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Background Despite the increasing number of epigenomic studies in plants, little is known about the forces that shape the methylome in long-lived woody perennials. The Lombardy poplar offers an ideal opportunity to investigate the impact of the individual environmental history of trees on the methylome. Results We present the results of three interconnected experiments on Lombardy poplar. In the first experiment, we investigated methylome variability during a growing season and across vegetatively reproduced generations. We found that ramets collected over Europe and raised in common conditions have stable methylomes in symmetrical CG-contexts. In contrast, seasonal dynamics occurred in methylation patterns in CHH context. In the second experiment, we investigated whether methylome patterns of plants grown in a non-parental environment correlate with the parental climate. We did not observe a biological relevant pattern that significantly correlates with the parental climate. Finally, we investigated whether the parental environment has persistent carry-over effects on the vegetative offspring’s phenotype. We combined new bud set observations of three consecutive growing seasons with former published bud set data. Using a linear mixed effects analysis, we found a statistically significant but weak short-term, parental carry-over effect on the timing of bud set. However, this effect was negligible compared to the direct effects of the offspring environment. Conclusions Genome-wide cytosine methylation patterns in symmetrical CG-context are stable in Lombardy poplar and appear to be mainly the result of random processes. In this widespread poplar clone, methylation patterns in CG-context can be used as biomarkers to infer a common ancestor and thus to investigate the recent environmental history of a specific Lombardy poplar. The Lombardy poplar shows high phenotypic plasticity in a novel environment which enabled this clonal tree to adapt and survive all over the temperate regions of the world.

Non-native Berberis aquifolium is an invasive species in Belgian coastal dunes. With its strong clonal growth through suckers, this evergreen shrub outcompetes native species and affects dune succession. To prevent further secondary spread and mitigate its impact, there was an urgent need for knowledge on the effectiveness of control measures, both at the plant and habitat level. Here, we report on a first control experiment. Individual B. aquifolium clones were subjected to one of four treatments (manual uprooting, foliar herbicide application, stem cutting followed by herbicide or salt application), with regrowth being measured up to one year after treatment. We analyzed the relationship between kill rate, treatment, dune area, plant volume and number of plant stems using a generalized linear model. Berberis aquifolium plants proved most susceptible to foliar herbicide application (5% glyphosate solution), resulting in 88% (64%–97%) of the clones dying after treatment. The predicted kill rate decreased with an increasing number of stems under all treatments. We discuss the limitations of our experiment and the potential for actual field application of the different treatments. We present some guidelines for future control that may become further refined as experience builds up and we provide some recommendations for tackling invasive alien species in Atlantic dune ecosystems.

Monitoring global biodiversity is essential for understanding and countering its current loss. However, monitoring of many species is hindered by their difficult detection due to crepuscular activity, hidden phases of the life cycle, short activity period and low population density. Few statistical power analyses of declining trends have been published for terrestrial invertebrates. Consequently, no knowledge exists of the success rate of monitoring elusive invertebrates. Here data from monitoring transects of the European stag beetle, Lucanus cervus , is used to investigate whether the population trend of this elusive species can be adequately monitored. Data from studies in UK, Switzerland and Germany were compiled to parameterize a simulation model explaining the stag beetle abundance as a function of temperature and seasonality. A Monte-Carlo simulation was used to evaluate the effort needed to detect a population abundance decline of 1%/year over a period of 12 years. To reveal such a decline, at least 240 1-hour transect walks on 40 to 100 transects need to be implemented in weekly intervals during warm evenings. It is concluded that monitoring of stag beetles is feasible and the effort is not greater than that which has been found for other invertebrates. Based on this example, it is assumed that many other elusive species with similar life history traits can be monitored with moderate efforts. As saproxylic invertebrates account for a large share of the forest biodiversity, although many are elusive, it is proposed that at least some flagship species are included in monitoring programmes.

Hybridization and genetic swamping by planted exotic Populus taxa are putative threats for native Populus resources. We investigated the potential for hybridization between the exotic hybrid Populus x canadensis Moench and its wild relative, the European black poplar ( Populus nigra L. ) , by a series of pollination experiments in the greenhouse. We also tested the effect of mixtures of pollen from the taxon’s own pollen and pollen of the foreign taxon on mating success in reciprocal crosses. We observed reduced pollen and seed viability of the hybrid clones of P. x canadensis compared to the clones of the parental species P. nigra . Surprisingly, when in combination with pollen of its wild relative P. nigra , pollen of exotic P. x canadensis sired significantly better on its own flowers. In poplar breeding, the pollen mentor technique which uses pollen mixes of artificially inactivated conspecific pollen and untreated incompatible foreign pollen, has been successfully used to overcome incompatibility barriers. The results of this study suggest that in the wild, where mixed pollen loads are common, similar effects as the pollen mentor effects may enhance the invasiveness of exotic P. x canadensis . This study helps to explain former field observations and contributes to the understanding of potential environmental impacts of commercial exotic and transgene poplar plantations.

Wild boar (Sus scrofa) reappeared in Flanders, Belgium in 2006 after more than half a century of absence. Besides being a native and highly valued game species in Europe, wild boar are also known to be responsible for car collisions, crop damage, disease transmission, and ecological damage at high densities. The management of wild boar therefore seeks to balance these positive and negative impacts. Given the highly fragmented landscape in Flanders and its multifunctional use, coexistence with wild boar is only possible through integrated management involving relevant stakeholder groups. However, to be successful, this requires that the management objectives, the overall wild boar policy of the Flemish authorities, and management actions are supported by the stakeholders. To assess the support for the current management, we conducted a survey among members of the 3 key stakeholder groups: farmers, hunters, and conservationists. Our survey assessed the importance stakeholders attribute to different management objectives, their support for the current legal provisions, and how desirable the different stakeholder groups considered possible management actions. The potential for conflict index was used to analyze the (dis)agreement between and within stakeholder groups. Reducing or preventing crop damage and the risk for car accidents are indicated as being the most important management objectives by all 3 stakeholder groups. Stakeholder groups differ strongly in their support for the current legal provisions. Those stakeholders that have to implement the legal provisions or are mostly affected by these laws are less supportive than others. The desirability of the possible management actions strongly varied according to the different stakeholder groups. Contrary to other studies, the desirability of a possible management action was hardly influenced by the management objective it tried to achieve.

Prior to the construction of an offshore wind farm at the Belgian Thorntonbank, local seabird abundance was studied by means of ship-based surveys. ‘Seabirds at sea’ count data, however, exhibit extreme spatial and temporal variation, impeding the detection of human impacts on seabird abundance and distribution. This paper proposes a transparent impact assessment method, following a before–after control–impact design and accounting for the statistical challenges inherent to ‘seabirds at sea’ data. By simulating a broad range of targeted scenarios based on empirical model coefficients, we tested its efficacy in terms of power and investigated how the chance of statistically detecting a change in numbers is affected by data characteristics, monitoring period and survey intensity. Because of high over-dispersion and/or zero inflation, the power to detect a 50% decrease in numbers was generally low, but did reach 90% within less than 10 years of post-impact monitoring for northern gannet (Morus bassanus) and common guillemot (Uria aalge).

Non-native Berberisaquifolium is an invasive species in Belgian coastal dunes. With its strong clonal growth through suckers, this evergreen shrub outcompetes native species and affects dune succession. To prevent further secondary spread and mitigate its impact, there was an urgent need for knowledge on the effectiveness of control measures, both at the plant and habitat level. Here, we report on a first control experiment. Individual B.aquifolium clones were subjected to one of four treatments (manual uprooting, foliar herbicide application, stem cutting followed by herbicide or salt application), with regrowth being measured up to one year after treatment. We analyzed the relationship between kill rate, treatment, dune area, plant volume and number of plant stems using a generalized linear model. Berberisaquifolium plants proved most susceptible to foliar herbicide application (5% glyphosate solution), resulting in 88% (64%–97%) of the clones dying after treatment. The predicted kill rate decreased with an increasing number of stems under all treatments. We discuss the limitations of our experiment and the potential for actual field application of the different treatments. We present some guidelines for future control that may become further refined as experience builds up and we provide some recommendations for tackling invasive alien species in Atlantic dune ecosystems.

Germination and establishment of ancient forest species are bottlenecks in forest habitat restoration. We hypothesised that tree species can influence these processes on acidification sensitive soils through their effects on the soil. Seeds of seven ancient forest species were sown in soil collected in a post-agricultural forest under four different tree species, notably Acer pseudoplatanus, Alnus glutinosa, Fagus sylvatica and Populus x euramericana. Germination of four species was affected by tree species, while only Scilla non-scripta was indifferent and germination of Anemone nemorosa and Paris quadrifolia was unsuccessful. The acid intolerant Primula elatior only germinated in the soil of P. x euramericana but also the acid tolerant Lonicera periclymenum and Stellaria holostea performed best in the soil of P. x euramericana and worst in the soil of A. glutinosa. Lamium galeobdolon preferred the soil of A. pseudoplatanus. Germination of competitive seed bank species was much more successful in the soil of P. x euramericana than in soil of other tree species. From our results we deduce that tree species selection can affect germination of ancient forest species. Forest managers should be aware of the effects of tree species on their colonisation chances and favour trees with good decomposable litter especially on acidification sensitive soils.

Question: Does clear-felling influence forest herb colonization into postagricultural forest? Location: A stand of poplar cultivars with a dense understorey of Acer pseudoplatanus in Muizen forest (northern Belgium), planted in 1952 on farmland adjacent to ancient forest and clear-felled in 1997. Methods: Shade-tolerant forest herbs were surveyed in 112 grid-based sample plots: just before clear-felling, and 5 and 10yr afterwards. Shade-tolerant herbs were subdivided into ancient forest species (AFS) and other shade-tolerant species (OSS). Effects of clear-felling on species number per plot, total cover per plot and colonization rate of species groups were compared using nonparametrical tests. Species number per plot was modelled by means of generalized linear mixed models (GLMMs), with inventory time, distance to the nearest parcel edge, and cover of light-loving species (LS) as explanatory variables. The C-S-R signature (competitive, stress-tolerant and ruderal strategies, respectively) shift of sample plots was calculated on the selected shadetolerant species. Results: Frequency of most species increased during the 10-yr period. Number of OSS increased more and faster than that of AFS. OSS increased to the level of the adjacent forest, but was lower where LS cover remained high. There was a positive correlation between the change of the colonization rate and the competitive plant strategy. Conclusions: We assume that clear-felling stimulated generative reproduction of shade-tolerant herbs, whereas quickly emerging woody species controlled competitive exclusion by LS. Succession of dark and light phases, such as provided by an understorey managed as a coppice, could promote colonization of shade-tolerant herbs into post-agricultural forest.