Annual temperatures on the Antarctic Peninsula, one of the most rapidly warming regions on Earth, have risen by up to 0.56°C per decade since the 1950s 1. Terrestrial and marine organisms have shown ...changes in populations and distributions over this time 2, 3, suggesting that the ecology of the Antarctic Peninsula is changing rapidly. However, these biological records are shorter in length than the meteorological data, and observed population changes cannot be securely linked to longer-term trends apparent in paleoclimate data 4. We developed a unique time series of past moss growth and soil microbial activity from a 150-year-old moss bank at the southern limit of significant plant growth based on accumulation rates, cellulose δ13C, and fossil testate amoebae. We show that growth rates and microbial productivity have risen rapidly since the 1960s, consistent with temperature changes 5, although recently they may have stalled 2. The recent increase in terrestrial plant growth rates and soil microbial activity are unprecedented in the last 150 years and are consistent with climate change. Future changes in terrestrial biota are likely to track projected temperature increases closely and will fundamentally change the ecology and appearance of the Antarctic Peninsula.
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•Antarctic moss growth and microbial activity changes are consistent with warming•Isotope and testate amoeba proxies show growth increased from the 1960s to the 1990s•Biological proxies show some decrease in growth since a late 1990s maximum
Changes in plant cover and productivity are important in driving Arctic soil carbon dynamics and sequestration, especially in peatlands. Warming trends in the Arctic are known to have resulted in ...changes in plant productivity, extent and community composition, but more data are still needed to improve understanding of the complex controls and processes involved. Here we assess plant productivity response to climate variability between 1985 and 2020 by comparing peak growing season NDVI (Normalised Difference Vegetation Index data from Landsat 5 and 7), to seasonal-average weather data (temperature, precipitation and snow-melt timing) in nine locations containing peatlands in high- and low-Arctic regions in Europe and Canada. We find that spring (correlation 0.36 for peat dominant and 0.39 for mosaic; MLR coefficient 0.20 for peat, 0.29 for mosaic), summer (0.47, 0.42; 0.18, 0.17) and preceding-autumn (0.35, 0.25; 0.33, 0.27) temperature are linked to peak growing season NDVI at our sites between 1985 and 2020, whilst spring snow melt timing (0.42, 0.45; 0.25, 0.32) is also important, and growing season water availability is likely site-specific. According to regression trees, a warm preceding autumn (September–October–November) is more important than a warm summer (June–July–August) in predicting the highest peak season productivity in the peat-dominated areas. Mechanisms linked to soil processes may explain the importance of previous-Autumn conditions on productivity. We further find that peak productivity increases in these Arctic peatlands are comparable to those in the surrounding non-peatland-dominant vegetation. Increased productivity in and around Arctic peatlands suggests a potential to increased soil carbon sequestration with future warming, but further work is needed to test whether this is evident in observations of recent peat accumulation and extent.
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•Peat dominant Arctic areas show greening trends similar to wider areas between 1985 and 2020.•Spring conditions, and summer and previous-autumn temperature are linked to peak growing-season NDVI in Arctic Peatlands.•Precipitation is not linked to peak NDVI, local hydrology is probably more important.•Autumn soil processes may be an important factor driving the following growing season's peak productivity.
Due to the scarcity of reliable and highly resolved moisture proxies covering much of the Holocene, there has been increased interest in the study of living and subfossil peatland trees sensitive to ...gradual and extreme changes in hydrology, precipitation, and related environmental processes. Peatland development and the associated carbon accumulation, which are strongly influenced by hydrological fluctuations, are also of prime importance as peatlands represent long-term sinks of atmospheric carbon. Improved knowledge of peatland development and soil moisture variability during the Holocene is therefore essential to our understanding of long-term hydroclimate changes, the terrestrial carbon cycle, and to enable more robust predictions of peatland response to future climate changes.
Here, we review the existing mid- to late Holocene peatland tree-ring chronologies that have been used to study climate variability on (sub-)annual to centennial scales with a primary focus on northern Europe. Since the 1970s, absolutely dated tree-ring chronologies covering substantial parts of the Holocene have been developed from excavated remains of oak (Quercus spp.) and pine (Pinus sylvestris L.). The annual tree-ring patterns of these trees are often characterized by periods of depressed growth reflecting annual to decadal hydroclimatic changes. In addition, changes in the spatio-temporal distribution of trees throughout the Holocene are often found to reflect decadal to centennial climate and hydrological changes. Moreover, synchronicity between tree-ring chronologies and tree-population dynamics over larger geographical areas show periods of coherent regional climate forcing, especially during the mid-Holocene.
This review (i) provides an overview of pioneering and recent studies presenting tree-ring chronologies developed from subfossil peatland trees, and (ii) presents recent developments in the fields of dendroecology (i.e. the response of tree growth and changes in vitality as a result of changes in climatic variables) and dendroclimatology (i.e. the reconstruction of climate fluctuations based on tree-ring analyses) in peatland regions. Moreover, we (iii) use long-term climate reconstructions based on alternative proxies for comparison, and (iv) present different ways to analyse tree-ring records to generate novel information on annual to centennial timescales. This analysis is based on an unprecedented network of tree-ring chronologies from Denmark, Finland, Germany, Great Britain, Ireland, Lithuania, the Netherlands, Poland, Sweden, and Canada, as well as a wealth of old and previously (un) published literature from Scandinavia and Germany, which has not been accessible to a wider audience in the past due to inaccessibility or linguistic barriers. Finally, a map of possible hotspots for the assessment of continuous peatland-tree studies is presented, along with suggestions for new research directions in the field.
•We review extensive peatland tree-ring chronologies from northern Europe covering major parts of the Holocene.•Long distance cross-matches (correlograms) and significant positive correlation point to larger-scale climate signals.•Subfossil peatland trees can be used for detailed palaeoclimatic and palaeohydrological reconstructions.•Warm/dry conditions are favourable for peatland tree growth, but may turn peatlands from carbon sinks to carbon sources.
Recent climate change on the Antarctic Peninsula is well documented 1–5, with warming, alongside increases in precipitation, wind strength, and melt season length 1, 6, 7, driving environmental ...change 8, 9. However, meteorological records mostly began in the 1950s, and paleoenvironmental datasets that provide a longer-term context to recent climate change are limited in number and often from single sites 7 and/or discontinuous in time 10, 11. Here we use moss bank cores from a 600-km transect from Green Island (65.3°S) to Elephant Island (61.1°S) as paleoclimate archives sensitive to regional temperature change, moderated by water availability and surface microclimate 12, 13. Mosses grow slowly, but cold temperatures minimize decomposition, facilitating multi-proxy analysis of preserved peat 14. Carbon isotope discrimination (Δ13C) in cellulose indicates the favorability of conditions for photosynthesis 15. Testate amoebae are representative heterotrophs in peatlands 16–18, so their populations are an indicator of microbial productivity 14. Moss growth and mass accumulation rates represent the balance between growth and decomposition 19. Analyzing these proxies in five cores at three sites over 150 years reveals increased biological activity over the past ca. 50 years, in response to climate change. We identified significant changepoints in all sites and proxies, suggesting fundamental and widespread changes in the terrestrial biosphere. The regional sensitivity of moss growth to past temperature rises suggests that terrestrial ecosystems will alter rapidly under future warming, leading to major changes in the biology and landscape of this iconic region—an Antarctic greening to parallel well-established observations in the Arctic 20.
•First Peninsula-wide assessment of biological sensitivity to recent warming•Analyze moss bank plant and microbial proxy data over 150 years and 600-km gradient•Fundamental and widespread changes in terrestrial biosphere in response to warming•Terrestrial ecosystems likely to alter rapidly under future warming scenarios
Amesbury et al. use plant and microbial material preserved in moss banks to demonstrate fundamental and widespread changes in the terrestrial biosphere of the Antarctic Peninsula in response to recent climate change. Moss growth sensitivity to climate suggests that the terrestrial biosphere and landscape will alter rapidly under future warming.
Protists are the most diverse eukaryotes. These microbes are keystone organisms of soil ecosystems and regulate essential processes of soil fertility such as nutrient cycling and plant growth. ...Despite this, protists have received little scientific attention, especially compared to bacteria, fungi and nematodes in soil studies. Recent methodological advances, particularly in molecular biology techniques, have made the study of soil protists more accessible, and have created a resurgence of interest in soil protistology. This ongoing revolution now enables comprehensive investigations of the structure and functioning of soil protist communities, paving the way to a new era in soil biology. Instead of providing an exhaustive review, we provide a synthesis of research gaps that should be prioritized in future studies of soil protistology to guide this rapidly developing research area. Based on a synthesis of expert opinion we propose 30 key questions covering a broad range of topics including evolution, phylogenetics, functional ecology, macroecology, paleoecology, and methodologies. These questions highlight a diversity of topics that will establish soil protistology as a hub discipline connecting different fundamental and applied fields such as ecology, biogeography, evolution, plant-microbe interactions, agronomy, and conservation biology. We are convinced that soil protistology has the potential to be one of the most exciting frontiers in biology.
•Protists are the most diverse eukaryotes in soils.•They are key elements in the soil food web and are essential for plant functioning.•Nevertheless, protists are highly understudied compared to other microorganisms.•We here provide an overview of missing research gaps to guide future studies.•This will allow bridging protistology to general microbiology and ecology in soils.
Multi-millennial climate changes were relatively minor over the mid–late Holocene in the British Isles, because orbitally forced insolation changes were smaller than those at higher latitudes. ...Centennial climate variability is thus likely to have exerted a greater influence on the environment and human society of the region. Proxy-climate records from the British Isles covering the last 4500
years are assembled and re-evaluated with the aim of identifying centennial climate variability reflected by multi-proxy indicators. The proxies include bog oak populations, peatland surface wetness, flooding episodes from fluvial deposits, speleothem annual band width and oxygen isotopes, chironomids from lake sediments and sand and dune deposition. Most proxies reflect water balance rather than temperature alone, and records predominantly reflect warm season climate. A series of 12 key periods of enhanced precipitation–evaporation (P-E) are identified by their presence in two or more proxy records. Variability in P-E is much greater than that shown by temperature proxies and there is no necessary association between warm/cool and dry/wet periods. Although the data for temperature are less robust than those for P-E, a series of key temperature changes are proposed based on speleothem δ
18O and chironomid inferred July temperature records; relatively cool before c. 3100
years BP, warmer (3100–2000
years BP), cool (2000–1250
cal years BP), warm (1250–650
cal years BP), and cool (650
cal years BP onwards). Some key increases in P-E (2750, 1650, 550
cal years BP) show a strong correspondence with ‘Bond cycles’ in ocean proxy records for increased ice rafted debris, decreased summer sea surface temperatures and sometimes decreased North Atlantic deep water circulation. Other higher frequency changes in P-E are also strongly related to SST variability. Whilst some of the main changes to cooler SSTs and increased P-E are approximately coincident with reduced solar output, most are not and thus must be the result of the internal dynamics of the ocean and atmosphere. Future work should concentrate on firmly establishing the pattern of temperature change, improving chronological accuracy and precision in existing records and improving process-based understanding of proxies.
Interpretation of proxy-climate records depends on a thorough understanding of the proxy-climate relationship. Peatland surface wetness records have been interpreted as reflecting changes between ...cool and/or wet conditions and warm and/or dry conditions. This paper analyses a high-resolution record of reconstructed water-table changes based on testate amoebae analysis in relation to instrumental weather records since AD 1775. Replicate peat records are reconciled by multiple chronological techniques and tuning, and demonstrate that the reconstructions preserve many replicable high-frequency changes. Water-table variability is highly correlated with the total seasonal moisture deficit (precipitation—evapotranspiration, P-E) expressed as the sum of all months with negative P-E. The reconstructed water-table record reflects antecedent periods of 5 or 10 years (maximum r2 = 52.4%) and proxy bog surface wetness records can therefore be interpreted as reflecting the length and intensity of the summer water deficit period. Response surfaces of the summer deficit in relation to temperature and precipitation variability support the hypothesis that the summer deficit is determined by summer precipitation in midlatitude oceanic peatlands and that summer temperature plays a greater but still subsidiary role in higher latitude, continental settings. These relationships apply for all plausible past Holocene climate changes and future twenty-first century climate scenarios. Non-linear responses to longer-term climate states prevent the direct application of a calibration of the reconstructed water-table records to infer quantitative estimates of climate variables. Models that combine peat accumulation, mire growth and hydrological processes are required to undertake this task.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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