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1.
Sci Total Environ ; 722: 137875, 2020 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-32199381

RESUMO

In September 2014, the Kashmir valley (north-west India) experienced a massive flood causing significant economic losses and fatalities. This disaster underlined the high vulnerability of the local population and raised questions regarding the resilience of Kashmiris to future floods. Although the magnitude of the 2014 flood has been considered unprecedented within the context of existing measurements, we argue that the short flow series may lead to spurious misinterpretation of the probability of such extreme events. Here we use a millennium-long record of past floods in Kashmir based on historical and tree-ring records to assess the probability of 2014-like flood events in the region. Our flood chronology (635 CE-nowadays) provides key insights into the recurrence of flood disasters and propels understanding of flood variability in this region over the last millennium, showing enhanced activity during the Little Ice Age. We find that high-impact floods have frequently disrupted the Kashmir valley in the past. Thus, the inclusion of historical records reveals large flood hazard levels in the region. The newly gained information also underlines the critical need to take immediate action in the region, so as to reduce the exposure of local populations and to increase their resilience, despite existing constraints in watershed management related to the Indus Water Treaty.

2.
Nat Ecol Evol ; 4(1): 40-45, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31844189

RESUMO

According to the competitive exclusion principle, species with low competitive abilities should be excluded by more efficient competitors; yet, they generally remain as rare species. Here, we describe the positive and negative spatial association networks of 326 disparate assemblages, showing a general organization pattern that simultaneously supports the primacy of competition and the persistence of rare species. Abundant species monopolize negative associations in about 90% of the assemblages. On the other hand, rare species are mostly involved in positive associations, forming small network modules. Simulations suggest that positive interactions among rare species and microhabitat preferences are the most probable mechanisms underpinning this pattern and rare species persistence. The consistent results across taxa and geography suggest a general explanation for the maintenance of biodiversity in competitive environments.

3.
Sci Rep ; 9(1): 14560, 2019 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-31601991

RESUMO

Landslides are frequently triggered by extreme meteorological events which has led to concern and debate about their activity in a future greenhouse climate. It is also hypothesized that dry spells preceding triggering rainfall may increase slope predisposition to sliding, especially in the case of clay-rich soils. Here we combined dendrogeomorphic time series of landslides and climatic records to test the possible role of dry spells and extreme downpours on process activity in the Outer Western Carpathians (Central Europe). To this end, we tested time series of past frequencies and return periods of landslide reactivations at the regional scale with a Generalized Linear Mixed (GLM) model to explore linkages between landslide occurrences and triggering climate variables. Results show that landslide reactivations are concentrated during years in which spring and summer precipitation sums were significantly higher than usual, and that triggering mechanisms vary between different types of landslides (i.e. complex, shallow or flow-like). The GLM model also points to the susceptibility of landslide bodies to the combined occurrence of long, dry spells followed by large precipitation. Such situations are likely to increase in frequency in the future as climate models predict an enhancement of heatwaves and dry spells in future summers, that would be interrupted by less frequent, yet more intense storms, especially also in mountain regions.

4.
J Vis Exp ; (143)2019 01 07.
Artigo em Inglês | MEDLINE | ID: mdl-30663651

RESUMO

Sheet erosion is among the crucial drivers of soil degradation. Erosion is controlled by environmental factors and human activities, which often lead to severe environmental impacts. The understanding of sheet erosion is, consequently, a worldwide issue with implications for both environment and economies. However, the knowledge on how erosion evolves in space and time is still limited, as well as its effects on the environment. Below, we explain a new dendrogeomorphological protocol for deriving eroded soil thickness (Ex) by acquiring accurate microtopographic data using both terrestrial laser scanning (TLS) and microtopographic profile gauges. Additionally, standard dendrogeomorphic procedures, dependent on anatomical variations in root rings, are utilized to establish the timing of exposure. Both TLS and microtopographic profile gauges are used to obtain ground surface profiles, from which Ex is estimated after the threshold distance (TD) is determined, i.e., the distance between the root and the sediment knickpoint, which allows defining the lowering of the ground surface caused by sheet erosion. For each profile, we measured the height between the topside of the root and a virtual plane tangential to the ground surface. In this way, we intended to avoid small-scale impacts of soil deformation, which may be due to pressures exerted by the root system, or by the arrangement of exposed roots. This may provoke small amounts of soil sedimentation or erosion depending on how they physically affect the surface runoff. We demonstrate that an adequate microtopographic characterization of exposed roots and their associated ground surface is very valuable to obtain accurate erosion rates. This finding could be utilized to develop the best management practices designed to eventually halt or perhaps, at least, lessen soil erosion, so that more sustainable management policies can be put into practice.


Assuntos
Meio Ambiente , Laboratórios
5.
Ann N Y Acad Sci ; 1436(1): 206-216, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-29968302

RESUMO

In this study, we analyze the linkage between atmosphere and ocean modes and winter flood variability over the 20th century based on long-term flow-discharge series, historical archives, and tree-ring records of past floods in the North Atlantic Basin (NAB). The most extreme winter floods occurred in 1936 and had strong impacts on either side of the Atlantic. We hypothesize that the joint effects of sea surface temperatures (SSTs) over the Atlantic and Pacific Oceans and the Arctic Oscillation (AO), which is closely related to the North Atlantic Oscillation, play a significant role when describing flood variability in North America and Europe since 1900. Statistical modeling supports the assumption that the response of flood anomalies over the NAB to AO phases is subsidiary of SST phases. Besides, we shed light on the extraordinarily winter flood of 1936 that was characterized by very high SSTs over both the Atlantic and Pacific (>98th percentile) and very low, negative values of AO (<1st percentile). This outstanding winter flood episode was most likely characterized by stratospheric polar vortex anomalies, which can usually be linked to an increased probability of storms in western and southwestern Europe and increased snowfall events in eastern North America. By assessing the flood anomalies over the NAB as a coupled AO and SST function, one could further the understanding of such large-scale events and presumably improve anticipation of future extreme flood occurrences.


Assuntos
Inundações/história , Modelos Teóricos , Estações do Ano , Oceano Atlântico , Europa (Continente) , História do Século XX , História do Século XXI , América do Norte
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