2,512 research outputs found
Terrestrial Ecology in the Arctic; Climate Change Challenges
第3回極域科学シンポジウム/第34回極域生物シンポジウム 11月27日(火) 統計数理研究所 3階セミナー
Botanical Research on Svalbard; Historical Perspective and Future Directions.
第3回極域科学シンポジウム/特別セッション「これからの北極研究」11月28日(水) 国立極地研究所 2階大会議
When spring ephemerals fail to meet pollinators: Mechanism of phenological mismatch and its impact on plant reproduction
The flowering phenology of early-blooming plants is largely determined by snowmelt timing in high-latitude and high-altitude ecosystems. When the synchrony of flowering and pollinator emergence is disturbed by climate change, seed production may be restricted due to insufficient pollination success. We revealed the mechanism of phenological mismatch between a spring ephemeral (Corydalis ambigua) and its pollinator (overwintered bumblebees), and its impact on plant reproduction, based on 19 years of monitoring and a snow removal experiment in a cool-temperate forest in northern Japan. Early snowmelt increased the risk of phenological mismatch under natural conditions. Seed production was limited by pollination success over the 3 years of the pollination experiment and decreased when flowering occurred prior to bee emergence. Similar trends were detected on modification of flowering phenology through snow removal. Following snowmelt, the length of the pre-flowering period strongly depended on the ambient surface temperature, ranging from 4 days (at greater than 7°C) to 26 days (at 2.5°C). Flowering onset was explained with an accumulated surface degree-day model. Bumblebees emerged when soil temperature reached 6°C, which was predictable by an accumulated soil degree-day model, although foraging activity after emergence might depend on air temperature. These results indicate that phenological mismatch tends to occur when snow melts early but subsequent soil warming progresses slowly. Thus, modification of the snowmelt regime could be a major driver disturbing spring phenology in northern ecosystems
Onset of autumn senescence in High Arctic plants shows similar patterns in natural and experimental snow depth gradients
Predicted changes in snow cover and temperature raise uncertainties about how the beginning and the end of the growing season will shift for Arctic plants. Snowmelt timing and temperature are known to affect the timing of bud burst, but their effects on autumn senescence are less clear. To address this, researchers have examined senescence under natural and experimental environmental gradients. However, these approaches address different aspects of plant responses and the extent to which they can be compared is poorly understood. In this study, we show that the effect of snowmelt timing on the timing of autumn senescence in High Arctic plants is the same between a natural and an experimental gradient in three out of four studied species. While the two approaches mostly produce comparable results, they give in combination greater insight into the phenological responses to predicted climate changes. We also showed that a short warming treatment in autumn delayed senescence by 3.5 days in Dryas octopetala L., which is a 10% extension of the growing season end for this species. Warming treatments have commonly been applied to the whole growing season, but here we show that even isolated autumn warming can be sufficient to affect plant senescence.Peer reviewe
Grazing by captive Barnacle geese affects graminoid growth and productivity on Svalbard
Migratory geese breed in Svalbard in summer and return to Western Europe for the winter, feeding on wetlands and agricultural fields. Recent changes in climate, land use and the implementation of protective measures dramatically improved the birds\u27 ability to survive the winter, increasing population sizes and thus the potential grazing impact on Svalbard. This study measured live leaf length and aboveground productivity of Alopecurus borealis and Dupontia fisheri, widespread forage grasses on Svalbard, in order to make a quantitative assessment of the short term effects of different intensities of goose grazing. In addition we wanted to establish whether warming could enhance graminoid growth and regenerative capacity of grazed grasses. We carried out a factorial experiment of grazing (control, normal and high grazing pressure) using captive wild barnacle geese and temperature manipulation using open top chambers (OTCs) in a mesic and wet habitat in Adventdalen, Svalbard (78°N , 16°E ), following the growth of individual tillers before grazing and up until 20 days after grazing. OTCs enhanced temperatures and growth rates for Alopecurus in the mesic habitat, but slightly decreased belowground temperatures and early season growth for Dupontia in the wet habitat. Grazing stimulated growth rates resulting in increased cumulative leaf length production. The strength of response was greater for Alopecurus than Dupontia. We suggest that nutrients released by goose faeces were taken up by Alopecurus thus enhancing their growth rates, but that the thick layer of mosses prevented the addition of faeces from benefitting Dupontia as much
Natural variation in snow depth and snow melt timing in the High Arctic have implications for soil and plant nutrient status and vegetation composition
Snow cover is a key component in Arctic ecosystems and will likely be affected by
changes in winter precipitation. Increased snow depth and consequent later snowmelt leads
to greater microbial mineralization in winter, improving soil and vegetation nutrient
status. We studied areas with naturally differing snow depths and date of snowmelt in
Adventdalen, Svalbard. Soil properties, plant leaf nutrient status, and species composition
along with the normalized difference vegetation index (NDVI) were compared for three
snowmelt regimes (Early, Mid, and Late). We showed that (1) Late regimes (snow beds) had
wetter soils, higher pH, and leaves of Bistorta vivipara (L.) Delarbre and Salix polaris
Wahlenb. had higher concentration of nutrients (nitrogen and δ15N). Little to no difference
was found in soil nutrient concentrations between snowmelt regimes. (2) Late regimes had
highest NDVI values, whereas those of Early and Mid regimes were similar. (3) Vegetation
composition differed between Early and Late regimes, with Dryas octopetala L. and Luzula
arcuata subsp. confusa (Lange) characterizing the former and Equisetum arvense L. and
Eriophorum scheuchzeri Hoppe the latter. (4) Trends for plant nutrient contents were similar
to those found in a nearby snow manipulation experiment. Snow distribution and time of
snowmelt played an important role in determining regional environmental heterogeneity,
patchiness in plant community distribution, their species composition, and plant
phenology
Short-term herbivory has long-term consequences in warmed and ambient high Arctic tundra
Source at https://doi.org/10.1088/1748-9326/aa579d. Climate change is occurring across the world, with effects varying by ecosystem and region but
already occurring quickly in high-latitude and high-altitude regions. Biotic interactions are
important in determining ecosystem response to such changes, but few studies have been long-
term in nature, especially in the High Arctic. Mesic tundra plots on Svalbard, Norway, were
subjected to grazing at two different intensities by captive Barnacle geese from 2003–2005, in a
factorial design with warming by Open Top Chambers. Warming manipulations were continued
through 2014, when we measured vegetation structure and composition as well as growth and
reproduction of three dominant species in the mesic meadow. Significantly more dead vascular
plant material was found in warmed compared to ambient plots, regardless of grazing history,
but in contrast to many short-term experiments no difference in the amount of living material
was found. This has strong implications for nutrient and carbon cycling and could feed back into
community productivity. Dominant species showed increased
flowering in warmed plots,
especially in those plots where grazing had been applied. However, this added sexual
reproduction did not translate to substantial shifts in vegetative cover. Forbs and rushes increased
slightly in warmed plots regardless of grazing, while the dominant shrub,
Salix polaris
, generally
declined with effects dependent on grazing, and the evergreen shrub
Dryas octopetala
declined
with previous intensive grazing
.
There were no treatment effects on community diversity or
evenness. Thus despite no changes in total live abundance, a typical short-term response to
environmental conditions, we found pronounced changes in dead biomass indicating that tundra
ecosystem processes respond to medium- to long-term changes in conditions caused by 12
seasons of summer warming. We suggest that while high arctic tundra plant communities are
fairly resistant to current levels of climate warming, underlying ecosystem processes are beginning
to change. In addition, even short bouts of intense herbivory can have long-term consequences
for some species in these communities
Experimentally increased snow depth affects high Arctic microarthropods inconsistently over two consecutive winters
Climate change induced alterations to winter conditions may afect decomposer organisms controlling
the vast carbon stores in northern soils. Soil microarthropods are particularly abundant decomposers
in Arctic ecosystems. We studied whether increased snow depth afected microarthropods, and if
efects were consistent over two consecutive winters. We sampled Collembola and soil mites from
a snow accumulation experiment at Svalbard in early summer and used soil microclimatic data to
explore to which aspects of winter climate microarthropods are most sensitive. Community densities
difered substantially between years and increased snow depth had inconsistent efects. Deeper snow
hardly afected microarthropods in 2015, but decreased densities and altered relative abundances of
microarthropods and Collembola species after a milder winter in 2016. Although increased snow depth
increased soil temperatures by 3.2 °C throughout the snow cover periods, the best microclimatic
predictors of microarthropod density changes were spring soil temperature and snowmelt day. Our
study shows that extrapolation of observations of decomposer responses to altered winter climate
conditions to future scenarios should be avoided when communities are only sampled on a single
occasion, since efects of longer-term gradual changes in winter climate may be obscured by interannual weather variability and natural variability in population sizes
Ectomycorrhizal and saprotrophic fungi respond differently to long-term experimentally increased snow depth in the High Arctic
Source:DOI: 10.1002/mbo3.375Changing climate is expected to alter precipitation patterns in the Arctic, with
consequences for subsurface temperature and moisture conditions, community
structure, and nutrient mobilization through microbial belowground processes.
Here, we address the effect of increased snow depth on the variation in species
richness and community structure of ectomycorrhizal (ECM) and saprotrophic
fungi. Soil samples were collected weekly from mid-
July to mid-
September in
both control and deep snow plots. Richness of ECM fungi was lower, while
saprotrophic fungi was higher in increased snow depth plots relative to controls.
[Correction added on 23 September 2016 after first online publication: In the
preceding sentence, the richness of ECM and saprotrophic fungi were wrongly
interchanged and have been fixed in this current version.] ECM fungal richness
was related to soil NO3- N, NH4- N, and K; and saprotrophic fungi to NO3-N
and pH. Small but significant changes in the composition of saprotrophic fungi
could be attributed to snow treatment and sampling time, but not so for the
ECM fungi. Delayed snow melt did not influence the temporal variation in
fungal communities between the treatments. Results suggest that some fungal
species are favored, while others are disfavored resulting in their local extinction
due to long-
term changes in snow amount. Shifts in species composition of
fungal functional groups are likely to affect nutrient cycling, ecosystem respira-
tion, and stored permafrost carbon
Dead or Alive; or Does It Really Matter? Level of Congruency Between Trophic Modes in Total and Active Fungal Communities in High Arctic Soil
Describing dynamics of belowground organisms, such as fungi, can be challenging. Results of studies based on environmental DNA (eDNA) may be biased as the template does not discriminate between metabolically active cells and dead biomass. We analyzed ribosomal DNA (rDNA) and ribosomal RNA (rRNA) coextracted from 48 soil samples collected from a manipulated snow depth experiment in two distinct vegetation types in Svalbard, in the High Arctic. Our main goal was to compare if the rDNA and rRNA metabarcoding templates produced congruent results that would lead to consistent ecological interpretation. Data derived from both rDNA and rRNA clustered according to vegetation types. Different sets of environmental variables explained the community composition based on the metabarcoding template. rDNA and rRNA-derived community composition of symbiotrophs and saprotrophs, unlike pathotrophs, clustered together in a similar way as when the community composition was analyzed using all OTUs in the study. Mean OTU richness was higher for rRNA, especially in symbiotrophs. The metabarcoding template was more important than vegetation type in explaining differences in richness. The proportion of symbiotrophic, saprotrophic and functionally unassigned reads differed between rDNA and rRNA, but showed similar trends. There was no evidence for increased snow depth influence on fungal community composition or richness. Our findings suggest that template choice may be especially important for estimating biodiversity, such as richness and relative abundances, especially in Helotiales and Agaricales, but not for inferring community composition. Differences in study results originating from rDNA or rRNA may directly impact the ecological conclusions of one’s study, which could potentially lead to false conclusions on the dynamics of microbial communities in a rapidly changing Arctic
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