Short-term signals of climate change along an altitudinal gradient in the South Alps

Short-term changes in plant species number, frequency and composition were studied along an altitudinal gradient crossing four summits from the treeline ecotone to the subnival zone in the South Alps (Dolomites, Italy). Large-scale (summit areas) and small-scale patterns (16 plots of 1 m2/summit) were monitored. After 5 years, a re-visitation of the summit areas revealed a considerable increase of species richness at the upper alpine and subnival zone (10% and 9%, respectively) and relatively modest increases at the lower alpine zone and the treeline ecotone (3% and 1%, respectively). At the small scale, the results were partly different, with species richness decreasing at the lower summits and increasing at the higher summits. The changes can most likely be attributed to climate warming effects and to competitive interactions. The main newcomers at the lower three summits were species from the treeline and the lower altitudinal zones. Only at the highest summit, the newcomers came from the alpine species pool. At the treeline ecotone, the abundance of Pinus cembra, of dwarf shrubs and clonal graminoid species increased. Here, displacements of alpine species may be predicted for the near future. At the higher summits, expansions of the established alpine species and further invasions of species from lower altitudes are forecasted.     

Sympatric diploid and hexaploid cytotypes of Senecio carniolicus (Asteraceae) in the Eastern Alps are separated along an altitudinal gradient

We explored the fine-scale distribution of cytotypes of the mountain plant Senecio carniolicus along an altitudinal transect in the Eastern Alps. Cytotypes showed a statistically significant altitudinal segregation with diploids exclusively found in the upper part of the transect, whereas diploids and hexaploids co-occurred in the lower range. Analysis of accompanying plant assemblages revealed significant differences between cytotypes along the entire transect but not within the lower part only, where both cytotypes co-occur. This suggests the presence of ecological differentiation between cytotypes with the diploid possessing the broader ecological niche. No tetraploids were detected, indicating the presence of strong crossing barriers. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Leaf wettability decreases along an extreme altitudinal gradient

The duration and amount of water captured on leaves and its functional significance is highly varied. Leaf surface wettability influences water absorption, gas exchange, pathogen infection, nutrient leaching, contamination by pollutants, self-cleaning properties and in freezing environments the probability of extrinsic ice nucleation. To test the impact of environment on the development of leaf wettability, this functional trait was measured in 227 dominant plant species along an extreme altitudinal environment gradient (186–5,268 m) on the wet and dry slopes of the Nepalese Himalayas. Plants from the understorey and open places in woodlands were also compared. Leaf wettability was assessed by droplet contact angle (θ), retention and leaf inclination measurement. With increasing altitude leaf wettability decreased significantly parallel to the observed atmospheric temperature decrease (0.5 K/100 m). Leaves from non-freezing tropical and subtropical origins were highly wettable (θ < 90°). Temperate leaves were non-wettable (110° < θ < 130°). Subalpine and alpine leaves were highly non-wettable (130° < θ < 150°) and adaxial pubescence occurred more frequently. Leaves taken from the understorey were more wettable but had a better droplet run off than leaves sampled in open places. In the semi-arid northern slopes (temperate to alpine) of the Himalayas leaf wettability was decreased in comparison to the southern humid side. The majority of the leaves had a low droplet retention <20°; higher values were linked to high non-wettability (θ > 130°) which was more often observed at high altitude. Good droplet run off at ±10° inclination was found in highly wettable leaves (θ < 90°) of tropical and subtropical origin and on leaves from the forest understorey. Structural properties for low wettability are developed in cold and dry environments and open sites with frequent dew formation as it appears to be an important functional trait to prevent a number of the negative effects adhering surface water may have.     

The relative contribution of symbiotic N2 fixation and other nitrogen sources to grassland ecosystems along an altitudinal gradient in the Alps

The significance of symbiotic N₂ fixation in legumes (Trifolium alpinum L., T. nivale Sieber, T. pratense L., T. badium Schreber, T. thalii Vill., T. repens L., Lotus alpinus [DC.] Schleicher, L. corniculatus L., Vicia sativa L.) and other N sources for the N budget of grassland ecosystems was studied along an altitudinal gradient in the Swiss Alps. The total annual symbiotic N₂ fixation was compared with other sources of N for plant growth of the total plant community (mineralisation and wet deposition). The contribution of symbiotically fixed N to total above-ground N yield of the swards decreased from at least 16% to 9% with increasing altitude where legumes were present. This decrease was due to a decrease in the yield proportion of legumes from 15% at 900 and 1380 m a.s.l. to 5% at 2100 and 2300 m a.s.l. (no legumes were found above 2750 m a.s.l.) and not to a decline in the activity of symbiotic N₂ fixation. With increasing altitude legumes are more patchily distributed. The high symbiotic N₂ fixation of individual plants up to their altitudinal limit is not primarily the result of low mineral N availability since an addition of NH₄ ⁺ or NO₃ ⁻ fertiliser at 2300 m a.s.l. led either to no decrease or only to a minor decrease in symbiotic N₂ fixation. At 1380 m a.s.l., N mineralisation (13.45 g N m⁻² yr⁻¹) appeared to be the main source of N for growth of the sward; N from symbiosis (at least 1.0 g to 2.6 g N m⁻² yr⁻¹) and wet deposition (0.4 g to 0.6 g m⁻² yr⁻¹) was not a significant N source for plant growth at this altitude. At 2100 m a.s.l., the combined amounts of N from symbiotic N₂ fixation (at least 0.1 g N m⁻² yr⁻¹) and wet deposition (0.3 g N m⁻² yr⁻¹) appeared to be similarly important for plant growth as soil N mineralisation (0.47 g N m⁻² yr⁻¹). At high altitudes, wet N deposition and symbiotic N₂ fixation together represent a significant source of N for the grassland ecosystem while at low altitudes these N inputs appear to be much less important. This revised version was published online in June 2006 with corrections to the Cover Date.     

Freezing tolerance in grasses along an altitudinal gradient in the Venezuelan Andes

The tropical high Andes experience greater daily temperature oscillations compared to seasonal ones as well as a high frequency of night frost occurrence year round. Survival of organisms, under such environmental conditions, has been determined by selective forces which have evolved into adaptations including avoidance or tolerance to freezing. These adaptations have been studied in different species of trees, shrubs and perennial herbs in páramo ecosystems, while they have not been considered in grasses, an important family of the páramo. In order to understand survival of Poaceae, resistance mechanisms were determined. The study was performed along an altitudinal gradient (2,500–4,200 m a.s.l.) in the páramo. Supercooling capacity and frost injury temperature were determined in nine species in order to establish cold resistance mechanisms. Grasses registered a very low supercooling capacity along the altitudinal gradient, with ice formation between −6 and −3°C. On the other hand, frost injury temperature oscillated between −18 and −7°C. Our results suggest that grasses exhibit freezing tolerance as their main cold resistance mechanism. Since grasses grow at ground level, where greatest heat loss takes place, tolerance may be related to this life form as reported for other small life forms.     

Butterfly diversity and historical land cover change along an altitudinal gradient

Land cover and climate change are both major threats for biodiversity. In mountain ecosystems species have to adapt to fragmented habitats and harsh environmental conditions but so far, altitudinal effects in combination with land cover change have been rarely studied. The objective of this study was to determine the effects of altitude and historical land cover change on butterfly diversity. We studied species richness patterns of butterflies occuring in wetlands and other open habitats along an altitudinal gradient in a low mountain region (340–750 m a.s.l., Bavaria, Germany) with drastic loss of open habitats within the last 40–60 years. We recorded in 27 sites a total of 4,523 individuals of 49 butterfly species and five species of burnet moths. Species richness peaked at mid elevation and increased with patch size. Land cover change was most pronounced at high altitudes, but neither current open habitats, nor the historical loss of open habitats affected the species richness of butterflies. Neither open land specialized butterflies nor generalist and forest species were significantly affected by the loss of open habitats. However, increasing forest area in high altitudes reduces possible refuge open habitats for butterflies at their thermal distribution limits. This could lead to extinction of such butterfly species when temperatures further rise due to global warming.     

Stable isotopes as indicators of altitudinal distributions and movements in an Ecuadorean hummingbird community

Altitudinal migration and dispersal is an important component of the life history of several temperate and tropical birds but remains poorly understood due to the limited success of mark and recapture techniques. Stable isotopes of hydrogen (deltaD) in rainfall, and to a lesser extent, carbon (delta13C) in plants are known to change with altitude and hence may provide the basis of a technique for tracking the altitudinal movements in birds and other wildlife. We investigated the potential for this technique by measuring delta13C, deltaD, and delta15N values in tail feathers of eight species of hummingbirds ( Phaethornis malaris, P. syrmatophorus, P. guy, Adelomyia melanogenys, Coeligena torquata, C. lutetiae, Metallura baroni, M. williami) along an altitudinal gradient (300-3,290 m asl) in the Andes Mountains of Ecuador. Feather delta13C and deltaD values were correlated and each changed significantly with elevation above 400 m. In general, we found good agreement between feather deltaD values and those predicted from a generalized relationship of precipitation and surface water deltaD with altitude. Similarly, feather delta13C values showed an enrichment of approximately 1.5 per thousand per 1,000 m over the linear portion of the elevational response. Stable-nitrogen isotope values were variable, and so did not provide useful information on elevation in birds, apart from trophic effects. Overall there appears to be good potential for using the (deltaD, delta13C) stable isotope approach to track altitudinal movements and to elucidate previously unrecognized patterns of life history variation in both temperate and tropical species that migrate across elevational isotopic gradients.     

Phylogenetic beta diversity in an upper montane Atlantic Forest along an altitudinal gradient

Plant Ecology - Studying community phylogenies along elevation gradients can inform us about the influences of environmental conditions on the structuring communities, and therefore allow...     

Environmental drivers of aquatic macrophyte assemblages in ponds along an altitudinal gradient

The aim of this study was to explore the environmental drivers of the aquatic macrophyte assemblage in a large, heterogeneous Spanish region covering a wide altitudinal range. We hypothesized that physicochemical variables affecting assemblages would differ depending on altitude. The study was conducted in 46 plateau ponds and 21 mountain ponds. Our results revealed a shift in hydrophyte assemblage composition and structure along an altitude and water chemistry gradient. However, altitude was not a good predictor of species richness. Conductivity and nutrient concentrations were higher in plateau ponds than in mountain ponds and binary logistic regression showed that conductivity was the best variable for differentiating between both pond types. Canonical correspondence analysis indicated that conductivity was the main factor responsible for the species distribution in both pond types. Generalized linear models showed that in plateau ponds, total phosphorus and mean depth were the strongest predictors of submerged macrophyte coverage, and no model could be created for richness. In the mountain ponds, conductivity and pond area explained coverage of submerged plants, while richness was related to pond area. Our results corroborated the hypothesis to be tested, and the conclusions obtained may be of relevance for making decisions on conservation and restoration.     

Cold hardiness and supercooling along an altitudinal gradient in andean giant rosette species

Summary Factors affecting supercooling capacity and cold hardiness were investigated in leaves of ten giant rosette species of the genus Espeletia (Compositae). These species grow along a 2,800–4,200 m elevation gradient in the Venezuelan Andes. In this high tropical environment, freezing frequently occurs every night, particularly above 3,300 m, but lasts for only a few hours. Supercooling capacty is linearly related to leaf water potential ( _L ) in all species; however supercooling is more responsive to _L changes in Espeletia species from high paramos. The rate of change in the species-specific supercooling point and the rate of change of average annual minimum temperature along the elevation and climatic gradient follow the same trend (approximately -0.6 K per 100 m elevation). At a given elevation, the expanded leaves of the different species tend to supercool 8–10 K below minimum air temperatures. Experimentally-induced freezing was accompanied by the formation of intracellular ice and tissue damage. The relative apoplastic water content (RAWC) of the leaves, which may influence the ice nucleation rate or the facility by which ice propagates, was determined by pressure-volume methods. Species from higher sites tend to exhibit lower RAWC (2%–7%) than species from lower sites (7%–36%). A causal relationship between supercooling capacity and RAWC is suggested. In the high tropical Andes, the temperature oxotherm plateau of Espeletia leaves seems to be sufficiently fow to avoid freezing.     

白龙江林区地表甲虫沿海拔梯度的群落结构及动态分析

【目的】揭示白龙江林区地表甲虫群落沿海拔梯度（927-2 735 m）的多样性格局、群落结构及动态变化,为林区内生物多样性长期监测及保护提供理论基础和依据。【方法】采用巴氏罐诱捕法,沿不同海拔梯度（927、1 794、2 376和2 735 m）设置陷阱诱集地表甲虫。【结果】共采集2 015头地表甲虫,包括18科95种。虎甲科Cicindelidae的个体数量最多（436只）占总数的21.6%,其次是叩甲科Elateridae、步甲科Carabidae、葬甲科Silphidae、隐翅甲科Staphylinidae。5个科的采集数量占到总数的75.1%,是白龙江地区优势种群。随着海拔梯度的升高,流域内地表甲虫的数量及优势种群数量都呈先上升后下降的趋势。在海拔2 376 m处,地表甲虫丰富度最高,诱集数量最多。低海拔地区地表甲虫丰富度低,诱集数量少。在种群动态变化中,中高海拔地区的优势种群在6-9月间的种群数量变化趋势呈单峰增长模式,且不同海拔高度不同科种群的诱集峰值不同。如在不同海拔梯度内诱集的步甲科数量均在7月份最多;在海拔2 376 m处,叩甲科个体数量在8月份最多,相比海拔较低的1 794 m处,则7月份数量最多,在低海拔927 m处和高海拔地区2 735 m处,叩甲科的个体数量急剧减少,且动态变化不明显。【结论】在白龙江林区拱坝河流域,地表甲虫种类丰富,优势种群明显。在不同海拔梯度上,其优势种群表现出不同的变化模式。根据地表甲虫群落在海拔梯度上的分布,可将地表甲虫分为三类。一是分布在中高海拔,包括步甲科、隐翅甲科及虎甲科等,在流域内4个不同海拔梯度都有分布。二是在中高海拔和高海拔处种类丰富,在低海拔处未诱集到相应甲虫,包括叩甲科及葬甲科。三是在不同海拔高度都有分布,但数量少,未形成优势种群,包括金龟科、象甲科及瓢虫科等。     

Species richness and trait composition of butterfly assemblages change along an altitudinal gradient

Species richness patterns along altitudinal gradients are well-documented ecological phenomena, yet very little data are available on how environmental filtering processes influence the composition and traits of butterfly assemblages at high altitudes. We have studied the diversity patterns of butterfly species at 34 sites along an altitudinal gradient ranging from 600 to 2,000 m a.s.l. in the National Park Berchtesgaden (Germany) and analysed traits of butterfly assemblages associated with dispersal capacity, reproductive strategies and developmental time from lowlands to highlands, including phylogenetic analyses. We found a linear decline in butterfly species richness along the altitudinal gradient, but the phylogenetic relatedness of the butterfly assemblages did not increase with altitude. Compared to butterfly assemblages at lower altitudes, those at higher altitudes were composed of species with larger wings (on average 9 %) which laid an average of 68 % more eggs. In contrast, egg maturation time in butterfly assemblages decreased by about 22 % along the altitudinal gradient. Further, butterfly assemblages at higher altitudes were increasingly dominated by less widespread species. Based on our abundance data, but not on data in the literature, population density increased with altitude, suggesting a reversed density–distribution relationship, with higher population densities of habitat specialists in harsh environments. In conclusion, our data provide evidence for significant shifts in the composition of butterfly assemblages and for the dominance of different traits along the altitudinal gradient. In our study, these changes were mainly driven by environmental factors, whereas phylogenetic filtering played a minor role along the studied altitudinal range.     

阿尔卑斯山黄花茅(Anthoxanthum alpinum)沿海拔梯度的基因频率分布

在瑞士阿尔卑斯山的2个定点样地,黄花茅从森林线（海拔1700 m）到山顶（海拔2830 m）呈连续分布。在海拔梯度样带的最高和最低定样场所间的垂直距离差不多为1000 m,但2个定样场所间相距仅仅1.4 km。在所研究的3个海拔梯度样带中,3个同工酶位点（Px_1, Got_2和 Mdh_1）被观察到有统计意义的倾群变异。研究结果显示：沿海拔梯度样带的亚居群间的基因流可能太弱不足以克服自然选择的影响,后者促使对局部环境的适应。在这种情况下,温度因子至少可能作为一种主要的自然选择力起作用。     

Developmental time and size-related traits in Drosophila buzzatii along an altitudinal gradient from Argentina

Clinal analysis for fitness-related traits provides a well-known approach to investigate adaptive evolution. Several fitness-related traits (developmental time, thorax length, wing length and wing loading) were measured at two laboratory generations (G7 and G33) of D. buzzatii from an altitudinal gradient from northwestern Argentina, where significant thermal differences persist. Developmental time (DT) was positively correlated with altitude of origin of population. Further, DT was negatively correlated with maximal mean temperature at the site of origin of population, and this thermal variable decreases with altitude. Wing loading tended to be larger in highland than in lowland populations, suggesting that flight performance is subject to stronger selection pressure in highland populations. Developmental time showed a significant increase with laboratory generation number. There was no significant correlation between developmental time and body size across populations along the altitudinal cline of DT. This result illustrates that developmental time and body size do not always evolve in the same direction, even though both traits are often positively and genetically correlated in a well-known tradeoff in Drosophila.     

Littoral benthic macroinvertebrates of alpine lakes (Tatra Mts) along an altitudinal gradient: a basis for climate change assessment

Littoral benthic macroinvertebrates were studied in three alpine lakes in the High Tatra Mountains (Slovakia) located at different elevations: 2157, 1940 (alpine zone) and 1725 m (sub-alpine zone). The study sites were selected in order to obtain a gradient in thermal regimes and particular organic matter (POM). Differences in the faunal composition of lakes were tested for the ability of these differences to indicate climatic changes, and species/taxa were identified that could be used for the purposes of monitoring and climate change assessment. Macroinvertebrates were sampled quantitatively during the ice-free seasons of 2000 and 2001, and lake surface water temperature (LSWT) and POM were measured. LSWT and POM were negatively correlated with elevation, whereas ice cover was positively correlated with elevation. A total of 60 oligostenothermic macroinvertebrate species/taxa were collected belonging to ten higher taxonomic groups. Statistical analysis showed trends in several biotic metrics with altitude. More specifically, there was a clear increase in the number of species/taxa, genera, and higher taxonomic groups, as well as an increase in the Shannon–Wiener diversity with decreasing altitude. On the contrary, evenness and density of benthic macroinvertebrates did not show any clear relationship with altitude. Gatherers of detrital particles dominated the assemblages’ trophic structures, but no distinct changes in the proportion of functional feeding groups along the altitudinal gradient were found. While the non-insect fauna of the lakes was rather uniform across the elevational gradient, the insect fauna composition was highly correlated with altitude, as confirmed by Detrended Correspondence Analysis. Aquatic insects, in particular chironomids and caddisflies, can therefore be used as good indicators of temperature changes. Our results suggest that under warmer conditions, non-insect benthic macroinvertebrates will remain more or less stable, while aquatic insects will undergo an increase in the number of thermophilic species typical for lower altitudes. These colonizers will increase the diversity of alpine lakes, while the extinction of cold stenothermal species will lead to impoverishment of the native fauna. An indirect impact on benthic macroinvertebrates through changes in food sources is likely, and changes in trophic structure of the littoral assemblages can be expected.     

Morphological variation in the Common Fiscal Lanius collaris along an altitudinal gradient in southern Africa

Geographic variation among four Common Fiscal subpopulations along an altitudinal gradient in South Africa demonstrated significant variation of 13 morphological features and 38 skeletal characters. Common Fiscals were largest in cooler, less humid, more arid areas and smallest in warmer, wetter, more humid localities, supporting Bergmann's Rule. Patterns of variation in morphology, anatomy and skeletal trends were significantly correlated with 11 climatic trends. Cardiopulmonary organ mass and blood haematocrit increased with altitude and reflected adaptations to low ambient temperatures and decreased oxygen pressures associated with high altitudes. These trends are concordant with those reported in various other avian species.