Inferências sobre Vegetação e Clima no Holoceno a partir de Fitólitos e Pólen da Lagoa do Macuco, Litoral Norte do Estado do Espírito Santo (Brasil)

[EN] An interproxy approach focused on phytoliths and pollen, including radiocarbon dating and sediment particle-size analyses, has been carried out at Lagoa do Macuco, Linhares municipality, Espírito Santo State, Brazil. Three pollen zones were identified: the first one (MAC-C I) indicates the presence of mangrove vegetation between 7700 cal yr BP and 4396 cal yr BP; the second one a displacement of the vegetation from the lower areas to the more elevated margins of the valley (MAC-C II, from between 4396 to 1287 cal. yr BP) and third one (MAC-C III), representing the period of the current lake evolution, between 1287 cal. yr BP and the present day. The displacement of the mangrove seems to be connected to the landward migration of the palaeo-estuary and the flooding of the lower parts of the valley, reflecting the relative sea-level highstand, which occurred after 7000 cal yr BP. The phytolith analysis indicated four main zone. The phytolith zone I (7700-7100 cal yr BP) did not show the presence of phytoliths. The phytoliths zone II (7100-3400 cal yr BP) indicates the presence of an open vegetation predominantly of grasses while phytolith zone III (3400-400 cal yr BP) shows a phase with more forested vegetation. Finally, the phytolith zone IV (400 cal yr BP to modern) has a decrease in tree cover and the setting of vegetation with a strong grasses component. Phytoliths indices indicate trends of humidity and temperature at a more local scale, allowing understanding the environmental conditions during the formation of the current lake.[PT] Uma abordagem interproxy focada na análise de fitólitos e de grãos de pólen, também incluindo datação 14C e análise granulométrica de sedimentos, foi aplicada ao estudo da Lagoa do Macuco, em Linhares no Estado do Espírito Santo. Foram identificadas três zonas polínicas definidas com base nas mudanças do registro polínico, a primeira (MAC-C I) indicando a presença de uma vegetação de mangue entre 7700 anos cal AP e 4396 anos cal AP, a segunda (MAC-C II) que representa o deslocamento da vegetação das áreas mais baixas para as partes marginais mais elevadas do vale (4396 anos cal AP - 1287 anos cal AP) e a terceira (MAC-C III) que representa o período da instalação do atual lago, entre 1287 anos cal AP e os dias atuais. O deslocamento do mangue parece estar conectado a migração em direção ao paleo-estuário e o alagamento das partes baixas do vale, refletindo a elevação do nível relativo do mar depois de 7000 cal anos AP. A análise fitolítica indicou quatro zonas principais. A zona fitolítica I (7700-7100 anos cal AP), não apresentou fitólitos. A zona fitolítica II (7100-3400 anos cal AP) indica a presença de uma vegetação predominantemente composta por gramíneas, enquanto a zona fitolítica III (3400-400 anos cal AP) mostrou uma fase com uma vegetação mais florestada. Finalmente, a zona fitolítica IV, (400 anos cal AP até os dias atuais) apresentou decréscimo da cobertura arbórea e uma estrutura de vegetação com forte presença de gramíneas em sua composição. Os índices fitolíticos indicaram tendência de umidade e temperatura em escala local permitindo a compreensão das condições ambientais durante a formação do lago atual.The authors express their gratitude to Vale and Sooretama Nature Reserves (Linhares, ES, Brasil) for the field support. This work received financial support by the São Paulo Foundation for Research (FAPESP), grant 2011/00995-7, and CNPq (Universal), grant 470210/2012-5.Peer Reviewe

Uncoupling human and climate drivers of late Holocene vegetation change in southern Brazil

In the highlands of southern Brazil an anthropogenitcally driven expansion of forest occurred at the expense of grasslands between 1410 and 900cal BP, coincident with a period of demographic and cultural change in the region. Previous studies have debated the relative contributions of increasing wetter and warmer climate conditions and human landscape modifcations to forest expansion, but generally lacked high resoltiuon proxies to measure these efects, or have relied on single proxies to reconstruct both climate and vegetation. Here, we develop and test a model of natural ecosystem distribution against vegetation histories, paleoclimate proxies, and the archaeological record to distinguish human from temperature and precipitation impacts on the distribution and expansion of Araucaria forests during the late Holocene. Carbon isotopes from soil profles confrm that in spite of climatic fuctuations, vegetation was stable and forests were spatially limited to south-facing slopes in the absence of human inputs. In contrast, forest management strategies for the past 1400 years expanded this economically important forest beyond its natural geographic boundaries in areas of dense pre-Columbian occupation, suggesting that landscape modifcations were linked to demographic changes, the efects of which are still visible today

Amazon Basin forest pyrogenic carbon stocks: First estimate of deep storage

Amazon Basin forest soils contain considerable soil organic carbon stocks; however, the contribution of soil pyrogenic carbon (PyC) to the total is unknown. PyC is derived from local fires (historical and modern) and external inputs via aeolian deposition. To establish an initial estimate of PyC stocks in non-terra preta forest with no known history of fire, to assess site and vertical variability, as well as to determine optimal sampling design, we sampled 37 one hectare forest plots in the Amazon Basin and analysed PyC via hydrogen pyrolysis of three individual samples per plot and of bulked samples to 200 cm depth. Using our data and published total organic carbon stocks, we present the first field-based estimate of total PyC stock for the Amazon Basin of 1.10 Pg over 0–30 cm soil depth, and 2.76 Pg over 0–100 cm soil depth. This is up to 20 times higher than previously assumed. Three individual samples per 1 ha are sufficient to capture the site variability of PyC in our plots. PyC showed significant, large-scale variability among plots. To capture 50% of the PyC in 200 cm soil profiles, soil must be sampled to a depth of at least 71 cm. PyC represents a significant (11%) portion of total organic carbon in soil profiles 0–200 cm depth. This finding highlights the potentially important role that historical fire has played in modifying soil C stocks. Our data suggest that PyC is an important carbon pool for long-term storage, involved in millennial scale biogeochemical cycling, particularly in the subsurface soil

Interdisciplinary paleovegetation study in the Fernando de Noronha Island (Pernambuco State), northeastern Brazil

The aim of this research was to reconstruct vegetation changes (with climate inferences) that occurred during the Holocene in the Fernando de Noronha Island, Pernambuco State, northeastern Brazil. The research approach included the use of geochemical (mineralogy, elemental), carbon isotopes (δ13C, 14C) and pollen analyses in soil organic matter (SOM) and sediments collected in Lagoa da Viração and Manguezal do Sueste. The carbon isotopes data of SOM indicated that there was no significant vegetation changes during the last 7400 BP, suggesting that the climate was not the determinant factor for the vegetation dynamics. The pollen analysis of the sediment of a core collected in the Lagoa da Viração showed the absence of Quaternary material in the period between 720 BP and 90 BP. The mineralogical analysis of deeper layer showed the presence of diopside indicating this material was developed "in situ". Only in the shallow part of the core were found pollen of similar plant species of the modern vegetation. The geochemistry and isotope results, in association with the sediment type and pollen analyses of sediment samples of Manguezal do Sueste, indicated variations in the vegetation and in its location since the middle Holocene. Such variations can be associated with climatic events and sea level oscillations and also with anthropogenic events considering the last five hundred years._________________________________________________________________________________________ RESUMO: Esta pesquisa teve o objetivo de reconstruir trocas de vegetação (com referências climáticas) que ocorreram durante o Holoceno na ilha de Fernando de Noronha, Estado de Pernambuco, nordeste do Brasil. Para o desenvolvimento da pesquisa utilizou-se de análises geoquímicas (minerais, elementar), isótopos do carbono (δ13C, 14C) e análises polínicas em solos e sedimentos coletados na Lagoa da Viração e no manguezal do Sueste. Os isótopos do carbono dos solos indicaram que não houve trocas significativas de vegetação durante os últimos 7400 anos AP, sugerindo que o clima não foi um fator determinante para a dinâmica da vegetação. A análise polínica dos sedimentos da Lagoa da Viração mostrou ausência de elementos quaternários no período entre 720 AP e 90 AP. A análise mineralógica das camadas mais profundas mostrou a presença de diopsídeo, indicando que este material foi desenvolvido"in situ". Somente na parte superficial do testemunho foram encontrados palinomorfos de plantas similares à vegetação moderna. Os resultados geoquímicos e isotópicos, em associação com o tipo de sedimento e as análises polínicas das amostras de sedimento do Manguezal do Sueste, indicaram variações na vegetação e na sua localização desde o Holoceno médio. Tais variações podem estar associadas a eventos climáticos e oscilações do nível do mar e também a eventos antrópicos considerando os últimos quinhentos anos

Hydrological influence on the evolution of a subtropical mangrove ecosystem during the late Holocene from Babitonga Bay, Brazil

Mangroves are key ecosystems which respond to global changes in tropical and subtropical regions worldwide. We describe late Holocene mangroves that established close to the southernmost limit (28°S) for this type of ecosystem in South America. Our findings are based on a C dated core obtained from Babitonga Bay, Santa Catarina State, Brazil (26°12′S, 48°33′W). Analysis of palynology, sedimentary facies, isotopic and elemental data shows that mangrove establishment took place ~500 yrs. B.C.E., following an increase in humidity, and expanded further during the Roman Warm Period and at the end of Dark Age Cold Period. Mangrove and precipitation proxies records appear to be sensitive to rainfall patterns imposed both by the expansion/retraction of the Intertropical Convergence Zone and also the interaction with the South Atlantic Subtropical Anticyclone which affects coastal region due to sea surface temperature variations.The authors thank the Coastal Dynamic Laboratory (LADIC-UFPA) , C-14 Laboratory of the Center for Nuclear Energy in Agriculture (CENA-USP) , University of Joinville (UNIVILLE) and Radiocarbon Laboratory (LAC-UFF) for all infrastructure and support. We also thank three anonymous Reviewers and Prof. H. Falcon-Lang for their constructive comments. The first and third author thanks Brazilian Council for Technology and Science-CNPq for fellowship (process 131813/2016-1 , 165911/2015-8 and 305074/2017-2 ). This study was financed by CNPq ( 445111/2014-3 , 405060/2013- 0 ) and FAPESP ( 2011/00995-7 , 2017/03304-1, and 2020/13715-1 ). This study also was financed in part by the Coordenação de Aperfeiçoamento de Pessoal Nível Superior – Brazil (CAPES) – Finance Code 001

Estudos paleoambientais interdisciplinares: dinâmica da vegetação, do ambiente marinho e inferências climáticas milenares a atuais na Costa Norte do Espírito Santo, Brasil

Estudos paleoambientais desde ~50.000 anos na costa do Brasil e, em particular, no litoral do Espírito Santo, são ainda insuficientes para servir de base a reconstituições da dinâmica da vegetação, de oscilações do nível relativo do mar e de flutuações climáticas e respectivas influências sobre a ação humana milenar. Para obter essas informações, uma equipe interdisciplinar, financiada por projetos temáticos FAPESP e CNPq, desenvolveu pesquisas correlatas na Reserva Natural Vale (RNV) e região. Para a caracterização da dinâmica da vegetação e marinha, com inferências climáticas, em locais de floresta de tabuleiros e campos naturais da RNV e região desde ~16.000 anos, utilizaram-se isótopos do C (12C, 13C e 14C) da matéria orgânica do solo e sedimentar, além de palinologia em sedimentos lacustres e terrestres. No estudo da dinâmica do ecótono floresta – campo, apresentam-se inferências preliminares sobre a evolução pedogenética dos Espodossolos associados ao campo, com ênfase às suas características físico-químicas, e também dos Argissolos, encontrados sob floresta. Finaliza-se com o estágio inicial de uma coleção de referência de fitólitos, bioindicador de vegetação utilizado em estudos paleoambientais, extraídos de plantas da floresta de tabuleiros da RNV.A equipe agradece todo o empenho dos funcionários e apoio logístico da Reserva Natural Vale, Linhares, Espírito Santo; à FAPESP através do projeto Temático 2011/00995-7 (ProjES); e ao CNPq – Universal 2012-5/470210, pelo aporte financeiro e a colaboração dos técnicos do Laboratório 14C, Liz Mary Bueno de Moraes e Thiago Casemiro Barrios de Campos, na preparação de amostras gasosas para a datação 14C.Peer Reviewe

Isotopes in pyrogenic carbon: a review

Pyrogenic carbon (PC; also known as biochar, charcoal, black carbon and soot) derived from natural and anthropogenic burning plays a major, but poorly quantified, role in the global carbon cycle. Isotopes provide a fundamental fingerprint of the source of PC and a powerful tracer of interactions between PC and the environment. Radiocarbon and stable carbon isotope techniques have been widely applied to studies of PC in aerosols, soils, sediments and archaeological sequences, with the use of other isotopes currently less developed. This paper reviews the current state of knowledge regarding (i) techniques for isolating PC for isotope analysis and (ii) processes controlling the carbon (<sup>13</sup>C and <sup>14</sup>C), nitrogen, oxygen, hydrogen and sulfur isotope composition of PC during formation and after deposition. It also reviews the current and potential future applications of isotope based studies to better understand the role of PC in the modern environment and to the development of records of past environmental change