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Modeling species distribution and predicting the effects of climate change on plant species decline are necessary in restoration programs. This study aimed to predict the occurrence and decline of Astragalus verus under climate change in Central Iran with an area of about 123,167 km2. We recorded 12 and 71 sites for the dead and alive species using the stratified sampling method, respectively. The general circulation model of CCSM4 was applied at two timeframes of present and 2050 under two climate change scenarios of RCP2.6 and RCP8.5. Four environmental variables of annual mean temperature, the maximum temperature of the warmest month, the precipitation of the coldest quarter, and elevation were selected as the inputs of the nine statistical models. Results indicated that Random Forest model had the best performance in predicting climatic niche and decline of A. verus (AUC and TSS of 0.99) compared to the other models. The suitable habitat and decline for this species are 12.4% and 19.87% of the study area, respectively. With the estimated temperature rise of 3 °C under the CCSM4-RCP2.6 scenario, A. verus habitat will shrink by about 3.4% of the study area and will move toward higher elevations with colder temperatures in the future. Most changes in the suitability of the species will occur in the altitude range of 1800 to 2200 meters because the most temperature and precipitation variations will happen in this elevation stratum. The results can be used to prevent its rapid dieback or even restore vegetation cover in regions with similar conditions. [ABSTRACT FROM AUTHOR]

Soil degradation poses serious environmental problems and requires quantitative assessment. This study aimed to investigate the soil properties in rangelands with different management conditions. Based on the assessment of soil erosion, vegetation cover, vegetation composition, and vegetation vigor, 56 sites were selected in rangelands with moderate, poor, and very poor conditions located in 15 grazing-free areas and one wildlife refuge region. Soil samples (0–10 cm layer) were collected from these sites through a systematic-random method to compare their physical and chemical properties. Results showed that soil organic carbon (OC) and total nitrogen content were significantly different between sites with different range conditions. The mean weight diameter of water-stable aggregates and structural stability index in moderate rangelands were 1.56 mm and 3.98%, respectively, and declined towards more degraded rangeland (i.e. 0.84 mm and 0.83%). Grazing-free rangelands exhibited a relatively larger OC deficit; hence specific management measures and control of grazing are required to enhance the quality of soil in these sites. This study highlighted the role of organic matter in preserving soil structural stability. Increasing protection level of rangelands and decreasing grazing pressure may preserve soil quality and combat desertification in these arid regions. [ABSTRACT FROM AUTHOR]

The scale of satellite images affects the recognition of landscape patterns and conditions. Therefore, this research focused on relationships between landscape fragmentation and function using multi-sensor imagery in semi-arid regions of Iran. Landscape function leakiness index (LI) and fragmentation metrics were calculated based on Sentinel-2, Landsat OLI, and MODIS data and compared using regression models and principal component analysis. Upscaled data were obtained based on changing the resolution of native Sentinel-2 from 10 to 30 m and 250 m. Results showed low (4%) and high (91%) fragmentation values in good and poor rangelands, respectively. The Sentinel-2 native LI index was the best indicator of vegetation cover (R2 = 0.99, p < 0.001) and fragmentation (R2 = 0.72, p < 0.05) and its upscaling to 30 m correlated better with fragmentation values than 250 m. The findings indicated that landscape functionality has reduced in the degraded areas because of increasing fragmentation and inter-patch spaces. [ABSTRACT FROM AUTHOR]

The present study explored the habitat suitability for an endangered species, Hedysarum criniferum, in Iran using fuzzy logic. We measured 24 environmental variables including soil, climate, and physiographic variables of eight natural habitats of H. criniferum as the predictive variables and the percent cover of the species as the response variable. The most important environmental factors influencing species distribution and the species response curves were determined by principal component analysis (PCA) and the generalized linear model, respectively. The tolerance range and the optimal growth point of the studied species with respect to the environmental factors were specified, the ranges were divided into 11 classes by fuzzy value, and the fuzzy functions of the environmental factors were calculated. The species habitats were classified by the developed fuzzy model. Three regions with no H. criniferum occurrence were selected to determine their fuzzy suitability. The success in germination and shoot growth length of H. criniferum were used as the metrics of the habitat suitability in these regions. Based on the PCA, H. criniferum occurrence was most strongly affected by soil Mg, K, and Ca content, soil pH, wind speed, annual minimum temperature, slope, and altitude. The results revealed that the seedling length and germination percentage in the site with the fuzzy suitability of 0.6 differed from those in the two other sites with the fuzzy suitability of 0.5 and 0.3 significantly. The method used in this study can be employed in predicting optimal habitats for other endangered species in different ecosystems. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the soil aggregate stability and selected soil quality indicators in various land uses in a semiarid region in central Iran. Random soil sampling was used to collect soil samples from surface (0–5 cm) and subsurface (5–25 cm) soil layers in rangelands of different condition classes, dry farmland and abandoned land. The aggregate size distribution indices including mean weight diameter (MWD), geometric mean diameter (GMD) and median diameter (D50) of water-stable aggregates in the collected soil samples were measured. Our findings showed that percent of macroaggregates (>0.25 mm) of the surface and subsurface layers in rangelands of different condition classes were significantly higher than dry farmlands and abandoned lands (P < 0.05). Results showed that the trend of changes in soil organic matter was similar to soil aggregate stability in different land uses in both soil layers as follows: rangeland with good condition > rangeland with poor condition > abandoned land > dry farmlands. The structural stability indices (i.e. MWD, GMD andD50) of rangelands with good condition were significantly greater than other land uses (P < 0.05). This highlights the importance of maintaining native rangeland to prevent organic matter loss, structure deterioration and soil erosion. [ABSTRACT FROM AUTHOR]

Monitoring is essential for appropriate rangeland management. The present study aimed to examine the potential of moderate resolution imaging spectroradiometer (MODIS) satellite imagery in rangeland condition assessment and monitoring within and across vegetation types in the arid and semi-arid rangelands of central Iran. The normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI) were calculated from MODIS Aqua/Terra Level 1B data (related to 2003–2013). The obtained values were compared with vegetation cover measurements and rangeland condition classes at 110 sampling sites using linear regression, one-way analysis of variance (ANOVA), independent-samples t-tests, and Tukey’s pairwise comparisons. The results showed that two indices made stronger predictions of vegetation cover within a vegetation type (R2 > 0.87,P < 0.001) than across vegetation types (R2 > 0.51,P < 0.001). Both NDVI and EVI worked well across vegetation types (P ≤ 0.001) in predicting rangeland condition classes (poor, fair, and good), but their performance varied between vegetation types. The NDVI classified about 73, 19, and 7.5% of the rangelands in poor, fair, and good condition classes, respectively. The good performance of MODIS NDVI index at different landscapes indicates that this index has high potential in detecting vegetation cover and discriminating different condition classes, therefore, it can be used to aid field- based techniques in rangeland condition assessment and monitoring. [ABSTRACT FROM AUTHOR]

Fire products have been widely identified as germination cues for a number of species from both fire-prone and fire-free ecosystems. However, there is uncertainty about the effects of fire products on seed germination of semi-arid rangeland species. We examined the germination of seven dominant species from Central Zagros rangelands in the semi-arid region of Iran under various heat shock (60, 80 and 120 °C), aerosol smoke, ash and control treatments. Our findings showed that fire products could enhance, inhibit or not affect the seed germination of rangeland species in this area. The germination percentage ofAstragalus adscendensincreased following 60 °C heat treatment in comparison with the control. The germination ofAstragalus verus,Bromus tectorum,B. tomentellusandPhlomis olivieriwere increased significantly using smoke treatment (P<0.0001). The seed germination ofB. tomentellusandB. tectorumwas promoted by ash treatment, whereas the other species exhibited no response or were inhibited by fire products. In addition, smoke treatment shortened the overall germination time ofB. tectorum. These findings suggest that fire products affect the germination of several species and can serve as potential tools for understanding the vegetation dynamics and restoration of disturbed semi-arid rangelands. [ABSTRACT FROM PUBLISHER]