A high-resolution pollen record from western Greece shows that the amplitude of millennial-scale oscillations in tree abundance during the last glacial period was subdued, with temperate tree ...populations surviving throughout the interval. This provides evidence for the existence of an area of relative ecological stability, reflecting the influence of continued moisture availability and varied topography. Long-term buffering of populations from climatic extremes, together with genetic isolation at such refugial sites, may have allowed lineage divergence to proceed through the Quaternary. Such ecologically stable areas may be critical not only for the long-term survival of species, but also for the emergence of new ones.
Large, intact areas of tropical peatland are highly threatened at a global scale by the expansion of commercial agriculture and other forms of economic development. Conserving peatlands on a ...landscape scale, with their hydrology intact, is of international conservation importance to preserve their distinctive biodiversity and ecosystem services and maintain their resilience to future environmental change. We explored threats to and opportunities for conserving remaining intact tropical peatlands; thus, we excluded peatlands of Indonesia and Malaysia, where extensive deforestation, drainage, and conversion to plantations means conservation in this region can protect only small fragments of the original ecosystem. We focused on a case study, the Pastaza-Marañón Foreland Basin (PMFB) in Peru, which is among the largest known intact tropical peatland landscapes in the world and is representative of peatland vulnerability. Maintenance of the hydrological conditions critical for carbon storage and ecosystem function of peatlands is, in the PMFB, primarily threatened by expansion of commercial agriculture linked to new transport infrastructure that is facilitating access to remote areas. There remain opportunities in the PMFB and elsewhere to develop alternative, more sustainable land-use practices. Although some of the peatlands in the PMFB fall within existing legally protected areas, this protection does not include the most carbon-dense (domed pole forest) areas. New carbon-based conservation instruments (e.g., REDD+, Green Climate Fund), developing markets for sustainable peatland products, transferring land title to local communities, and expanding protected areas offer pathways to increased protection for intact tropical peatlands in Amazonia and elsewhere, such as those in New Guinea and Central Africa which remain, for the moment, broadly beyond the frontier of commercial development. Extensas e intactas áreas de turberas tropicales están severamente amenazadas a escala mundial, debido a la expansión de la agricultura comercial y a otras formas de desarrollo económico. La conservación de las turberas como parte del medio natural, con su hidrología no intervenida, es de importancia internacional para asegurar la conservación de su biodiversidad tan característica y de los servicios ambientales que ofrecen, y así mantener su resiliencia ante futuros cambios ambientales. Exploramos las amenazas y las oportunidades para conservar las turberas tropicales intactas y remanentes. Nuestro enfoque por lo tanto excluye las turberas de Indonesia y Malasia, donde la deforestación de forma extensiva y el drenado para el establecimiento de plantaciones hace que la conservación en estas regiones pueda proteger solo pequeños fragmentos del ecosistema original En este estudio, nos enfocamos en las cuencas del Pastaza Marañón (PMFB, siglas en inglés) en Perú, que comprende una de las turberas tropicales intactas más extensas del mundo y es representativa de la vulnerabilidad que las amenaza. El mantenimiento de las condiciones hidrológicas críticas para el almacenamiento de carbono y la función ambiental de las turberas está, en la PMFB, amenazada principalmente por la expansión de la agricultura comercial y las nuevas vías de transporte que facilitan el acceso a las áreas remotas. En la PMFB y en otros lugares aún hay oportunidades para desarrollar prácticas alternativas y sostenibles del uso del suelo. Aunque algunas de las turberas en la PMFB caen dentro de áreas naturales protegidas, esta protección no incluye las áreas con mayor densidad de carbono (varillal hidromórfico). Nuevas herramientas para la conservación basada en el carbono (p.e. REDD+, Fondo Verde para el Clima), el desarrollo de mercados para los productos de las turberas, la transferencia de títulos de propiedad de la tierra a las comunidades locales, y la expansión de las áreas protegidas ofrecen alternativas para una mayor protección de las turberas tropicales intactas en la Amazonia y en otros lugares, como las turberas de Nueva Guinea y África Central que permanecen, por el momento, alejadas de la frontera de desarrollo comercial.
Recent investigations of wetlands in western Amazonia have revealed the presence of extensive peat deposits up to 7.5m thick developing under a variety of vegetation types. We report the first ...attempt to establish the long-term (centennial to millennial scale) vegetation history of one of these peatland sites, Quistococha, a palm swamp close to Iquitos in northern Peru. Pollen and sedimentological analyses show that peat formation began at the core site under sedge fen or floating mat vegetation c. 2200 calendar years before present (calyr BP). A seasonally flooded woodland developed c. 1880calyr BP. The permanently waterlogged palm swamp which persists today began to form c. 1000calyr BP, with the present vegetation community established by c. 400years ago. The vegetation at this site has undergone continuous change throughout the period of peat formation, with several abrupt transitions, and reversals and repetitions in the apparent trajectory of change. The pollen data, combined with sedimentary evidence, suggest that the dominant control on ecosystem functioning and development is the flooding regime. There appears to have been a decrease in fluvial influence over time. There is no clear evidence of direct climatic or anthropogenic influence although we cannot rule out the possibility of climatically driven hydrological changes. Our results caution against adopting a simple model of peatland vegetation succession in this region.
► We present the first pollen record from a Peruvian Amazonian palm swamp. ► Development of the modern vegetation took 2200years in several stages. ► Succession involved abrupt transitions between short-lived communities and reversals. ► The main allogenic control was flooding regime on the very dynamic Amazon floodplain. ► Wetlands are unusually dynamic and variable relative to other Amazonian ecosystems.
Despite the widespread application of tephra studies for dating and correlation of stratigraphic sequences (‘tephrochronology’), questions remain over the reliability and replicability of tephra ...records from lake sediments and peats, particularly in sites >1000 km from source volcanoes. To address this, we examine the tephrostratigraphy of four pairs of lake and peatland sites in close proximity to one another (<10 km), and evaluate the extent to which the microscopic (crypto-) tephra records in lakes and peatlands differ. The peatlands typically record more cryptotephra layers than nearby lakes, but cryptotephra records from high-latitude peatlands can be incomplete, possibly due to tephra fallout onto snow and subsequent redistribution across the peatland surface by wind and during snowmelt. We find no evidence for chemical alteration of glass shards in peatland or lake environments over the time scale of this study (mid-to late- Holocene). Instead, the low number of basaltic cryptotephra layers identified in distal peatlands reflects the capture of only primary tephra-fall, whereas lakes concentrate tephra falling across their catchments which subsequently washes into the lake, adding to the primary tephra fallout received in the lake. A combination of records from both lakes and peatlands must be used to establish the most comprehensive and complete regional tephrostratigraphies. We also describe two previously unreported late Holocene cryptotephras and demonstrate, for the first time, that Holocene Icelandic ash clouds frequently reached Arctic Sweden.
•Lakes and peatlands provide contrasting records of volcanic ash deposition.•Generally, we see more tephra layers in peatlands than lakes.•Tephra shards show no chemical alteration in either lakes or peatlands.•More basaltic tephra layers are found in lakes which act to concentrate shards.•We report two new distal Icelandic tephras in Ireland (CLA-L1) and Sweden (SN-1).
The long baseline between Earth and the Sun makes solar neutrinos an excellent test beam for exploring possible neutrino decay. The signature of such decay would be an energy-dependent distortion of ...the traditional survival probability which can be fit for using well-developed and high-precision analysis methods. Here a model including neutrino decay is fit to all three phases of B8 solar neutrino data taken by the Sudbury Neutrino Observatory (SNO). This fit constrains the lifetime of neutrino mass state ν2 to be >8.08×10−5 s/eV at 90% confidence. An analysis combining this SNO result with those from other solar neutrino experiments results in a combined limit for the lifetime of mass state ν2 of >1.92×10−3 s/eV at 90% confidence.
ABSTRACT
Peat in the Pastaza–Marañón Foreland Basin (PMFB), northern Peru, forms beneath open wetlands, palm swamps, pole forests and seasonally flooded forests. These vegetation communities may ...represent different successional stages of peatlands, but the spatiotemporal patterns of peatland development in Amazonia are still poorly understood. We present a new geochemical and palaeoecological record spanning the last c. 4330 years from an open peatland (San Roque, core SAR_T3_03_B). Our results suggest the persistence of predominantly herbaceous vegetation communities at the core site since the start of peat accumulation (c. 3180 cal a bp). Micro‐X‐ray fluorescence core scanning provides evidence for episodes of fluvially derived minerogenic input and simultaneous increases in flood‐tolerant taxa relating to intervals of increased frequency and depth of riverine flooding. The establishment of Mauritia flexuosa palms from around 440 cal a bp coincided with a shift to lower flooding depth and frequency which continues to the present day. This study reveals the role of flooding variability in shaping peatland development and influencing vegetation succession in the PMFB, underlining the need to understand natural environmental variability for the conservation of these ecosystems due to their vital contributions to ecosystem services and carbon storage.
Aim To characterize the changing fire regime of a Mediterranean landscape during the Holocene and the Last Interglacial and, by comparing the two periods, to improve our understanding of the extent ...and timing of human alteration of natural fire regimes. Location Lake Ioannina, north-western Greece (39°45′ N, 20°51′ E). Methods Using a long sequence of lake sediments, we measured the charcoal content of the sediment over the course of the Holocene and the Last Interglacial. We compared the charcoal data with pollen data for the same periods. Results Charcoal was present in all samples analysed. Charcoal influx was greater during interglacials, which at Ioannina were forested, than during glacials, when tree populations were small. Charcoal influx was greater and more variable during the Holocene than during the Last Interglacial. Main conclusions Fire was a persistent feature throughout the periods studied, under both glacial and interglacial conditions. Overall, more biomass was burned during interglacials than during glacials, and peak burning occurred at intermediate values of moisture availability. There is little evidence that the composition of forests significantly affected burning regimes. Enhanced burning during the Holocene relative to the Last Interglacial may reflect human impact, as well as climatic or vegetational differences between the two periods.
A search has been performed for neutrinos from two sources, the hep reaction in the solar pp fusion chain and the νe component of the diffuse supernova neutrino background (DSNB), using the full ...dataset of the Sudbury Neutrino Observatory with a total exposure of 2.47 kton − years after fiducialization. The hep search is performed using both a single-bin counting analysis and a likelihood fit. We find a best-fit flux that is compatible with solar model predictions while remaining consistent with zero flux, and set a one-sided upper limit of Φhep < 30 × 103 cm−2 s−1 90% credible interval (CI). No events are observed in the DSNB search region, and we set an improved upper bound on the νe component of the DSNB flux of ΦνeDSNB < 19 cm−2 s−1 (90% CI) in the energy range 22.9 < Eν < 36.9 MeV.
A new pollen record of the penultimate interglacial complex, corresponding approximately to marine isotope stage (MIS) 7 (ca 186,000–245,000 years before present), has been generated in core I-284 ...from the Ioannina basin in northwest Greece. It represents the highest resolution terrestrial record for this interval available to date, with a mean sampling interval of 200 years. The sequence records four forested intervals, correlated with MIS 7e, 7c, 7a and a sub-orbital-scale event following 7a but within MIS 7. The longest and most complete warm stage in terms of vegetational succession is MIS 7c, while the succession in MIS 7e appears to be truncated by a shift to colder, drier climatic conditions. The results of biomisation suggest that during all of these intervals winter temperatures in NW Greece remained lower than during the Eemian or Holocene, while smaller populations of sclerophyllous taxa indicate that summers may have been wetter. Intervening intervals of open vegetation are correlated with MIS 7d, 7b and an oscillation following 7a. Low tree pollen percentages during MIS 7d are interpreted as reflecting very cold and dry conditions, concomitant with a period of low northern hemisphere insolation which resulted from a rare combination of minimum obliquity and maximum precession. Higher tree pollen percentages throughout MIS 7b, by contrast, are indicative of relatively mild conditions, in agreement with marine temperature and ice volume records. Sub-orbital scale oscillations in tree population extent are also recorded in the new I-284 record suggesting that, just as in the last climatic cycle, NW Greece was affected by rapid climatic oscillations that are associated with changes in the North Atlantic.
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