• Energy Research
• 2021-2025close

SummaryLichens play important roles in habitat formation and community succession in polar and alpine ecosystems. Despite their significance, the ecological effects of lichen traits remain poorly researched. We propose a trait trade‐off for managing light exposure based on climatic harshness. In the harshest cold environments, where abiotic stress predominates over biotic pressures, lichens should rely on photostable, recalcitrant and immobile substances such as allomelanin and hydrophobic compounds. These compounds provide durable protection without the need for continual synthesis. In milder conditions where biotic interactions – for example, competition and pathogen presence – become increasingly pronounced, lichens should retain flexibility and produce simple protective secondary compounds that, in addition to functioning as light screens, can leach out to influence their direct environment. Preliminary empirical findings for Antarctic lichen species distribution are consistent with this hypothesised trade‐off, in that lichens producing soluble compounds dominate in milder regions and are less represented at higher southern latitudes, where species producing insoluble compounds with a melanised thallus dominate. As climate change progresses, increasing temperatures and precipitation could make the currently coldest and driest areas more hospitable, allowing the ranges of lichens producing soluble compounds to expand, with cascading effects on rock weathering, nutrient cycling and other ecosystem processes.

1.AbstractThe Arctic harbours uniquely adapted biodiversity and plays an important role in climate regulation. Strong warming trends in the terrestrial Arctic have been linked to an increase in aboveground biomass (Arctic greening) and community-wide shifts such as the northwards-expansion of boreal species (borealisation). Whilst considerable efforts have been made to understand the effects of warming trends in average temperatures on Arctic biota, far fewer studies have focused on trends in extreme climate events and their biotic effects, which have been suggested to be particularly impactful during the Arctic winter months. Here, we present an analysis of trends in two ecologically-relevant winter extreme events –extreme winter warming and rain-on-snow, followed by a meta-analysis on the evidence base for their effects on Arctic biota. We show a strong increase in extreme winter warming across the entire Arctic and high variability in rain-on-snow trends, with some regions recently experiencing rain-on-snow for the first time whilst others seeing a decrease in these events. Ultimately, both extreme events show significant changes in their characteristics and patterns of emergence. Our meta-analysis –encompassing 178 effect sizes across 17 studies and 49 species– demonstrates that extreme winter warming and rain-on-snow induce negative impacts on Arctic biota, with certain taxonomic groups –notably angiosperms and chordates (mostly vertebrates)– exhibiting higher sensitivity than others. Our study provides evidence for both emerging trends in Arctic winter extreme climate events and significant negative biotic effects of such events –which calls for attention to winter weather variability under climate change in the conservation of Arctic biodiversity, whilst highlighting important knowledge gaps.

AbstractThe regional variability in tundra and boreal carbon dioxide (CO2) fluxes can be high, complicating efforts to quantify sink‐source patterns across the entire region. Statistical models are increasingly used to predict (i.e., upscale) CO2 fluxes across large spatial domains, but the reliability of different modeling techniques, each with different specifications and assumptions, has not been assessed in detail. Here, we compile eddy covariance and chamber measurements of annual and growing season CO2 fluxes of gross primary productivity (GPP), ecosystem respiration (ER), and net ecosystem exchange (NEE) during 1990–2015 from 148 terrestrial high‐latitude (i.e., tundra and boreal) sites to analyze the spatial patterns and drivers of CO2 fluxes and test the accuracy and uncertainty of different statistical models. CO2 fluxes were upscaled at relatively high spatial resolution (1 km2) across the high‐latitude region using five commonly used statistical models and their ensemble, that is, the median of all five models, using climatic, vegetation, and soil predictors. We found the performance of machine learning and ensemble predictions to outperform traditional regression methods. We also found the predictive performance of NEE‐focused models to be low, relative to models predicting GPP and ER. Our data compilation and ensemble predictions showed that CO2 sink strength was larger in the boreal biome (observed and predicted average annual NEE −46 and −29 g C m−2 yr−1, respectively) compared to tundra (average annual NEE +10 and −2 g C m−2 yr−1). This pattern was associated with large spatial variability, reflecting local heterogeneity in soil organic carbon stocks, climate, and vegetation productivity. The terrestrial ecosystem CO2 budget, estimated using the annual NEE ensemble prediction, suggests the high‐latitude region was on average an annual CO2 sink during 1990–2015, although uncertainty remains high.

AbstractThe Antarctic Peninsula is under pressure from non-native plants and this risk is expected to increase under climate warming. Establishment and subsequent range expansion of non-native plants depend in part on germination ability under Antarctic conditions, but quantifying these processes has yet to receive detailed study. Viability testing and plant growth responses under simulated Antarctic soil surface conditions over an annual cycle show that 16 non-native species, including grasses, herbs, rushes and a succulent, germinated and continued development under a warming scenario. Thermal germination requirement (degree day sum) was calculated for each species and field soil-temperature recordings indicate that this is satisfied as far south as 72° S. Here, we show that the establishment potential of non-native species, in number and geographical range, is considerably greater than currently suggested by species distribution modelling approaches, with important implications for risk assessments of non-native species along the Antarctic Peninsula.

Climate change, coupled with the introduction of non-native organisms, represent major threats to the functioning of ecosystems, especially in species-poor communities such as polar terrestrial ecosystems. In this laboratory study, we quantified the impacts of the non-native springtail Folsomia candida and isopod Porcellio scaber on seed germination and growth of the non-native grass Poa pratensis, and ecosystem respiration. The impacts of invertebrate communities of progressively increasing complexity were assessed, starting with the native springtail Cryptopygus antarcticus alone, followed by C. antarcticus in combination with F. candida or P. scaber and, finally, a community including all three species. The impact of these invertebrate communities were studied in a simulation of contemporary Antarctic soil surface conditions (2 °C) and a +5 °C warming scenario over one growing season. Warming resulted in earlier germination (21 d), 10-fold increased plant biomass, N-content (>5-fold), and higher levels (90%) of ecosystem respiration. Warming also resulted in a 350% increase in C. antarcticus abundance. The presence of the woodlouse P. scaber had the strongest impact on the measured soil and plant variables and this impact was largely irrespective of temperature. Impacts included: delay in seedling emergence (4 d), reduced plant emergence (20%), and higher ecosystem respiration (135%). The presence of both C. antarcticus and P. scaber resulted in 30% higher plant leaf N-content and a reduction in C:N ratio from 21 to 17. The experimental communities containing F. candida showed a 37% reduction in plant biomass under warming. The presence of P. scaber reduced C. antarcticus abundance (94%) but F. candida abundance was unaffected. Our data indicate that non-native invertebrates differ in their ecosystem impacts, with potentially significant consequences for ecosystem functioning and community composition of plants and animals in cold biomes.