Alpine Botany最新文献

Graminoids are typically the dominant plants in certain grassland communities, and their clonal growth is considered an important method of evaluating their adaptation to environmental disturbances. Whether disturbances caused by small burrowing herbivores influence clonal growth in graminoids is not well documented. A field experiment was conducted to investigate the effects of disturbances by small burrowing herbivores, the plateau pika, on the clonal growth of the tussock-forming Kobresia pygmaea and the rhizomatous K. humilis across three sites. This study showed that disturbance by plateau pikas increased the shoot number, spacer number and tiller bud number per clonal fragment of both the tussock-forming K. pygmaea and the rhizomatous K. humilis across three sites. This study also showed that disturbance by plateau pikas increased the rhizome branch number, rhizome length, and rhizome bud number per clonal fragment of rhizomatous K. humilis at each site, while the effects of disturbance by plateau pikas on the rhizome branch number, rhizome length, and rhizome bud number per clonal fragment of the tussock-forming K. pygmaea were different among the three sites. These results suggested that disturbance by plateau pikas benefits for current and potential population recruitment in the tussock-forming K. pygmaea and the rhizomatous K. humilis due to the resulting higher shoot number and tiller bud number per clonal fragment.

In high-mountain habitats, summer frosts have negative consequences for plant fitness, therefore high-mountain plants have developed mechanisms of avoidance and tolerance to cope with freezing temperatures. Various hypotheses have been proposed to explain the prevalence of one freezing-resistance mechanism over another, focusing on thermal conditions without a consensus. We hypothesize that the prevalence of a freezing-resistance mechanism depends on the life-history strategy of the species, and is probably the consequence of a trade-off between growth/reproduction and the cost of the mechanism. Specifically, short-lived annual species should be freezing avoidant, whereas perennial long-lived species should be freezing tolerant. We used thermal analysis to determine the mechanism of freezing resistance of leaves and flowers for 10 annual and 14 perennial herb species from an alpine ecosystem in the Central Chilean Andes. We found that 70% of the annual species, their flowers and leaves were freezing avoidant, indicating that avoidance was their predominant freezing-resistance mechanism. In the case of perennial species, both mechanisms were almost equally represented in flowers and leaves. Overall, our results showed that a species freezing-resistance mechanism depends on its life-history strategy, and that leaves and flowers of single species exhibit the same freezing resistance mechanism, suggesting a common whole plant strategy. Further, freezing resistance strategies were not found to be mutually exclusive. In some cases, a specific combination of phenological, structural, and functional strategies may determine how freezing resistant vegetative and reproductive organs are to freezing during the growing season.

Climatic oscillations of the Quaternary rapidly compelled plant species to shift their geographical range. How alpine plant species responded to climate change, however, remains elusive and remnants of the cold-adapted flora that currently strive in restricted ranges as small, isolated populations have been particularly overlooked. To address the evolutionary history of such a ‘glacial relict’, we here sampled and genotyped all known native populations of a narrow endemic species from the northwestern Alps, Papaver occidentale, as well as closely related taxa with double digest restriction-site Associated DNA (ddRAD) sequencing. Spatial patterns of genetic variation across populations coupled with insights from climatic niche modelling through time address underpinings of the long-term persistence of the species in face of climate changes. Evidence from population genetics and ecological modelling indicates that P. occidentale likely persisted through the last glacial maximum outside of the Western Prealps and that a major lineage recolonized the area from lower elevation, external regions. Differentiated lineages at the Northern margins of the species distribution range highlight highly divergent and geographically restricted populations that include considerable share of private markers and may indicate local glacial survival in isolated conditions. Our data thus imply that processes having shaped intraspecific spatial genetic structure within the Alps can be complex and lead to mosaic of populations with a mixed-history of local survival and immigration. A better understanding of spatio-temporal aspects of range contraction–expansion is crucial to shed light on processes underlying the evolution of remnant populations of such endemic species and set conservation priorities considering current climate changes.

In contrast to adult plants, little is known about the frost-tolerance of seedlings of alpine species, despite the fact that frost has been considered as one of the main factors limiting plant recruitment in high elevation. Here we report the results of a comparative study on seedling frost-tolerance of nine congeneric species pairs with lowland (0–900 m a.s.l.) and alpine (1800–2700 m a.s.l.) distribution. Similarly to adult alpine plants, we expected seedlings of alpine species to be more frost-tolerant than their lowland counterparts. Frost-tolerance was estimated under laboratory conditions by exposing seedlings to frost events from − 1 to − 9 °C, calculated as the temperature at which 50% of the seedlings were lethally damaged by frost (LT₅₀). The LT₅₀ values varied between − 1.95 and − 6.11 °C suggesting that seedling of all tested species could potentially survive mild and/or short frosts, but might be lethally damaged by severe and/or continuous frost events. The LT₅₀ values for lowland and alpine species did not differ statistically and were on average − 3.96 ± 0.18 °C and − 4.16 ± 0.43 °C, respectively. These findings did not confirm our hypothesis that seedlings of alpine species have higher frost-tolerance than seedlings of lowland species. Four possible reasons could explain this pattern. They include (1) comparable levels of negative-stress in both lowland and alpine habitats, (2) opportunistic seed germination strategy in alpine plants, (3) peculiarities of our experimental set up and (4) potentially stronger effects of drought on alpine seedling survival than frost.

In high-mountain habitats, summer frost events can have negative consequences for plant fitness. Despite this, most studies have evaluated the consequences of frosts for vegetative structures of perennial plants, and neither for leaves nor for flowers of annual plants. We hypothesize that the degree of freezing resistance of flowers and leaves of a species depends on its life-history strategy (LHS), and is probably the consequence of a trade-off between growth/reproduction and the cost of the freezing resistance. Specifically, flowers and leaves of short-lived annual species should be less freezing resistant than those of perennial plant species. We compared the freezing resistance of flowers and leaves of 10 annual and 12 perennial plant species from the Andes of central Chile using the electrolyte leakage method. Temperature damage for 50% tissue (LT₅₀) of annual species was − 9.6 °C in flowers and − 11.9 °C in leaves. In perennial species, LT₅₀ was similar in flowers (− 12.3 °C) and leaves (− 12.5 °C). Despite that, these differences were not significant (except the flowers of annual species), we found remarkable differences between LHS when freezing resistance was analyzed species by species. Like this, 58% and 83% of perennial species resist temperatures ≤ − 10 °C in their flowers and leaves, respectively, compared with only 30% and 40% of annual species. Additionally, in most of the species, the freezing resistance of leaves was greater than that of flowers, with this proportion being greater in annual (58%) than in perennial species (43%). Thus, we concluded that the degree of freezing resistance depends on the LHS, such that annual species, which are less freezing resistant than perennial species, have an infrequent occurrence and a distribution restricted to low elevation in high-mountain habitats.

Conceptual models of how interactions with native species influence invasions emphasize competition, but recent evidence suggests facilitation can promote invasion in stressful environments. However, how nurse-plants with contrasting growth-forms and distribution interact with invaders remains unexplored, although it could offer insights on nurse/exotic interaction mechanisms. We asked whether shrub and cushion nurses differed in their effects on the exotic Rumex acetosella in sites at four elevations in the high tropical Andes (4100–4400 m), shrubs dominating the lowest sites and cushions the highest sites. During the dry season, we measured soil organic matter (SOM) and water content (SWC) under the shrub Hypericum laricifolium, the cushion Azorella julianii, and adjacent areas outside. We compared Rumex’s performance under each situation, measuring midday leaf temperatures (T_leaf), vapor pressure deficit (VPD), minimum water potentials (Ψ_min) and leaf nitrogen (N_leaf) and compared the number, size and proportion of fruiting ramets within sampling rings in each situation. SOM and SWC were higher at all elevations under cushions, then under shrubs and lower outside. Rumex’s density was generally reduced under shrubs but increased on cushions. However, both nurses had positive effects along the gradient on Rumex’s size, reproduction, water balance and N_leaf, shrubs having stronger effects on T_leaf and VPD and cushions on N_leaf. Our results indicate that alternating nurses influenced an invader’s physiological performance to different extents via contrasting effects on shading and soil resources, leading to mixed competitive/facilitative effects of shrubs on the exotic’s demography, while cushions had more consistent facilitative effects across elevations.

Ecological interactions play a fundamental role in determining the genetic structure of plant species in time and space. The demography of the Andean Puya hamata has been linked to fire regimes and hummingbird behaviour, which might modify the plant’s population genetic structure. Naturally, poor dispersal results in patches of genetically related plants, a pattern intensified further by burning which promotes seedling germination around parent plants. Later, when these plants flower, large patches are attractive to territorial hummingbirds which prevent visits by traplining hummingbird species, carrying pollen from likely unrelated plants. To explore this hypothesis, a genetic study of P. hamata using microsatellite markers was conducted with (i) isolated and grouped adults in two size categories of patches, and (ii) seeds collected from the same patches and isolated individuals. Isolated individual plants presented a higher observed heterozygosity with close to zero inbreeding. Adult plants from large patches showed a lower observed heterozygosity and higher inbreeding than plants from other spatial contexts. Seed genetic structure displayed a gradient of diversity: lower at patch centres but higher at patch edges, in small patches, and for isolated infructescences. The spatial context of these plants, especially the contrast between large patch centres and other situations, determines the genetic diversity of their seeds via hummingbird foraging behaviour. Territorial hummingbirds restrict gene flow in and out of large patches, but traplining hummingbirds maintain genetic diversity among isolated plants, small patches, and plants at the edges of large patches. Our study illustrates the need to consider interactions between land use, plants, and their pollinators when considering genetic diversity at the landscape scale.

Treeline isotherms are used in comparative and modelling studies to predict treeline positions. However, how representative local short-term temperature records are for a given region remains poorly understood. Furthermore, the predictive value of on-site temperatures for explaining tree growth requires further validation. Here we present temperature records and tree growth datasets from treeline ecotone sites differing in elevation and slope direction in the High Sudetes (Czechia and Poland). The goal was to determine the spatial and temporal variability of soil and air temperatures and to describe the relationship of various temperature metrics with tree growth. Our results demonstrate that, because of spatial and temporal variability, major temperature metrics used in comparative studies should be provided with an uncertainty range between 0.6 and 0.8 K for seasonal mean soil and air temperature. While soil temperatures exhibit high spatial variability, air temperatures vary more with time. Elevation is the most important driver of temperature patterns in treeline ecotones. Differences related to slope direction were important mainly for soil temperatures in lower parts of treeline ecotones. Tree growth is tightly related to June–September air temperature, with a modulating role of the onset date of soil temperature-defined growing season. In this study, we describe patterns of temperature variation in the treeline ecotones of two mountain ranges and demonstrate the extremely strong dependence of tree stem growth on air temperature, with very limited remaining space for other potentially limiting factors.

The Alps played an important role in the biogeography of European plants and acted as a refugium for numerous species during the interglacial cycles. We investigated Nuphar pumila, one of the most emblematic glacial relicts of the Alps, by carrying out exhaustive literature and field surveys to collect relevant data on its distribution and threats. We further evaluated the level of introgression with the closely related N. lutea based on microsatellite data from natural populations across the Alps as well as from all ex situ collections and reintroductions in Switzerland. According to our results, more than 60% of the known N. pumila populations went extinct, and the species currently presents 37 natural populations in the investigated area. A large number of populations were affected by eutrophication (69%) and hybridization with N. lutea (53%). Priority should be given to the in situ conservation of genetically pure populations, while ex situ cultures should be applied to nearly extinct populations and the genetically pure individuals still present in hybrid populations. N. pumila is an excellent representative of the wetland/aquatic glacial relicts that are particularly affected by the combination of climate change and habitat degradation. International integration of research and conservation programs is needed to limit the decline of such rare species in the Alps.

Patterns of flowering phenology, i.e. first and last flowering day (FFD and LFD) and flowering duration (FD) govern plant pollination and reproduction. Most research has focused on FFD whereas LFD, FD and second flowering events were neglected although they are crucial events. To assess whether flowering patterns change species-specifically with changing abiotic conditions and whether these are related to leaf persistence, reproduction and pollination syndrome, we monitored flowering phenology (including also second flowering events) of 29 herbaceous species along two elevational gradients ranging from 700 to 1800 m a.s.l. in two consecutive years. FFD was delayed with increasing elevation. LFD followed two alternative strategies: species which ceased flowering early in the season delayed LFD with increasing elevation, species which ceased flowering late did not change LFD. FD decreased with increasing elevation in most species. The timing of flowering phenology had strong influences on the intensity of change along the elevational gradient and other stages of flowering phenology. Many species showed a second flowering event which occurred irrespective of elevation, suggesting a link to unsuccessful pollination rather than temperature. Life history strategies helped explain patterns of flowering phenology and a species’ ability to track changes in abiotic conditions, e.g. evergreen species started to flower earlier than summer green species and insect-pollinated species were able to expand FD most. These findings give insight into species-specific changes in phenological patterns and thus plant performance with changing environment. They should be considered when assessing the consequences of environmental change at both the community and ecosystem level.