Staff Publications

Staff Publications

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    '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.

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Greenery: more than beauty and health : The positive effects of greenery in urban environments
Hiemstra, J.A. ; Vries, S. de; Spijker, J.H. - \ 2019
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 benefits more than just our health and well-being. It also facilitates water management and promotes biodiversity in built-up areas, and can help reduce the effects of noise pollution. Greenery also helps to raise the property value of homes and offices. This document provides general information on the benefits of greenery, and complements the detailed fact sheets on how greenery can improve health and well-being in Residential, Professional, Educational and Healthcare contexts.
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
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
Wageningen University. Promotor(en): M. Scheffer, co-promotor(en): M. Holmgren; 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
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
aftasten - remote sensing - sensors - bos- en haagplantsoen - bomen - sensing - remote sensing - sensors - 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
Wageningen 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 - coffea - coffea arabica - 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 - noord-brabant - monitoring - 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
Wageningen University. Promotor(en): Herbert Prins; Steven Bie, co-promotor(en): Ignas Heitkonig. - Wageningen : Wageningen University - ISBN 9789462577008 - 134
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
Wageningen University. Promotor(en): Rik Leemans, co-promotor(en): Dolf de Groot; H.J. Wörtche. - Wageningen : Wageningen University - ISBN 9789462576414 - 220
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
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
Wageningen 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 - acer palmatum - quercus robur - wood - insect pests - growth rings - outbreaks - flooding - wood anatomy - trees


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.

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.
Eikensterfte: een serieus en complex probleem
Oosterbaan, A. ; Bobbink, R. ; Decuyper, M. - \ 2015
Vakblad Natuur Bos Landschap (2015)113. - ISSN 1572-7610 - p. 10 - 14.
quercus - bodem-plant relaties - bodemchemie - verzuring - droogte - bomen - groeiplaatsen - soil plant relationships - soil chemistry - acidification - drought - trees - sites
Steeds meer beheerders zien met lede ogen aan hoe de eiken in hun bossen langzaam maar zeker afsterven. Over de precieze oorzaak is nog niet zo heel veel bekend. Wel maakt onderzoek duidelijk dat er meerdere oorzaken zijn die elkaar lijken te versterken. Droogte en aantasting door insecten zijn zeker een deel van het probleem, maar ook de snelle uitspoeling van basische kationen zijn waarschijnlijk een heel belangrijke factor
Essentaksterfte, bosbouwkundig beheersbaar?
Kopinga, J. ; Vries, S.M.G. de - \ 2015
Bosberichten 2015 (2015)1. - ISSN 1574-6046 - p. 1 - 4.
bomen - schimmelziekten - fraxinus excelsior - plantenziekten - rassen (planten) - cultivars - resistentie van variëteiten - trees - fungal diseases - plant diseases - varieties - varietal resistance
Vanaf ca. 2010 slaat de essentaksterfte in Nederland op grote schaal toe. Tot dusver vooral in bossen en wat minder in laanbeplantingen. Hoe het zich verder ontwikkelt, is nog onduidelijk, maar het einde lijkt nog niet in zicht. In sommige regio’s is binnen enkele jaren de conditie van bomen zwaar achteruit gegaan of zijn bomen geheel afgestorven. Voor bosbeheerders en boseigenaren een ware ramp. Gedane investeringen ‘verdampen’. Sommigen vrezen zelfs dat de es geheel uit het Nederlandse bosbeeld zal verdwijnen. Echter, met gerichte bosbouwkundige maatregelen, lijken er mogelijkheden de es te behouden. In deze bijdrage van gastauteurs Jitze Kopinga en Sven de Vries wordt aangegeven welke strategieën daarbij denkbaar zijn en wordt aangegeven welke de meest kansrijke lijken te zijn.
Long-term trends in tropical tree growth: a pantropical study
Groenendijk, P. - \ 2015
Wageningen University. Promotor(en): Pieter Zuidema; Frans Bongers. - Wageningen : Wageningen University - ISBN 9789462572362 - 244
bosbomen - tropische bossen - bomen - groei - jaarringen - bosecologie - bosbedrijfsvoering - centraal-afrika - forest trees - tropical forests - trees - growth - growth rings - forest ecology - forest management - central africa

Tropical forests cover only 7% of the earth’s land surface, but harbour almost half of the world’s biodiversity. These forests also provide many ecosystem services, such as the storage of carbon and the regulation of local and regional climate, and many goods such as timber and fruits. Furthermore, tropical forests contribute disproportionately to the global carbon cycle, storing an estimated 25% of the carbon stocks on land and accounting for a third of the terrestrial net primary productivity. Therefore, changes in forest cover or in the net uptake or loss of carbon by forests directly influences the global carbon cycle. Tropical forests are under increasing anthropogenic pressure and are undergoing rapid changes due to deforestation, conversion to other land uses and logging. Additionally, there is evidence that pristine and intact tropical forests are undergoing changes due to the effects of climate change. Concerted increases in biomass and tree growth have been found in studies monitoring intact tropical forests, suggesting that they acted as considerable carbon sinks over the past decades. On the other hand, decreasing or fluctuating forest growth and biomass have also been noted. These different changes have been attributed to different climatic drivers: growth increases have been suggested to arise from growth stimulation by increasing atmospheric CO2 concentrations, while growth decreases have been interpreted to reflect the limiting effects of increased temperature on growth. As monitoring plots usually cover only a few decades, it is still unclear whether these changes are pervasive or whether they simply reflect the effect of short-term climatic fluctuations on tree growth. Assessing whether changes have occurred over centennial scales is thus crucial to understanding whether and how tropical forests are reacting to climatic changes.

In this thesis we apply tree-ring analysis on a pantropical study to assess longterm changes in growth of tropical forest trees. Tree-ring analysis was used to measure long-term growth rates of ~1350 trees of different species coming from three sites across the tropics. Trends in growth over the last two centuries were then analysed using an established an a new trend-detection method. Additionally, we applied the long-term growth data from rings to improve the evaluation of forest management practices in Cameroon. All samples were collected and measured within the TROFOCLIM project led by Pieter Zuidema. The project also includes two other PhD theses and sample collection was divided among the three PhD projects and the three sites: in Bolivia (samples collected by Peter van der Sleen), Cameroon (by me) and in Thailand (by Mart Vlam). The main objectives of this thesis were: (1) to assess the potential for using treerings in a wet tropical forest in Central Africa; (2) to project timber yields in the next logging round for four Cameroonian tree species; (3) to evaluate the sensitivity and accuracy of four commonly used methods to detect long-term trends in tree-ring data; and (4) to detect whether growth rates of tropical forest trees have changed over the past ~150 years.

In Chapter 2 of this dissertation, we evaluated whether growth rings are formed annually in the wood of tree species growing under very high levels of precipitation (>4000 mm) in an African tropical forest. For this purpose, we assessed whether ring structures are formed in the wood of the 22 commercially exploited tree species and found that ring structures are indeed formed by more than half of these species (in 14 species), though with varying ring clarity. On four species we proved the annual character of ring formation using radiocarbon bomb-peak dating. That rings are formed under such high levels of precipitation is surprising, as these conditions are considered improper to induce ring formation. These results suggest that the potential of tree-rings analysis is more or less similar across the tropics. Based on our results and that of other studies, we estimate that tree rings can be used to measure tree growth and ages for around a quarter to a third of tropical tree species.

Worldwide, over 400 million hectares of tropical forests are set aside for timber production. Attaining sustainable use of these forests is very important, in the light of the important role of tropical forests in retaining biodiversity and storing carbon. Ensuring that timber species are not overexploited is key to ensure that forest use is sustainable and entails finding a balance between economic gains and the (ecological) sustainability of logging operations. In Chapter 3, we integrated growth data from tree-rings with logging inventory data to forecast whether timber yields can be sustained in the next harvest round for four timber species in Cameroon. Under current logging practices, future logging yields were predicted to reduce moderately to strongly for all species. These yield reductions are worrisome for forest conservation, as loss of economic value may lead to conversion of forests to other land uses. We recommend that such calculations are needed for more species and argue that these simulations should include the effects of logging and eventual silvicultural measures on the growth and survival of trees.

Lifetime tree growth data – as acquired by tree-ring analysis – contains longterm trends in growth that reflect the ontogenetic development of an individual or species, i.e., these data contains an age/size signal in growth. In Chapter 4 we evaluate the sensitivity, accuracy and reliability to detect long-term trends in growth of four methods that are commonly used to disentangle these age/size trends from long-term growth trends. We applied these growth-trend detection methods to measured growth data from tree rings and to simulated growth trajectories on which increasing an decreasing trends were imposed. The results revealed that the choice of method influences results of growth-trend studies. We recommend applying two methods simultaneously when analysing long-term trends – the Regional Curve Standardization and Size Class Isolation – as these methods are complementary and showed the highest reliability to detecting long-term growth changes.

In Chapter 5, we analysed long-term growth trends in tropical forest trees using a pantropical approach applying the two recommended growth-trend detection methods. We showed that growth rates for most of the 13 tropical tree species, from the three sites across the tropics, decreased over the last centuries. These species-level changes may have important demographic consequences and may eventually lead to shifts in the species composition of tropical forests. We found no strong growth changes when analysing trends aggregated per site or across sites: only weak growth reductions were detected for the Thai site and across sites. These findings contrast growth increases that would be expected if tree growth is stimulated by increased ambient CO2. These growth reductions suggest worsening growth conditions for several tropical tree species, and could result from the negative effect of temperature increases on tree growth, or reflect the effect of large-scale disturbances on these forests.

If one image becomes clear from this thesis it is that long-term data are crucial to enhance the management of tropical forests and to quantify changes happening in these forests. Tree-ring analysis provides this long-term perspective for tree growth and is thus a great tool to evaluate changes in the growth of trees, including for tropical species. One of the most important finding of this thesis is that many tropical species show long-term decreases in growth. These results suggest that the commonly assumed growth increases tropical forests, based on measurements over the last couple of decades, may be incorrect. This discrepancy in results could have strong consequences, among others leading to erroneous predictions of the carbon dynamics of tropical forests under future climate change. Combining monitoring plot data (to analyse short-term changes in growth and species composition) with remotely sensed data (to accurately determine forest land cover) and with the long-term growth data from tree rings is probably the best way forward to relate recent findings of short-term changes in tree growth and forest biomass to changes over the past centuries. Such integrative approaches are needed to better quantify and understand the effects of climate change on tropical forests.

OHN : Object Hoogten Nederland, de hoogte van alles wat boven het maaiveld uitsteekt
Kramer, H. ; Clement, J. ; Mücher, C.A. - \ 2014
Geo-Info 2014 (2014)3. - ISSN 1572-5464 - p. 18 - 21.
bomen - gebouwen - meting - hoogte - gegevensbeheer - geografische informatiesystemen - trees - buildings - measurement - height - data management - geographical information systems
Op locaties waar geen hoogtemetingen beschikbaar zijn, bevat het AHN geen hoogtegegevens. Reden genoeg voor Alterra om een vlakdekkend bestand te maken met alle hoogten boven maaiveld: het bestand Object Hoogte Nederland (OHN). Met OHN is het mogelijk om de vraag te beantwoorden "hoe hoog is deze boom"
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