CCL

Összesen 2 találat.
#/oldal:
Részletezés:
Rendezés:

1.

001-es BibID:BIBFORM079873
Első szerző:Hubay Katalin (biológus, környezetkutató)
Cím:Age-depth relationship and accumulation rates in four sediment sequences from the Retezat Mts, South Carpathians (Romania) / Hubay Katalin, Molnár Mihály, Orbán Ildikó, Braun Mihály, Bíró Tamás, Magyari Enikő
Dátum:2018
ISSN:1040-6182
Megjegyzések:This study summarizes the results of radiocarbon dating and age-depth modelling in four mountain lakes (Brazi, Gales, Bucura and Lia) in the Retezat Mountains. Altogether 69 AMS 14C measurements were performed on these deposits, mostly on terrestrial plant macrofossils. In several cases, plant macrofossils, aquatic animal remains (Cladoceran eggs) and bulk sediment were measured from the same depth allowing for the comparison of various sediment components in terms of their dating potential. Age-depth models were developed using both Bayesian modelling with the BACON and smooth spline curve fitting with the CLAM software. In this study Bayesian models are applied to identify outlier 14C dates, while smooth spline models are used to model sediment accumulation age-depth relations, as these are more likely to follow natural deposition time changes of lake sediments. Changes in sediment deposition times (DT) in relation to catchment size and climate are also studied. DT varied considerably in the late glacial (LG) part of the records. The sediment sequence characterised by high deposition rates during the late glacial (DT maximum around 100?110 years cm?1) was defined by small catchment size (Lake Brazi, 6 ha; surface area: 0.5 ha). In contrast, much slower LG sediment deposition in the southern slope lake characterised by large catchment area (Lake Lia, 171 ha, 20 years cm?1), principally reflecting strong erosion in these catchment areas at times when vegetation cover was scarce. Holocene was characterised again by variable DT values, but only Lake Gales showed extreme values: 62?110 years between 10,900 and 6050 cal yr BP, followed by much slower sediment deposition in the last 6000 years (av. 29 years cm?1). Generally, sediment deposition times were largely dependent on the stability and vegetation cover of the slope in the case of high altitude deep lakes, while lower altitude, shallow lakes showed slower sediment deposition time in the early and mid-Holocene, when summer insolation was higher than today. This reflects that in these shallow lakes in-lake organic production probably increased with summer insolation, which was a significant driver in the rate of deposition.
Tárgyszavak:Természettudományok Környezettudományok idegen nyelvű folyóiratközlemény külföldi lapban
AMS 14C dating
Glacial lake sediments
Late glacial
Holocene
Carpathians
Megjelenés:Quaternary International. - 477 (2018), p. 7-18. -
További szerzők:Molnár Mihály Orbán Ildikó Braun Mihály (1966-) (vegyész, analitikus) Bíró Tamás Magyari Enikő (1973-) (biológus)
Internet cím:Szerző által megadott URL
DOI
Intézményi repozitóriumban (DEA) tárolt változat
Borító:

2.

001-es BibID:BIBFORM079875
Első szerző:Orbán Ildikó
Cím:Treeline and timberline dynamics on the northern and southern slopes of the Retezat Mountains (Romania) during the late glacial and the Holocene / Ildikó Orbán, Hilary H. Birks, Ildikó Vincze, Walter Finsinger, Ilona Pál, Elena Marinova, Gusztáv Jakab, Mihály Braun, Katalin Hubay, Tamás Bíró, Enikő K. Magyari
Dátum:2018
ISSN:1040-6182
Megjegyzések:To investigate treeline and timberline dynamics in the Retezat Mountains (Romanian Carpathians), late glacial and Holocene sediment sequences from four lakes were studied. The south and north slopes of the mountain range were compared using two lakes from the north flank (Lake Brazi, 1740 m a.s.l. and Lake Gales, 1990 m a.s.l) and two from the south flank (Lake Lia, 1910 m a.s.l. and Lake Bucura, 2040 m a.s.l.). Macrofossil and stomata analyses were performed to assess changes in the local vegetation, supplemented by pollen, charcoal and loss-on-ignition analyses. Our results show that treeline reached Lake Brazi on the northern side during the late glacial (ca. 14,000 cal yr BP) and then Lake Gales between 11,000 and 10,800 cal yr BP. During the early Holocene the upper limit of closed forest, the timberline, reached and passed Lake Brazi and has stayed above it since, but it has never reached Lake Gales at 1990 m a.s.l. The expansion of Larix decidua in the late glacialand early Holocene around Lake Brazi is unique. Stomata and macrofossils of Abies alba are also more abundant in the northern records. On the southern flank, treeline reached Lake Lia at around 12,000 cal yr BP, and was either very close to or at the elevation of Lake Bucura between ca. 8600 and 3000 cal yr BP. Timberline reached Lake Lia at ca. 8000 cal yr BP, some 3000 years after Lake Brazi, only 170 m lower on the north slope. Local fire events delayed the advance of timberline around Lake Lia in the early Holocene in a dry continental climate. The surrounding forest was dominated by Picea abies with individuals of Pinus cembra and stands of P. mugo until about 3000 cal yr BP when timberline retreated below the lake. Maximum elevation of timberline was attained between ca. 8000 and 3000 cal yr BP, after which it descended in response to climate cooling. Regional climate change appears to be the main driver of treeline dynamics, but it was modified by local climatic differences due to slope aspect. The first signs of human disturbance appeared ca. 4200 cal yr BP, when naturally open areas were used as alpine pastures. Human impact in the treeline ecotone, mainly burning and grazing, was intensified after ca. 2600 cal yr BP, contributing to the widening of the ecotone and the lowering of the timberline.
Tárgyszavak:Természettudományok Környezettudományok idegen nyelvű folyóiratközlemény külföldi lapban
Treeline
Timberline
Macrofossil analysis
Stomata analysis
Retezat mountains
Carpathians
Megjelenés:Quaternary International. - 477 (2018), p. 59-78. -
További szerzők:Birks, Hilary H. Vincze Ildikó Finsinger, Walter Pál Ilona Marinova, Elena Jakab Gusztáv Braun Mihály (1966-) (vegyész, analitikus) Hubay Katalin (1985-) (biológus, környezetkutató) Bíró Tamás Magyari Enikő (1973-) (biológus)
Internet cím:Szerző által megadott URL
DOI
Intézményi repozitóriumban (DEA) tárolt változat
Borító:
Rekordok letöltése1