Wageningen University and Research Centre

About: Wageningen University and Research Centre is a education organization based out in Wageningen, Netherlands. It is known for research contribution in the topics: Population & Sustainability. The organization has 23474 authors who have published 54833 publications receiving 2608897 citations.

Diversity of flower-visiting bees in cereal fields: effects of farming system, landscape composition and regional context

Abstract: 1. Agri-environment schemes promote organic farming in an attempt to reduce the negative effects of agricultural intensification on farmland biodiversity and ecosystem services such as pollination. Farming system, landscape context and regional differences may all influence biodiversity, but their relative impact and possible interactions have been little explored. 2. The study was performed in three regions (150 km apart, 400-500 km(2) per region) differing in land use intensity. Within each region, seven pairs of conventionally and organically cultivated wheat fields (mean size 4 ha, 42 study fields) were selected to encompass a gradient from heterogeneous to homogeneous landscapes within a 1-km radius around each field. 3. Farming system had the greatest influence on biodiversity. Higher bee diversity, flower cover and diversity of flowering plants were recorded in organic compared with conventional fields. Bee diversity was related both to flower cover and diversity of flowering plants, suggesting plant-mediated effects of the farming system. 4. Differences in bee diversity between organic and conventional fields increased with the proportion of arable crops in the surrounding landscape, indicating that processes at the landscape level modified the effectiveness of organic farming in promoting biodiversity. Similar patterns for flower cover and diversity of flowering plants suggested that landscape effects on bee diversity were mainly resource-mediated. After statistically removing the variance explained by flower parameters, residual bee diversity increased with increasing landscape heterogeneity. 5. Bee diversity differed between the three regions, but the effects of farming systems and landscape context were independent of regional differences. 6. Synthesis and applications. Bee diversity in wheat fields was mainly influenced by farming system, but an understanding of local bee diversity needs to incorporate both landscape and regional perspectives. The consistency of the results in three regions provides a reliable basis for management decisions. Agri-environment schemes that promote organic farming in homogeneous landscapes where there are few remaining flower-rich habitats could have the highest relative impact. However, while organic farming could help to sustain pollination services by generalist bees in agricultural landscapes, other measures are required to conserve more specialized bee species in semi-natural habitats.

Salivary secretions by aphids interacting with proteins of phloem wound responses

Abstract: Successful phloem feeding requires overcoming a number of phloem-related plant properties and reactions. The most important hurdle is formed by the phloem wound responses, such as coagulating proteins in the phloem sieve elements of the plant and in the capillary food canal in the insect's mouth parts, i.e. the stylets. It seems that in order to prevent protein clogging inside a sieve element, ejection of watery saliva plays an important role. This ejection is detected in the electrical penetration graph (EPG) as E1 salivation and always precedes phloem sap ingestion. During this feeding from sieve elements, another regular and concurrent salivation also occurs, the watery E2 salivation. This E2 saliva is added to the ingested sap and, it probably prevents phloem proteins from clogging inside the capillary food canal. Whatever the biochemical mode of action of the inhibition of protein coagulation might be, in some plants aphids do not seem to be able to prevent clogging, which may explain the resistance to aphids in these plants. The relevance of this hypothesis is demonstrated by new experimental results and is related to new EPG results from plants with phloem-located resistance.

Twenty-three unsolved problems in hydrology (UPH)–a community perspective

Abstract: This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.