Sandrine Godefroid

Temporal analysis of the Brussels flora as indicator for changing environmental quality

With their species diversity, their population abundance and their integrator characters, higher plants represent useful tools to solve problems concerning the environment analysis and management. As they are good bioindicators, plants integrate many environmental parameters and can help to reveal the misworking of the ecosystems. Within this framework, a recent and complete survey of the phanerogamic flora of the Brussels area was carried out by the method of the floristic grid-map based on 1 km - squares. A comparison with earlier data has allowed us to appreciate the consequences of half a century of human activities on plant diversity in the urban ecosystem. The basic aim is to present a method of diagnosis and mapping that has been used, so as to turn the descriptive information about the biological environment of the area into a series of guidelines for land-use regulation and management within the city. Ellenbergs indicator values were used to express the relationship of flora to soil nitrogen, moisture content, reaction, light and temperature. Considering the biological characteristics of new floristic components and plants which have become rare or disappeared, it was possible to draw conclusions about the alterations in environmental conditions in Brussels. Our results show that the number of species did not differ significantly from 1940 until now. However, considerable changes have appeared during this period: there is a clear increase in the number of alien species; the flora of the Brussels area is becoming more nitrophilous and tolerant to shade, while it does not differ with respect to soil moisture, reaction and temperature. Human activities have disturbed the distribution and abundance of many species, inducing a decline or disappearance Of some of them, principally those which are associated with cropland, with marshland and woodland. On the other hand, numerous species have recently appeared in the city, many of which are aliens. The comparison between indigenous and alien species has revealed that their occurrence depends upon their ecological requirements: alien species are more tolerant of nitrogen, light, drought, heat and alkaline soils. The response of the flora to human impact is clearly demonstrated. Such sensitivity has obvious implications for both conservation and management. Circumstances, where Brussels plant monitoring is carried out permitting the avoidance of potential disaster and the saving of valuable biological resources, are developed. Arguments for the conservation of wild plants in cities also lead to some remarks concerning nature conservation practices in Brussels.

Distribution pattern of the flora in a peri-urban forest: an effect of the city–forest ecotone

We studied the spatial variation of plant assemblages in a 4383 ha deciduous forest in the periphery of Brussels. All vascular plant species were recorded following a grid-map of 1 km 2 -cells totally or partly covered by the forest. A total of 414 plant species was observed. Species composition and plant functional groups in forest edges and the neighbouring forest interior are studied. The study quantifies plant functional groups (e.g. ancient forest plants, true forest species, rare species, geophytes, C, S or R-strategists) in the plots and tests for relationships with the geographical position in the forest according to a city-to-forest gradient. Our results led us to identify distinct characteristics of forest flora based on the distance to the actual city border. The study revealed significant outer edge effects on the flora. Plant composition of the forest interior and forest edge can be separated by ordination on species composition, suggesting that these two biotopes have a distinct species assemblage. χ 2 -test and Two-Way-Indicator-Species-Analysis detected significant edge-associated species that were recorded exclusively in the edge or were the most frequent in the forest edge. We found that forest stands close to urban areas support populations of indicators of disturbance (pioneer species, C and R-strategists and aliens) to plots which are distant from the city. However, our observations also suggest that species groups with high conservation value (e.g. ancient forest species, or rare species) may also be more represented at the edge than in the core of the forest. Moreover, no forest specialists which would occur only in the interior zone were found. These observations are in disagreement with the hypothesis that true forest plants and species groups of high conservation value would be more frequent in the forest than on the borders. These findings are applicable to the management of forests in an urban context.

Computing diversity from dated phylogenies and taxonomic hierarchies: does it make a difference to the conclusions?

Recently, dated phylogenies have been increasingly used for ecological studies on community structure and conservation planning. There is, however, a major impediment to a systematic application of phylogenetic methods in ecology: reliable phylogenies with time-calibrated branch lengths are lacking for a large number of taxonomic groups and this condition is likely to continue for a long time. A solution for this problem consists in using undated phylogenies or taxonomic hierarchies as proxies for dated phylogenies. Nonetheless, little is known on the potential loss of information of these approaches compared to studies using dated phylogenies with time-calibrated branch lengths. The aim of this study is to ask how the use of undated phylogenies and taxonomic hierarchies biases a very simple measure of diversity, the mean pairwise phylogenetic distance between community species, compared to the diversity of dated phylogenies derived from the freely available software Phylomatic. This is illustrated with three sets of data on plant species sampled at different scales. Our results show that: (1) surprisingly, the diversity computed from dated phylogenies derived from Phylomatic is more strongly related to the diversity computed from taxonomic hierarchies than to the diversity computed from undated phylogenies, while (2) less surprisingly, the strength of this relationship increases if we consider only angiosperm species.

Identifying indicator plant species of habitat quality and invasibility as a guide for peri-urban forest management

A floristic survey has been carried out in a peri-urban forest, the Sonian Forest in Brussels, to identify indicator plant species in the herbaceous layer, which could be used as an aid within the framework of a more sustainable management of the forest. Three hundred and seventy two (372) taxa have been identified, 33 of which are non-native (i.e. non-indigenous species regarding the study area, whether invasive or not). Criteria of habitat quality that have been chosen are the species richness, the commonness of the habitat, based on constitutive species, and its invasibility (vulnerability for invasion). On the basis of a comparison of the value of these criteria when each considered (potential indicator) species is present or not, 17 species have been recognised as reliable indicators of at least one of these three criteria. In particular, vegetation types containing either Anthriscus sylvestris, Galeopsis tetrahit or Senecio ovatus were found to be more susceptible to invasion than other habitats. The way to how the predictability of invasions might be effectively used as a management tool is discussed. Furthermore, we found a positive significant correlation (Bonferroni corrected probabilities) between the species richness and luminosity factor (derived from Ellenbergs indices), and the proportion of grassland and wetland species. The species richness was significantly negatively correlated with the proportion of woodland species. An increase in commonness was significantly correlated with a decrease in the proportion of geophytes. The usefulness of these results as an ecological basis for forest management is discussed.

Plant reintroductions: the need for a global database

Plant reintroductions include labor-intensive, costly, and time-consuming work and often cannot guarantee a successful outcome. In order to maximize the chances of success, it is therefore of utmost importance to appropriately select target species, release site, cultivation and reintroduction methodology, and management technique of the out-planting site. Case studies, best practice and experiences of plant reintroductions are however not sufficiently disseminated to the plant conservation community, most often remaining in unpublished internal reports to which access is difficult. We suggest that this is a major problem for conservationists and it requires the establishment of a framework for rapid and effective broadcasting of information on plant reintroduction programs. We propose a set of variables for a centralized web-based interface which could provide the necessary information in a standardized and accessible form.

Effects of soil mechanical treatments combined with bramble and bracken control on the restoration of degraded understory in an ancient beech forest

This paper describes the ground floor vegetation that developed four years after tillage implements in an ancient beech forest in central Belgium. The purpose of this study was twofold: (1) to explore whether tillage has a lasting effect on soil compaction and soil moisture as well as on vegetation characteristics; and (2) to analyse whether two distinct tillage treatments (rotary plough vs. disc plough), combined with vegetation control when necessary, have the same effect on soil compaction, soil moisture and plant establishment. Of the 29 species recorded, 15 showed a significant recovery after soil loosening in the studied forest area. Interestingly, different tillage treatments did not have the same influence on plant establishment. Treatment effects on soil structure and/or moisture status can be considered as causing the observed growth response.RésuméCette étude décrit la flore herbacée qui s’est développée quatre années après la mise en place d’expériences de traitement mécanique du sol dans une ancienne hêtraie dans le centre de la Belgique. Les objectifs furent : (1) explorer si le traitement mécanique du sol a un effet durable sur la compaction et l’humidité du sol et sur les caractéristiques de la végétation; et (2) analyser si deux traitements effectués avec des machines différentes (crabe et fraise rotative), combinés à un contrôle de la végétation si nécessaire, ont le même effet sur la compaction et l’humidité du sol et sur l’établissement des plantes. Parmi les 29 espèces inventoriées, 15 ont montré un développement significatif suite au labour du sol dans les zones expérimentales étudiées. Il est intéressant de constater que les différents traitements n’ont pas eu la même influence sur l’établissement des espèces végétales. L’effet des traitements sur la structure et/ou l’humidité du sol peut être considéré comme étant la cause de la réponse végétale observée.

Pre-translocation considerations in rare plant reintroductions: implications for designing protocols

The existing literature on plant translocations focuses on post-translocation outcome while still overlooking issues related to the preparation phases. Yet, plant translocation programmes face significant pre-translocation challenges. In the present study, we want to share our pre-transplant experience on four rare plant species (Arnica montana, Campanula glomerata, Dianthus deltoides and Helichrysum arenarium), highlighting aspects we need to focus on while planning plant translocations. We emphasize some issues that need to be overcome before any translocation is undertaken during the four steps of translocation preparation, i.e. the selection and profiling of the target species, the seed collection, the development of propagation protocols and the assessment of plant fitness of the populations used as seed source. We discuss the implications of our results for designing translocation protocols. Our findings on A. montana show that if local seed sources are constrained to small remnant populations, seed quality may be poor. Preliminary tests using different kinds of growing medium provided valuable information for optimizing plant propagation protocols. Although it is attractive to establish propagation protocols using seeds obtained via Index Seminum (to avoid wasting collected source seeds), the results obtained were not always reproducible on the seeds collected in the wild source populations. Differences in pre-translocation plant fitness were also detected between seed source populations, which might reflect genetic diversity and maternal effects. As the translocated plants should capture as much genetic diversity as possible to ensure a high adaptive potential and improve establishment success, multisource reintroductions can be recommended.

Seed banking of endangered plants: Are we conserving the right species to address climate change?

The increasing awareness of the effects of climate change on plant distributions in situ has made the appropriate application of ex situ techniques more crucial. These ex situ conservation techniques need to be targeted to priority species identified at risk from climate change. The present paper assesses the sensitivity of plant species to climate change in Belgium and explores the current conservation status of those species potentially vulnerable to climate change. We then checked whether these species were included in ex situ collections. The whole Belgian flora has been assessed (a total of 1,396 native plant species). We evaluated whether each of these species occurs in a “climate change-vulnerable” habitat, having therefore a higher probability to be impacted by climate change. The assessment revealed that there are at least 415 native plant species (30% of the Belgian native flora) that appear to be vulnerable to climate change during the next decades. Results also showed that about one-third of the species currently included in the red list may have their situation made potentially worse due to climate change. In addition, depending on the region, between 45 and 67% of the species that are currently not threatened in Belgium are likely to become so due to climate change. It also appeared that only 32% of these climate change-vulnerable species are currently held ex situ. We conclude that there is a need to identify gaps in existing ex situ collections as an urgent priority and ensure that species potentially vulnerable to climate change are conserved ex situ.

Limited evidence of local phylogenetic clustering in the urban flora of Brussels

As species functioning is not randomly distributed with respect to phylogeny, we should expect that species assemblages, which are subject to the same environmental filters, often possess a clustered phylogenetic structure. This locally clustered phylogenetic structure is usually detected with randomization tests. In this paper we apply a test of community phylogenetic clustering that takes into account the non-random distribution of species frequency across the phylogeny of the urban flora of Brussels (Belgium). Our results provide only moderate support to the idea that a locally clustered phylogenetic structure is central to the coarse-scale patterns of species co-occurrence of this urban area. The abiotic drivers that promote a locally clustered phylogeny in cities like Brussels are also shortly discussed.

Native and introduced plants differ in their distribution patterns in southern England

Abstract The distribution patterns of native and introduced plants were investigated using floristic surveys of 4 km2 grid squares collected between 1987 and 2008 in lowland England. Variograms were used to compare the autocorrelatory range of 1,293 different species with their native status. Various patterns of spatial distribution were seen in the flora, including species that are highly spatially autocorrelated, through to species whose distribution is spatially uncorrelated at this scale. Almost all native plants showed autocorrelation in their distribution at distances of <10 km, whereas introduced plants either showed no autocorrelation or over shorter distances than native plants. This difference between native and introduced plants has an important consequence: when biogeographical range size is measured using large (>100 km2) grid squares, as it often is, this can lead to the wrong conclusion that introduced plants occupy more area than native plants with a similar range.