Animal Unit of Sheep (Zel Breed) Grazing in Mazandaran Grasslands in Iran

Animal unit equivalents (AUEs), provide a means of summarising grazing capacity, calculating stocking rates and other stocking variables (Scarnecchia, 1990). Animal units (AU) are often defined in relation to the dominant animal type in an area In Iran there are 27 sheep breeds which are classified into three main body size classes, namely: small, medium and large. The objective of this experiment was to define animal units, animal and forage requirements for sheep grazing in Mozandaran grasslands

Climatic condition effects on the components of plant diversity in the western Iran grasslands using multiplicative partitioning methods

This study aimed to investigate the effects of different climatic conditions (arid vs. semi-arid) on patterns of species richness and plant diversity as well as plant composition in two over-grazed regions. The regions were located in the west of Iran, closed to each other and different in climatic conditions. Based on the aridity index of De Martonne climate classification, Rika (I = 9.94) and Dalab (I = 18.54) were categorized as arid and semi-arid regions, respectively. In each region, we collected plant vegetation data from a nested sampling design consisted of local (80 plots) and regional (8 sites) scales. Patterns of plant diversity and species richness in each region, and similarity of plant composition between the two regions were analyzed using multiplicative partitioning methods, species richness estimator and cluster analysis, respectively. The results showed that diversity components in all scales had significant difference with their expected values (p <0.000) resulted in non-random distribution of plant species among and within scales. In addition, the results showed that species richness in Rika region (arid, 89 species) was greater than Dalab region (semi-arid, 76 species). The results of cluster analysis suggested that Rika and Dalab regions had different plant species compositions. Based on our results, the role of seed dispersal might be more prominent in smaller scales (plot and sites) compared to region scale, since the highest possible amount of β-diversity was occurred between regions. Our results suggested that plant diversity in the largest scale (region) had the highest amount of diversity components where the rangeland manager should attend on this scale for conservation of plant diversity

Changes in soil organic matter driven by shifts in co-dominant plant species in a grassland

International audienceGlobally, grassland soils, if managed properly, are important for the sake of carbon sequestration. The quality and quantity of soil organic carbon is probably influenced by vegetation traits such as composition and plant species. We determined the influence of vegetation composition and co-dominant species on soil organic carbon in two Prangus uloptera stands. The stands situated at close proximity were identified in a Prangos uloptera community in north-western Iran. Both stands shared similar dominant plant species with the same physiographical and climatological characteristics, but differed in their co-dominant plant species. To compare soil organic matter (SOM) parameters, soil samples from each stand were collected from depths of 0-15 cm and 15-30 cm. The results showed that SOM had spatial variation which was probably affected by the plant species. The highest values of total C, Total N, POM-C, POM-N, microaggregates, C in macroaggregates and C in microaggregates in the upper soil layer occurred in the stand with the highest cover of Astragalus microcephalus and Acanthophyllum microcephalum. It is suggested that, in conservation projects based on higher carbon sequestration, the plant species with more incorporation of carbon content into soil should be identified and used more widely

Role of Different Shrubs in Soil Seed Bank Conservation in Different Climates of Iran

Shrubs often produce positive effects on understory soil seed bank (SSB) characteristics. However, the effect of shrubs on SSB could be variable in different habitats depending on the climate and the type of shrub. In this study, the effect of Crataegus pseudomelanicarpa (humid areas, northern Iran), Onobrychis cornuta, Berberis integerrima and Juniperus sabina (sub alpine areas, northern Iran) and, Astragalus myriacanthus and Acantholimon spinosum (semi-arid areas, central Iran) on SSB characteristics was studied. Soil samples were collected under the canopy of shrubs and the control (out of canopies) from 0-5 cm and 5-10 cm depths by auger and seed germination was monitored in the greenhouse. The results showed that generally all shrub species in different climates had a significant positive influence on SSB density and diversity in all climates. In comparison between subalpine shrubs, density of the SSB was lowest under J. sabina and highest in the control area, but did not differ between B. integerrima and O. cornuta. In comparison between semi-arid shrubs, the mean density of SSBs under A. myriacanthus (904 seeds/m2 ) was significantly higher than that of A. spinosum (361 seeds/m2 ). This study revealed that the extent to which vegetation affected SSB characteristics depends on the presence and species of shrubs in the area

Comparison of soil seed banks of habitats distributed along an altitudinal gradient in northern Iran

International audienceIn this study we investigated the variations in soil seed banks along an altitudinal gradient in the Alborz mountains, Iran, covering three habitats from lower to upper altitudes: forest, forest-subalpine grassland ecotone and subalpine meadow. In each habitat from 1850 to 2400 m, 20 quadrats were established along four transects, and the above-ground vegetation and the germinable seed banks were determined. Results show that the similarity between seed bank and vegetation was lowest in the ecotone located at intermediate altitudes. Together with the contrasting highest density and species diversity of seeds at these altitudes, the ecotonal role of this habitat was confirmed. We found evidence that lower altitudes could act as storage for seeds of some species growing at higher altitudes; the role of the ecotone was more prominent as a reserve for the meadow plant seeds than the role of the forest as a reserve for seeds of the meadow and ecotone habitats. Soil seed banks, particularly from the ecotone, can be used for restoring vegetation in some degraded sites

modeling potential habitats for pergularia tomentosa using maximum entropy model and effect of environmental variables on its quantitative characteristics in arid rangelands southeastern iran

Predicting the potential habitat of plants in arid regions, especially for medicinal ones, is very important. Although Pergularia tomentosa is a key species for medicinal purposes, it appears in very low density in the arid rangelands of Iran, needing an urgent ecological attention. In this study, we modeled and predicted the potential habitat of P. tomentosa using maximum entropy, and the effects of environmental factors (geology, geomorphology, altitude, and soil properties) on some characteristics of the species were determined. The results showed that P. tomentosa was absent in igneous formation while it appeared in conglomerate formation. In addition, among geomorphological units, the best quantitative characteristics of P. tomentosa was belonged to the conglomerate formation-small hill area (plant aerial parts = 57.63 and root length = 30.68 cm) with the highest electrical conductivity, silt, and CaCO3 content. Conversely, the species was not found in the mountainous area with igneous formation. Moreover, plant density, length of roots, and aerial parts of the species were negatively correlated with soil sand, while positive correlation was observed with CaCO3, EC, potassium, and silt content. The maximum entropy was found to be a reliable method (ROC = 0.91) for predicting suitable habitats for P. tomentosa. These results suggest that in evaluating the plant's habitat suitability in arid regions, contrary to the importance of the topography, some environmental variables such as geomorphology and geology can play the main role in rangeland plants' habitat suitability

Improvement of the seedling emergence method in soil seed bank studies using chemical treatments

The seedling emergence method (SEM) is the most frequently used method for studying the soil seed bank. The main prob- lem with this method is that it cannot provide a complete assessment of the seed flora present in the soil because its results are influenced by seed dormancy. In order to break seed dormancy of the soil seed bank, SEM can be combined with some chemical treatments. The objectives of this study were to determine the best chemical treatment which is able to overcome seed dormancy, and to study the effects of different chemical treatments on soil seedling emergence of different plant func- tional groups. Therefore, twenty soil samples were collected in the early spring in subalpine rangelands in northern Iran. Each soil sample was divided into four equal subsamples, and each subsample was treated by one of the dormancy-breaking treatments including gibberellic acid (GA 3 ), hydrogen peroxide (H 2 O 2 ), potassium nitrate (KNO 3 ) and distilled water as control. The emergent species from the soil samples were categorized into functional groups, i.e., annual forbs, perennial forbs and perennial grasses. The results showed that the highest total seedling emergence was observed in the soil samples treated with GA3 (5465 seedlings/m 2 ), whereas the lowest seedling emergence was found in the soil samples by KNO3 appli- cation (586 seedlings/m 2 ). The perennial forbs were the only functional group that responded to all chemical treatments. We concluded that the use of GA 3 for breaking seed dormancy can be useful for providing a more reliable estimation of the soil seed bank characteristics

Effect of grazing removal on aboveground vegetation and soil seed bank composition in sub-alpine grasslands of northern Iran

International audienc

Effect of burning of evergreen savin juniper and herbaceous patches on soil: Seed banks, chemical and biological properties

The coniferous shrub species Juniperus sabina (savin) is widespread in mountainous regions of Eurasia. The species produces large amounts of fire-prone plant mass in its habitats. The aim of this study was to assess the effect that burning of savin shrubs has on the soil seed bank (SSB), the microbial respiration and the amount of organic matter under its canopy. In each of three sampling areas, four individuals of savin were randomly selected. Under each of these individuals and on adjacent herbaceous control patches, soil samples were taken from 0 to 5 cm and 5–10 cm depths for SSB, biological and chemical analyses. The sampling was repeated after burning the canopy. We found that the immediate effects of burning on the SSB and on the biological and chemical soil parameters were significantly negative. In particular, SSB density, magnitude of microbial respiration and amount of organic matter were significantly decreased after savin canopy burning in 0–5 cm depth, while these changes were less pronounced on the burned herbaceous patches. Hence the restoration of gaps created by burning savin cannot rely on the SSB. Furthermore, alkalization of the soil and decreased soil quality caused by savin burning might hamper the vegetation recovery even in the medium to long run

Environmental determinism versus biotic stochasticity in the appearance of plant species in salt-marsh succession

Background and aims It is generally accepted that in terrestrial ecosystems the occurrence and abundance of plant species in late successional stages can be predicted accurately from prevailing soil conditions, whereas in early succession their presence is much more influenced by chance events (e.g. propagule availability). Late successional vegetation stages would therefore be deterministically structured, while early succession would be dominated by more stochastic features. To test this hypothesis in salt marsh conditions, we compared the effect of abiotic environmental factors on vegetation composition and probability of occurrence of individual species in two adjacent salt marshes, differing in age (i.e. successional stage). Material and methods In 2002, a new salt marsh was created on substrate devoid of plant diaspores in the nature reserve The Uzermonding (Nieuwpoort, Belgium). From 2002 onwards, primary colonization started on that sterile substrate by hydrochoric seed dispersal, induced by tidal water currents from an adjacent 5 ha relic of the old salt marsh. In 2005, three years after the start of the colonization process of the new salt marsh, vegetation and three abiotic environmental factors (soil texture, salinity and elevation) were recorded in a set of 155 releves on the new and old salt marsh. Key results In contrast to the general observation in other terrestrial ecosystems, the vegetation composition of the early successional stage of the new salt marsh appeared to be at least as much determined by the combined effect of the measured abiotic factors as that of the old salt marsh. As revealed by logistic regression the presence/absence of perennial species as well as annual species oldie young salt marsh could be well predicted by the measured abiotic variables. For the old salt marsh this also held for the perennial species, but not for the annual species. The stochastic appearance of gaps in the perennial vegetation cover appeared to be important for the establishment of annuals in the older salt marsh. Conclusion In the case of salt marsh succession, the generally accepted hypothesis of early successional stochasticity dominance versus late successional environmental determinism must be rejected