جستجوی مقالات مرتبط با کلیدواژه « آب و هوای دیرین » در نشریات گروه « محیط زیست »

In this research we tried to investigate the respond of high part of Zagros Mountains to past climate change by studying a 300cm core was extracted from Lake Gahar. This region is as an important biome of oak forest of Iran. Then the aim of this investigation is to detect past climate condition by palynology and climate modeling. According to the pollen diagram of Lake Gahar, four main local pollen assemblage zones during Holocene consisting of two older zones GHA(depth of 300 to 290 cm), GHB (290 to 110 cm depth) and two more new zones GHC (depth 110 to 50 cm) and GHD (depth 50 to 0 cm) were identified. We also reconstructed the annual mean precipitation and temperature data over 40000 years by MCM (Macrophysical Climate Model). The results showed that two zones GHA and GHB beyond depth 300-110cm indicate vegetation of forest- steppe with dominant species of oak trees however Quercus pollen is evident in all zones. It seems that the abrupt decreasing of arboreal pollen, especially Quercus at a depth of 50 and 60 cm at the boundary between the two zones GHC and GHD is associated with unfavorable conditions for plant growth during this period. There are also upland herbs pollen types such as Poaceae crealia types and polygonium can be considered as evidence of the destruction of the region as a result of anthropogenic effects and heavy grazing and farming operations. It is also approved the existence of consecutive period of cold/wet and warm/dry period in the past climate of Gahar region by comparing the results of this study with results from other lakes in the northwest of Iran.

In this study we used pollen analysis for reconstruction of the past vegetation and paleoclimate of Lake Neor area located in the northwest of Iran. We detected the Late glacial,Younger Dryas and early Holocene by interpretation of pollen diagram of Neor Lake. As a result, the pollen analysis as well as dating results revealed some climatic events in Lake Neor area in the north-west of Iran. We also used some pollen ratios for detecting the wet and dry phases during early Holocene. The interpretation of pollen diagram of Lake Neor suggested that the forest- steppe vegetation cover with Artemisia dominated in the Neor region during early Holocene. There are also some evidences that show the usefulness of palynology method as an appropriate paleoclimatic technique in Lake Neor area for understanding the vegetation change in the context of the global climate change during late-glacial to mid-Holocene.