Abstract
Quantitative relationship between modern pollen assemblage and altitudinal vegetation belt is crucial for the reconstruction of paleovegetation in the mountain regions. Modern pollen analysis on 70 topsoil samples was conducted across an altitudinal transect (1100-4500 m) on the eastern slope of Gongga Mountain in the eastern Tibetan Plateau with an elevation interval of 50 m. Distributions of major pollen types along the transect indicated a weak correlation between Pinus pollen and the elevation. Distributions of Picea and Abies pollen (percentage sum of 2%-8%) could fairly indicate the elevation range of 2700-3700 m, as well as the subalpine dark coniferous forest and the timberline in the region. High percentage intervals of alpine types of Ericaceae, Cupressaceae and Cyperaceae were correlated to the high-elevation regions (3700-4500 m) dominated by alpine shrub meadow and alpine meadow. Seven altitudinal vegetation belts on the eastern slope of Gongga Mountain were well defined by discriminant analysis conducted on the modern pollen assemblages, as reflected by high values of probability of modern analog. Most of the modern pollen assemblages (88.5%) were typical for the vegetation types at their sampling locations. Thus, the relationship between the modern pollen assemblages and vegetation across the altitudinal transect based on discriminant analysis can be applied to the quantitative reconstruction of paleovegetation changes in the mountain regions of the eastern Tibetan Plateau.
Highlights
Quantitative relationship between modern pollen assemblage and altitudinal vegetation belt is crucial for the reconstruction of paleovegetation in the mountain regions
Previous modern pollen investigations have been limited to explore the relationships between surface pollen spectra, vegetation and climate conditions in the eastern regions [19,20], the western plateau [21], and the whole surface of the Tibetan Plateau (TP) on a large scale [8,12, 17,22]
Due to the marked changes of meterorological and hydrological conditions over relatively short distances, mountainous vegetation is very vulnerable to climate changes on different time scales [23]
Summary
The eastern slope of Gongga Mountain is characterized by a distinct environmental gradient from warm/dry conditions at low-elevation regions to cold/moisture environment at high-elevation slopes, due to the relative elevation difference of about 6500 m [28]. Altitudinal vegetation belts on the eastern slope of Gongga Mountain are composed of valley arid shrub and grass vegetation belt, agro-forest vegetation, evergreen broadleaved forest, mixed coniferous and broad-leaved forest, subalpine dark coniferous forest, alpine shrub meadow, alpine meadow, and alpine sparse vegetation (Figure 1). (iv) Mixed coniferous and broad-leaved forest (2400– 2800 m) is dominated by various species of Tsuga and deciduous trees of Betula and Acer, with some Euptolea pleiospermum, Sorbus, Carpinus, patchy community of Pinus armandii and a few Picea brachytyla. (v) Subalpine dark coniferous forest (2800–3700 m) is characterized by Picea brachytyla and Abies fabric, with patchy secondary forests of Betula, Salix and Sorbus, and some shrubs of Rhododendron and Bashania fangiana. (vi) Alpine shrub meadow (3700–4000 m) is mainly composed of shrub species of Rhododendron, and meadow of Kobresia and Festuca, with patchy shrubs of Sabina, Salix and Potentilla. Alpine sparse vegetation (4500–4900 m) occurs below the snow line, composed mainly of Saussurea, Soroseris, Arenaria, etc
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