Showing 9 results for Grazing
Mohammad Reza Vahhabi, Mehdi Bassiri, Jamaleddin Khajeddin,
Volume 1, Issue 1 (4-1997)
Abstract
Short-term changes (5 years) in canopy cover, species composition and forage production were studied under protection from grazing and grazed condition in 19 range sites in Fereydan region, Isfahan province. In this study, density, canopy cover and forage production data were obtained from quadrates inside and outside exclosures in the spring of 1983. These parameters were studied again in 1988 and compared with the previous data. Results indicated that species diversity in these range sites was relatively high up to 212 plant species were identified. Sixteen, 8.5 and 75.5 percent of these species were classified into I, II and III palatability classes respectively. After five years, comparison of inside and outside exclosures indicated an increase in the density of species of I, II and III palatability classes by 138.8, 120.8 and 51.5 percent inside exclosures, respectively. Density of all species had increased by 62 percent as a result of 5-year protection from grazing. Species composition data as canopy cover were used to construct 3 dendrograms to investigate the similarity among range Sites. Assuming 32% similarity as the threshold level, 19 range sites were classified into 10 vegetation types in 1983. After 5 years, these vegetation types decreased to 8 and increased to 11 under protection from grazing and grazed conditions, respectively. The average forage production inside exclosures was almost twice as much as in grazed sites (600 Vs. 315 kg/h). Three groups of range sites were recognized according to the time requirement for rehabilitation by grazing protection. The first group was improved considerably by the end of the 5-year protection Period. The second group improved relatively within five years of grazing exclusion. The third group did not improve by 5-year grazing protection and needed much longer protection period or some other range rehabilitation practices.
F. Raiesi Gahrooee, E. Asadi, J. Mohammadi,
Volume 9, Issue 3 (10-2005)
Abstract
Over-grazing may induce changes in the dynamics of plant residue carbon and soil organic carbon (SOC). The objective of this study was to evaluate the litter quality of three dominant pasture species, and the relationship between litter quality and C dynamics under different range managements in native rangelands of SabzKou. Aboveground litters from three dominant species including, Agropyron intermedium (AP), Hordeum bulbosum (HB) and Juncus stenophylla (JU) were collected in an area protected from grazing for 15 years. Concentrations of N, P and K in litter samples were determined. Litter decomposition was also studied by using a litter bag experiment. Bagged litters were incubated under field conditions at grazed and ungrazed sites for one year. Concentrations of N in litters were 1.37, 1.36 and 0.98, respectively, for AP, JU and HB. Assuming 50 % C in the litter, C/N ratios of litters were 37.2, 37.3 and 51.1, respectively, for AP, JU and HB. The litters of AP, JU and HB contained, respectively, 0.13,0.12 and 0.21 % of P, and 1.04, 1.01 and 1.72 % of K. Results indicate no significant (p>0.05) and consistent difference in litter decomposition rates between grazed and ungrazed areas. The three pasture species, however, showed significant (p<0.01) differences in litter decomposition rate. It is appearing that the trend in litter decomposition of these plant species correlates initially with litter C/N ratio, but other quality parameters of litter as well as soil environmental conditions would likely affect the litter decomposability in advanced stages of decomposition process.
H. Arzani, M. Jangjo, H. Shams, S. Mohtashamnia, M. A. Fashami, H. Ahmadi, M. Jafari, A. A. Darvishsefat, E. Shahriary,
Volume 10, Issue 1 (4-2006)
Abstract
Range suitability and its grazing capability are the most important criteria in rangeland analysis and monitoring. Determination and monitoring of factors affecting on range suitability and diagnosis of them are important .All range ecosystem components affect range suitability. Which among them physical and vegetational factors, forage production, water resources and sensitivity to erosion were considered. The objective of this research was to determine range suitability of Lar, Dasht bakan, Ardestan, Siahrood rangelands to design a model for sheep grazing. This study was carried out in four regions, two of them (Siahrood and Lar) located in Alborz mountain chain, Ardestan in center of Iran and Dashtbakan in Zagros mountain chain. According to the results among physical factors, slope remoteness of watering points and sensitivity to erosion had more effect on grazing capability than vegetation factors. In Siahrood watershed aboundancy of poisonous plants, high slope, transient watering points and non resistant formations were limiting factors. High slope, sensitivity of soils and stones to erosion, kind of exploitation in Lar watershed affected range suitability. In Ardestan watershed, low range productivity, presence of invader plants, erosion, remoteness of watering points are major limitation of range suitability. In Dasht Bakan factors including slope, elevation, dispersion of water resources and transient water resources were limited grazing capability. In land evaluation each land utilization type has certain land use requirement and each land unit has certain land qualities. Utilization of rangeland based on grazing capacity, range readiness and recreation of degraded rangeland can improve suitability of rangelands in the studied areas.
Sh. Ayoubi, M. H. Alizadeh,
Volume 10, Issue 3 (10-2006)
Abstract
Overgrazing is the most important agent which causes accelerated soil erosion and land degradation in arid and semi-arid zones of Iran. Appropriate planning and land use in these areas based on land suitability evaluation provide a suitable base for conserving the land and controling desertification. Land evaluation identifies possible alternatives in land use which will more effectively meet national or local needs and assists in assessing the consequences of these alternatives. Extensive grazing refers to the land utilization type in which animals feed in natural pastures. This study was performed to evaluate physical potential of the given watershed for grazing by sheep and goats, and assess the limiting factors for the land utilization type in Mehr watershed, Sabzevar, Khorasan province. Land qualities which were evaluated include accessibility to animals, soil erodibility, moisture availability, rooting conditions, salinity and alkalinity, and drinking water availability for animals. Above mentioned land qualities were assessed by appropriate land characteristics. The requirement of grazing land utilization type was defined in terms of rated land characteristics. Matching of requirements of LUT with the land qualities of each pixel of DEM (prepared in 200×200m by GIS software) resulted in a rating for every land characteristics. Some characteristics such as slope, aspect, and distance to drinking water for animals were calculated directly by GIS. Land index for every pixel was calculated by square root method. Finally, qualitative and physical land suitability classes were determined based on land indices and classified to polygons which would be suitable in grazing management. The results were interpreted under two different scenarios. In the first scenario, drinking water for animals was supplied by permanent sources and in the second one, the supplying of water was developed to temporary rivers besides the permanent sources. With the analysis of spatial modeling it was possible to assess the land suitability with higher accuracy. Overall results showed that the given area was not highly suitable for grazing at all. The most limiting factors included moisture availability for plant growth, slope, rock fragment and outcrops and distance to drinking water. Also during the late winter, spring and early summer, when the seasonal rivers were supplying the drinking water, the limitation of given area was decreased.
M. Sheklabadi, H. Khademi, M. Karimian Eghbal, F. Nourbaksh,
Volume 11, Issue 41 (10-2007)
Abstract
The effect of overgrazing on vegetation changes in central Zagros has been studied by a few scientists, but there is no detailed information on the impact of such practices on soil properties. The objective of this study was to assess the effect of climate and grazing management on selected soil biochemical properties. Fourteen experimental range sites protected against grazing as well as their adjacent overgrazed sites in Chadegan, Pishkuh and Poshtkuh were selected. In each site, samples were collected from the depths 0-5 and 5-15 cm. Soil organic C (OC), microbial biomass C (MBC), total nitrogen (TN), organic C to total N ratio (C/N), microbial biomass C to organic C ratio (Cmic/Coc) and metabolic quotient (qCO2) were measured and/or calculated. The results showed that the lowest SOC, MBC, TN and Cmic/Coc occur in Chadegan due to low fresh materials input. The above parameters in Pishkuh and Poshtkuh regions are 2.5 to 3 times greater than those in Chadegan area. Grazing intensity in Pishkuh is less than that in Poshtkuh region and there is no significant difference between grazed and protected sites in Pishkuh. But, there is a significant difference between grazed and protected plots in Poshtkuh due to a higher grazing intensity. Higher Cmic/Coc and lower qCO2 suggest that the quality of organic matter is better in Poshtkuh and Pishkuh. In conclusion, highly degraded rangelands in Pishkuh and Poshtkuh seem to be able to recover very quickly with proper management, while Chadegan region needs a much longer period of time to restore.
A Ephtekhari, M Farahpour, H Arzani, J Abdolahi,
Volume 13, Issue 47 (4-2009)
Abstract
Species which were grazed by livestock and wildlife in range sites and the portion taken by each animal were the subject of this study. Two sites occupied with Scariola orientalis (Boiss.) Sojak and Artemisia sieberi Besser and another with Aellenia subaphyla (C.A.Mey.)Aellen and Artemisia sieberi were selected for the study. These sites were already established by Yazd Research Center for Agriculture and Natural Resources. Sites should be covered with similar vegetation (72% similarity), as much as possible indeed. One site, by the name of Kalmand, is a protected area and is exclusively grazed by Iranian gazelle, while the other, Jadehdehshir, by sheep and goat. Results of the study show that the selection of species is the same by these animals. Both are interested in the following species: Artemisia sieberi, Scariola orientalis, Bromus tectorum L, Stipa barbata Desf. , Noaea mucronata (Forsk.) A schers.et Schweinf, and Launaea acanthodes (Boiss.)o.Kuntze. On the contrary, species such as Acantholimon scorpiurs (Joub. &Spach) Boiss, Astragalus albispinus L were not taken by the animal for their woody stems and thorny branches. Fresh and non woody parts of the plants were grazed by both types of animal. Similarity between grazing behavior of wildlife and livestock in Yazd province shows that wildlife feed requirement should be seriously taken into account when grazing capacity of rangelands is to be evaluated.
M. Riahi , F. Raiesi,
Volume 16, Issue 59 (4-2012)
Abstract
Mountainous landscapes in Central Zagros are mainly used as grazing rangelands to feed animals and are heavily degraded. Overgrazing may impose a negative effect on rangeland productivity and sustainability through significant changes in soil properties. Soil nitrogen (N) mineralization is one of the key biological processes that might be affected by biotic and abiotic factors including range grazing regime or intensity. The primary objective of this study was to assess the effects of rangeland management (grazing and ungrazing regimes) on soil N mineralization in natural rangelands of Chaharmahal VA Bakhtiyari province. Three range management regimes including a) long-term ungrazed, b) controlled grazed and c) freely- (over)-grazed plots in a close vicinity were selected in three regions consisting of SabzKouh (protected from grazing for 18 years), Boroujen (protected from grazing for 23 years) and Sheida (protected from grazing for 2 years), and soil samples were collected from 0-15 cm depth for some physical and chemical properties. Soil N mineralization was measured under standard laboratory conditions. At SabzKouh, the effect of range management on the cumulative N mineralization and the proportion of N mineralized (%) was significant (P<0.05) and ungrazing regime resulted in 89% and 96% increases in soil N mineralization in ungrazed rangelands compared with controlled grazed and freely- grazed rangelands, respectively. Similarly, soil N mineralization was significantly greater (P<0.05) in ungrazed rangelands (3.3- to 3.5-folds) than in controlled grazed and freely-grazed rangelands at Boroujen site. However, at Sheida site with short-term ungrazing period and cropping history there were no significant and considerable differences in soil N mineralization among the three grazing regimes. Briefly, degraded rangelands at SabzKouh and Boroujen sites seem to recover rather quickly from long-term overgrazing with a proper grazing management, while rangeland ecosystems at Sheida site need a much longer period for steady-state conditions and for improvements in soil quality and fertility after long-term soil degradation and disturbance.
N. Ghorbani Ghahfarokhi, Z. Kiani Salmi, F. Raiesi, Sh. Ghorbani Dashtaki,
Volume 17, Issue 63 (6-2013)
Abstract
Free and uncontrolled pasture grazing by animals may decrease soil aggregate stability through reductions in plant cover and subsequent soil organic C, and trampling. This could expose the soil surface layer to degradation and erosion. The objective of this study was to determine the influence of pasture management (free grazing, controlled grazing and long-term non-grazing regimes) on aggregate-size distribution and aggregation parameters by wet and dry sieving methods in two native pastures, protected areas in Chaharmahal va Bakhtiari province. The studied pastures were 1) SabzKouh pastures protected from grazing for 20 years, and 2) Boroujen pastures protected from grazing for 25 years. Soil samples were collected from 0-15 cm depth during the grazing season in summer 2008. Samples (finer than 2 mm) were analyzed for aggregate-size distribution and aggregation parameters by wet and dry sieving methods. Results showed that pasture management had a significant influence on aggregate-size distribution and aggregation parameters in the two areas. The two methods indicated that macro-aggregates in non-grazing and controlled grazing regimes were higher than those in free grazing regime, whereas in free grazing management micro-aggregates showed an opposite trend, and were greater compared with the other grazing regimes. Similarly, soil aggregate stability indices (i.e. mean weight diameter, aggregate geometric and ratio mean diameter) were all improved by non-grazing regimes, suggesting that animal grazing and trampling break down large soil aggregates due largely to compaction and reduced plant coverage. However, the extent to which grazing affects soil aggregation depends in large part on grazing intensity and duration, and the area involved.
M. Kazemi, H. Karimzadeh, M. Tarkesh Esfahani, H. Bashari,
Volume 22, Issue 4 (3-2019)
Abstract
Evaluating the possible relationships between vegetation and environmental characteristics can assist managers to identify effective factors influencing plants establishment and to characterize various vegetation communities. This study was aimed to evaluate the effects of long term grazing exclusion ( more than 33 years) and the controlled grazing system (resting – rotation grazing system) on the vegetation distribution and some soil properties in the Hamzavi research station in Hanna area-Semirom, Isfahan. Six transects (three parallel transects and three transects perpendicular to the general slope of the area) were established in each area and 10 square plots with the size of 2m2 were placed along each transect; then, the cover percentage, production and list of all plant species were recorded. In each area, eighteen plots were collected randomly and in each plot, five soil samples were collected from 0-30 cm of the soil and then the samples were mixed and one sample of the compound was selected as an evidence plot. Soil properties such as pH, EC, CaCO3, organic carbon, absorbable phosphor, total nitrogen, K, Ca, Mg, soil saturated percentage, cation exchange capacity, soil clay, silt, sand and fine sand contents were measured in the soil laboratory. The independent t test was used to compare the vegetation characteristics in two areas. Cation exchange capacity, CaCO3, gravel percentage, soil phosphor content and grazing management were identified as the most discriminative factors in separating vegetation communities based on Canonical correspondence analysis (CCA) and cluster analysis. Controlled grazing management significantly modified some soil characteristics and increased the production (352 versus 184.2 kg/ha) and vegetation cover percentage (25.46 versus 18.37), as compared to the exclusion area (α= 5%). The vegetation density was increased significantly in the exclusion rather than controlled grazing area (3.03 versus 2.02 plant/m2). This study, therefore, revealed that controlled grazing management was more effective on improving some soil quality and vegetation characteristics rather than p long term grazing exclusion in the semi-arid ecosystems. So, avoiding long term grazing exclusion in semi-arid rangelands is suggested.
