Alexis M.A.,French National Institute for Agricultural Research |
Rumpel C.,French National Institute for Agricultural Research |
Knicker H.,TU Munich |
Leifeld J.,Swiss Federal Research Station for Agroecology and Agriculture |
And 4 more authors.
Organic Geochemistry | Year: 2010
Vegetation fires profoundly alter the C cycle of terrestrial ecosystems, notably through the potential formation of highly stable pyrogenic structures. Fire-induced changes in the structure of organic matter (OM) have been studied mainly under controlled laboratory conditions. The objective of this work was to characterise changes in OM chemistry occurring in the litter layer of a scrub-oak ecosystem subjected to a prescribed fire. Maximum temperatures reached during the fire were monitored with thermo-sensitive paint. Litter samples collected before and after the fire were subjected to size fractionation, each size fraction being divided on the basis of visual observation into burnt and unburnt components, i.e. black and brown, respectively. All fractions were analysed for C and N contents and stable carbon isotopic composition. Shifts in the composition of >2mm fraction components were evaluated using solid-state 13C nuclear magnetic resonance (NMR) spectroscopy and differential scanning calorimetry (DSC).The effects of charring were evaluated through comparisons of black vs. brown post-fire litter in >370°C plots. Comparison of bulk pre- vs. post-fire litter proved unreliable because of the complicating effect of fresh litter fall during the fire event. Charring significantly increased the litter C content by 115-142mgg-1 and significantly decreased the δ13C value by an average of 0.8‰. The NMR and DSC analyses indicated that O-alkyl compounds were preferentially lost vs. aryl and alkyl compounds. This suggests a preferential loss of cellulose components and a relative preservation of lignin and lipids. However, the charred litter samples had a low degree of condensation vs. a graphitic-like model. The findings suggest that leaf-derived charcoal produced during natural vegetation fires does not contribute much to the highly stable fraction of pyrogenic OM. © 2010 Elsevier Ltd.
Wichern F.,University of Kassel |
Wichern F.,KS KALI GmbH |
Mayer J.,Swiss Federal Research Station for Agroecology and Agriculture |
Joergensen R.,University of Kassel |
Muller T.,University of Hohenheim
Plant and Soil | Year: 2010
To investigate the amount and fate of root-derived C and N, often tracer techniques are used, where plants are labelled with isotopes. In the present study, we evaluated the suitability of the cotton wick method for in situ labelling of peas (Pisum sativum L.) and oats (Avena sativa L.) with 13C and 15N simultaneously. With two greenhouse experiments we investigated how the wick method and aqueous urea and sugar solutions at a variety of concentrations affected plant development. In addition, we investigated the distribution of 13C and 15N in plants from column experiments under outdoor conditions. Solution was taken up by the plant from a small vial connected to the stem by a cotton wick which was passed through a hole in the stem of the plants. Generally, solution uptake varied between individual plants and decreased with increasing sugar concentrations. Below-ground, above-ground and total plant dry matter, were not significantly affected by the wick method and the applied solutions. Mixtures of aqueous glucose solutions at 2 to 4% and aqueous urea solutions at 1% are useful carriers of 13C and 15N. However, in the investigated plants isotopes were not homogeneously distributed among plant parts. Above-ground plant biomass was preferentially enriched with 13C and 15N, whereas below-ground plant biomass was generally lower enriched. Moreover, isotope distribution ratio of individual plants varied considerably, independent of plant part or timing of labelling. This must be taken into account when estimating root-derived C and N. Future studies comparing labelling methods need to present the isotope distribution ratios among plant parts to allow a true comparison of the methods and the evaluation of their suitability for estimating rhizodeposition. © Springer Science+Business Media B.V. 2009.
Diekotter T.,ETH Zurich |
Diekotter T.,Justus Liebig University |
Baveco H.,Wageningen University |
Arens P.,Wageningen University |
And 8 more authors.
Landscape Ecology | Year: 2010
Habitat fragmentation has been generally regarded detrimental to the persistence of many species, especially those with limited dispersal abilities. Yet, when exactly habitat elements become functionally disconnected very much depends on the dispersal ability of a species in combination with the landscape's composition in which it occurs. Surprisingly, for many small and ground-walking generalists knowledge at what spatial scale and to what extent landscape structure affects dispersal is very scarce. Because it is flightless, the bush cricket Pholidoptera griseoaptera may be regarded susceptible to fragmentation. We applied habitat occupancy surveys, population genetic analyses and movement modelling to investigate the performance of P. griseoaptera in an agricultural mosaic landscape with suitable habitat patches of varying size and isolation. Despite its presumed dispersal limitation we could show that P. griseoaptera occupied the majority of suitable habitats, including small and isolated patches, showed a very low and non-significant genetic differentiation (FST = 0.0072) and, in the model, managed to colonize around 73% of all suitable habitat patches within one generation under weak and strong landscape-effect scenarios. We conclude that P. griseoaptera possesses the behavioural attributes (frequent inter-patch dispersal) necessary to persist in this landscape characterized by a patchy distribution of habitat elements. Yet, sound recommendations to landscape planning and conservation require more research to determine whether this represents a general behaviour of the species or a behavioural adaptation to this particular landscape. © 2009 Springer Science+Business Media B.V.
Kleijn D.,Wageningen University |
Kleijn D.,Radboud University Nijmegen |
Kohler F.,Wageningen University |
Baldi A.,Hungarian Academy of Sciences |
And 11 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2012
Worldwide agriculture is one of the main drivers of biodiversity decline. Effective conservation strategies depend on the type of relationship between biodiversity and land-use intensity, but to date the shape of this relationship is unknown. We linked plant species richness with nitrogen (N) input as an indicator of landuse intensity on 130 grasslands and 141 arable fields in six European countries. Using Poisson regression, we found that plant species richness was significantly negatively related to N input on both field types after the effects of confounding environmental factors had been accounted for. Subsequent analyses showed that exponentially declining relationships provided a better fit than linear or unimodal relationships and that this was largely the result of the response of rare species (relative cover less than 1%). Our results indicate that conservation benefits are disproportionally more costly on high-intensity than on lowintensity farmland. For example, reducing N inputs from 75 to 0 and 400 to 60 kg haK1 yrK1 resulted in about the same estimated species gain for arable plants. Conservation initiatives are most (cost-)effective if they are preferentially implemented in extensively farmed areas that still support high levels of biodiversity. © 2008 The Royal Society.
Pokhrel M.R.,Agriculture and Forestry University |
Thapa R.B.,Tribhuvan University |
Mandal C.K.,Tribhuvan University |
Keller S.F.,Swiss Federal Research Station for Agroecology and Agriculture |
Gc Y.D.,Swiss Federal Research Station for Agroecology and Agriculture
Journal of Biopesticides | Year: 2014
A laboratory experiment was conducted to evaluate the level of effects by different concentrations of indigenous entomopathogenic fungus, Metarhizium anisopliae (Metsch.) Sorokin spores by dipping the non-target organisms, the silkworm, Bombyx mori L. in the fungus suspension at laboratory condition in Rampur, Chiwan, Nepal. The selected most virulent fungus isolate, among 26 was tested at different concentrations of 107, 106, 105, 104, 103 and 102 number of spores per ml including a control each replicated thrice to each of 30 fourth instar silkworm larvae. The mortality of silkworm larvae due to fungus started only after five days of the treatment and finally caused 70, 44.44, 28.88, 26.66, 23.33 and 3.33 percent death of silkworm larvae with 107, 106, 105, 104, 103 and 102 spores per ml of fungal conidial concentrations respectively. The larval body weight was significantly lower even one day after treatment in the lots treated with 107 spores as compared to other concentrations. On the third and fourth day of treatment, there was no significant difference in the body weight of silkworm larvae in all the treatments. There was significantly lower weight in the lots treated with 107 spores after fifth, sixth and seven days of treatment but after eighth days, there was no significant difference in the body weight with the treatments. The laboratory result indicated that even a small number of conidia of M. anisopliae (Metsch.) Sorokin caused mortality and was found hazardous to silkworms. © 2014, JBiopest. All rights reserved.
Kumar V.,University of Sheffield |
Holzkaemper A.,Swiss Federal Research Station for Agroecology and Agriculture |
Lerner D.,University of Sheffield
Modelling for Environment's Sake: Proceedings of the 5th Biennial Conference of the International Environmental Modelling and Software Society, iEMSs 2010 | Year: 2010
Developing supporting models for multidisciplinary, uncertain and complex Integrated Catchment Management (ICM) is a highly challenging task. Knowledge from multiple disciplines must be integrated, and the process is compounded by significant uncertainty. The key gap that provides the research context is the need for a holistic modelling framework to support ICM, able to capture system complexities and interrelationships, and identify long-term solutions to catchment management problems. In this paper, we present the feasibility study of a new framework for developing an integrated meta-model for decision-support in ICM. The study undertaken by the Catchment Science Centre at the University of Sheffield in a project called the Macro-Ecological Model (MEM) in collaboration with the Environment Agency of UK. The MEM is developed as a consistent framework for the integration of knowledge and information about environmental, social and economic processes and process-interactions that are affected by management actions and have impacts on multiple management objectives. The MEM combines the advantages of "soft" techniques of stakeholder participation for problem structuring, interdisciplinary communication and negotiation with the "hard" predictive capabilities for analysing the likely outcomes of different management scenarios. The metamodel could serve as a learning and decision-support tool to be applied within a group of decision-makers and stakeholders.