Paleo-ENSO impacted habitat availability for early modern humans

<p>In this study we synthesize terrestrial and marine proxy records spanning the last 620,000 years, to decipher pan-African climate variability, its drivers and potential linkages to hominin evolution. We find a tight correlation between moisture availability across Africa to Walker and Hadley Circulation variability that were most likely driven by changes in Earth´s eccentricity. Our results demonstrate that low latitude insolation rather than glacial-interglacial cyclicity was the predominant driver of pan-African climate change during the mid to late Pleistocene. We argue that these low-latitude climate processes governed the dispersion and evolution of vegetation, as well as mammals, in eastern and western Africa, ultimately by increasing resource-rich and stable ecotonal settings that have long thought to have been the preferred habitats of hominins.</p>

Preservação de fitólitos em solo no Parque Nacional do Iguaçu, Paraná

O acompanhamento da evolução da vegetação é importante para compreensão das possíveis modificações naturais na composição das formações florestais. O presente trabalho tem por objetivo abarcar a conservação da assembleia fitolítica em solos do Parque Nacional do Iguaçu/Paraná (PNI). Os fitólitos são micropartículas silicosas produzidas por gramíneas e algumas famílias arbóreas, que no final do ciclo de vida da planta são incorporados aos solos. Os procedimentos metodológicos pautaram-se em atividades de campo e de laboratório. Foram coletados 12 perfis de solo (trincheira 1, tubo de alumínio 1 e 10 tradagens). Os resultados tornaram possível a identificação e compreensão da distribuição fitolítica no PNI. Na discussão é abordada a correspondência das morfologias e comparação dos resultados obtidos, bem como a relação com a literatura. Identificou-se que as amostras que apresentaram os maiores valores no quantitativo fitolítico foram P1, T1, P4, P9, Fazenda Salinet, RPS, P8, P2, P5, P6, P3 e P7 respectivamente. Determinou-se que até as profundidades estudadas a vegetação arbórea e rasteira sempre coabitaram com prevalência do estrato arbóreo. No entanto, ressalta-se que ocorreram variações da vegetação com momentos de floresta mais e menos densa, e, com maior e menor sinais de umidade; tendo cada ponto amostrados peculiaridades. Concluiu-se que ocorreram diferenças tanto na Floresta Ombrófila Mista quanto na Floresta Estacional Semidecidual, bem como nos diferentes solos amostrados. Preservation of phytoliths on soil in the Iguaçu National Park, Paraná A B S T R A C T The monitoring evolution of vegetation is important to understand possible natural changes in the composition of forest formations. This work aims to cover the conservation of the phytolytic assembly in soils of the Iguaçu/Paraná National Park (PNI). Phytoliths are siliceous microparticles produced by grasses and some tree families, which at the end of the plant's life cycle are incorporated into the soil. The methodological procedures were based on field and laboratory activities. Twelve soil profiles were collected (trench 1, aluminum tube 1 and 10 edgings). The results made it possible to identify and understand the phytolytic distribution in the PNI. In the discussion, the correspondence of the morphologies and comparison of the results obtained is addressed, as well as the relationship with the literature. It was identified that the samples that presented the highest values in the phytolytic quantity were P1, T1, P4, P9, Fazenda Salinet, RPS, P8, P2, P5, P6, P3 and P7 respectively. It was determined that even the depths studied, tree and undergrowth vegetation always cohabited with prevalence of tree strata. However, it is noteworthy that vegetation variations occurred with moments of more and less dense forest, and with greater and lesser signs of humidity; having each point sampled peculiarities. It was concluded that differences occurred both in the Mixed Ombrophilous Forest and in the Seasonal Semideciduous Forest, as well as in the different sampled soils.Keywords: Conservation Unit, Proxy, Vegetation.

Fire on the Mountain. Disturbance and Regeneration in Deciduous and Conifer Forests. 20 Years of Experience

"Fire on the Mountain. Disturbance and Regeneration in Deciduous and Conifer Forests. 20 Years of Experience. Two test and monitoring sites in SW Germany (Forchtenberg) and Leghia (NW Romania) furnish insights to the regeneration modes after fire, clearing, burning, and cultivation -slash and burn - in a deciduous forest or after wildfire in a conifer stand. Forest maps and archivalia helped to reconstruct the forest history of the last 250 years of the Forchtenberg site, which as a heritage still influences the present situation. We could document the autonomous co- evolution of vegetation and soil over two decades. It was done by transects and mapping as well as by soil analysis and micromorphology. The role of soil animals for the weathering of charcoals became evident. The evolution of vegetation and soil after a wildfire could be studied on the Leghia site and compared with the Forchtenberg results. As the Leghia site was not cleared after the fire, it enabled us to follow the stages of decay and of regeneration, where conifers do not play a role. Moreover, one could investigate the effects of grass- and pasture fire, still active in the region. It also evidenced the necessary differentiation of charred material into wood- and grass coal. The indicator values of topsoil/soil surfaces are presented as well as those of charred material for the regeneration stages. Finally, we will discuss the fire risk in deciduous forests under a changing climate. Keywords: Forest disturbance, succession types, forest history, slash and burn, wild fire, charcoal taphonomy, fire risk. "

Bibliographical note on the syntaxonomy of the vegetation of Tlemcen, Hafir, Moutas and its reserve (North-western Algeria)

This study provides bibliographical note on the syntaxonomy of the vegetation of Tlemcen, Hafir, Moutas of North-western Algeria, including the associations and alliances of the different higher units found in the Hafir forest and the Moutas Reserve. In this work, we observed modifications of forest and pre-forest structures according to bioclimatic variations. However, in this region, the xericity of the climate is not the only factor destroying the plant cover, anthropization is also a degradation factor. While being aware of the negative consequences, man, through their abusive cultivation, illegal logging, overgrazing, urbanization, the depletion of natural resources;, inhibits the evolution of vegetation, participates in the replacement of a rich plant cover by another and more xerophytic plant cover with thorny and/or toxic feature. The landscape is dominated, for the most part, by open and degraded formations based on therophytes and chamaephytes, linked to Rosmarinetea and Cisto-Lavanduletea. The tree structures in Hafir and the Moutas reserve, still occupy only minimal areas subject to the destructive actions of man and his flock. These formations are still linked to the Quercetea ilicis. These ecosystems are marked by a regressive evolution (forest, pre-forest, scrub, scrubland and therophytization). Bangladesh J. Plant Taxon. 27(2): 345-358, 2020 (December)

Holocene vegetation history in the Northern Vosges Mountains (NE France): Palynological, geochemical and sedimentological data

Palynological data from the Northern Vosges Mountains (NVM) are very rare, unlike for the Southern and Central Vosges Mountains, where the past vegetation history is relatively well known. As a consequence, the beginning of human activities has never been clearly identified and dated in the NVM. In order to reconstruct the evolution of vegetation in this region, multiproxy studies (pollen, non-pollen palynomorphs, sedimentological and geochemical analyses) were conducted in two peatlands. Overall, the results, extending from about 9500 cal. BP to recent times, show a classical vegetation succession with local particularities resulting from human activities. In the La Horn peatland, a strong human impact related to pastoralism is attested from the late Bronze Age onwards. The second phase of human occupation, mainly characterized by crop cultures, begins during the Hallstatt period. The geochemical results (x-ray fluorescence) also highlight the presence of metallic elements, which, combined with significant quantities of carbonized particles, point to potential metal working. In the Kobert-Haut peatland, human occupation began much later (1500 cal. BP), but lasted from the Gallo-Roman period to the beginning of the Modern Period. Unlike for the vegetation history of the rest of the Vosges, Pinus remains a prevailing taxon throughout the Holocene in the NVM. Another particularity is the early establishment of Picea, long before the 18th to 19th century plantations.

Trend Evolution of Vegetation Phenology in China during the Period of 1981–2016

The trend of vegetation phenology dynamics is of crucial importance for understanding vegetation growth and its responses to climate change. However, it remains unclear how the trends of vegetation phenology changed over the past decades. By analyzing phenology data including start (SOS), end (EOS) and length (LOS) of growth season with the Ensemble empirical mode decomposition (EEMD), we revealed the trend evolution of vegetation phenology in China during 1981-2016. Our study suggests that: (1) On the national scale, with EEMD method, the change rates of SOS and LOS were increasing with time, while that of EOS was decreasing. Moreover, the EEMD rates of SOS and LOS exceeded the linear rates in the early-2000s, while that of EOS dropped below the linear rate in the mid-1980s. (2) For each phenological event, the shifted trends took up a large area (~30%), which was close to the sum of all monotonic trends, but more than any monotonic trend type. The shifted trends mainly occurred in the north-eastern China, eastern Qinghai-Tibetan Plateau, eastern Sichuan Basin, North China Plain and Loess Plateau. (3) For each phenological event, the areas in the high-latitude experienced the contrary trends to the other. The amplitude and frequencies of phenology variation in the mid-latitude were stronger than those in the high-latitude and low-latitude. Meanwhile, LOS in the high-latitude was induced by SOS. (4) For each phenological event, the trend evolution varying with longitudes can be divided into eastern region (east of 121°E), central region (92°E–121°E) and western region (west of 92°E) based on the evolution of trends varying with longitudes. The east experienced a delayed SOS and a shorten LOS, which was different from the other areas. The magnitude of delayed trends in EOS and the prolonged trends in LOS were stronger from east to west as longitudes changes. The variation characteristics of LOS with longitude were mainly caused by SOS in the eastern region and by SOS and EOS together in the western and central region. (5) Each land cover types, except Needleleaf Forests, experienced the same trends. For most land cover types, the advance of SOS, delay of EOS and extension of LOS began in the 1980s, the 1990s, and the 1990s, respectively and enhanced several times. Moreover, the magnitudes of Grasslands in SOS and Evergreen Broadleaf Forest in EOS were much greater than the others, while that of croplands was the smallest in each phenological event. Our results showed that the analysis of trend evolution with nonlinear method is very important to accurately reveal the variation characteristics of phenology trends and to extract the inherent trend shifts.

Temporal and Spatial Evolution of Vegetation Coverage in the Mianyuan River Basin Influenced by Strong Earthquake Disturbance

The 2008 Wenchuan earthquake caused significant economic losses and degradation of regional ecosystems, including the terrestrial vegetation. Since the vegetation root system can enhance the soil’s anti-erosion capacity and therefore mitigate the occurrence of slope instabilities, it is beneficial to study the spatial and temporal evolution of vegetation for a long-term assessment of co-seismic secondary disasters. The Mianyuan River Basin, an uninhabited area passing through an active fault located in the earthquake-affected region, was selected as the study area. The Normal Difference Vegetation Index (NDVI) was calculated using remote sensing images from 1994 to 2017 to analyze the process of vegetation growth, loss, fluctuation and recovery. Statistical results suggest that the area in the middle and lower reaches, near the river network, and with a slope of 30 to 40 degrees were variable regions, showing more significant vegetation destruction during the earthquake and faster repair after the seismic event. Besides, vegetation near the fault was damaged more severely after the earthquake, but the active fault did not play an essential role in the vegetation recovery period. In the Mianyuan River Basin, vegetation experienced a volatility period (5 plus or minus one year) before entering the recovery period. In 8 to 9 years after the earthquake, the surficial vegetation could recover to the state before the earthquake.