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1.
Richard Tipping Patrick Ashmore Althea L. Davies B. Andrew Haggart Andrew Moir Anthony Newton Robert Sands Theo Skinner Eileen Tisdall 《Vegetation History and Archaeobotany》2008,17(3):251-267
Pollen, microscopic charcoal, palaeohydrological and dendrochronological analyses are applied to a radiocarbon and tephrochronologically
dated mid Holocene (ca. 8500–3000 cal b.p.) peat sequence with abundant fossil Pinus (pine) wood. The Pinus populations on peat fluctuated considerably over the period in question. Colonisation by Pinus from ca. 7900–7600 cal b.p. appears to have had no specific environmental trigger; it was probably determined by the rate of migration from particular
populations. The second phase, at ca. 5000–4400 cal b.p., was facilitated by anthropogenic interference that reduced competition from other trees. The pollen record shows two Pinus declines. The first at ca. 6200–5500 cal b.p. was caused by a series of rapid and frequent climatic shifts. The second, the so-called pine decline, was very gradual (ca.
4200–3300 cal b.p.) at Loch Farlary and may not have been related to climate change as is often supposed. Low intensity but sustained grazing
pressures were more important. Throughout the mid Holocene, the frequency and intensity of burning in these open Pinus–Calluna woods were probably highly sensitive to hydrological (climatic) change. Axe marks on several trees are related to the mid
to late Bronze Age, i.e., long after the trees had died. 相似文献
2.
Samuli Helama Matti Vartiainen Taneli Kolström Heli Peltola Jouko Meriläinen 《Vegetation History and Archaeobotany》2008,17(6):675-686
A collection of subfossil wood of Pinus sylvestris (Scots pine) was exposed to X-ray densitometry. The collection of 64 samples from the southern boreal forest zone was dendrochronologically
cross-dated to a.d. 673-1788. Growth characteristics were determined by performing density profiles including the following parameters: minimum
density, earlywood and latewood boundary density, maximum density, earlywood width, earlywood density, latewood width, latewood
density, annual ring width and annual ring density. Seven out of the nine parameters were found to contain non-climatic growth
trends and six were found to be heteroscedastic in their variance. Tree-specific records were indexed, to remove the non-climatic
growth trends and stabilize the variance, and combined into nine parameter-specific tree-ring chronologies. Growth characteristics
of the pines changed in parallel with the generally agreed climatic cooling from the Medieval Warm Period to the Little Ice
Age: pine tree-rings showed decreasing maximum densities from the period a.d. 975-1150 to a.d. 1450–1625. A concomitant change in the intra-annual growth characteristics was detected between these periods. The findings
indicate that not only the trees growing near the species’ distributional limits are sensitive to large-scale climatic variations
but also the trees growing in habitats remote from the timberline have noticeably responded to past climate changes. 相似文献
3.
Willy Tinner Feng Sheng Hu Ruth Beer Petra Kaltenrieder Brigitte Scheurer Urs Krähenbühl 《Vegetation History and Archaeobotany》2006,15(4):279-293
Pollen, plant macrofossil and charcoal analyses of sediments from two Alaskan lakes provide new data for inferring Lateglacial and Holocene environmental change. The records span the past 14,700 years at Lost Lake, 240 m a.s.l., central Alaska, north of the Alaska Range and 9600 years at Grizzly Lake, 720 m a.s.l., Copper River Plateau, south of the Alaska Range. Salix shrubs expanded in the herb tundra about 14,400 cal b.p., and Betula shrub tundra became established at ca. 13,200 cal b.p. Diminished Betula shrub cover in association with the increased abundance of herbaceous taxa occurred at 12,500–11,600 cal b.p., although the timing of these changes is not well constrained. Populus expanded at 11,200 cal b.p. and formed dense stands until 9600–9400 cal b.p. when Picea glauca forests or woodlands became established at both sites. The abundance of Alnus viridis increased markedly around 8500 cal b.p. at both sites, marking the development of alder shrub thickets around the lakes and on mountain slopes in these areas. Boreal forests dominated by Picea mariana became established around 7200 cal b.p. at Grizzly Lake and 5700 cal b.p. at Lost Lake. At Grizzly Lake, marked vegetational oscillations occurred within the past 8500 years; for example, A. viridis expanded at 2750 cal b.p. and 450 cal b.p. and declined at 150 cal b.p. Some of these oscillations coincide with large-scale climatic events, such as the Little Ice Age cooling (LIA), and they probably reflect vegetational sensitivity to climatic change at this high site. Microscopic charcoal at Lost Lake suggests that fire was important in the lateglacial birch tundra, probably because of severe moisture deficits of the regional climate and/or high abundance of fine fuels. On the basis of the Grizzly Lake microscopic charcoal record, regional fires were common between 8500 and 6800 cal b.p. and between 450 and 150 cal b.p. Around Grizzly Lake, the mean return intervals of local fires estimated from macroscopic charcoal were ∼386 years between 6800 and 5500 cal b.p. when Picea glauca dominated over P. mariana, ∼254 years between 5500 and 3900 cal b.p. when P. mariana was more abundant than P. glauca, and ∼200 years after 3900 cal b.p. in both P. glauca and P. mariana dominated forests. Correlation analysis of pollen and microscopic charcoal at Grizzly Lake reveals that increased fire activity led to the reductions of P. glauca, P. mariana, and tree Betula in association with the expansions of A. viridis, Epilobium, Lycopodium clavatum, and L. annotinum. 相似文献
4.
Verushka Valsecchi Willy Tinner Walter Finsinger Brigitta Ammann 《Vegetation History and Archaeobotany》2006,15(2):99-113
Lake-sediment records were used to reconstruct human impact on the landscape around Lago Lucone (45°33′N, 10°29′E, 249 m a.s.l.),
a former lake in the western amphitheatre system of the Lago di Garda. Presence of prehistoric human populations is attested
by pile-dwelling settlements from the Early-Middle Bronze Age, with one settlement at a distance of only 100 m from the coring
site. Pollen, plant-macrofossil and microscopic charcoal analyses were applied to a 250 cm sediment core with four dates providing
the time control. A mixed oak forest that was important during the Early-Middle Holocene was cleared and replaced by open
vegetation during the Bronze Age (∼2000–1100 b.c.) when open lands were estimated to have covered more than 60% of the total relevant pollen-source area. During a phase of
high human impact, independent climatic proxies suggest warm and dry climatic conditions. Later, ca. 1100 b.c., palaeobotanical evidence indicates a sharp decrease in human pressure in the Lago Lucone area. The comparison with other
sedimentary palaeocultural records shows that the period 1300–1100 b.c. was characterised by general declines of agricultural activities both south and north of the Alps. These declines have been
previously attributed to a change towards wetter and colder climatic conditions in and around the Alps. However, the decline
in human impact around Lago Lucone cannot be exclusively attributed to climatic variation. Therefore other forcing factors
independent of climatic changes, such as cultural crises or changes in spatial organisation of the habitats, cannot be ruled
out under the present state of knowledge. 相似文献
5.
A. C. D’Andrea 《Economic botany》2008,62(4):547-566
T’ef (
Eragrostis tef
) in Ancient Agricultural Systems of Highland Ethiopia. T’ef (Eragrostis tef) has been cultivated in the Horn of Africa for at least 2,000 years. The earliest known agricultural systems in this region
date to the Pre-Aksumite period (800–400 b.c.) and appear to have focused on Near Eastern crops, with indigenous African species increasing in importance during Aksumite
times (400 b.c.–a.d. 700). While palaeoethnobotanical data are available from Pre-Aksumite and late Aksumite periods, macroscopic botanical remains
from the site of Ona Nagast, northern Ethiopia, provide a first glimpse of agricultural systems dating to Proto-Aksumite (400–50
b.c.), Early to Classic (50 b.c.–a.d. 340), and Post-Aksumite (a.d. 700–900) times. Archaeological t’ef remains from Ona Nagast are examined in detail. Guidelines are developed for the identification
of t’ef grains preserved on archaeological sites, with a focus on how to differentiate them from seeds of wild Eragrostis species. Charring experiments reveal that in some cases t’ef may not survive high temperatures tolerated by larger cereal
grains, such as wheat and barley. The domestication history of t’ef appears to be different from some other cereals, a factor
which may explain the preponderance of indeterminate Eragrostis seeds in archaeological samples. Selection of large seed size and intensified tillage were not key factors in t’ef domestication.
Early cultivators were likely selecting for increased branching and higher percentage seed set under conditions of minimal
tillage. 相似文献
6.
Shinichi Yoshihiro Masaru Ohtake Hajime Matsubara Koichiro Zamma Goro Han'ya Yasuaki Tanimura Hiroyuki Kubota Ritsuko Kubo Tatsuhiro Arakane Toru Hirata Mari Furukawa Aki Sato Yukio Takahata 《Primates; journal of primatology》1999,40(2):409-415
A census of wild Yakushima macaques (Macaca fuscata yakui) was carried out in a 23-km2 area of the western coast of Yakushima Island, Japan. We analyzed the census data to investigate changes in monkey distribution
associated with the vertical distribution of vegetation. In the lowland coastal zone of 0–300 m above sea level (a.s.l.),
4.8 troops and 62.4–99.8 monkeys are estimated to have existed per km2. In the mountainside zones of 300–900 m a.s.l., the troop density decreased to 1.3–1.6 troops/km2. Since there was no difference in size between the coastal and mountainside troops, population density should decrease with
altitude to about 30–36 monkeys per km2. On the other hand, 2.4 troops and about 36 monkeys were estimated to have inhabited per km2 in the mountain summit zone of 900–1,323 m a.s.l.
Nature Conservation College 相似文献
7.
The transition from the early to the middle phase of the Late Neolithic (fourth–third millennium b.c.) is closely connected with the term “secondary products revolution”, which involves the adoption of animal traction and an
increased production of rendered animal commodities such as wool and dairy products. Based on measurements of Linum usitatissimum L. (flax) seeds and their abundance in 32 wetland settlements in southwest Germany, we presume that the introduction of a
new flax variety, maybe a better flax for fibre, and the intensification of flax cultivation were also a part of this process.
The morphometric analysis shows that flax seed sizes in the early phase of the Late Neolithic (4000–3400 cal. b.c.) differ significantly from those of the middle and latest phase (3400–2400 cal. b.c.). 相似文献
8.
André F. Lotter Oliver Heiri Wolfgang Hofmann Willem O. van der Knaap Jacqueline F. N. van Leeuwen Ian R. Walker Lucia Wick 《Vegetation History and Archaeobotany》2006,15(4):295-307
Palaeobotanical analysis and radiocarbon dating of lake sediments from Bachalpsee (2265 m a.s.l.), a small lake above the present-day timber-line in the northern Swiss Alps reveals that the region was already deglaciated during the Younger Dryas. The sediment record is dominated by long-distance transported pollen that originates from lowland vegetation but the plant macrofossils give evidence of the local vegetation development. Comparison with palaeobotanical results from three sites along an altitudinal transect permits the reconstruction of the regional timber-line history. Throughout the entire Holocene the catchment of Bachalpsee consisted of a mosaic of open meadows and dwarf shrubs (Salix, Vaccinium, Rhododendron). Chironomid and cladoceran assemblages suggest that the early to mid-Holocene was the warmest interval at Bachalpsee. Comparison of the palaeobotanical results with those from the mire “Feld” (2130 m a.s.l.) in the vicinity of Bachalpsee showed that during the mid-Holocene the timber-line was formed by Pinus cembra and Picea abies with some scattered Abies alba trees and was situated close to Bachalpsee but never reached its catchment. The maximum timber-line in the Northern Alps was reached between 6000 and 3000 cal b.p. which is several millennia later than in the Central Alps. The species composition of the tree-line (Abies alba, Pinus cembra and the absence of Larix decidua) points to less continental and moister climatic conditions compared with the central Alps during the early to mid-Holocene. From 3000 cal b.p. onwards the timber-line was lowered by human deforestation with the most intense pulses of human impact occurring since the Middle Ages. The catchment of Bachalpsee has been used as alpine pasture since the Bronze Age. 相似文献
9.
Guillermina Massaccesi Fidel A. Roig Guillermo J. Martínez Pastur Marcelo D. Barrera 《Trees - Structure and Function》2008,22(2):245-255
The influence of ecological factors resulting from altitude on growth characteristics of Nothofagus pumilio was analyzed. N. pumilio forests grow in the southern Andes from near sea level to 600 m.a.s.l. Eight study sites were selected in the southwestern
area of Tierra del Fuego, on north- and south-facing slopes, and distributed along an altitudinal gradient (200–600 m.a.s.l.).
Growth cycles throughout time were identified. The correlation between climate and tree growth was determined. Tree diameter
and height decreased whereas stand density increased towards tree-line. South-facing slopes showed higher values in common
growth variability, probably because of stronger climatic controlling factors. Climate-growth correlation models revealed
long-term temperature influences on growth variability, and showed variations among the different plots. Differences were
detected in the spectral power component of the chronologies throughout the altitudinal profile. The series had a significant
spectral peak at frequencies around 7 years, possibly related to mast seeding cycles. This signal became weaker as the altitude
increased probably due to lower seed production. These results suggest a strong altitudinal component in growth variability
of N. pumilio in Tierra del Fuego. 相似文献
10.
Two pollen diagrams from near the Chuya Basin, Russian Altai, are presented together with results from geomorphological archives.
The Kuray Range profile (2330 m a.s.l.) is situated just above the forest line and starts with the weak cooling of the middle
Atlantic period (ca. 6500–5900 b.p.) that bisects the Holocene optimum, as in other parts of Siberia. Taiga (boreal coniferous forest) with Picea obovata established afterwards but was displaced at ca. 5300 b.p. by the pronounced cooling of the early Sub-boreal. A gradual recovery of taiga stopped and it disappeared around 3400 b.p. at the end of the middle Sub-boreal. Since then the climatic and vegetational conditions much resemble those of the Sub-atlantic.
In the last two millennia, three climatic declines are documented in the second diagram from the Tarkhata Valley (2210 m a.s.l.)
from the dry limit of Larix sibirica: a cold and wet one around the 5th century a.d., a cold and dry one around a.d. 1200 and the Little Ice Age which started around a.d. 1600. In addition, several of the climatic periods and especially local human influence can be proved by the geomorphological
findings. Most of the climatic changes seem to be connected with socio-ecological changes in Asia and even Europe, with movements
of the Huns and Mongols, which show the possible dimensions of global climatic change. Hints of teleconnections between Siberia,
the Mediterranean and the Himalayas via the North Atlantic and the Arctic Oscillation are discussed. 相似文献
11.
The article presents archaeobotanical results from six late Neolithic excavation sites in eastern Austria. Two of the sites
belong to the Jevišovice culture (3200–2800 cal b.c.), the remaining four to the Baden culture (3600–2900 cal b.c.). Results show that farmers around 3000 cal b.c. were relying on the use of Triticum monococcum and Hordeum vulgare as principal cereals, with Triticum dicoccum and Panicum miliaceum as additional crops. Common millet was found in quantity at one of the Jevišovice sites and shows the remarkably early westward
spread of this species. Single records of Triticum spelta are discussed in the light of the recently proposed ideas about an independent central European origin of spelt. Another
record concerns the “new-type” glume wheat, providing further evidence for the once widespread occurrence of this cultivar.
Triticum aestivum (hexaploid naked wheat) and Setaria italica (foxtail millet) were found as rare admixtures at the Jevišovice settlements. Pulses were represented by Pisum sativum and Lens culinaris, oil plants by Papaver somniferum and Linum usitatissimum. One of the Jevišovice sites offered a good opportunity for a study of the undisturbed spatial distribution of charred plant
remains within a burnt house. Among wild plants, the occurrence of Stipa sp., Teucrium chamaedrys, Asperula cynanchica and Plantago media point to the presence of dry steppe grassland in the vicinity of the settlements, which was probably used for grazing. Woodland
plants were mainly represented by fruit-bearing plants growing in clearings and forest edges, reflecting both the deliberate
collection of wild fruits and the growing human impact on the vegetation. 相似文献
12.
Five altitudinal pteridophyte zones are established along the northeastern altitudinal slopes of Mt. Banahaw de Lucban, Quezon,
Luzon Is., Philippines using cluster- and ordination analyses, namely: Zone 1, Cyathea contaminans – Dicranopteris–Nephrolepis–Diplazium patches at 700–800 m a.s.l.; Zone 2, Sphaerostephanos hirsutus var. hirsutus – Selaginella delicatula patches at 750–900 m a.s.l.; Zone 3, Cyathea philippinensis – Selaginella patches at 900–1200 m a.s.l.; Zone 4, Cyathea philippinensis – Cyathea callosa–Asplenium cymbifolium–Selaginella cumingiana patches at 1200–1550 m a.s.l. and; Zone 5 which is further divided into Sub-zone 5A, Cyathea callosa – Cyathea loheri-Hymenophyllaceae patches at 1550–1800 m a.s.l. and Sub-zone 5B, Cyathea loheri – Cephalomanes apiifolia patches at 1800–1875 m a.s.l. These pteridophyte zones coincide with the woody species zones of Mt. Banahaw de Lucban but
differ significantly with the altitudinal fern zones of Mt. Makiling. Stepwise multiple regression analysis reveals that altitude
exhibits a linear relationship with pteridophyte species distribution. Altitude and soil pH influence 65% of the variation
in principal component 1 [PC1 = 0.0839 + 0.0010(altitude) − 0.2072(soil pH); r = 0.8058] and 27% of the variation in principal component 2 [PC2 = 2.0453 − 0.0005(altitude) − 0.2560(soil pH); r = 0.5206]. Thirty-three (33) species are preferential to specific microenvironments along the altitudinal gradient, making
them effective altitudinal zone markers and biodiversity conservation indicators for the forest ecosystem of Mt. Banahaw de
Lucban. 相似文献
13.
Zhao W Weber C Zhang CL Romanek CS King GM Mills G Sokolova T Wiegel J 《Extremophiles : life under extreme conditions》2006,10(4):337-345
A novel thermophilic, alkali-tolerant, and CO-tolerant strain JW/WZ-YB58T was isolated from green mat samples obtained from the Zarvarzin II hot spring in the Uzon Caldera, Kamchatka (Far East Russia). Cells were Gram-type and Gram stain-positive, strictly aerobic, 0.7–0.8 μm in width and 5.5–12 μm in length and produced terminal spherical spores of 1.2–1.6 μm in diameter with the mother cell swelling around 2 μm in diameter (drumstick-type morphology). Cells grew optimally at pH25°C 8.2–8.4 and temperature 50–52°C and tolerated maximally 6% (w/v) NaCl. They were strict heterotrophs and could not use either CO or CO2 (both with or without H2) as sole carbon source, but tolerated up to 90% (v/v) CO in the headspace. The isolate grew on various complex substrates such as yeast extract, on carbohydrates, and organic acids, which included starch, d-galactose, d-mannose, glutamate, fumarate and acetate. Catalase reaction was negative. The membrane polar lipids were dominated by branched saturated fatty acids, which included iso-15:0 (24.5%), anteiso-15:0 (18.3%), iso-16:0 (9.9%), iso-17:0 (17.5%) and anteiso-17:0 (9.7%) as major constituents. The DNA G+C content of the strain is 45 mol%. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain JW/WZ-YB58T is distantly (<93% similarity) related to members of Bacillaceae. On the basis of 16S rRNA gene sequence, physiological and phenotypic characteristics, the isolate JW/WZ-YB58T (ATCC BAA-1258; DSM 17740) is proposed to be the type strain for the type species of the new taxa within the family Bacillaceae, Thermalkalibacillus uzoniensis gen. nov. sp. nov. The Genbank accession number for the 16S rRNA gene sequence is DQ221694.The Genbank accession number for the 16S rRNA gene sequence of strain JW/WZ-YB58T is DQ221694. 相似文献
14.
Ruth Drescher-Schneider Jacques-Louis de Beaulieu Michel Magny Anne-Véronique Walter-Simonnet Gilles Bossuet Laurent Millet Elisabetta Brugiapaglia Anton Drescher 《Vegetation History and Archaeobotany》2007,16(4):279-299
Interdisciplinary studies of the sediments of Lago dell’Accesa started in 2001. We present here results from the palynological
study. The pollen diagram provides a record of vegetation and climatic change spanning over 15,000 years. The oldest pollen
spectra show a late-glacial steppe vegetation typical of central and southern Italy during this period. The Late-glacial Interstadial,
interrupted by two cooling events, is dominated by open deciduous oak forests. The Younger Dryas is represented by 150 cm
of sediment and shows the presence of steppic vegetation. The Holocene vegetation is characterised by alternating dominance
of deciduous oaks and Quercus ilex. The three zones characterised by Q. ilex are accompanied by peat layers marking lake-level lowering at ca. 8600–7900, 4600–4300 and 3700–2800 cal b.p. Between approximately 9000 and 6000 cal b.p. extensive Abies-forests existed on the Colline Metallifere located 15–20 km to the north and northeast of the lake. Local fir populations
may also have existed by the lake. Human impact starts at approximately 8000 cal b.p. during the Neolithic period, and increases at ca. 4300 cal b.p.
Castanea and Juglans pollen is recorded from ca. 2800 cal b.p. The impact of the Etruscan settlement near the lakeshore is shown in the increasing values of arable crops, species of secondary
forest canopy (Ericaceae, Pinus, Pistacia, Myrtus) and anthropogenic indicators (Chenopodiaceae, Plantago lanceolata, Rumex etc). 相似文献
15.
The archaeological site of Lavazzé at 2108 m a.s.l., and the summer farming site of Borghetto Sotto at 1897 m a.s.l., have
been studied using pollen analysis. The pollen diagrams reflect human disturbance from the Bronze and Neolithic ages respectively.
The name Lavazzé is also used as a local name for Rumex alpinus. At both sites, significant values of R. alpinus, up to about 10% of total terrestrial pollen, have been recorded, from about 2400 b.p. (ca 360 cal b.c.) onwards, although Lavazzé is above the present-day known local limit for R. alpinus. Written sources document local growth and cultivation of the species at 1300 m. It was used for various purposes in the
past, and the high values are interpreted as reflecting former intensive local growth. Local cultivation at higher altitudes
should not be excluded. Use of R. alpinus is known as far north as Scotland and Finland, and the species ought to be regarded as an apophyte and/or a naturalised crop. 相似文献
16.
María José Gil García María Blanca Ruiz Zapata Juan Ignacio Santisteban Rosa Mediavilla Enrique López-Pamo Cristino José Dabrio 《Vegetation History and Archaeobotany》2007,16(4):241-250
The use of a high resolution pollen record in combination with geochemical data from sediments composed mainly of layers of
charophytes alternating with layers of vegetal remains plus some detrital beds permits the reconstruction of the environmental
evolution of the last 3000 years in an inland wetland of the Mediterranean domain, thus introducing a new climatic dataset
for the Late Holocene. Hydrological fluctuations, reflected in the relationship between emerged and aquatic vegetation and
inorganic and organic C and N changes, can be related to aridity or humid phases, while relations among arboreal taxa (Quercus and Pinus) and Artemisia are used as temperature indicators. Five climatic periods have been identified: a Subatlantic Cold Period (<150 b.c.), cold and arid; the Roman Warm Period (150 b.c.–a.d. 270), warmer and wetter; the Dark Ages (a.d. 270–a.d. 950), colder and drier; the Medieval Warm Period (a.d. 950–a.d. 1400), warmer and wetter; and the Little Ice Age (>a.d. 1400) indicated by a cooling and drying trend. Despite the lack of any direct evidence of human action, there are some episodes
related to deforestation during the Reconquista (Middle Ages) that mask the real climatic signal. 相似文献
17.
Plantaricin A (PlnA) is a 26-mer peptide pheromone with membrane-permeabilizing, strain-specific antibacterial activity, produced
by Lactobacillus plantarum C11. We investigated the membrane-permeabilizing effects of PlnA on cultured cancerous and normal rat anterior pituitary
cells using patch-clamp techniques and microfluorometry (fura-2). Cancerous cells displayed massive permeabilization within
5 s after exposure to 10–100 μm PlnA. The membrane depolarized to nearly 0 mV, and the membrane resistance decreased to a mere fraction of the initial value after less than 1 min. In outside-out membrane
patches, 10 μm PlnA induced membrane currents reversing at 0 mV, which is compatible with an unspecific conductance increase. The d and l forms of the peptide had similar potency, indicating a nonchiral mechanism for the membrane-permeabilizing effect. Surprisingly,
inside-out patches were insensitive to 1 mm PlnA. Primary cultures of normal rat anterior pituitary cells were also insensitive to the peptide. Thus, PlnA differentiates
between plasma membranes and membrane leaflets. Microfluorometric recordings of [Ca2+]
i
and cytosolic concentration of fluorochrome verified the rapid permeabilizing effect of PlnA on cancerous cells and the insensitivity
of normal pituitary cells. 相似文献
18.
Lignocellulosic biomass, particularly corn fiber, represents a renewable resource that is available in sufficient quantities
from the corn wet milling industry to serve as a low cost feedstock for production of fuel alcohol and valuable coproducts.
Several enzymatic and chemical processes have potential for the conversion of cellulose and hemicellulose to fermentable sugars.
The hydrolyzates are generally rich in pentoses (D-xylose and L-arabinose) and D-glucose. Yeasts produce a variety of polyalcohols from pentose and hexose sugars. Many of these sugar alcohols have food
applications as low-calorie bulking agents. During the screening of 49 yeast strains capable of growing on L-arabinose, we observed that two strains were superior secretors of L-arabitol as a major extracellular product of L-arabinose. Candida entomaea NRRL Y-7785 and Pichia guilliermondii NRRL Y-2075 produced L-arabitol (0.70 g/g) from L-arabinose (50 g/l) at 34°C and pH 5.0 and 4.0, respectively. Both yeasts produced ethanol (0.32–0.33 g/g) from D-glucose (50 g/l) and only xylitol (0.43–0.51 g/g) from D-xylose (50 g/l). Both strains preferentially utilized D-glucose>D-xylose>L-arabinose from mixed substrate (D-glucose, D-xylose and L-arabinose, 1:1:1, 50 g/l, total) and produced ethanol (0.36–0.38 g/g D-glucose), xylitol (0.02–0.08 g/g D-xylose) and L-arabitol (0.70–0.81 g/g L-arabinose). The yeasts co-utilized D-xylose (6.2–6.5 g/l) and L-arabinose (4.9–5.0 g/l) from corn fiber acid hydrolyzate simultaneously and produced xylitol (0.10 g/g D-xylose) and L-arabitol (0.53–0.54 g/g L-arabinose).
Received: 24 April 1995/Received revision: 9 August 1995/Accepted: 7 September 1995 相似文献
19.
J. N. Harney E. E. Grossman B. M. Richmond C. H. Fletcher III 《Coral reefs (Online)》2000,19(2):141-154
The origin, age, and dynamics of carbonate sediments in Kailua Bay on Oahu, Hawaii, are described. The shoreface (from shoreline
to 4 km offshore) consists of a broad (5 km2) fringing coral reef ecosystem bisected by a sinuous, shore-normal, sand-filled paleostream channel 200–300 m wide. The median
grain diameter of surface sands is finest on the beach face (<0.3 mm) and increases offshore along the channel axis. Kailua
sands are >90% biogenic carbonate, dominated by skeletal fragments of coralline algae (e.g. Porolithon, up to 50%) followed by the calcareous green alga Halimeda (up to 32%), coral fragments (1–24%), mollusc fragments (6–21%), and benthic foraminifera (1–10%). Sand composition and age
across the shoreface are correlated to carbonate production. Corals and coralline algae, principal builders of the reef framework,
are younger and more abundant in sands along the channel axis and in offshore reefal areas, while Halimeda, molluscs, and foraminifera are younger and more dominant in nearshore waters shoreward of the main region of framework building.
Shoreface sediments are relatively old. Of 20 calibrated radiocarbon dates on skeletal constituents of sand, only three are
younger than 500 years b.p.; six are 500–1000 years b.p.; six are 1000–2000 years b.p.; and five are 2000–5000 years b.p. Dated fine sands are older than medium to coarse sands and hence may constitute a reservoir of fossil carbonate that is
distributed over the entire shoreface. Dominance of fossiliferous sand indicates long storage times for carbonate grains,
which tend to decrease in size with age, such that the entire period of relative sea-level inundation (∼5000 years) is represented
in the sediment. Despite an apparently healthy modern coral ecosystem, the surficial sand pool of Kailua Bay is dominated
by sand reflecting an antecedent system, possibly one that existed under a +1–2 m sea-level high stand during the mid- to
late Holocene.
Accepted: 20 December 1999 相似文献
20.
Analyses of pollen, macrofossils and microscopic charcoal in the sediment of a small sub-alpine lake (Karakol, Kyrgyzstan)
provide new data to reconstruct the vegetation history of the Kungey Alatau spruce forest during the late-Holocene, i.e. the
past 4,000 years. The pollen data suggest that Picea schrenkiana F. and M. was the dominant tree in this region from the beginning of the record. The pollen record of pronounced die-backs
of the forests, along with lithostratigraphical evidence, points to possible climatic cooling (and/or drying) around 3,800
cal year b.p. and between 3,350 and 2,520 cal year b.p., with a culmination at 2,800–2,600 cal b.p., although stable climatic conditions are reported for this region for the past 3,000–4,000 years in previous studies. From
2,500 to 190 cal year b.p. high pollen values of P. schrenkiana suggest rather closed and dense forests under the environmental conditions of that time. A marked decline in spruce forests
occurred with the onset of modern human activities in the region from 190 cal year b.p. These results show that the present forests are anthropogenically reduced and represent only about half of their potential
natural extent. As P. schrenkiana is a species endemic to the western Tien Shan, it is most likely that its refugium was confined to this region. However,
our palaeoecological record is too recent to address this hypothesis thoroughly. 相似文献