180 research outputs found
Relationships of stable carbon isotopes, plant water potential and growth: an approach to asses water use efficiency and growth strategies of dry land agroforestry species
No full textThe relationships between annual wood stable carbon isotope composition (delta C-13), dry season midday plant water potential, and annual growth rate were investigated to asses the ability of agroforestry species to adapt to climate changes. 6-8 stem disks from four co-occurring species (Acacia senegal, A. seyal, A. tortilis and Balanites aegyptiaca) were collected for radial growth measurements using tree-ring analysis spanning 1930-2003. Annual delta C-13 was measured on three tree disks per species for the period 1970-2002. Midday plant water potential was measured during the dry season. Annual radial growth and midday plant water potential ranged from 0.27 to 9.12 mm and -1.0 to -5.0 MPa, respectively, with statistically significant differences. After correcting annual wood delta C-13 for atmospheric changes in delta C-13, carbon isotopic composition ranged from -22.22 to -26.58aEuro degrees. Relationships between delta C-13, radial growth and plant water potentials revealed the interaction of water availability, stomatal conductance, delta C-13 values and growth. Two contrasting water use strategies and competitive advantages can be distinguished. Species with lower mean delta C-13 values (A. senegal and A. seyal) show high plant water potential and, hence, better growth during moist years. Thus, they indicate low water use efficiency (WUE) and opportunistic water use strategy. On the other hand, species with lower water potentials (A. tortilis and B. aegyptiaca) showed relative better growth performance and less increase in delta C-13 in drought years, reflecting their high WUE and conservative water use strategy. These results suggest that delta C-13 in tree rings can be useful in estimating historic changes in plant WUE and hence in screening drought tolerant species in the face of expected climate changes, as well as for assessing the functional diversity and risk reduction in mixed vegetation.German Academic Exchange Service (DAAD
Nitrous oxide emissions from agricultural land use in Germany - a synthesis of available annual field data
No full textThe nations that have ratified the Kyoto Protocol must set up an appropriate national inventory on N2O emissions from agricultural land use, in order to report properly on the achievements made in reducing greenhouse-gas emissions. The search for the appropriate method is a controversial topic as it is subject to high uncertainty in particular associated to the upscaling from site measurements. In this study, all available data from Germany on annual N2O-emission rates derived from field experiments of at least an entire year are summarized. From each study, only differences in soil properties on N input qualified as an individual data set. Under these premises, 101 treatments from 27 sites were found equally spread across Germany. The annual N application ranged from 0 to 400 kg N ha(-1) and the annual emission rates from 0.04 to 17.1 kg ha(-1). Annual emission factors (EFs), uncorrected for background emission, varied considerably from 0.18% to 15.54% of N applied. There was no nationwide correlation found for the relationship between N2O losses and N application, soil C, soil N, soil texture, or soil pH. However, site-specific trends in the relationship between emission factor and mean soil aeration status, as expressed by the soil type and/or mean climatic conditions, were revealed. Regularly water-logged soils were characterized by low emission factors as were soils from the drier regions (2O emissions from agricultural land use on the national scale, there must be a biological adaptation to mean site conditions, i.e., different microbial communities react differently to similar actual conditions in terms of N2O dynamics. Regardless of the point of view, the chapter on N2O Soil dynamics cannot be closed yet, and new additional model concepts, process studies, and field measurements are needed. [References: 59
The Victorian Newsletter (Spring 1973)
No full textThe Victorian Newsletter is sponsored for the English X Group of the Modern Language Association by New York University and Queens College, City University of New York.The State of Victorian Studies: 1962-1972 - Introductory Remarks / Robert A. Colby -- Victorian Nonfiction Prose / G. B. Tennyson -- Victorian Poetry / R. C. Tobias -- Victorian Fiction / Lionel Stevenson -- Emily Brontë and the Responsible Imagination / Victor A. Neufeldt -- Wave and Fire Imagery in Tennyson's Idylls / Henry Kozicki -- Tennyson and the Spasmodics / Joseph J. Collins -- Recent Publications: A Selected List / Arthur F. Minerof -- English X New
Reporting adaptation through the biennial transparency report: A practical explanation of the guidance
No full textAcknowledging that climate action is urgently needed, the Paris Agreement – adopted in 2015 – establishes a series of long-term goals across climate change mitigation, adaptation, and the provision of support. Unlike under its predecessor,the Kyoto Protocol, the contributions of countries party to the agreement towards achieving the Paris Agreement’s goals are self-determined, i.e. countries decide on how and to what extent they reduce their national GHG emissions, implement adaptation, and provide support to developing countries. Under the Paris Agreement, countries submit their new pledges to the UNFCCC via their Nationally Determined Contributions (NDCs), which they are able to renew every five years.The initial contributions pledged by countries in the first round of NDCs are not of sufficient magnitude to reach the goals of the Paris Agreement (UNEP, 2019). However, as the approach adopted in the Paris Agreement is centred around countries raising their levels of ambition over time, countries that have signed the agreement are expected to enhance the size and scope of their contributions in each five-year cycle. For this approach to work in practice, it is recognised that mutual trust will need to be built between countries as a means of enhancing the ambition of collective action. In order to establish this mutual trust, and to allow collective progress towards these goals to be monitored, the importance of ensuring transparency in actions and reporting is emphasized across the Paris Agreement.For this purpose, the Paris Agreement under Article 13 establishes the Enhanced Transparency Framework (ETF) for action and support. The ETF establishes a new set of rules and procedures related to transparency that are intended improvethe quality of country reporting to the UNFCCC. When it comes into force in 2024, the structure established by the ETF will form the basis of the Paris Agreement’s transparency arrangements that, for countries that have signed the greement,will replace the Measurement, Reporting, and Verification (MRV) system that provides the basis for transparency under the convention.The design and structure of the ETF is built upon the experiences of the MRV system that it supersedes. However, an important difference between the two systems is that the ETF will be applicable to all parties (i.e. the ETF’s rules and requirements will be equally applicable across annex I and non-annex I Parties). Continuing to acknowledge the differences in the capacity that countries have to adhere to rules and requirements, the ETF allows developing countries that need it in light of their capacities, to exercise a certain amount of flexibility regarding the extent to which they report against the ETF’s mandatory reporting requirements
Geoecological drivers of cerrado heterogeneity and 13C natural abundance in oxisols after land-use change Fatores geoecológicos das diferentes formações de cerrados - uma hipótese baseada em abundância natural de 13C e fotografia aérea
No full textThe 13C natural abundance technique was applied to study C dynamics after land-use change from native savanna to Brachiaria, Pinus, and Eucalyptus in differently textured Cerrado Oxisols. But due to differences in the d13C signatures of subsoils under native savanna and under introduced species, C substitution could only be calculated based on results of cultivated soils nearby. It was estimated that after 20 years, Pinus C had replaced only 5 % of the native C in the 0-1.2 m layer, in which substitution was restricted to the top 0.4 m. Conversely, after 12 years, Brachiaria had replaced 21 % of Cerrado C to a depth of 1.2 m, where substitution decreased only slightly throughout the entire profile. The high d13C values in the subsoils of the cultivated sites led to the hypothesis that the natural vegetation there had been grassland rather than Cerrado sensu stricto, in spite of the comparable soil and site characteristics and the proximity of the studied sites. The hypothesis was tested using aerial photographs of 1964, which showed that the cultivated sites were located on a desiccated runoff head. The vegetation shift to a grass-dominated savanna formation might therefore have occurred in response to waterlogging and reduced soil aeration. A simple model was developed thereof, which ascribes the different Cerrado formations mainly to the plant-available water content and soil aeration. Soil fertility is considered of minor significance only, since at the studied native savanna sites tree density was independent of soil texture or nutrient status.A abundância natural de 13C foi utilizada para estudar a dinâmica de carbono em latossolos de textura média e argilosa após plantação de pastagens (Brachiaria decumbens) e reflorestamentos (Pinus caribaea e Eucalyptus citriodora). Considerando as diferenças de d13C nos subsolos das savanas nativas e das espécies introduzidas, pôde-se calcular a substituição de carbono somente para os solos argilosos, baseando-se em resultados publicados de d13C em solos adjacentes. Estimou-se que somente 5 % do carbono nativo foram substituidos após 20 anos de plantação com pinus na camada de 0-1,2 m, ficando a substituição restrita aos primeiros 0,4 m do solo. Na pastagem de 12 anos, 21 % do carbono novo foram introduzidos na camada de de 0-1,2 m, sendo a substituição diminuída gradativamente pelo perfil inteiro. De acordo com os altos valores de d13C nos subsolos das áreas cultivadas, levantou-se a hipótese de que a vegetação natural teria sido de campo limpo em vez de cerrado stricto sensu apesar da semelhança dos solos e da proximidade dos sítios estudados. A hipótese foi testada com fotos aéreas de 1964, mostrando que as áreas cultivadas encontravam-se numa cabeceira de escoamento ressecada. Portanto, a vegetação dominada por gramíneas pode ter sido induzida pela hidromorfia e pela baixa aeração do solo. Com base nessas observações, desenvolveu-se um modelo simplificado, atribuindo às diferentes formações de cerrados o acesso de água para as plantas e a aeração do solo. A fertilidade do solo foi considerada de menor importância porque a densidade arbórea das áreas de cerrados encontrava-se independente da textura ou do nível de nutrientes dos solos
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