جستجوی مقالات مرتبط با کلیدواژه « دی اکسید کربن » در نشریات گروه « اکولوژی »

Global warming has already been occurring in Iran and will probably continue during the 21st century. There has been an increased intensity and frequency of hot daytime temperatures in the last two decades in the country. Winter wheat (Triticum aestivum L.) is the most important staple food crop in the country, with a total farming area of nearly 6.33 million ha and a production exceeding 14 million tons in 2017. Wheat production in Iran is an important component of national food security. The crop is grown almost all over the country under varied soil and climatic conditions. Most parts of Iran have an arid and semi-arid climate with long dry summer and winter rainfall, which climate change may negatively affect wheat production sustainability in these vulnerable environments. Wheat is a thermo-sensitive crop, and a change in air temperature may alter the length of its growing period and grain yield. Wheat production mainly depends on the duration of the reproductive period; thus, precise crop phenology estimation is essential for yield prediction under current and future climate conditions. The variety of C-84-8, which is named "Mihan," was introduced from the cross between the domestic variety “Barkat” and the Chinese variety “Zhong87-90” in Karaj for normal irrigation conditions and drought stress after the flowering stage in the cold regions of Iran in 2009. Mihan variety is known as a high yielded potential. The actual yield of this variety in Ardabil province has been reported between 8.13 to 10.31 tons per hectare.

The aim of this study was to simulate the climate change effects on the growth period, LAI, and biological and grain yield of wheat (Mihan variety) in the Kerman and Ardebil regions. For this purpose, we employed the HadGEM2-ES model as affected by two RCP4.5 and RCP8.5 scenarios for two time periods, 2021-2055 and 2056-2090. MarkSIMGCMmodel was used to produce daily climatic parameters as one stochastic growing season for each projection period, and the CERES-wheat model in DSSAT software was used to simulate wheat growth. Calibration and validation of the model in Kerman were performed with two-year experiments designed at the Shahid Bahonar University farm in Kerman, and for the Ardabil region, it performed with the data of the wheat projects of the Agricultural Research and Training Center and Natural Resources of Ardabil province.

The results of the model evaluation showed that MarkSIMGCM had an appropriate prediction for simulating climatic parameters and stochastic growing seasons in future climate change conditions. In both studied regions, the RCP8.5 scenario has a higher temperature and radiation increase than the RCP4.5 scenario, and these changes are greater in the long-term period than in the short-term period. Rainfall changes in both investigated regions did not show a regular trend. The growing period length was reduced by 0.51% -4.59% as affected by various climate change scenarios and periods. In the near period time (2055), simulating results showed that wheat grain yield would decrease by 3.87% compared to the current condition based on the RCP4.5 scenario. But, the traits will be increased by 0.99%-15.15% according to the RCP8.5 scenario in Kerman and Ardebil based on both scenarios. In the far period time (2090), the grain yield for the Kerman region will respectively decrease by -7.39% and -36% according to both RCP4.5 and RCP8.5 scenarios compared to the current time, and in Ardabil, based on the scenario RCP4.5 will be improved by 20.36%, and it will be declined by -2.89% according to the RCP8.5 scenario. This indicates that the negative impacts of warming will outweigh to the positive effect of CO2 enrichment over time.

In general, the results confirmed that the Mihan variety would produce acceptable grain yield in the future climate change conditions of Ardabil, but in Kerman, mitigating strategies should be considered to adapt wheat to the adverse impacts of climate change.

The main objective in agriculture production, so far, focused mostly on the increase of yield and production. Whereas today, economical and sustainable production is more important with regard to product quality, reduction of input consumption, conservation of natural resources and environment. Conservation tillage methods stabilize the soil productivity, reduce greenhouse gas emissions and protect the environment. The atmospheric concentration of greenhouse gases (GHGs) has been increased considerably in recent year's, as a result, human activities. Carbon dioxide (CO2) is the most important anthropogenic GHG; its annual emissions increased by about 80% between 1970 and 2004. Conservation tillage systems are increasingly considered as sustainable options to reduce the aftermaths of improper soil tillage. The objective of this study was to investigate energy flow and greenhouse gases emissions of sunflower production in three different tillage methods in northeastern part of Iran.

In order to evaluate the effect of three methods of sunflower production (conventional tillage and sowing, reduced tillage and direct seeding method) on energy consumption and global warming potential in rainfed conditions, this study was performed in the Kalpoosh of shahrood. Data were gathered from thirty representative fields by using a face-to-face questionnaire method and monitoring production practices and inputs used. After gathering of data, energy parameters and global warming potential were calculated based on CO2 balance. The energy amount of each input was calculated by multiplying the amount of consumed input on energy's equivalent. The output energy of sunflower was calculated by multiplying the crop yield on energy's equivalent. Other calculations of inputs and outputs in each method performed by energy coefficients.

The results indicated that total input energy in the conventional method, reduced tillage, direct seeding were 13169, 11814 and 10600 MJ.ha-1, respectively. Thus, conventional method had the highest rate of energy consumption (30 % higher than of direct seeding). Similar results reported by some researchers. The highest amount of total energy input related to nitrogen fertilizer and diesel fuel. Seedbed preparation had the highest rate of fuel and energy consumption (43.5 %) followed by nitrogen Fertilizer (37.6). Maximum of direct and indirect consumed energy, related to fuel and nitrogen, respectively. Similar results reported by some researchers. In three tillage methods, the share of irreproducible energy was the highest and small share of total energy consumption related to renewable energy. Rajabi et al. (2011) reported similar results. The energy efficiency of conventional method was less than other methods. This is due to the high share of machinery and fuel energy and greater use of workers and low yield per hectare. Reducing inputs consumption can be increased efficiency in agricultural systems. Feyzbakhsh and Soltani (2013) reported similar results. Maximum and minimum of energy productivity related to direct seeding (0.15 kg.MJ-1) and conventional method (0.11 kg.MJ-1), respectively. Maximum and minimum of global warming potential (GWP) was related to conventional method (1731 Kg.CO2 eq.ha-1) and direct seeding (1405 Kg.CO2 eq.ha-1), respectively. This issue is compatible with more fuel consumption in conventional method compared with direct seeding. In conventional method, the most rate of GWP was related to fuel consumption (44.8%) followed by nitrogen fertilizer (38.8%) and farm machinery (8.3%).

Based on this study results, through reducing of fuel consumption (replacing of obsolescent machinery and usage of modern implement, performing of farm operations in suitable soil moisture content and preventing of additional operations) and accurate consuming of nitrogen (according to soil testing), it is possible to reduce fuel consumption, greenhouse gas emission and environmental pollutions. 

Human environmental impacts on the earth can be examined in various fields. One of the areas of great importance is carbon dioxide emissions by human. One of the thousands of human activities that lead to carbon dioxide emissions into the environment is the supply of water. This paper examines the amount of carbon dioxide released by the drinking water supply system in Sepidan. This project took place within a year's time. The results of the surveyes show that in Sepidan, from one well with an energy consumption of 81318 kwh, one spring with an energy consumption of 102234 kwh, and the building of water and sewage organization with an energy consumption of 5491 kwh, amounting to 1067, 48,769 and 3293 kilograms of carbon dioxide release per year. Also, the results showed that 38 grams of carbon dioxide is produced for the supply of one liter of drinking water in the Sepidan. The results of study showed that the supply of water from the spring at a higher altitude point than areas of the city due to the specific topography of the Sepidan, Which is in the form of sloping, requires much less energy, and releases less contamination or carbon Dioxide.

Over the past few decades, advances in technology have led to the increased use of energy and emissions of greenhouse gases. In this regard, researching the economic dimension of greenhouse gas emissions and their environmental effects, particularly in the present condition that their volume is increasing, has gained a lot of attention. This is due to the fact that the industrialization of modern societies has led to the use of fossil fuels such as coal, oil, and gas in production and services. Combustion of fossil fuels causes an increase in greenhouse gas emissions into the atmosphere of which carbon dioxide (CO2) is one of the most important. About 60% of greenhouse gas emissions in Iran is caused by the agricultural sector (Energy Balance, 2012) which is regarded as one of the main sources of such emissions. In the process of the production of agricultural products, greenhouse gases will be emitted as a result of inappropriate application of land and fertilizer, livestock, and the use of fossil energy (Behboodi et al., 2010) .So, in this study, the relationship between technological progress (land under modern irrigation and agricultural machinery), energy price and carbon dioxide emissions in Iranʼ s agricultural sector has been investigated.
For this purpose, a vector autoregressive model (VAR) and time series data during the period 1970-2012 were used .The reason for this choice of model, namely VAR, in this study is that it determines the long-running relationship between the variables and also has the ability to explain the short-run relationship between them. At first, the stationary degree of the variables was examined (Abrishami, 1996).
The results showed that, although not all variables are stationary at all levels, their first order differencing was stationary. After ensuring there is a convergence between variables, the results of model estimation are presented in two categories: the long-run relationship and the short-run relationship. The results showed that the energy price variable with a lag has a negative effect on CO2 emissions in the agricultural sector. With an increase in the energy price in agricultural sector energy demand, energy consumption will be reduced which leads, in turn, to reduced CO2 emissions. The machinery variable with a lag has a positive effect on carbon dioxide emissions in the agricultural sector. By assuming the same technology, increasing the number of such machinery results in more energy being consumed; increasing energy consumption leads to increased emissions of CO2. The land under modern irrigation variable with a lag has a negative effect on carbon dioxide emissions in the agricultural sector, with the short-run results confirming the long-run results. Share variables in the prediction error variance decomposition of carbon dioxide in the agricultural sector were also examined using the analysis of variance decomposition for a 10-year period. Results showed that energy price and land under modern irrigation have the most and the least effect on this variable both in the short- and long-run.
Therefore, one method to reduce carbon dioxide emissions without reducing of production is to improve energy intensity in the agricultural sector. If energy efficiency increases, it can reduce carbon dioxide emissions in this sector without reducing of production. Also, by employing multi-purpose machines it is possible to use less machinery and thus less use of energy. Modern technologies such as pressurized irrigation that reduce energy consumption and CO2 emissions are therefore recommended.