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.

An integrated pan‐tropical biomass map using multiple reference datasets

Abstract: We combined two existing datasets of vegetation aboveground biomass (AGB) (Proceedings of the National Academy of Sciences of the United States of America, 108, 2011, 9899; Nature Climate Change, 2, 2012, 182) into a pan-tropical AGB map at 1-km resolution using an independent reference dataset of field observations and locally calibrated high-resolution biomass maps, harmonized and upscaled to 14 477 1-km AGB estimates. Our data fusion approach uses bias removal and weighted linear averaging that incorporates and spatializes the biomass patterns indicated by the reference data. The method was applied independently in areas (strata) with homogeneous error patterns of the input (Saatchi and Baccini) maps, which were estimated from the reference data and additional covariates. Based on the fused map, we estimated AGB stock for the tropics (23.4 N–23.4 S) of 375 Pg dry mass, 9–18% lower than the Saatchi and Baccini estimates. The fused map also showed differing spatial patterns of AGB over large areas, with higher AGB density in the dense forest areas in the Congo basin, Eastern Amazon and South-East Asia, and lower values in Central America and in most dry vegetation areas of Africa than either of the input maps. The validation exercise, based on 2118 estimates from the reference dataset not used in the fusion process, showed that the fused map had a RMSE 15–21% lower than that of the input maps and, most importantly, nearly unbiased estimates (mean bias 5 Mg dry mass ha−1 vs. 21 and 28 Mg ha−1 for the input maps). The fusion method can be applied at any scale including the policy-relevant national level, where it can provide improved biomass estimates by integrating existing regional biomass maps as input maps and additional, country-specific reference datasets.

Social interactions in urban parks: stimulating social cohesion?

Abstract: People from all ethnic backgrounds spend some of their leisure time in green areas. This study found that urban parks are more inclusive green places than non-urban green areas, and that urban parks can promote social cohesion. The objective of the research was to establish the extent to which urban parks facilitate social cohesion and how social interaction and place attachment can contribute to such cohesion. Quantitative research (a survey) and qualitative research (observations and interviews) carried out in five urban parks in the Netherlands revealed that there are many similarities in the ways that ethnic groups use urban parks and in the meanings of such parks to these groups. Urban parks are sites where different ethnic groups mingle and where informal and cursory interactions can stimulate social cohesion. Furthermore, being involved and concerned with parks can facilitate attachment to these places. Urban parks can provide a vital locality where everyday experiences are shared and negotiated with a variety of people. The design of a park, its location and people's image of the park in combination with the cultural characteristics of various ethnic groups inform the opportunities for intercultural interactions.

Enclosed outdoor photobioreactors: Light regime, photosynthetic efficiency, scale‐up, and future prospects

Abstract: Enclosed outdoor photobioreactors need to be developed and designed for large-scale production of phototrophic microorganisms. Both light regime and photosynthetic efficiency were analyzed in characteristic examples of state-of-the-art pilot-scale photobioreactors. In this study it is shown that productivity of photobioreactors is determined by the light regime inside the bioreactors. In addition to light regime, oxygen accumulation and shear stress limit productivity in certain designs. In short light-path systems, high efficiencies, 10% to 20% based on photosynthetic active radiation (PAR 400 to 700 nm), can be reached at high biomass concentrations (>5 kg [dry weight] m(-3)). It is demonstrated, however, that these and other photobioreactor designs are poorly scalable (maximal unit size 0.1 to 10 m(3)), and/or not applicable for cultivation of monocultures. This is why a new photobioreactor design is proposed in which light capture is physically separated from photoautotrophic cultivation. This system can possibly be scaled to larger unit sizes, 10 to >100 m(3), and the reactor liquid as a whole is mixed and aerated. It is deduced that high photosynthetic efficiencies, 15% on a PAR-basis, can be achieved. Future designs from optical engineers should be used to collect, concentrate, and transport sunlight, followed by redistribution in a large-scale photobioreactor.

Heterodimerization and endocytosis of Arabidopsis brassinosteroid receptors BRI1 and AtSERK3 (BAK1).

Abstract: In Arabidopsis thaliana brassinosteroid (BR), perception is mediated by two Leu-rich repeat receptor-like kinases, BRASSINOSTEROID INSENSITIVE1 (BRI1) and BRI1-ASSOCIATED RECEPTOR KINASE1 (BAK1) (Arabidopsis SOMATIC EMBRYOGENESIS RECEPTOR-like KINASE3 [AtSERK3]). Genetic, biochemical, and yeast (Saccharomyces cerevisiae) interaction studies suggested that the BRI1-BAK1 receptor complex initiates BR signaling, but the role of the BAK1 receptor is still not clear. Using transient expression in protoplasts of BRI1 and AtSERK3 fused to cyan and yellow fluorescent green fluorescent protein variants allowed us to localize each receptor independently in vivo. We show that BRI1, but not AtSERK3, homodimerizes in the plasma membrane, whereas BRI1 and AtSERK3 preferentially heterodimerize in the endosomes. Coexpression of BRI1 and AtSERK3 results in a change of the steady state distribution of both receptors because of accelerated endocytosis. Endocytic vesicles contain either BRI1 or AtSERK3 alone or both. We propose that the AtSERK3 protein is involved in changing the equilibrium between plasma membrane–located BRI1 homodimers and endocytosed BRI1-AtSERK3 heterodimers.

Vegetation pattern formation in semi-arid grazing systems

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