Abstract:
مسئله گرمایش جهانی و گرم شدن سریع هوا در دهههای اخیر را میتوان یکی از مشکلات فراروی بشر در هزارهی سوم دانست. از سوی دیگر، افزایش متوسط دمای جهانی به تغییر در میزان، نوع و الگوی توزیع مکانی و زمانی بارش منجر شده است. بالا بودن دما و کمبود بارش در سطح زمین، زمینه را برای تأثیرپذیری سطح زمین از باد افزایش میدهد؛ بنابراین، در مناطقی که با افزایش دمای ناشی از گرمایش جهانی و کاهش بارش مواجه هستند، فرسایش بادی تشدید مییابد. در این پژوهش، به بررسی تأثیر گرمایش جهانی بر میزان فرسایشپذیری خاک حاصل از باد، در غرب دشت مرکزی و شرق زاگرس میانی ایران پرداخته شد. برای پهنهبندی مناطق مستعد فرسایش بادی، از مدل اثر باد بر فرسایش ـ که لویز پلتیر (Peltier, 1950) ارائه کردهاست، استفاده شد. همچنین برای پیشبینی دما و بارش در آیندهی محدودهی پژوهش، از مدل مجیک سنجن استفاده شد. در ابتدا به پهنهبندی میزان تأثیرپذیری خاک از باد در دورهی کنونی پرداخته شد. نتایج پژوهش نشان داد که دشت مرکزی ایران، تحت شرایط دما و بارش دورهی کنونی کاملاً مستعد فرسایش بادی شدید است. همچنین در مناطق مرتفع و قلل کوههای زاگرس، باد نقش بسیار ناچیزی در فرسایش خاک دارد. این پژوهش نشان داد که در اثر گرمایش جهانی در دهههای آتی، پهنههایی که در آنها فرسایش بادی شدید است، توسعه مییابد و مناطقی از دامنههای شرقی کوههای زاگرس که در دورهی کنونی، باد در فرسایش خاک آن نقش چندانی ندارد، در آینده مستعد فرسایش بادی شدیدی هستند.
Extended abstract
1- Introduction
Climate change is one of the problems human is facing today, and most of the scientific societies know that it is rooted in the distribution of greenhouse gases. Distribution of greenhouse gases with large volumes and in large spans has been affecting the energy budget and consequently has caused earth rapid temperature increase during the last decades. On the other hand, such a growth of world means temperature has changed the amount, type and spatiotemporal pattern of precipitation and it is forecasted that it will affect the hydrological cycle in the future decades, severely. Different Changes of moisture and thermal components as inputs for the organized systems of nature means that (under present condition which can be called rapid change era) we should wait for the consequences of irreversible human manipulations on the nature. The damages caused by wind erosion on the environment, health and economy are vast. These damages occur at the removal place and also at the places where the particles of soil deposit. Wind erosion entails the loss of soil fertility, the damage to infrastructure and railway lines, the limitation of the life of plant and animal species, the occurrence of severe dust storms and air quality fall, increase in respiratory problems and illnesses, and desertification. Several factors contribute to the erosion of the soil by the wind. For example, to determine the severity of wind erosion in the IRIFR model, 9 different factors are used. The Raizal model, which is a software program, determines the amount of soil erosion in terms of the physical condition of the land, including the soil, climate, and region. A point among all the wind erosion models is that the climate factors are the most effective factors in creating wind erosion. Wind erosion is one of the most important factors in soil erosion in the arid and semi-arid regions. Iran, due to its location in the arid and semi-arid belt of the Earth, is one of the areas that exposed to wind erosion. Most of the researches on wind erosion in Iran have been in the central and desert regions of Iran, whereas other parts of Iran also affected by this phenomenon. One aspect of the climate change includes the changes in soil erosion susceptibility from the wind. If the climate becomes dry, the wind erosion will increase. This study investigated the effects of global warming on the soil erosion caused by the wind in the West Central Plains and the East central Zagros mountains of Iran.
2- Methodology
Wind erosion is a process where soil particles detached from the surface and moved by the wind. Several factors contribute to the creation of wind erodibility including lithology, topography, climate, land use and vegetation. Climate conditions among these factors is the most effective one due to the fact that the climate conditions influence the other factors such as land use, vegetation, and even the surface layers of lithology and topography in the long term. This article focused on climatic aspect of influencing factors on the soil wind erodibility.
The study area was limited to Khoramabad (48.17 E, 33.26 N), Kashan (51.27 E, 33.59 N), Yazd (54.17 E, 31.54 N) and Yasuj (51.41 E, 3050 N) contexts. Louis Peltier, using two climate indices, i.e. rainfall and temperature, determines the susceptibility of the soil erosion by the wind. For the zoning of the areas susceptible to the wind erosion, Louis Peltierchr('39')s model used. In order to choose a suitable model for predicting the temperature and precipitation values under the effects of global warming, MAGICC SCENGEN model used. This composite model used for evaluating the climate change due to the greenhouse gases.
3-Results
The results showed that in the regions of the West Central plains of Iran in the current period which had low rainfall and relatively high temperature, the wind plays an important role in the soil erosion. According to Peltierchr('39')s classification, wind erosion is severe in these areas. While passing through these areas to the eastern slopes of the central Zagros Mountains, the rate of wind erosion reduced. In these areas, the wind erosion is moderate. In the highlands of the Zagros Mountains, undergoing low temperature and relatively high rainfall, the wind has very little role in the erosion of the soil. The results also showed that due to global warming, the areas with severe wind erosion would expand.
4- Discussion and Conclusion
Because Iran is located in the arid and semi-arid belt of the Earth, it can regarded as one of the areas susceptible to wind erosion. This study indicated that the climate factors, the most important of which are temperature and rainfall, have created the conditions for wind erosion in Iran. Wind erosion is so severe in the large parts of the study area. Only in the highlands of the Zagros Mountains, due to higher rainfalls and lower temperatures and thus maintaining the soil moisture, the wind cannot cause soil erosion. This study showed that global warming could play a major role in the development of the regions where the wind erosion is severe. Hence, in land use and infrastructure planning, the type of the wind erosion in the current period as well as in the future periods must take into account.