In order to study weed density and dominance in irrigated wheat fields، 4126 fields were investigated in seven climatic zones (according to the Cilianinov method). 496 weed species from 42 families have been observed within these fields. Slightly semi-arid، humid، semi-humid، mean semi-arid، highly semi-arid، arid and absolutely arid climates had the highest density and mean، slightly and highly semi-arid، humid، semi-humid، arid and absolutely arid climates had the highest diversity (according to the Shannon-viener index)، respectively. Among 496 recorded species، 280 species belonged to five major families; Asteraceae، Poaceae، Fabaceae، Brassicaceae and Caryophyllaceae with 76، 69، 67، 44 and 24 species، respectively: These families had the highest diversity in irrigated wheat fields of Iran. Bindweed (Convolvulus arvensis) and wild oat (Avena ludoviciana) had the greatest abundance at 81. 9 and 59. 9 percent، respectively. In addition، these two weeds have been recognized as assertive and ascendant weeds، respectively. Mean، slightly and highly semi-arid، humid، semi- humid، arid، and absolutely arid climates had the first to sixth ranks on the weed species richness measurement. According to the results، mean semi-arid with highly and slightly semi-arid climates and mean semi-arid with arid climates had the highest and lowest species similarity on the base of the Sorenson index، respectively.

The principled use and proper management of arid and semi-arid regions, which cover a significant extent of the Earth’s drylands, require planning based on accurate and timely information on different ecosystem components, including vegetation. Considering vegetation is one of the major and important needs in the management and exploitation of arid and semi-arid regions. Since it is time consuming and costly to collect information at vast levels in dry and desert conditions by traditional ways and through ground operations, the use of new techniques in these studies is necessary. Remote sensing is one of the most effective techniques in this field. The arid and semi-arid regions have low Leaf Area Index and fairly open crowns due to reactions to environmental stresses, which makes the surface soil visible in these areas. The high effect of surface soil on spectral reflections of vegetation in arid and semi-arid regions causes mistakes in evaluating plants in these areas through remote sensing. Many studies have been carried out on introducing suitable plant indices for assessing vegetation changes in arid and semi-arid regions. The results of all these studies indicate that due to variability of vegetation and soil characteristics in different regions of arid and semi-arid regions, as well as differences in utilized satellite data in terms of sensor type, bands number, spectral range, spatial accuracy, etc. it is not possible to introduce a specific indicator for vegetation studies in all arid and semi-arid regions, but, considering the characteristics of vegetation, soil and the type of used satellite data, indicator or indicators that are meaningful according to studies can be introduced for each region. The aim of this study is to investigate the spectral reflections of vegetation in arid and semi-arid regions considering different reactions of plants in arid and semi-arid regions against environmental stresses, the openness of crown of vegetation, and the high effect of surface soil on the reflection of the vegetation in these areas, and to introduce a suitable technique for studying the vegetation of such areas.

The average weather condition in a specific region is defined as climate. The diversity of climatic variables is effective in determining the climate of a region and causes the formation of diverse and different climates. One of the effects of climate change is that causes an increase or decrease in a climate zone and, as a result, a shift in climate zones. Climate classification is an attempt to identify and recognize the differences and similarities of climate in different regions and to discover the relationships between different components of the climate system. Climate classification indicators are used to visualize current climate and quantify future changes in climate types as predicted by climate models. The studies conducted on these methods show that climatic variables affecting experimental methods such as temperature and precipitation should be considered effective variables in determining climatic boundaries in a new way. The De Martonne aridity index is an empirical index for climate classification based on two components, precipitation and temperature. Due to its high accuracy, and the use of variables that are more accessible and can be measured at most meteorological stations, De Martonne’s index has received more attention from researchers and has been used in many studies of climate change. Therefore, the purpose of this research is to evaluate the effects of climate change on the climatic classification of Iran.

To investigate the effects of climate change on the climatic classification of Iran, the De Martonne aridity index has been used. To show the effects of climate change in the past and the future on Iran's climate, data from 120 meteorological stations of Iran, which are distributed in different locations with different climates, were collected and analyzed in the statistical period of 1933-2022. The climatic condition of Iran in the base period was determined according to the De Martonne aridity index. In addition, to investigate the effects of climate change in the coming periods on the climatic classification of Iran, the data related to the output of the CanESM2 model, which is one of the CMIP5 models that is hybridized by the Canadian Center for Climate Modeling and Analysis (CCCMA) by combining CanCM4 and CTEM models, were used. To examine the changes in climatic classes of Iran under different scenarios and conditions, the output of two release scenarios, RCP2.6 and RCP8.5, were utilized. Due to the large-scale output of General Circulation Models (GCM), the output of this model was downscaled using the LARS-WG model. The LARS-WG model, which is considered one of the most famous and widely used models for downscaling weather data, was used to generate precipitation values, minimum and maximum temperatures, as well as daily radiation, under base and future climate conditions.

According to the results, the majority of Iran (90.49%) has an arid and semi-arid climate. The percentage of arid climate is 68.82%, while that of semi-arid climate is 21.97%. Therefore, Iran should be called an arid and semi-arid country in terms of climate. By analysis of the effects of climate change indicates that in future periods, the precipitation and average temperature will increase. This increase will be greater under the RCP8.5 scenario than the RCP2.6 scenario. The study of the climatic classification of Iran in the coming periods indicates that the majority of the country will continue to experience arid and semi-arid climates. The sum of arid and semi-arid climates will reach its lowest level in the period of 2020-2041. This is following the RCP2.6 scenario, after which these climates are expected to expand once more. According to the RCP8.5 scenario, during the periods of 2021-2040, 2041-2060, and 2061-2080, the total area of arid and semi-arid climates will decrease. However, from 2081 to 2100, this trend will be reversed, increasing in these climates. According to the results of this research and according to the forecast, although according to different release scenarios, the difference in the area of different classes can be seen, in the future, arid and semi-arid climatic zones will still form the majority of Iran.

In this research, by using the latest available data, Iran's climate is classified by the De Martonne aridity index, and then the changes in Iran's climate classes under the effects of climate change in the future periods, according to the output of the CanESM2 model from the CMIP5 modes, which is downscaled using the LARS-WG model. It has been investigated according to two emission scenarios, RCP2.6 and RCP8.5. The results indicated that the arid climate with 68.82% and the semi-arid climate with 21.97% constitute the largest area of Iran. The remaining climatic classes collectively comprise less than 10% of Iran's area. Therefore, Iran should be called an arid and semi-arid country in terms of climate. Investigating the effects of climate change on precipitation and temperature showed that both precipitation and average temperature will increase in future periods. However, the increase in both variables will be greater under the RCP8.5 scenario. The study of the climatic classification of Iran in the coming periods indicates that the majority of the country will continue to experience arid and semi-arid climates. The findings of this study indicate the necessity of addressing the issue of climate change and the importance of involving experts and macro planners in the analysis of the effects of climate change. It is suggested to use the output of other GCM models in future research due to the uncertainty of climate scenarios. Also, the use of diverse climate classification methods that incorporate other variables is suggested for more precise identification of climate characteristics.

Soil carbon changes is one of the most important indicators impacts of climate change impacts on soil genesis. Study of soil carbon, including organic and inorganic carbon (carbonates) and its impact on other soil characteristics in different climates, is essential for the proper management of soil carbon on a global scale. It is too important the balance between different parts of carbon sources in the environment. In current study, organic and inorganic carbon complex with primary particles were studied in 9 profiles a climosequence including three climates arid, semi-arid and semi-humid with typic aridic, dry xeric and typic xeric moisture regimes and mesic and thermic temperature regimes. Results showed that the amount of organic carbon in all three components decreases with increasing depth and also clay component has more organic carbon content in all depths compared with other components of soil. Contrast to organic carbon, inorganic carbon content is lower in surface horizon compared with the subsurface in all three components of particle size and increases with increasing depth. The avearage of organic carbon components of particle size in three studied regions showed that the following trend clay (1.1%) > silt (0.68%) > sand (0.23%), while inorganic carbon in the soil with trend silt (14.41%) > sand (12.11%) > clay (8.14%).

On the basis of definition of United Nation Convention on Combating Desertification: “desertification is land degradation on arid, semi-arid and sub- humid arid regions by reason of climate change and human activities”. Also on the basis of this Convention, arid, semi-arid and sub-humid arid regions is regions that quotient between precipitation with potential evapotranspiration is approximately 0.05 to 0.65. Annual temperature averages and total annual precipitation from 45 synoptic meteorological stations for a 30 years period (1976-2005) has been collected the Meteorological Organization of Iran. In this paper for study of spatial spreading trend of arid and semi-arid climates of Iran of bioclimatic index of UNEP (United Nation Environment Programme) were used. Thirty years period divided to three subgroups: (1976-1985), (1986-1995) and (1996-2005). Then for each subgroup provided zoning maps and finally zoning maps were subtracted from each other. Results showed that: (1) The most spatial spread of arid and semi-arid climates observed in third decade and (2) The most severe changes of spatial climate observed in west and north-west and south-east of Iran, respectively.

The research aim is to study the yield including irrigated and dry-farmed wheat, barley, and corn in the climate and sub-climates of the country. So, the average yield of the studied products, average rainfall, and average temperature data have been used for the climatic change from the period 1982-2015. Due to the fact that cereal products over 56% and 77% of the cultivated area in arid and semi-arid regions, respectively. Therefore, in this study, only cereal are studied and among all of the crops, they have been selected, the five crops that have the highest area under cultivation. Finally, the function of various crops’ demands was used to investigate the effects of climate change on crops.The results show that the highest yield coefficients of rainfall are to precipitation in cold and sub-climates semi-arid cold, semi-arid hot, semi-arid temperate, cold dry, hot dry and temperate dry are related to dryland wheat, irrigated wheat, dryland wheat, dryland barley, dryland barley, dryland wheat, respectively. In addition, the highest coefficients of function of demands to temperature in cold and sub-climates of semi-arid cold, semi-arid warm, semi-arid temperate, cold dry, hot dry and temperate dry are related to dryland wheat, dryland barley, irrigated wheat and dryland barley, dryland wheat, respectively. According to the results of the research and in order to efficiently manage production and better performance, agricultural products in climates and sub-climates in the country are recommended. Compilation of a comprehensive cultivation model and allocation of the type of crop cultivation in the climate and sub-climate should be done by considering the reaction rate of the yield of the products and the exploitation of most of the mentioned products.

Energy management in agroecosystems helps to attain efficient and sustainable use of energy. The aims of this study were to evaluate the energy input, energy output and energy indices in irrigated and dry-land wheat farms under different climatic conditions in Kermanshah Province. Data were collected from irrigated and dry-land wheat growers by using a face-to-face questionnaire during 2012-2013. The results showed that, regardless of climatic conditions, total energy input in irrigated and dry-land wheat farms was 52444 and 15612 MJ ha-1, respectively. Among irrigated wheat farms, the highest and the lowest energy inputswere calculated in aridwarm (60157 MJ ha-1) and wet-moderate (48083 MJ ha-1) climates while, in dry-land wheat farms, these were calculated in semiarid-cold (15295 MJ ha-1) and wet-cold (16263 MJ ha-1) climates, respectively. In irrigated wheat farms the highest energy output was 174289 MJ ha-1 for a semiarid-cold climate and the lowest was 11494 MJ ha-1 for an arid-warm climate while, in dry-land wheat farms, the highest was 70806 MJ ha-1 for a semiaridwarm climate and the lowest was 36955 MJ ha-1 for an arid-warm climate. Energy use efficiency was about 19.9% higher in dry-land farms than in irrigated ones. The highest energy use efficiencyin irrigated and dry-landwheat farms was 3.5 (in a semiarid-cold climate) and 4.4 (in a semiarid-warm climate), respectively. The highest energy productivity in irrigated farms was 0.11 for wet-cold and semiarid-cold climates while it was 0.11 for wet-moderate and semiarid-cold climates in dry-land farms. Based on our results, dry-land wheat farms had higher efficiency and productivity compare to irrigated wheat farms.

Climate and land use are two important factors which are greatly influence on soil physical and chemical properties. This research was conducted to study the effects of climate and land use on physical and chemical properties of soil in Ilam province in 2016. After initial studies, Ivan area with semi-humid climate and Ganjavan with semi-arid climate in Ilam province were selected. In each region, three land uses including forest, rangeland and agricultural were considered. After field studies in each land use, five soil samples were taken from 0-10cm and 10-30cm depths and collected randomly. The results showed that the highest amount of soil lime (47.85%) and soil silt (31.75%) were obtained in semi-arid climate of Ganjvan. The soils of Ayvan as a semi-humid climate had the highest amount of clay and K available. The highest bulk density (1.87 g.cm-3) was obtained in semi-arid climate of Ganjavan under the effect of agricultural use at lower soil depth. The lowest amount of bulk density (1.08 g.cm-3) was observed in semi-humid climate of Ayvan in the soil surface depth under forest land use. The highest amount of organic matter was obtained in forest land use in semi-humid climate in Ayvan, (42.85 %) which was more than semi-arid climate of Ganjvan. Agricultural land use had the lowest amount of organic matter (4.37%). The highest amount of N (0.514%) and P (35.04 mg kg-1) concentrations were obtained in forest land use in the semi-humid climate of Ayvan. The amount of Ca and Mg concentration in subsoil solution (10-30cm) layer was higher than topsoil solution (0-10cm) layer in Ayvan. In general, by changing land use from forest to farm, the percentage of clay, organic matter, nitrogen, phosphorus, and potassium available decreased in semi-arid climates of Ganjvan. Therefore, proper land use management in semiarid climates is essential for optimal preservation of soil properties.

Climate change phenomenon is one of the most important global challenges for mankind in providing sufficient and healthy food for the ever-increasing world population. The leading factors of climate change, such as increasing temperature, changing precipitation patterns, and increasing the frequency and intensity of weather events, affect soil characteristics, especially in the ecosystems of arid and semi-arid regions. These changes can directly affect the growth and production of crops. The amount of soil organic matter is one of the most important indicators of soil quality and health, which affects many physical, chemical and biological characteristics of soil and is directly and indirectly affected by climatic factors such as temperature and rainfall. On the other hand, the balance of input and output of organic carbon to the soil is effective on the amount of carbon dioxide in the atmosphere and thus on global warming and the climate change phenomenon. The results of many forecasts show that in arid and semi-arid regions, climate change will lead to an increase in temperature and a decrease in rainfall. Therefore, considering that the amount of organic matter in the soil decreases with the increase in temperature and decrease in humidity, it seems that the phenomenon of climate change will have adverse effects on the amount of soil organic matter and biological activity, and then on the production of crops in arid and semi-arid regions. Therefore, it is very important to use the necessary solutions to mitigate these adverse effects and adapt to the upcoming conditions. Mitigation refers to methods that lead to the reduction of greenhouse gas emissions, especially carbon dioxide; But the goal of adaptation is to mitigate the inevitable effects of climate change. Based on the results of various publications, compliance with the principles of the conservation agriculture system is considered one of the most important mitigation and adaptation solutions in dealing with the consequences of climate change in arid and semi-arid regions. Due to the fact that the climate change phenomenon is an inevitable event and its adverse effects and consequences in human life are felt more and more intense day by day, it is necessary for the management of soil resources to have the necessary foresight regarding the results of this phenomenon on the quality of the soil and the potential of producing agricultural products, especially in Arid and semi-arid areas should be considered.

Phosphorous is one of the essential macronutrients for plant growth and development but its mobility in soil is very low. The utilization of the soil biological potential, in particular phosphate solubilizing bacteria, is an efficient way which can be used for exploiting available sources of phosphorous in the soil. The principal mechanism for mineral phosphate solubilization is the production of organic acid, and acid and alkaline phosphatases play a major role in the mineralization of organic phosphorous in the soil. Presence and distribution of phosphate solubilizing bacteria in the soil and soil phosphatase activities is influenced by soil conditions such as climate, soil type, vegetation and land uses. In order to understand the relationships and considering the importance of the subject, the soil samples were chosen from two different climates; semi-moist (Fandoghlou-Ardabil) and semi-arid (Namin- Ardabil) under culture of legumes, cereals and uncultivated areas, in this experiment.
In order to study the effects of different land uses, climate conditions and soil physicochemical properties on phosphate solubilizing microorganism (PSM) distribiution and soil acid and alkaline phosphatase activity, a factorial experiment based on completely randomized design was performed with considering three different land uses (including legumes, cereals and wasteland) and two climate conditions (semi-moist: Fandoghlu- Ardabil and semi-arid: Namin-Ardabil). Four composite soil samples (0-25 cm) were taken from each land uses. Finally, a total number of 24 soil samples were used to enumerate phosphate solubilizng bacteria and evaluate soil phosphatase activities. The enumeration and selection of bacteria in the mineral Sperber medium was done by attention to the clear zone production in the presence of tri-calcium phosphate and in organic sperber (IHPТ) due to blue phenotype of grown colonies. Also, phosphatase activity of soil samples was assessed based on the usual methods for phosphatase assessment. Moreover, after the evaluation of the physicochemical properties of the soil samples and soil enzyme activities and PSB distribution, all data were analyzed by SPSS and MSTAT-C softwares.
The Sperber mediums containing mineral and organic phosphates were used in counting the number of PSB. According to the results, the highest total number of bacteria (>6 log cfu/g) was gained in legume land uses in both climate conditions. Furthermore, the highest numbers of organic and mineral phosphate solubilizing bacteria (5.3 log cfu/g) were counted in samples taken from pastures, in other word in soil samples which were collected from uncultured land in semi-moist climate conditions. Enzyme assay showed that acid phosphatase activity (430 µg pNP/g.h) in semi-moist climate conditions were increased three times in comparison to semi-arid climate conditions. Perhaps, this increase can be explained by parameters such as high moisture content and organic matter which can cause an increase in the number of bacteria and soil enzyme content. Our results showed that, alkaline phosphatase activities (APAs) were affectd by interaction effects of land uses and climate, wherein the highest APA (810 µg pNP/g.h) was measured in legume samples in semi-arid climate conditions. The pH of these soil samples and supporting legume rhizospheres from AP producing microorganisms may be the reasons of this increment.
The highest activity of the soil acid phosphatase was observed in soil samples which were taken from uncultivated area under semi-moist climate conditions (namely pastures) (866.59 µgPNP/g.h) while the soil alkaline phosphatase activity had high mean in legume land use soil samples under semi-arid climate conditions (795.15 µPNP/g.h). The total number of bacteria was the highest in semi-arid leguminous land use (14.13×106 cfu/g) but the total numbers of solubilizing bacteria in both mineral and organic media were the highest in semi-moist uncultivated area (respectively 1.9 ×106 and 1.48 × 106cfu/g).