Search

Snow is an important driver of ecosystem processes in cold biomes. Snow accumulation determines ground temperature, light conditions, and moisture availability during winter. It also affects the growing season’s start and end, and plant access to moisture and nutrients. Here, we review the current knowledge of the snow cover’s role for vegetation, plant-animal interactions, permafrost conditions, microbial processes, and biogeochemical cycling. We also compare studies of natural snow gradients with snow experimental manipulation studies to assess time scale difference of these approaches. The number of tundra snow studies has increased considerably in recent years, yet we still lack a comprehensive overview of how altered snow conditions will affect these ecosystems. Specifically, we found a mismatch in the timing of snowmelt when comparing studies of natural snow gradients with snow manipulations. We found that snowmelt timing achieved by snow addition and snow removal manipulations (average 7.9 days advance and 5.5 days delay, respectively) were substantially lower than the temporal variation over natural spatial gradients within a given year (mean range 56 days) or among years (mean range 32 days). Differences between snow study approaches need to be accounted for when projecting snow dynamics and their impact on ecosystems in future climates.

Global climate and land use change are causing woody plant encroachment in arctic, alpine, and arid/semi-arid ecosystems around the world, yet our understanding of the belowground impacts of this phenomenon is limited. We conducted a globally distributed field study of 13 alpine sites across four continents undergoing woody plant encroachment and sampled soils from both woody encroached and nearby herbaceous plant community types. We found that woody plant encroachment influenced soil microbial richness and community composition across sites based on multiple factors including woody plant traits, site level climate, and abiotic soil conditions. In particular, root symbiont type was a key determinant of belowground effects, as Nitrogen-fixing woody plants had higher soil fungal richness, while Ecto/Ericoid mycorrhizal species had higher soil bacterial richness and symbiont types had distinct soil microbial community composition. Woody plant leaf traits indirectly influenced soil microbes through their impact on soil abiotic conditions, primarily soil pH and C:N ratios. Finally, site-level climate affected the overall magnitude and direction of woody plant influence, as soil fungal and bacterial richness were either higher or lower in woody encroached versus herbaceous soils depending on mean annual temperature and precipitation. All together, these results document global impacts of woody plant encroachment on soil microbial communities, but highlight that multiple biotic and abiotic pathways must be considered to scale up globally from site- and species-level patterns. Considering both the aboveground and belowground effects of woody encroachment will be critical to predict future changes in alpine ecosystem structure and function and subsequent feedbacks to the global climate system.

Plant reproduction is often inhibited by herbivorous leaf damage, which affects the resource pool allocated for reproduction. Rhododendron kaempferi var. kaempferi is a semi‐evergreen shrub widely distributed in Japan, and its leaves are occasionally damaged by sawfly larvae (Arge similis). This species is partially self‐compatible, but its selfed seedlings suffer from inbreeding depression. Our study aimed to clarify (1) the magnitude of herbivorous damage under natural conditions, (2) the effects of foliage damage on seed number and mass, and (3) the possibility of selective abortion of selfed seeds to maintain outcrossed seed production under resource limitation. In the 2022 survey, 2 of the 20 ramets observed were collectively parasitized by sawfly larvae, and the most damaged ramet had a 59.6% foliage loss. In contrast, the herbivorous damage in 2023 was consistently low throughout the growing season, averaging a 3.2% loss. Leaf excision reduced the seed number per fruit (i.e., low seed‐set rate) but did not affect the individual seed mass. The outcrossing rate of the excision treatment (81.7%) was significantly higher than that of the control (72.0%). The values of seed‐set rate × outcrossing rate were 0.172 for the excision treatment and 0.171 for the control, nearly equal. Our results indicated that (1) sawfly larvae damage was concentrated on a few specific plants, (2) intense foliage damage reduced seed number but not seed mass, and (3) R. kaempferi mitigated the decline in outcrossed seed production by the abortion of selfed seeds when leaves were intensively damaged. [ABSTRACT FROM AUTHOR]

Pollination success of alpine plants is often restricted by low and unpredictable pollinator activity because of harsh and unstable weather conditions, where nocturnal pollination is rare. The alpine orchid, Platanthera tipuloides (Orchidaceae), has inconspicuous greenish yellow flowers with a sweet scent and a long spur that contains nectar. These floral traits are expected to be related to nocturnal moth pollination. To elucidate the pollination mode and reproductive characteristics of this species, we measured floral traits (spur length, nectar content in the spur, floral scent), documented flower visitors using camera traps, and quantified self‐compatibility and the degree of pollen limitation through controlled pollinations at two study plots in the Taisetsu Mountains, northern Japan. It was revealed that P. tipuloides is self‐incompatible and pollen limitation was absent at one of the study plots. The flowers emitted more volatile substances during the night, including lilac aldehyde isomers, which are known to attract moths. A nocturnal moth, Entephria amplicosta, was observed foraging nectar from the flowers, while no diurnal visitors were observed. The proboscis of E. amplicosta was shorter than the spur length, but it was long enough to access the accumulated nectar in the spurs. These results suggest that nocturnal pollination by moths is possible and can be efficient even in an alpine ecosystem with harsh environmental conditions. [ABSTRACT FROM AUTHOR]

The great majority of studies on foundation species focused on a single dominant plant in a community, while more than one such species can often coexist and compete for space and limited resources. Morphologically different coexisting foundation species can create diverse niches occupied by different subsets of beneficiary species. To test this hypothesis, we sampled alpine plant communities at exposed fellfields in alpine zone, in the Taisetsu Mountains (Hokkaido, northern Japan), with coexisting putative foundation species Pinus pumila (evergreen shrub) and Diapensia lapponica (evergreen cushion‐forming shrub), and analyzed their spatial relationships with other plants. Preliminary vegetation survey indicated that fruticose lichens and Loiseleuria procumbens (evergreen mat‐forming shrub) might also act as a foundation species; thus, we included them in our analyses. The coexisting foundation species had both general as well as specific effects on plant community structure. Namely, almost all the members of the community aggregated spatially with lichens, while the other foundation species were spatially segregated from each other. These foundation plants associated with different members of the community, thus showing species‐specific effects on the community structure. Blooming species showed even stronger patterns of species‐specific spatial associations, suggesting that foundation species had beneficial effects on their associated species. We conclude that the focus on coexisting foundation species can reveal important details of community structure which would be hidden if we treated all species as equal members of the community. Studying the effects of coexisting foundation species could greatly advance our understanding of how species diversity functions in plant communities. [ABSTRACT FROM AUTHOR]

Phenological responses of plants to temperature dynamics are receiving attention due to the ongoing challenge with climate change. Most previous phenological studies have focused on flowering phenology rather than fruiting phenology. However, at mid-latitudes, the air temperature periodically changes during the growing period of plants. Hence, cool temperatures early and late in the growing period may affect reproductive success through pollination and fruit-development processes. To evaluate the linkages between reproductive phenology and success, we compared the phenologies, photosynthetic capacities, and fruit-set rates among 25 species within a cooltemperate community in northern Japan. The ambient temperature during the flowering periods of individual species increased with delays in flowering-onset time, whereas the ambient temperature during fruit-development periods was highest for species which bloomed in July. Fruit-set success among species was positively correlated with the ambient temperatures during the reproductive periods and with the photosynthetic capacity. Fruit production of early blooming species was limited by cool temperatures during the flowering period, presumably because of low pollinator activity, whereas that of late-blooming species was limited by cool temperatures during the fruit-development period because of slow fruit-development (i.e., sink limitation). Thus, limiting factors of fruit production varied depending on the flowering phenology of individual species within a community. Key words: air temperature, pollen limitation, pollinator, seasonality, sink limitation. Les réponses phénologiques des plantes à la dynamique de la température font l'objet d'une attention particulière en raison des changements climatiques en cours. La plupart des études phénologiques précédentes se sont concentrées sur la phénologie de la floraison plutôt que sur la phénologie de la fructification. Toutefois, aux latitudes moyennes, la température de l'air change périodiquement pendant la période de croissance des plantes. Par conséquent, des températures fraîches au début et à la fin de la période de croissance peuvent affecter le succès de la reproduction à travers les processus de pollinisation et de développement des fruits. Afin d'évaluer les liens entre la phénologie et le succès de la reproduction, les auteurs ont comparé les phénologies, les capacités photosynthétiques et les taux de fructification de 25 espèces à l'intérieur d'une communauté tempérée froide du nord du Japon. La température ambiante pendant les périodes de floraison des espèces individuelles augmentait avec le retard de l'apparition de la floraison, tandis que la température ambiante pendant les périodes de développement des fruits était la plus élevée pour les espèces qui fleurissaient en juillet. Le succès de la fructification des différentes espèces était positivement corrélé avec les températures ambiantes pendant les périodes de reproduction et avec la capacité photosynthétique. La production de fruits des espèces à floraison précoce était limitée par les températures fraîches pendant la période de floraison, probablement en raison de la faible activité des pollinisateurs, tandis que celle des espèces à floraison tardive était limitée par les températures fraîches pendant la période de développement des fruits en raison de la lenteur du développement des fruits (c'est-à-dire la limitation du puits). Ainsi, les facteurs limitants de la production de fruits varient en fonction de la phénologie de floraison des espèces individuelles au sein d'une communauté. [Traduit par la Rédaction] Mots-clés : température de l'air, limitation du pollen, pollinisateur, saisonnalité, limitation du puits., Introduction When should plants bloom and develop fruits? This issue is critical for plants to adapt to local abiotic and biotic environments, and it is one of their most important [...]

Premise: Mast flowering/seeding is often more extreme in lower‐resource environments, such as alpine compared to lowland habitats. We studied a masting herb that had less extreme masting at higher elevations, and tested if this difference could be explained by higher photosynthetic productivity and/or lower reproductive investment at the higher‐elevation sites. Methods: We examined the relationship between flowering intervals and carbon budget (i.e., the balance between reproductive investment and annual carbon fixation) in a masting herb, Veratrum album subsp. oxysepalum, across five lowland and six alpine populations in northern Japan. We evaluated the previous flowering histories of individual plants based on rhizome morphology and analyzed the masting patterns of individual populations. Total mass of the reproductive organs, as a proxy of reproductive investment, was compared between the lowland and alpine populations. Annual carbon fixation was estimated on the basis of photosynthetic capacity, total leaf area per plant, and seasonal transition of light availability. Results: Interval between high‐flowering years was shorter and total reproductive investment was smaller in the alpine than in the lowland populations. Owing to its high photosynthetic capacity and continuous bright conditions, annual carbon fixation per plant was 1.5 times greater in alpine habitat than in lowland habitat. These results suggest that V. album alpine populations have shorter flowering intervals than lowland populations due to faster recovery from energy loss after reproduction. Conclusions: Our study demonstrated that masting intervals in V. album populations can be explained by habitat‐specific carbon budget balances. [ABSTRACT FROM AUTHOR]

Flowering phenology of alpine plant communities and seasonal dynamics of flower visitors have been scarcely studied in the tropical/subtropical alpine regions. We report flowering phenology, flower production, and flower‐visiting insects in an alpine site of central Taiwan. Throughout the research period (2017–2018), we recorded flowering phenology of 130 plant species, flower production of 81 species, and 15,127 insects visiting alpine flowers. Most of the alpine plants were visited by dipteran insects and/or hymenopteran insects. The seasonal patterns of flowering were more apparent in bee‐visited plants compared to fly‐visited plants in which the flowering of bee‐visited plants clearly increased as the season progressed. About 63% of flower visitors were dipteran insects (syrphid and non‐syrphid flies), and 30% were hymenopteran insects (mostly bumble‐bee workers). Although the seasonal trend in fly abundance was less clear between years, bumble‐bee abundance consistently increased in the middle to late seasons, reflecting colony development. There was a positive correlation between bee abundance and the number of flowering species of bee‐visited plants, but there was no correlation between fly abundance and the number of flowering species of fly‐visited plants throughout the season. These results suggest that the flowering phenology of subtropical alpine communities is influenced by the seasonal availability of pollinators. Bumble bees, syrphid flies, and non‐syrphid flies had wide ranges of foraging flowers, but their niche overlap was relatively small. Because cold‐adapted bumble bees are threatened by climate change in Taiwan, plant–pollinator interactions may be disturbed by global warming. [ABSTRACT FROM AUTHOR]