30,000 years of landscape and vegetation dynamics in a mid-elevation Andean valley

Investigating Environmental (Climate and Vegetation) Change of Eastern Amazonia During Pleistocene and Holocene Using Multi-Proxy Analysis

Response of prehistoric human activity to environmental changes since 7,000 cal yr BP in Nenjiang River Basin, northeast China

The Lateglacial and Early Holocene vegetation dynamics: New multi-proxy data from the central Belarus

The Ecuadorian Andes in northwestern South America are well known for being among the hot spots of global vascular plant diversity due to their complex topography (uplift of the mountain chain), varying climatic conditions and different vegetation types. Despite its high biodiversity level, the Ecuadorian Andes represent a most threatened and poorly studied landscape. Especially the páramo and mountain ecosystems are subject to overgrazing, burning, cultivation and deforestation caused by the expansion of human activity during the last decades. The knowledge of palaeoecology and landscape dynamics is important in order to understand past processes that played a major role in the development of the ecosystems and Ecuadorian landscapes of today. Nevertheless only a limited number of palaeoecological studies are available from the Ecuadorian Andes. This thesis presents palynological analyses carried out at three different sites in the central and southern Ecuadorian Andes region to better understand the past vegetation changes, climate and fire dynamics as well as human impact since the late Pleistocene. The analysis of the sediment core El Cristal, located on the eastern slope at the Protective Forest Corazón de Oro in southeastern Ecuador reveals changes in the vegetation distribution, climate, fire regime and human impact since late Pleistocene. During the late Pleistocene mountain forest was the main vegetation type. In particular, there is evidence of a Polylepis forest which does not occur today. Nevertheless there is also evidence of relatively high proportion of páramo, which suggest that an open mountain forest occupied the region. The presence of páramo taxa during the late Pleistocene, points to an upper forest line (UFL) at a markedly lower elevation. The transition from the late Pleistocene to the early mid-Holocene was characterized by mountain forest and a stable proportion of páramo vegetation. However, after ca. 4000 cal yr BP, the Polylepis forest decreased, probably because of an increase in fire frequency. During the mid- to late Holocene the composition of the vegetation changed. The mountain forest was less frequent and the páramo vegetation expanded. Higher proportions of Asteraceae and Muehlenbeckia/Rumex (since ca. 1380 cal yr BP) reflect landscape disturbance probably by human impact. Fires were recorded throughout the late Pleistocene but were more frequent during the wetter late Holocene, which suggests that they were of anthropogenic origin. The pollen record from Cajanuma valley, in the western slope at the Podocarpus National Park, southern Ecuador, reveals environmental changes since the late Glacial. During the late Glacial, herb páramo rich in Poaceae, Cyperaceae and Gentianaceae covered the area. The UFL occurred at a much lower elevation than today. The early to mid-Holocene is characterized by partial replacement of treeless páramo by a mountain forest (Symplocos taxa), which moves into higher elevations where it is today. During the mid- to late Holocene there is evidence of a vegetation change. The páramo re-expanded with the dominance of Poaceae and high presence of Huperzia and Cyatheaceae. During the late Holocene páramo was the main vegetation type that covered the area. Fires became frequent since the late Holocene. The Anteojos valley pollen record, which is located in the western slope at the Llanganates National Park, central Ecuadorian Andes, yields a detailed environmental reconstruction of the past ca. 4100 years. Páramo vegetation had a dominant and stable occurrence in the study area (Poaceae, Cyperaceae and Asteraceae); especially between ca. 4100 to 3100 cal yr BP. Between ca. 3100 to 2100 cal yr BP páramo decreased followed by a slight expansion of mountain forest (Moraceae/Urticaceae, Trema, Celtis and Macrocarpaea). From ca. 2100 cal yr BP to the present páramo once again became more frequent with stable occurrence of mountain forest taxa. Low frequencies of fires were evidenced throughout the record but there is evidence of a slight increase during ca. 4100 to 3100 cal yr BP.

Long-term vegetation dynamics along altitudinal and longitudinal gradients in the Hyrcanian forest region (northern Iran)

Holocene environmental changes inferred from an oxbow lake in a Mauritia palm swamp (aguajal) in the Madre de Dios region, southeastern Peru

Holocene climatic and environmental change from pollen records of lakes Zempoala and Quila, central Mexican highlands

In order to study the stability and dynamics of highly biodiverse mountain rain forest and paramo ecosystems, the late Pleistocene and Holocene climate and fire variability as well as human impact in the Podocarpus National Park region, the first comprehensive palaeoenviremental study from the southeastern Ecuadorian Andes will be presented. An initial study of recent vegetation/modern pollen rain relationship on an altitudinal transects between 1800 and 3200 m elevation in the mountain forest and (sub)-paramo vegetation of the ECSF (Estacion Cientifica San Francisco) research area provide important background information in the interpretation of late Quaternary pollen records. Cluster analysis on the pollen rain data by CONISS, clearly reflects the zonation of the different vegetation units, lower mountain forest (LMF), upper mountain forest (UMF) and (sub)-paramo. A relatively high number of pollen taxa correspond to the altitudinal distribution of genera and families of modern vegetation. The modern tree line in the research area is at ca. 2790 m, which is pointed out by an increase of (sub)-paramo taxa and a decrease of mountain forest taxa in the pollen rain data. Palaeoenvironmental changes, inferred from 9 lake, peat bog and soil deposits, collected at different elevations between ca. 2000 and 3300 m, were investigated by pollen, spores and charcoal analysis, in combination with XRF- and magnetic susceptibility-scanning on the lake sediment cores. During the late Pleistocene from ca. 21,000 to 11,200 cal yr BP, grass-paramo vegetation occurred at the Tiro-Pass (2810 m), reflecting cold and moist climatic conditions as well as a shift of vegetation zones into lower elevation during this period. During the transition from late Pleistocene to early Holocene from ca. 14,500 to 9700 cal yr BP, arboreal taxa, mainly Weinmannia strongly increase at Laguna Cocha Caranga (2710 m), reflecting a raise in temperature. The early Holocene from ca. 11,200 to 8900 cal yr BP (El Tiro-Pass) is characterised by an increase of temperature and moisture, as well as a shift of vegetation zones into higher elevation. During the mid Holocene period, from ca. 8900 to 3300 cal yr BP, upper mountain forest vegetation developed at the El Tiro-Pass, where subparamo vegetation occurred in recent times, suggesting a warmer climate than present day at this elevation. XRF-scanning data from Laguna Rabadilla de Vaca (3310 m) reflects a drier period from ca. 8990 to 6380 cal yr BP and a wetter period from ca. 6380 to 3680 cal yr BP. The green algae Botryococcus braunii, Isoetes and Cyperaceae were used to reconstruct Holocene wet/dry phases at Laguna Cocha Caranga. Drier climatic conditions occurred from ca. 9700 to 6900 cal yr BP and from ca. 4200 to 1300 cal yr BP. From ca. 6900 to 4200 cal yr BP and from ca. 1300 cal yr BP to modern time"s wetter climatic conditions occurred. During the late Holocene, modern climatic conditions, as well as recent vegetation established since ca. 3680 cal yr BP at Laguna Rabadilla de Vaca and since ca. 3300 cal yr BP at the El Tiro-Pass. An increase of fire intensity during the early to mid Holocene period after ca. 9700 cal yr BP at Laguna Cocha Caranga and after about 7500 cal yr BP at the El Tiro-Pass reflects beginning human impact on the ecosystem in the Podocarpus National Park region. High occurrence of grasses document, that past fires have markedly influenced the floristic composition of the mountain rain forest and paramo ecosystems during the mid to late Holocene period. The reduction of fire intensity coupled with a decrease of grasses after ca. 1300 cal yr BP (Laguna Cocha Caranga) and between ca. 970 to 400 cal yr BP (Upper Rio San Francisco valley), coupled with a missing of Zea mais pollen, suggests a reduction and/or absence of human activities, may be as a result of political unrest. After the reduction and/or absence of human influence the mountain forest vegetation starts to recover.

Reconstruction of climatic and environmental changes in NW Romania during the early part of the last deglaciation (∼15,000–13,600 cal yr BP)

We obtained a 15 m drill core from Deukryang Bay on the southwest coast of Korea, which is now an area of reclaimed land used for agriculture. We investigated changes in the depositional environment and hydrological climate responses to sea level changes using sedimentary facies, radiocarbon ages, grain-size analysis, total organic carbon (TOC), total sulfur (TS), and stable carbon isotopes (δ13C). Sediment deposition began at 12,000 cal yr BP and was divided into four stages based on changes from fluvial to intertidal environments related to Holocene marine transgression events. Stage 1 (>10,000 cal yr BP) is represented by fluvial sediments; Stage 2 (10,000–7080 cal yr BP) is represented by the deposition of mud facies in an intertidal zone in response to sea level rise; Stage 3 (7080–3300 cal yr BP) was a period of gradually descending sea level following the Holocene maximum sea level and is characterized by gradual changes in TOC, TS, and C/S ratios compared with the mud facies of Stage 2. Stage 4 (3300 to present) was deposited in a supratidal zone and contains low TS and an abundance of TOC. Based on our TS and C/S ratio results, the south coast of Korea was mainly affected by sea level rise between 7000 and 3000 cal yr BP, during the middle Holocene. At 3000 cal yr BP, sea level began to stabilize or gradually decrease. In addition, changes in δ13C values are clearly observed since ca. 5000 cal yr BP, in particular, large hydrological changes via freshwater input are confirmed in 4000–3000 cal yr BP. We consider these shifts in freshwater input indicators of an increased influence of El Niño and La Niña conditions, related to the weakening of the East Asian Summer Monsoon (EASM) and changes in sea surface temperature (SST) of the Western Pacific Ocean during the middle Holocene climatic optimum (between 7800 and 5000 cal yr BP). The cooling periods of SST in East Asia between 8400 and 6600 cal yr BP reported from the west coast of Korea are related closely to changes in vegetation (as evidenced by δ13C) from 7700 cal yrs BP to the present in the southwest coast of Korea. We interpret the freshwater input events at 4000–3000 cal yr BP to be related to changes in SST in response to the weakening of the EASM on the southwest coast of Korea. However, additional research is needed to study the southward migration effect of the westerly jet related to SST and atmospheric circulation controlling terrestrial climate in the middle Holocene.

Late Quaternary environmental changes in Marguerite Bay, Antarctic Peninsula, inferred from lake sediments and raised beaches

Dynamic early Holocene vegetation development on the Faroe Islands inferred from high-resolution plant macrofossil and pollen data

Environmental context of a Neolithic site at Beifudi, north-west Hebei Province, China

Understanding the spatiotemporal monsoonal variability during the Holocene helps in understanding the rise and fall of many civilizations. In this study, a 2.65 m high palaeo lake sedimentary profile from the Kumaun Lesser Himalaya, Uttarakhand State, India was pollen analysed to reconstruct the variability in the monsoonal precipitation during the Middle Holocene. The study revealed that between ~7522 and 7216 cal yr BP, conifers dominated mixed broad-leaved forests occurred around the landscape of the study area, indicating a less cold and dry climate with decreased monsoon precipitation. Broad-leaved taxa during this phase show increased values considerably, indicating amelioration in climatic condition, which could be, in global perspective, broadly falling within the time-interval of the Holocene Climate Optimum (HCO; 7000–4000 BP). Between ~7216 and 6526 cal yr BP, dense conifers-dominated mixed broad-leaved forests transformed the conifers-dominated broad-leaved forests around the study area under a cold and drier climate with further reduction in monsoon precipitation. Subsequently, between ~6526 and 5987 cal yr BP, conifers-dominated broad-leaved forests continued to grow, but with lesser frequencies, around the study area under a comparatively less cold and dry climate with reduced monsoon precipitation. Finally, between ~5987 and 5817 cal yr BP, the frequencies of conifers-dominated broad-leaved forests further decreased around the landscape of the study area under a comparatively lesser cold and dry climate, probably indicating decreased monsoonal precipitation. Hence, the present study mainly showed the dominance of conifers forests around the study area between ~7522 and 7216 cal yr BP, ~7216 and 6526 cal yr BP, ~6526 and 5987 cal yr BP and between ~5987 and 5817 cal yr BP; however, broad-leaved forests also demonstrated increasing tendency between ~7522 and 7216 cal yr BP in the milieu of cold and dry climates. Moreover, the study also revealed that a lake was formed around 7522 cal yr BP along the Kulur River, a tributary of Saryu River around the study area and existed until 5817 cal yr BP.

Holocene vegetation variation in the Daihai Lake region of north-central China: a direct indication of the Asian monsoon climatic history