关中平原全新世环境演变

HOLOCENE ENVIRONMENTAL CHANGES IN THE GUANZHONG PLAIN

根据陕西歧山等剖面高分辩率孢粉分析和古土壤类型研究得知 ,全新世大暖期关中地区发育的土壤为淋溶型森林土壤 ,而非过去所认为的半干旱气候下的森林草原型的黑垆土 ;该区全新世可分为三个时期 9个阶段 ,全新世早、晚期分别包括 2个阶段 ,中期包括 5个阶段 ;植被类型以落叶阔叶林为主 ,间有森林草原出现 ;中全新世气候最佳阶段年均温比今高约 3℃ ,年均降水量比今多 2 0 0mm左右。

According to the high resolution sporo-pollen analysis in the Qishan profile of Shaanxi Province and the study on the paleosol type, the paper has discussed the Holocene environmental changes in the Guanzhong Plain. The clay grouting in soil developing in Middle Holocene in the area was stronger, lumpy clay films developed well, the content of CaCO 3 is less than 1%, and the illuvial horizon of CaCO 3 has migrated from the clay grouting horizon of the paleosol. This materials indicated that it was eluvial forest soil whose intensity was no less than Luvic cinnamon soil and it was not Dark loessial soil that developed under the forest-steppe environment so-called in the past. The sporo-pollen analysis of 54 samples in Qishan profile indicates the content of sporo-pollen is rich and there is more than 100 grains in each sample, including about 50 families and genuses. The majority of the sporo-pollen constitute is herbaceous pollen. The content of arbor pollen is less than 10%, including Quercus, Pinus, Ailanthus, Carpinus, Ulmus, Alnus, Corylus, Castanea, Julance, Platycarya, Pterocarya, Picea, Rhus and so on. The pollen of herbaceous are Compositae, Artemisia, Chenopodiaceae, Gramineae, Cruciferae, Rubiaceae and so on. According to the content and constitute changes of arbor pollen, Holocene vegetation and climate changes can be divide into three periods and nine stages. The Early Holocene can be divided into two stages. The First stage is deciduous broadleaf forest and the second stage is forest-steppe. The Middle Holocene can be divided into five stages. The first, the third and the fifth are deciduous broadleat forest and the rest are forest-steppe. Luvic cinnamon soil developed well and the climate was suitable in the first stage. The mean annual temperature was 3℃ higher and the mean annual rainfall is about 200mm more than present. The Late Holocene can be divide into two stages. The first is forest-steppe and the second is deciduous broadleaf forest.