A high-altitude peatland record of environmental changes in the NW Argentine Andes (24 ° S) over the last 2100 years

High-altitude cushion peatlands are versatile archives for high-resolution palaeoenvironmental studies, due to their high accumulation rates, range of proxies, and sensitivity to climatic and/or human-induced changes. Especially within the Central Andes, the knowledge about climate conditions during the Holocene is limited. In this study, we present the environmental and climatic history for the last 2100 years of Cerro Tuzgle peatland (CTP), located in the dry Puna of NW Argentina, based on a multi-proxy approach. X-ray fluorescence (XRF), stable isotope and element content analyses (δ13C, δ15N, TN and TOC) were conducted to analyse the inorganic geochemistry throughout the sequence, revealing changes in the peatlands' past redox conditions. Pollen assemblages give an insight into substantial environmental changes on a regional scale. The palaeoclimate varied significantly during the last 2100 years. The results reflect prominent late Holocene climate anomalies and provide evidence that in situ moisture changes were coupled to the migration of the Intertropical Convergence Zone (ITCZ). A period of sustained dry conditions prevailed from around 150 BC to around AD 150. A more humid phase dominated between AD 200 and AD 550. Afterwards, the climate was characterised by changes between drier and wetter conditions, with droughts at around AD 650-800 and AD 1000-1100. Volcanic forcing at the beginning of the 19th century (1815 Tambora eruption) seems to have had an impact on climatic settings in the Central Andes. In the past, the peatland recovered from climatic perturbations. Today, CTP is heavily degraded by human interventions, and the peat deposit is becoming increasingly susceptible to erosion and incision.Fil: Schittek, Karsten. University of Heidelberg; Alemania. Universitat Zu Köln; AlemaniaFil: Kock, Sebastian T.. University of Heidelberg; Alemania. Research Center Jülich; AlemaniaFil: Lücke, Andreas. Helmholtz Gemeinschaft. Forschungszentrum Jülich; AlemaniaFil: Hense, Jonathan. Universitaet Bonn; AlemaniaFil: Ohlendorf, Christian. Universitat Bremen; AlemaniaFil: Kulemeyer, Julio José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Jujuy. Universidad Nacional de Jujuy. Centro de Investigaciones y Transferencia de Jujuy; ArgentinaFil: Lupo, Liliana Concepcion. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Jujuy. Universidad Nacional de Jujuy. Centro de Investigaciones y Transferencia de Jujuy; ArgentinaFil: Schäbitz, Frank. Universitat Zu Köln; Alemani

Stable Oxygen Isotope Records (δ18O) of a High-Andean Cushion Peatland in NW Argentina (24° S) Imply South American Summer Monsoon Related Moisture Changes During the Late Holocene

High-elevation cushion peatlands are promising archives for paleoenvironmental studies in their extreme habitat of the Central Andean highlands between ∼4000 and 4800 m a.s.l. The Cerro Tuzgle cushion peatland (CTP, 24°09′ S, 66°24′ W), located in the NW Argentine Andes, is formed by the vascular cushion plants Oxychloe andina (O. andina) and Zameioscirpus muticus (Z. muticus). To extend the knowledge base on the modern ecology of these peatlands, we investigated the stable isotope composition of bulk material and cellulose (δ18O, δ13C, δ15N) of the dominant cushion-forming species O. andina (Juncaceae) and Z. muticus (Cyperaceae) as well as water samples (δ18O, δ2H) of several pools interspersed within the peatland. We further applied a multiproxy approach for a peat core from CTP spanning the last 2900 years with XRF scanning, bulk geochemistry and stable isotope analyses on bulk peat and cellulose size fractions. Modern samples of O. andina and Z. muticus expose significant differences in cellulose δ18O, e.g., between leaves and rhizomes of O. andina (Δδ18Ol-r = 4.11‰) and between leaves of O. andina and Z. muticus (Δδ18Ol-l = 2.8‰). Modern water samples exhibit strong isotopic differences between single water pools (max. Δδ18O = 13.09‰) due to local variable evaporative enrichment. Within the peat core, we observe considerable multi-centennial variations in δ18O composition of cellulose confirmed by all size fractions. Based on the regional relation between decreasing δ18Oprec values with increasing precipitation amounts and 18O enrichment in the peatland waters due to evaporation, we suggest an interpretation of our δ18O cellulose record as moisture proxy for CTP. This interpretation is corroborated by a high correlation between oxygen isotopes, peat growth and geochemical data. Accordingly, CTP indicates dryer conditions between 2190 and 2120, 1750 and 1590, 1200 and 1080 and since 130 cal. yr BP, whereas periods with increased humidity prevailed from 2750 to 2250 and from 600 to 130 cal. yr BP. Temporal changes in the match to South American Summer Monsoon (SASM) reconstructions suggest impacts of other large-scale atmospheric variability modes or a different SASM expression at our southerly location

Geomorphodynamics as recorded in a high-Andean cushion peatland of the western Chilean Central Andes (27° S) during the last 1800 cal. yr BP

Due to their location at the southern margin of the Arid Diagonal, only a limited number of archives in the western Central Andes of Chile is capable for paleoclimate investigations. High-altitude cushion peatlands are potentially suitable to fill this gap despite their heterogenic stratigraphies representing past geomorphodynamics, especially for the Late Holocene. We investigated a 4 m sediment profile from the Lagunillas cushion peatland (LP, 27° 12' S, 69° 17' W), located in the dry Puna of the Western Central Andes. Directed by Electrical Resistivity Tomography (ERT) measurements, sediment cores were recovered at the deepest point of the investigated valley section. In total, 10 radiocarbon samples were used to build the age-depth model resulting in a sediment chronology spanning the last 1800 cal. yr BP. Core stratigraphy and ERT data were applied to allow insights into the sedimentary environment. Geochemical (X-ray fluorescence) and sedimentological (grain size) analyses were conducted to identify significant changes in sedimentation dynamics during the Late Holocene. Grain size analyses were investigated on 24 samples from peat layers as well as from stratigraphical sections characterized by allochthonous sediments. In combination with the results of the XRF measurements, evidence for changes in geomorphodynamic processes during the last 1800 cal. yr BP could be revealed. Our data disclose that investigations of heterogenic peat stratigraphies could also provide promising inferences about paleoclimatic changes. Within the Lagunillas record, stable phases of peat accumulation alternate with phases dominated by clastic material input. A stable phase of peat accumulation prevailed from 1750 cal. yr BP until about 1250 cal. yr BP and was followed by a phase with unstable conditions from 1250 to 980 cal. yr BP. During the Medieval Climate Anomaly (MCA) between 980 to 620 cal. yr BP, drier conditions prevailed at Lagunillas peatland, while shorter humid periods favored peat accumulation between 620 to 560 cal. yr BP. Higher precipitation amounts were evident during the Little Ice Age (LIA) from 560 –160 cal. yr BP. During the period from 160 cal. yr BP to recent times, a higher frequency of changes between peat accumulation and clastic layers occurred, presumably due to a decreasing trend in precipitation

Multi‐Centennial‐Scale Variations of South American Summer Monsoon Intensity in the Southern Central Andes (24–27°S) During the Late Holocene

Oxygen isotope records of cushion‐plant peat cellulose from the southern central Andes capture evidence for significant environmental changes. We observe that the δ18Ocell peatland record from Cerro Tuzgle (24°S) is in high conformity with the respective Lagunillas peatland record (27°S). During the late Holocene, two significant fluctuations occurred and are interpreted as regional moisture signals with increased precipitation amounts indicated during multi‐centennial phases from 1,530 to 1,270 cal. yr BP and from 470 to 70 cal. yr BP. These fluctuations can be best explained by changes in the strength of the South American summer monsoon (SASM). This interpretation is further supported by consistency with northern Andean paleoclimate records (10–13°S) and very high correlation (R2 = 0.76) with the Southern Oscillation Index. The congruent precipitation signals suggest the persistent climatic control of the SASM‐strength in this latitudinal band during the last 1,800 years

Role of LTBP4 in alveolarization, angiogenesis, and fibrosis in lungs

Deficiency of the extracellular matrix protein latent transforming growth factor-beta (TGF-beta)-binding protein-4 (LTBP4) results in lack of intact elastic fibers, which leads to disturbed pulmonary development and lack of normal alveolarization in humans and mice. Formation of alveoli and alveolar septation in pulmonary development requires the concerted interaction of extracellular matrix proteins, growth factors such as TGF-beta, fibroblasts, and myofibroblasts to promote elastogenesis as well as vascular formation in the alveolar septae. To investigate the role of LTBP4 in this context, lungs of LTBP4-deficient (Ltbp4(-/-)) mice were analyzed in close detail. We elucidate the role of LTBP4 in pulmonary alveolarization and show that three different, interacting mechanisms might contribute to alveolar septation defects in Ltbp4(-/-) lungs: 1) absence of an intact elastic fiber network, 2) reduced angiogenesis, and 3) upregulation of TGF-beta activity resulting in profibrotic processes in the lung