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The onset of agriculture improved the capacity of ecosystems to produce food, but inadvertently altered other vital ecosystem functions. Plant traits play a central role in determining ecosystem properties, therefore we investigated how the onset of agriculture in Europe changed plant trait composition using 78 pollen records. Using a novel Bayesian approach for reconstructing plant trait composition from pollen records, we provide a robust method that can account for trait variability within pollen types. We estimate an overall four‐fold decrease in plant size through agriculture and associated decreases in leaf and seed size. We show an increase in niche space towards the resource‐acquisitive end of the leaf economic spectrum. Decreases in leaf phosphorus might have been caused by nutrient depletion through grazing and burning. Our results show that agriculture, from its start, has likely been gradually impacting biogeochemical cycles through altered vegetation composition. [ABSTRACT FROM AUTHOR]

Lake Baikal, lying in a rift zone in southeastern Siberia, is the world's oldest, deepest, and most voluminous lake that began to form over 30 million years ago. Cited as the "most outstanding example of a freshwater ecosystem" and designated a World Heritage Site in 1996 due to its high level of endemicity, the lake and its ecosystem have become increasingly threatened by both climate change and anthropogenic disturbance. Here, we present a record of nutrient cycling in the lake, derived from the silicon isotope composition of diatoms, which dominate aquatic primary productivity. Using historical records from the region, we assess the extent to which natural and anthropogenic factors have altered biogeochemical cycling in the lake over the last 2,000 y.We show that rates of nutrient supply from deep waters to the photic zone have dramatically increased since the mid-19th century in response to changing wind dynamics, reduced ice cover, and their associated impact on limnological processes in the lake. With stressors linked to untreated sewage and catchment development also now impacting the near-shore region of Lake Baikal, the resilience of the lake's highly endemic ecosystem to ongoing and future disturbance is increasingly uncertain. [ABSTRACT FROM AUTHOR]

We investigated the response of lake algal communities to changes in glacial meltwater from the Renland Ice Cap (Greenland) through the Holocene to assess whether influxes always elicit consistent responses or novel responses. We measured sedimentary algal pigments in two proximal lakes, snow-fed Raven and glacier- and snow-fed Bunny Lake, and diatom community structure and turnover in Bunny Lake. Diatom data were not available in Raven Lake. We also modeled lake-level change in Bunny Lake to identify how glacial meltwater may have altered diatom habitat availability through time. Through a series of glacier advances and retreats over the Holocene, the algal response in Bunny Lake was relatively constant until approximately 1015 yr BP, after which there were major changes in sedimentary algal remains. Algal pigment concentrations sharply declined, and diatom species richness increased. Diatom community structure underwent three reorganizations. Until 1015 yr BP, assemblages were dominated by Pinnularia braunii and Aulacoseira pffaffiana. However, approximately 1015-480 yr BP, these species declined and Tabellaria flocculosa and Hannaea arcus became a significant component of the assemblage. Approximately 440 yr BP, A. pfaffiana increased along with species indicating elevated nitrogen. In contrast, the algal pigment records from nearby snow-fed Raven Lake showed different and minimal change through time. Our results suggest that changes in the magnitude and composition of meltwater in our two study lakes were unique over the last 1000 yr BP and elicited a non-linear threshold response absent during other periods of glacier advance and retreat. Deciphering the degree to which glaciers structure algal communities over time has strong implications for lakes as glaciers continue to recede. [ABSTRACT FROM AUTHOR]

Abstract: Diatom, magnetic susceptibility and loss-on-ignition (LOI) analyses of a 9-metre sediment core from Heygsvatn (Suðuroy, the Faroe Islands) were used to investigate the response of lake and catchment to mid-Late Holocene environmental change. A 30-lake training set from Faroese lakes was also used to explore the relationships between diatoms and environmental variables and assist in the interpretation of the diatom stratigraphy. Canonical Correspondence Analysis showed that lake depth, light penetration, total phosphorus (TP), pH and dissolved organic carbon (DOC) were the most significant variables affecting diatom distribution in Faroese lakes (p < 0.06). Nine 14C AMS dates indicated that the sediment record covered the last ~ 5700 years. Exceptionally high rates of sediment accumulation, an increase in LOI and magnetic susceptibility and inversion of radiocarbon dates suggested that a period of elevated soil erosion occurred at Heygsvatn ca. 1700–1200cal. yr. BP. Because this erosion pre-dates the arrival of humans the most likely cause is climate deterioration (cooler, wetter conditions). The diatom stratigraphy supports this hypothesis by showing that during the period of erosion the lake was deeper or/or more depauperate in TP, consistent with the climate becoming wetter and leading to increased lake flushing. Subsequently, with sustained sediment erosion, the lake became more shallow and pH increased as the lake infilled. In combination, the proxies support the idea that the climate became wetter ca. 1700–1200cal. yr. BP in the Faroe Islands, but that the response of the landscape was partly dependent on the increased development of peat initiated during the onset of Neoglacial cooling after 5000cal. years BP. [Copyright &y& Elsevier]