The surface pollen of the woodland–steppe ecotone in southeastern Inner Mongolia, China

Abstract

Surface pollen deposition in a modern woodland–steppe ecotone in the southeastern edge of the Inner Mongolia Plateau, situated between the deciduous broadleaved forest zone and the steppe zone in Asia, has been investigated. The following pollen and spore groups can be classified according to the relationship between surface pollen and plant community: (1) pollen group representing the whole study region: Artemisia, Betula, Chenopodiaceae, Polygonaceae and Plantago; (2) pollen group representing a vegetation zone: Pinus; (3) pollen and spore group representing a certain community type: Quercus, Picea, Ostryopsis, Corylus and spores; and (4) pollen group having a low representation: Ulmus, Gramineae, Leguminosae and Compositae. According to the pollen composition in each vegetation zone, four vegetation zones of the investigated area could be characterized by the following combinations of pollen types: (1) woodland zone: Betula–Pinus–Artemisia; (2) woodland–grassland zone: Betula–Artemisia; (3) woodland–steppe zone: Artemisia–Betula–Chenopodiaceae; and (4) steppe zone: Artemisia–Chenopodiaceae. Some ratios of various pollen types have been proved to be better at indicating the vegetation gradient than single pollen types. For example, C/A (Chenopodiaceae/ Artemisia), A/B ( Artemisia/ Betula) and AP/NAP (Arboreal pollen/Non-Arboreal Pollen) show distinctly the gradient from the woodland zone to the steppe zone. This investigation has a future application for the reconstruction of Holocene vegetation and climate history in the investigated area. Various pollen combinations can be used as `indicator units' for the diagnosis of vegetation types from fossil pollen analysis. Some problems of the interpolation of vegetation from fossil pollen data in the semi-arid area have also been discussed. High Artemisia pollen value do not indicate an Artemisia-dominated steppe vegetation due to the under-representation of Gramineae pollen. Plantago pollen in semi-arid and arid area can hardly be regarded as an indicator of human interference.