Search

• Uncertainties in paleo-habitat definition limit adequate vegetation reconstruction. • Plant functional indicators are of limited value for paleovegetation reconstruction. • Biome scale analyses of functional types rarely apply to plant communities. • Underlying basis for whole-plant modal PFT construction and use is described. • Modal PFTs are more functionally informative than individual traits. Plant functional traits are widely applied in models that simulate the effects of climate change on biodiversity and resource management. Here the aim is to examine the potential role of specific plant functional traits and their whole-plant syndromes (Plant Functional Types or PFTs as specific 'modal' trait assemblages) as indicators of vegetation response to climate change, past, present and future. Because plant functional characteristics have evolved through time, it is widely argued that models of vegetation performance under future climates should benefit from a study of plant response under previous climates. This paper presents an overview first, of developmental concepts underlying the current use of PFTs as indicators of plant response to environmental change, second, implications arising from species acclimation and third, process-based models used in reconstruction of vegetation under mainly Holocene environments but also with respect to present and future climates. In this regard the role of individual functional traits in 'biomization' procedures in vegetation response models is briefly discussed. It is concluded that, while PFTs possess limited indicator value at biome scale, uncertainties in the delimitation of local paleohabitats greatly restrict their use as indicators for paleovegetation reconstruction at community level. Emerging hypotheses are: 1) A whole-plant system of modal PFTs based on a novel set of functional traits can provide an improved alternative to PFTs and traits used in models of vegetation response to climate change, 2) Modal PFTs are potentially more efficient indicators of vegetation response to climate change than individual traits, 3) Improved plant functional selection criteria can lead to more efficient parameterization of Earth System and Dynamic Global Vegetation Models. [ABSTRACT FROM AUTHOR]

Reconstruction of past vegetation change is critical for better understanding the potential impact of future global change on the fragile alpine ecosystems of the Qinghai-Tibetan Plateau (QTP). In this paper, pollen assemblages comprising 58 records from the QTP, spanning the past 15 kyrs, were collected to reconstruct biome compositions using a standard approach. Six forest biomes were identified mainly on the southeastern plateau, exhibiting a pattern of gradual expansion along the eastern margin during early to mid-Holocene times. The alpine meadow biome was separately identified based on an updated scheme, and showed notable westward expansions towards lower latitudes and higher altitudes during early Holocene times. Consistent patterns of migration could also be identified for the alpine steppe biome, which moved eastward during the late Holocene after 4 ka. As the dominant biome type, temperate steppe was distributed widely over the QTP with minor migration patterns, except for a progressive expansion to lower altitudes in the late Holocene times. The desert biome was inferred mainly as covering the northwestern plateau and the Qaidam Basin, in relatively restricted areas. The spatial distribution of the reconstructed biomes represent the large-scale vegetation gradient on the QTP. Monsoonal precipitation expressed predominant controls on the development of alpine ecosystems, while the variations in desert vegetation responded to regional moisture brought by the mid-latitude Westerlies. Temperature changes played relatively minor roles in the variations of alpine vegetation, but exerted more significant impacts on the forest biomes. • Fossil pollen based biome reconstruction on the Qinghai-Tibetan Plateau since 15 ka. • Spatial/temporal patterns of biome changes on the QTP were illustrated and examined. • Forest and alpine meadow biomes experienced migrations during the mid-Holocene. • Vegetation changes responded closely to moisture changes with spatial divergence. [ABSTRACT FROM AUTHOR]

Lacustrine-peat sediments from the Oskino-09 borehole in Western Siberia, which span the last 7.5 cal ka BP, were sampled for pollen and plant macro-remains to better understand regional climatic changes and the position of the forest-steppe border. Analysis of palynological assemblages indicate that meadow-steppe landscapes occupied the largest area in the middle of the Holocene (7.5–4.7 cal ka BP) due to reduced effective moisture during a warm climate interval. A subsequent gradual decrease in temperatures and evaporation led to an increase in effective moisture and emergence of birch groves during 4.7–2.0 cal ka BP, with short interruptions at ca. 3.3 and 2.5 cal ka BP. The expansion of pine forests and the advance of taiga to the south were recorded at ca. 2.0 cal ka BP. There is little evidence for significant human impact on forest-steppe belt evolution, and specifically evidence for anthropogenic deforestation on the southern border of the taiga is lacking. Human activities did not start to impact forests until the emergence of semi-nomadic cattle breeding in the Iron Age. A methodological finding of this paper is that we show that the Landscape Reconstruction Algorithm (LRA) is not always reliable and often overestimates forested areas. • Forests area is overestimated by quantifying landscape assessment in forest-steppe. • Largest meadow-steppe areas were due to reduced effective moisture ca 7.5–4.7 ka BP. • Intensive spread of coniferous in Western Siberian forest-steppe ca 2.0 ka BP. • Human impact on the landscape of Western Siberian forest-steppe was not significant. [ABSTRACT FROM AUTHOR]