Browsing by Author "Boski, Tomasz"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- Characteristics of organic matter sources from Guadiana Estuary salt marsh sediments (SW Iberian Peninsula)Publication . Kumar, Mukesh; Boski, Tomasz; Gonzalez-Vila, Francisco J.; Jimenez-Morillo, Nicasio T.; Gonzalez-Perez, Jose A.Estuaries are dynamic interfaces between land, rivers and the ocean that play major roles in the global carbon cycle. These coastal wetlands store huge amounts of organic carbon (OC), commonly known as "blue carbon" and excellent places to study C cycling. The Guadiana river estuary is among the most important tidal salt marshes in the South - Iberian coastal margin. Here, a detailed organic geochemical study is described that includes the identification of sedimentary OM composition at a molecular and isotopic level. Total organic carbon content (TOC) of core sediments ranged from 0.39 to 2.23% and stable carbon isotope composition (delta C-13) also showed a wide range between -22.4 and -27.0 parts per thousand. A(13)C depletion trend observed from the surface to bottom in the core sediments profiles, reflects loss of labile biogenic C-13 enriched compounds i.e. polysaccharides and a selective preservation of more depleted compounds with depth i.e. lignin and lipids in the core sediments. Series of nalkanes were found in the range from C-10 to C-31. Carbon preference index ratio (CPI) calculated for long-chain n-alkanes (C-24-C-31) that ranged between 1.17 and 1.94 reflecting diverse OM inputs to the sediments. A study of the lignin-derived phenolic composition pointed to a recalcitrant OM derived from both gymnosperm and angiosperm plants. Moreover, high abundance of vinyl phenol and vinyl guaiacol points to a dominant contribution of lignins from grasses and aquatic macrophytes to the sediments. A well-resolved series of long-chain linear alkyl benzenes (LABs from C-4 to C-22) were recorded in all core sediment samples indicating direct discharge of untreated domestic and/or industrial effluents to the estuary. Polycyclic aromatic hydrocarbons (PAHs) with more than 3 rings reflects the pyrogenic origin of a portion of the sedimentary OM. This study highlights the importance of different OM sources to the lower Guadiana estuarine sediments and contributes to a better knowledge about its origin, dynamics and fate.
- Drought, fire and grazing precursors to large-scale pine forest declinePublication . Connor, Simon; Araújo, João; Boski, Tomasz; Gomes, Ana; Gomes, Sandra D.; Leira, Manel; Freitas, Maria da Conceição; Andrade, Cesar; Morales‐Molino, César; Franco‐Múgica, Fátima; Akindola, Rufus B.; Vannière, BorisAim Temperate forests are currently facing multiple stresses due to climate change, biological invasions, habitat fragmentation and fire regime change. How these stressors interact with each other influences how, when and whether ecosystems recover, or whether they adapt or transition to a different ecological state. Because forest recovery or collapse may take longer than a human lifetime, predicting the outcomes of different stressor combinations remains difficult. A clearer vision of future forest trajectories in a changing world may be gained by examining collapses of forests in the past. Here, we use long-term ecological data to conduct a post-mortem examination of the decline of maritime pine forests (Pinus pinaster Ait.) on the SW Iberian Peninsula 7000-6500 years ago. Location Portugal and Spain. Methods We compared four palaeoecological records-two with pine declines and two without-using a multiproxy approach. Bioclimatic differences between the four sites were explored. Proxies for past vegetation and disturbance (fire and grazing) were compared with independent palaeoclimatic records. We performed functional traits analysis and used phase plots to examine the causes of pine decline. Results The pine decline represents a critical transition in SW Iberia, which lies close to maritime pine's bioclimatic limits. Prolonged drought likely killed trees and suppressed the fires that normally stimulate pine germination and pinewood recovery. Increased grazing pressure facilitated the rapid spread of resprouter shrubs. These competed with pine trees and ultimately replaced them. Our data highlight complex interactions between climate, fire, grazing and forest resilience. Main Conclusions The pine decline occurred at least a century after post-fire resprouters overtook obligate seeders in the vegetation, constituting an early-warning signal of forest loss. Fire suppression, resprouter encroachment and grazing may threaten the persistence of Mediterranean forests as droughts become more frequent and extreme.
- Paleolandscape evolution along the coasts of the Baixo Alentejo (Portugal) during the quaternaryPublication . Goy, J.L.; Roquero, E.; Zazo, C.; Moura, Delminda; Dabrio, C.J.; Boski, Tomasz; Martínez-Graña, A.; Lario, J.; Bardají, T.A detailed geomorphological mapping allowed to understand the complex relationships interplayed between local tectonics and sedimentation across the coastal area of the Baixo Alentejo (Portugal) all along the Quaternary. Different outcrops of coastal sediments between Sines and Vilanova de Milfontes permitted to reconstruct a general sequence of up to fifteen stair-cased marine terraces, while wide sequences of alluvial fans develop in the hinterland. The distinct geomorphological disposition of these alluvial fans together with the presence/absence of marine terraces, have allowed to define different phases of paleolandscape evolution based both in sea level changes and differential uplift. A dune system has been attributed to MIS 5e in basis of OSL, and C-14 and U-series dating permitted the adscription of a beach unit to MIS 5. These data allowed to stablish the relative chronology of the entire marine terrace sequence and to determine the vertical movement rates along the studied coastal area. The results give values ranging from slight uplift (+0.015mm/a) to subtle subsidence (-0.030 mm/a), coinciding with other author's determinations.
- Projections of maximum tidal inundation limits of estuaries and lagoons of the south Algarve, forced by mean sea level rise: RCP8.5 scenarioPublication . Sampath, Dissanayake; Boski, Tomasz; Moura, Delminda; Veiga-Pires, C.In the present study, we adopted the Hybrid Estuarine Sedimentation Model to simulate the estuarine and lagoon evolution in the South Algarve region due to projected mean sea level rise (MSLR) and sediment deficit scenarios during the 21st century. Thus, we forecasted morphological evolution of six large and medium size estuaries (Guadiana Alcantarilha, Arade, Gilão, Quarteira River, Alvor and a coastal lagoon system (Ria Formosa lagoon) due to the imposed scenarios of MSLR. The projected digital elevation models were used to identify the maximum tidal limits of each system by the year 2100. According to the results, in all cases, saltmarsh habitats and sand flats will be affected severely in response to upper-limit of RCP8.5 scenario of MSLR by 2100. The conjugation of the increase of the mud-flat area and the decrease of saltmarshes will result in the reduction of habitats and then of biodiversity. Habitats associated with the Ria Formosa coastal lagoon and the Guadiana estuary are highly vulnerable to the worst case scenario of MSLR (90 cm higher relative to the year 2011). Agricultural and aquaculture areas in all study areas will be affected due to the landward translation limits of the intertidal areas. Accordingly, it would be advisable to adopt measures to minimize the socioeconomic impacts and loss of ecosystem services in the South Algarve due to climate change driven MSLR during the 21st century and beyond while taking adaptation actions to prevent the loss of environmentally sensitive habitats like salt marshes and sand dunes.