Tracing the origin of Arctic driftwood

Arctic environments, where surface temperatures increase and sea ice cover and permafrost depth decrease, are very sensitive to even slight climatic variations. Placing recent environmental change of the high-northern latitudes in a long-term context is, however, complicated by too short meteorological observations and too few proxy records. Driftwood may represent a unique cross-disciplinary archive at the interface of marine and terrestrial processes. Here, we introduce 1445 driftwood remains from coastal East Greenland and Svalbard. Macroscopy and microscopy were applied for wood anatomical classification; a multi-species subset was used for detecting fungi; and information on boreal vegetation patterns, circumpolar river systems, and ocean current dynamics was reviewed and evaluated. Four conifer (Pinus, Larix, Picea, and Abies) and three deciduous (Populus, Salix, and Betula) genera were differentiated. Species-specific identification also separated Pinus sylvestris and Pinus sibirica, which account for ~40% of all driftwood and predominantly originate from western and central Siberia. Larch and spruce from Siberia or North America represents ~26% and ~18% of all materials, respectively. Fungal colonization caused different levels of driftwood staining and/or decay. Our results demonstrate the importance of combining wood anatomical knowledge with insight on boreal forest composition for successfully tracing the origin of Arctic driftwood. To ultimately reconstruct spatiotemporal variations in ocean currents, and to better quantify postglacial uplift rates, we recommend consideration of dendrochronologically dated material from many more circumpolar sites.

Vegetation responses to rapid warming and to minor climatic fluctuations during the Late-Glacial Interstadial (GI-1) at Gerzensee (Switzerland)

High-resolution pollen analyses made on the same samples on which the ratios of oxygen isotopes were measured that provided the time scale and a temperature proxy after correlation to NorthGRIP. (1) A primary succession: The vegetation responded to the rapid rise of temperatures around 14,685 yr BP, with a primary succession on a decadal to centennial time scale. The succession between ca 15,600 and 13,000 yr BP included: (1.1.) The replacement of shrub-tundra by woodland of Juniperus and tree birch (around 14,665 yr BP) (1.2.) The response of Juniperus pollen to the shift in oxygen isotopes in less than 20 yr, (1.3.) A sequence of population increases of Hippophaë rhamnoides (ca 14,600 yr BP), Salix spp. (ca 14,600 yr BP), Betula trees (ca.14,480 yr BP), Populus cf. tremula (ca. 14,300 yr BP), and Pinus cf. sylvestris (ca. 13,830 yr BP). (2) Biological processes: Plants responded to the rapid increase of summer temperatures on all organisational levels: (2.1) Individuals may have produced more pollen (e.g. Juniperus); (2.2) Populations increased or decreased (e.g. Juniperus, Betula, later Pinus), and (2.3) Populations changed their biogeographical range and may show migrational lags. (2.4) Plant communities changed in their composition because the species pools changed through immigration and (local) extinction. Some plant communities may have been without modern analogue.These mechanisms require increasing amounts of time. (2.5) Processes on the level of ecosystems, with species interactions, may involve various time scales. Besides competition and facilitation, nitrogen fixation is discussed. (3) The minor fluctuations of temperature during the Late-Glacial Interstadial, which are recorded in δ18O, resulted in only very minor changes in pollen during the Aegelsee Oscillation (Older Dryas biozone, GI-1d) and the Gerzensee Oscillation (GI-1b). (4) Biodiversity: The afforestation at the onset of Bølling coincided with a gradual increase of taxonomic diversity up to the time of the major Pinus expansion.

Pollen and macroremains from sediment core Aschenhütte

The Upper Pleistocene sediments of the Aschenhütte sink-hole (west of Herzberg am Harz, Lower Saxony) enable one to make interesting correlations between palynological and geological results. The sequence is composed of limnic-telmatic deposits (Eemain to Lower Weichselian) and loess with paleosoils (Weichselian). Sedimentation started during the hornbeam-dominated phase of the Eemian interglacial period and continued throughout the Eemian, the Weichselian Brörup interstadial (sensu Andersen) and parts of the preceding and the following stadial phases, the Herning and the Rederstall stadials. As opposed to most of the known Eemian sites spruce was a major tree species during the hornbeam-dominated phase of the Eemian. The vegetational development during the interstadial phase does not show a period of climatic deterioration as is the case for the Brörup interstadial when considering regions with a more demanding vegetation or regions close to the natural boundaries of the tree species concerned. Pollen or seeds of Bruckenthalia and Picea omoricoides have not been found in the Aschenhütte cores. The limnic-telmatic sediments interlock with loess-paleosoils (Eemian soil and Lower Weichselian bleaching soils) at the lake shore. They are overlaid by loess paleosoils of the Stillfried-B interstadial (Hattorf soil and Lohne soil). Lake level fluctuations were determined by means of the facies distribution and isochrones as defined by pollen analysis. A relatively high stand of the lake level existed after the end of the Eemian interglacial and during the Brörup interstadial periods. In the course of the Herning stadial period the water level dropped, whereas during the Rederstall stadial phase the lake basin was covered by sediments and therefore dried up.

Requerimiento hídrico en álamos de 6 años : Rivadavia, Mendoza (Argentina)

Durante tres años consecutivos se desarrolló el ensayo de riego en álamos de 6 años (Populus euramericana I-214), en el Departamento de Rivadavia, Mendoza, Argentina. El suelo es de textura franco-arenosa. El ensayo se estableció en cuatro bloques completos aleatorizados. El área unitaria fue de 192 m2, con un total de 20 árboles por parcela. Los Intervalos de Riego (IR) fueron 7,14 y 21 días. El número de riegos anuales fue de 21 y la evapotranspiración diaria del cultivo fue de 14.6 mm/día. Los resultados muestran que para el IR = 7 días la Evapotranspiración real (Etc) fue de 2.097 mm; para IR = 14 días fue de 1 467 mm y para IR = 21 días fue de 1 051 mm. El Coeficiente Kc de cultivo se obtuvo al relacionar la Etc con la Evapotranspiración potencial obtenida por la fórmula de Blaney y Criddle y del tanque de evaporación estándar tipo A. Los esultados fueron respectivamente: Kc = 2.95 y 2.06 para IR = 7 días; Kc = 2.07 y 1.45 para IR = 14 días y Kc = 1.47 y 1.05 para IR = 21 días. Del análisis estadístico del volumen de madera producido se concluye que el IR de 7 días fue el mejor para álamos de seis años.

Comportamiento de clones de álamos en Barreal : San Juan, Argentina

Con el objetivo de estudiar el comportamiento de diferentes clones de álamos en el valle cordillerano de Barreal, ubicado en la provincia de San Juan, Argentina, en 1995 se instaló un ensayo con los siguientes clones: 7 Populus x canadensis: Cima, Fogolino, Giorgione, Schiavone, Conti 12, I-214, Veronese y 7 Populus x deltoides: Harvard, Fierolo, I-72, 67/67, 71/67, Catfish 2 y Catfish 5. El sitio se encuentra a 31°36'55'' S, 69°27'30'' W y una altura de 1.628 msnm. El suelo es aluvial, de textura franca con cantos rodados de tamaño medio a partir de los 70 cm de la superficie. El marco de plantación fue de 5 x 2,5 m y el riego superficial por surcos. Se tomaron periódicamente datos dasométricos del diámetro altura de pecho (DAP) de todos los individuos, y altura total de árboles de diámetro promedio de cada clon. Además se observó cada una de las plantas a fin de determinar la presencia o ausencia de cancrosis del álamo y taladrillo de los forestales. Los resultados a la fecha muestran que los clones con mayor producción de madera, expresada en m3/ha son: Schiavone, I-214, Veronese, Conti 12 y Giorgione.