نشریه خشک بوم
سال دوم شماره 1 (بهار و تابستان 1391)

Determing of daily metabolism energy required livestock rangelands in different climatic zone، in order to calculate grazing capacity is essential. In this regard; daily metabolism energy required in Balochi breed sheep and Nadoshan breed goat in Nadoshan rangelands were studied. For this purpose، according to the average values ​​of forage quality indices in plant species and their proportion in the composition of rangeland vegetation in different growth stages، metabolism energy value in 1Kg of dry matter for livestock grazing rangelands was estimated. Considering of daily metabolism energy required in Balochi breed sheep and Nadoshan breed goat، amount of forage which supplies animal requirements in different stages of growth in this region، were estimated. Daily requirement of sheep، ram and lambs of Balochi breed sheep and animal classes of Nadoshan breed goat based on metabolism energy، according to the MAFF equation proposed (1984) in the state of maintenance and livestock grazing in rangeland، and considering the physical characteristics of the rangelands، intervals of animal drinking places، plants density and 40% additive coefficient، were calculated 8. 19، 14. 66، 8. 29 and 5. 90، 6. 0، 5. 45 Mj، respectively. According to the results، amount of forage required to provide the daily requirements of sheep، ram and lamb of Balochi breed sheep considering the forage quality of rangelands in the initial stages of growth respectively، is 0. 92، 1. 64 and 0. 93; in the middle of stages growth respectively، is 1. 06، 1. 89 and 1. 07، and in the final stages of growth is 1. 19، 2. 13 and 1. 21 Kg of dry forage. Thus، the amount of forage required to provide the daily requirements animal classes of Nadoshan breed goat considering the forage quality of rangelands in the initial stages of growth is 0. 66، 0. 67 and 0. 61، respectively; in the middle of stages growth is 0. 76، 0. 77 and 0. 70، respectively and in the final stages of growth is 0. 86، 0. 87 and 0. 79 Kg of dry forage. This implies that time of grazing affects on the daily requirements of livestock and daily requirement of livestock must be determined according to forage quality. It is obvious that the quality of forage plants changes depending to the environmental condition of year، but since the determing forage quality is expensive، the obtained results can be used to estimate daily requirement of livestock in different years.

Seed germination as the most important plant development stages can be frequently affected by environmental stress including drought and salinity. The seeds and/or fruits of many species in desert habitats have an external mucilage layer that can be increased water holding capacity of seeds under water stress condition. To evaluate the role of mucilage in enhancing of drought tolerance of Plantago ovata Forsk. and Plantago major L. in seed germination and early growth stages، a completely randomized experiment was conducted in a factorial arrangement with four replications. Plant species (P. ovata، P. major)، drought stress levels (0، -5، -9، - 14. 5، -21 MPa) and seed type (with mucilage، and without mucilage) were considered as first، second and third factors، respectively. Different variables including germination percentage، rate of germination، stem as well as root length were measured. Results indicate that with increasing drought stress، germination and seedling growth of two plant species were significantly decreased. Seeds with mucilage were less affected by drought stress compared to the seeds without mucilage. Germination and early growth of the two plant species differ in their sensitivity to drought stress and P. major was more affected by drought stress. Overall، results indicate that mucilage can improveseed germination of both plant species under drought stress condition. However، the ability of mucilage in improving seed germination depends on type of plant species and amount of seeds mucilage.

Vegetation is an important component of global ecosystems. Determining of the Earth''s vegetation cover is important to understand land-atmosphere interactions and their effects on climate، soil erosion، drought and natural resources management. The main objective of this study is to estimate vegetation fraction (Fv) using various vegetation indices. First، vegetation fraction was collected in 52 random sample plots in July 2009. Some vegetation indices (ARVI، DVI، EVI، SAVI، SAVI2، TSAVI، SARVI، WDVI،NDVI، PVI، IPVI، GEMI، MSAVI1، MSAVI2، OSAVI، SR، MSR) and ALOS (AVNIR2) imagery (June 2009) were used to find the most suitable index for estimating of Fv. Validation of the obtained results have been done using two methods of Cross-Validation and، dividing measured samples to calibration and validation data. Result revealed that selecting the calibration and validation data randomly، leads to different results. Generally، among all studied vegetation indices، those VIs use soil line coefficient، have higher R2 (>0. 63) and lower RMSE (<3%).

The effect of arbuscular mycorrhizae and humic acid on water use efficiency and physiological growth indices of maize was studied at three water regimes. The research was carried out in an farm experiment using a split plot factorial based randomized complete block dasign with three replications. Main plot included three levels of under water deficit condition (100%FC، 66%FC، and 33%FC); and sub plot included two species of mycorrhizae (M1: Glomus mosseae، M2: Glomus intraradices and M0: non application of mycorrhizae) and two levels of humic acid. (application of humic acid (H1) non application of humic acid (H0)). Results showed that the application of arbuscular mycorrhizae، humic acid، and normal condition (no water deficit)، increased leaf area index، crop growth rate، relative growth rate and total dry matter. The above mentioned characteristics were decreased under water deficit condition، non application of mycorrhizae and non application of humic acid. Application of mycorrhizae and humic acid significantly increased water use efficiency. The intraction effects of water deficit and mycorrhizae، was statisticaly significant. The highest water use efficiency (2-5 Kg/m3) occured under water deficit condition (33% FC) and Glomus mosseae species. The lowest amount of water use efficiency (1. 31 Kg/m3) observed with non application of mycorrhizae under normal condition (no water deficit).

Understanding the vegetation dynamics of arid rangelands is a prerequisite for their proper management. Water stress is the most crucial environmental stress for vegetation in this region and long-term monitoring experiments are an important tool to investigate rainfall and temperature variability impact. In this research، the reactions of the dominant plant species yield to meteorological variables such as rainfall and high temperature were studied at steppe rangeland in Ernan region during the period of 2000 to 2008. For this purpose، it was selected four dominant species and their forage production were measured every year with clipping and weighting method along four permanent lines transect in 60 random plots (2m × 2m). Meteorological data were collected from nearby climatological station. Relationship between main meteorological gradients and forage annual yield، analyzed by redundancy analysis. According to this result، total annual yield and annual yield of Artemisia sieberi and Salsola tomentosa had significant correlation with axis 1 (r = - 0. 93، r =- 0. 86 and r = - 0. 92 (and influenced by rainfall in December-March period and maximum temperature in July. In addition، forage yield of Salsola tomentosa is influenced by rainfall in the previaus year. Species yield of Ephedra strobilacea and Stipa barbata showed high correlation with axis 2 (r = 0. 64 and r = 0. 72 (and influenced by rainfall in December-March، April-June periods and maximum temperature in April. These meteorological gradients were related closely to the first two canonical axes، and accounted for 94. 9% of the species–environment relationship in the study sites.

Drought as one of the environmental stresses، is the most significant factor restricting plant growth and crop production. Drought stress can results in disruption of water potential gradients، turgor loss، membrane integrity disruption and protein denaturation. In addition، it inhibits the photochemical activities. Potato is an important plant in agriculture that has an average sensitivity on salt and a high sensitivity on draught. In this study، potato’s residence against draught was investigated in two cultivars of Kenebeck and Concord under in vitro culture conditions. Potato cultivars were grown in MS medium containing 50 μM Silver Thiosulfate (STS) and they were transferred to liquid medium of MS after rooting then were treated for 14 days with concentration of 0، 2 and 4 percent of PEG (MW 6000). After four weeks post treatment، physiological factors such as fresh and dry weight، content of photosynthesis pigments (total chlorophyll and carotenoid) were measured in order to identify resistant and sensitive plants against water stress. Results indicated that Kenebec showed lower reduction in the above-mentioned factors under stress conditions compared to Concord. In order to study mechanisms of resistance against draught in these two types، proline and soluble carbohydrate in shoot were investigated. According to results، with increasing، PEG concentration proline and the soluble carbohydrate increase significantly in the shoots Kenebec. Proline concentration in Concord showed an increase only 2% PEG treatment. In comparison to control plants، soluble carbohydrates in Concord showed no significant increase

Soil salinity and sodicity are two aspects of land degradation، especially in arid and semi-arid regions. This study focused on the role of different amendments on physical and chemical properties of a saline sodic soil، including EC، ESP، organic carbon، bulk density، saturated percent، field capacity and available water content. The experiments were conducted as factorial based on completely randomized design using six soil amendments، including control (C)، cattle manure (M)، pistachio residue (P)، gypsum (G)، M+G and P+G، moreover، two water treatments (with and without sulfuric acid) each at three replicates. The experiments were carried out under laboratory condition using soil column. Four intermittent leaching steps were applied with one month intervals and one pore volume. Results showed that at different treatments، final EC and ESP values compared to those of the initial soil decreased 66. 2- 84. 9% and 73. 6-90. 6%، respectively. Since the soil was calcareous، the final EC and ESP of soil compared to the initial soil decreased 80 and 84. 2%، respectively because of leaching. In presence and absence of sulfuric acid، the highest efficiency in reduction of EC was found for gypsum and pistachio residue. In addition، pistachio residue and cattle manure exhibited higher and less efficiencies in reduction of ESP، respectively. The finally، ESP of the treated soils was reduced to less than 11%، for all of the treatments. Furthermore، the application of organic matters led to improvement of soil physical properties. The results indicated that sulfuric acid had no significant influence on soil bulk density. Control and gypsum treatments showed the least amounts of available water. It was also found that the combined application of organic matters with gypsum compared to their exclusive application had more significant impact on available water. The findings of this research reveal the importance of pistachio residue in ameliorating saline sodic soil under leaching condition.