Neogene floras and palaeoclimatic estimates from various sites of South-West China

Neogene climates and vegetation history of western Yunnan are reconstructed on the basis of known fossil plants using the Coexistence Approach (CA) and Leaf Margin Analysis (LMA). Four Neogene leaf floras from Tengchong, Jianchuan and Eryuan in southwestern China are analyzed by the CA, and the paleoclimatic data of one Miocene carpoflora from Longling and three Pliocene palynofloras from Longling, Yangyi and Eryuan are used for comparison. The Miocene vegetation of the whole of West Yunnan is subtropical evergreen broad-leaved forest, and a similar mean annual precipitation is inferred for Tengchong, Longling and Jianchuan. However, by the Late Pliocene a large difference in vegetation occurred between the two slopes of Gaoligong Mountain, western Yunnan. The region of Tengchong retained a subtropical evergreen broad-leaved forest vegetation, whereas in Yangyi and Eryuan a vertical vegetation zonation had developed, which consists, in ascending order, of humid evergreen broad-leaved, needle and broad-leaved mixed evergreen, and coniferous forests. Distinctively, the Late Pliocene vegetational patterns of West Yunnan were already very similar to those of the present, and the Pliocene mean annual precipitation in Tengchong was markedly higher than that of Yangyi and Eryuan. Considering that the overall vegetation of West Yunnan and the precipitation at Yangyi and Eryuan have undergone no distinct change since the Late Pliocene, we conclude that the Hengduan Mountains on the northern boundary of West Yunnan must have arisen after the Miocene and approached their highest elevation before the Late Pliocene. Furthermore, the fact of the eastern portion of the Tibetan Plateau underwent a slight uplift after the Late Pliocene is also supported.

Pollen and macroremains from four profiles from site Samerberg 1

Pollen and macrofossil analysis of lake sediments revealed the complete development of vegetation from Riss late-glacial to early Würm glacial times at Samerberg (12°12' E, 47°45' N, 600 m a.s.l) on the northern border of the Alps. The pollen bearing sediments overlie three stratigraphic units, at the base a ground-moraine, then a 13 m thick layer of pollen free silt and clay, and then a younger moraine; all the sediments including the pollen bearing sediments, lie below the Würm moraine. The lake, which had developed in an older glacial basin, became extinct, when the ice of the river Inn glacier filled its basin during Würm full-glacial time at the latest. One interglacial, three interstadials, and the interdigitating treeless periods were identified at Samerberg. Whereas the cold periods cannot be distinguished from one another pollenanalytically, the interglacial and the two older interstadials have distinctive characteristics. A shrub phase with Juniperus initiated reforestation and was followed by a pine phase during the interglacial and each of the three interstadials. The further development of the interglacial vegetation proceeded with a phase when deciduous trees (mainly Quercus, oak) and hazel (Corylus) dominated, though spruce (Picea) was present at the same time in the area. A phase with abundant yew (Taxus) led to an apparently long lasting period with dominant spruce and fir (Abies) accompanied by some hornbeam (Carpinus). The vegetational development shows the main characteristics of the Riss/Würm interglacial, though certain differences in the vegetational development in the northern alpine foreland are obvious. These differences may result from the existence of an altitudinal zonation of the vegetation in the vicinity of the site and are the expression of its position at the border of the Alps. A greater age (e.g. the Holsteinian) can be excluded by reason of the vegetational development, and is also not indicated at first sight from the geological and stratigraphical data of the site. Characteristic of the Riss/Würm vegetational development in southern Germany - at least in the region between Lake Starnberg/Samerberg/Salzach - is the conspicuous yew phase. According to absolute pollen counts, yew not only displaced the deciduous species, but also displaced spruce preferentially, thus indicating climatic conditions less favourable for spruce, caused by mild winters (Ilex spreading!) and by short-term low precipitation, indicated by the reduced sedimentation rate. The oldest interstadials is bipartite, as due to the climatic deterioration the early vegetational development, culminating in a spruce phase, had been interrupted by another expansion of pine. A younger spruce-dominated period with fir and perhaps also with hornbeam and beech (Fagus) followed. An identical climatic development has been reported from other European sites with long pollen sequences (see chapter 6.7). However, different tree species are found in the same time intervals in Middle Europe during Early Würm times. Sediments of the last interglacial (Eem or Riss/Würm) have been found in all cases below the sediments of the bipartite interstadial, and in addition one more interstadial occurs in the overlying sediments. This proves that Eem and Riss/Würm of the north-european plain resp. of the alpine foreland are contemporaneous interglacials although this has been questioned by some authors. The climax vegetation of the second interstadial was a spruce forest without fir and without more demanding deciduous tree species. The vegetational development of the third interstadial is recorded fragmentary only. But it has been established that a spruce forest was present. The oldest interstadial must correspond to the danish Brørup interstadial as it is expressed in northern Germany, the second one to the Odderade interstadial. A third Early Würm interstadial, preserved fragmentarily at Samerberg, is known from other sites. The dutch Amersfoort interstadial most likely is the equivalent to the older part of the bipartite danish Brørup interstadial.

Deforesting Europe: pollen-inferred Holocene land cover change using the 'pseudobiomization' approach

Maps of continental-scale land cover are utilized by a range of diverse users but whilst a range of products exist that describe present and recent land cover in Europe, there are currently no datasets that describe past variations over long time-scales. User groups with an interest in past land cover include the climate modelling community, socio-ecological historians and earth system scientists. Europe is one of the continents with the longest histories of land conversion from forest to farmland, thus understanding land cover change in this area is globally significant. This study applies the pseudobiomization method (PBM) to 982 pollen records from across Europe, taken from the European Pollen Database (EPD) to produce a first synthesis of pan-European land cover change for the period 9000 BP to present, in contiguous 200 year time intervals. The PBM transforms pollen proportions from each site to one of eight land cover classes (LCCs) that are directly comparable to the CORINE land cover classification. The proportion of LCCs represented in each time window provides a spatially aggregated record of land cover change for temperate and northern Europe, and for a series of case study regions (western France, the western Alps, and the Czech Republic and Slovakia). At the European scale, the impact of Neolithic food producing economies appear to be detectable from 6000 BP through reduction in broad-leaf forests resulting from human land use activities such as forest clearance. Total forest cover at a pan-European scale moved outside the range of previous background variability from 4000 BP onwards. From 2200 BP land cover change intensified, and the broad pattern of land cover for preindustrial Europe was established by 1000 BP. Recognizing the timing of anthropogenic land cover change in Europe will further the understanding of land cover-climate interactions, and the origins of the modern cultural landscape.