Background: Range species have varying sensitivities to livestock grazing, which can be exacerbated by climatic conditions. Preserving high-quality pasture and edible species and maintaining plant composition and productivity in the pasture ecosystem requires appropriate levels of pasture exploitation. Thus, knowledge of the Allowable use of rangeland species is essential for the management of these ecosystems. This study aimed to determine the Allowable use of key species in Zagheh alpine rangelands. Methodology: The study selected 40 average stands of the species Astragalus curvirostris, Bromus tomentellus, Festuca ovina, Onobrychis melanotricha, and Picris strigosa to determine Allowable use. The stands were subjected to different levels of harvest treatment over five years (2011-2016), with stands 1-10 left unharvested and used as a control. Stands 11-20, 21-30, and 31-40 were subjected to 25%, 50%, and 75% harvest treatments, respectively. An additional ten plants were selected as annual witnesses and weighed using an electric scale with an accuracy of 0. 01 grams. The data collected included vigor, mortality, plant height, and production, which were analyzed using MSTAT-C software. Results: The study found that O. melanotricha increased in production with a 25% harvest treatment, but harvesting at 50% and 75% caused stands to die. Harvests of 25%, 50%, and 75% increased the production of B. tomentellus compared to the control. F. ovina showed greater resistance to harvesting than other species, with the highest production in the control and 75% harvest treatments. A. curvirostris should not be grazed more than 50%, while P. strigosa is not very sensitive to grazing in the flowering stages and after but is sensitive to grazing in the first season. Conclusion: The Allowable use of species can be expressed as follows: F. ovina can tolerate up to 75% harvest, while O. melanotricha can tolerate 25%, A. curvirostris 25-50%, B. tomentellus 50%, and P. strigosa 25-50%. However, the grazing season must be carefully observed to ensure successful management of rangelands.

To investigate the Allowable use of Stipa barbata, five sites were selected in the semisteppe rangelands of the country. In the beginning of grazing season, 40 individuals were selected in each site and protected from grazing. Different harvesting treatments were applied including control, 25%, 50%, and 75%. The simulation method was applied to calculate the production and harvestig rate. The mortality, height, and seed production rate of the study species were also evaluated after application of treatments. The data were collected over the years of the research and analyzed in a split plot design based on completely randomized design with SAS and SPSS software. The means of traits were compared with Duncan test. The interaction of treatments was analyzed using the AMMI model with IRRISTAT software. Our results clearly showed that an Allowable use of 50% could be recommended as the Allowable harvesting rate for Stipa barbata in similar sites.

Determining the Allowable use is one of the basic requirements to calculate the grazing capacity in range management plans. In this study, initially, the range condition and trend of vegetation types and the suitability class of soil susceptibility to erosion were determined. Then, the Allowable use was determined for each vegetation type regarding the mentioned indices and that the Allowable use in each climate region is recommended differently to maintain rangeland health. The maximum Allowable use for the study rangelands, representing mountainous semi-steppe, was calculated to be 40%. The Allowable use of other vegetation types was determined regarding the limitations of indices. According to the results, the Allowable use was calculated to be 40%, 30%, 25%, and 15% for 21. 4%, 13. 6%, 19. 3%, and 27. 6% of the study rangelands, respectively. Around 18. 1% of the study rangelands were classified as non-utilizable due to the poor range condition, negative trend and the soil susceptible to erosion. In most areas, poor range condition and negative trend acted as a limiting factor and led to a low estimate of Allowable use. Therefore, care must be taken in selecting the indices affecting the Allowable use of range habitats and in addition to plant health, range condition and trend as well as ecosystem health should be considered.

A proper utilization of rangelands could result in preventing degradation, maintaining desirable species and improving range condition, leading to longterm and economic production. This research was aimed to investigate the Allowable use of Stipa hohenckeriana in Kordan rangelands. In this study, a reference area of one hectare was selected and fenced in the first year of the study. Treatments included four harvesting intensities of 25, 50 and 75% and 0 (control group). Finally, data were analyzed using split plot design in time with 10 replications for each treatment. Data analysis was performed by SAS software. Results showed that the effects of harvesting intensity, different years and their interactions on the forage production were significant at 1% level of probability, indicating that in different years, production rate varied with varying climate conditions. According to the results, an Allowable use of 25% is recommended for Stipa hohenckeriana in the study area. The recommended Allowable use can be used in determining the Allowable use for the study area and areas of similar climate, along with information from other plants.

Determination of Allowable use of the key species of rangelands is necessary to calculate the rangeland capacity. Actual rangeland capacity could be determined through having the exact values of this factor for rangeland species and the destruction of vegetation, soil and water loss on rangelands can be avoided. In this research, Artemisia aucheri, Bromus tomentellus, Kochia prostrata, Asperula glomerata and Buffonia koelzii were investigated as the key species of Arak Enjedan rangelands. A key area of one hectare was selected in Arak Enjedan rangelands and was fenced in the first year of the study. Then, 40 individuals were selected from each species and harvesting intensities of 25, 50, 75% and control treatment were implemented. Harvesting was done by a clipper monthly during grazing season for 4 years. The influence of harvesting was investigated in the second to fifth years through the study of changes in phenological characteristics, forage and seed production, vitality, and mortality and other characteristics of plant species. Results showed that increasing the harvesting intensity caused problems and decline of vital abilities of all species especially, As. glomerata and Br. tomentellus that are more palatable species. According to the results, an Allowable use of 25% is recommended for Br. tomentellus and As. Glomerata while for Ar. aucheri, Ko. prostrata and Bu. Koelzii an Allowable use of 50% was obtained with the least negative effects on plant characteristics. Results of the analysis of variance for forage production data were significant for all of the studied species in 1% level of probability.

Sheep fescue is one of the most important and effective grasses in the summer rangelands of Golestan Province. It is a key species in Saraliabad Gorgan rangelands, having an average production and relative consumption of 38.9 and 41.6% respectively. One of the important factors in determining grazing capacity is Allowable use of species. Due to lack of sufficient information in this regard, this research was performed in order to determine the Allowable use of sheep fescue during 2006 to 2011 at Saraliabad Gorgan rangelands. Experimental treatments in each block were included four harvesting intensities (25, 50, 75 percent and control or no harvesting). In each treatment, 10 species were assessed as replication. Results were analyzed by SAS software in split plot statistical design. The results of production showed that the effect of year, different harvesting intensities and their interactions was significant of (P<0.01). The effect of year showed that except first and second year, there was a significant difference between the mentioned years with the third and fourth year of the study. Also, the effect of harvesting treatments showed that only a harvesting of 75% had a negative impact on production. The interaction effect between year and treatments showed significant differences for control treatment despite no harvesting. Therefore, another factor was effective in reduction of the production and it was the rain. Results of the effects of harvesting intensity on freshness and mortality of sheep fescue showed that most of the species had acceptable freshness and vitality; also no mortality was recorded for the years and treatments. According to the results and with regard to other functions of Saraliabad Gorgan rangelands, an Allowable use of 60% is recommended for sheep fescue (Festuca ovina).

This research was aimed to determine the Allowable use of Bromus tomentellus, Festuca ovina and Stipa hohenackeriana in Firouzkooh rangeland during 2006 to 2010. Treatments included different harvesting intensities of 25%, 50%, 75% and control, performed on 40 medium-sized individuals of each species. Data were analyzed in a split plot in time design by SAS software and means were compared using Duncan. Results showed that the effects of treatment, year, and interaction effect of year*treatment were significant at 1% level of significance. In addition, the results of mean comparisons showed that the reduced forage yield was under the influence of harvesting intensities. In this regard, S. hohenackeriana and B. tomentellus were sensitive to drought while F. ovina was resistant to drought and more affected by the harvesting intensity. Our results clearly showed that a harvesting intensity of 25% and control treatment had no impact on the yield of species, leading to the reduced forage yield of the mentioned species. Therefore, an Allowable use of 50% is recommended.

Allowable use is one of the most important factors in determining grazing capacity. The present study was carried out to determine the Allowable use of Salsola laricina in Khoshkerood site of Saveh. In this research, four treatments including 25%, 50%, 75% harvesting and no harvesting (control) were compared during three years. The results showed that the effect of the year and interaction of different harvesting intensities and year were statistically significant at the level of one percent. In the first year of study, there was no significant difference among treatments; however, in the subsequent years, the effects of treatments were visible. So that the treatments had the most impact on the species in the last year. It was clear that there was not significant difference between the 25% harvesting intensity and control treatment. These treatments had the most forage production and also, there was not a significant difference between the other two treatments. The observations showed that the vitality of species in control treatment was less than that of 25% and 50% harvesting intensities, indicating that grazing can increase the plants vitality. Based on the AMMI analysis, the first interaction principal component (IPC1) was significant at the level of 1%, so that 98.2% of the sum of squares of the interaction could be expressed by IPC1. According to the biplot of the IPC1 and mean production, the lowest production rate and stability was recorded for the harvesting intensity of 75%. According to the results, it can be stated that a harvesting intensity of 25% guarantees the survival of S.laricina in this region with no negative effect on the vitality of Salsola laricina.

Picris strigosa is a valuable forage species in mountainous rangelands of Lorestan province, Iran, which produces suitable forage for sheep grazing. The aim of this study was to determine the Allowable use and grazing tolerance of this species. For this purpose, 50 individu-als of P. strigosa were selected in its typical habitat and marked for monitoring after applying four levels of harvesting intensities including control (0%), 25, 50, and 75% of the annual pro-duction during 2007–, 2011. Treatments were investigated by clipping and weighing method eve-ry month from May to July in vegetation period. The results showed a significant difference in terms of forage production between treatments (P≤, 0. 01). The highest and lowest forage produc-tion with average values of 42. 45g and 15. 23 g per plant were obtained in 0% harvesting rate (control) and 75% intensity rate, respectively. In other words, harvesting higher than 50% cou-pled with early grazing (April and May, in accordance with the local pattern and research method of this article) weakens the individuals. Continuation of this process also increases the mortality of the individuals (death of 30% of the stands at a harvest intensity rate of 75%). Due to the sen-sitivity of the species to early grazing, it was recommended that for such a dominant species, livestock should enter the pasture in early June. Maximum forage production in control and the fast reduction in forage production of 75% treatment emphasize that overgrazing of this species would completely eliminate it from the field. It was concluded that P. strigosa is sensitive to grazing and its sensitivity should be considered in rangeland management plans.

Maximum Allowable Depletion (MAD) by affecting on number of irrigation in growing season and irrigation use reduction can be used as a managerial tool to save water. The purpose of this study was to investigate the effect of MAD in irrigation interval, applied irrigation water, top and root growth of grass under subsurface drip irrigation system. Three irrigation treatments which were MAD equal to 40% (W1), 60% (W2), and 80% (W3) arranged in a randomized complete blocks statistical design with three replications in 2012 and 2013 in Isfahan University of Technology. The soil moisture was measured daily using Moisture Meter GMK-770S in the root zone depth of grass to manage irrigation. The apparent parameters and root parameters of grass were collected periodically. These parameters were analyzed by Duncan's multiple range test and the results showed that the irrigation treatments had no significant effect on the root growth parameters and top weight. In the depth of 0-13 cm the maximum root volumetric density and fresh and dry root weighted density were occurred in W1, W2 and W3 treatments, respectively. On the average, 80.14% of the mentioned parameters were in of 0-5 cm depth and 19.86% of them were in of 5-13 cm depth. The maximum (3.93 g/day) and minimum (3.21/day) dry biomass were observed in W1 and W3 treatments, respectively. Overall, the results indicated that although the increment of MAD to 80% in a clay-loam soil slightly decreased the shoot and root growth of mix sport grass under a subsurface drip irrigation system, it is a reasonable management solution with the aim of conserving water in the water shortage condition which had the least negative effect on apparent parameters of grass.