对百色石器层位和时代的新认识

1988年冬在百色盆地进行的发掘中,从砖红壤化阶地出土了69件石制品。这是百色地区自1973年发现旧石器以来首次获得数量较大和层位记录完备的材料。有关构造、地貌和古环境等方面的分析表明:百色地区含旧石器的砖红壤化阶地的堆积时代不会晚于北京人时代早期。     

Geochronology of cave deposits at Liang Bua and of adjacent river terraces in the Wae Racang valley, western Flores, Indonesia: a synthesis of age estimates for the type locality of Homo floresiensis

A robust timeframe for the extant cave deposits at Liang Bua, and for the river terraces in the adjoining Wae Racang valley, is essential to constrain the period of existence and time of extinction of Homo floresiensis and other biota that have been excavated at this hominin type locality. Reliable age control is also required for the variety of artifacts excavated from these deposits, and to assist in environmental reconstructions for this river valley and for the region more broadly. In this paper, we summarize the available geochronological information for Liang Bua and its immediate environs, obtained using seven numerical-age methods: radiocarbon, thermoluminescence, optically- and infrared-stimulated luminescence (collectively known as optical dating), uranium-series, electron spin resonance, and coupled electron spin resonance/uranium-series. We synthesize the large number of numerical age determinations reported previously and present additional age estimates germane to questions of hominin evolution and extinction.     

大田增强UV-B辐射对元阳梯田地方水稻茎秆性状和倒伏指数的影响

大田原位种植元阳梯田2个地方水稻品种——白脚老粳和月亮谷,研究2年不同强度(0、2.5、5.0和7.5 kJ·m^-2)UV-B辐射对水稻穗下第1至第4节的茎秆性状(节间长、茎秆粗和茎壁厚)和倒伏指数的影响.结果表明: 增强UV-B辐射对水稻茎秆的节间长和茎秆粗没有显著影响,但导致茎壁厚度显著减小,其中,7.5 kJ·m^-2 UV-B辐射对水稻穗下第4节茎秆茎壁厚度的影响较大,降幅为11.6%～19.6%;增强UV-B辐射导致水稻茎秆的倒伏指数增加,增大水稻倒伏的风险,水稻穗下第4节茎秆倒伏指数最大,并大于倒伏临界值(200);水稻穗下第4节、第3节和第2节茎秆的倒伏指数与茎壁厚度呈显著负相关.表明增强UV-B辐射显著减小元阳梯田水稻茎秆的茎壁厚是增加其倒伏风险的主要原因.
     

Découverte d’une industrie du Paléolithique inférieur en bordure de la commune de Nice,au Vallon obscur à Saint-Isidore

An archaic lithic assemblage has just been brought to light in border of the municipality of Nice (Alpes-Maritimes, France), in secondary position in a geologic context of middle fluviatile terrace in left bank of the Var. Lithic artefacts collected gather some shaping products (worked or broken pebbles) and débitage products (cores, flakes, angular fragments), obtained on pebbles mainly in marly limestone, stemming from the local plio-Pleistocene conglomerate and the alluviums of the Var. This lithic production shows essentially the beginnings of chaînes opératoires, with the first phases of pebbles cortex removing. Flakes are very mainly cortical or semi-cortical, and cores reveal a weak technical investment, with a reduced enough number of removal negatives. The débitage of orthogonal type is the most frequent, and the bipolar technique on anvil is attested. Some rare flakes are retouched by notches or by abrupt continuous retouches. The sector where was brought to light this lithic industry, in sediments reshaped below a level of fluviatile terrace of the Var in 70 m of height, made us suggest a very ancient age for these vestiges, being able to go back up at the beginning of Middle Pleistocene, even of Lower Pleistocene, what is in agreement with the technical characteristics noticed on this lithic assemblage.     

Vergleichende vegetationskundliche Untersuchungen an Schneeböden

Die begriffliche Abgrenzung von Schneeböden und ihrer Vegetation wird unterschiedlich gehandhabt und bereitet für die Einschätzung des Umfanges der Klasse Salicetea herbaceae Probleme. — Klimaunterschiede zwischen der alpinen Stufe mitteleuropäischer Gebirge und oroarktisch-arktischer Regionen und die daraus resultierenden edaphischen Unterschiede werden als eine Ursache verschiedener Gliederungskonzepte der Vegetationstypen hervorgehoben. Die teilweise unzulängliche Berücksichtigung der Kryptogamen erschwert zusätzlich die Vergleichbarkeit der regional gewonnenen Befunde Syndynamische Beziehungen zu Kontaktgesellschaften werden skizziert, und für die Schneeboden-Vegetation bezeichnende Geoelemente werden vorgestellt und in ein Gliederungskonzept (Tabelle 2 und Appendix) eingearbeitet. Für die Abgrenzung der Phytozönosen im Bereich der Arktis sind zusätzliche Untersuchungen notwendig Die ökologisdien Verhältnisse werden beispielhaft an einem Transekt aus den Zentralalpen (Ötztal, Österreich) skizziert (Abb. 2 bis 4). Die Bedeutung von Kryptogamensynusien für die Charakterisierung kleinräumig wechselnder edaphischer Unterschiede wird betont und die ökologische Amplitude einiger ”Schlüsselarten” umrissen     

黄土丘陵区坡改梯生态经济耦合效应

坡改梯是黄土丘陵区提高农作物单产和控制水土流失的有效措施。基于坡改梯内生和外延效应的学术思路,构建了能定量刻画坡改梯生态经济耦合状况的数学模型;以位于黄土丘陵区腹地的延安燕沟流域为例,利用土地利用和数字地形等空间数据、作物产量和土壤侵蚀模拟数据以及监测和调查数据,定量评价分析了燕沟流域坡改梯的生态经济耦合效应。结果表明:地形坡度越大,坡改梯的生态经济耦合效应越显著;地形坡度5°和15°是两个重要阈值,5°以下不必进行坡改梯,5°—15°之间应作为坡改梯的重点对象,15°以上宜退耕还林还草。坡改梯使燕沟流域农耕地的生态经济耦合程度得到了显著提高,坡改梯前生态经济耦合指数为1.805t/100元,坡改梯后下降为0.853t/100元,下降幅度达52.73%。随着坡改梯和植被覆盖率的提高,流域的洪水径流量和输沙模数均大幅度下降。     

Vegetation patterns,plant distribution and life forms across the alpine zone in southern Tierra del Fuego,Argentina

The alpine zone is examined at meso‐ and microscales in southern Tierra del Fuego (54°49′S), where the full zone is expressed. Mesoscale patterns were studied on opposing aspects, and microscale patterns were studied on a series of solifluction terraces, in a hanging valley overlooking the Beagle Channel. Plant cover and life form data were collected within 50‐m altitudinal bands on north and south aspects and comprehensive plant lists were compiled for each band. Topography and associated surface cover were recorded on the terraces. Six alpine plant communities, in lower and upper floristic zones, were differentiated with multivariate analyses and significantly related to five ecological factors. Equivalent communities were separated by approximately 185 m altitude on opposing aspects, which related to a soil temperature difference of approximately 3.0°C. The richness (and range) of 80 local vascular taxa (18.6% of the regional flora), decreased with increasing altitude (6.6 per 100 m); however, richness differed significantly with aspect (north: 5.6, south: 7.5). Upper altitudinal limits (approximately 1250 m a.s.l.), were associated with a midsummer isotherm of approximately 1.7°C. Chamaephytes and hemicryptophytes dominated throughout but the tall tussock form was conspicuously absent. Reasons for this are discussed in the context of the Nothofagus treeline, which conformed to a midsummer isotherm of only approximately 6.0°C. Such patterns are at variance with those found in the oceanic subantarctic islands, other oceanic perhumid temperate mountain regions and tropical high mountains. However, the microscale pattern of fines, pebbles, stones and rock across the active solifluction terraces, with dense vegetation on their steep risers, had a clear affinity with that of other subantarctic regions. Inferences that alpine systems of the Southern Hemisphere are necessarily equivalent to those at similar northern latitudes are cautioned against. Likewise, such comparisons within the Southern Hemisphere may also be invalid.     

Radial growth of Pinus sylvestris growing on alluvial terraces is sensitive to water-level fluctuations

Along the Alpine river Lech (Tyrol, Austria), poorly grown Scots pine (Pinus sylvestris) stands dominate on dry alluvial terraces, which are made up of coarse calcareous gravel. Here we evaluated the impact of environmental factors, such as precipitation, temperature and water table, on annual variability of radial growth. Tree-ring chronologies from six stands comprising different age classes were developed by extracting two core samples from more than 15 trees per plot. Pearson correlations were applied to determine the influence of environmental factors. Close inverse correlations (r2 > 0.35) between maximum water table during the growing period and annual increments of adult stands indicated that water surplus in the rooting zone was the primary growth-limiting factor. Drought stress reduced growth only in some extremely dry years. Results provide evidence that dominance of P. sylvestris on gravelly alluvial terraces is caused not only by tolerance of soil dryness and nutrient deficiency, as previously assumed, but also by a dynamic multilayered root system which allows adaptation to highly variable soil-moisture conditions.     

Les nappes alluviales de la Basse Somme revisitées

The new approach of the fluviatile sequence preserved downstream of Abbeville from Port-le-Grand to Saint-Valery, brings together two sets of complementary data in a same canvas. The first set combines the field records of V. Commont and A. Briquet slightly above the basal cravels. The second set encompasses the data gained for the high and very high terraces mapped in the eighties. They point to a succession of ten main terraces and two second order ones, occurring in continuity with the Abbeville terrace system. The upper terrace being related to Jaramillo, we are dealing with one million year strong regional record with a high-resolution palaeoenvironmental signature fitting in with the ODP 677 marine isotopic record and with the Chinese loess record. In this way, the laminar tool-kit of Croix-l’Abbé could be positioned in the middle part of MIS 8, around 250 ka.