47 research outputs found
Resilience trinity: Safeguarding ecosystem functioning and services across three different time horizons and decision contexts
Ensuring ecosystem resilience is an intuitive approach to safeguard the functioning of ecosystems and hence the future provisioning of ecosystem services (ES). However, resilience is a multiâfaceted concept that is difficult to operationalize. Focusing on resilience mechanisms, such as diversity, network architectures or adaptive capacity, has recently been suggested as means to operationalize resilience. Still, the focus on mechanisms is not specific enough. We suggest a conceptual framework, resilience trinity, to facilitate management based on resilience mechanisms in three distinctive decision contexts and timeâhorizons: 1) reactive, when there is an imminent threat to ES resilience and a high pressure to act, 2) adjustive, when the threat is known in general but there is still time to adapt management and 3) provident, when time horizons are very long and the nature of the threats is uncertain, leading to a low willingness to act. Resilience has different interpretations and implications at these different time horizons, which also prevail in different disciplines. Social ecology, ecology and engineering are often implicitly focussing on provident, adjustive or reactive resilience, respectively, but these different notions of resilience and their corresponding social, ecological and economic tradeoffs need to be reconciled. Otherwise, we keep risking unintended consequences of reactive actions, or shying away from provident action because of uncertainties that cannot be reduced. The suggested trinity of time horizons and their decision contexts could help ensuring that longerâterm management actions are not missed while urgent threats to ES are given priority
Honey bee colony performance affected by crop diversity and farmland structure: a modeling framework
This is the final version. Available on open access from Wiley via the DOI in this recordForage availability has been suggested as one driver of the observed decline in honey bees. However, little is known about the effects of its spatiotemporal variation on colony success. We present a modeling framework for assessing honey bee colony viability in cropping systems. Based on two real farmland structures, we developed a landscape generator to design cropping systems varying in crop species identity, diversity, and relative abundance. The landscape scenarios generated were evaluated using the existing honey bee colony model BEEHAVE, which links foraging to in-hive dynamics. We thereby explored how different cropping systems determine spatiotemporal forage availability and, in turn, honey bee colony viability (e.g., time to extinction, TTE) and resilience (indicated by, e.g., brood mortality). To assess overall colony viability, we developed metrics, PH and PP, which quantified how much nectar and pollen provided by a cropping system per year was converted into a colony's adult worker population. Both crop species identity and diversity determined the temporal continuity in nectar and pollen supply and thus colony viability. Overall farmland structure and relative crop abundance were less important, but details mattered. For monocultures and for four-crop species systems composed of cereals, oilseed rape, maize, and sunflower, PH and PP were below the viability threshold. Such cropping systems showed frequent, badly timed, and prolonged forage gaps leading to detrimental cascading effects on life stages and in-hive work force, which critically reduced colony resilience. Four-crop systems composed of rye-grassâdandelion pasture, trefoilâgrass pasture, sunflower, and phacelia ensured continuous nectar and pollen supply resulting in TTE > 5Â yr, and PH (269.5Â kg) and PP (108Â kg) being above viability thresholds for 5 yr. Overall, trefoilâgrass pasture, oilseed rape, buckwheat, and phacelia improved the temporal continuity in forage supply and colony's viability. Our results are hypothetical as they are obtained from simplified landscape settings, but they nevertheless match empirical observations, in particular the viability threshold. Our framework can be used to assess the effects of cropping systems on honey bee viability and to develop land-use strategies that help maintain pollination services by avoiding prolonged and badly timed forage gaps.German Academic Exchange ServiceHelmholtz Interdisciplinary GRADuate School for Environmental ResearchBiotechnology and Biological Sciences Research Council (BBSRC
Carbonyl Reductase 3 (CBR3) Mediates 9-cis-Retinoic Acid-Induced Cytostatis and is a Potential Prognostic Marker for Oral Malignancy
The molecular mechanisms of growth suppression by retinoic acid (RA) were examined. Our results suggest that the cytostatic effects of RA could be mediated by the activation of endogenous CBR3 gene in oral squamous cell carcinomas (OSCCs), and the expression is a potential marker for oral malignancy
Cation Exchange during the Synthesis of Colloidal Type-II ZnSe-Dot/CdS-Rod Nanocrystals
Cation exchange is known to occur during the synthesis
of colloidal
semiconductor heteronanoparticles, affecting their band gap and thus
altering their optoelectronic properties. It is often neglected, especially
when anisotropic heterostructures are discussed. We present a study
on the role of cation exchange inevitably occurring during the growth
of anisotropic dot-in-rod structures consisting of a spherical ZnSe
core enclosed by a rod-shaped CdS shell. The material combination
exhibits a type-II band alignment. Two reactions are compared: the
shell-growth reaction of CdS
on ZnSe and an exchange-only reaction of ZnSe cores to CdSe. Transmission
electron microscopy and a comprehensive set of optical spectroscopy
data, including linear and time-resolved absorption and fluorescence
data, prove that cation exchange from ZnSe to CdSe is the dominant
process in the initial stages of the shell-growth reaction. The degree
of cation exchange before significant shell growth starts was determined
to be about 50%, highlighting the importance of cation exchange during
the heteronanostructure growth