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.

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Approaches to the conservation of forest genetic resources in Europe in the context of climate change
Kelleher, Colin T. ; Vries, S.M.G. de; Baliuckas, Virgilijus - \ 2015
Rome : Biodiversity International - ISBN 9789292550325 - 46 p.
forest trees - genetic diversity - genetic resources - plant genetic resources - forest resources - climatic change - forest policy - bosbomen - genetische diversiteit - genetische bronnen - genetische bronnen van plantensoorten - bosbestanden - klimaatverandering - bosbeleid
In Europe, forests have been expanding in terms of area and timber stock over the past 50 years and subsequently they have acted as a carbon sink while they have been recovering from previous eras of deforestation. National adaptation strategies to climate change and other policies have been formulated in many European countries to harness the potential of forests and the forestry sector for mitigating climate change. However, the impacts of climate change on forests, and especially on their genetic diversity have not been given a proper consideration in these policies. For these reasons, the EUFORGEN Steering Committee established a working group on climate change and the conservation of forest genetic resources that made several recommendations for action presented in this report
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
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.

No growth stimulation of tropical trees by 150 years of CO2 fertilization but water-use efficiency increased
Sleen, J.P. van der; Groenendijk, P. ; Vlam, M. ; Anten, N.P.R. ; Boom, A. ; Bongers, F. ; Pons, T.L. ; Terburg, G. ; Zuidema, P.A. - \ 2015
Nature Geoscience 8 (2015). - ISSN 1752-0894 - p. 24 - 28.
rising atmospheric co2 - carbon-dioxide - climate-change - elevated co2 - forest trees - responses - ecosystems - vegetation - feedbacks - lessons
The biomass of undisturbed tropical forests has likely increased in the past few decades (1, 2), probably as a result of accelerated tree growth. Higher CO2 levels are expected to raise plant photosynthetic rates (3) and enhance water-use efficiency (4), that is, the ratio of carbon assimilation through photosynthesis to water loss through transpiration. However, there is no evidence that these physiological responses do indeed stimulate tree growth in tropical forests. Here we present measurements of stable carbon isotopes and growth rings in the wood of 1,100 trees from Bolivia, Cameroon and Thailand. Measurements of carbon isotope fractions in the wood indicate that intrinsic water-use efficiency in both understorey and canopy trees increased by 30–35% over the past 150 years as atmospheric CO2 concentrations increased. However, we found no evidence for the suggested concurrent acceleration of individual tree growth when analysing the width of growth rings. We conclude that the widespread assumption of a CO2-induced stimulation of tropical tree growth may not be valid.
Eutrophication of mangroves linked to depletion of foliar and soil base cations
Fauzi, A. ; Skidmore, A.K. ; Heitkonig, I.M.A. ; Gils, H. van; Schlerf, M. - \ 2014
Environmental Monitoring and Assessment 186 (2014)12. - ISSN 0167-6369 - p. 8487 - 8498.
northeastern united-states - avicennia-marina - ammonium-sulfate - shrimp farms - pond culture - forest trees - red spruce - nitrogen - nutrient - phosphorus
There is growing concern that increasing eutrophication causes degradation of coastal ecosystems. Studies in terrestrial ecosystems have shown that increasing the concentration of nitrogen in soils contributes to the acidification process, which leads to leaching of base cations. To test the effects of eutrophication on the availability of base cations in mangroves, we compared paired leaf and soil nutrient levels sampled in Nypa fruticans and Rhizophora spp. on a severely disturbed, i.e. nutrient loaded, site (Mahakam delta) with samples from an undisturbed, near-pristine site (Berau delta) in East Kalimantan, Indonesia. The findings indicate that under pristine conditions, the availability of base cations in mangrove soils is determined largely by salinity. Anthropogenic disturbances on the Mahakam site have resulted in eutrophication, which is related to lower levels of foliar and soil base cations. Path analysis suggests that increasing soil nitrogen reduces soil pH, which in turn reduces the levels of foliar and soil base cations in mangroves.
EUFORGEN - 20 years of pan-European collaboration
Vries, S.M.G. de; Hubert, J. - \ 2014
bossen - bosbestanden - bosbomen - genetische diversiteit - genetische bronnen - biodiversiteit - europa - forests - forest resources - forest trees - genetic diversity - genetic resources - biodiversity - europe
This video reflects some achievements of the pan-European collaboration on forest genetic resources since 1994. Two National Coordinators of EUFORGEN, Sven de Vries (Netherlands) and Jason Hubert (United Kingdom) share their experiences and explain why EUFORGEN is needed.
ABS Focal Point
Visser, L. - \ 2014
Wageningen : Wageningen UR
genetische bronnen van diersoorten - genetische bronnen van plantensoorten - bosbomen - genetische diversiteit - internationale verdragen - eu regelingen - nederland - onderzoek - ontwikkeling - animal genetic resources - plant genetic resources - forest trees - genetic diversity - international agreements - eu regulations - netherlands - research - development
This website of the ABS Focal Point of the Netherlands contains information that is relevant to all public institutes, companies and individuals using genetic resources for research and development. It provides basic guidance for Dutch and foreign users seeking access to genetic resources as well as background information on the relevant international agreements, and explains various terms that are often used.
Wood structural differences between northern and southern beech provenances growing at a moderate site
Eilmann, B. ; Sterck, F.J. ; Wegner, L. ; Vries, S.M.G. de; Arx, G. von; Mohren, G.M.J. ; Ouden, J. den; Sass-Klaassen, U.G.W. - \ 2014
Tree Physiology 34 (2014)8. - ISSN 0829-318X - p. 882 - 893.
fagus-sylvatica l. - climate-change - european beech - scots pine - phenotypic plasticity - forest trees - drought tolerance - quercus-petraea - pubescent oak - norway spruce
Planting provenances originating from southern to northern locations has been discussed as a strategy to speed up species migration and mitigate negative effects of climate change on forest stability and productivity. Especially for drought-susceptible species such as European beech (Fagus sylvatica L.), the introduction of drought-tolerant provenances from the south could be an option. Yet, beech has been found to respond plastically to environmental conditions, suggesting that the climate on the plantation site might be more important for tree growth than the genetic predisposition of potentially drought-adapted provenances. In this study, we compared the radial growth, wood-anatomical traits and leaf phenology of four beech provenances originating from southern (Bulgaria, France) and northern locations (Sweden, the Netherlands) and planted in a provenance trial in the Netherlands. The distribution of precipitation largely differs between the sites of origin. The northern provenances experience a maximum and the southern provenances experience a minimum of rainfall in summer. We compared tree productivity and the anatomy of the water-conducting system for the period from 2000 to 2010, including the drought year 2003. In addition, tree mortality and the timing of leaf unfolding in spring were analysed for the years 2001, 2007 and 2012. Comparison of these traits in the four beech provenances indicates the influence of genetic predisposition and local environmental factors on the performance of these provenances under moderate site conditions. Variation in radial growth was controlled by environment, although the growth level slightly differed due to genetic background. The Bulgarian provenance had an efficient water-conducting system which was moreover unaffected by the drought in 2003, pointing to a high ability of this provenance to cope well with dry conditions. In addition, the Bulgarian provenance showed up as most productive in terms of height and radial growth. Altogether, we conclude that the similarity in ring-width variation among provenances points to environmental control of this trait, whereas the differences encountered in wood-anatomical traits between the well-performing Bulgarian provenance and the other three provenances, as well as the consistent differences in flushing pattern over 3 years under various environmental conditions, support the hypothesis of genetic control of these features.
Genome-wide distribution of genetic diversity and linkage disequilibrium in a mass-selected population of maritime pine.
Plomion, C. ; Chancerel, E. ; Endelman, J. ; Lamy, J.B. ; Mandrou, E. ; Lesur, I. ; Ehrenmann, F. ; Isik, F. ; Bink, M.C.A.M. ; Heerwaarden, J. van; Bouffier, L. - \ 2014
BMC Genomics 15 (2014)1. - ISSN 1471-2164 - 17 p.
multilocus genotype data - loblolly-pine - forest trees - cryptomeria-japonica - density-estimation - cloned population - breeding values - complex traits - consensus map - white spruce
BACKGROUND: The accessibility of high-throughput genotyping technologies has contributed greatly to the development of genomic resources in non-model organisms. High-density genotyping arrays have only recently been developed for some economically important species such as conifers. The potential for using genomic technologies in association mapping and breeding depends largely on the genome wide patterns of diversity and linkage disequilibrium in current breeding populations. This study aims to deepen our knowledge regarding these issues in maritime pine, the first species used for reforestation in south western Europe. RESULTS: Using a new map merging algorithm, we first established a 1,712 cM composite linkage map (comprising 1,838 SNP markers in 12 linkage groups) by bringing together three already available genetic maps. Using rigorous statistical testing based on kernel density estimation and resampling we identified cold and hot spots of recombination. In parallel, 186 unrelated trees of a mass-selected population were genotyped using a 12k-SNP array. A total of 2,600 informative SNPs allowed to describe historical recombination, genetic diversity and genetic structure of this recently domesticated breeding pool that forms the basis of much of the current and future breeding of this species. We observe very low levels of population genetic structure and find no evidence that artificial selection has caused a reduction in genetic diversity. By combining these two pieces of information, we provided the map position of 1,671 SNPs corresponding to 1,192 different loci. This made it possible to analyze the spatial pattern of genetic diversity (He) and long distance linkage disequilibrium (LD) along the chromosomes. We found no particular pattern in the empirical variogram of He across the 12 linkage groups and, as expected for an outcrossing species with large effective population size, we observed an almost complete lack of long distance LD. CONCLUSIONS: These results are a stepping stone for the development of strategies for studies in population genomics, association mapping and genomic prediction in this economical and ecologically important forest tree species.
High rates of gene flow by pollen and seed in oak populations across Europe
Gerber, S. ; Chadoeuf, J. ; Gugerli, F. ; Lascoux, M. ; Buiteveld, J. ; Cottrell, J. ; Dounavi, A. ; Fineschi, S. ; Forrest, L. ; Fogelqvist, J. ; Goicoechea, P.G. ; Jensen, J.S. ; Salvini, D. ; Vendramin, G.G. ; Kremer, A. - \ 2014
PLoS ONE 9 (2014)1. - ISSN 1932-6203
torminalis l. crantz - quercus-petraea - paternity analysis - bur oak - reproductive success - parentage analysis - dispersal kernel - wildservice tree - forest trees - patterns
Gene flow is a key factor in the evolution of species, influencing effective population size, hybridisation and local adaptation. We analysed local gene flow in eight stands of white oak (mostly Quercus petraea and Q. robur, but also Q. pubescens and Q. faginea) distributed across Europe. Adult trees within a given area in each stand were exhaustively sampled (range [239, 754], mean 423), mapped, and acorns were collected ([17,147], 51) from several mother trees ([3,47], 23). Seedlings ([65,387], 178) were harvested and geo-referenced in six of the eight stands. Genetic information was obtained from screening distinct molecular markers spread across the genome, genotyping each tree, acorn or seedling. All samples were thus genotyped at 5–8 nuclear microsatellite loci. Fathers/parents were assigned to acorns and seedlings using likelihood methods. Mating success of male and female parents, pollen and seed dispersal curves, and also hybridisation rates were estimated in each stand and compared on a continental scale. On average, the percentage of the wind-borne pollen from outside the stand was 60%, with large variation among stands (21–88%). Mean seed immigration into the stand was 40%, a high value for oaks that are generally considered to have limited seed dispersal. However, this estimate varied greatly among stands (20–66%). Gene flow was mostly intraspecific, with large variation, as some trees and stands showed particularly high rates of hybridisation. Our results show that mating success was unevenly distributed among trees. The high levels of gene flow suggest that geographically remote oak stands are unlikely to be genetically isolated, questioning the static definition of gene reserves and seed stands.
Loofbomen in Nederland en Vlaanderen : soorten en hybriden
Goudzwaard, L. - \ 2013
Zeist : KNNV - ISBN 9789050114325 - 432
loofhout - bosbomen - bomen - soorten - identificatie - foto's - habitus - vlaanderen - nederland - taxonomie - broadleaves - forest trees - trees - species - identification - photographs - habit - flanders - netherlands - taxonomy
Loofbomen van Nederland en Vlaanderen beschrijft 268 verschillende boomsoorten en hybriden en 400 verschillende variëteiten waaronder tal van boomgeslachten, zoals Acer (esdoorn), Fagus (beuk), Magnolia, Malus (appel) en Quercus (eik), maar ook minder bekende boomsoorten, zoals venkelhout (Sassafras albidum) en lederboom (Ptelea trifoliata).H erkenning, gebruik en ziektegevoeligheid komen aan bod, maar ook de geschiedenis van het boomgeslacht en de plaatsen waar prachtige exemplaren van de soort te zien zijn. In dit boek leest u waar u complete collecties van boomgeslachten kunt bekijken, evenals monumentale bomen.
Special topic: integrating modelling and experimentation
Matyssek, R. ; Mohren, G.M.J. - \ 2012
Trees-Structure and Function 26 (2012)6. - ISSN 0931-1890 - p. 1679 - 1682.
forest trees
Tree-growth analyses to estimate tree species' drought tolerance
Eilmann, B. ; Rigling, A. - \ 2012
Tree Physiology 32 (2012)2. - ISSN 0829-318X - p. 178 - 187.
pinus-sylvestris l. - scots pine - forest trees - picea-abies - climate - water - mortality - soil - switzerland - responses
Climate change is challenging forestry management and practices. Among other things, tree species with the ability to cope with more extreme climate conditions have to be identified. However, while environmental factors may severely limit tree growth or even cause tree death, assessing a tree species' potential for surviving future aggravated environmental conditions is rather demanding. The aim of this study was to find a tree-ring-based method suitable for identifying very drought-tolerant species, particularly potential substitute species for Scots pine (Pinus sylvestris L.) in Valais. In this inner-Alpine valley, Scots pine used to be the dominating species for dry forests, but today it suffers from high drought-induced mortality. We investigate the growth response of two native tree species, Scots pine and European larch (Larix decidua Mill.), and two non-native species, black pine (Pinus nigra Arnold) and Douglas fir (Pseudotsuga menziesii Mirb. var. menziesii), to drought. This involved analysing how the radial increment of these species responded to increasing water shortage (abandonment of irrigation) and to increasingly frequent drought years. Black pine and Douglas fir are able to cope with drought better than Scots pine and larch, as they show relatively high radial growth even after irrigation has been stopped and a plastic growth response to drought years. European larch does not seem to be able to cope with these dry conditions as it lacks the ability to recover from drought years. The analysis of trees' short-term response to extreme climate events seems to be the most promising and suitable method for detecting how tolerant a tree species is towards drought. However, combining all the methods used in this study provides a complete picture of how water shortage could limit species.
Dryland resources, livelihoods and institutions : diversity and dynamics in use and management of gum and resin trees in Ethiopia
Teshale Woldeamanuel Habebo, Teshale - \ 2011
Wageningen University. Promotor(en): Bas Arts; Frans Bongers, co-promotor(en): Freerk Wiersum. - [S.l.] : S.n. - ISBN 9789085859628 - 170
bosbomen - gomleverende planten - acacia - boswellia - commiphora - bosproducten anders dan hout - bosbouw - bosexploitatie - bosbedrijfsvoering - ethiopië - forest trees - gum plants - non-wood forest products - forestry - forest exploitation - forest management - ethiopia
Dry woodlands comprise the largest forest resources in Ethiopia. An important feature of these forests is their richness in Acacia, Boswellia and Commiphora (ABC) species that produce gum and resin. Gums/resins significantly contribute to rural livelihoods, the national economy, and ecosystem stability. Their contribution to local livelihoods is in terms of both cash income and subsistence value. In different parts of the country they contribute up to one-third of the annual household income. Currently, an estimated US2 million gum and resin are consumed locally, the rest is exported. During the 2007/08 fiscal year, Ethiopia earned a revenue of about US.7 million from this export. However, the woodlands and the ABC species are under intense pressure. Especially in the traditional production areas in north Ethiopia the pressure is high and the policies that were enacted to shape their use and management have not been very effective. The main objective of this study is to investigate how gum and resin utilization and management is carried out in the drylands of Ethiopia and what processes affect this. The following four questions were addressed: (i) What types of gum-resin woodland management and production systems are present in Ethiopia and how are they related to the land-use and socio-political conditions?, (ii) What dynamic processes in institutional arrangements and gum-resin production and management have occurred in various regions of Ethiopia?; (iii) How do multi-level formal and informal institutions interact and affect gum and resin production and management?, and (iv) How does gumresin utilization fits into the livelihoods strategies of households in the study areas? The study is based on a multi-theoretical approach giving attention to both diversity and dynamics in ABC woodlands production systems, institutional diversity and interaction regarding the governance of ABC resources, and the role of gum and resin in the livelihoods strategies of the households. The study design consisted of a comparative case study of three regions in north (Abergelle), northwest (Metema and Quara), and south Ethiopia (Borana). The three locations are characterized by ecological and socio-economic differences as well as a different history of gum and resin production. A two-phase research approach consisting of a base-line survey and a systematic household survey was used. The base-line survey served to assess the local socio-economic, institutional and land-use conditions; data were collected through open interviews with groups and key informants. The household survey served to obtain further detailed information on the ABC production conditions and the role of the products at household level. The survey included 327 respondents; it was follow-up by feedback meetings with groups of participants to check and validate the main issues that emerged from it. The qualitative data from key informant interviews and focus group discussion were transcribed, categorized, and interpreted. The data from household survey was analysed using descriptive statistics and mean comparisons in SPSS. Chapter 2 discusses the diversity in gum and resin management and production systems and how different exploitation arrangements are related to different phases of resource domestication and/or degradation. Seven presently existing production models are identified. In south Ethiopia pastoral people mainly collect the products in the form of ooze from natural vegetation. In north Ethiopia the production is part of mixed farming practices or is done by externally hired laborers. Production is done by tapping wild trees. Despite decades of production history in this region, the species is not cultivated and hardly domesticated in an ecological or biological sense. The production systems gradually evolved from openaccess extraction of wild trees to a controlled production in assigned forest plots. This institutionalisation of access rules concerns a process of domestication in a social sense. However, this process is not yet very effective; the ABC woodlands are often subject to serious degradation as a result of competing land-use practices and inappropriate social arrangements for production and trade of the gums/resins. These findings show that the nature of domestication in a social sense determines whether forests and/or specific forest resources can be further domesticated in an ecological and biological sense resulting in intensified management and resource enrichment, or whether they are subject to degradation. Chapter 3 and 4 elaborate how gum and resin production is shaped in the different parts of Ethiopia by the location-specific interaction between formal and informal institutions. Chapter 3 discusses how gum and resin production and marketing in Borana is related to the interplay between well-established traditional land-use institutions and external institutions. Both the traditional and external institutions do not explicitly control access to the gum and resin production system, but under traditional conditions gum and resin extraction was embedded in a strong customary system for controlled pastoral land use. The traditional institutions did not developed rules and norms regulating market access. The external institutions impacted gum and resin production mainly by creating access to markets, but this has not yet had much impact on the actual exploitation arrangements. The woodlands are experiencing increasing pressure due to the increase in non-traditional and non-gum and resin based livelihoods activities that negatively affect ABC woodlands. Also, the traditional natural resources management institutions are weakened due to modernization processes and contribute at present little to sustainable use and management of gum-resin resources. This situation calls for either revitalizing the traditional range land management system, or generating institutions specific to ABC species that integrate the customary and external institutions. Chapter 4 discusses the nature and interactions of formal and informal institutions concerning the AB resource use and management in the north and northwest Ethiopia. Existing government regulations recognize gum and resin production and marketing by both smallholders, cooperatives, and companies. However, in practice gum and resin production and marketing by smallholders is restricted. This is the result of informal bureaucratic institutions that act as rules-in-use regarding gum and resin production and marketing regardless of whether they contradict with the regulations of federal and regional states. Moreover, the customary rules and practices and the sectoral government policies often compete with the formal regulations for ABC species use and management. The interaction between government regulations and informal institutions is generally competing; this often results in indiscriminate tree cutting and woodland conversion. The situation requires harmonization of the formal and informal institutions and coordination of institutions across sectors. Chapter 5 discusses the relationship between gum and resin production and the livelihood systems of local producers. Both the livelihoods systems and the contribution of the multiple activities to cash and total income vary among the study areas. In Borana the use of gum and resin is part of a predominantly pastoral livelihood system with gum and resin acting as supplementary cash crops or safety nets in times of emergency. In Abergelle the production fits into a diversification strategy with gum and resin exploitation forming a component of a mixed farming system. In Metema local farmers were not involved in gum and resin exploitation; here production is a specialized activity of commercial enterprises using laborers from outside the region. The findings show that not only the value of the ABC resources, but also the degree of the embeddedness of the product in multi-livelihoods strategies of the households as well as the institutional arrangements that govern production system and market access are important regarding how these products fit into the livelihoods strategies of the households. Chapter 6 brings all the information together and further assesses the nature of the different institutional arrangements for gum and resin exploitation, and their dynamics and interaction. It also elaborates the relation between the status of ABC resource domestication and their exploitation arrangements. The process of organizing gum and resin utilization followed different pathways in north and south Ethiopia. In the south it started as the collection of products for chewing gum for subsistence use; later it was marketed as a coping mechanism during periods of livelihood stress. In contrast to these endogenous developments, in the north the production was introduced by external private and state companies. Only gradually also some informal systems of private exploitation evolved. After 1990 cooperatives took over many of the concession areas of the commercial companies. This cooperative movement also was introduced in the south. As a result of these location-specific dynamics in organizing the production, six exploitation arrangements evolved. These arrangements differ with respect to whether their organization is companybased, cooperative-based or privately based, and are characterized by different rules and regulations regarding access to resources and markets, and the type of labor used for production. In all study areas the exploitation arrangements co-exist with a growing importance of the cooperative arrangements. The institutional arrangements are not conducive to stimulate intensification of production, rather they may limit local participation and endogenous development of informal and location-specific institutions. Moreover, the effectiveness of the exploitation arrangements may be limited as a result from competing development policies and programmes aimed at other land-use sectors. These findings further illustrate that the limited progress in ABCs domestication greatly depends on the nature of institutional arrangements for access to resources and markets, the relation of formal and informal institutional arrangements, and development polices. In chapter 7 it is concluded that the use and management of the ABC species in Ethiopia is very divers both in terms of production systems, institutional arrangements for exploitation, and roles in local livelihoods. The nature of location-specific production systems is greatly affected by the local system for ABC governance. Such a system involves complex set of both formal and informal institutions at both government level and local level. The informal institutions do not only include customary institutions of local communities, but also informal rules-in-use of local bureaucrats. The historic process of institutionalisation of ABC governance differs between regions. Depending on local land-use conditions and government policies, different exploitation arrangements have been developed based on either company, cooperative or private control over the production, labor and marketing. But despite of this diversified stage of domestication in a social sense, the production systems are still in an early phase of domestication in ecological and technical sense and intensified production through tree cultivation or plantation establishment has hardly been developed. Several gum and resin production systems are even subject to serious degradation due to the inappropriate nature of, and sometimes even competition between, the exploitation arrangements, as well as the economic position of the ABC resources in relation to other forms of land-use. The complex pattern of institutions governing the production of gum and resin also impacts on the role that the resources play in local livelihoods. Both the role of gum and resin production in the prevailing land-use conditions and the degree of control on market and resource access determine how the gum and resin fit into the livelihoods strategies of the households. As the governance of gum and resin production involves a complex, diverse and dynamic web of formal and informal institutions, it will not be effective to stimulate production as a means for both sustainable forest use and livelihood improvement by a generic development policy. Rather a diversified and regional-specific approach is needed that builds upon the location specific characteristics of the gum and resin production systems and exploitation arrangements.
De zwarte els in Nederland
Oosterbaan, A. ; Polman, J.E. - \ 2011
Groen : vakblad voor groen in stad en landschap 67 (2011)1. - ISSN 0166-3534 - p. 44 - 47.
alnus - alnus glutinosa - bomen - bosbomen - straatbomen - geschiedenis - twente - achterhoek - historische ecologie - trees - forest trees - street trees - history - historical ecology
De zwarte els is een belangrijke boomsoort voor ons landschap. Hij is zelfs bepalend voor het landschap van grote delen van ons land. Bijvoorbeeld in het van oudsher dichte singellandschap van de Friese Wouden, de kop van Overijssel, delen van Twente en de Achterhoek. Maar ook in het westelijke veenweidengebied kwamen van oorsprong veel elzensingels voor. Verder tref je de zwarte els aan in al of niet gemengde bomenrijen, als knotboom en als solitair.
Nieuwe autochtone herkomsten van fladderiep en boskers op de Rassenlijst Bomen
Buiteveld, J. ; Vries, S.M.G. de - \ 2010
Vakblad Natuur Bos Landschap 7 (2010)5. - ISSN 1572-7610 - p. 26 - 27.
bomen - rassen (planten) - ulmus laevis - houtachtige planten als sierplanten - prunus avium - bosbomen - rassenlijsten - trees - varieties - ornamental woody plants - forest trees - descriptive list of varieties
De aanbevelende Rassenlijst Bomen bevat twee nieuwe herkomsten van fladderiep (Ulmus laevis) en een nieuwe herkomst van boskers (Prunus avium). De Raad voor plantenrassen en het Bosschap maakten dit bekend. Het gaat in alle drie de gevallen om genenbankmateriaal dat is opgenomen in de categorie 'naar herkomst geïdentificeerd'.
Lindespintmijt veroorzaakt veel bladverkleuring : landelijke inventarisatie insectenplagen 2008
Moraal, L.G. - \ 2009
Tuin en Landschap 31 (2009)19. - ISSN 0165-3350 - p. 36 - 39.
tetranychidae - anoplura - insectenplagen - afwijkingen, planten - inventarisaties - bosbomen - houtachtige planten als sierplanten - insect pests - plant disorders - inventories - forest trees - ornamental woody plants
Aantastingen door lindespintmijt en overlast door stamluizen zijn het meest opvallend in de landelijke inventarisatie van insectenplagen op bomen en struiken. Verder waren er veel aardappelgallen. De paardenkastanjemineermot werd het meest gemeld en staat dus bovenaan in de Insecten top tien
Ziekte- en plaagdruk in 2009
Dijk, A. van; Kuik, A.J. van; Tol, R. van der - \ 2009
De Boomkwekerij 22 (2009)49. - ISSN 0923-2443 - p. 8 - 9.
tetranychidae - cecidomyiidae - natuurlijke vijanden - bosbomen - bladvlekkenziekte - thysanoptera - meeldauw - ziektebestrijding - plagenbestrijding - natural enemies - forest trees - leaf spotting - mildews - disease control - pest control
Een overzicht van de belangrijkste ziekten en plagen die het afgelopen jaar de boomkwekerij parten speelden
EVOLTREE : EVOLution of TREEs as drivers of terrestrial biodiversity
Anonymous, - \ 2009
forest trees - europe - data management - diversity - forest ecology
Acer platanoides: hoog gewaardeerd, veel gebruikt
Sluis, B.J. van der; Schalk, G. ; Hiemstra, J.A. - \ 2008
De Boomkwekerij 21 (2008)31/32. - ISSN 0923-2443 - p. 22 - 24.
straatbomen - aantrekkelijke bomen - houtachtige planten als sierplanten - bosbomen - acer platanoides - gebruikswaarde - onderzoek - soorten - cultivars - street trees - amenity trees - ornamental woody plants - forest trees - use value - research - species
In het gebruikswaardeonderzoek laanbomen zijn maar liefst 13 soorten en cultivars van Acer opgenomen, want het geslacht Acer kent een grote variëteit aan goede soorten en cultivars, de boom voldoet goed langs de straat en het aantal verschijningsvormen is groot. In onderstaand artikel de ervaringen met deze populaire soort. Met tips voor een goede opkweek van Acer platanoides.
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