Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

    We have a manual that explains all the features 

Current refinement(s):

Records 1 - 20 / 951

  • help
  • print

    Print search results

  • export
    A maximum of 250 titles can be exported. Please, refine your queryYou can also select and export up to 30 titles via your marked list.
  • alert
    We will mail you new results for this query: keywords==trees
Check title to add to marked list
Ecosysteemdiensten van bomen en groen in de stad
Hiemstra, J.A. - \ 2017
Wageningen : Groen Kennisnet
bomen - planten - biodiversiteit - ecosystemen - klimaat - luchtkwaliteit - regenwateropvang - stedelijke gebieden - trees - plants - biodiversity - ecosystems - climate - air quality - water harvesting - urban areas
Groen kost geld en de baten zijn slecht tastbaar. Het project 'Ecosysteemdiensten van boomkwekerijproducten' ontwikkelt instrumenten om de voordelen van groen beter te laten meewegen bij het nemen van beslissingen. Voordelen: verkoeling, luchtzuivering, waterberging en beleefbare biodiversiteit. In eerste instantie voor de productgroep bomen, later ook voor andere productgroepen.
Greenery: more than beauty and health : A summary of the benefits of greenery on health, productivity, performance and well-being
Hiemstra, J.A. ; Vries, S. de; Spijker, J.H. - \ 2017
Wageningen : Wageningen University & Research - 6 p.
health - well-being - plants - trees - reconditioning - air quality - biodiversity - air conditioning - learning - labour - green roofs - green walls - gezondheid - welzijn - planten - bomen - herstellen - luchtkwaliteit - biodiversiteit - klimaatregeling - leren - arbeid (werk) - groene daken - groene gevels
Greenery in our living environment is beneficial for more than just our health and well-being. It facilitates water management and stimulates biodiversity in built-up areas, and it can also reduce the effects of noise pollution. Greenery also has a positive impact on the property value of homes and offices. This document provides general information on the benefits of greenery, supplementary to the detailed fact sheets on how greenery can improve health and well-being in Residential, Professional, Educational and Healthcare contexts.
Forest-grassland transitions : How livestock and fire shape grassy biomes
Bernardi, Rafael E. - \ 2017
University. Promotor(en): Marten Scheffer, co-promotor(en): Milena Holmgren Urba; Matías Arim. - Wageningen : Wageningen University - ISBN 9789463436212 - 129
forests - grasslands - fire - cattle - livestock - subtropics - south america - trees - bossen - graslanden - brand - rundvee - vee - subtropen - zuid-amerika - bomen

Plant associations are determined by complex interactions with their environment depending on resource availability, landscape features, and periodic disturbances that shape the structure and functions of these communities. Forests, savannas and grasslands extend across the global land surface, contribute to planetary processes and provide ecosystems services sustaining local production. However, the factors that explain the distribution of trees and determine these biomes are still not well understood. In this thesis, long-standing questions about the origins and distribution of these ecosystems are discussed in light of new evidence suggesting that a feedback of fire and grasses may maintain forests, savannas and grasslands as alternative tree cover states. I also address how anthropogenic land use, including the introduction of livestock, may be affecting these dynamics, particularly in the neotropics, with consequences in terms of potential transitions in tree cover regimes.

I analyze the distribution of trees in the grasslands of subtropical South America, looking at what may determine current tree cover and change dynamics (Chapters 2 & 3). The results suggest that, in non-cultivated areas, the expansion of trees into grasslands is likely limited by fire, livestock and precipitation, and that livestock likely reduces fire frequency (Chapter 2). The analyses also suggest that in the Uruguayan Campos of southeastern South America, where fire frequency is low and livestock densities are high, a release in livestock density may cause a moderate expansion of forests into grasslands (Chapter 3). To understand the consequences of a potential transition to higher tree cover by increasing precipitation, I looked at the effects of tree cover in subtropical rangelands (Chapter 5). The results indicated that isolated trees can improve the forage quality and abundance of these rangelands, with potential benefits in terms of biodiversity and ecosystem services. Lastly, I analyzed correlational patterns relating livestock density to vegetation structure across the global tropics and subtropics (Chapter 4), in an attempt to generalize the findings of Chapter 2. The results indicate that extensive livestock systems reduce fire frequency and impact vegetation structure, maintaining savannas and grasslands with low tree cover, low fire frequency and a higher presence of shrubs and dwarf trees.

Bomen aan der einder : Onze bomen en bossen door de eeuwen heen (herziene versie)
Pistorius, R. ; Vries, S.M.G. de - \ 2017
Wageningen : Wageningen UR
bomen - soortendiversiteit - historische ecologie - genetische bronnen van plantensoorten - trees - species diversity - historical ecology - plant genetic resources
Pas in de laatste decennia hebben bossen hun voornaamste functie, houtproductie, verloren. Ons huidige, relatief weinig diverse, bosbestand getuigt nog van die verloren functie. Reden te meer het behoud van de biodiversiteit van onze bossen aandacht te geven. Deze brochure belicht ons nationaal bosbeheer door de eeuwen heen en staat stil bij de huidige bewaring van genetisch materiaal van autochtone bomen.
Veenvrij substraat : Verkenning van de mogelijkheden van veenvrij substraat in de teelt van laanbomen (opzetters)
Sluis, B.J. van der; Reuler, H. van - \ 2016
Randwijk : Wageningen Plant Research, Bloembollen, Boomkwekerij & Fruit (Rapport 2016-09) - 21 p.
substraten - kweekmedia - bomen - turf - potcultuur - cultuurmethoden - containerplanten - substrates - culture media - trees - peat - pot culture - cultural methods - container grown plants
Verkenning sensing laanboomkwekerij : toepassing van de bodemscan in de laanboomkwekerij
Baltissen, A.H.M.C. ; Sluis, B.J. van der - \ 2016
Randwijk : Praktijkonderzoek Plant & Omgeving BBF - 17 p.
aftasten - remote sensing - sensors - bos- en haagplantsoen - bomen - sensing - woody nursery stock - trees
De doelstelling van dit project is het verkennen van de mogelijkheden van nieuwe sensing technieken in de laanboomkwekerij. Gekozen is voor het uitvoeren van een sensing van de bodem. De bodem is de basis van de teelt. Het verkrijgen van inzicht in de variatie van de bodem kan helpen om teeltmaatregelen af te stemmen op die variatie. Dit rapport beschrijft een eerste verkenning naar de mogelijkheden van Proximal Soil Sensing en heeft als doel het vaststellen van de variatie van de bodem met een specifieke bodemsensor (EM38-mk2) en onderzoeken wat deze variatie betekent voor de laanboomteelt.
Examining growth, yield and bean quality of Ethiopian coffee trees : towards optimizing resources and tree management
Bote, Adugna - \ 2016
University. Promotor(en): Niels Anten, co-promotor(en): Jan Vos; F.L. Ocho. - Wageningen : Wageningen University - ISBN 9789462578319 - 138
coffea - coffea arabica - trees - growth - yields - quality - radiation - nitrogen - agroecosystems - bomen - groei - opbrengsten - kwaliteit - straling - stikstof - agro-ecosystemen

Coffee (Coffeaarabica L.)bean production and quality are determined by a diversity of interacting factors (e.g. shade, nitrogen, crop traits). Bean yield increases with increase in radiation, but adequate fertilizer suppliesare needed to sustain the productivity. This thesis analysed coffee tree growth, bean production and bean quality in relation to different degrees of exposure to radiation and nitrogen supply. Growth of leaves and branches and properties of leaves such as specific leaf area, nitrogen content per unit leaf area and light-saturated rate of photosynthesis were determined. Radiation interception and nitrogen uptake were also determined as were radiation use efficiency and apparent nitrogen recovery. Tree biomass and coffee bean yield responded positively to both radiation and nitrogen supply. Abundant bean yield to the detriment of vegetative growth, however, resultedin biennial bearing in coffee trees. Effects of fruit load on coffee treegrowth and productivity were studied for two consecutive years and the resultshowed that competition between fruit growth and vegetative growth predisposed the trees for biennial bearing. Reduced vegetative growth when fruit load is high reduces the number of flower bearing nodes and hence yields in the next season. Coffee quality is a sum of favourable characteristics that satisfies requirements of different actors in the coffee chain and is the factor determining the price on the coffee market. This study has also examined coffee quality attributes in relation to radiation and nitrogen, fruit load manipulation, and genotype by environment (different altitudes) interactions. The result indicated that factors and conditions that support non-limiting supply of resources for bean to grow and a sufficient long period of maturation promote coffee bean quality. Overall, the study gained further understanding of coffee tree growth, yield and bean quality responses to aforementioned factors and explored traits that underlie the patterns. Further works are required to use the traits and describe the behaviour of coffee trees in different agro-ecosystems.

Invloed van beekbegeleidende bomen op de ecologische kwaliteit van Noord-Brabantse beken
Verdonschot, R.C.M. ; Brugmans, Bart ; Scheepens, Mark ; Coenen, Daniël ; Verdonschot, P.F.M. - \ 2016
H2O online (2016)28 juli.
aquatische ecologie - waterlopen - bomen - noord-brabant - monitoring - beschaduwen - gegevensanalyse - waterschappen - vegetatie - waterplanten - waterkwaliteit - aquatic ecology - streams - trees - shading - data analysis - polder boards - vegetation - aquatic plants - water quality
Monitoringsdata van Brabantse beken laat zien dat bomen belangrijk zijn voor het halen van ecologische doelen. Echter, voor maximale effectiviteit met betrekking tot vegetatieontwikkeling en koeling van het beekwater voldoet alleen de zwaarste beschaduwingsklasse (>70%) en moet gestreefd worden naar lange beschaduwde trajecten. Macrofauna profiteert vooral via de door bomen gegenereerde substraatdifferentiatie. Het toepassen van beschaduwing brengt voor de waterschappen wel grote uitdagingen met zich mee. Verder blijkt uit de data-analyse dat jaarrond voldoende stroming een vereiste is voor de ecologische doelrealisatie in de trajecten.
The facilitative role of trees in tree-grass interactions in savannas
Priyadarshini, K.V.R. - \ 2016
University. Promotor(en): Herbert Prins; Steven Bie, co-promotor(en): Ignas Heitkonig. - Wageningen : Wageningen University - ISBN 9789462577008 - 134 p.
plant interaction - trees - grasses - savannas - ecosystems - ecology - planteninteractie - bomen - grassen - savannen - ecosystemen - ecologie

Terrestrial ecosystems support a high plant diversity where different plant types coexist. However, the mechanisms that support plant coexistence are not entirely clear. Savanna ecosystems that are nutrient and water limited are characterized by a unique ecological feature: the coexistence of trees and grasses. Tree-grass interactions in savannas are typically viewed as being competitive and are based on the Gaussian principle of niche or habitat differentiation. Trees and grasses are reported to suppress the growth of each other and the interactions are viewed as competition. However, tree-grass mixtures persist in a range of rainfall conditions in savannas. This study examined tree-grass interactions to understand the ecological processes that may sustain tree-grass coexistence in dry savannas (< 800 mm of rainfall) of southern Africa. Water and nitrogen resource-use patterns of trees and grasses were investigated and the effects of competition between trees and grasses on resource storage in perennial grasses were examined. An ecological perspective of the role of trees in two human land-use types in African drylands is provided and the functionality of trees in these land-use types was reviewed.

Seasonality of plant available water imposes intense water limitation to plants in savannas. Yet, trees and grasses coexist. The water relations between trees and grasses are poorly understood. In Chapter 2, the principal water-sources for trees and grasses in different seasons were identified using the natural variation in H and O stable isotope composition of source waters. Seasonal differences in the stable isotope composition of water in trees and grasses indicated that there was water-source use partitioning as well as overlap. Trees and grasses used water from the topsoil after rainfall indicating overlap of water-sources. Trees shifted to groundwater or subsoil water when there was no water in the topsoil, indicating partitioning of water-use. Grasses always used water from the topsoil. By labelling deep-soil (2.5 m depth) with a deuterium tracer, hydraulic-redistribution in all the studied tree species and water transfer to grasses via the topsoil was confirmed. However, this occurred only in the dry-season. Results indicated possible shifts in tree-grass interactions during different periods of the year. Furthermore, dry-season hydraulic-redistribution indicated potential facilitation affects by trees to their understory grasses.

A key question in savanna ecology is how trees and grasses coexist under nitrogen limitation. In Chapter 3, the sources of nitrogen for trees and grasses in a semi-arid savanna were investigated using natural abundance of foliar δ15N and nitrogen content. 15N tracer additions were used additionally to investigate the redistribution of subsoil nitrogen by trees to grasses. Foliar δ15N values were consistent with trees and grasses using mycorrhiza-supplied nitrogen in all seasons and a switch to microbially-fixed nitrogen during the wet season. Based on seasonal variation in mineralization rates in the Kruger Park region, the use of mineralized soil nitrogen by trees and grasses seemed highly unlikely. The foliar δ15N values were similar for all the studied tree species differing in the potential for nitrogen-fixation consistent with the absence of nodules indicating the lack of rhizobially fixed nitrogen. The tracer experiment showed that nitrogen was redistributed by trees to understory grasses in all seasons. Redistribution of nitrogen by trees and subsequent uptake of this tree redistributed nitrogen by grasses from the topsoil was independent of water redistribution. Although there was overlap of nitrogen sources between trees and grasses, dependence on biological sources of nitrogen coupled with redistribution of sub-soil nitrogen by trees could be contributing to the co-existence of trees and grasses in semi-arid savannas.

An important plant response to competition and resource limitation is an increase in root reserves. In Chapter 4, the root characteristics of perennial grasses in the presence and absence of trees as a proxy of competition in South African savannas in three sites that differed in rainfall were investigated. The hypothesis on which this investigation was based was that competition from trees and water limitation will result in increased storage in roots of grasses under trees. However, no significant effect of variation in rainfall of the different study locations on root characteristics of grasses were found. Furthermore, most root characteristics were not significantly influenced by tree presence with the exception of nitrogen-content. The root nitrogen content showed an increase with rainfall and tree presence through potentially higher mineralization rates and nitrogen availability in the under-tree canopy environment. The study sites occurred in the drier rainfall range in South Africa. Therefore, it is likely that trees and grasses in these dry savannas might have a positive relationship conforming to the stress-gradient hypothesis. Alternatively, grasses and trees might be using complementary water and nutritional resources.

The mix of trees and grasses is critical for the functioning of the savanna biome, which supports a large fraction of the human population and sustains the highest densities and diversities of herbivores in the world. Both, increases and decreases in tree densities have been reported from savannas globally, which are attributed to human activities and climate change. Changes in tree densities could drastically impact ecosystem functioning and lead to land degradation and large economic losses. Consequently, the sustainable and heterogeneous nature of various savanna land-use types is compromised. In Chapter 5, the significant role of trees in dry savannas (< 800mm rainfall) based on nutrient and water-redistribution capabilities of savanna trees is illustrated. An ecological perspective of the role of trees in two human land-use types in African drylands: agroforests and rangelands which include silvo-pastoral systems and mixed-game-livestock farming systems, is provided. The causes for the loss of trees in these land-use types is evaluated and the role of trees for better land and sustainable natural resource management is highlighted.

Chapter 6 synthesises the conclusions of all the preceding chapters highlighting the importance of facilitative interactions in tree-grass coexistence in savannas that are mostly overlooked. A simple Gaussian model of niche or habitat differentiation may not be a holistic and functional explanation of plant coexistence but rather the role of biotic interactions that include symbionts, parasites, or predators that will influence not only the competitive ability of plants but also facilitation, may be more pragmatic. Plant-plant interactions are complex and a multitrophic approach may be necessary to understand the functioning of these interactions and their roles in ecosystems.

The effect of urban green infrastructure on local microclimate and human thermal comfort
Wang, Y. - \ 2016
University. Promotor(en): Rik Leemans, co-promotor(en): Dolf de Groot; H.J. Wörtche. - Wageningen : Wageningen University - ISBN 9789462576414 - 220 p.
urban environment - green infrastructure - urban areas - towns - management of urban green areas - microclimate - temperature - trees - ecosystem services - stadsomgeving - groene infrastructuur - stedelijke gebieden - steden - groenbeheer - microklimaat - temperatuur - bomen - ecosysteemdiensten
Pan-European strategy for genetic conservation of forest trees and establishment of a core network of dynamic conservation units
Vries, S.M.G. de; Alan, Murat ; Bozzano, Michele ; Burianek, Vaclav - \ 2015
Rome : EUFORGEN - ISBN 9789292550295 - 40 p.
forest administration - forests - forest trees - genetic diversity - trees - nature conservation - bosbeheer - bossen - bosbomen - genetische diversiteit - bomen - natuurbescherming
The diversity of forests, at the level of species and at the level of genetic diversity within species, is an important resource for Europe. Over the past several decades European countries have made considerable efforts to conserve the genetic diversity of tree species. According to the EUFGIS portal, there are more than 3200 genetic conservation units which harbour more than 4000 populations of about 100 tree species. An earlier analysis of the EUFGIS information revealed significant gaps in the conservation efforts in terms of the species covered and the geographical distribution of the units within the species’ ranges. Subsequently, the EUFORGEN Steering Committee established a working group to develop the pan-European genetic conservation strategy for forest trees. The process followed by the working group and its results are presented in this report
Op het spoor van de boktor
Kleis, R. ; Copini, P. - \ 2015
Resource: weekblad voor Wageningen UR 20 (2015)6. - ISSN 1874-3625 - p. 18 - 19.
cerambycidae - plantgezondheid - plantenplagen - bossen - bomen - acer palmatum - jaarringen - dissertaties - plant health - plant pests - forests - trees - growth rings - theses
Boktorren die uitvliegen laten sporen na in hun kraamkamer. Promovendus Paul Copini leest die sporen in jaarringen van bomen en kan zeggen wanneer de boktor is geboren. Een oordeel met gewicht.
Boomkronen afleiden uit het Actueel Hoogtebestand Nederland : kwaliteitsaspecten rondom het geautomatiseerd in kaart brengen van bomen op basis van het AHN2-bestand
Meijer, M. ; Rip, Frans ; Benthem, R. van; Clement, J. ; Sande, C. van der - \ 2015
Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2671) - 85
bomen - kroondak - kroon - gegevensanalyse - gegevens verzamelen - methodologie - remote sensing - hoogteligging - cartografie - nederland - trees - canopy - crown - data analysis - data collection - methodology - altitude - mapping - netherlands
Alom wordt erkend dat bomen belangrijk zijn. Zowel voor de mens, de natuur als het klimaat. Recentelijk is een procedure ontwikkeld om op basis van het nationale Nederlandse hoogtebestand AHN2 een bestand te genereren met alle boomkronen in Nederland, genaamd ‘CP’. Een dergelijk bestand kan onder andere het groenbeheer van de gemeenten in Nederland vereenvoudigen en helpen bij het inventariseren van landschapselementen. De vraag is echter: hoe goed is dit bestand? In dit rapport wordt voor een drietal verschillende gebieden onderzocht wat de kwaliteit is van CP. Verder wordt mede op basis van de ervaringen die tijdens het kwaliteitsonderzoek zijn gedaan een standaard kwaliteitsraamwerk opgezet voor het controleren van nieuwe versies van het boomkronenbestand. Daarnaast is dit document er ook op gericht om de potentiële gebruiker een beter beeld van de kwaliteit te geven.
Markers inside wood : tree rings as archives of insect outbreaks, drift-sand dynamics, and spring flooding
Copini, P. - \ 2015
University. Promotor(en): Frits Mohren, co-promotor(en): Ute Sass-Klaassen; Jan den Ouden. - Wageningen : Wageningen University - ISBN 9789462574861 - 192
acer palmatum - quercus robur - hout - insectenplagen - jaarringen - uitbraken (ziekten) - inundatie - houtanatomie - bomen - wood - insect pests - growth rings - outbreaks - flooding - wood anatomy - trees

MARKERS INSIDE WOOD – TREE RINGS AS ARCHIVES OF INSECT OUTBREAKS, DRIFT-SAND DYNAMICS AND SPRING FLOODING

Trees are long-living organisms that record ecologically relevant information in their xylem that can be accessed by dendrochronology, the study of tree rings. Specific environmental events like frost, fire, floods, burial or wounding may drastically alter the anatomy of tree rings and consequently may leave markers inside trees. These wood-anatomical markers have shown a high potential for studying past environmental events with an annual or even intra-annual temporal resolution. In this thesis, the temporal resolution of wood-anatomical markers was studied to date wounds made by invasive Anoplophora beetles. In addition, the accuracy of dating drift-sand dynamics and spring flooding events was studied using wood-anatomical changes, which were expected to occur after drastic changes in the stem and root environment. It was hypothesised that all these wood-anatomical markers can be used with an intra-annual resolution. Field studies in combination with experiments were used to study tree growth and the formation of wood-anatomical markers in Japanese maple (Acer palmatum Thunb.) and pedunculate oak (Quercus robur L.).

It was shown that wounds in Japanese maple can be assigned to three different phases related to tree-ring development: (1) wounds that originated during dormancy are located at the tree-ring boundary; (2) wounds that originated during the growing season are located within the tree ring. If wound-xylem formation was observed locally around the wound (3), it could either imply that the wound originated at the very end of the growing season or just before the onset of radial growth or during dormancy when temperature was high. Dating wounds caused by the formation of exit holes has proved to be very significant in fighting invasive insect outbreaks. By pinpointing the exact year and season when Anoplophora beetles emerged, it can be substantiated whether exit holes in imported trees were formed at the location of import. This knowledge can subsequently be used to draw up customised eradication measures and allocate proper surveillance plans and population dynamics can be reconstructed.

Living trees in drift-sand areas may contain burial or exposure signals even if the sand under which they were buried has long since disappeared. Anatomical changes in pedunculate oak trees due to burial are not a result of physical changes in the stem environment that directly affect the cambium. Instead they are most likely the result of adventitious root formation that transforms lower parts of the stem into root, and concomitantly induces a change from stem to root anatomy. As the formation of a wood-anatomical marker caused by burial can be delayed by many years or might be entirely absent, depending on the formation of adventitious root formation, its presence only allows for an estimate on minimum burial age.

Flood rings containing anomalously small earlywood vessels in pedunculate oak are formed in response to spring flooding within a narrow time window related to cambial phenology. They can be induced if a flooding event has occurred for at least two weeks during spring. The extreme reduction in vessel size is a consequence of a delay in vessel formation due to anoxic conditions related to flooding. Flood rings however, provide only limited information on the duration of flooding, as the flooding may have lasted for months (during winter) before it is recorded.

It is concluded that the origin of wood-anatomical markers largely determines the temporal resolution. Markers induced by wounding or flooding show a high intra-annual temporal resolution and immediate effect on tree functioning, whereas burial might not be recorded three years after the triggering events. The different wood-anatomical markers addressed in this thesis illustrate the relevance of studying the mechanism behind the formation of markers for correct interpretation of the specific triggering factor as well as their temporal resolution. Only with this knowledge it becomes possible to reliably use wood-anatomical markers as archives to understand and reconstruct dynamics in geomorphic, entomologic, pathogenic or climatic factors.

Teelt van laanbomen op eigen wortel
Sluis, Bart van der - \ 2015
trees - street trees - cultivation - plant health - vegetative propagation - propagation materials - cost analysis - cropping systems - cuttings - rhizoplane
Street greenery and its physical and psychological impact on outdoor thermal comfort
Klemm, W. ; Heusinkveld, B.G. ; Lenzholzer, S. ; Hove, B. van - \ 2015
Landscape and Urban Planning 138 (2015). - ISSN 0169-2046 - p. 87 - 98.
urban-environment - climate-change - human health - vegetation - spaces - infrastructure - design - model - landscapes - trees
This study focuses on the benefits of street greenery for creating thermally comfortable streetscapes in moderate climates. It reports on investigations on the impact of street greenery on outdoor thermal comfort from a physical and psychological perspective. For this purpose, we examined nine streets with comparable geometric configurations, but varying amount of street greenery (street trees, front gardens) in the city of Utrecht, the Netherlands. Mobile micrometeorological measurements including air temperature (Ta), solar and thermal radiation were performed, enabling the calculation of mean radiant temperature (Tmrt). Additionally, semi-structured interviews with pedestrians about their momentary and long-term perceived thermal comfort and their esthetical appreciation of the green street design were conducted. Measurements showed a clear impact (p = 0.0001) of street greenery on thermal comfort through tree shading: 10% tree crown cover within a street canyon lowered street averaged Tmrt about 1 K. In contrast, our results did not show an influence of street greenery on street averaged Ta. Interview results indicated that momentary perceived thermal comfort tended to be related to the amount of street greenery. However, the results were not statistically significant. Related to long-term perceived thermal comfort respondents were hardly consciously aware of influences by street greenery. Yet, people significantly (p <0.001) valued the presence of street greenery in esthetic terms. In conclusion, street greenery forms a convenient adaptive strategy to create thermally comfortable and attractive living environments. Our results clearly indicate that both physical and psychological aspects of thermal comfort have to be considered in urban design processes.
Mapping Soil Properties of Africa at 250 m resolution: random forest significantly improve current predictions
Hengl, T. ; Heuvelink, G.B.M. ; Kempen, B. ; Leenaars, J.G.B. ; Walsh, M.G. ; Shepherd, K.D. ; Sila, A. ; Macmillan, R.A. ; Mendes de Jesus, J.S. ; Tamene, L. ; Tondoh, J.E. - \ 2015
PLoS One 10 (2015)6. - ISSN 1932-6203
continental-scale - maps - classification - surveillance - management - models - carbon - trees
80% of arable land in Africa has low soil fertility and suffers from physical soil problems. Additionally, significant amounts of nutrients are lost every year due to unsustainable soil management practices. This is partially the result of insufficient use of soil management knowledge. To help bridge the soil information gap in Africa, the Africa Soil Information Service (AfSIS) project was established in 2008. Over the period 2008–2014, the AfSIS project compiled two point data sets: the Africa Soil Profiles (legacy) database and the AfSIS Sentinel Site database. These data sets contain over 28 thousand sampling locations and represent the most comprehensive soil sample data sets of the African continent to date. Utilizing these point data sets in combination with a large number of covariates, we have generated a series of spatial predictions of soil properties relevant to the agricultural management—organic carbon, pH, sand, silt and clay fractions, bulk density, cation-exchange capacity, total nitrogen, exchangeable acidity, Al content and exchangeable bases (Ca, K, Mg, Na). We specifically investigate differences between two predictive approaches: random forests and linear regression. Results of 5-fold cross-validation demonstrate that the random forests algorithm consistently outperforms the linear regression algorithm, with average decreases of 15–75% in Root Mean Squared Error (RMSE) across soil properties and depths. Fitting and running random forests models takes an order of magnitude more time and the modelling success is sensitive to artifacts in the input data, but as long as quality-controlled point data are provided, an increase in soil mapping accuracy can be expected. Results also indicate that globally predicted soil classes (USDA Soil Taxonomy, especially Alfisols and Mollisols) help improve continental scale soil property mapping, and are among the most important predictors. This indicates a promising potential for transferring pedological knowledge from data rich countries to countries with limited soil data.
Phylogenetics of African Rinorea (Violaceae): Elucidating Infrageneric Relationships using Plastid and Nuclear DNA Sequences
Velzen, R. van; Wahlert, G.A. ; Sosef, M.S.M. ; Onstein, R.E. ; Bakker, F.T. - \ 2015
Systematic Botany 40 (2015)1. - ISSN 0363-6445 - p. 174 - 184.
rain-forest - tropical forest - lepidoptera nymphalidae - diversity - cameroon - trees - gabon
Rinorea is a pantropical genus of shrubs and small trees within the family Violaceae. The genus is particularly diverse in Africa where species are ecologically important as they are often abundant or even dominant in particular forest types and act as larval host plants for highly specialized Cymothoe butterflies. Despite their importance, species identification of African Rinorea is difficult and a taxonomic revision is needed. Previous phylogenetic studies have suggested that neotropical taxa are sister to a palaeotropical clade, with multiple independent dispersals to Madagascar, but these were based on plastid data only. We therefore present an updated phylogeny of Rinorea with increased sampling of African taxa, using plastid as well as nuclear DNA sequences. Phylogenetic relationships inferred from nuclear DNA data were generally congruent with those based on evidence from plastid haplotypes from earlier studies. Our increased taxonomic sampling also revealed previously undiscovered African Rinorea clades, some of which warrant further taxonomic study. Ancestral state reconstructions refute previous hypotheses about the evolution of morphological characters traditionally used for Rinorea infrageneric classification. In addition, some widespread species may comprise species complexes. It is clear that African Rinorea require comprehensive taxonomic revision; our contribution to understanding Rinorea infrageneric relationships will facilitate this task.
Hyperdominance in Amazonian forest carbon cycling
Fauset, S. ; Arets, E.J.M.M. ; Steege, H. ter; Pena Claros, M. ; Poorter, L. ; Levis, C. ; Toledo, M. - \ 2015
Nature Communications 6 (2015). - ISSN 2041-1723
tropical forests - rain-forest - experimental drought - species composition - economics spectrum - biomass - trees - allometry - productivity - mortality
While Amazonian forests are extraordinarily diverse, the abundance of trees is skewed strongly towards relatively few ‘hyperdominant’ species. In addition to their diversity, Amazonian trees are a key component of the global carbon cycle, assimilating and storing more carbon than any other ecosystem on Earth. Here we ask, using a unique data set of 530 forest plots, if the functions of storing and producing woody carbon are concentrated in a small number of tree species, whether the most abundant species also dominate carbon cycling, and whether dominant species are characterized by specific functional traits. We find that dominance of forest function is even more concentrated in a few species than is dominance of tree abundance, with only ˜1% of Amazon tree species responsible for 50% of carbon storage and productivity. Although those species that contribute most to biomass and productivity are often abundant, species maximum size is also influential, while the identity and ranking of dominant species varies by function and by region.
Een jasje voor het bloeden
Kleis, R. ; Lammeren, A.A.M. van; Korsuize, C.A. - \ 2015
Resource: nieuwssite voor studenten en medewerkers van Wageningen UR 9 (2015)17. - ISSN 1389-7756 - p. 18 - 19.
aesculus - bomen - plantenziekteverwekkende bacteriën - pseudomonas syringae pv. aesculi - ziektebestrijding - methodologie - temperatuur - warmtebehandeling - verwarming - trees - plant pathogenic bacteria - disease control - methodology - temperature - heat treatment - heating
Een groot deel van de kastanjebomen in ons land bloedt. De oorzaak is een lastig te bestrijden bacterie. Wageningse wetenschappers hebben nu een oplossing die even simpel als geniaal is: verwarmen.
Check title to add to marked list
<< previous | next >>

Show 20 50 100 records per page

 
Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.