108,839 research outputs found
Inverse meta-modelling to estimate soil available water capacity at high spatial resolution across a farm
Geo-referenced information on crop production that is both spatially- and temporally-dense would be useful for management in precision agriculture (PA). Crop yield monitors provide spatially but not temporally dense information. Crop growth simulation modelling can provide temporal density, but traditionally fail on the spatial issue. The research described was motivated by the challenge of satisfying both the spatial and temporal data needs of PA. The methods presented depart from current crop modelling within PA by introducing meta-modelling in combination with inverse modelling to estimate site-specific soil properties. The soil properties are used to predict spatially- and temporally-dense crop yields. An inverse meta-model was derived from the agricultural production simulator (APSIM) using neural networks to estimate soil available water capacity (AWC) from available yield data. Maps of AWC with a resolution of 10 m were produced across a dryland grain farm in Australia. For certain years and fields, the estimates were useful for yield prediction with APSIM and multiple regression, whereas for others the results were disappointing. The estimates contain âimplicit informationâ about climate interactions with soil, crop and landscape that needs to be identified. Improvement of the meta-model with more AWC scenarios, more years of yield data, inclusion of additional variables and accounting for uncertainty are discussed. We concluded that it is worthwhile to pursue this approach as an efficient way of extracting soil physical information that exists within crop yield maps to create spatially- and temporally-dense dataset
Hotspots: Exotic mosquito risk profiles for New Zealand
This document reports the main findings of the first systematic, spatial analyses of risks
to New Zealand associated with exotic mosquitoes of current public health concern
Mesoscale mapping of sediment source hotspots for dam sediment management in data-sparse semi-arid catchments
Land degradation and water availability in semi-arid regions are interdependent challenges for management that are influenced by climatic and anthropogenic changes. Erosion and high sediment loads in rivers cause reservoir siltation and decrease storage capacity, which pose risk on water security for citizens, agriculture, and industry. In regions where resources for management are limited, identifying spatial-temporal variability of sediment sources is crucial to decrease siltation. Despite widespread availability of rigorous methods, approaches simplifying spatial and temporal variability of erosion are often inappropriately applied to very data sparse semi-arid regions. In this work, we review existing approaches for mapping erosional hotspots, and provide an example of spatial-temporal mapping approach in two case study regions. The barriers limiting data availability and their effects on erosion mapping methods, their validation, and resulting prioritization of leverage management areas are discussed.BMBF, 02WGR1421A-I, GROW - Verbundprojekt SaWaM: Saisonales Wasserressourcen-Management in Trockenregionen: Praxistransfer regionalisierter globaler Informationen, Teilprojekt 1DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische UniversitÀt Berli
Enhancing the Guidance of the Intentional Model "MAP": Graph Theory Application
The MAP model was introduced in information system engineering in order to
model processes on a flexible way. The intentional level of this model helps an
engineer to execute a process with a strong relationship to the situation of
the project at hand. In the literature, attempts for having a practical use of
maps are not numerous. Our aim is to enhance the guidance mechanisms of the
process execution by reusing graph algorithms. After clarifying the existing
relationship between graphs and maps, we improve the MAP model by adding
qualitative criteria. We then offer a way to express maps with graphs and
propose to use Graph theory algorithms to offer an automatic guidance of the
map. We illustrate our proposal by an example and discuss its limitations.Comment: 9 page
TWINLATIN: Twinning European and Latin-American river basins for research enabling sustainable water resources management. Combined Report D3.1 Hydrological modelling report and D3.2 Evaluation report
Water use has almost tripled over the past 50 years and in some regions the water demand already
exceeds supply (Vorosmarty et al., 2000). The world is facing a âglobal water crisisâ; in many
countries, current levels of water use are unsustainable, with systems vulnerable to collapse from even
small changes in water availability. The need for a scientifically-based assessment of the potential
impacts on water resources of future changes, as a basis for society to adapt to such changes, is strong
for most parts of the world. Although the focus of such assessments has tended to be climate change,
socio-economic changes can have as significant an impact on water availability across the four main
use sectors i.e. domestic, agricultural, industrial (including energy) and environmental. Withdrawal
and consumption of water is expected to continue to grow substantially over the next 20-50 years
(Cosgrove & Rijsberman, 2002), and consequent changes in availability may drastically affect society
and economies.
One of the most needed improvements in Latin American river basin management is a higher level of
detail in hydrological modelling and erosion risk assessment, as a basis for identification and analysis
of mitigation actions, as well as for analysis of global change scenarios. Flow measurements are too
costly to be realised at more than a few locations, which means that modelled data are required for the
rest of the basin. Hence, TWINLATIN Work Package 3 âHydrological modelling and extremesâ was
formulated to provide methods and tools to be used by other WPs, in particular WP6 on âPollution
pressure and impact analysisâ and WP8 on âChange effects and vulnerability assessmentâ. With an
emphasis on high and low flows and their impacts, WP3 was originally called âHydrological
modelling, flooding, erosion, water scarcity and water abstractionâ. However, at the TWINLATIN
kick-off meeting it was agreed that some of these issues resided more appropriately in WP6 and WP8,
and so WP3 was renamed to focus on hydrological modelling and hydrological extremes.
The specific objectives of WP3 as set out in the Description of Work are
The Crab Nebula at 1.3 mm: evidence for a new synchrotron component
We present the results of 1.3 mm observations of the Crab Nebula, performed
with the MPIfR bolometer arrays at the IRAM 30-m telescope. The maps obtained,
of unprecedented quality at these wavelengths, allow a direct comparison with
high-resolution radio maps. Although the spatial structure of the Crab Nebula
does not change much from radio to millimetre wavelengths, we have detected
significant spatial variations of the spectral index between 20 cm and 1.3 mm.
The main effect is a spectral flattening in the inner region, which can be
hardly explained just in terms of the evolution of a single population of
synchrotron emitting electrons. We propose instead that this is the result of
the emergence of a second synchrotron component, that we have tried to extract
from the data. Shape and size of this component resemble those of the Crab
Nebula in X rays. However, while the more compact structure of the Crab Nebula
in X rays is commonly regarded as an effect of synchrotron downgrading, it
cannot be explained why a similar structure is present also at mm wavelengths,
where the electron lifetimes far exceed the nebular age. Our data, combined
with published upper limits on spatial variations of the radio spectral index,
also imply a low-energy cutoff for the distribution of electrons responsible
for this additional synchrotron component. Although no model has been developed
so far to explain the details of this component, one may verify that the total
number of the electrons responsible for it is in agreement with what predicted
by the classical pulsar-wind models, which otherwise are known to fail in
accounting for the number of radio emitting electrons. We have also detected a
spectral steepening at mm wavelengths in some elongated regions, whose
positions match those of radio synchrotron filaments.Comment: 10 pages, Latex, 8 figures, JPEG, given separately Submitted to
Astronomy and Astrophysic
How to enhance crop production and nitrogen fluxes? A result-oriented scheme to evaluate best agri-environmental measures in Veneto Region, Italy
The cost-effectiveness of adopting agri-environmental measures (AEMs) in Europe, which combine agricultural productions with reduced N losses, is debated due to poorly targeted site-specific funding that is allocated regardless of local variability. An integrated DAYCENT model-GIS platform was developed combining pedo-climatic and agricultural systems information. The aim was to evaluate best strategies to improve N fluxes of agro-ecosystems within a perspective of sustainable intensification. Indicators of agronomic efficiency and environmental quality were considered. The results showed that agronomic benefits were observed with a continuous soil cover (conservation agriculture and cover crops), which enhanced nitrogen use efficiency (+17%) and crop yields (+34%), although in some cases these might be overestimated due to modelling limitations. An overall environmental improvement was found with continuous soil cover and long-term change from mineral to organic inputs (NLeach 45 Mg ha 121), which were effective in the sandy soils of western and eastern Veneto with low SOM, improving the soil-water balance and nutrients availability over time. Results suggest that AEM subsidies should be allocated at a site-specific level that includes pedo-climatic variability, following a result-oriented approach
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