مجله مرتع
سال هشتم شماره 2 (پیاپی 30، تابستان 1393)

This study aimed to evaluate the Artificial Neural Network (ANN) model potential to predict the spatial distribution of plant species. The vegetation data as well as topography, climate, geology and soil data were collected. A randomized-systematic method was used to collect the vegetation data. Three parallel transects with 150 meters lengths were established in each sampling unit, and the vegetation data were collected from 15 quadrates placed with intervals of 10 meters. Various geo-statistical methods were used to produce environmental maps, and ANN technique was used to predict the potential vegetation habitats. The produced model was assessed using Kappa coefficient. According to the results, the study area was identified as a good habitat for species such as Agropyron intermedium, Thymus kotschyanus, Astragalus gossypinus and Stipa barbata with Kappa coefficient of 0.95, 0.84, 0.83 and 0.7 respectively. The results indicated that ANN technique has good potential to predict the spatial distribution of range species. According to the results, the accuracy of the model prediction for the species of all four studied habitats was more than 95%. This indicates that the potential habitat maps of plant species can be produced appropriately by using the selected soil and climatic variables in a plant distribution model.

This study aimed to evaluate the effects of various grazing intensities including non-grazing (as control site), moderate grazing and heavy grazing on aboveground and belowground biomass of Bromus tomentellus in Bijar protected area- Kordestan province. Regression techniques were used to assess the relationships of aboveground and belowground biomass of the species, and one-way ANOVA and Duncan's test were used to compare all the treatments. According to the results, there was a linear relationship between aboveground and underground biomass in the different treatments. Increasing grazing intensity leads to a significant reduction in aboveground, belowground and total biomass of the plant species. The species biomass in moderatly and heavily grazed sites declined 37% and 80% respectively in compare with the control. ‏‏‏‏‏‏The average total biomass in the control, moderately and heavily grazed sites were estimated 839, 488.75 and 132.88 kg/ha respectively. The relative contribution of aboveground and belowground biomass of the species were decreased and increased respectively as the grazing intensities were increased. The relative contribution of aboveground biomass in the control, moderately and heavily grazed sites were 54.97%, 61.42% and 64.34% respectively. The relative contribution of belowground biomass in the control, moderately and heavily grazed sites were 45.03%, 38.58% and 35.66% respectively. The results of this study highlight the importance of controlling the grazing intensities to prevent soil erosion and losing the valuable plant species.

This study was conducted to evaluate the ability of Sample Point software compared with Ocular estimation (O.E.) as a traditional method for estimating soil cover in Semi-steppe rangelands of Arjan area in the west part of Fars province. Estimation of soil cover attributes including canopy cover, litter, stone and bare soils were performed using ocular estimation (O.E.). Simultaneously, the digital images of each plot were obtained using a Canon camera with 8-megapixel quality installed 2 meters height above the sampling plots. Image processing was carried out in Sample Point software version 1.65. The times consumed in different parts of sampling process were also recorded. The results demonstrated that all the soil cover attributes in the two different methods (O.E. and S.P.) were significantly correlated (P≤0.01). The percentage of measured canopy cover, litter, stone cover and bare soil were not significantly different between the two sampling methods (P≤0.05). The time of field work and the overall time which spent in O.E. method was more than S.P. sampling approach. Nevertheless, the lab analysis time in S.P. method was greater than the O.E. method (p≤0.01). Generally; the result of this research indicated that digital imaging techniques can be used by Sample Point software to estimate soil cover appropriately. We therefore introduce and recommend this technique as a practical, easy, inexpensive and repeating method to evaluate the soil cover of Semi-steppe rangelands.

This study was conducted to investigate the effects of different treats of gamma ray doses including 15, 20, 30, 50, 100 and 150 gray, on Bromus inermis and B. tomentellus seeds. The efficiency of gamma ray to stimulate the growth and increasing the plant tolerance and physiological stability in daily temperature and water supply fluctuations was evaluated by measuring some parameters including total protein, proline and chlorophyll content. A completely random design was used to collect the data from irradiated seeds that were sown in greenhouse condition. The results showed that the 15 gray doses caused the most positive effects on chlorophyll content and physiological condition of B. inermis. The most positive effect on B. tomentellus physiological conditions was observed in 30 gray treatment. Using 100 and 150 gray doses treatments decreased the seed growth of the both species through its negative effects on photosynthetic rate and evapotranspiration of the species. Soluble protein content in the both species increased as gamma ray intensity increased. Proline concentration of B. inermis seeds was also decreased significantly (p<0.01) after using gamma ray treatments. The proline content of B. inermis seeds in control and 15 gray treatments did not varied significantly but it was decreased in higher gamma ray intensities (from 20 gray intensities to higher doses). The results indicated that the gamma ray application had no significant effects on proline content of B. tomentellus. In conclusion, the 15 gray treat for B.inermis and 30 gray treat for B. tomentellus can enhance the seed growth of the both species.

Identification of rangeland species is an essential step in range management. This study aimed to study the flora, and investigate on the relationships of species distribution with climatic factors in Iranshahr region rangelands. Taxonomic studies were conducted to provide the plant floristic list. Plants life forms were determined using Raunkiaer categories. Twenty seven climate variables were collected from 12 synoptic stations close to the study area. Principal component analysis was used to identify the most effective climatic variables on the plant species distribution. According to the results, 175 plant species from 136 genera and 44 families were identified in the study area. Gramineae, Compositae, Papilionaceae and Chenopodiaceae contained the most plant species in the flora respectively. Results indicated that 25.72% of the plant species were Therophytes, 25.14% Hemicryptophytes, 24.57% Phanerophytes, 20.57% Chamaephytes and 4% Geophytes. According to the chrological analysis, 28.57% of the studied plant species belonged to Sahara-Sindian region, 24% Irano-Turanian /Sahara-Sindian, 20% Irano-Turanian, and 4% cosmopolitan elements. Results showed that the study area is located in Sahara-Sindian region. PCA results also indicated that the average of maximum relative humidity, number of days with thunderstorm, number of days with precipitation and maximum daily precipitation had significant effects on the plant species distribution.

Various methods have been proposed for determining rangeland suitability from different aspects. Although FAO’s method is the most widespread approach for determining rangeland suitability, it is very time consuming, not convenient and field and laboratory data hungry. Accordingly, it was necessary to devise a scientific, simple and cost-effective guideline for range mangers to assess rangeland suitability. The new proposed guideline for assessing range suitability from animal grazing aspect consists of three criteria of vegetation (20 points), water (15points), and soil (15points). This study aimed to evaluate this guideline in Hendovan mountainous region. The non-parametric Wilcoxon Test was used to compare the results obtained from this guideline with the findings gained by the FAO’s method. According to the results, forage production and the sensitivity of soil to erosion was identified as the most limiting factor for the grazing suitability in the both models. Moreover, there was not any significant difference between the two methods regarding the levels of suitability. Therefore, it can be concluded that the proposed guideline is an appropriate method for recognizing and dividing the suitable and unsuitable areas for animal grazing. Furthermore, the cost-effectiveness, time saving, simplicity and efficiency of the proposed model are remarkable in comparison with FAO’s method. This guideline will assist range experts in making "rangeland management plans" to achieve a sound grazing management.

This study aimed to investigate the feasibility of using critical area (village) as a basis in the assessment of rangeland degradation with an emphasis on the composition and diversity of vegetation in Southeastern Sabalan. The vegetation and soil data were collected from the sites with high, moderate and low grazing pressure around three critical areas of Alvares, Latran and Vargasaran. One square meter plots along 100 meters transect was used to collect the data in each site. The species composition, diversity and evenness indices in the sites were determined and analysis of variance and mean comparison tests were then used to compare these characteristics. Cluster analysis and principal components analysis was also used to summarize and analyze the data. Results showed that unpalatable species (class III species) were dominant (more than 56 percent) in the heavily grazed sites. The production, density and canopy cover of plant species varied significantly in the sites with various distances from Vargasaran and Alvares villages, but there was no changes along this gradient in Latran village (P<0.05). Production and canopy cover of the species along the studied gradient varied significantly (P<0.05) but diversity and evenness indices did not show any particular trend. Cluster analysis could not separate sites with similar grazing pressure. According to the result, the defined degradation gradient cannot be used as a basis for rangeland assessment due to the distribution of critical areas in the studied area. Repeating similar studies in Sabaln rangelands can clarify if this framework is an appropriate basis for rangeland assessment or not.

Vegetation and soil characteristics are highly affected by herbivores and exploring these relationships is essential for rangeland management. This study aimed to compare the plant composition and physico-chemical soil properties under livestock (sheep and goat) and wildlife (deer) grazing regimes in Kalmand-Bahadoran plain rangelands of Yazd province. A random-systematic method was used to collect the data from 10 randomly established transects with 100¬ meters lengths and 3 plots of 2 m2 were placed on each transect. CANOCO4 software was used to analyze the collected data. According to the results, livestock and wildlife grazing were identified as the most responsible factors, describing the sites places along the first axis of Redundancy analysis (RDA) plot. The frequency of some species such as Colchicum kotschyi, Stachys inflata, Iris songarica, Lolium rigidum, Boissiera squarrosa, Noaeae mucronata, Astragalus sp. and also stone percentage increased in the sites grazed by wildlifes. On the other hand, the frequency of Echinops sp., Scorzonera sp., Launaea acantodes, Zygophyllum eurypterum, Stipa barbata, Peganum harmala, litter and bare soil percentage raised in the sites grazed by livestock. livestock and wildlife grazing did not have any significant effects on the frequency of Artemisia sieberi as a dominant species, Lactuca sp. and Cousinia sp. Soil texture, soil moisture and soil organic carbon content did not varied significantly in the two studied areas but some soil characteristics such as EC, pH, TNV and soil bulk density were higher in the sites grazed by livestock than the other site. Wildlife grazing resulted to some positive changes in soil characteristics and vegetation composition, therefore it can be concluded that similar management practices experienced in sites grazed by wildlife can enhance the range condition of other sites.

Monitoring and interpreting vegetqation changes to various ecological condition and management practices is required to achieve sustainable management in rangeland ecosystems. This study aimed to identify indicator species of grazing impacts in thirty one range places with relatively homogeneous ecological conditions and various grazing intensities in Semi-Steppe rangelands of Feridan- Isfahan. Plant species frequencies in each range site were studied along four perpendiculars 30 meters transects using step point method. Integrated System for plant Dynamics (ISPD) software was used to conduct the ِDetrended Corresponding Analysis (DCA) and Centered Principal Component Analysis (CPCA) on the frequency data. Once it was confirmed that the range places were well distributed along first axis of CPCA, the species frequencies were fitted by Gaussian curves against the first axis of ordination plot. According to the regression analysis results, the species with D-Statistic more than 0. 5 and correlation coefficient more than 0. 3 were identified as indicator species of grazing impacts. Five out of 34 plant species were quantitatively identified as indicators of grazing impact. Agropyron trichophorum was identified as decreaser, Hordeum bulbosum and Acanthophyllum microcephalum as increasers and Astragalus verus and Cousinia bachtiarica as invaders in the study area. Evaluating the frequency of these indicator species can assist range managers to track any positive or negative changes in grazing values of the vegetation compositions in the study area. They can adapt their management strategies using assessment of these indicator species accordingly.