pezhman Tahmasebi; Esmael Asadi
Volume 25, Issue 3 , November 2018, , Pages 547-561
Abstract
Livestock grazing is one of the most important factors influencing on the structure and dynamics of the rangeland vegetation. The aim of this study was to identify the plant functional traits as the indicators for the effects of grazing management on Karsanak semi-steppe rangelands ...
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Livestock grazing is one of the most important factors influencing on the structure and dynamics of the rangeland vegetation. The aim of this study was to identify the plant functional traits as the indicators for the effects of grazing management on Karsanak semi-steppe rangelands of Chahar Mahal Va Bakhtiari province. A randomized-systematic sampling method was used to survey vegetation in seven grazed and enclosure sites by estimating plant cover in five plots of 4 m2 along a 100-m transect in each site. Then, the plant traits were measured and compared among grazed and enclosure sites. The results showed that there were significant differences between grazed and enclosure sites in several functional groups including plant height, leaf area, total plant weight , palatability class I and II, annuals and perennials, therophytes , and geophytes (P<0.05). The results also showed that the mean value of leaf length, the plant cover of species with palatability class II, forbs, and therophytes were significantly increased in non-grazed area compared to grazing area. The results of PCA showed that the most affecting factors responsible for overall changes in vegetation were plant weight, perennial and annual plant species, shrub growth form, chaemophytes, phanerophytes and phanerophytes forms, leaf length, leaf width, leaf area, and palatability class II and class III, justifying 60% of total variation in plant community composition. Combining the results of t-test and PCA, the results indicate that plant traits including total plant weight, leaf length and width, leaf area, palatability class, and life form are among the most important indicators to evaluate the effect of grazing managements on the structure and dynamics of vegetation in semi- steppe rangelands.
Zeynab Jafarian; Farzad Ahmadi; mansoureh Kargar
Volume 24, Issue 4 , January 2018, , Pages 768-777
Abstract
This study was carried out in Bolban Abad, Kurdistan province, Iran, in order to investigate the changes in species diversity and functional diversity of vegetation under different grazing intensities. In this study, the data of three sites with different grazing intensity (low, moderate and heavy) were ...
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This study was carried out in Bolban Abad, Kurdistan province, Iran, in order to investigate the changes in species diversity and functional diversity of vegetation under different grazing intensities. In this study, the data of three sites with different grazing intensity (low, moderate and heavy) were collected. Indices of species diversity including: richness (S), Shannon (H), evenness (E) and Simpson (D) and the functional diversity index (convex hull hyper-volume (CHull), Functional Richness (FRic), Functional Evenness (FEve), Functional divergence (FDive) and index Rao (Rao) were calculated for all sites. FD package and generalized canonical discriminant analysis (gCCA) were used in R 3.1.1to calculate these indices and determine the effect of grazing intensity on diversity indices. In addition, Duncan's test was used to compare the means of grazing intensities. Results showed that the species diversity indices, species richness index (S) and Shannon (H) were reduced by increasing grazing intensity. According to the results of generalized canonical discriminant analysis, species richness showed little change in response to grazing and CHull index showed an increase under grazing. Also, species functional traits were decreased with increasing of grazing intensity.
Parviz Gholami; Jamshid ghorbani; Maryam Shokri; MOstafa Tarkesh; Nosratollah Safaeian
Volume 24, Issue 4 , January 2018, , Pages 870-880
Abstract
Stachys byzantina is one the major increaser species in rangelands of north face of Alborz Mountain in Mazandaran province. The purpose of this study was to assess the effects of its invasion on vegetation under some disturbances in Vaz Chamestan summer rangelands in Mazandaran ...
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Stachys byzantina is one the major increaser species in rangelands of north face of Alborz Mountain in Mazandaran province. The purpose of this study was to assess the effects of its invasion on vegetation under some disturbances in Vaz Chamestan summer rangelands in Mazandaran province. Vegetation sampling was carried out in exclosure, and invaded rangelands including abandoned dryland, moderate grazing and heavy grazing sites. The vegetation and some characteristics of Stachys were sampled in 1 m2 quadrates along transects. The results showed that Stachys byzantina had greater quantities in abandoned dryland and rangelands under moderate grazing. The cover percentage of total perennials, perennial grasses and forbs significantly reduced from exclosure to heavy grazing and abandoned dryland. Total annuals plants, annual grasses and forbs significantly increased in abandoned dryland. A significant negative correlation was found between cover percentage of perennials and the cover and density of Stachys byzantina. Moreover, the forage production of forbs was negatively correlated withthe cover and density of Stachys byzantina. Multivariate analysis showed that species composition significantly changed under invasion, showing a reduction for palatable species.
Ardavan ghorbani; Ardashir Pournemati; Amin Pourali; mekaiel Badrzadeh; Ali Teimour zadeh
Volume 24, Issue 3 , October 2017, , Pages 581-595
Azam Khosravi Mashizi; Gholamali Heshmati; Adel Sepehri; Hossein Azarnivand
Volume 18, Issue 2 , September 2011, , Pages 244-257
Abstract
Aim of this study was to introduce of the functional threshold by ecological process changes along grazing gradient to determine destroyed area.In order to prove the existence of a threshold, two linear models and three nonlinear models (exponential curve, a piecewise regression and a sigmoid logistic) ...
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Aim of this study was to introduce of the functional threshold by ecological process changes along grazing gradient to determine destroyed area.In order to prove the existence of a threshold, two linear models and three nonlinear models (exponential curve, a piecewise regression and a sigmoid logistic) were fitted on stability, infiltration and nutrient cycling data.Two nonlinear models (exponential curve and a piecewise regression) provided a much better fit to the data than the linear models. It is the evidence of threshold along grazing gradient.Results also showed that ecosystem function descended near the water point that it needs special attention of the managers.The passing of the structural threshold, increase of invasive vegetation and animal trampling were identified as the main factors in the decline of ecosystem function near the water point and occurrence of functional threshold.According to the results, the recognition of the threshold is suggested for rangeland ecosystem because defining the threshold will help land managers to prevent the occurrence of undesirable states and promote for sustainable management of rangeland ecosystems.