JOURNAL OF RANGELAND SCIENCE
Year:2018 | Volume:8 | Issue:4 |Papers Count:9

Mohammad Hossein Hakimi Meibody was born in 1963 in Meibod, Yazd province. He had gotten his diploma in Meibod and then for higher education, he had gone to Isfahan university and had exceeded direction of plant science for 4 years and graduated in 1989 with excellent grade. Then, he went to Tehran university and passed course of Plant Systematic in Biology department of faculty of science since 1996 with excellent grades; in this year (1996), he was accepted as a faculty member of Natural Resources department of Yazd University....

Grasslands are an important land cover and have a world-wide distribution with grassdominated communities from the equator to the polar tundra, from the sea level to the alpine zone, and occurring both naturally (such as tropical savannas and temperate steppes) and secondary (as in the cultural landscapes of Europe).

Climate is the most important factor of plants distribution in global and regional scale. Understanding the current distribution of vegetation cover and its interaction with climate regularity is important for predicting its future. In order to determine the effective climate factors in plant life-form in Polour rangelands in the Damavand summit (2400 to 4100 m above sea level), Iran, a study was carried out in May to July 2016. Climatic diagram for the average data of 2006-2016 was obtained by Emberger’ s method. Regression method was used for determining the relationships between altitude and climatic factors and the output was employed to draw isothermal and isohyet maps as well as phytoclimatic map using Arc GIS v. 10. 2 software. One square meter plots were established randomly in the stand area and vegetation cover data were collected. The results showed that the study area has cold arid climate with six months of drought period. The stepwise regression analysis between total vegetation cover and the climate factors showed that minimum temperature was the most effective variable (r=0. 875) that may influence the vegetation cover. The plant growth was started when environmental temperature copes with 10oC which was mid-April. Hence, the upland rangeland plants of Polour are grown in severe condition and the most life forms such as grass-shrubs need sufficient climatic components such as precipitation and temperature. Therefore, the range management approach can be achieved by limiting the grazing periods for two months to maintain the current vegetation cover which finds an opportunity to balance themselves with expressive climate changes.

Reduction of species diversity which is a significant threat to the earth has been found more important and has attracted attention among ecologists over recent years. This research was carried out to determine the relationships between plant species diversity indices and soil properties by multivariate regression methods in Jamilabad region, Baft, Kerman province, Iran in 2016. Different sites of natural ecosystem (including non-grazed, moderate grazed and over-grazed rangeland) and disturbed ecosystem [including rangelands plowed to Glycyrrhiza glabra root harvesting and abandoned dry land for ten years (Fallow) sites] were selected by fieldwork with the same climate, topography and geological factors. Abundance and canopy of species and soil samples (0-20 cm) were taken from each site contemporary for multivariate regression model and its validation. Determination of species diversity indices was done by PAST and BIO-DAP packages. Results revealed that regression models had higher accuracy in the disturbed ecosystem. In this regard, soil erodibility factor as well as soil total nitrogen explained 80% and 77% total variation in both Shannon-Wiener and Margarof indices, respectively. Results showed that even though the soil erodibility was excluded from the model, its components such as organic matter (in Berger-Parker index) had an important role in plant diversity. Therefore, soil erodibility or its components were strongly affected by plowing in the disturbed ecosystem and led to the formation of strong regression models between soil properties and species diversity indices.

Plants may induce small-scale heterogeneity in soil nutrients, forming fertile islands. However, this process may depend on plant spices, plant developmental stages and habitat conditions. Vegetation cover in arid and semi-arid regions is mostly in the form of plant patches and bare soil of inter-patch areas and this form of vegetation cover can be useful to study plants impact on soil to get applicable knowledge for predicting plants efficiency in restoration projects. This study was conducted in 2016 to study some soil properties in vegetation patches of some halophytes from Urmia Lake, Iran. The results showed that soil EC decreased from10. 32 (mS. cm-1) in bare soil to 4. 92 (mS. cm-1) in vegetated areas. Also, significant increase of soil pH and phosphorous content was observed in vegetation patches that were 8. 73 and 29. 61 (ppm) respectively in comparison with bare soil with 8. 51 and 12. 81 (ppm) patches. As vegetation patches caused a decrease in soil evaluated cations, the main shoot succulent halophytes of Salsola dendroides, S. nitraria, S. iberica and Halocnemum strobilaceum which can uptake these ions were selected to measure their above ground biomass and root tissues content of these salts; the results showed a significant difference between plant species in their salt uptake and accumulating ability. Halocnemum strobilaceum had higher amount of sodium and magnesium in shoots that were 9. 73 and 2. 96 (mg. kg-1), respectively. So, it had the most ability to absorb these salts by roots transporting them to shoots. In overall, these plants can improve soil nutrients and chemical conditions in their rhizosphere.

One of the major issues examined in the quantitative ecology is the spatial distribution pattern of plant species. Knowledge of the spatial distribution patterns is essential to measure the level of uniformity in the surrounding environment, plant reproduction, and distribution of the seedlings, plant behavioral patterns, coexistence, allelopathic relations, and competition. Therefore, the aim of the present research is to select suitable indicators to determine the spatial distribution of three plant species namely Seidlitzia rosmarinus, Cornulaca monacantha and Stipagrostis plumosa and to evaluate their accuracy in arid and semi-arid rangelands of Birjand. Sampling was taken in the key area of each site with four transects of 100 m using quadrates (with their size proportional to the vegetative form of the plant species) by a stratified random sampling technique in 2014-2015. At each point, the distance from the nearest neighbors, the closest species and species richness were recorded. S. plumosa and S. rosmarinus produced the largest and smallest values as 6. 6 and 0. 24 plant/m2, respectively. Our results suggested that S. rosmarinus, C. monacantha and S. plumosa follow regular and uniform distribution patterns. The results of the statistical analysis also showed the positive binomial distribution for these species, which further confirm our finding. In total, it has been found that quadratic indicators provide more accurate results regarding plant species distribution patterns as compared with the distance indicators.

Knowledge of the relationships between biotic components of rangeland ecosystem i. e. herbivores and plants is important for range managers. In order to study herbivorse grazing intensity on plant species diversity, an experiment was conductef using fuor grazing treatments in darrehshar rangelands, Ilam province in 2015. Plant species data were taken based on a randomized-systematic sampling method. Numerical values of diversity, richness and evenness indices were calculated using PAST as well as Ecological Methodology softwares. Significant differences were observed between grazing treatments for all diversity indices, except Camargo evenness index (P ≤ 0. 05). The highest values of Simpson and Shannon diversity indices as 0. 916 and 3. 96 respectively were obtained in the ungrazed site and the lowest values of those indices as 0. 87 and 3. 36 were obtained in the heavy grazing treatment. Ungrazed site had 6. 4 ٪ and 12. 2 ٪ higher diversity than the heavily grazed site. The highest values of Margalef and Menhinick richness as 4. 66 and 0. 91 were obtaned in the moderately grazed site. The lowest values of those indices as 2. 71 and 0. 598 were occurred in the heavy grazing site. Margalef and Menhinick indices values in the moderately grazed site were 36. 8 ٪ and 46% higher than those in the heavy grazing treatment, respectively. The highest modified and Smith & Wilson evenness indices with average values of 0. 163 and 0. 272 were obtained in the heavy grazing site and the lowest values with the average of 0. 101 and 0. 178 were in the ungrazed area. This study concludes that heavy grazing intensity can adversely affect plant species diversity in semisteppe rangelands.

Pubescent wheatgrass (Agropyron trichophorum (Link) Richt. ) is growing in semiarid regions of Iran at altitude of 500 to 2000 m. Among different grasses growing in Iran, A. trichophorum is relatively resistant to grazing and defoliation as compared to other species of Agropyron genus which are dominant in the most summer rangelands. In Emam Gholi protected summer rangelands, Ghochan, Khorasan province, Iran, A. trichophorum as a dominant grass was selected for our study, and was subjected to a series of defoliation treatments. Forty eight quadrates of 0. 5 m2 were established in two macro-plots and subjected to one, two, three, and four weekly interval clipping started in May 6, 2016 in vegetative stage and other treatments of once clipping started in May 6, May 19, June 3, and a control treatment was clipped only once in July 15. Floral stalks of A. trichophorum were counted before clipping. Then, quadrates were clipped to the ground surface, air dried and weighed for different treatments. Using ANOVA, the responses to frequent clipping showed that there were no significant differences in daily, current, primary, and total production of A. trichophorum (p>0. 05) which may be due to the reservation of carbohydrate in roots and base of this grass after 15 years of protection. Low slope of sigmoid curve for weight of clipped plants also confirmed the resistibility of this species to defoliation, but as the frequency of clippings were increased, the number of floral stalks was decreased showing an exponential model (p<0. 0). To find the allowable use of A. trichophorum, further years of research will be required to evaluate the responses to defoliation in different locations.

Bush encroachment is an increase in woody plant density typically resulting in impenetrable thickets, suppressing palatable grasses and herbs. Moreover, bush encroachment is a globally observed phenomenon. Besides, increasing the density of unpalatable shrubs and trees has reduced the carrying capacity and threatens the sustainability of grazing animal production, especially in arid and semi-arid grasslands and savannas around the world. Bush encroachment is a serious environmental and economic problem. In addition, biodiversity, wildlife habitat and nutrient cycling (rates, magnitude, seasonability and spatially patterns) are affected by these changes in vegetation. Although the increases in woody plant abundance have widely noted, such elements as rates, dynamics, spatial patterns and approximation have not been well documented. However, land use practices such as increased grazing pressure and decreased fire frequency have been associated with shifts from grass to woody plant domination. The pastoralists have been using the traditional grazing management in order to cope up with the relatively arid conditions of the environment, prevent from overgrazing and ensure the sustainability of resource base.