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Measuring the diversity of plant functional types, identifying their characteristics, and their classification will help to identification of woodland germination capacity and implementing appropriate range management programs. The study was designed to measure the species diversity and to identify plant functional types in three adjacent ecological sites in Shimbar or Shirin Bahar region. During winter, spring and summer since 2013 to 2014, the data regarding the percentage of species coverage were taken from 106 plots using stratified random sampling method in the south facing slopes, north facing slopes and the wetland. Species diversity (Alpha diversity) and habitat diversity (Beta diversity) were measured using PAST and SDR softwares. According to the Shannon-Wiener and Simpson indices the greatest species diversity were found in the wetland, south slopes and north slopes respectively. Species richness was higher in northern slope than northern slopes and the lowest in wetland. For classifying and determining response of vegetation to environmental factors and identifying plant functional types, about 66 resistance to disturbance characters were measured and subjected to clustering by Ward method in R software. The annual and perennial species were classified into 21 and trees and shrubs to 8 classes.

Soil bacteria and fungi play key roles in the functioning of terrestrial ecosystems, yet our understanding of their responses to climate change lags significantly behind that of other organisms. This gap in our understanding is particularly true for drylands, which occupy ∼41% of Earth´s surface, because no global, systematic assessments of the joint diversity of soil bacteria and fungi have been conducted in these environments to date. Here we present results from a study conducted across 80 dryland sites from all continents, except Antarctica, to assess how changes in aridity affect the composition, abundance, and diversity of soil bacteria and fungi. The diversity and abundance of soil bacteria and fungi was reduced as aridity increased. These results were largely driven by the negative impacts of aridity on soil organic carbon content, which positively affected the abundance and diversity of both bacteria and fungi. Aridity promoted shifts in the composition of soil bacteria, with increases in the relative abundance of Chloroflexi and α-Proteobacteria and decreases in Acidobacteria and Verrucomicrobia. Contrary to what has been reported by previous continental and global-scale studies, soil pH was not a major driver of bacterial diversity, and fungal communities were dominated by Ascomycota. Our results fill a critical gap in our understanding of soil microbial communities in terrestrial ecosystems. They suggest that changes in aridity, such as those predicted by climate-change models, may reduce microbial abundance and diversity, a response that will likely impact the provision of key ecosystem services by global drylands.

Aims Climate and human impacts are changing the nitrogen (N) inputs and losses in terrestrial ecosystems. However, it is largely unknown how these two major drivers of global change will simultaneously influence the N cycle in drylands, the largest terrestrial biome on the planet. We conducted a global observational study to evaluate how aridity and human impacts, together with biotic and abiotic factors, affect key soil variables of the N cycle. Location Two hundred and twenty-four dryland sites from all continents except Antarctica widely differing in their environmental conditions and human influence. Methods Using a standardized field survey, we measured aridity, human impacts (i.e. proxies of land uses and air pollution), key biophysical variables (i.e. soil pH and texture and total plant cover) and six important variables related to N cycling in soils: total N, organic N, ammonium, nitrate, dissolved organic:inorganic N and N mineralization rates. We used structural equation modelling to assess the direct and indirect effects of aridity, human impacts and key biophysical variables on the N cycle. Results Human impacts increased the concentration of total N, while aridity reduced it. The effects of aridity and human impacts on the N cycle were spatially disconnected, which may favour scarcity of N in the most arid areas and promote its accumulation in the least arid areas. Main conclusions We found that increasing aridity and anthropogenic pressure are spatially disconnected in drylands. This implies that while places with low aridity and high human impact accumulate N, most arid sites with the lowest human impacts lose N. Our analyses also provide evidence that both increasing aridity and human impacts may enhance the relative dominance of inorganic N in dryland soils, having a negative impact on key functions and services provided by these ecosystems.

As the utilization of rangelands in Iran has exceeded 2.2 times its carrying capacity, increasing numbers of livestock, especially in drought years, have dramatic effects on rangelands. In this regard, the prediction of forage production is an important management strategy to mitigate the consequences of drought. In Plour and Saveh Range Experimental Sites, climatic factors such as precipitation, temperature (mean, maximum and minimum), evapotranspiration, standardized precipitation index, reconnaissance drought index, and/or a combination of these factors were used to construct a predictive model of forage production. For each climatic variable and/or index, 33 time periods of 1–4, 6 and 9-months were specified. We used principal components analysis, stepwise regression and best subset regression, to reduce the number of variables and then the appropriate time periods selected. To select a model, assessment statistics of correlation coefficient, mean of bias error, root mean of square error, mean of absolute relative error and ideal point error were used. Finally models derived from combined climatic factors and drought indices were selected for the prediction of forage production at both study areas. In the arid region of Saveh, production is more effected by precipitation, while in the humid and colder region of Plour, minimum temperature had more effects on plant growth. In Saveh, due to a lack of rainfall in February and minimum temperatures in March, production has direct and indirect relationships with drought and with maximum temperatures, respectively. In the Plour, production has a direct relationship with the maximum temperatures of March–June and drought of February–March and has an indirect relationship with the maximum temperatures of May–June.

The effect of six SiO2 nanosized concentrations (0, 5, 20, 40, 60 and 80 mg L-1) and three seed prechilling treatments (control, seed prechilling before nano SiO2 treatments, treatments of seed with nano SiO2 before prechilling) on germination and seedling growth of tall wheatgrass (Agropyron elongatum L.) were studied. Results indicated that application of SiO2 nanoparticles significantly increased seed germination of tall wheatgrass from 58 percent in control group to 86.3 and 85.7 percent in 40 and 60 mg L-1, respectively. Applying SiO2 nanoparticles increased dry weight of shoot, root and seedling of tall wheatgrass. Increasing concentration of nanoparticle from 0 up to 40 mg L-1 increased seedling weight around 49 percent compared to the control, nevertheless decreased under 60 and 80 mg L-1 treatments. In conclusion, seed prechilling in combination with SiO2 nanoparticles largely broke the seed dormancy for A. elongatum.

Global Ecosystem Analysis The relationship between species richness and the functional properties of their ecosystems has often been studied at small scales in experimental plots. Maestre et al. (p. 214 ; see the Perspective by Midgley ) performed field measurements at 224 dryland sites from six continents and assessed 14 ecosystem functions related to carbon, nitrogen, and phosphorus cycling. Positive relationships were observed between perennial plant species richness and ecosystem functionality. The relative importance of biodiversity was found to be as large as, or larger than, many key abiotic variables. Thus, preservation of plant biodiversity is important to buffer negative effects of climate change and desertification in drylands, which collectively cover 41% of Earth's land surface and support over 38% of the human population.

In arid environments, episodically-pulsed resources are important components of annual water and nutrient supply for plants. This study set out to test whether seedlings have an increased capacity for using pulsed resources, which might then improve establishment when in competition with older individuals. A second aim was to determine whether there is a trade-off in competitive strategies when resources are supplied continuously at low concentrations, or as pulses with pronounced inter-pulse periods. A glasshouse experiment used a target-neighbour design of size-asymmetric competition, with juveniles of Panicum antidotale (blue panicgrass) introduced into contrasting densities of adult plants. Stable isotopes of nitrogen were used for measuring plant resource uptake from pulses, and tolerance to inter-pulse conditions was assessed as the mean residence time (MRT) of nitrogen. A higher root/shoot ratio and finer root system enhanced the capacity of juveniles to use resources when pulsed, rather than when continuously supplied. Higher resource uptake during pulses improved the establishment of juvenile Panicum in mixed cultures with older individuals. However, a trade-off was observed in plant strategies, with juveniles showing a lower MRT for nitrogen, which suggested reduced tolerance to resource deficit during inter-pulse periods. Under field conditions, higher utilization of pulsed resources would lead to the improved seedling establishment of Panicum adjacent to "nurse" plants, whereas mature plants with well-developed roots, exploiting a greater soil volume, maintain more constant resource uptake and retention during inter-pulse periods.

Aim: Geographical, climatic and soil factors are major drivers of plant beta diversity, but their importance for dryland plant communities is poorly known. The aim of this study was to: (1) characterize patterns of beta diversity in global drylands; (2) detect common environmental drivers of beta diversity; and (3) test for thresholds in environmental conditions driving potential shifts in plant species composition. Location: Global. Methods: Beta diversity was quantified in 224 dryland plant communities from 22 geographical regions on all continents except Antarctica using four complementary measures: the percentage of singletons (species occurring at only one site); Whittaker's beta diversity, ?(W); a directional beta diversity metric based on the correlation in species occurrences among spatially contiguous sites, ?(R2); and a multivariate abundance-based metric, ?(MV). We used linear modelling to quantify the relationships between these metrics of beta diversity and geographical, climatic and soil variables. Results: Soil fertility and variability in temperature and rainfall, and to a lesser extent latitude, were the most important environmental predictors of beta diversity. Metrics related to species identity [percentage of singletons and ?(W)] were most sensitive to soil fertility, whereas those metrics related to environmental gradients and abundance [(?(R2) and ?(MV)] were more associated with climate variability. Interactions among soil variables, climatic factors and plant cover were not important determinants of beta diversity. Sites receiving less than 178 mm of annual rainfall differed sharply in species composition from more mesic sites (> 200 mm). Main conclusions: Soil fertility and variability in temperature and rainfall are the most important environmental predictors of variation in plant beta diversity in global drylands. Our results suggest that those sites annually receiving c. 178 mm of rainfall will be especially sensitive to future climate changes. These findings may help to define appropriate conservation strategies for mitigating effects of climate change on dryland vegetation

The biogeochemical cycles of carbon (C), nitrogen (N) and phosphorus (P) are interlinked by primary production, respiration and decomposition in terrestrial ecosystems. It has been suggested that the C, N and P cycles could become uncoupled under rapid climate change because of the different degrees of control exerted on the supply of these elements by biological and geochemical processes. Climatic controls on biogeochemical cycles are particularly relevant in arid, semi-arid and dry sub-humid ecosystems (drylands) because their biological activity is mainly driven by water availability. The increase in aridity predicted for the twenty-first century in many drylands worldwide may therefore threaten the balance between these cycles, differentially affecting the availability of essential nutrients. Here we evaluate how aridity affects the balance between C, N and P in soils collected from 224 dryland sites from all continents except Antarctica. Wefind a negative effect of aridity on the concentration of soil organic C and total N, but a positive effect on the concentration of inorganic P. Aridity is negatively related to plant cover, which may favour the dominance of physical processes such as rock weathering, a major source of P to ecosystems, over biological processes that provide more C and N, such as litter decomposition1. Our findings suggest that any predicted increase in aridity with climate change will probably reduce the concentrations of N and C in global drylands, but increase that of P. These changes would uncouple the C, N and P cycles in drylands and could negatively affect the provision of key services provided by these ecosystems. Fil: Delgado Baquerizo, Manuel. Universidad Pablo de Olavide; España. Universidad Rey Juan Carlos. Departamento de Biología y Geología. Área de Biodiversidad y Conservación; España Fil: Maestre, Fernando T.. Universidad Pablo de Olavide; España. Universidad Rey Juan Carlos. Departamento de Biología y Geología. Área de Biodiversidad y Conservación; España Fil: Gallardo, Antonio. Universidad Pablo de Olavide; España Fil: Bowker, Matthew A.. Northern Arizon University/school Of Forestry; Fil: Wallenstein, Matthew D.. Northern Arizona University; Estados Unidos Fil: Bran, Donaldo Eduardo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentina. Universidad Rey Juan Carlos. Departamento de Biología y Geología. Área de Biodiversidad y Conservación; España Fil: Gatica, Mario Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina Fil: Hepper, Estela Noemí. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Pampa. Facultad de Agronomía; Argentina Fil: Prina, Anibal Oscar. Universidad Nacional de La Pampa. Facultad de Agronomía; Argentina Fil: Pucheta, Eduardo Raúl. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina Fil: Huber Sannwald, Elisabeth. Instituto Potosino de Investigación Científica y Tecnológica; México Fil: Jankju, Mohammad. Ferdowsi University of Mashhad; Irán Fil: Liu, Jushan. Northeast Normal University. Institute of Grassland Science,; China Fil: Mau, Rebecca L.. Northern Arizona University; Estados Unidos Fil: Miriti, Maria. Ohio State University; Estados Unidos Fil: Monerris, Jorge. Université du Québec a Montreal; Canadá Fil: Naseri, Kamal. Ferdowsi University of Mashhad; Irán Fil: Noumi, Zouhaier. Université de Sfax; Túnez Fil: Polo, Vicente. Universidad Rey Juan Carlos. Departamento de Biología y Geología. Área de Biodiversidad y Conservación; España Fil: Ramírez Collantes, David A.. International Potato Center; Perú Fil: Romão, Roberto. Universidade Estadual de Feira de Santana. Departamento de Ciencias Biológica, Herbario; Brasil Fil: Tighe, Matthew. University of New England; Australia Fil: Torres, Duilio. Universidad Centroccidental ‘‘Lisandro Alvarado’’; Venezuela Fil: Torres Díaz, Cristian. Universidad del Bio Bio. Facultad de Ciencias. Departamento de Ciencias Básicas. Laboratorio de Genómica y Biodiversidad; Chile Fil: Ungar, Eugene D.. The Volcani Center. Agricultural Research Organization. Institute of Plant Sciences; Israel Fil: Val, James. Office of Environment and Heritage; Australia Fil: Wamiti, Wanyoike. National Museums of Kenya. Zoology Department; Kenia Fil: Wang, Deli. Northeast Normal University. Institute of Grassland Science; China Fil: Zaady, Eli. Gilat Research Center; Israel