Finished projects

Acidification and eutrophication of forests on sandy soil: effects of forest type and deposition load

Picture forest conversionReports on the environment and nature in Flanders indicate the serious degree of soil acidification and -eutrophication of Flemish forests on sandy soils. Especially coniferous forests are threatened. Forest conversion of these homogenous coniferous plantations are often seen as one of the most urgent measures that need to be studied and implemented in order to protect soil fertility and vitality of forests on sandy soils. Increasing the share of broadleaved tree species is expected to have a fourfold effect: less captation of pollutants, higher consumption of nitrogen, better circulation of nutrients and in case of exploitation higher export of nitrogen. Following preliminary studies of De Schrijver et al. (2000), Van Hoydonck (1999) and Janssen (2001), this research project gained better insight in the possibility of forest conversion as effect-oriented measure against soil acidification and eutrophication of forests and forest edges. Furthermore, this study will give recommendations for the practical implementation of forest conversion into forestry practice.

Contact person: dr. ir. An De Schrijver (An.DeSchrijver@UGent.be)
Financier: Ghent University
Supervisor: Prof. dr. ir. K. Verheyen
Period: 2001-2007

Assessment of the effects of tree species diversity on FORest BIOdiversity and ecosystem functioning (FORBIO)

The FORBIO project resulted in (1) a review that synthesized and disseminated the existing knowledge about the benefits and drawbacks of mixed stands vs. monocultures with respect to the three components of sustainability, i.e., ecology, sociology and economics, (2) the establishment of a highly innovative, large-scaled forest biodiversity experiment for evaluating the impact of increasing tree diversity on ecosystem functioning. This experimental platform provides a highly innovative research facility for national and international scientists from a wide range of disciplines, with the purpose of deepening the understanding of the mechanisms behind diversity-ecosystem functioning relationships in forests. (3) an active network (a 'community of practice') for forest biodiversity research and management in Belgium, by providing areas of communication (meetings, conferences, discussion groups) between the whole community concerned with forest ecology, biodiversity and management. For more info, see: treediv|Belgium and TreeDivNet.

Contact person: Prof. dr. ir. K. Verheyen (Kris.Verheyen@UGent.be)
Financier: Belspo
Period: 2008-2010

Biomonitoring of air quality by using leaf characteristics of trees

Picture research TatianaThis research focuses on the potential of bio-monitoring of air quality with trees. Biological monitoring (or bio-monitoring), defined here as the measurement of the response of living organisms to changes in their environment (air quality), gives the possibility to take interactions between air pollutants and meteorological effects into account. The main objective of this research is to improve the bio-monitoring, by (i) investigating the correlation between the adaptation of leaf characteristics and air quality, (ii) evaluating the effect of genetic variability on the response, due to air pollution, of trees and (iii) determining the influence of duration of exposition to air pollutants on the response of trees. During the last year, the optimal bio-monitoring will be applied in a case study.

You can download this PhD thesis.

Researcher: dr. ir. Tatiana Wuytack
Contact person: Prof. dr. ir. Kris Verheyen (Kris.Verheyen@UGent.be)
Financier: Institute for the Promotion of Innovation by Science and Technology in Flanders (IWT)
Supervisors: Prof. dr. ir. R. Samson (UA), Prof. dr. ir. K. Verheyen
Period: 2009-2012

Can microbial community structure and selective nitrogen uptake explain differences in forest nitrogen dynamics

Nitrogen leaching below coniferous stands is more enhanced than in adjacent deciduous stands than can be explained by higher N inputs alone. In a previous study gross N transformation pathways were quantified in undisturbed well-drained sandy soils of neighbouring deciduous (pedunculate oak) and coniferous (Scots pine) forest stands located in a region with high N deposition (north Belgium). In situ inorganic N-15 labelling of the mineral topsoil (0-10 cm) combined with numerical data analysis demonstrated that all gross N transformations differed significantly between the two forest soils. The different N dynamics in these contrasting forest soils helped to explain the observed higher nitrate leaching under the coniferous stand compared to the deciduous stand. The present research aims to relate these different N dynamics in contrasting forest types to the structure of the active soil microbial community and to preferential uptake of inorganic and organic N forms by tree roots and micro-organisms. Therefore, in situ stable C and N isotope application to the mineral topsoil will be combined with advanced compound-specific analytical methods for stable isotopes. We will measure amino sugars and phospholipid fatty acids (PLFAs) in soils and amino acids in soils and plant roots. The research hypotheses are that (1) a functional link exists between gross N transformation rates, forest type, and the active microbial community structure, and (2) adult Scots pine trees under field conditions more preferentially take up ammonium than nitrate compared to pedunculate oak trees, while both tree species take up amino acids.

Researcher: dr. ir. Jeroen Staelens
Contact person: Prof. dr. ir. Kris Verheyen (Kris.Verheyen@UGent.be)
Financier: Research Foundation - Flanders (FWO)
Supervisors: Prof. dr. ir. K. Verheyen, Prof. dr. ir. P. Boeckx
Period: 2009-2012

Changes in bioavailability of phosphorus following afforestation of agricultural land

Picture research anAfforestation of agricultural land is of current interest in Flanders (North Belgium) and Europe. Forests deliver a varied gamma of ecosystem services such as climate and water regulation, erosion control, wood production, biodiversity protection and hunting possibilities.Fertilization of agricultural land has caused an accumulation of nutrients in the top soil layer, of which phosphorus (P) is particularly persistent. P concentrations are still elevated hundreds to thousands years after abandonment of agricultural practices. This persistently elevated bioavailable P is a paradox for the ecosystem fulfillment of new forests on agricultural land: a higher P bioavailability can on the one hand stimulate stand productivity and tree growth, but on the other hand limit the development of typical forest plant communities and other associated organisms. In soils, P may exist in many different forms which can be divided in three major pools: the solution P pool, the active P pool and the fixed P pool. The main objective of this research proposal is to study the tree-species dependent long-term changes in P fractions after afforesting agricultural land.

Contact person: dr. ir. An De Schrijver (An.DeSchrijver@UGent.be)
Financier: Ghent University - Research Foundation - Flanders (FWO)
Supervisor: Prof. dr. ir. K. Verheyen, Prof. dr. ir. S. De Neve
Period: 2008-2011

Comparison of ecosystem functioning and biogeochemical cycles in temperate forests in southern Chile and Flanders (1999 – 2002)

The pristine rain forests of southern Chile are one of the most unique forest ecosystems in the world. At present these forest are in danger by human activities, such as agricultural intensification and conversion to plantations. Increase of agricultural activities in the Central Valley of southern Chile could result in elevated N losses into the atmosphere, and increased N deposition on natural ecosystems. The aim of this project is to assess the current N deposition, to model future N deposition, to assess N and P biogeochemistry, and to contribute to a sustainable forest and agricultural management. This project is a joint project between the Ghent University, the Catholic University of Leuven (Flanders) and the Universidad Austral de Chile. The Flemish part is funded by the Ministry of the Flemish Community, Science, Innovation and Media Department.

Researcher: dr. ir. An De Schrijver
Contact person: Prof. dr. ir. Kris Verheyen (Kris.Verheyen@UGent.be)
Foreign partners: dr. Roberto Godoy and dr. Carlos Oyarzun, Universidad Austral de Chile, Valdivia, Chile.
Belgian partners: Prof. dr. ir. O. Van Cleemput, Prof. dr. ir. P. Boeckx, Prof. dr. ir. N. Verhoest
Financier: Ghent University. Bilateral Scientific and Technological Cooperation between Flanders and Chile.
Period: 1999-2002

Connectivity of the Natura 2000 network across the Belgian-Dutch borders in the Meuse basin

The overall objective of the project is the restoration of a mosaic of threatened pastoral habitats and species habitats within the basin of the Meuse River and its tributaries between Andenne and Maastricht. To achieve their common goals and ensure the coherence of the restored habitats network, partners from Wallonia (Natagora, DNF), Flanders (Natuurpunt, ANB, De Scheepvaart, Ghent University) and from the Netherlands (Natuurmonumenten) have chosen to combine their efforts through the presentation of a single LIFE project. Targeted habitats are mostly related to former pastoral systems: semi-natural dry grasslands on calcareous substrates (6210*, often in mosaic with rupicolous grasslands 6110*) and their transition forms to hay meadows (6510) or acidophilic grasslands (6230*), or are derived from mining or industrial activity (calaminarian grasslands, 6130). In the project area, these highly rich-species habitats have become extremely fragmented, and are undergoing progressive qualitative and quantitative regression.The project proposal also targets 4 species of bat. The calcareous character of the bedrock is indeed responsible for the presence of numerous caves and cavities, which are used by bats during the winter months. Although knowledge about their population’s status is still incomplete, we know that the Walloon part of the perimeter still shelter reproductive populations of four highly threatened species : Rhinolophus ferrumequinum, R. hipposideros, Myotis emarginatus, M. myotis. These species are strongly dependent on grasslands quality and structural diversity. The lack of connections between foraging habitats and roosts seems to be a key factor for their survival. Forest and Nature lab is responsible for the study of soil characteristics, in order to quantify which measures should be undertaken for restoration of the named semi-natural grassland types.

Contact person: dr. ir. An De Schrijver (An.Deschrijver@UGent.be), ir. Pieter Vangansbeke ()
Financier: Life+ (EU)
Period: 2015-2020

Decision support for harvesting methods of hardwood with large diameter in Flanders

Picture Aelmoeseneieforest exploitatie 2The increasing use of heavyweight machinery for wood harvests has a big impact on the soil. Former research showed that soils of Flemish forest are already seriously compacted. This demonstrates that the use of harvesting techniques with smaller impact on the soil is recommended. However, the implementation of those techniques in deciduous forests is not as straightforward as one would think, especially not for trees with large measurements, on slopes or on fragile soils. And supposedly these methods are more time consuming and require more physical labour. Therefore the financial impact should not be neglected.

The aim of this research is to define which methods are adequate for different circumstances. To do this, harvests are monitored in detail and terrain discussions are held between operators and forest managers. The focus is put on deciduous forests of large diameter and the typical given equipment, situation and possibilities of the Flemish harvesting industry. Every method is evaluated on financial, ecological and technical level.

 

Researcher: ir. Darline Velghe
Contact person: Prof. dr. ir. Kris Verheyen (Kris.Verheyen@UGent.be)
Financier: ANB, Agency of Nature and Forest Belgium
Supervisor: Prof. dr. ir. K. Verheyen
Period: 2009-2010

 

Defining guidelines for climate adaptation in the management of nature reserves in Flanders

soil erosionClimate change will affect ecosystems worldwide. How can nature and forest managers in Flanders adapt their management to be more resilient to climate change? A literature review will be combined with input from three workshops with terrain managers and experts.

Contact person: dr. ir. Andreas Demey (Andreas.Demey@UGent.be), dr. ir.  De Frenne (Pieter.DeFrenne@UGent.be)
Financier: ANB
Period: 2014-2015

 


DYLCAFO: DYnamic Life Cycle Assessment on FOrestry

Picture research ThomasTo make sure forestry is conducted in a sustainable manner, it is of crucial importance to assess the (potential) impact of it on the forest ecosystem and the environment in total. In this research, we’re going to quantify the impact of this activity and the further industrial processing of the wood on the environment over its complete life cycle chain, starting from photosynthesis and leading up to consumer usage of the wood product. In other words, we’ll perform a Life Cycle Assessment (LCA). However a forest is a living ecosystem. As a consequence, it will respond dynamically to any forestry activity and the effect(s) can have a long lasting duration. To assess the impact of e.g. wood harvest on a forest, we’ll thus need to take into account the (possible) future dynamic responses of a forest ecosystem to this activity. By using existing model(s), these responses will be simulated. The final goal is the conduction of a dynamic LCA on forestry (DYLCAFO) on a case study, a 1000 ha pine dominated forest in North-EastBelgium, by integration of a forest growth model into the LCA. Hopefully, this methodology can then be used in the future for other case studies.

You can download this PhD Thesis.

 

Researcher: ir. Thomas Schaubroeck
Contact person: Prof. dr. ir. Kris Verheyen (Kris.Verheyen@UGent.be)
Financier: Research Foundation Flanders (FWO)
Supervisors: Prof. dr. ir. J. Dewulf, Prof. dr. ir. K. Verheyen, Prof. dr. ir. B. Muys (KULeuven)
Period: 2010-2013

 

Ecohydrological monitoring in managed and unmanaged forest ecosystems in southern Chile (2006-2007)

 

Ecohydrology involves the study of both hydrology and ecology, and their interactions, and focuses on the links between plants and the abiotic environment which is driven by the hydrological cycle. In this project we investigate the impact of forest management on the ecohydrology of secondary forest ecosystems in southern Chile.

Researcher: dr. ir. Jeroen Staelens (contact: Prof. dr. ir. Kris Verheyen, Kris.Verheyen@UGent.be)
Foreign partners: dr. Roberto Godoy and dr. Carlos Oyarzun, Universidad Austral de Chile, Valdivia, Chile.
Belgian partners: Prof. dr. ir. O. Van Cleemput, Prof. dr. ir. P. Boeckx, Prof. dr. ir. N. Verhoest
Financier: Ghent University. Bilateral Scientific and Technological Cooperation between Flanders and Chile.
Period: 2006-2008

 

Ecosystem development and pollutant cycling on buffer dikes constructed with dredged material

 

This research is part of a multidisciplinary project exploring the possibilities of buffer dikes constructed with dredged material in the harbor of Antwerp. The advantages of such dikes are that a) a buffer is created between incompatible land uses (e.g. between industrial and residential area); b) a solution is created to the problem of shortage of disposal sites for dredged material; c) ecosystems are developed in or near the industrial harbor zones. Former research indicated that wind, soil moisture and salt content might be determining factors for tree growth. In 2000 an experimental dike was constructed in the Antwerp harbor area. The evolution of the salt and water content of the brackish material will be examined. The relation between these parameters and tree growth will be investigated and recommendations for planning and construction of buffer dikes will be made. The second topic of the research is the soil pollution. The dikes can only be constructed on the condition that they are ecotoxicologically safe. The uptake of pollutants that are specific for these sites is assessed and the influence of tree species on the soil pollution and uptake will be investigated.

You can download this PhD Thesis.

Researcher: dr. ir. Jan Mertens (contact: Prof. dr. ir. Kris Verheyen, Kris.Verheyen@UGent.be)
Financier: Antwerp Port Authority
Supervisor: Prof. dr. ir. K. Verheyen
Period: 2000-2006

Early tree diversity effects on tree growth, litter decomposition and herbivory

The impact of local neighbourhood composition and diversity on the growth (diameter, height), crown damage (e.g., defoliation) and crown arthropod community of target trees is investigated at the Zedelgem and Gedinne FORBIO sites (see treediv|Belgium and TreeDivNet). In-situ litter bags are used to study the decomposition rates of leaf litter mixtures.

 

You can download this PhD Thesis.

Contact person: prof. dr. ir. Kris Verheyen
Financier: European Commission – Erasmus Mundus
Period: 2011-2014


Effects of climate change on Acer regeneration from seeds

 

Picture research MercedesClimate warming is unequivocal and evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising of the global average sea level. An increase of the global mean air temperature of between 2.0 and 6.3ºC is expected by 2100. For the high latitudes, the current generation of models indicates that precipitation will generally increase as a consequence of a general intensification of the global hydrological cycle. Taking into account the magnitude of the changes in climatic parameters, it is evident that these modifications will have an important influence on plant fitness in general, and regeneration in particular. Some studies are conducted on the possible consequences of climate change on seed production, dormancy breaking, germination, population level consequences, etc. However, there is still an important lack of knowledge mainly concerning empirical studies about phenological phases of different species facing climate change. The main purpose of this project is to analyze the impact of climate change scenarios on the regeneration of forest trees from seeds in temperate forest communities in Europe. For this research we will work with seeds with different provenance. The seeds will be analyzed to detect the existence of ecotypes, genotypic or phenotypic differences related with the provenance. The impact of different climatic scenarios on the regeneration from seeds will be analyzed using growth chambers and open top chambers; this last method will also be combined with competition treatments. The goal of this study is to obtain valuable information for the development of recommendations for temperate European forest conservation and management in the face of climate change.

You can download this PhD Thesis.

Contact person: Maria Mercedes Caron (mechicaron@gmail.com)
Financier: European Commission – Erasmus Mundus
Supervisor: Prof. dr. ir. K. Verheyen
Period: 2011-2014

 

Effect of fire damage on regeneration and N loss from Araucaria araucana forests in southern Chile (2004 – 2005)

 

Chile’s forests are of great ecological value on a global scale, because of the high number of endemic species and biodiversity. In this bilateral project between Flanders and Chile we investigate the effect of a wild fire in an Araucaria araucana forest in Tolhuaco National park (southern Chile) on the regeneration of the vegetation and associated C loss and leaching losses of N species.

Researcher: dr. ir. Jeroen Staelens (contact: Prof. dr. ir. Kris Verheyen, Kris.Verheyen@UGent.be)
Foreign partners: dr. Roberto Godoy and dr. Carlos Oyarzun, Universidad Austral de Chile, Valdivia, Chile.
Belgian partners: Prof. dr. ir. O. Van Cleemput, Prof. dr. ir. P. Boeckx, Prof. dr. ir. N. Verhoest
Financier: Ghent University. Bilateral Scientific and Technological Cooperation between Flanders and Chile.
Period: 2002-2004

 

Effects of tree species induced soil acidification on litter and herb layer dynamics along a natural gradient of soil buffering capacity

 

Picture research GorikA large number of recent European studies report a significant forest soil acidification over the past 50 years. Soil acidification is a major cause of loss of soil buffering capacity and biodiversity. Soil acidification can be caused by several processes, of which atmospheric pollution is been considered to be very important. However, also tree species choice can be an important driver. The overall objective of this study is therefore to evaluate the effect of tree species induced soil acidification on litter and herb layer dynamics along a natural gradient of soil buffering capacity. Our study consists of three major parts. In a first observational part, the magnitude and velocity of the effect of soil acidification on soil properties, litter layer, earthworm community and herbal biodiversity will be quantified. Secondly, we aim to define threshold values for soil acidity of some forest herbs by means of a controlled pot experiment. Thirdly, we will test by means of a field experiment whether forest soils can recover from soil acidification.

You can download this PhD Thesis.

Contact person: Prof. dr. ir. K. Verheyen
Financier: Institute for the Promotion of Innovation by Science and Technology in Flanders (IWT)
Period: 2008-2012

 

Effects of tree species’ litter and root decomposition products on the mobility of Cd and Zn in sandy soils

 

Picture Lotte ResearchLitter decomposition and fine root turnover play an important role in the direct cycling of metals between plants and soil, and thus in the mobilization process of the metals. Hence, the goal of this project is to quantify the effects of decomposition processes of leaf litter and roots under 6 different tree species on the mobility of Cd and Zn, after 10 years of tree growth on former agricultural, sandy soil. The project focuses on modifications in pH and percent base saturation and the different OC fractions that will be originated during those decomposition processes.

Contact person: ir. Lotte Van Nevel (Lotte.VanNevel@Ugent.be)
Financier: Research Foundation - Flanders (FWO)
Supervisors: Prof. dr. ir. K. Verheyen, Prof. dr. ir. F. Tack, Prof. dr. ir. S. De Neve
Period: 2008-2012

 


Environmental, social and economic feasibility of forest conversion

 

Forest conversionForest degradation due to external input of atmospheric pollutants is a problem that is internationally recognized. The limited objectives for the reduction of emissions aren’t even approximately reached and ecologically relevant changes by source-oriented measures are not to be expected before some decades. The depositions of atmospheric pollutants into forests cause a cascade of ecological degradation: soil acidification, nitrate leaching, losses of base cations, degradation of the forest floor, decreased vitality of trees, collapse of biodiversity, especially into homogenous coniferous stands. Conifer stands (i) have a higher captation potential for air pollutants than deciduous trees (higher LAI, evergreen) and thus a higher input into the forest, (i) they consume more ammonium and less nitrate than deciduous species with an acidifying effect and a stimulus for nitrate leaching and (iii) they have a poorer litter quality and therefore slow down nutrient cycling, thus reinforcing nutritional imbalances caused by exogenous inputs. Moreover, the Belgian policy maker is currently faced with the need to implement different international protocols on sustainable development. At present, both the Flemish and the Walloon authorities have worked out / are working out incentives that promote a conversion towards sustainable forestry. Nevertheless, the current silviculture is still dominated by monocultures, exotic species, even-aged stands, coniferous species, purely economic goals etc. This project focuses on a sustainable forest conversion as the main driving force in turning a situation of forests under environmental threat into forests with increasing potential to provide ecological, economic and social benefits to present and future generations. The proposal aims at supplying an efficient and effective mix of policy instruments for conversion towards a more sustainable forestry type (forest conversion). This conversion is in the first place seen as an effect-oriented measure to counteract forest degradation caused by the interaction of forest type and high atmospheric deposition of pollutants.

Contact person: Prof. dr. ir. Kris Verheyen (Kris.Verheyen@UGent.be)
Financier: Belspo
Supervisor: Prof. dr. ir. K. Verheyen
Period: 2006-2008

 

 

Evaluation of policy instruments for sustainable forest management and forest expansion in Flanders

 

The research aim is to analyze the support and effectiveness of (new) policy instruments for sustainable forest management and forest expansion.

The research is put into practice through thee case studies:
Case 1. Forest expansion: the analyses of the support (political, official and civil society level) for forest expansion, for adjustments of legislative instruments (tenure law, field code), for current instruments (purchase policy, pre-emption, grants, compensation, long lease) and for new instruments (new rural estates, fiscal advantages of existing estates, forest fund, expert support, farmers for nature and red for green).
Case 2. Forest group: analysis of the possibilities of the forest group to introduce sustainable forest management in private forests.
Case 3. Financial instruments and sustainable forest management: the analyses of the support (political, official, civil society and forest owners) and efficiency of auction, long lease, easements, tradable developments rights, etc for sustainable forest management.

You can download this PhD Thesis.

Researcher: dr. ir. Peter Van Gossum (contact: Prof. dr. ir. Kris Verheyen, Kris.Verheyen@UGent.be)
Financier: Ghent University, BOF
Supervisors: Prof. dr. ir. K. Verheyen, Prof. dr. B. Arts (Wageningen University), Prof. dr. ir. R. De Wulf
Period: 2006-2009

 

 

Forest edge effect on atmospheric deposition, nitrate leaching and soil acidification in forests on sandy soils

 

In Flanders, the effects of atmospheric nitrogen deposition are enhanced by the highly fragmentized structure of the Flemish forests. Many forests are so small or have such geometry that the contribution of the edge in the total forest area amounts to almost 60%. Forest edges act as hotspots for atmospheric deposition, as they are more efficient at trapping atmospheric particles and gasses than the forest interior, and show on average a 1.5 to 4-fold increase of deposition compared with the interior. This edge effect diminishes with increasing distance to the forest edge. The width of the edge zone and the deposition enhancement in the edge zone depend on the structure of this edge.
The project evaluates the possibility of forest edge conversion as an effect-oriented measure against nitrate leaching and soil acidification. It inquires into the impact of tree species, tree density and the occurrence of forest margin vegetation on the width of the edge zone and the enhancement of deposition, nitrate leaching and soil acidification in the edge zone. The experiments are carried out forests in the north of the Campine region and in the western part of Flanders, in the forest ‘Neigembos’ and in ‘De Neterselsche Heide’ (the Netherlands). Transects of 128 m are established in forest edges, exposed to the prevailing wind direction (SW). Along these transects, throughfall water, soil solution, soil samples and vegetation characteristics are collected in a period of one year. By means of a wind tunnel experiment, the influence of various edge structure characteristics on the turbulence development and the deposition pattern at the edge is evaluated. The results of the observational as well as the experimental component of this study will be used to model throughfall deposition using edge structure characteristics. The study will result in recommendations for the optimal design of the forest edge for its protection against further acidification and nitrate leaching.

You can download this PhD Thesis.

Researcher: dr. ir. Karen Wuyts (contact: Prof. dr. ir. Kris Verheyen, Kris.Verheyen@UGent.be)
Financier: Ghent University
Supervisor: Prof. dr. ir. K. Verheyen
Period: 2007-2010

 

Forest plant dynamics along a latitudinal gradient

You can download this PhD Thesis.

Researcher: dr. ir. Pieter De Frenne
Financier: FWO
Supervisor: Prof. dr. ir. K. Verheyen
Period: 2007-2011


Forest understories: integrating below- and aboveground biotic interactions

Reforestation of former agricultural land is one of the most common practices to increase forest cover in Europe. However, forests grown on restored lands show low frequencies of typical understory plant species compared with ancient forests that have not been reclaimed. These differences are usually ascribed to differential abiotic soil conditions, the low seed availability due to dispersal limitation, and the lack of a permanent seed bank. An alternative, complementary, yet less studied explanation, is that previous land uses determines the soil biota composition, and this, in turn, hampers the establishment of the forest understory community. The aim of the present project is to investigate how the belowground biotic interactions found in restored forests (on formerly arable lands and grasslands) affect the plant community's structure and dynamics. In particular, the following will be addressed: (i) how plant-soil feedbacks affect the establishment, growth, and fitness of the understory and seedling/sapling community; and (ii) how soil biotic interactions affect aboveground trophic groups involved in ecosystem functioning and the delivery of ecosystem services. The results of this research are relevant to the understanding of forest ecosystem functioning and will help to optimize restoration practices.

Contact person: dr. Eduardo de la Pena
Financier: Research Foundation - Flanders (FWO)
Supervisors: Prof. dr. D. Bonte, Prof. dr. ir. K. Verheyen
Period: 2010-2013

FunDivEUROPE: Functional significance of forest biodiversity in Europe

Picture research FunDivThe overall scientific goal of FunDivEUROPE is to quantify the effects of forest biodiversity on ecosystem functions and services in major European forest types. A major aim is to understand and quantify how tree species diversity can be used to foster the provision of ecosystem services such as timber production, carbon sequestration and freshwater provisioning. Additionally, the implications of tree species diversity for the vulnerability of ecosystem services under climate change will be assessed by integrating field and modelling data on the performance of pure versus mixed species stands under different climates. The policy relevant objective is to strengthen the science-policy interface by delivering timely, relevant and understandable information to policymakers and stakeholders about the relationship of forest biodiversity and ecosystem services within the framework of multifunctional forestry. In FunDivEUROPE there are seven work packages operating on four platforms – three research platforms and one devoted to knowledge transfer processes. The research platforms can be seen as entities from which novel or previously hidden information on the functional significance of forest diversity can be extracted with experimental, observational, statistical or simulation methods. There are two physical platforms: the Experimental Platform consisting of the existing and independently funded network of tree diversity experiments (TreeDivNet), and the Exploratory Platform, a new observational platform consisting of six clusters each comprising about fifty forest stands that form a diversity gradient under comparable management and environmental conditions. The digital Inventory Platform, a compilation of relevant information from national forest inventories and other observational networks (e.g. FutMon) as well as complementary information on environmental and management-related covariates complements the forest-related data base.

Contact person: Michael Scherer-Lorenzen (michael.scherer@biologie.uni-freiburg.de)
Partners: INRA, University Freiburg, University Leipzig, UGent, METLA, ULEI, et al.
Financer: European Union Seventh Framework Programme (FP7/2007-2013)
Period: 2010-2015
Subprojects in ForNaLab:
- Quantifying the overstorey-understorey diversity relationships in forests
(more info)

Impact of bioavailable phosphorus on plant and soil microbial community interactions in grassland under restoration management

Heischraal graslandSpecies-rich semi-natural grasslands are often hotspots of biodiversity, but their extent decreases steadily in Western Europe. Several countries seek to restore semi-natural grasslands through conversion of agricultural land. Besides the potential unavailability of seeds of target plant species, two major bottlenecks may hamper restoration. Firstly, due to years of intensive fertilizer application, phosphorus (P) stocks have been built up to unprecedented levels and bioavailable P concentrations have shown to be negatively related with plant species diversity. Another bottleneck for ecosystem restoration on abandoned agricultural land is the general absence of a typical community of soil organisms, which has the potential to influence the composition of plant communities. Both drivers have been studied extensively, but to date their mutual interaction hardly received attention. Our aim is to find out if and how P bioavailability influences the soil microbial and plant community and their interactions in moderately dry endangered Nardus grasslands. An observational field study will be combined with an experimental mesocosm study in order to gaining novel insights in the processes that are at play in grasslands under restoration management at former agricultural land.

Contact person: dr. ir. An De Schrijver (An.DeSchrijver@UGent.be)
Financier: FWO
Supervisors: prof. dr. ir. Kris Verheyen, prof.dr.ir. Stefaan De Neve
Period: 2012-2015

 


Impact of a high density willow cover on the mobility and bioavailibility of trace elements in contaminated dredged sediment

 

The introduction of fast growing willow stands for energy purposes is a valuable land use option for the revaluation of contaminated substrates. It is possible to export heavy metals from the site through a repeated harvest of the willow wood. Mean time this generates additional income. These stands further initiate soil development and reduce erosion. However care should be taken to minimize the risk of spreading heavy metals into the environment through leaching and leaf litter fall. Our research focuses on the behaviour of heavy metals in the rhizosphere and root zone of willow growing on contaminated substrates. The mobility and availability of metals are determined using single and sequential extraction techniques. Changes in soil water characteristics in the rhizosphere are assessed using rhizoboxes and (micro)lysimeters. The spatial influence of willow roots on metal behaviour is determined in a rhizotron experiment.

You can download this PhD Thesis.

Researcher: dr. ir. Pieter Vervaeke (contact: Prof. dr. ir. Kris Verheyen, Kris.Verheyen@UGent.be)
Financier: Research Foundation - Flanders (FWO-Vlaanderen)
Supervisor: Prof. dr. ir. N. Lust
Period: 2000-2006

 

 


Impact of converting former pine plantations on the abundance of the sheep tick (Ixodes ricinus L.)

Picture research WesleyIxodes ricinus (L.), known as the sheep tick, is a tick of considerable significance as vector of both livestock and human diseases. In Europe, I. ricinus is the principal vector of Lyme disease, a potentially serious illness caused by the bacterium Borrelia burgdorferi, which is transmitted to humans during the blood meals of Ixodes ticks. Because risk of human exposure to the disease increases with increasing abundance of the vectors, it is important to better understand the biotic and abiotic factors regulating tick abundance. This insight is especially relevant in the Kempen region (Flanders, Belgium), where forest conversion (i.e. change in the dominant tree species from coniferous to deciduous) will take place over the next decennia. This research attempts to advance our understanding of the impact of forest conversion on tick abundance through influence on microclimate and food supply for small-sized mammals such as mice and voles, which serve as the main hosts for immature ticks. Relationships between vertical forest structure, food supply and tick abundance will be examined experimentally. Ticks will be collected by flag sampling of the vegetation, and abundance of small mammals will be determined using capture-recapture techniques. The knowledge gained in this study will enable us to determine the risk periods and zones for humans, and will help us to evaluate the implications of forest conversion on public health.

You can download this PhD thesis.

Researcher: dr. ir. Wesley Tack
Contact person: Prof. dr. ir. Kris Verheyen (Kris.Verheyen@UGent.be)
Financier: Institute for the Promotion of Innovation by Science and Technology in Flanders (IWT)
Supervisors: Prof. dr. ir. K. Verheyen, dr. M. Madder (Institute of Tropical Medicine)
Period: 2008-2011

 

Impact of hemiparasitic plants on grassland communities and biogeochemistry

 

Picture research AndreasHemiparasitic plants can influence the population dynamics and plant diversity of grasslands by (1) direct changes in vegetation structure [structural effects] and (2) indirectly by the redistribution of nutrients in the ecosystem [biogeochemical effects]. (1) Parasitic infection mostly causes total aboveground biomass to decrease. Furthermore, if dominant grasses are chosen as hosts, this may facilitate other species and increase species richness. (2) Parasitic plants act as a strong sink for water and nutrients from host plants, and therefore often produce fast-decomposing, high quality litter. This in turn may result in faster nutrient turnover and may possibly decrease species richness when higher nutrient availability favors competitive species.
This research project aims to reveal whether structural or biogeochemical effects of hemiparasites dominate vegetation changes in grassland ecosystems with contrasting nutrient availability. The two main hypotheses are (1) the structural effects will dominate in more nutrient-rich grasslands, and (2) the biogeochemical effects will dominate in more nutrient-poor grasslands. The two species studied are Rhinanthus angustifolius, growing in rather mesophile grasslands and Pedicularis sylvatica, growing in nutrient-poor heath grasslands. Experimental sites are all situated in nature reserves in Flanders.

You can download this PhD thesis.

Contact person: dr. ir. Andreas Demey (Andreas.Demey@UGent.be)
Financier: Institute for the Promotion of Innovation by Science and Technology in Flanders (IWT)
Supervisors: Prof. dr. ir. K. Verheyen, Prof. dr. ir. P. Boeckx, Prof. dr. ir. M. Hermy
Period: 2008-2012

 

Impact of tree species mixture on chemical forest floor characteristics

 

In a mixed hardwood forest (Quercus robur, Quercus rubra, Betula pendula, Betula pubescens) the spatial heterogeneity of the litter layer characteristics (biomass, C, Ntot, Ca, K, Mg, Na, Al) is quantified. From the knowledge of the tree positions, a spatially explicit model is build to predict leaf litter distribution, and composition and nutrient reserve of litter layer and topsoil for several mixtures. The research considers nutrient fluxes by troughfall and stemflow water, by leaf litter and by litter decomposition. The results should present the evolution of litter quantity and quality in a natural stand development in which the share of birch declines in favour of the share of the two oak species. Several methodological substudies are done to test used techniques as litterbags, throughfall collectors, etc.

Researcher: ir. Lieven Nachtergale (contact: Prof. dr. ir. Kris Verheyen, Kris.Verheyen@UGent.be)
Financier: Ghent University
Supervisor: Prof. dr. ir. N. Lust
Period: 1996-2001


Mechanistic modeling of aqueous nitrogen uptake by tree canopies

PIcture research KarenTree crowns are able to exchange gaseous nitrogen (N) compounds with the atmosphere and to take up N ions deposited as aerosol or gas and dissolved within the thin water film on leaves/needles and branches. The N taken up via the canopy is incorporated into the plant’s N pool and can be a substantial part of the overall N demand of the plant, dependent on atmospheric and pedospheric N concentrations, the plant’s N status and the species considered. The main objective of the study is to deliver an integrated mechanistic and input-extensive model for simulating the uptake of dissolved N by tree canopies on the leaf level, taking into account the phenological and physiological variation. The model will be developed based on available data from previous and ongoing studies, and on data from gap-filling pot experiments. In these experiments, we focus on the impact of plant-available N in the soil, rainfall characteristics, N concentration levels and tree species specific anatomical leaf characteristics (i.e., the characteristics of the stomata and the cuticle) on the uptake of N from thin water films on leaves/needles and twigs.

Researcher: dr. ir. Karen Wuyts
Contact person: Prof. dr. ir. Kris Verheyen (Kris.Verheyen@UGent.be)
Financier: Ghent University
Supervisors: Prof. dr. ir. R. Samson (UA), Prof. dr. ir. K. Verheyen
Period: 2009-2012

 

Model-based wood price predictions from public forest timber sales in Flanders

 

Contact person: dr. ir. Andreas Demey, dr. ir. Lander Baeten
Financier: Belspo
Period: 2013

 

Monitoring of the above and below ground C sequestration potential of Belgian forests and short rotation coppice on former agricultural land

 

Empircal results demonstrate that the canopy structure of a forest ecosystem causes systematic spatial patterns in throughfall water. The aim of the research is to quantify this spatial effect of a hardwood canopy on the amount and chemical composition of the hydrological input to the forest floor. Rainwater passing through the canopy of a forest ecosystem is influenced in two ways, quantitatively as well as qualitatively. Quantitatively, the amount of precipitation is divided into a fraction that reaches the forest floor as throughfall and stemflow water, and a fraction that is intercepted and evaporated during and after a rain event. Qualitatively, throughfall water is generally enriched in most chemical elements compared to bulk precipitation, as a result of (i) dry deposition of particles and gases, and (ii) canopy leaching, i.e. release of ions from plant tissues. The research is conducted in a mixed forest stand (forest of Aelmoeseneie, Gontrode) that is part of the UNEP network International co-operative program on the assessment and monitoring of air pollution effects on forests. Throughfall and stemflow have consequently been monitored since 1995, but to study the small-scale spatial variability of thoughfall water in detail, the present research focuses on one dominant beech tree. The spatial variability of throughfall amount at the plot scale is measured by a set of automatically registrating tipping buckets, and is predicted at the event scale by modelling the interception amount using meteorological data with high temporal resolution. The following step is to describe and predict the spatial variability of nutrients in throughfall water. The final model results will be of great relevance for evaluating the efficiency and accuracy of different sampling strategies for throughfall water.

Contact person: Prof. dr. ir. Kris Verheyen (Kris.Verheyen@UGent.be)
Financier: Belspo
Supervisor: Prof. dr. ir. N. Lust / K. Verheyen
Period: 2001-2005

 


Nitrogen retention in contrasting temperate forest ecosystems in a region of high nitrogen

 

Picture forest conversionAtmospheric nitrogen (N) input to terrestrial and aquatic ecosystems has strongly increased in the past century due to human activities. This has resulted in modified soil processes and varying ecosystem responses, including increased biomass growth and carbon sequestration, but also increased N losses by emission from soils and by leaching below the rooting zone. Nevertheless, considerable N retention in forests has been observed. Forest type and tree species potentially affect the degree of N retention because of differences in organic and mineral soil characteristics, microbial soil activity and N uptake by plant roots.
The objective of this study is to determine aboveground and belowground N retention in two contrasting forest stands in a region exposed to a chronically enhanced atmospheric N deposition. Studying the fate of added 15N isotopes and the rates of N transformation processes can explain the discrepancy between the input and loss of N that has been observed for these ecosystems.

Researcher: dr. ir. Jeroen Staelens (contact: Prof. dr. ir. Kris Verheyen, Kris.Verheyen@UGent.be)
Financier: Research Foundation - Flanders (FWO)
Supervisors: Prof. dr. ir. K. Verheyen, Prof. dr. ir. P. Boeckx
Period: 2006-2009

 


Phytoextraction of phosphorus: an attainable measure for nature development?

 

The European Habitats Directive urges the European member states to take measures for maintaining and restoring natural habitats. In Flanders and the Netherlands, the surface area of nature reserves is intended to be enlarged with 38.000 ha and 150.000 ha, respectively, what is mainly to be realized on former agricultural land. In order to restore species rich nature habitats on former agricultural land, it is crucial to decrease the availability of nutrients and a limitation for plant growth by at least one nutrient should be ensured. In Flanders and the Netherlands, the atmospheric deposition of the volatile nitrogen is far too high to be a limitating nutrient. Consequently, the focus now lies on the limitation of phosphorus (P) which is not volatile and more easy to regulate. The former fertilization of P in the agricultural context results in an immense P pool fixated to the soil and this is regarded as one of the main problems hindering the restoration.

The traditional method to deplete the soil P pool is by cropping and removing the biomass which very time-consuming (several hundred years) because of a depression in grass-biomass after a few years. Another, more recent method is top-soil removal, where the P-saturated soil is taken away with heavy machinery. This is a very expensive operation where also the soil buffering components and soil biota are exported. Recent research showed that these components and biota might be essential against soil acidification and in the recovery of the species rich habitat. In this study we will focus on another potential method, the phytoextraction of P, also P mining. This is the deprivation of soil P with a crop with high P-use efficiency and non-P fertilization. This method allows the gradual transition from agricultural land use towards nature management. We will use a complex grass mixture together with humic acids, mycorrhizae and clover to speed up the solubilization of phosphorus. As an additional treatment we will cultivate also white lupines (Lupinus albus) which can utilize fixated phosphorus very efficiently with cluster roots. The goal of this project is to propose a practical alternative for the current restoration methods.

Researcher: ir. Stephanie Schelfhout (Stephanie.Schelfhout@UGent.be)
Financier: University College Ghent
Supervisors: Prof. dr. ir. G. Haesaert (HoGent), prof. dr. ir. K. Verheyen, dr. ir. A. De Schrijver
Period: 2010-2012

 

Present and future population dynamics of black cherry (Prunus serotina Ehrh.) in forests in its introduced range deposition

Picture Research Margot AVPrunus serotina Ehrh., a tree species native to eastern North America, has been introduced into Europe for different reasons since the beginning of the 17th century. The species is considered an invasive species in Western Europe, and a lot of time and money have been invested in the control of the species. Only during the last decade, researchers have started to investigate the ecology of the species. In this thesis, we wanted to gain more insight into the population dynamics of P. serotina in forests in its introduced range.
We investigated (1) two key processes in the biology of the species, i.e., diameter growth and regeneration, (2) patterns of long-term spontaneous colonization of P. serotina in two contrasting forests in which the species had not been introduced intentionally, and (3) long-term scenarios of forest development with P. serotina using SORTIE-ND, a spatially explicit model of forest dynamics. The focus of the thesis lies on pine (Pinus sylvestris L.) forests on sandy soil because these are the forests in which P. serotina occurs most often in its introduced range. In addition, we also studied a mixed deciduous forest on sandy loam soil.

You can download this PhD thesis.

Contact person: dr. ir. Margot Vanhellemont (Margot.Vanhellemont@UGent.be)
Financier: Research Foundation - Flanders (FWO)
Supervisors: Prof. dr. ir. K. Verheyen, Prof. dr. M. Hermy (KULeuven)
Period: 2005-2009

 


Reading ancient woodlands in the Campine region of Antwerp (northern Belgium). An exercise in historical ecology

This interdisciplinary project examines a number of ancient woodlands (permanently existing since 1775) in the Campine region of the current Province of Antwerp. The Campine region is dominated by relatively poor sandy soils, and the landscape used to consist mainly of heathlands and small-scale arable fields. Forests were very limited in number and extent until the 19th century when the heathlands were transformed in pine forests in the context of the new mining activities in Wallonia and Limburg. Our research area consists of three rare examples of large ancient forest complexes, i.e., Zoerselbos (380 ha), Grotenhout (295 ha) and Peerdsbos (154 ha), and focuses on the period of the 'ancien régime' (13th -18th century).

The three forests are examined focusing on historical property relations and dynamics, land use, their botanical composition, past management activities and landscape features and this in relation to the heuristic potential (historical sources, historical ecological values and relicts in the landscape).

Our main goal is to compare and synthesize the variables of each research area. By doing so, useful inheritance can be studied in a comparative perspective with important consequences on both thematic and management fields.

Contact person: Kris Verheyen
Financier: Free University of Brussels, Province of Antwerp
Supervisors: Prof. dr. ir. K. Verheyen
Period: 2008-2012

 

 

Recovery potential of forest plant communities on phosphate enriched farmland

Picture research LanderAfter reforestation of agricultural land, the accumulated amount of phosphorus from former fertilization practice persists in the topsoil layer and vegetation for hundreds or thousands of years. Moreover, since this nutrient is regarded as a limiting recourse in forest ecosystems, its enhanced availability is expected to determine species richness and composition of the forest herb layer. Therefore, the aim of this study is to assess which plant species can establish and persist in these recent forests and which plant communities are to be expected on the long-term. The research focuses on both the plant and the community level and includes two contrasting forest types (mesotroof versus oligotroof). The influence of possible interacting factors such as light availability and soil acidity will be integrated in the study.

You can download this PhD Thesis.

Contact person: dr. ir. Lander Baeten (Lander.Baeten@UGent.be)
Financier: Institute for the Promotion of Innovation by Science and Technology in Flanders (IWT)
Supervisors: Prof. dr. ir. K. Verheyen, Prof. dr. M. Hermy (KULeuven)
Period: 2007-2010

 


Refinement of a canopy budget model by analysing nutrient transfer processes in tree canopies at different spatio-temporal scales

Picture research SandyBecause of their surface roughness, higher leaf area index and physiological leaf characteristics, forests receive a higher atmospheric input of gases and aerosols compared to open field circumstances. These increased deposition levels may have adverse effects on the structure and functioning of forest ecosystems. To quantify the total atmospheric deposition onto forests, a so-called canopy budget model that estimates dry deposition and ion exchange reactions within forest canopies, based on precipitation and throughfall measurements, is applied worldwide. Up to now, this model has only been validated twice with the results of an inferential method. In both studies the results of the two methods didn’t correspond sufficiently for one or more elements.

The aim of this project is to evaluate and adapt the several assumptions made in the canopy budget model for different tree species, phenological periods, atmospheric pollution levels and site conditions by working at different spatial levels. For one year dry deposition and canopy exchange processes will be studied at the leaf and branch level of an adult beech and young beech, birch and pine trees under different N-supply, rain intensity and atmospheric pollution level. At the same time, physiological leaf characteristics will be measured and linked to the observed processes. This results can be used to adapt the canopy budget model and extend the existing FORUG model, that simulates nutrient transfer using meteorological en atmospheric conditions. Using canopy architecture data, this FORUG model can be upscaled to the canopy level. Both models will be compared en validated at the stand level (a Level II observation plot in which water and ion fluxed in throughfall and stemflow have been measured since 1994) with an inferential method for measuring dry deposition.

You can download this PhD thesis.

Researcher: dr. ir. Sandy Adriaenssens
Contact person: Prof. dr. ir. Kris Verheyen (Kris.Verheyen@UGent.be)
Financier: Research Foundation - Flanders (FWO)
Supervisors: Prof. dr. ir. K. Verheyen, Prof. dr. ir. R. Samson (UA), Prof. dr. ir. P. Boeckx
Period: 2008-2011

 

Relations between growth dynamics, forest management and wood characacteristics of birch on sandy soils in Flanders

Picture Aelmoeseneieforest sfeerbeeldThere are not many birch stands in Flanders. The knowledge about the growth, management and wood quality of birch in our region is therefore limited. Due to a changed policy concerning pine plantations on sandy soils in Flanders, these forests are designated for forest reconversion towards mixed stands. Birch is said to be one of the tree species fit for this purpose. This research therefore focusses on determining the potential of birch on the sandy soils in Flanders. In several birch stands measurments will be done and trees will be harvested and this to determine their wood quality. Combining this knowledge with data concerning growth and limiting factors for growth and wood quality should lead to best management practices aiming at optimal growth and wood quality of birch in Flanders.

Contact person: Prof. dr. ir. Kris Verheyen (Kris.Verheyen@UGent.be)
Financier: Ghent University
Supervisor: Prof. dr. ir. Kris Verheyen, Prof. dr. ir. Joris Van Acker (Woodlab)
Period: 2008-2010

Research on the P bottleneck for restoration of:

- lowland meadows in Bos van Aa

- lowland meadows in Dorent/Pikhaken

- lowland meadows in the valley of the Marck

- different grassland types in the valley of the Moervaart

In the framework of the establishment of the Natura 2000 network, an EU-wide network of protected areas, ecosystems have to be restored on former agricultural land. However, restoration on agricultural land is hindered by both biotic and abiotic bottlenecks.  One of the most important bottlenecks for ecosystem restoration on former agricultural land is the large stock of nutrients, in particular nitrogen and phosphorus. Because of a surplus of animal manure in many Western European countries, agricultural soils were often intensively fertilised with slurry or farmyard manure during many decades. Within these different projects, we studied whether restoration of species-rich grasslands is possible on several parcels, most of them in agricultural use. We sampled and analysed soil on different chemical characteristics, especially different P fractions, and evaluated which management regime (mowing, soil removal or P-mining) is most appropriate for ecosystem restoration.

Contact person: Dr. ir. An De Schrijver (An.DeSchrijver@UGent.be)
Financier: Agency for Nature and Forest
Period: 2012-2015


Risk assessment of agricultural intensification on N deposition on pristine forests and plantations in southern Chile (2001-2004)

The pristine rain forests of southern Chile are one of the most unique forest ecosystems in the world. At present these forest are in danger by human activities, such as agricultural intensification and conversion to plantations. Increase of agricultural activities in the Central Valley of southern Chile could result in elevated N losses into the atmosphere, and increased N deposition on natural ecosystems. The aim of this project is to assess the current N deposition, to model future N deposition, to assess N and P biogeochemistry, and to contribute to a sustainable forest and agricultural management. This project is a joint project between the Ghent University, the Catholic University of Leuven (Flanders) and the Universidad Austral de Chile. The Flemish part is funded by the Ministry of the Flemish Community, Science, Innovation and Media Department.

Researcher: dr. ir. Jeroen Staelens (contact: Prof. dr. ir. Kris Verheyen, Kris.Verheyen@UGent.be)
Foreign partners: dr. Roberto Godoy and dr. Carlos Oyarzun, Universidad Austral de Chile, Valdivia, Chile.
Belgian partners: Prof. dr. ir. O. Van Cleemput, Prof. dr. ir. P. Boeckx, Prof. dr. ir. N. Verhoest
Financier: Ghent University. Bilateral Scientific and Technological Cooperation between Flanders and Chile.
Period: 2002-2004

 

Scenarios of topsoil removal and P mining for habitat restoration in Smeetshof

SmeetshofAreas for top soil removal were designated based on an eco-hydrological model. Although very useful, such models overlook phosphorus accumulation in the soil as a potential bottleneck for ecosystem restoration. In this project, we analyse soil samples in order to formulate optimized recommendations for top soil removal and phosphorus mining.

Contact person: dr. ir. An De Schrijver (An.DeSchrijver@UGent.be)
Financier: ANB
Period: 2014-2015


Seed ecology of common juniper (Juniperus communis)

Picture research RobertJuniper is a coniferous shrub which occurs mainly on vast heathlands and calcareous grasslands. It has the largest distribution range of all coniferous species, covering large parts of the Northern hemisphere. Nevertheless, the last decades, a decline of juniper populations was observed in North-western Europe and in the Mediterranean area. The loss and degradation of suitable habitats due to afforestation, urbanization, the abandonment of traditional management and the expansion of competitive species play a significant role in this decline. More importantly however, is the failing reproduction, caused by a dramatically low seed viability and the absence of appropriate microsites for germination. The poor regenerative status of common juniper is widely considered to be the greatest long-term threat for its conservation. Therefore, the main goal of this project is to find out the reasons for failing reproduction and the effect of management on recruitment.

You can download this PhD thesis.

Researcher: dr. ir. Robert Gruwez                                                                                                              Contact person: Prof. dr. ir. K. Verheyen ()
Financier: Ghent University
Supervisor: Prof. dr. ir. K. Verheyen
Period: 2010-2014

 

Seeing the trees for the wood: using 40 years of research in the forest Aelmoeseneie to answer current environmental questions

The Aelmoeseneie forest is part of the patrimony of Ghent University, is characterized by a long forest history and has been used for scientific research since the 1970s (see the history of the Aelmoeseneie forest). The aims of the project were to review the forest's history, make an overview of the research performed in the forest, synthesize the results of the different scientific studies into a book for laymen, and provide information on the multiple functions of the Aelmoeseneie forest via a website. The book and the website are aimed at the general public. They make the results of the scientific research in the forest Aelmoeseneie easily accessible to all people interested in forests and the related environmental issues. In the book, the results of the scientific studies are used to answer topical environmental questions regarding forests in Flanders, such as ‘Are forests able to mitigate air pollution and climate change?’, ‘How much wood does a forest produce?’, ‘How many plant and animal species can be found in a forest?’

Contact person: dr. ir. Margot Vanhellemont (Margot.Vanhellemont@UGent.be)
Financier: Ghent University
Supervisor: Prof. dr. ir. K. Verheyen
Period: 2009-2011

 

Smart land management for biobased economies

In the near future, the importance of biomass as a material and as a source of energy is expected to increase. Extracting biomass from forests is one way to answer this demand. On the other hand, biomass plays an important role in several ecological processes (that provide benefits to society). Thus the question arises how much biomass can be extracted from the forest without largely reducing the other ecosystem services. This leads to a geographical optimization exercise to find a land use management that is accepted by all stakeholders.
A case study is elaborated for Bosland, the largest forest of Flanders, to underpin decision making on this topic on a larger scale.

You can download this PhD thesis.

Contact person: ir. Pieter Vangansbeke (Pieter.Vangansbeke@UGent.be)
Financier: Flemish Institute for Technological Research (VITO)
Supervisor: prof. dr. ir. K. Verheyen, dr. L. Gorissen
Period: 2011-2015

 

Soil compaction due to mechanized forest harvesting

In forest harvesting increasingly more use is made of heavyweight logging machines. Through the process of soil compaction, this may cause an alteration of several soil physical characteristics, such as bulk density, penetration resistance, porosity, and chemical processes. In this way, it may also negatively influence important ecological characteristics (flora, pedofauna, tree vitality, growth, ...). This research attempts to quantify the impact of mechanized logging and the recovery potential of different soil types in an integrated and differentiated way. It also aims at determining the influence of pH, earthworm activity and litter quality on the recovery process.

You can download this PhD Thesis.

Contact person: dr. ir. Evy Ampoorter (Evy.Ampoorter@UGent.be)
Financier: Institute for the Promotion of Innovation by Science and Technology in Flanders (IWT)
Supervisors: Prof. dr. ir. K. Verheyen, Prof. dr. M. Hermy (KULeuven)
Period: 2007-2010

 

Spatial variability of throughfall water under beech

picture-doctoraat-jeroenEmpircal results demonstrate that the canopy structure of a forest ecosystem causes systematic spatial patterns in throughfall water. The aim of the research is to quantify this spatial effect of a hardwood canopy on the amount and chemical composition of the hydrological input to the forest floor. Rainwater passing through the canopy of a forest ecosystem is influenced in two ways, quantitatively as well as qualitatively. Quantitatively, the amount of precipitation is divided into a fraction that reaches the forest floor as throughfall and stemflow water, and a fraction that is intercepted and evaporated during and after a rain event. Qualitatively, throughfall water is generally enriched in most chemical elements compared to bulk precipitation, as a result of (i) dry deposition of particles and gases, and (ii) canopy leaching, i.e., release of ions from plant tissues. The research is conducted in a mixed forest stand (forest of Aelmoeseneie, Gontrode) that is part of the UNEP network International co-operative program on the assessment and monitoring of air pollution effects on forests. Throughfall and stemflow have consequently been monitored since 1995, but to study the small-scale spatial variability of thoughfall water in detail, the present research focuses on one dominant beech tree. The spatial variability of throughfall amount at the plot scale is measured by a set of automatically registrating tipping buckets, and is predicted at the event scale by modelling the interception amount using meteorological data with high temporal resolution. The following step is to describe and predict the spatial variability of nutrients in throughfall water. The final model results will be of great relevance for evaluating the efficiency and accuracy of different sampling strategies for throughfall water.

You can download this PhD Thesis.

Researcher: dr. ir. Jeroen Staelens (contact: Prof. dr. ir. Kris Verheyen, Kris.Verheyen@UGent.be)
Financier: Research Foundation - Flanders (FWO-Vlaanderen), research fund of the Ghent University (BOF)
Supervisor: Prof. dr. ir. K. Verheyen
Period: 2001-2005


The effect of phosphorous bioavailability on the recovery of plant communities in post-agricultural forests

The large-scale conversions of forest to agricultural land and subsequent afforestation represent a major disturbance across western European and eastern North-American landscapes during the past centuries. In certain landscapes up to 80% of the present forest area is recovering from former agricultural land use. Following the afforestation of agricultural land herb species need to establish again through recolonization. However, it is thoroughly documented that forest herbs have low abilities to recolonize post-agricultural forest (20-100 m per century). Forest herb diversity and the value for nature conservation of these recent forests is therefore much lower compared to ancient forest, i.e. forest that has never been cleared for agriculture at least since the oldest land use maps.

There is an overwhelming amount of evidence that the low dispersal capacity of many forest herbs in space and time (seed banks) partly accounts for this slow recovery. In addition, it is more than likely that persistently altered habitat conditions including higher nutrient availability further hampers forest herb layer recovery. The general aim of this project is to evaluate which forest herb communities are able to develop in recent forests established on phosphorous enriched soils (former agricultural land). Specific aims of this project are: (1) To determine if phosphorus and light availability actually have an effect on the production of biomass and the composition of a forest plant community. (2) To compare plasticity in allocation and performance between contrasting forest herbs with respect to phosphorus availability and light. The relation with colonization capacity is also checked. (3) To evaluate whether allocation and performance of forest herbs changes during forest development on former agricultural land as bioavailability of phosphorus changes.

Contact person: Prof. dr. ir. Kris Verheyen (Kris.Verheyen@UGent.be)
Financier: Research Foundation - Flanders (FWO)
Supervisors: Prof. dr. ir. K. Verheyen, Prof. dr. ir. S. De Neve, Prof. dr. M. Hermy (KULeuven)
Period: 2009-2011

 

The impact of the variation in tree leaf-out phenology on forest understorey plant communities

Picture research LanderThe tree diversity in forests may influence the ecosystem functioning. Here we will study the impact of the diversity of the tree population on the understorey plant community, a vegetation layer with a high functional importance that is disproportionate to its low biomass. Yet, we will not look at taxonomic tree diversity, but at the variation in leaf-out timing between trees (“phenological diversity”). Small differences in the timing of the canopy green up create comparatively large differences in the total yearly irradiance received at the forest floor. Since light availability in early spring, before the canopy closure, is crucial for the growth and reproduction of many understorey plant species, phenological diversity is expected to have a strong influence on the understorey.

Contact person: Prof. dr. ir. Lander Baeten (Lander.Baeten@UGent.be)
Financier: FWO
Period: 2012-2015

 

The importance of landscape fragmentation and climate change to forest herb species in Northern Europe (FLEUR)

According to the Intergovernmental Panel on Climatic Change, the rise in annual mean temperature in the northern temperate zones will reach 2,1-4,6ºC by 2080. A change in temperature will have its impact on plant species. Ancient forest species colonize new forests very slowly due to their low colonizing capacity. Because of the predicted temperature rise in the temperate zones, however, the actual observed colonizing capacity of these species can alter. The distribution of forest herbs in Western Europe can change due to these processes, especially at the northern and southern limits of their distribution range. This research will quantify plant and population traits along a NW-European (Sweden-Germany-Belgium-France) latitudinal gradient and try to predict forest species’ response to future climate change. Fifteen forest plant researchers study the importance of latitude and temperature to reproduction of a set of forest herb species. So far population characteristics and seeds of selected species have been collected along a gradient from Northern France to Northern Sweden. The seeds are germinated in incubators in Abisko (Sweden). Collaborators in the second years sampling and germination are Guillaume Decocq & Olivier Chabrerie (Universit de Picardie, Jules Verne, France), Martin Hermy (KULeuven, Belgium), Anette Kolb & Martin Diekmann (Bremen University),Thilo Heinken (Potsdam University), Hans Henrik Bruun & Karin Valtinat (Lund University), Johan Ehrl (Stockholm University), Lotta Strm (Ume University), Carol Baskin (Kentucky University, USA). Bente Graae (SLU, Sweden) co-ordinates the project.

Contact person: Prof. dr. ir. Kris Verheyen (Kris.Verheyen@UGent.be)
Financier: Research Foundation - Flanders (FWO)
Supervisors: Prof. dr. ir. K. Verheyen, Prof. dr. M. Hermy (KULeuven)
Period:2008-2011

 

The P bottleneck in the vegetation development towards species-rich grasslands in Fondatie-Heernisse

In the framework of the establishment of the Natura 2000 network, an EU-wide network of protected areas, ecosystems have to be restored on former agricultural land. However, restoration on agricultural land is hindered by both biotic and abiotic bottlenecks.  One of the most important bottlenecks for ecosystem restoration on former agricultural land is the large stock of nutrients, in particular nitrogen and phosphorus. Because of a surplus of animal manure in many Western European countries, agricultural soils were often intensively fertilised with slurry or farmyard manure during many decades. Within these different projects, we studied whether restoration of species-rich grasslands is possible on several parcels, at the moment in use of both agriculture and nature organisations. We made surveys of the vegetation, and sampled and analysed soil on different chemical characteristics, especially different P fractions, and evaluated which management regime (mowing, soil removal or P-mining) is most appropriate for ecosystem restoration.

Contact person: dr. ir. Andreas Demey (Andreas.Demey@UGent.be)
Financier: Flemish Land Agency (VLM)
Period: 2013-2014


Tree species effect on Cd and Zn mobility after afforestation of contaminated soils

 

In the Campine region zinc and lead were being refined from the end of the 19th century until mid 1970, which resulted in a widespread soil metal pollution. Due to the sandy soil type in the region, risks of leaching and spreading of the metals is increased. During the past years several polluted agricultural soils in the region have been afforested. Trees seem very well suited to reduce the metal mobility and thus the dispersion of the metals in the ecosystem, due to their extensive root systems and high transpiration capacity. But on the other hand, tree growth might enhance metal leaching, because of soil acidification and production of dissolved organic matter. The aim of this study is to investigate the effects of 6 different tree species on Cd and Zn mobility after 10 years of tree growth on agricultural, sandy soil near a former Zn refinery. The study focuses on the processes that have the most relevant influence on metal mobility. Those are, on the one hand, decomposition of litter and roots and the resulting modifications of soil properties (biogeochemical), and evapotranspiration on the other hand (biophysical). The final output of the study will be a model that predicts leaching of Cd and Zn to the groundwater as a function of tree species.

Researcher: dr. ir. Lotte Van Nevel (Lotte.VanNevel@UGent.be)
Financier: Ghent University
Supervisors: prof. dr. ir. K. Verheyen, prof. dr. ir. F. Tack, prof. dr. ir. S. De Neve, prof. dr. ir. J. Mertens
Period: 2007-2014

 

Validation and optimalisation of forest friendly harvesting in Flanders

 

Picture Aelmoeseneieforest exploitatie 4In forest harvesting, there is an ongoing trend to increase the use of heavy logging machines. This may cause soil degradation in forest ecosystems as the passes of these machines modify important soil structural characteristics through soil compaction, rutting and churning. The vulnerability of forest soils for these processes depends on several factors, such as soil texture and moisture. As part of an other research, an initial vulnerability classification was formulated mainly based on best professional judgement, but has to be validated and refined yet. In this project, vulnerability scores will be verified by means of observations in situ. The current state of the forest soils in Flandres and the recovery rate of the different soil types will also be examined.
The vulnerability classification mentioned above is associated with the use of forestfriendly harvesting methods. Unfortunately, many obstacles (underestimate of the machine impact, lack of time and/or money,...) prevent an easy implementation of these methods. Therefore, an intense dialogue with foresters and logging contractors will be held to sensitize concerning the problem of soil degradation and to develop economically and ecologically sound and acceptable solutions.

Contact person: Prof. dr. ir. Kris Verheyen (Kris.Verheyen@UGent.be)
Financier: TWOL, ANB, Agency for Nature and Forest, Flanders
Supervisor: Prof. dr. ir. K. Verheyen
Period: 2007-2008