Determination of allowable use for Stipa hohenackerian in semi-steppe rangelands of Iran

Abstract

Current research was carried out in selected sites of semi-steppe region including Arshagh (Ardebil), Firoozkooh (Tehran), Kordan (Alborz) and Jashloobar (Semnan). Stipa hohenackerian is a key and palatable species which has a considerable portion in rangeland yield. For this purpose, 40 similar species of Stipa hohenackerian were selected in each site. Selected species were exposed to different harvesting intensities of 25, 50 and 75 and 0% as control group. Data were analyzed by SPSS and MSTATC and Duncan’s Multiple Range Test was used for mean comparisons. According to the results, no significant differences were recorded for 25 and 50% harvesting intensities in terms of studied traits but a harvesting intensity of 75% negatively affected Stipa hohenackerian. Consequently, a harvesting intensity of 25-50% is recommended as the best allowable use for Stipa hohenackeriana in this vegetative region and other similar areas.

Introduction

Rangelands are one of the most important and most valuable national resources of Iran and form a large part (over 52%) of the country. Other services of the rangelands including pharmaceutical, industrial, and food products, soil conservation, control and increased groundwater storage, fresh air, increased relative humidity, regulation of the water cycle, provide forage for livestock, preservation of plant and animal genetic resources as well as wildlife are nationally important (Fazilati et al. 1965). It is noteworthy to state that providing forage for grazing livestock is the main use of rangelands while forage quantity and quality are inadequate to provide forage needed for livestock due to overutilization (Gharedaghi and Fazel Najafaabadi, 2000).

Despite the major role of determining allowable use of important species in improvement and restoration projects, soil erosion, calculation of available forage to livestock and also calculation of grazing capacity of rangeland and sustainability of desirable species resulted in economic prosperity, unfortunately, no systematic and adequate research has been done in this regard. This research was aimed to determine the allowable use of Stipa hohenackeriana as a key range species in semi-steppe rangelands of the country. The main question of the study was to what extent of harvesting could be tolerated by this species. (Smith et al. 2007) introduced range condition as one of the most important criteria in determining the level of range utilization, and stated that allowable use of the rangelands with poor condition would result in rangeland improvement. Also, allowable use should be considered higher in rangelands with good condition while it should be less in poor rangelands. (Arzani, 2010) stated that allowable use percentage varied depending on plant species. If allowable use is calculated for desireble species, it can be used for all plant species. ( Reece et al. 2001) have developed a theory on allowable use which is expressed as half harvesting and half remaining and according to it, the livestock are permitted to graze a distinct percentage of available forage that its rate is typically 50%. (Amiri, 2008) estimated an allowable use of 20 to 40 percent in rangelands of Semirom, Isfahan province. Also (Zhao and lin, 2007) in studies of some range species, stated that a number of range species could not tolerate the pressure of forage harvesting, and therefore are unable to offset declining production resulted from cutting shoots. Sharifi and (Akbarzadeh, 2010) studied the changesError! Reference source not found. of vegetation under exclosure and grazing conditions in rangelands of Ardebil (Arshagh site), and reported that species of Stipa hohenackeriana showed a considerable growth during exclosure. (Ganskcopp, 1988) investigated the effect of harvesting intensities on changes of forage yield of Stipa thurberiana at Range Research Station of Oregon and concluded that this species was sensitive to intense harvesting in vegetative stage and only in the case of light harvesting, it could be used multiple times during the growing season. (Fulstone, 2009) in his studies on grazing management of Missouri rangelannds, reported the allowable use of key species of Stipa californica and Stipa nevadensis to be 50 and 55%, respectively. As was mentioned, the determination of allowable use is dependent on the studies in place and its percentage will vary depending on the species. For this purpose, the project of determining the allowable use of Stipa hohenackerian in reference sites of semi-steppe regions was carried out for 5 years.

Material and methods Sampling Characteristics of the selected sites of semi-steppe region are summarized in Table 1. In each of the selected sites, Stipa hohenackeriana was evaluated as a key species. Therefore, 40 similar individuals were selected at the beginning of the grazing season in each region and were marked by wooden labels. These lables remained stable and were protected from livestock grazing during four years.

In this research, grazing simulation was performed in which different harvesting intensities of 25, 50, 75% and 0 (as control) were investigated as treatments with 10 replications for each treatment. Harvesting was done with clippers. Since forage harvesting was commenced from the begining to the end of livestock grazing, therefore, the number of days that species were normally grazed by livestock was calculated in each region and then it was divided by 30 to get the number of harvestsing. Residual forage and total forage of the control treatment were harvested when species were completely dry. Thereby, total yield was calculated in each year.

Statistical analysis

A split plot design in time with 10 replications was used, and data analysis was performed with SAS software. Mean comparisons were done by Duncan's Multiple Range Test. Interactions between treatments were tested by AMMI model, using IRRISTAT software. Other items investigated in this study included assessment of plant mortality, height, seed production and meteorological data.

Source: innspub.net