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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    Data from: Towards smarter harvesting from natural palm populations by sparing the individuals that contribute most to population growth or productivity
    Jansen, M. ; Anten, N.P.R. ; Bongers, F. ; Martínez-Ramos, Miguel ; Zuidema, P.A. - \ 2018
    Wageningen University & Research
    Chamaedorea - forest management - harvest simulations - individual heterogenity - Integral Project Model - leaf harvesting - NFTP - sustainability - Chamaedorea elegans
    1. Natural populations deliver a wide range of products that provide income for millions of people and need to be exploited sustainably. Large heterogeneity in individual performance within these exploited populations has the potential to improve population recovery after exploitation and thus help sustaining yields over time. 2. We explored the potential of using individual heterogeneity to design smarter harvest schemes, by sparing individuals that contribute most to future productivity and population growth, using the understorey palm Chamaedorea elegans as a model system. Leaves of this palm are an important non-timber forest product and long-term inter-individual growth variability can be evaluated from internode lengths. 3. We studied a population of 830 individuals, half of which was subjected to a 67 % defoliation treatment for three years. We measured effects of defoliation on vital rates and leaf size – a trait that determines marketability. We constructed integral projection models in which vital rates depended on stem length, past growth rate, and defoliation, and evaluated transient population dynamics to quantify population development and leaf yield. We then simulated scenarios in which we spared individuals that were either most important for population growth or had leaves smaller than marketable size. 4. Individuals varying in size or past growth rate responded similarly to leaf harvesting in terms of growth and reproduction. By contrast, defoliation-induced reduction in survival chance was smaller in large individuals than in small ones. Simulations showed that harvest-induced population decline was much reduced when individuals from size and past growth classes that contributed most to population growth were spared. Under this scenario cumulative leaf harvest over 20 years was somewhat reduced, but long-term leaf production was sustained. A three-fold increase in leaf yield was generated when individuals with small leaves are spared. 5. Synthesis and applications This study demonstrates the potential to create smarter systems of palm leaf harvest by accounting for individual heterogeneity within exploited populations. Sparing individuals that contribute most to population growth ensured sustained leaf production over time. The concepts and methods presented here are generally applicable to exploited plant and animal species which exhibit considerable individual heterogeneity.
    Socio-ecological analysis of multiple-use forest management in the Bolivian Amazon
    Soriano Candia, Marlene - \ 2017
    Wageningen University. Promotor(en): G.M.J. Mohren, co-promotor(en): M. Peña Claros; N. Ascarrunz. - Wageningen : Wageningen University - ISBN 9789463436557 - 220
    forest management - timber production - nuts - multiple use - bertholletia excelsa - forest ecology - amazonia - sustainability - community forestry - bosbedrijfsvoering - houtproductie - noten - meervoudig gebruik - bertholletia excelsa - bosecologie - amazonia - duurzaamheid (sustainability) - gemeenschapsbosbouw

    Community families throughout tropical regions derive an important share of their income from multiple forest products, with generally positive outcomes on their livelihoods. The production of these products in a multiple-use forest management scheme (MFM, the production of multiple forest products within a single management unit) encompasses many (yet) unknown socioeconomic and ecological feedbacks. In particular, MFM entailing timber and non-timber production may be affecting the future availability of valuable timber and non-timber tree species due to the extraction of vital plant components, which may have undesired outcomes on the income that community families derive from forests. In this thesis, I evaluated the social, economic, and ecological viability of an important MFM scheme widely practiced by community households in the Bolivian Amazon: the production of Amazon or Brazil nut (Bertholletia excelsa) and timber from other tree species. Data was obtained from a two-year (2014 and 2015) survey questionnaires of 24 community households in six campesino communities with community forest management plans (CFMPs) and from ecological surveys of 72 2 ha permanent research transects (three transects per household forest) harvested at varying Amazon nut and logging intensities. A CFMP entails the planning and execution of logging activities in compliance with formal rules intended to secure the long-term provision of timber at community-owned forest. Household-level decisions to harvest Amazon nut and to log timber allowed us to account for household forest as our sampling unit. We used multi-model inference and structural equation modelling techniques to determine the impact of socio-ecological factors on the income that community families derived from Amazon nut and timber (chapter 2), and regression and matrix modelling techniques to determine the impact of Amazon nut harvest and logging intensity on Bertholletia (chapter 3) and commercial timber species (chapter 4).

    In general, we found that few socioeconomic and biophysical factors of community households, together with a general positive response of studied species to timber logging and customary silvicultural intervention, make the production of Amazon nut and timber production of other tree species viable in a MFM scheme. In chapter 2, we found that community households could reduce their dependency on forest resources by increasing income opportunities from other existing livelihood activities. Amazon nut represented the largest source of household income (44% of the total household net income); and off-farm (salary, business and gifts; 21%), husbandry (generally subsistence agriculture, animal rising, and agroforestry; 21%), and timber (9%) incomes were complementary to their livelihood. Increased skills and ecological knowledge of community households enhanced household income derived from forest products. For example, an increase in the number of management practices reduced the need for timber income by increasing Amazon nut production; decreasing further pressure on timber of other tree species.

    In chapter 3, logging intensity was found to increase Bertholletia’s seedlings and saplings growth rate, and liana cutting was found to increase Amazon nut production rate. Both, logging and liana cutting intensities played a key role on Bertholletia population growth rate. Increased logging and liana cutting intensities counteracted the negative impact of Amazon nut harvesting intensity on the number of new recruits (i.e., due to nut harvest), indicating a trade-off between logging, liana cutting and Amazon nut harvesting intensities.

    Considering the overall stem density of commercial timber species (chapter 4), we found that 17% of the species present at unlogged sites (3 species out of 17: Swietenia macrophylla, Tabebuia impetiginosa and Terminalia sp.) were not present at sites six years after logging; and a larger percentage (71%) of the species present at unlogged sites in the harvestable size (trees>minimum diameter cutting – MDC) were not present at sites six years after logging, e.g., Cedrela spp. Stem density and timber volume of five of the eight most abundant commercial timber species under study differed among community-owned forests, after accounting for the effects of logging intensity and time since logging as indicated by our best models; whereas, potentially harvestable and harvestable timber volume differed between communities for only two and three species, respectively. Best models indicated that logging intensity increased either stem density or timber volume of Apuleia leiocarpa, Cedrela odorata, Dipteryx micrantha and Hymenaea parvifolia, decreased potentially harvestable timber volume of T. serratifolia, and had no effect on the other three species investigated. We also investigated the impact of logging intensity on congeneric species given that lumping congeneric species for logging is a common simplification during forest inventories and censuses, and is accepted in CFMPs assuming that closely related species respond to timber logging in a similar way. However, logging intensity had a differentiated effect on congeneric species. Logging intensity favoured growth rate of C. odorata trees >10 cm DBH and had no effects on Cedrela fissilis. Regarding Hymenaea congeneric species, logging intensity favoured H. parvifolia survival of individuals <10 cm DBH, but decreased growth rates of H. courbaril trees >10 cm DBH.

    In conclusion, Amazon nut harvest and timber logging of other tree species are compatible under certain socioeconomic and biophysical conditions, and as long as commercial timber species differential response to harvesting are accounted for in managing these species in a MFM scheme. This compatibility is due to existing socioeconomic complementarity of both activities and to the positive impact of logging intensity levels as practiced in the region on Amazon nut production and on most commercial timber species. Community families’ better negotiation skills to obtain better prices for Amazon nut, and increased implementation of management practices to increase Amazon nut production (e.g., liana cutting) helped families to increase their income and also decrease pressure on timber. These results highlight the need to look at both socioeconomic and ecological aspects when assessing the long-term sustainability of MFM schemes.

    Results of this research have important implications for policy to support the sustainable development of community forestry in the Bolivian Amazon. The compatibility found between Amazon nut and timber production calls for the investigation of the compatibility of timber production with other valuable NTFPs commonly harvested by community families throughout the tropics. We argue that management needs to be done at species-specific level, rather than at the level of products or at the level of species groups. This may result prohibitively expensive for communities and smallholders. Thus, we urge governments and the international community to revalorize local ecological knowledge of community people to manage their forests, while supporting the development of technologies, such as the ones based on hyperspectral LiDAR technology, to develop tools that could help reduce management costs of tropical forests at the required level. Such policies need to be accompanied by capacity building programs on different management tasks and negotiation skills to enhance the income obtained from MFM schemes. The research approaches used here could be used in other contexts and scales involving natural resources management to get a better understanding of the systems.

    Administrative co-management in special use forests of Vietnam
    Dung, Nguyen Kim - \ 2017
    Wageningen University. Promotor(en): Arthur Mol, co-promotor(en): Simon Bush. - Wageningen : Wageningen University - ISBN 9789462579866 - 183
    forests - forest administration - forest management - nature conservation - environmental protection - vietnam - bossen - bosbeheer - bosbedrijfsvoering - natuurbescherming - milieubescherming - vietnam

    To protect its natural heritage and biodiversity, Vietnam has established a system of ‘special use forest’ (SUFs) which is “the backbone of the national protected areas”. The ineffective management of SUFs based solely on the state leads to a decline in biodiversity and density of the forests. Recognizing this, collaborative or ‘co’-management for SUFs is advocated to get more participation and shared responsibilities and rights between government and non-state actors. However, it is widely noted that co-management is a particularly great challenge in Vietnam because of the nature of strong state control, decades of SUF conflicts, and the lack of capacity and initiatives of communities to negotiate with the government in co-management arrangements. This PhD thesis questions the degree to which co-management can be put in Vietnamese SUFs and the degree of ‘adaptiveness’ it can engender. Conditions of the economic, political and social context surrounding SUFs becomes key to any understanding of how co-management can be implemented, including insights into how co-management may need to be amended to adjust to ‘fit’ the context of mono-organisational states.

    EUROBATS : Analyse van de resoluties die zijn aangenomen tijdens de vergadering van de partijen (Meeting of the Parties) in 2014
    Ottburg, F.G.W.A. ; Adrichem, N.H.C. van; Limpens, H.J.G.A. ; Schillemans, M.J. - \ 2016
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport ) - 31
    chiroptera - wildbescherming - monitoring - bosbedrijfsvoering - milieubeleid - nederland - chiroptera - wildlife conservation - monitoring - forest management - environmental policy - netherlands
    Nederland is Party van ‘the Agreement on the Conservation of Populations of European Bats’, ofwel EUROBATS. De EUROBATS-agreement is een verdrag onder de conventie van Bern en met name de conventie van Bonn, de ‘Convention on the Conservation of Migratory Species of Wild Animals’. EUROBATS is een instrument bij de uitvoering van de verplichtingen vanuit de Europese Habitatrichtlijn. De Scientific Advisory Committee ontwikkelt resoluties, welke door de overheden van de Party-States van de EUROBATS-Agreement gezamenlijk worden aangenomen. Deze resoluties benoemen – specifiek vanuit de ecologie van de vleermuizen – knelpunten, speciale aandachtspunten en kansen, welke helpen de uitvoering van wet- en regelgeving in het kader van de Flora- en faunawet en Habitatrichtlijn effectief te focussen. De voorliggende rapportage geeft een overzicht van de resoluties en maakt inzichtelijk wat de Rijksoverheid, provincies of andere organisaties reeds doen voor vleermuizen. Tevens is een kennisagenda opgenomen met aanbevelingen ten behoeve van vleermuizen voor de nabije toekomst.
    Boseigendom in Twente en Salland : resultaten van een enquête onder kleine boseigenaren in Twente en Salland
    Clerkx, A.P.P.M. ; Hengeveld, G.M. ; Schelhaas, M. ; Helmink, A.T.F. - \ 2016
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2731) - 57
    bossen - bosbezit - bosbedrijfsvoering - biomassa - opbrengsten - salland - twente - forests - forest ownership - forest management - biomass - yields - salland - twente
    In de regio Twente/Salland is onderzoek uitgevoerd naar het boseigendom en motivatie van boseigenaren. Alle eigenaren met bosbezit van ten minste 0,5 ha hebben een enquête ontvangen met persoonlijke vragen over de eigenaar, het eigendom, beheer en oogst. Daarnaast is gekeken hoe gevoelig de eigenaren zijn voor verschillende strategieën die gericht zijn op vergroting van de houten biomassaoogst uit hun bos. Met deze antwoorden is voor de regio een indeling in eigenaarsgroepen gemaakt. Voor elke groep is een schatting gemaakt van het effect van de mobilisatiestrategieën en de hoeveelheid extra te mobiliseren hout.
    Biodiversity and the functioning of tropical forests
    Sande, M.T. van der - \ 2016
    Wageningen University. Promotor(en): Lourens Poorter, co-promotor(en): Marielos Pena Claros; Eric Arets. - Wageningen : Wageningen University - ISBN 9789462578029 - 282
    tropical forests - biodiversity - forest ecology - forest management - climatic change - tropische bossen - biodiversiteit - bosecologie - bosbedrijfsvoering - klimaatverandering

    Tropical forests are the most diverse terrestrial ecosystems. Moreover, their capacity for removal of carbon from the atmosphere makes them important for climate change mitigation. Theories predict that species use resources in a different way, and therefore high species diversity would result in more efficient resource use and higher total carbon removal. These theories, however, have yet not been clearly demonstrated for tropical forests. In this thesis, I evaluated how biodiversity of plants and their traits influenced carbon removal. I used data collected in different tropical forest types and at different spatial and temporal scales. I found that biodiversity was important for carbon removal especially at large spatial scales (e.g. the Amazon) where biodiversity varies strongly, and at long temporal scales (e.g. >200 years) where high biodiversity functions as a buffer for changing environmental conditions. In this way biodiversity contributes to long-term stable forests and a safe climate.

    Ghana's high forests : trends, scenarios and pathways for future developments
    Oduro, K.A. - \ 2016
    Wageningen University. Promotor(en): Frits Mohren; Bas Arts, co-promotor(en): B. Kyereh. - Wageningen : Wageningen University - ISBN 9789462577824 - 171
    forests - forest ecology - forest management - high forest system - forest resources - forestry - ghana - bossen - bosecologie - bosbedrijfsvoering - hoog opgaand bos - bosbestanden - bosbouw - ghana

    Deforestation and forest degradation in the tropics have been receiving both scientific and political attention in recent decades due to its impacts on the environment and on human livelihoods. In Ghana, the continuous decline of forest resources and the high demand for timber have raised stakeholders concerns about the future timber production prospects in the country. The principal drivers of deforestation and forest degradation in Ghana are agricultural expansion (50%), wood harvesting (35%), population and development pressures (10%), and mining and mineral exploitation (5%). Various measures are being pursued that are targeted at addressing the drivers of deforestation and forest degradation and at increasing the forest resource base. Understanding the key driving forces behind current forest resource development trends will help to gain insights into the possible courses of action to take to improve the developments of the resources, especially where actions that are being taken today will have an impact on the forest resources for many years to come.

    In this thesis, I used interdisciplinary research methods to provide insights into the current status of the forest resource base in Ghana and into its likely and possible future developments. I addressed 5 research questions: (1) What are the trends and changes associated with the growing stock in the timber production areas? (2) What driving forces account for current trends and future developments of timber resources in Ghana? (3) What different scenarios can be identified and how will these affect future developments of timber resources in the high forest zone? (4) What factors motivate farmers to engage in on-farm tree planting and management? (5) To what extent do the current trends of forest resources drive forest transition in Ghana?

    National forest inventory data, timber harvesting data and forest plantation establishment data showed that the growing stock in both on- and off-reserve production areas have been declining since 1990. Ghana’s average forest growing stock of 40m3 per ha is much lower than the 195 m3 per ha for the Western and Central Africa sub-region. Timber harvesting records also indicate that, in recent decades, total timber harvests have mostly been substantially higher than the annual allowable cut, resulting in an increasing gap between national timber demand and supply, which drives illegal logging. Current plantation establishment efforts are not sufficient to bridge the gap between demand and supply of timber, partly due to low establishment rates and lack of appropriate management of newly established plantations. Forest governance system and resource demand are the two key driving forces that affect the current trends and future developments of forest resources in the high forest zone of Ghana. Four scenarios were developed: (1) legal forestry scenario with emphasis on improving the resource base to meet high demand; (2) forest degradation, which implies a business-as-usual scenario; (3) forest transition, with emphasis on expanding the resource base in response to environmental concerns; and (4) timber substitution scenario seeking to provide wood substitutes to conserve the resource base. Across two on-farm tree planting schemes, I found that financial benefits, educational campaigns by project teams, knowledge about current environmental issues, ownership of timber for family use and access to land, grants, farming inputs, seedlings, capacity building, and market for agricultural produce are the factors that motivated farmers to engage in on-farm tree planting and management. Currently, there is no strong force toward a forest transition through any of the five generic pathways (economic development; forest scarcity; globalization; state forest policy; and smallholder, tree-based land use intensification). This is because the existing trends of forest resources developments are either too small-scale or too ineffective. In order to accelerate a forest transition in Ghana, policy and management options should target measures that reduce current degradation of natural forests, increase the area and productivity of commercial forest plantations, promote sustainable forest management, and support and encourage forest conservation and integration of trees into farming systems.

    Conservation genetics of the frankincense tree
    Bekele, A.A. - \ 2016
    Wageningen University. Promotor(en): Frans Bongers, co-promotor(en): Rene Smulders; K. Tesfaye Geletu. - Wageningen : Wageningen University - ISBN 9789462576865 - 158
    boswellia - genomes - dna sequencing - tropical forests - genetic diversity - genetic variation - genetics - forest management - plant breeding - boswellia - genomen - dna-sequencing - tropische bossen - genetische diversiteit - genetische variatie - genetica - bosbedrijfsvoering - plantenveredeling

    Boswellia papyrifera is an important tree species of the extensive Combretum-Terminalia dry tropical forests and woodlands in Africa. The species produces a frankincense which is internationally traded because of its value as ingredient in cosmetic, detergent, food flavor and perfumes productions, and because of its extensive use as incense during religious and cultural ceremonies in many parts of the world. The forests in which B. papyrifera grows are increasingly overexploited at the expense of the economic benefit and the wealth of ecological services they provide. Populations of B. papyrifera have declined in size and are increasingly fragmented. Regeneration has been blocked for the last 50 years in most areas and adult productive trees are dying. Projections showed a 90% loss of B. papyrifera trees in the coming 50 years and a 50% loss of frankincense production in 15 years time.

    This study addressed the conservation genetics of B. papyrifera. Forty six microsatellite (SSR) markers were developed for this species, and these genetic markers were applied to characterize the genetic diversity pattern of 12 B. papyrifera populations in Ethiopia. Next to this, also the generational change in genetic diversity and the within-population genetic structure (FSGS) of two cohort groups (adults and seedlings) were studied in two populations from Western Ethiopia. In these populations seedlings and saplings were found and natural regeneration still takes place, a discovery that is important for the conservation of the species.

    Despite the threats the populations are experiencing, ample genetic variation was present in the adult trees of the populations, including the most degraded populations. Low levels of population differentiation and isolation-by-distance patterns were detected. Populations could be grouped into four genetic clusters: the North eastern (NE), Western (W), North western (NW) and Northern (N) part of Ethiopia. The clusters corresponded to environmentally different conditions in terms of temperature, rainfall and soil conditions. We detected a low FSGS and found that individuals are significantly related up to a distance of 60-130 m.

    Conservation of the B. papyrifera populations is urgently needed. The regeneration bottlenecks in most existing populations are an urgent prevailing problem that needs to be solved to ensure the continuity of the genetic diversity, species survival and sustainable production of frankincense. Local communities living in and around the forests should be involved in the use and management of the forests. In situ conservation activities will promote gene flow among fragmented populations and scattered remnant trees, so that the existing level of genetic diversity may be preserved. Geographical distance among populations is the main factor to be considered in sampling for ex situ conservation. A minimum of four conservation sites for B. papyrifera is recommended, representing each of the genetic clusters. Based on the findings of FSGS analyses, seed collection for ex situ conservation and plantation programmes should come from trees at least 100 m, but preferably 150 m apart.

    Tropical forests in a changing world
    Zuidema, P.A. - \ 2015
    Wageningen : Wageningen University - ISBN 9789462573765 - 24
    tropical forests - forests - forest ecology - climatic change - forest management - tropische bossen - bossen - bosecologie - klimaatverandering - bosbedrijfsvoering
    Oogst in het Nederlandse bos : Analyse van niet-geoogste plots uit de Zesde Nederlandse Bosinventarisatie
    Clerkx, A.P.P.M. ; Schelhaas, M. ; Zwart, J. - \ 2015
    Alterra, Wageningen-UR (Alterra-rapport 2610) - 33
    forestry - forest inventories - forest management - forests - netherlands - bosbouw - bosinventarisaties - bosbedrijfsvoering - bossen - nederland
    Vanuit de overheid zijn al sinds de jaren 80 van de vorige eeuw acties genomen om de oogst in het
    Nederlandse bos te promoten, maar het niveau van de oogst is al enkele decennia min of meer
    constant. Uit de Zesde Nederlandse Bosinventarisatie is gebleken dat op ruim 40% van de punten niet
    is geoogst sinds de inventarisatie van het Meetnet Functievervulling. De eigenaren van deze punten
    zijn gevraagd naar de redenen waarom daar niet is geoogst en wanneer zij wel over zullen gaan op
    oogst. Met deze gegevens is een schatting gemaakt van de hoeveelheid hout die mogelijk meer zal
    kunnen worden geoogst
    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.

    Evaluating sustainability options in an agricultural frontier of the Amazon using multi-criteria analysis
    Verburg, R.W. ; Rodrigues Filho, S. ; Debortoli, N. ; Lindoso, D. ; Nesheim, I. ; Bursztyn, M. - \ 2014
    Land Use Policy 37 (2014). - ISSN 0264-8377 - p. 27 - 39.
    brazilian amazonia - forest management - deforestation - biodiversity - conservation - framework - policies - science
    Agricultural expansion and deforestation in the Brazilian Amazon are driven by a complex interaction between economic and demographic drivers and institutional constraints. Land use policies such as Conservation Units and the Forest Code law should conserve biodiversity and other environmental aspects while, on the other hand, increasing commodity prices of beef and soy, driven by world markets provokes economic growth and expansion of the agricultural area. We carried out an impact assessment in eleven municipalities within an agricultural frontier along the road BR-163 that runs in the Brazilian Amazon states of Mato-Grosso and Pará. The impact assessment, covered a period between 2008 and 2020, showed that the autonomous development in the study area results in a strong increase in the performance of economic indicators but a reduction in environmental and some social indicators. The studied conservation policies are able to reduce negative environmental impacts to some extent, while hardly affecting economic and social indicators. The multi-criteria analysis (MCA) showed a trade-off relation between the economic and environmental dimension in such a way that the effect was much stronger in the high commodity price scenario than in the low price scenario. The policy implications of the MCA results are discussed in light of the institutional capacity of the Brazilian States under study, to implement effective conservation policies.
    Functional ecology of tropical forest recovery
    Lohbeck, M.W.M. - \ 2014
    Wageningen University. Promotor(en): Frans Bongers; M. Martínez-Ramos, co-promotor(en): Lourens Poorter. - Wageningen : Wageningen University - ISBN 9789462571617 - 223
    bosecologie - ecologie - tropische bossen - bossen - plantensuccessie - biodiversiteit - bosbedrijfsvoering - forest ecology - ecology - tropical forests - forests - plant succession - biodiversity - forest management

    Electronic abstract of the thesis for the library for the acquisitions department of Wageningen UR library (published as a html file so hyperlinks may be included)

    In English, one or 2 pages.

    Functional ecology of tropical forest recovery

    Currently in the tropics, the area of secondary forest exceeds that of mature forest, and the importance of secondary forest will probably continue to increase in the future. Understanding secondary forests’ potential for maintaining biodiversity and critical ecosystem functions is thereby vital. The aim of this study was to mechanistically link tropical forest succession with the recovery of ecosystem functioning after agricultural field abandonment using a trait-based approach. Such an approach makes use of functional traits; components of an organism’s phenotype that are key to assess ecosystem responses to global change drivers, and are at the same time indicators of how organisms drive changes in ecosystem functioning. Trait-based approaches could therefore provide a mechanistic way to scale up from organisms to ecosystems and thereby contribute towards a more predictive biodiversity and ecosystem functioning science. For this study, I made use of secondary forest data from a wet forest region in Chiapas (main study site), that cover the first 3 decades of succession, complemented with data from a dry forest region in Oaxaca, that cover the first 6 decades of succession. Both are tropical regions in Mexico, characterized by high biodiversity levels and rapid forest loss for agricultural expansion.

    In this study I found that functional diversity (the range of different functional traits) increases rapidly and functional composition (the weighted average functional trait value) changes directionally with succession (chapter 2 and 3). These reflect changing habitat filters (changing environmental gradients that underlie succession), and also a gradual shift from habitat filtering towards an increasing effect of competitively driven limiting trait similarity (chapter 4 and 5). Such successional changes in community functional properties suggest strong changes in ecosystem functions, however in situ ecosystem function rates were primarily explained by the total amount of biomass present rather than by biodiversity or functional trait properties of secondary forests (chapter 6). Only the more controlled ex situ decomposition rates were additionally significantly influenced by functional diversity and functional composition. When evaluating the identity of species that drive most of the ecosystem functions I found that different functions were largely driven by the same (dominant) species, implying a limited effect of biodiversity for multifunctionality at a given moment in time. This suggests that biodiversity is mainly important for maintaining multifunctional ecosystems across temporal and spatial scales (chapter 7).

    Deforestation is a major threat to natural forests and biodiversity, and I recognize that secondary forests are generally a poor substitute of mature forest. Nevertheless, I show that unassisted recovery through natural succession can be rapid, and contribute considerably to maintenance of biodiversity, functional strategies and ecosystem functions. So while protecting the remaining tracts of mature forests is vital, secondary forests are key components of multifunctional human-modified landscapes where synergies between biodiversity, ecosystem functions and human wellbeing can be optimized.

    Entomofauna inventory in Speulder forest
    Jagers Op Akkerhuis, G.A.J.M. ; Dimmers, W.J. ; Moraal, L.G. - \ 2014
    biodiversity - forest management
    2002, inventory of entomofauna in an old beech forest reserve on sandy soil at Speuld, province of Gelderland using pitfalls, pyramidtraps and malaisetraps
    The role of spatial information in the preservation of the shrimp nursery function of mangroves: A spatially explicit bio-economic model for the assessment of land use trade-offs
    Zavalloni, M. ; Groeneveld, R.A. ; Zwieten, P.A.M. van - \ 2014
    Journal of Environmental Management 143 (2014). - ISSN 0301-4797 - p. 17 - 25.
    managing ecosystem services - brown shrimp - sustain biodiversity - distribution pattern - coastal fisheries - forest management - economic returns - mekong delta - conservation - habitats
    Conversion to aquaculture affects the provision of important ecosystem services provided by mangrove ecosystems, and this effect depends strongly on the location of the conversion. We introduce in a bioeconomic mathematical programming model relevant spatial elements that affect the provision of the nursery habitat service of mangroves: (1) direct or indirect connection of mangroves to watercourses; (2) the spatial allocation of aquaculture ponds; and (3) the presence of non-linear relations between mangrove extent and juvenile recruitment to wild shrimp populations. By tracing out the production possibilities frontier of wild and cultivated shrimp, the model assesses the role of spatial information in the trade-off between aquaculture and the nursery habitat function using spatial elements relevant to our model of a mangrove area in Ca Mau Province, Viet Nam. Results show that where mangrove forests have to coexist with shrimp aquaculture ponds, the inclusion of specific spatial information on ecosystem functions in considerations of land allocation can achieve aquaculture benefits while largely preserving the economic benefits generated by the nursery habitat function. However, if spatial criteria are ignored, ill-advised land allocation decisions can easily lead to a collapse of the mangrove’s nursery function.
    Forest governance dynamics in Ethiopia : histories, arrangements, and practices
    Ayana, A.N. - \ 2014
    Wageningen University. Promotor(en): Bas Arts, co-promotor(en): Freerk Wiersum; A. Agrawal. - Wageningen : Wageningen University - ISBN 9789462570139 - 140
    bosbeleid - governance - bosdynamiek - geschiedenis - bosbedrijfsvoering - ethiopië - forest policy - governance - forest dynamics - history - forest management - ethiopia

    This thesis deals with forest governance in Ethiopia. Forest governance is an important subject to study both as an emerging field of scientific analysis and as a means to understand and tackle the practical challenges facing forest resource management and conservation. Forests are one of the vital renewable resources that support the livelihoods of millions of people in Ethiopia. Despite their significance, Ethiopia is fast losing its forest resources due to intense and unsustainable human uses coupled with institutional and policy deficiencies. This study aims to provide a better understanding of how forest governance has developed and been practiced in Ethiopia over the past five decades. It analyses forest governance dynamics over several years, at multiple political-administrative levels, from multi-actor perspectives, and the effect of the new governance system on local forest management practices. The thesis thereby contributes to the scientific analysis of governance from the perspective of a country for which there is a dearth of relevant research. It also comprehensively explains the establishment process and performance of forest governance reforms in Ethiopia. It is hoped that the results will assist people who design and implement forest and related natural resource policies.

    Fixing rural development cooperation? Not in situations involving blurring and fluidity
    Umans, L.H.M. ; Arce, A.M.G. - \ 2014
    Journal of Rural Studies 34 (2014). - ISSN 0743-0167 - p. 337 - 344.
    forest management
    Rural development cooperation often took the form of a fix: external actors fixed a problem by introducing a fixed solution. Since the late 1980s the increased recognition of diversity, embeddedness and complexity, resulted in a shift from a ‘best fix’ approach to a ‘best fit’ approach. Context specificity replaced one-size-fits-all models. Yet in the specific case of forestry cooperation with the Yuracaré in Bolivia, it is argued no fit-in-context was found because of blurred phenomena and a confusing development situation. Moreover, the Yuracaré together with a Bolivian NGO blurred boundaries, reworked categorical divisions, and intermingled knowledge. This case sensitizes policy and rural development actors more generally to a novel conceptual and ontological perspective on such unstable situations, which revolve around fluidity. Fluid situations call for a rural development approach labelled ‘go-with-the-flow’. Recognizing the heterogeneity of development situations implies that any singular approach to realise rural development is at best partial
    Traditional ecological knowledge in Europe: status quo and insights for the environmental policy agenda
    Hernández-Morcillo, M. ; Hoberg, J. ; Oteros Rozas, E. ; Plieninger, T. ; Gómez-Baggethun, E. ; Reyes-García, V. - \ 2014
    Environment: Science and Policy for Sustainable Development 56 (2014)1. - ISSN 0013-9157 - p. 3 - 17.
    ecosystem management - cultural landscape - forest management - conservation - biodiversity - dynamics - science - sweden - spain - pastoralists
    From landless to forestless? : settlers, livelihoods and forest dynamics in the Brazilian Amazon
    Homero Diniz, F. - \ 2013
    Wageningen University. Promotor(en): Bas Arts, co-promotor(en): Kasper Kok; Marjanke Hoogstra-Klein. - [S.l.] : s.n. - ISBN 9789461735836 - 184
    ontbossing - landloosheid - bossen - bosdynamiek - bosecologie - middelen van bestaan - strategieën voor levensonderhoud - bosbedrijfsvoering - brazilië - deforestation - landlessness - forests - forest dynamics - forest ecology - livelihoods - livelihood strategies - forest management - brazil

    Keywords: deforestation; remote sensing; mental models; stakeholders’ perceptions; agrarian reform

    Over the last decades, hundreds of thousands of families have settled in projects in the Brazilian Amazon within the Agrarian Reform Program (ARP) framework, the rationale being to enable settlers to earn their living by small-scale farming and produce an agricultural surplus for sale. Further, the Brazilian Forestry Code requires settlers not to deforest more than 20% of forest on their properties, but in many projects settlers have deforested larger areas than this. However, specific questions about whether the settlers’ activities are, at the very least, providing their livelihoods, and about the effects of these choices on deforestation over time, have hardly been addressed. Located in five settlement projects in Eldorado do Carajás, southeast Pará State, this research investigated how settlers make their living; how their activities and practices affect forest cover changes; and how future prospects for both, i.e. people and forest, are envisioned. Within the framework of the sustainable livelihoods approach, the results indicated that settlers rely on three livelihood strategies (livestock-, diversified-, and off-farm-oriented), with dairy cattle as the main agricultural activity. These strategies are shaped by several factors, such as agrarian reform policies (e.g. credit) and settlers’ background. Forest dynamics analysis showed a clear recent increase in forest (2005–2010) at municipal level, suggesting that the first steps towards forest transition are taking place. However, settlers do not perceive secondary regrowth as ‘real’ forest, implying a high risk of future deforestation in these areas; but these areas can also be seen as having a high potential of remaining forested if technological innovations in agricultural activities and practices become available in the (near) future. The research findings also indicated the necessity to analyse livelihoods and forest cover changes as dynamic processes. It was not possible to determine one-to-one relationships and general patterns of effects of livelihood trajectories on forest dynamics due to the complexities involved, although analysis of individual household- and property-level cases offered insights into factors driving both. Fuzzy cognitive mapping was used to capture current settlers’ perceptions about their realities. The results indicated that settlers have similar perceptions of the factors that affect their livelihood security and environmental sustainability, independent of livelihood strategy adopted. However, differences were found in the relationships among factors and the weight attributed to each relationship, creating fundamentally different system dynamics for each livelihood strategy. Consequently, strong trade-offs exist between livelihood security and environmental sustainability independent of livelihood strategy and in (nearly) all future scenario analyses. The research produced five key messages: 1) small farmers within the studied ARP projects are less poor than often assumed; they achieve livelihood security through on- and off-farm income; 2) there is a strong trade-off between livelihood security and environmental sustainability; hence primary forest deforestation continues, although the first signs of secondary forest transitions have been observed; 3) the settlers’ contribution to deforestation is less than often assumed because they contribute to emerging forest transitions and because local deforestation peaked before the projects; 4) policies strongly affect the settlers’ realities; hence their views are crucial for effective policymaking, including both the Forestry Code and agrarian reform policies; and 5) livelihood trajectories and forest dynamics models are more appropriate to capture the realities of the human–environment systems in the Brazilian Amazon than livelihoods as snapshots and unidirectional deforestation models.

    Amerikaanse vogelkers
    Nyssen, B. ; Ouden, J. den; Verheyen, K. - \ 2013
    Zeist : KNNV - ISBN 9789050114523 - 160
    prunus serotina - bosecologie - geïntroduceerde soorten - invasieve soorten - bosbedrijfsvoering - nederland - forest ecology - introduced species - invasive species - forest management - netherlands
    Hij is de schrik van veel bosbeheerders: de Amerikaanse vogelkers. Maar het verhaal achter de boom is verrassend. Want zijn positieve eigenschappen wegen wellicht op tegen de nadelen. Dit boek belicht alle kanten en laat zien hoe we deze boom een plek kunnen geven in het Europese bosecosysteem. In dit boek wordt een nieuw perspectief geschetst op de Amerikaanse vogelkers. Zij blijkt in haar oorsprongsgebied een waardevolle boomsoort, en in onze bossen heeft vogelkers uiteindelijk ook gunstige effecten op het bosecosysteem. Bovendien worden lang niet al onze bossen massaal gekoloniseerd. De auteurs pleiten voor een genuanceerdere kijk op de vogelkers, waarbij handvatten worden gegeven voor een gedifferentieerd beheer. Het boek behandelt de introductie en bestrijding en de huidige problematiek rondom deze exoot. Ook haar invloed op bossuccessie, biodiversiteit, houtteelt en beheerstrategieën komen aan de orde. Dit boek laat zien hoe we deze exoot een plek kunnen geven in het Europese bosecosysteem, en tegelijk de bestrijdingskosten kunnen verminderen. Actuele kennis zorgvuldig en toegankelijk bijeengebracht voor specialisten in boomteelt, bosbeheerders, beleidsmakers en ecologen.
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