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首页> 外文期刊>Journal of paleolimnology >Paleolimnological responses of Ecuadorian paramo lakes to local and regional stressors over the last two millennia
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Paleolimnological responses of Ecuadorian paramo lakes to local and regional stressors over the last two millennia

机译：Paleolimnological responses of Ecuadorian paramo lakes to local and regional stressors over the last two millennia

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Increasing surface air temperatures and human influences (e.g., agriculture, livestock grazing, tourism) are altering lacustrine ecosystems in the South American Andean paramo, and these influences are evident in changes in the diatom-species composition in sediment cores from the region that span the last similar to 150 years. Existing studies are limited by their short temporal scales and limited spatial extent. We analyzed two sediment cores spanning the last two millennia from the northern (Laguna Pinan) and southern (Laguna Fondococha) Andean paramo of Ecuador to provide a longer-term perspective on lake dynamics. Both lakes show shifts in the dominant diatoms through time. Fondococha diatoms shifted in dominance between two Aulacoseira species and in the planktic to benthic ratio, and these shifts are interpreted as evidence of changing lake level. The inferred shifts are corroborated by changes in sediment geochemistry. Pinan shows a directional shift in the diatom assemblage over the period of the record, from benthic diatoms tolerant of high dissolved organic carbon (DOC), low pH, and low nutrients, to an assemblage characteristic of lower DOC, Melina use only one higher for pH, nutrients and lake levels. Shifts in Pinan's diatoms are correlated with tephra layers in the sediment, suggesting that local volcanic deposition may have been responsible for altering the catchment and lake geochemistry. This is supported by relatively high delta C-13 values in organic matter associated with tephra layers, which become more negative up-section. Our study suggests that remote lakes in spatially heterogenous montane regions act as sentinels of different facets of environmental change and provide insights into Andean ecosystem responses to environmental perturbations.

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