To what extent do forest herbs recover after clearcutting in beech forest?

We studied the occurrence of 22 plant functional groups and the distribution patterns of 12 forest herbs in four clear-felled areas of different ages, and across ecotones between the forest and clearcuts in a 4383 ha beech forest in central Belgium. The main goal was to improve our knowledge on the clearcut harvesting system and its possible influence on herb vegetation. Within each study site, the herbaceous vegetation was sampled along a north–south and an east–west transect with points at 20 or at 10 m intervals. We studied a total of 82 vegetation relevés (4 m²) on 18 transects according to the Braun–Blanquet method. Around the study sites, the abundance of each species present was noted according to a grid-map with cells of 50 m × 50 m, up to a distance of 150 m from the clearcut edges. Differences in species’ cover percentage and frequency between the clearcuts and the surrounding matrix were tested. The colonisation rate for each species was calculated and possible effect of clearcut age on the plant composition was examined. Results of this study show that plant functional groups with a high conservation value, such as ancient-forest species, stress-tolerant species and autochorous species showed a progressive decrease in time after clearcutting. Most of the studied forest herbs had a lower frequency and/or cover in the clearcut areas than in the surrounding forest matrix. For some of these species, we found a progressive abundance decrease along a 150 m-gradient within the forest towards the clearcut (e.g. Dryopteris dilatata, Luzula pilosa, L. sylvatica, Oxalis acetosella). Others, such as Anemone nemorosa and Circaea lutetiana, are characterised by a regular cover in the forest which suddenly drops at the edge and sustains a very low level throughout the clearcut. If some forest herbs recover better than others, data collected so far indicate that most of the studied species are not able to recover such disturbed sites within a few years. We conclude that silvicultural systems should be adapted to the dispersal and recruitment limitations of forest herbs in order to enable their long-term conservation. To achieve this goal, management without large clear fellings and harvesting methods that never leave the ground completely bare are proposed as alternatives to the clearcutting system.     

Ecological factors controlling the abundance of non-native invasive black cherry (Prunus serotina) in deciduous forest understory in Belgium

The relation between invasion success of Prunus serotina and type of recipient habitat was studied in a large forest in central Belgium. The major emphasis in this study was the determination of factors controlling the abundance of P. serotina in understory strata. Environmental variables measured in 34 sample plots were slope, aspect, litter depth, soil type, pH, soil compaction, soil moisture, air humidity, soil temperature and light intensity in spring and late summer. Site conditions were also expressed indirectly for 210 sample plots using Ellenberg indicator values (soil nutrients, acidity, moisture, light conditions). Plots with P. serotina had lower mean indicator values for soil moisture, reaction (pH) and nitrogen, compared to plots without P. serotina. Twenty indicator species were identified for plots in which P. serotina occurs. The species richness of the herb layer was negatively correlated with the percentage cover of black cherry in the shrub layer. The percentage cover of P. serotina saplings in different overstory types was ranked as follows: Quercus > Pinus > Fagus > logging areas. Only three variables explained significant amounts of variation in Prunus abundance: slope, light intensity at 120 cm in April and light intensity at ground level in September. We found a positive response of black cherry seedlings to light intensity between 58 and 80% of full light (April measurements at 120 cm), while saplings showed a negative response within this range. Between 21 and 47% of full light (April measurements at 120 cm), seedlings were poorly represented whereas saplings showed a quite high cover. Between 0.3 and 1.8% light (September measurements at ground level), seedlings were almost absent while saplings maintained a high abundance. The results suggest that P. serotina shows a differential response to light intensity in relation to its development stage, i.e. the species is heliophilous at the seedling stage and becomes a shade plant at the sapling stage.     

African trypanosomosis: from immune escape and immunopathology to immune intervention

African trypanosomes can cause prolonged chronic infections through a mechanism of antigen variation whereby they manipulate the humoral immune system of their hosts. However, besides antigenic variation these extracellular parasites exert other immunoregulatory activities mainly mediated by innate cells in particular macrophage-like (M) cells. In this review, the modulation of M cells through parasite factors and host cytokines as well as their role in parasite control and immunopathology will be examined. The concept of M cell polarization into distinct activation states (M1, M2) that may contribute to trypanosusceptibility or resistance will be discussed. Finally, the possibility to interfere with such activation states hereby providing new therapeutical modalities in the treatment of this infectious disease will be illustrated.     

Native plants on experimental urban green roofs support higher community-level insect abundance than exotics

Urbanization is one of the multiple factors leading to global insect declines. As urbanization grows, green roofs represent a nature-based solution that could provide habitat for plants and animals within cities. Several characteristics of green roofs could enhance insect biodiversity. Nevertheless, little is known about the effects of plant origin on insect abundance from a multi-taxa perspective. Thus, our main goal was to evaluate the effects of plant origin, local resources, and urbanization level on green roofs’ overall insect abundance, the abundance of different taxonomic orders, and community composition. Using experimental green roofs, we compared insect communities between native and exotic plants across an urbanization gradient, in Córdoba city, central Argentina. On the roofs of 30 houses, we installed two blocks of a modular extensive green roof system, with either native or exotic plant species (6 species each). In March 2019, we used yellow pan traps and pitfall traps (N = 360) to sample insects and measured flower abundance and plant cover at each plant treatment. The urbanization level of each house was estimated by the Normalized Difference Vegetation Index (NDVI), the Normalized Difference Built-up Index (NDBI), and the Land Surface Temperature (LST). A total of 35,257 insects from 12 orders were registered, with Diptera, Hymenoptera, and Hemiptera as the dominant groups. Native plants supported significantly higher total insect abundance on both types of traps, independently from the urbanization level, flower abundance, or plant cover of each roof. The abundance of most of the taxonomic orders was higher in natives as well, but particular effects of the covariables were detected for certain groups. In addition, plant origin was an important factor for insect composition. Our results highlight that green roof design should prioritize native plants to enhance insect conservation while achieving more sustainable cities.     

Exploring the urban park use,preference and behaviours among the residents of Kuala Lumpur,Malaysia

The understanding of cross-cultural upon park usage is vital to be enhanced among public since findings that been discovered in the Western context are not own any similarities with the Asian context. In fact, it has been in a long run for the Western nations to primarily contextualized and conceptualized much on the literature of park usage. This study aims to look at how the people use and perceive urban parks in their daily life in the Malaysian cultural context, and also highlights the constraints faced by Malaysians while using the urban parks in the city of Kuala Lumpur. A survey consisted of 669 urban park users as the sample of the study (365 men, 304 females) aged between 18 and 73 years (M = 34.85, SD = 11.46) were conducted in five urban parks in Kuala Lumpur. Respondents were recruited based on a random sampling method, which composed of three main ethnic groups in Malaysia. Malaysians wanted to use the urban parks for multiple purposes including active activities and others. Most of them would visit the parks and spend their time in a group consisting of family members or friends rather than alone. The percentage of respondent with 74.7% stated their reason of visiting the urban park in order “to get fresh air”, followed by the factor of reducing stress and relaxing with 69.7%; and the latter reason would be “to exercise, play games or keep in shape” with 61.4%. More than 80% of the respondents claimed the parks in Kuala Lumpur are safe to be visited. This is because, majority of the respondents tend to visit the parks in group of family or friends rather than alone. In addition, most of the respondents would run their activities in parks during the weekends, which simultaneously make them to enjoy their day in such comfortable and secure way. The findings of this survey would contribute to a better understanding of the present park usage of Kuala Lumpur residents. With a better understanding of current park-visiting habits, various constraints faced by the residents related to public security and safety, the Kuala Lumpur City Hall have been suggested to develop more comprehensive strategy in order to provide engagement and urban parks stimulation for its residents. In addition, this study is also fruitful for Kuala Lumpur future parks in terms of its development, design and management.     

Creating alternative spaces and articulating needs: Challenging gendered notions of forestry and forest ownership through women's networks

The forest industry continues to be men dominated, dependent on forest owners' supply of raw material and of significant importance to the national and local economy and economic development in Sweden. The interconnection between masculinity and the work, knowledge, forest owners and professionals in the sector contributes to exclusion of women. In response to this, women forest owners have formed networks in different local areas. Through focus group interviews, this study examined the strategies, functions and positions of these networks, both in their individual locations and the overall policy processes of gender mainstreaming of the sector, to scrutinise the reproduction of gender inequities and the gendered notion of forestry. The results show how the networks are acting to expand the discursive space, establish alternative publics and empower their members by inventing and circulating counterdiscourses. The different strategies adopted by the networks appear to have emerged in response to contemporary political processes. The conclusion is that one single public sphere cannot encompass the diversity of the contemporary forestry sector, indicating a need to contain a multiplicity of publics, both to challenge the modes of deliberation that mask domination and to facilitate transformative processes.     

Tree planting under customary tenure systems in malawi: impacts of marriage and inheritance patterns

Debates about land tenure throughout Africa, and in Malawi in particular, are central to development strategies. Marriage and inheritance patterns are important aspects of tenure that influence how individuals acquire land and trees thereon. Accordingly, such patterns may influence the management of natural resources, such as trees. Along these lines, policy makers in Malawi have been suggesting that uxorilocal marriage, where the man resides in the woman’s village upon marriage, discourages tree planting. In this study we investigate how marriage and inheritance patterns affect tree-planting behavior by gender in two villages. Results show that tree planting by men may indeed be dissuaded by uxorilocal marriage patterns. Furthermore, tree planting by married women is not necessarily promoted under uxorilocal patterns. Rather, a high incidence of non-married women appears to be associated with increased tree planting by women.     

Determination of methylmercury in fish by headspace-gas chromatography with microwave-induced-plasma detection

Some additional experiments checking out the extraction method recently developed for the determination of MeHg in biological samples by Headspace Gas Chromatography with Microwave Induced Plasma atomic emission spectroscopy detection were performed. In this method, the MeHg is cleaved from the biological tissue by H₂SO₄ and by addition of iodoacetic acid converted to the iodide form. These reaction steps take place in a closed headspace vial. The H₂SO₄ concentration and the sample matrix have an important influence on the recovery of the MeHg from the sample and these effects are discussed. The method was then applied to the determination of MeHg in cod fish caught in the North Sea. Levels found ranged from 0.13 to 0.63 μg g⁻¹ dw with a mean of 0.33 μg g⁻¹ on the 25 samples analyzed. The total Hg content of these samples was also determined by Cold Vapour Atomic Absorption Spectrometry, and all data pooled ranged from 0.19 to 0.90 μg g⁻¹ with a mean of 0.40 μg g⁻¹. A study of the ratio MeHg/total Hg revealed that MeHg always constituted more than 60 % of the total Hg level, with a mean of 83 % on the 25 samples. The percentage MeHg did not increase or decrease markedly when the total Hg content increased. It could be concluded that these North Sea samples are not much contaminated by Hg and are surely suitable for consumption.     

The impact of forest paths upon adjacent vegetation: effects of the path surfacing material on the species composition and soil compaction

This paper describes the vegetation which develops around forest paths (closed to public motor vehicles) in a 4383 ha-beech forest in central Belgium. The main purposes of these investigations were to analyse how far into the forest stands, paths have an influence on the surrounding plant species composition; and to acquire more specific information on the particular effect of some types of surfacing materials. The results show that forest paths have a significant effect on the surrounding plant assemblages. Some species are significantly associated with one particular type of surfacing material. Globally, the presence of a path results in an increase in the number of ruderal species, disturbance indicators, nitrogen-demanding species and indicators of basic conditions. Eutrophication and pH increase, as inferred from the plant composition, are perceptible up to a minimum distance of 10 m from the path. The consequences for long-term conservation of the woodland flora are discussed.     

The rhizosphere soil of diseased tomato plants as a source for novel microorganisms to control bacterial wilt

Plant growth promoting rhizobacteria (PGPRs) are used for biocontrol of bacterial wilt caused by Ralstonia solanacearum. They are commonly isolated from the rhizosphere of healthy plants and are scarce in the rhizosphere of diseased plants. We hypothesized that a pathogen-prevalent environment, such as the rhizosphere of infected plants, would be a good or better source for isolating PGPRs than the rhizosphere of healthy plants. In order for these PGPRs to survive successfully in a pathogen-prevalent environment, they must have particularly well-developed survival strategies under the stresses exerted by pathogen activities, which would be of value for their use as biocontrol agents. To test this hypothesis, R. solanacearum-antagonistic bacteria were screened from the rhizospheres of diseased and healthy tomato plants. In total, 110 rhizobacteria were isolated, 18 of which showed antagonism to R. solanacearum in vitro. Among the 18 antagonistic strains, 11 (out of 60) were from the rhizosphere of diseased plants, with inhibition diameter zones ranging from 11.2 to 15.2 mm, whereas 7 (out of 50) were from the rhizosphere of healthy plants, with inhibition diameter zones ranging from 11.5 to 30.5 mm. Strains WR4, WR21, and WR42 from diseased plants rhizosphere, and HR61, HR62, and HR92 from healthy plants rhizosphere, were chosen to investigate their biocontrol efficacies (BCEs) in greenhouse condition. Results showed that WR-isolates performed better in reducing disease incidence (DI) than those HR-isolates. Population densities of R. solanacearum in the rhizosphere soil and crown section of tomato plants were lower in WR-isolate treatments than those in HR-isolate treatments. The best biocontrol effect was achieved by inoculating the strain WR21, followed by WR4, WR42, HR92, HR62, and HR61. Root colonization test showed WR21 had the highest root-colonizing capacity compared with 5 other antagonists. BCEs were positively (r = 0.747) correlated with root-colonizing capacities, but were negatively (r = −0.797) correlated with inhibition zones. In conclusion, the rhizosphere of diseased tomato plants is a good reservoir of biocontrol bacteria.