A fossil Vallisneria plant (Hydrocharitaceae) from the Early Miocene freshwater deposits of the Most Basin (North Bohemia)

A new fossil species of Vallisneria (V. janecekii Bogner & Kva?ek, sp. n., Hydrocharitaceae) is reported from Early Miocene freshwater lake deposits of the North Bohemian brown coal basin (Czech Republic). It is based on a single fragmentary sterile plant bearing two clusters of ribbon-shaped widely serrulate leaves on a short rhizome. It is a potential producer of seeds described from equivalent and slightly older deposits in Saxony (Germany) as Vallisneria ovalis Mai.     

中国第四纪晚期孢粉记录整理

孢粉数据库是重建过去植被格局以及研究古气候变化和大气圈-生物圈-人类活动相互关系的基础,而孢粉取样信息的记录和整理是建立孢粉数据库的重要前提。该文在收集我国1960–2008年发表的孢粉研究文献的基础上,整理分析了第四纪晚期,尤其是2万年以来(全新世为主)全国孢粉采样点的信息,包括采样地点名称、详细采样位置、省份、采样点经纬度和海拔高度、样品类型、取样深度、孢粉样品数量、14C测年数量及年代记录、覆盖的时间段和参考文献。总结发现,我国目前共有2324个表土/湖泊表层花粉采样点和987个第四纪晚期的地层沉积剖面和钻孔,其中高质量的地层孢粉采样点714个。虽然我国以及部分国际上从事第四纪研究的科学家尽了最大努力开展中国疆域的孢粉学研究,但由于人力、物力以及地形条件的限制,在我国仍然存在部分孢粉采样的\"地理空隙\",比如北方和西北荒漠地区、青藏高原无人区、中南部山区和东部人类活动频繁区域。然而,该数据信息库的不断完善,将为中国第四纪孢粉数据库的建立奠定良好基础。     

The Holocene at Lac de Creno, Corsica, France: a key site for the whole island

Two Holocene lake sequences from Lac de Creno, Corsica were analysed on the basis of 119 pollen spectra and with the support of 13 ¹⁴C-calibrated dates. The lower part of one of these sequences, corresponding to the late- glacial period, has been published previously. The first third of the Post-glacial is characterized by very particular forest dynamics, namely the absence of a role for deciduous Quercus and Corylus , the presence of mesophilous vegetation types dominated by Taxus , and the major forest role of Erica arborea at lower and mean altitude. At about 7440 cal BP, the occurrence of a major anthropogenic action brought about significant changes in the vegetation, notably an increase of deciduous Quercus and the expansion of Quercus ilex . Later, three major human-induced events are identified: the first, at about 2290 cal BP, is the cause of a short local expansion of Abies ; the second, at about 1150 cal BP, is the degradation of deciduous forests to the benefit of Fagus ; the third, at about 310 cal BP, corresponds to the disappearance of Fagus and its replacement by Pinus . Pollen data indicate that Q. ilex , Abies and Fagus are not indigenous in Corsica but spread there during the Postglacial ; this probably took place at about 6980 cal BP for Q. ilex .     

Contributo alle Silicoflagellate fossili del Miocene superiore dell'Italia centrale

Abstract

A contribution to the fossil Silicoflagellates of the late Miocene in Central Italy. - A microscopic analysis of fourteen diatomite samples from a Messinian (late Miocene) stratigraphic series, in central-eastern Italy, has been carried out in order to verify the presence of Silicoflagellates. The skeletons of eight taxa were found in good condition and identified. The most abundant and continuous in the stratigraphic series examined are Dictyocha fibula and Distephanus speculum, also known in the present-day seas; Cannopilus sphaericus, a very rare and interesting species extinct in the Miocene, is limited to only two samples. On the basis of the Silicoflagellates found, it is possible to suggest that they lived in an open sea with 30–40‰ salinity and a temperature of 10–20°C. A very similar situation is present nowadays in the middle-western Adriatic Sea.     

Genetic consequences of glacial survival and postglacial colonization in Norway spruce: combined analysis of mitochondrial DNA and fossil pollen

Norway spruce (Picea abies [L.] Karst.) is a broadly distributed European conifer tree whose history has been intensively studied by means of fossil records to infer the location of full‐glacial refugia and the main routes of postglacial colonization. Here we use recently compiled fossil pollen data as a template to examine how past demographic events have influenced the species’ modern genetic diversity. Variation was assessed in the mitochondrial nad1 gene containing two minisatellite regions. Among the 369 populations (4876 trees) assayed, 28 mitochondrial variants were identified. The patterns of population subdivision superimposed on interpolated fossil pollen distributions indicate that survival in separate refugia and postglacial colonization has led to significant structuring of genetic variation in the southern range of the species. The populations in the northern range, on the other hand, showed a shallow genetic structure consistent with the fossil pollen data, suggesting that the vast northern range was colonized from a single refugium. Although the genetic diversity decreased away from the putative refugia, there were large differences between different colonization routes. In the Alps, the diversity decreased over short distances, probably as a result of population bottlenecks caused by the presence of competing tree species. In northern Europe, the diversity was maintained across large areas, corroborating fossil pollen data in suggesting that colonization took place at high population densities. The genetic diversity increased north of the Carpathians, probably as a result of admixture of expanding populations from two separate refugia.     

Integrated palaeoecological evidence for biodiversity at the floodplain-forest margin

This paper presents the results of a combined palynological and palaeoentomological investigation into the changing diversity of Holocene floodplain forest biota at Bole Ings in the lower reaches of the River Trent. The aim in combining the two techniques represents an attempt to overcome some of the inherent differences of scale and resolution which characterize different types of fossil species data. The two lines of ecofactual evidence, pollen and beetle remains indicate changes in the biodiversity of the floodplain, both in terms of the diversity and abundance of individual species, habitats and ecosystem structure. The results of the study demonstrate the potential of this approach in tracing the decline in plant and entomofaunal diversity at the floodplain forest margin. Although there are recognized limitations imposed by taphonomic uncertainties, taxonomic resolution and restricted ecological data, the combined results provide added details of variations in both species composition and structural diversity within the landscape. The results emphasize the need for multidisciplinary research design in palaeoecological investigations of biodiversity.     

Vegetation dynamics in central Africa since 18,000 yr BP: pollen records from the interlacustrine highlands of Burundi, Rwanda and western Uganda

A standardized analysis of palaeoecological data, in the form of six pollen sequences and forty- four radiocarbon ages, has permitted a region-wide reconstruction of Late Quaternary vegetation dynamics for the interlacustrine highlands of central Africa.
A landscape widely dominated by ericaceous scrub and grasslands, but also supporting sparse patches of open-canopied montane forest, possibly in those areas with a topography most favourable to the growth of trees, is indicated for the last glacial maximum of 18,000 yr bp . Major expansions in the extent of upper altitudinal forms of montane forest occurred from around 12,500 yr bp , while lower moist montane forest—the expected climax for much of the region today—did not become prominent until 11,000 yr bp to 10,000 yr bp . From the palaeoecological evidence at least, it appears that the major east Central forest refuge, proposed by some workers on the basis of current species' distribution patterns, did not extend to the eastern flanks of the Albertine Rift.
A late glacial–early Holocene transition is only fully chronicled in two of the sites. However, it appears that the expansion of lower montane forest had a time-transgressive pattern across the region, and was not simply from low to high altitude. The composition of forests during the early Holocene appears to have been different to that in the later stages of the present interglacial, as taxa presently associated with wetter and/or more open forest types were much more common. Pollen data also indicate that higher altitude parts of the interlacustrine highlands were more attractive to the earliest (possibly Bantu-speaking) farmers and metal-workers. There is evidence of wide-spread forest clearance around the beginning of the present millennium, possibly as a result of substantial changes in socio-economic conditions, and patterns of settlement, associated with the onset of the Late Iron Age.     

Coarse Woody Debris Quantity and Distribution in Central European Streams

Summarized here are ten investigations concerning the volume of coarse woody debris (CWD) in Central European streams. Altogether, 69 stream sections were examined ranging from Northern German lowland streams to brooks in alpine regions. Most of the study streams are according to Central European standards quasi‐natural and are bordered by deciduous forest. The geometric mean of CWD volume related to stream length is 1.44 m³ /100 meter reach. Related to stream bottom area, the geometric mean of CWD volume is 0.202 m³ /100 m² . The mean number of logs (≥10 cm diameter) is 12.5 logs/100 meter reach, and 3.01/100 m² bottom area (geometric means). Regarding only quasi‐natural stream sections (riparian forest currently unmanaged and no removal of CWD for at least 10 years), the geometric mean of CWD standing stock is 0.45 m³ /100 m² for lowland streams, 0.38 m³/100 m² for streams in lower mountainous areas and 0.02 m³ /100 m² for alpine floodplains. From the distribution of size classes and comparison with other studies it is likely, that the current CWD standing stock is considerably less than the potential amount of CWD. For centuries all of the streams have been influenced by man. Historic alterations of the stream, its floodplain and the riparian vegetation may still affect CWD supply and standing stock. We conclude that virtually all streams in Central Europe are highly altered with respect to the amount of CWD, and that the importance of CWD is under‐represented in recent assessment principles for streams in Germany.     

Habitatansprüche des Kleinspechts(Dendrocopos minor) in W?ldern der Nordost-Schweiz

Zusammenfassung Viele Aspekte der Autökologie des Kleinspechts(Dendrocopos minor) sind schlecht untersucht. Dies gilt in besonderem Maß für seine Habitatansprüche in den Wäldern Mitteleuropas. Ein Ziel der vorliegenden Arbeit bestand deshalb darin, in ausgewählten Wäldern der Nordost-Schweiz die für den Kleinspecht relevanten Habitatstrukturen zu identifizieren. Ausserdem wurde die Eignung von Tonband-Klangattrappen für die Kartierung untersucht. Für die Habitatanalyse wurden in 21 der 22 Wälder mit Kleinspechten und in einer Kontrollgruppe von 21 Wäldern ohne Kleinspechtvorkommen verschiedene Habitatvariablen erhoben. Mit einer logistischen Regression wurden die Variablen ermittelt, die am meisten zur Unterscheidung der beiden Gruppen beitragen. Es resultierten vier Variablen als Prädiktoren für das Vorkommen von Kleinspechten: 1) Weichhölzer begünstigen die Anwesenheit des Kleinspechts; 2) besiedelte Wälder weisen eine geringere Entfernung zu einem Gewässer auf; 3) Kleinspechte kommen hauptsächlich in tieferen Lagen vor; 4) Die untersuchten Kleinspecht-Wälder weisen im Vergleich mit den Kontrollwäldern weniger stehende tote Bäume mit BHD 15 cm auf. Die Erhebung von Kleinspecht-Beständen mit einer Klangattrappe kann während eines kurzen Zeitraums im März/April effizient und zuverlässig durchgeführt werden.

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Habitat requirements of the Lesser Spotted Woodpecker(Dendrocopos minor) in forests of northeastern Switzerland

Summary Despite the widespread distribution of the Lesser Spotted Woodpecker, many aspects of the species' biology are poorly known, particularly regarding its habitat requirements in central European forests. Recent studies suggest population declines in many areas of its range, making the need for appropriate management guidelines urgent. In 1997, we examined which habitat factors affect the presence of the Lesser Spotted Woodpecker in decidous lowland, non-riverine forests of northeastern Switzerland and evaluated the usefulness of playback tapes for censusing the species. Selected on the basis of prior knowledge of the species' distribution, 27 forests were searched for Lesser Spotted Woodpeckers using playbacks from March to early May. The species was still present in 17 of these formerly occupied forests, while 5 new registrations were made in previously unoccupied forests. Ninety percent of the registrations occurred between 16 March and 24 April, and the woodpeckers responded to the playbacks most often with call series. The habitat structure of forests with Lesser Spotted Woodpeckers was compared with that of forests where the species had been absent both during previous censuses and in 1997, and which had a similar tree species composition, forest structure and elevation to the occupied forests. Logistic regression analysis identified four habitat variables as significant predictors of the species' presence/absence. Accordingly, forests were most likely occupied by the Lesser Spotted Woodpecker if more softwoods, but fewer snags (with a DBH 15 cm) per area were available, if the distance to lakes and rivers was small, and the elevation was low. Therefore, the distribution of the Lesser Spotted Woodpecker seems to be affected by variables reflecting both forest structure and relative position of the forests within the landscape. We conclude that the Lesser Spotted Woodpecker will benefit from protection and promotion of softwood in all forest types, resulting in increased habitat connectivity. Moreover, censuses using playbacks can be efficiently conducted during a short period in March/April.

     

四川螺髻山表土和化石孢粉揭示的环境生态意义

通过四川螺髻山（1984、2017年）表土和化石孢粉与植被的关系分析发现：孢粉组合中木本植物含量（91.0%）占绝对优势,松属、冷杉属、青冈属、常绿栎类、落叶栎类、桤木属、杜鹃花科、禾本科和蒿属为主要花粉类型;人工次生林花粉组合能很好地反映母体植被的群落特征,并可指示优势种的存在和人类活动痕迹;针阔混交林花粉组合能较好地反映群落整体特征,花粉类型能与母体植被中优势种较好地对应;常绿阔叶林、针叶林和灌丛草甸的花粉组合难以反映母体植被的群落特征。DCA表明,花粉谱的百分含量,能较好地区分人工扰动植被和天然植被,但人工次生林、常绿阔叶林和针阔混交林之间以及针叶林和灌丛草甸之间未能区分。30年前后表土孢粉组合变化明显,1984年样品以松属、青冈属和桤木属等花粉为主,而2017年采样分析中松属、桤木属花粉占绝对优势。随着人类活动的加强,部分地区松树和桤木大面积飞播或种植,表土孢粉组合对当地植被指示意义与扰动强度呈负相关关系。现生植被与表土孢粉组合的差异能为恢复古植被和古环境提供参考,但原生植被已经被破坏地区的孢粉图谱,就很难作为重建历史时期植被的根据。本研究可以为亚热带山地利用孢粉学恢复第四纪时期植被与气候,探讨人类活动与环境的关系提供理论依据和实践参考。