359 research outputs found

    The Diffusion of Humans and Cultures in the Course of the Spread of Farming

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    The most profound change in the relationship between humans and their environment was the introduction of agriculture and pastoralism. [....] For an understanding of the expansion process, it appears appropriate to apply a diffusive model. Broadly, these numerical modeling approaches can be catego- rized in correlative, continuous and discrete. Common to all approaches is the comparison to collections of radiocarbon data that show the apparent wave of advance of the transition to farming. However, these data sets differ in entry density and data quality. Often they disregard local and regional specifics and research gaps, or dating uncertainties. Thus, most of these data bases may only be used on a very general, broad scale. One of the pitfalls of using irregularly spaced or irregularly documented radiocarbon data becomes evident from the map generated by Fort (this volume, Chapter 16): while the general east-west and south-north trends become evident, some areas appear as having undergone anomalously early transitions to farming. This may be due to faulty entries into the data base or regional problems with radiocarbon dating, if not unnoticed or undocumented laboratory mistakes.Comment: 20 pages, 5 figures, submitted to Diffusive Spreading in Nature, Technology and Society, edited by Armin Bunde, J\"urgen Caro, J\"org K\"arger, Gero Vogl, Chapter 1

    Establishment of Latin America Land Administration Network (LALAN)

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    Networks of academic and higher education institutions are proven platforms for knowledge sharing and experiences in education exchange. During the International Workshop LALA LADM+, 5-9 November 2018 in Quito Ecuador, organized by Universidad de las Fuerzas Armadas ESPE (ESPE University) Ecuador and Kadaster International together with Faculty ITC University of Twente from the Netherlands, Latin America Land Administration Network - LALAN was established. Representatives from seven countries from Latin American continent, Spain and the Netherlands were present at the workshop. The objective of this network is to: perform activities that can support capacity development and sharing knowledge in both fit-for-purpose and responsible land administration within the Latin America Land Administration Network of education institutions. This paper presents the process of establishment of LALAN, the network’s objective and planned activities for the coming period

    SEED: A framework for integrating ecological stoichiometry and eco‐evolutionary dynamics

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    Characterising the extent and sources of intraspecific variation and their ecological consequences is a central challenge in the study of eco‐evolutionary dynamics. Ecological stoichiometry, which uses elemental variation of organisms and their environment to understand ecosystem patterns and processes, can be a powerful framework for characterising eco‐evolutionary dynamics. However, the current emphasis on the relative content of elements in the body (i.e. organismal stoichiometry) has constrained its application. Intraspecific variation in the rates at which elements are acquired, assimilated, allocated or lost is often greater than the variation in organismal stoichiometry. There is much to gain from studying these traits together as components of an ‘elemental phenotype’. Furthermore, each of these traits can have distinct ecological effects that are underappreciated in the current literature. We propose a conceptual framework that explores how microevolutionary change in the elemental phenotype occurs, how its components interact with each other and with other traits, and how its changes can affect a wide range of ecological processes. We demonstrate how the framework can be used to generate novel hypotheses and outline pathways for future research that enhance our ability to explain, analyse and predict eco‐evolutionary dynamics

    Fluorescence excitation spectrum, lifetimes and photoisomerization of jet-cooled conformers of 1,1 '- bi(benzocyclobutylidene)

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    First measurements of fluorescence excitation spectra of the recently synthesized rigid stilbene analogue 1,1'- bi(benzocyclobutylidene) in a supersonic jet expansion show that, in contrast to the parent compound, both the trans- and the cis-conformer fluoresce under these conditions. The excitation energy dependence of fluorescence lifetimes indicates the onset of an efficient non-radiative decay channel above energy thresholds of 1340 cm(-1) and 990 cm(-1) for the trans- and cis-form, respectively, which is assigned to photoisomerization in the singlet state. From an RRKM analysis of the microcanonical rate coefficients an estimate of the high pressure limit of the thermal photoisomerization rate coefficient is obtained and compared with photoisomerization rate coefficients measured in low viscosity solution and in thermal vapor. There are strong indications that for this compound there are no dynamic or static solvent induced effects that lead to an anomalous acceleration of the reaction in solution

    Creating resilience to natural disasters through FFP land administration – an application in Nepal

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    Information on people to land relationships - documented in a land administration system - is crucial in any natural disaster response. This work explores how Fit-For-Purpose approaches and interventions in Land Administration (FFP LA) can be used in the process of earthquake recovery, to improve the community resilience. Four affected communities from the April 2015 earthquake in the Dolakha district of Nepal are considered. The massive 7.6 magnitude earthquake struck Nepal on 25 April 2015 and was followed by subsequent aftershocks, larger than magnitude 4. Due to landslides, ruptures and destabilization almost five hundred settlements are considered in the need for relocation. The Nepal Government experiences problems in the recovery and reconstruction assistance to the earthquake victims. This concerned housing affected communities, especially people without any land documents. Therefore, innovative land tools are used in the post-earthquake context to support the recordation and management of customary and informal land rights for communities. A case study method is applied in three communities in the Dolakha region to see if such FFP LA approaches on the ground support rebuilding efforts. The FFP LA approach involved participatory mapping through and with the community by identifying visible boundaries on high-resolution satellite imagery. The approach is successful and proves to be efficient and effective mapping land rights in the context of Disaster Risk Management (DRM) – because urgently required data on people to land relationships for reconstruction grants and decision making are available quickly and with the agreement of the citizens. Information gathered by grassroot surveyors in the project area revealed that one third of the earthquake victims cannot access the grants because the land title is missing. Currently not all land rights are recognized nor recorded in the Land Administration System (LAS) in Nepal and this is delaying the post-disaster recovery and reconstruction processes. For this reason, tenure rights of the poor and vulnerable have to be secured and access to land has to be guaranteed. The Nepalese government reacted and developed a FFP LA strategy and also made changes in the requirements to access the reconstruction grants

    An experimental test of the growth rate hypothesis as a predictive framework for microevolutionary adaptation

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    The growth rate hypothesis (GRH) posits that the relative body phosphorus content of an organism is positively related to somatic growth rate, as protein synthesis, which is necessary for growth, requires P-rich rRNA. This hypothesis has strong support at the interspecific level. Here, we explore the use of the GRH to predict microevolutionary responses in consumer body stoichiometry. For this, we subjected populations of the rotifer Brachionus calyciflorus to selection for fast population growth rate (PGR) in P-rich (HPF) and P-poor (LPF) food environments. With common garden transplant experiments, we demonstrate that in HP populations evolution toward increased PGR was concomitant with an increase in relative phosphorus content. In contrast, LP populations evolved higher PGR without an increase in relative phosphorus content. We conclude that the GRH has the potential to predict microevolutionary change, but that its application is contingent on the environmental context. Our results highlight the potential of cryptic evolution in determining the performance response of populations to elemental limitation of their food resources

    Functional diversity can facilitate the collapse of an undesirable ecosystem state

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    Biodiversity may increase ecosystem resilience. However, we have limited understanding if this holds true for ecosystems that respond to gradual environmental change with abrupt shifts to an alternative state. We used a mathematical model of anoxic–oxic regime shifts and explored how trait diversity in three groups of bacteria influences resilience. We found that trait diversity did not always increase resilience: greater diversity in two of the groups increased but in one group decreased resilience of their preferred ecosystem state. We also found that simultaneous trait diversity in multiple groups often led to reduced or erased diversity effects. Overall, our results suggest that higher diversity can increase resilience but can also promote collapse when diversity occurs in a functional group that negatively influences the state it occurs in. We propose this mechanism as a potential management approach to facilitate the recovery of a desired ecosystem state

    The chronostratigraphy of Late Pleistocene glacial and periglacial aeolian activity in the Tuktoyaktuk Coastlands, NWT, Canada

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    Aeolian periglacial sand deposits are common in the Tuktoyaktuk Coastlands of Western Arctic Canada. Regionally extensive and thick aeolian sand-sheet deposits have been observed in two major stratigraphic settings: within a sand unit characterized by large aeolian dune deposits; and interbedded with glaciofluvial outwash from the Laurentide Ice Sheet (LIS). Small, localized sand sheets have also been observed along the tops of sandy bluffs, within sequences of drained thermokarst lakes deposits and as an involuted veneer above buried basal ice of the LIS. On the basis of radiocarbon and optically stimulated luminescence (OSL) dates from preserved periglacial aeolian sand sheets and dunes a regional chronostratigraphy is presented which indicates that both extensive dunes and sand sheets accumulated mainly between ca 30 and 13 ka. A switch to dominantly sand-sheet aggradation at ca 14–13 ka, with sand sheets forming widely until ca 8 ka, is attributed to (a) surface armouring by glacial deposits associated with the advance of the LIS; and (b) amelioration of the climate from cold aridity. An absence of OSL dates between ca 8 and 1 ka suggests that sand sheets stabilized during much of the Holocene. Local sand-sheet aggradation during recent centuries has occurred near sandy bluffs and on the floors of drained thermokarst lakes. The OSL dates constrain the maximum extent of the LIS in the Tuktoyaktuk Coastlands to Marine Isotope Stage 2
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