Holocene vegetation and water level history in two bogs of the Cordillera de Talamanca, Costa Rica

Pollen records of Holocene sediment cores from the Costa Rican Cordillera de Talamanca (La Chonta bog, 2310 m and La Trinidad bog, 2700 m) show the postglacial development of the montane oak forest zone from ca. 9500 to 1500 yr BP. During the early Holocene (ca. 9500–700 yr BP), alder vegetation covered the La Chonta and La Trinidad bogs and their adjacent hills. The upper forest line is inferred to be at 2800–3000 m elevation. A Podocarpus-Quercus forest characterised the middle Holocene (ca. 7000–4500 yr BP). The upper forest line is located at >3000 m reaching the present-day altitudinal distribution. A Quercus forest characterised the late Holocene (ca. 4500–1500 yr BP). Compared to modern conditions, the early Holocene has similar average temperatures, but the moisture level was probably higher. Pollen evidence for the late Holocene indicates drier environmental conditions than today. In order to improve the paleoecological interpretation, we described the local vegetation and used moss samples as pollen traps at both montane bogs along strong soil moisture gradients.The Netherlands Centre for Geo-ecological Research, ICG     

Zelkova carpinifolia (Pallas) K. Koch in Holocene sediments of Georgia—an indicator of climatic optima

Zelkova pollen has been found in Oligocene- to Pleistocene-aged deposits from many parts of Europe and northern Africa, but became extinct in mainland Europe prior to the last glacial maximum. This paper presents some observations on the ecology, pollen productivity and Holocene history of Zelkova carpinifolia to further understanding of Quaternary climatic trends. Georgia is one of the last refuges of this Tertiary relict tree.Based on palynological data from 20 Holocene sediment profiles in Georgia, we have established that Zelkova pollen is almost always accompanied by elevated proportions of thermophilous taxa (Castanea sativa, Quercus hartwissiana, Quercus iberica, and Pterocarya pterocarpa) in pollen spectra. These spectra are associated with phases of climatic amelioration and humidification. Zelkova carpinifolia is characterised by low pollen productivity and is underrepresented in pollen spectra by four-to-five orders of magnitude. Because of this, even single grains of Zelkova pollen may play a significant role in pollen-based climatic reconstructions.Six major climatic optima occurred in Georgia through the course of the Holocene, the longest and warmest of which occurred in the mid-Holocene and reached its maximum between 6000 and 5500 Cal. yr BP. During that period, Zelkova and Castanea forests were widespread. In Western Georgia, the upper tree line was elevated by as much as 300 m above its present-day level. In semiarid Eastern Georgia, the tree line may have been 500–600 m higher. Other climatic optima are seen in late-Holocene pollen spectra dating to 3800–2500 Cal. yr BP and 1350–800 Cal. yr BP.     

Vascular plant diversity and climate change in the alpine zone of the Snowy Mountains,Australia

This study examines vascular plant species richness along an altitudinal gradient in alpine Australia. Vascular plant composition and soil temperature records were obtained for five summits (from 1729 m to 2114 m a.s.l.) using sampling protocols from the Global Observation Research Initiative in Alpine Environments program. Species richness was examined against altitude, aspect and climatic variables at different spatial scales (10 × 10 cm quadrats, 1 m² quadrats, clusters of 4 * 1 m² quadrats, for the summit area above a line 5 m altitudinally below the summit (the −5 m isoline), for the extended summit down to the −10 m isoline). About 75 taxa (70 species, 5 graminoid genera) were recorded, 9 of which are endemic to the small alpine area of ∼100 km². There were significant linear relationships between species richness and altitude and climatic variables for the top to −5 isolines on the summits. However, there was no consistent pattern for species richness at other spatial scales, altitude, aspect or climatic variables. The proportion of species for the whole summits with localised distributions (local endemics) increased with altitude. Predicted increasing temperatures and reduced snowcover is likely to result in an increase in species richness as shrubs, herbs and introduced weeds become more common at higher altitude. Because Australian alpine areas occur in narrow altitudinal bands with no nival zone, there are no higher altitudinal refuges available for alpine species. Therefore many of these species are likely to be at risk of extinction from climate change.     

Influence of altitude on the distribution pattern of flora in a protected area of Western Himalaya

IntroductionDistribution pattern and diversity of flora was compared along an altitudinal gradient using the stratified random sampling design for identifying major plant communities of Kedarnath Wildlife Sanctuary of Garhwal Himalaya, India. The reconnaissance of flora is presented, along with the analysis of the distribution of species, genera, and families within five (5) altitudinal zones. Kedarnath Wildlife Sanctuary which is situated in the Indian Himalayas harbours a rich variety of flora and fauna. The Himalayas are recognized for diverse vegetation distributed over a wide range of topographical conditions.ResultsThe analysis of diversity within five (5) altitudinal zones was carried out and a total of 324 plant species, representing 219 genera belonging to 92 families, were found. The dominant family was Asteraceae; the co-dominant family was Rosaceae, followed by Lamiaceae and Ranunculaceae. Eight (8) families were observed in all the altitudinal zones, while forty (40) families were observed in a single altitudinal zone, and the remaining forty-four (44) families were found in more than one (1) altitudinal zone. Most of the tree species were contagiously distributed, but a few of them were randomly distributed in all the altitudinal zones. The shrubs and herbs were contagiously distributed in all the altitudinal zones. The correlation analysis (P < 0.05) between altitude and number of species showed that altitude is negatively correlated with tree (r = −0.96), shrub (r = −0.61), and herb species (r = −0.20). As per the cluster analysis of tree layer, altitudinal zone - III (2450–2650 m) and altitudinal zone - IV (2900–3100 m) were found most similar. Altitudinal zone–V (3350–3550 m) was found to be dissimilar from the other zones for herbs.ConclusionsAlthough species composition varies with altitude, but there is a complex relationship between species richness and altitudinal gradient. A decreasing pattern in both species richness and family richness for trees, shrubs and herbs, was recorded with increasing altitude. The predominant factors underlying this variability in plant species and biogeography appear to be climatic and specific to each taxonomic group.     

An altitudinal transect study of the vegetation on Mount Kinabalu,Borneo

A quantitative transect analysis of altitudinal sequences of forest canopy species from 600 to 3400 m asl on Mt. Kinabalu (4101 m), Borneo, resulted in four discrete altitudinal vegetation zones. These were made up of mutually exclusive species groups for lowland (<1200 m asl), lower montane (1200 to 2000–2350 m asl), upper montane (2000–2350 to 2800 m asl), and subalpine (2800 to the forest line, 3400 m asl) zones. Zonal soil types were correlated with the vegetation zones. In upslope sequence, these were: lowland Oxisols, montane Histosol/Spodosol complex, and subalpine Inceptisols. The highest contents of organic carbon, extractable phosphorus, and exchangeable magnesium and potassium were recorded in the lower and upper montane zones. The upper boundaries of the lowland, upper montane and subalpine zones coincided with thermal thresholds of latitudinal bioclimatic zones: 18°C TMIN (Köppen's tropical), WI 85 (Kira's warm temperate), and WI 45 (Kira's cool temperate), respectively. The upper limit of the lower montane zone was correlated with an abrupt increase of water surplus estimated from the annual rainfall minus annual potential evaporation. These climatic characteristics appear to define ecological altitudinal turnover points, so called critical altitudes, where groups of associated species are displaced by other groups.Abbreviations asl = above sea level - DBH = diameter at breast height - PHQ = Park headquarters - TMAX = Mean daily maximum air temperature - TMIN = Mean daily minimum air temperature - TWINSPAN = Two-way indicator species analysis - WI = Warmth index     

Species Diversity and Life-Form Patterns in Steppe Vegetation along a 3000 m Altitudinal Gradient in the Alborz Mountains, Iran

Biodiversity pattern and life-form spectra were studied along a 3,000 m altitudinal gradient from a semi-desert area to the alpine peak of Tochal Mountain. The gradient is located on the southern slopes of Central Alborz with a Mediterranean continental climate. DCA ordination was applied to 1,069 relevés and 7 quantitative variables to discover the relation of diversity and altitude. A biodiversity pattern was obtained by relating values for species richness and Shannon-Wiener’s index to 100-m altitudinal sections. Altitude was determined as the major ecological gradient. Both diversity indices are negatively correlated with altitude and show a decreasing trend beyond a peak in species richness at 1,800–1,900 m a.s.l. towards a very low diversity in the high alpine zone. The biodiversity peak does not match with the potential tree line in the area (2,500–3,000 m a.s.l.). The high diversity in foothills can be related to habitat heterogeneity, longer suitable climatic conditions, and diverse disturbance factors, while unfavorable conditions at high-altitude alpine and low-altitude desert areas reduce the number of species at both extremes. Life-form patterns clearly change along altitudinal gradient. Annuals with decreasing trend, and hemicryptophytes and chamaephytes with increasing trend along the altitudinal gradient are notable patterns of life form in the area. Temperature, soil moisture and nutrients are the main factors that explain the ecological influence of altitude on species diversity and life-form patterns in the semi-arid steppe vegetation of the area.     

Upward migration of vascular plants following a climate warming trend in the Alps

The aim of this study was to understand (1) whether warmer climatic conditions affected the vascular plant species composition, (2) the magnitude and rate of altitudinal changes in species distributions, and (3) whether an upward migration of alpine plants is connected to wind dispersal of diaspores. We compared historical records (1954–1958) with results from recent plant surveys (2003–2005) from alpine to nival ecosystems in the Rhaetian Alps, N-Italy. The presence of all vascular plant species and their maximum altitude were recorded along a continuous altitudinal transect of 730 m. An increase in species richness from 153 to 166 species was observed. Moreover, 52 species were recorded from altitudes 30–430 m higher than their 1950s limits, which corresponds to a median migration rate of 23.9 m/decade. In order to explain the observed migrations, the species wind-dispersal ability (diaspore weight and morphology) and the air temperature variation from 1926 to 2003 were considered. Species with more pronounced altitudinal shifts possess lighter diaspores. The highest increase in species richness was found between 2800 and 3100 m a.s.l.; this appears to be related to an estimated shift of the permafrost limit by +240 m during the last 50 years. The mean air temperature in the region rose by +1.6 °C in summer and by +1.1 °C in winter within this period. Climate warming is therefore considered as a primary cause of the observed upward migration of high mountain plants. Calculated altitudinal migration rates, however, varied remarkably among species. This would imply differential abilities of species to persist in an increasingly warmer climate. Species-specific conservation measures, including ex situ conservation, may therefore be required.     

Uphill shifts in the distribution of the white stork Ciconia ciconia in southern Poland: the importance of nest quality

The aim of this paper is to explain the altitudinal changes that have occurred during the 20th century to the white stork distribution in the Podhale region of the uplands of the Tatra mountains, southern Poland. We analysed both historical data from the white stork censuses and detailed yearly records from 1974 to 2003 on population size, distribution and breeding success. A white stork nest was first recorded at Podhale in 1931 and numbers increased to seven nests in 1933, all located below 650 m altitude. During the 30‐years, 1974–2003, both the maximum and upper‐quartile altitudes of nests increased significantly. In 1974 the highest nest was at an altitude of 770 m, and the maximum reached 890 m in 1999. In the same period, the breeding population increased significantly. The minimum and lower‐quartile altitudes of nests decreased significantly following initial occupation of suitable lower altitude sites before uphill expansion. We noted the positive association between nest occupancy over the study period and breeding performance. As a result, long‐occupied nests contributed most of the young produced in the population and chicks from these nests probably colonized new areas. We believe this is the first well‐documented evidence of, and mechanism for, a particular bird species to ascend to higher elevations and that the altitudinal shifts reported for butterflies, plants and whole biomes can be detected in birds as well.     

Vegetation development and human activities in Attiki (SE Greece) during the last 5,000?years

Pollen assemblages recovered from a 5?m sediment core from the Vravron coastal marsh suggest a close correlation between vegetation development and human presence in Attica, and provide the first complete record of middle to late Holocene vegetation history. Correlation of pollen with archaeological data attempts to decode the man–environment relations of the past, within the context of the known climatic variability of the mid-late Holocene, in the vicinity of ancient Athens, an area of high historical significance. The pollen record of Vravron denotes a rather variable landscape where open Mediterranean evergreen pine woods alternated with maquis shrublands and grasslands, where human activities and climate have left their imprints on vegetation. During the last 5,000?years agricultural practices displayed several variations: cereal cultivation appears more intense during the Bronze Age, especially in the Mycenaean, while a spread of Olea is observed during Geometric to Classical times. The gradual abandonment of Olea cultivation evidenced in our pollen diagram came as a result of the displacement of human activities in the interior of Mesogaia in Hellenistic and Roman times. Olea and cereal cultivation intensification is observed again during the Mesobyzantine period. In the upper part of the core evidence of intense soil erosion and expansion of Vravron wetland was recorded, coinciding with the Little Ice Age climatic event and the introduction of Arvanites populations in the area.     

Multi-scale altitudinal patterns in species richness of land snail communities in south-eastern France

Aim Species richness is an important feature of communities that varies along elevational gradients. Different patterns of distribution have been described in the literature for various taxonomic groups. This study aims to distinguish between species density and species richness and to describe, for land snails in south‐eastern France, the altitudinal patterns of both at different spatial scales. Location The study was conducted on five calcareous mountains in south‐eastern France (Etoile, Sainte Baume, Sainte Victoire, Ventoux and Queyras). Methods Stratified sampling according to vegetation and altitude was undertaken on five mountains, forming a composite altitudinal gradient ranging from 100 to 3100 m. Visual searching and analysis of turf samples were undertaken to collect land snail species. Species density is defined as the number of species found within quadrats of 25 m². Species richness is defined as the number of species found within an elevation zone. Different methods involving accumulation curves are used to describe the patterns in species richness. Elevation zones of different sizes are studied. Results Eighty‐seven species of land snails were recovered from 209 samples analysed during this study. Land snail species density, which can vary between 29 and 1 species per 25 m², decreases logarithmically with increasing altitude along the full gradient. However, on each mountain separately, only a linear decrease is observable. The climatic altitudinal gradient can explain a large part of this pattern, but the great variability suggests that other factors, such as heterogeneity of ground cover, also exert an influence on species density. The altitudinal pattern of species richness varies depending on the spatial resolution of the study. At fine resolution (altitudinal zones of 100 m) land snail species richness forms a plateau at altitudes below 1000 m, before decreasing with increasing altitude. At coarse resolution (altitudinal zones of 500 and 1000 m) the relationship becomes linear. Main conclusions This study reveals that land snail species density and land snail species richness form two different altitudinal patterns. Species density exhibits strong variability between sites of comparable altitude. A large number of samples seem necessary to study altitudinal patterns of species density. Species density decreases logarithmically with increasing altitude. Above a critical altitudinal threshold, this decrease lessens below the rate seen in the first 1500 m. Different methods exist to scale‐up species density to species richness but these often produce different patterns. In this study, the use of accumulation curves has yielded a pattern of species richness showing a plateau at low altitude, whereas simple plotting of known altitudinal ranges from single mountains would have produced stronger mid‐altitudinal peaks. This study shows that not only factors such as temperatures and habitat heterogeneity, but also an ecotone effect, are responsible for the observed patterns.     

Brain size variation along altitudinal gradients in the Asiatic Toad (Bufo gargarizans)

Size changes in brain and brain regions along altitudinal gradients provide insight into the trade‐off between energetic expenditure and cognitive capacity. We investigated the brain size variations of the Asiatic Toad (Bufo gargarizans) across altitudes from 700 m to 3,200 m. A total of 325 individuals from 11 sites and two transects were sampled. To reduce confounding factors, all sampling sites within each transect were within a maximum distance of 85 km and an altitudinal difference close to 2,000 m. Brains were dissected, and five regions were both measured directly and with 3D CT scan. There is a significant negative correlation between the relative whole‐brain volume (to snout‐vent length) and altitude. Furthermore, the relative volumes (to whole‐brain volume) of optic tectum and cerebellum also decrease along the altitudinal gradients, while the telencephalon increases its relative volume along the gradients. Therefore, our results are mostly consistent with the expensive brain hypothesis and the functional constraint hypothesis. We suggest that most current hypotheses are not mutually exclusive and data supporting one hypothesis are often partially consistent with others. More studies on mechanisms are needed to explain the brain size evolution in natural populations.     

Environmental changes in the northeast of the Buryat Republic during the Holocene post-Optimum: First results

The results of a high-temporal-resolution geochemical and pollen analysis of bottom sediments in Lake Baunt (55°11′15″ N and 113°01′45″ E), located within the continuous permafrost zone, have made it possible to reconstruct the environmental and climate changes in northern Buryatia during the Holocene post-Optimum for the first time. Over the last almost 7000 years, the natural and climatic conditions in the northeast of Buryatia have not remained homogeneous. A relatively warm and dry climate occurred here at the end of the Holocene Optimum between 6900 and 6000 BP. Later, about 6000–1500/1000 BP, the climate became colder, long-term permafrost activated, and chemical weathering attenuated. The climate over the last 1500–1000 years was colder in general than the modern climate. The environmental indices have different values in sediments with respect to warm and cold intervals and reflect the sedimentation conditions what were controlled by climate changes.     

Morphometric cranial identity of prehistoric Malawians in the light of sub-Saharan African diversity

Little has been described of the Holocene populations of South‐Central Africa, despite the region demonstrating major subsistence shifts relating to dispersals of agriculturalists at least 2,000 years ago. Seven sites with associated human skeletal remains were selected. Hora, Chencherere, Fingura, and Mtuzi represent the Middle Holocene (2,000–5,000 years ago), and Phwadze, Mtemankhokwe, and Nkudzi Bay represent the Late Holocene and the arrival of agriculturalists between 500–2,000 years ago. Focusing on the identity of Hora and Chencherere specimens, two questions were addressed: are the various Holocene Malawians similar to each other, or do they suggest morphological change over time? What modern populations are closest to the prehistoric specimens? The archaeological sample was compared to modern sub‐Saharan Africans from four regions, plus a historic Khoi‐San foraging group. Factor analyses were performed in order to identify complex patterns of variation in metric traits of the skull. According to the results, prehistoric Malawians showed only slight differences between the Late and Middle Holocene, suggesting a population change without any major discontinuity. Later Stone Age skulls did not exclusively show similarities with the Khoi‐San, as they frequently fit well within the variation of modern Bantu‐speaking groups, especially West‐Central Africa. Therefore, we reject the hypothesis that Middle Holocene South‐Central Africans have an exclusively Khoi‐San ancestry, and support an alternative hypothesis that both Middle and Late Holocene groups share a common biological heritage originating in West‐Central Africa in earlier times. Am J Phys Anthropol, 2006. © 2005 Wiley‐Liss, Inc.     

高黎贡山种子植物物种丰富度沿海拔梯度的变化

物种丰富度沿海拔梯度的分布格局成为生物多样性研究的热点。为探讨中尺度区域物种丰富度沿海拔梯度的分布,本文以高黎贡山为研究对象,利用该地区的地方植物志资料,结合通过GIS生成的区域数字高程模型(DEM)数据,分析了该区域全部种子植物和乔木、灌木、草本三种生活型种子植物物种丰富度的垂直分布格局以及物种密度沿海拔梯度的变化特征。结果表明：(1)全部种子植物和不同生活型植物物种丰富度随着海拔的升高呈现先增加后减小的趋势,最大值出现在海拔1500—2000m的范围;(2)物种密度与海拔也呈现单峰曲线关系;(3)物种丰富度和物种密度分布格局的形成主要受海拔所反映的水、热状况组合以及物种分布的边界影响。     

The distribution of ground spiders (Araneae, Gnaphosidae) along the altitudinal gradient of Crete, Greece: species richness, activity and altitudinal range

Aim To study the altitudinal variation of ground spiders (Araneae, Gnaphosidae) of Crete, Greece, as far as species composition, species richness, activity and range of distribution are concerned. Location Altitudinal zones (0–2400 m) along the three main mountain massifs of the island of Crete. Methods Thirty‐three sampling sites were located from 0 to 2400 m a.s.l. on Crete, and sampled using pitfall traps. Material from the high‐activity period of Gnaphosidae (mid‐spring to mid‐autumn) was analysed. Sampling sites were divided into five altitudinal zones of 500 m each. Statistical analysis involved univariate statistics (anova ) and multivariate statistics, such as multidimensional scaling (MDS) and cluster analysis (UPGMA) using binomial data of species presence or absence. Results Species richness declines with altitude and follows a hump‐shaped pattern. The activity pattern of the family, as a whole, is not correlated with altitude and is highly species‐specific. In the highest zone, both species richness and activity decline dramatically. The altitudinal range of species distribution increases with altitude. On the Cretan summits live highly tolerant lowland species and isolated residents of the high mountains of Crete. Two different patterns of community structure are recorded. Main conclusions Communities of Gnaphosidae on Crete present two distinct structures following the altitudinal gradient, these being separated by a transitional zone between 1600 and 2000 m. This study supports previous results which show a hump‐shaped decline in species richness of Gnaphosidae along altitudinal gradients, leading to a peak at 400–700 m, where an optimum of environmental factors exists. This makes this zone the meeting point of the often opportunistic lowland species with the older and most permanent residents of the island. Rapoport's rule on the positive correlation of the altitudinal range of species distributions with altitude is also supported. The high activity recorded for the species that persist on the high mountains of Crete is indicative of a tolerant arachnofauna, and is considered to result from relaxation of competitive interactions with other species. This is related to a reduction in species numbers, shortening of the activity period on high mountains and the unique presence of high mountain species that thrive only there. As shown in our study, strategies to cope with altitude are species‐specific. Therefore, there cannot exist one single model to describe how animals react to the change in altitude, even under the same environmental conditions.     

Determinants of northerly range limits along the Himalayan bird diversity gradient

The primary explanation for the latitudinal gradient in species diversity must lie in why species fail to expand ranges across different climatic regimes. Theories of species gradients based in niche conservatism assume that whole clades are confined to particular climatic regimes because the traits they share limit adaptation to alternative regimes. We assess these theories in an analysis of the twofold decline in bird species richness along the Himalayas from the southeast to the northwest. The presence of fewer species in the northwest is entirely due to a steep decline in the number of forest species; species occupying more open habitats show a reversed gradient. Forest species numbers are exceptionally high at midelevations (1,000-2,000 m) in the southeast, which experience a warm, wet climate not present in the northwest, and a high proportion of these species fail to expand their range to the northwest. Despite this, many species do have populations or close relatives that straddle different climatic regimes along altitudinal gradients and/or the regional gradient, implying that climate-based niche conservatism per se does not strongly constrain range limits. We argue that climate- and competition-mediated resource distributions are important in setting northerly range limits and show that one measure of forest resources (foliage density) is lower in the northwest.     

Distribution et caractéristiques des associations d’ostracodes au Pléistocène supérieur et Holocène au niveau de la marge orientale du détroit de Gibraltar (mer d’Alboran, Maroc)

A detailed study of the upper Pleistocene and Holocene ostracode fauna from the Moroccan margin of the Western Mediterranean is here presented based on sediments of three cores drilled near the Straits of Gibraltar (Sea of Alboran), between 300 and 550 m of depth. Information on the quantitative and qualitative distribution of the ostracodes was obtained, for the first time, in this area. This study also allowed to identify recall the main climatic and eustatic variations as recorded in the sediments and the faunal composition and to identify the corresponding chronological limits from the last glacial maximum to the present time.     

Biological invasion on an oceanic island mountain: Do alien plant species have wider ecological ranges than native species?

Abstract. Spatial distribution patterns of alien plant species were compared with those of native species on a windward slope of Mt. Haleakala (3055 m). Oceanic islands are considered susceptible to biological invasion, and this study numerically tested this circumstantial evidence with the following questions: Are all habitats equally susceptible; and, do successful invaders have wider realized niches than natives? The mountain slope consists of three distinct altitudinal bioclimatic zones (hot moist lowland, wet montane cloud, and cool arid high-altitude zones). Ordination indicated that alien species' ranges and population expansions were clustered in the lowland and high-altitude zones. The lowland zone had been subjected to natural canopy dieback, and the high-altitude zone to grazing by domestic and feral ungulates. By contrast, the montane cloud forest was relatively intact in terms of number and cover of native species. Thus, susceptibility to alien invasion clearly differed among zones, and the primary causes seemed to be the obvious disturbance factors. The mean ecological range along the altitude-rainfall gradient was significantly (P < 0.05) greater for native than for alien species in most life-form groups. The reasons for the greater number of climate generalists among the natives vs. the range-restricted aliens appear to be related to: (1) the pre-alien condition with a depauperate flora which allowed for ‘ecological release’ of successful native colonizers, and (2) the climatic pre-adaptation of alien invaders which restricts them from penetrating over a broader spectrum of climatic zones in a floristic matrix subjected to increasing interspecific competition.     

Can we detect a west Norwegian tree line from modern samples of plant remains and pollen? Results from the DOORMAT project

In the DOORMAT (Direct Observation of Recent Macrofossils Across Treeline) project, the modern representation of local vegetation by pollen and plant remains (plant macrofossils) across a west Norwegian tree line, composed of Betula pubescens and Pinus sylvestris, has been studied over 2 years. The aim was to discover if the modern tree line could be detected and therefore how precisely past tree-line movements could be reconstructed and related to Holocene climate changes by using one proxy or a combination of both. Traps were placed in the vegetation from 663 to 1,120 m a.s.l., spanning the pine altitudinal species limit, the birch tree-line ecotone, and the vegetation zones up to the mid-alpine zone. Three traps were also set in the small lake Trettetjørn close to the modern tree line at 800 m a.s.l. Traps were emptied twice a year to sample both summer and winter seasons. Macrofossils represent their local vegetation well. However, tree Betula remains were trapped above the tree line and Pinus and Picea remains were recorded 1.0–1.5 km away from their sources, demonstrating considerable dispersal capacity. This shows that rare macrofossil remains do not necessarily represent the local presence of these trees. Aerial tree pollen deposition in traps at the upper limit of pine woodland and in the subalpine birch woodland was unexpectedly low, whereas pollen accumulation rates (PAR) were orders of magnitude higher in the lake traps. We hypothesise that the lake receives regional pollen rain washed in from its catchment by snow meltwater and that high values in traps are due to continuous suspension of pollen in the lake water during summer. The interpretation of tree-line changes from existing Holocene pollen and plant macrofossil data from Trettetjørn was supported and refined by the DOORMAT macrofossil data, but the modern pollen data were anomalous.     

Bryophyte Species Richness and Composition along an Altitudinal Gradient in Gongga Mountain,China

An investigation of terrestrial bryophyte species diversity and community structure along an altitudinal gradient from 2,001 to 4,221 m a.s.l. in Gongga Mountain in Sichuan, China was carried out in June 2010. Factors which might affect bryophyte species composition and diversity, including climate, elevation, slope, depth of litter, vegetation type, soil pH and soil Eh, were examined to understand the altitudinal feature of bryophyte distribution. A total of 14 representative elevations were chosen along an altitudinal gradient, with study sites at each elevation chosen according to habitat type (forests, grasslands) and accessibility. At each elevation, three 100 m × 2 m transects that are 50 m apart were set along the contour line, and three 50 cm × 50 cm quadrats were set along each transect at an interval of 30 m. Species diversity, cover, biomass, and thickness of terrestrial bryophytes were examined. A total of 165 species, including 42 liverworts and 123 mosses, are recorded in Gongga mountain. Ground bryophyte species richness does not show any clear elevation trend. The terrestrial bryophyte cover increases with elevation. The terrestrial bryophyte biomass and thickness display a clear humped relationship with the elevation, with the maximum around 3,758 m. At this altitude, biomass is 700.3 g m⁻² and the maximum thickness is 8 cm. Bryophyte distribution is primarily associated with the depth of litter, the air temperature and the precipitation. Further studies are necessary to include other epiphytes types and vascular vegetation in a larger altitudinal range.