9 resultados para bioprospection mixed forest

em Publishing Network for Geoscientific


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The discovery of a neolithic pile field in the shallow water near the eastern shore of the Degersee confirmed earlier palynological and sedimentological studies stating that early man was active in the region since more than 6000 years. The already available off-site data were freshly assessed, completed by additional data from old and new cores and the interpretations revised. A common time scale for the off-site data and the on-site data was obtained by AMS dating of terrestrial macro remains of the neolithic section of off-site core De_I+De_H. The ages can thus be parallelled with AMS ages of construction timber on-site. Pollen analyses from all cores provide a further time scale. The continuously and densely sampled pollen profile of the profundal zone embracing the entire Late glacial and Holocene serves as a reference. From the Boreal onwards the relative ages are transformed by AMS ages and varve counts into calibrated and absolute. A transect cored close to the neolithic pile field across the lake marl-platform demonstrates its geological architecture in the shallow water since the Lateglacial. Studies of the microfabric of thin sections of drilled cores and of box cores from the excavations demonstrate that neolithic settlements now at 2-3,5 m water depth had been erected on lake marl freshly fallen dry, thus indicating earlier lake levels dropped by 1.5-2 m. The neolithic section of the highly resolved off-site profile in the lake=s profundal zone has laminated and calcareous zones alternating with massive ones. Assemblages of diatoms and concentrations of trace elements changing simultaneously characterise the calcareous sections as deposits of low lake levels that lasted between some 40 and more than 300 years. The ages of discovered lake shore dwellings fall into calcareous segments with low lake levels. From the end of the Upper Atlantic period (F VII) appear Secondary Forest Cycles in the beech forest, a man-made sequence of repeated vegetational development with an identical pattern: With a decrease of beech pollen appear pollen of grasses, herbs and cultural indicators. These are suppressed by the light demanding hazel and birch, those again by ash, and finally by the shade demanding beech forming a new pollen peak. Seven main Forest Cycles are identified In the upper Neolithic period each comprising some 250, 450 or 800 years. They are subdivided into subcycles that can be broken down by very dense sampling in even shorter cycles of decadal length. Farming settlers have caused minor patchy clearances of the beech-mixed-forest with the use of fire. The phases of clearance coincide with peaks of charcoal and low stands of the lake levels. The Secondary Forest Cycles and the continuous occurrence of charcoal prove a continued occupation of the region. Together with the repeated restoration of the beech climax forest they point to pulsating occupation probably associated with dynamic demography. The synchronism of the many palynological, sedimentological and archaeological data point to an external forcing as the climate that affects comprehensively all these proxies. The fluctuations of the activity of the sun as manifested in the residual d14C go largely along with the proxies. The initial clearances at the begin of the forest cycles are linked to low lake levels and negative values of d14C that point to dry and warm phases of a more continental climate type. The subcycles exist independent from climatic changes, indicating that early man acted largely independent from external forces.

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The Mediterranean Sea hydrology at the time of the Heinrich formation in the North Atlantic Ocean was analyzed by comparing sea surface temperatures (SSTs) and oxygen isotope composition of seawater (dw) changes during the past 75 kyr in two marine cores. These were compared to the palynological variations derived in the Mediterranean Sea core. During the last glacial the two oceanic SST records show similar and synchronous patterns, with several long-term cooling periods, ending by abrupt SST increases. At the time of the Heinrich events, cold SSTs and low salinity prevailed in the Mediterranean Sea. The freshwater budget was similar to the modern one, permitting the presence of a mixed forest on the Mediterranean borderlands. The post-Heinrich periods are marked by a freshwater budget decrease, limiting oak and fir tree growth in the Mediterranean region. Increase of precipitation or reduction of evaporation is observed before the Heinrich episode, and is associated with a well-developed mixed Mediterranean forest.

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This study presents a newly compiled dataset of modern pollen and climate data from 798 sites across Japan and the Russian Far East. This comprehensive reference dataset combined with the modern analogue technique (MAT) provides a powerful tool for pollen-based reconstruction of the Quaternary Northwest Pacific climate. Pollen-derived reconstruction of the modern climate at the reference pollen-sampling sites matches well with the estimated modern climate values (R2 values vary between 0.79 and 0.95, and RMSEP values vary between 5.8 and 9.7% of the modern climatic range for all nine tested variables). The successful testing of the method encourages its application to the fossil pollen records. We used a coarse-resolution pollen record from Lake Biwa to reconstruct glacial-interglacial climate dynamics in central Japan since ~438 kyr and compared it to the earlier reconstruction based on a less representative reference dataset. The current and earlier results consistently demonstrate that the coldest glacial intervals experienced pronounced cooling in winter and moderate cooling in summer, supporting the growth of cool mixed forest (COMX) where warm mixed forest (WAMX) predominates today. During the last glacial, maximum (~24 kyr BP) mean temperatures of the coldest (MTCO) and warmest (MTWA) month were about -13 °C (RMSEP = 2.34 °C) and 21 °C (RMSEP = 1.66 °C) respectively, and annual precipitation (PANN) was about 800 mm (RMSEP = 158.06 mm). During the thermal optimums of the interglacial intervals, the temperatures of the coldest and warmest month were above 0 °C and 25 °C respectively, leading to the reconstruction of WAMX and temperate conifer forest (TECO). Although both these vegetation types grow in the southern part of Japan today, WAMX requires warmer space. The presence of WAMX during marine isotope stages (MIS) 11 and 1, and its absence during MIS 9 and MIS 5 contradict the marine isotope and Antarctic ice records, suggesting that the latter two interglacials were the warmest of the last 800 kyr. The apparent contradiction allows at least three different explanations including low temporal resolution of the pollen record; different trends in CO2 concentrations during 'short' and 'long' interglacials; and regional climate variability and non-linear response of different regions to the global forcing. More definitive conclusions will be possible on the basis of forthcoming high-resolution pollen records from central Japan.

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This study reconstructs middle and late Holocene vegetation and climate dynamics in the Oshima Peninsula, SW Hokkaido, using the published method of biome reconstruction and modern analogue technique applied to the Yakumo pollen record (42°17'03''N, 140°15'34''E) spanning the last 5500 years. Two previously published matrices assigning Japanese plant/pollen taxa to the major vegetation types (biomes) are tested using a newly compiled dataset of 78 surface pollen spectra from Hokkaido. With both matrices showing strengths and weaknesses in reconstructing cool mixed and temperate deciduous forests of Hokkaido, the results suggest the necessity to consider the whole list of identified terrestrial pollen taxa for generating robust vegetation reconstructions for northern Japan. Applied to the fossil pollen data, both biome-reconstruction approaches demonstrate consistently that oak-dominated cool mixed forest spread in the study region between 5.5 and 3.6 cal ka BP and was subsequently replaced by beech-dominated temperate deciduous forest. The pollen-based climate reconstruction suggests this change in the vegetation composition was caused by a shift from cooler and drier than present climate to warmer and wetter, similar to modern conditions about 3.6 cal ka BP. Comparing the pollen-based reconstruction results with the published marine records from the NW Pacific, the reconstructed vegetation and climate dynamics can be satisfactorily explained by the greater role played by the warm Tsushima Current in the Sea of Japan and in the Tsugaru Strait during the middle and late Holocene. An increase in sea surface temperatures west and south of the study site would favour air temperature rise and moisture uptake and cause an increase in precipitation and snow accumulation in the western part of Hokkaido during the late Holocene.

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The Longling Coal Mine (W. Yunnan) is situated in an area of substantial geotectonic activity. Its Late Pliocene palynoflora is of considerable interest, since the area represents a centre of biodiversity. Eighty-two palynomorphs belonging to 61 families were recovered from the lignite. The palynoflora is dominated by angiosperms (68.3%), with ferns (24.4%), gymnosperms (4.9%) and algae (2.4%). Comparisons indicate that most of the palynoflora was derived from the Montane Humid Evergreen Broad-leaved Forest, with lesser contributions from the Tsuga dumosa Forest and Evergreen Coniferous Broad-leaved Mixed Forest, as well as the Montane Mossy Evergreen Broad-leaved Forest. This indicates that the Late Pliocene climate was cooler than that of the present. In the course of the accumulation of the lignite, the climate underwent five major phases of warming and cooling.

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Palynological investigations of sediments from northern Bavaria (Rhön, Grabfeld, Lange Berge) reveal the Late Glacial and Postglacial history of the regional vegetation. The older sedirnents were found in the Rhön (Schwarzes Moor) and date back into the Bölling Period. At the end of that period pine spread into the Grabfeld. In both areas Lacher Tuff has been found. A radiocarbon date of 10,300 BP was found for the Late Glacial - Postglacial transition and one of 9300 BP for the Preboreal - Boreal transition. Hazel reached its highest values in the Rhön around 7,400 BP. During the Atlanticum a deciduous mixed oak forest covered the Rhön and Grabfeld regions. Beech dominated since the Subatlanticum. In the Lange Berge region, however, a mixed forest with Fagus, Picea, Pinus and Abies developed. In the Rhön first anthropogenic influence was found during the Latene Period. The boundary between zone IX and X has been dated at 820 A.D., and the start of extensive forest clearances at 1000 A. D. A culmination of landuse was found for the Medieval Period. At the end of that period however the Rhön was deserted. New forest clearances started around 1500 A.D., but were interrupted by the 'Thirty Years War'. Afterwards the Rhön got its present appearance.

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We analyzed the abundance of Scots pine regeneration in a 257 ha wildfire in an inner-alpine forest. We sampled regeneration, percent soil cover by classes, physical and chemical properties of topsoils (A horizon, 0-5 cm) under four fire severity levels (unburned, moderate, moderate/high, high severity). 5 plots per severity level, circular (R= 3m). Analysis methods for soil properties as described in the paper.

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Notes from Henrik de Nie: The project started as a phenological study in cooperation with the (Dutch) meteorological institute (KNMI) to register the time of arrival of Fitis and Tjiftaf. During 1951 to 1969 he went every day to the wood (except 1966, in this year his wife died). Thereafter he went no more daily, but because he knew the wood very well and he was free to choice the day on which he did a survey, therefore he choose days with relatively good weather. He did not observe very common bird species, maybe because they are dependent on nest boxes and he did not want to be dependent on the management of the nest box-people (in fact I forgot precisely his arguments, and now I cannot ask him this): Common Starling; Eurasian Tree Sparrow (not common); Great Tit; Eurasian Blue Tit Pieter mentioned 14 species that scored many zero values or only one observation: Stock Dove; Common Cuckoo; Lesser Spotted Woodpecker; Eurasian Golden Oriole; Eurasian Nuthatch; Short-toed Treecreeper; Common Nightingale; Marsh Warbler; Lesser Whitethroat; Goldcrest; Common Firecrest (after 1970 he had difficulties in hearing these two species); Spotted Flycatcher; Eurasian Bullfinch; Black Woodpecker He also mentioned species that he found much fewer as: European Greenfinch; European Pied Flycatcher; Long-eared Owl; Red Crossbill; Sedge Warbler; Icterine Warbler; Eurasian Woodcock; Eurasian Siskin; European Green Woodpecker; Great Spotted Woodpecker; Eurasian Hobby; Western Barn Owl; Woodlark; Common Wood Pigeon; Little Owl; European Crested Tit; Hawfinch. But for these species I think that observations are strongly dependent on the number of visits to the wood. Also here, many zeros and few 1 x during the whole series of visits.

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Detailed knowledge of forest cover dynamics is crucial for many applications from resource management to ecosystem service assessments. Landsat data provides the necessary spatial, temporal and spectral detail to map and analyze forest cover and forest change processes. With the opening of the Landsat archive, new opportunities arise to monitor forest dynamics on regional to continental scales. In this study we analyzed changes in forest types, forest disturbances, and forest recovery for the Carpathian ecoregion in Eastern Europe. We generated a series of image composites at five year intervals between 1985 and 2010 and utilized a hybrid analysis strategy consisting of radiometric change classification, post-classification comparison and continuous index- and segment-based post-disturbance recovery assessment. For validation of the disturbance map we used a point-based accuracy assessment, and assessed the accuracy of our forest type maps using forest inventory data and statistically sampled ground truth data for 2010. Our Carpathian-wide disturbance map achieved an overall accuracy of 86% and the forest type maps up to 73% accuracy. While our results suggested a small net forest increase in the Carpathians, almost 20% of the forests experienced stand-replacing disturbances over the past 25 years. Forest recovery seemed to only partly counterbalance the widespread natural disturbances and clear-cutting activities. Disturbances were most widespread during the late 1980s and early 1990s, but some areas also exhibited extensive forest disturbances after 2000, especially in the Polish, Czech and Romanian Carpathians. Considerable shifts in forest composition occurred in the Carpathians, with disturbances increasingly affecting coniferous forests, and a relative decrease in coniferous and mixed forests. Both aspects are likely connected to an increased vulnerability of spruce plantations to pests and pathogens in the Carpathians. Overall, our results exemplify the highly dynamic nature of forest cover during times of socio-economic and institutional change, and highlight the value of the Landsat archive for monitoring these dynamics.