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Hans de Kroon

Bio: Hans de Kroon is an academic researcher from Tilburg University. The author has contributed to research in topics: Mental health & Assertive community treatment. The author has an hindex of 61, co-authored 225 publications receiving 13378 citations. Previous affiliations of Hans de Kroon include Smithsonian Tropical Research Institute & Radboud University Nijmegen.


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Journal ArticleDOI
18 Oct 2017-PLOS ONE
TL;DR: This analysis estimates a seasonal decline of 76%, and mid-summer decline of 82% in flying insect biomass over the 27 years of study, and shows that this decline is apparent regardless of habitat type, while changes in weather, land use, and habitat characteristics cannot explain this overall decline.
Abstract: Global declines in insects have sparked wide interest among scientists, politicians, and the general public. Loss of insect diversity and abundance is expected to provoke cascading effects on food webs and to jeopardize ecosystem services. Our understanding of the extent and underlying causes of this decline is based on the abundance of single species or taxonomic groups only, rather than changes in insect biomass which is more relevant for ecological functioning. Here, we used a standardized protocol to measure total insect biomass using Malaise traps, deployed over 27 years in 63 nature protection areas in Germany (96 unique location-year combinations) to infer on the status and trend of local entomofauna. Our analysis estimates a seasonal decline of 76%, and mid-summer decline of 82% in flying insect biomass over the 27 years of study. We show that this decline is apparent regardless of habitat type, while changes in weather, land use, and habitat characteristics cannot explain this overall decline. This yet unrecognized loss of insect biomass must be taken into account in evaluating declines in abundance of species depending on insects as a food source, and ecosystem functioning in the European landscape.

2,065 citations

Journal ArticleDOI
01 Oct 1986-Ecology
TL;DR: The results support the hypothesis that competition for light is "asymmetric" and that the observed increases in plant size variability with increasing density may have been primarily due to competition forLight.
Abstract: over plants grown without competition (P < .05). Plants suffering from both root and shoot competition were not significantly smaller than those suffering from root competition only, but they showed the greatest size variability. In plants competing both above and below ground, root competition accounted for the reduction in mean plant size, but shoot competition accounted for the increase in size inequality. The results support the hypothesis that competition for light is "asymmetric" and that the observed increases in plant size variability with increasing density may have been primarily due to competition for light. There may be situations in which competition for nutrients is also asymmetric, i.e., situations in which nutrients can be preempted by individuals with larger roots. Because a leaf is shaded only by leaves above it, competition for light appears to be inherently asymmetric.

793 citations

Journal ArticleDOI
17 Jul 2014-Nature
TL;DR: The hypothesis that the most widely used neonicotinoid insecticide, imidacloprid, has a negative impact on insectivorous bird populations is investigated and it is shown that, in the Netherlands, local population trends were significantly more negative in areas with higher surface-water concentrations of imidcloprid.
Abstract: Recent studies have shown that neonicotinoid insecticides have adverse effects on non-target invertebrate species. Invertebrates constitute a substantial part of the diet of many bird species during the breeding season and are indispensable for raising offspring. We investigated the hypothesis that the most widely used neonicotinoid insecticide, imidacloprid, has a negative impact on insectivorous bird populations. Here we show that, in the Netherlands, local population trends were significantly more negative in areas with higher surface-water concentrations of imidacloprid. At imidacloprid concentrations of more than 20 nanograms per litre, bird populations tended to decline by 3.5 per cent on average annually. Additional analyses revealed that this spatial pattern of decline appeared only after the introduction of imidacloprid to the Netherlands, in the mid-1990s. We further show that the recent negative relationship remains after correcting for spatial differences in land-use changes that are known to affect bird populations in farmland. Our results suggest that the impact of neonicotinoids on the natural environment is even more substantial than has recently been reported and is reminiscent of the effects of persistent insecticides in the past. Future legislation should take into account the potential cascading effects of neonicotinoids on ecosystems.

766 citations

Journal ArticleDOI
01 Mar 2000-Ecology
TL;DR: In this paper, the authors discuss the applications of elasticity analysis, and its extension, loop analysis, in life history studies and conservation, and highlight the different kinds of results of the two analyses in studies of life histories are emphasized.
Abstract: Elasticity is a perturbation measure in matrix projection models that quantifies the proportional change in population growth rate as a function of a proportional change in a demographic transition (growth, survival, reproduction, etc.). Elasticities thus indicate the relative “importance” of life cycle transitions for population growth and maintenance. In this paper, we discuss the applications of elasticity analysis, and its extension, loop analysis, in life history studies and conservation. Elasticity can be interpreted as the relative contribution of a demographic parameter to population growth rate. Loop analysis reveals the underlying pathway structure of the life cycle graph. The different kinds of results of the two analyses in studies of life histories are emphasized. Because elasticities quantify the relative importance of life cycle transitions to population growth rate, it is generally inferred that management should focus on the transitions with the largest elasticities. Such predictions based on elasticities seem robust, but we do identify three situations where problems may arise. The mathematical properties and biological constraints that underlie these pitfalls are explained. Examples illustrate the additional information that needs to be taken into account for a sensible use of elasticities in population management. We conclude by indicating topics that are in need of research.

561 citations

Journal ArticleDOI
01 Jan 2001-Ecology
TL;DR: In this article, a spatially explicit model con- sisting of partial differential equations using a method for demonstrating pattern formation (Turing analysis) was proposed. And the model revealed that pattern formation can occur in semi-arid areas given only the positive feedback between plant density and local water infiltration coupled with the spatial redistribution of runoff water.
Abstract: Hypotheses about the origin of vegetation pattern formation in semi-arid areas around the world almost all include a common feature of semi-arid areas: the presence of a positive feedback between plant density and water infiltration We investigate whether this positive feedback and the spatial redistribution of runoff water are sufficient to explain vegetation pattern formation For this purpose, we analyze a spatially explicit model con- sisting of partial differential equations using a method for demonstrating pattern formation (Turing analysis) Our analysis reveals that pattern formation can occur in semi-arid areas given only the positive feedback between plant density and local water infiltration coupled with the spatial redistribution of runoff water Thus, slope and underlying heterogeneity are not essential conditions Other factors in the model, such as herbivory, plant dispersal, rainfall, and drought tolerance of plants, appear to determine under what conditions pattern formation is likely but are not the primary factors that generate the patterns The model is in agreement with field observations and indicates the conditions for which vegetation pattern formation can be expected in arid and semi-arid grazing systems

474 citations


Cited by
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Journal ArticleDOI
TL;DR: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols used xiii 1.
Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

14,171 citations

Journal Article

5,680 citations

Journal ArticleDOI
TL;DR: Food in the Anthropocene : the EAT-Lancet Commission on healthy diets from sustainable food systems focuses on meat, fish, vegetables and fruit as sources of protein.

4,710 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a collection of qualified narrative methods for the human sciences that has actually been composed by the authors themselves, which can be used as an excellent source for reading.
Abstract: Whatever our proffesion, narrative methods for the human sciences can be excellent source for reading. Locate the existing files of word, txt, kindle, ppt, zip, pdf, as well as rar in this site. You can definitely check out online or download this publication by right here. Now, never ever miss it. Searching for a lot of offered publication or reading source worldwide? We supply them all in layout kind as word, txt, kindle, pdf, zip, rar and ppt. among them is this qualified narrative methods for the human sciences that has actually been composed by Still confused how you can get it? Well, simply check out online or download by signing up in our website below. Click them. Our goal is always to offer you an assortment of cost-free ebooks too as aid resolve your troubles. We have got a considerable collection of totally free of expense Book for people from every single stroll of life. We have got tried our finest to gather a sizable library of preferred cost-free as well as paid files. GO TO THE TECHNICAL WRITING FOR AN EXPANDED TYPE OF THIS NARRATIVE METHODS FOR THE HUMAN SCIENCES, ALONG WITH A CORRECTLY FORMATTED VERSION OF THE INSTANCE MANUAL PAGE ABOVE.

2,657 citations

Journal ArticleDOI
TL;DR: A single ‘fast–slow’ plant economics spectrum that integrates across leaves, stems and roots is a key feature of the plant universe and helps to explain individual ecological strategies, community assembly processes and the functioning of ecosystems.
Abstract: Summary 1. The leaf economics spectrum (LES) provides a useful framework for examining species strategies as shaped by their evolutionary history. However, that spectrum, as originally described, involved only two key resources (carbon and nutrients) and one of three economically important plant organs. Herein, I evaluate whether the economics spectrum idea can be broadly extended to water – the third key resource –stems, roots and entire plants and to individual, community and ecosystem scales. My overarching hypothesis is that strong selection along trait trade-off axes, in tandem with biophysical constraints, results in convergence for any taxon on a uniformly fast, medium or slow strategy (i.e. rates of resource acquisition and processing) for all organs and all resources. 2. Evidence for economic trait spectra exists for stems and roots as well as leaves, and for traits related to water as well as carbon and nutrients. These apply generally within and across scales (within and across communities, climate zones, biomes and lineages). 3. There are linkages across organs and coupling among resources, resulting in an integrated whole-plant economics spectrum. Species capable of moving water rapidly have low tissue density, short tissue life span and high rates of resource acquisition and flux at organ and individual scales. The reverse is true for species with the slow strategy. Different traits may be important in different conditions, but as being fast in one respect generally requires being fast in others, being fast or slow is a general feature of species. 4. Economic traits influence performance and fitness consistent with trait-based theory about underlying adaptive mechanisms. Traits help explain differences in growth and survival across resource gradients and thus help explain the distribution of species and the assembly of communities across light, water and nutrient gradients. Traits scale up – fast traits are associated with faster rates of ecosystem processes such as decomposition or primary productivity, and slow traits with slow process rates. 5. Synthesis. Traits matter. A single ‘fast–slow’ plant economics spectrum that integrates across leaves, stems and roots is a key feature of the plant universe and helps to explain individual ecological strategies, community assembly processes and the functioning of ecosystems.

2,246 citations