Urban Bees Benefit from a Native Forest Species Grown in a City Environment–A Case Study of Geranium Phaeum L.

This two-year study tested whether urban bees benefit from the forest perennial Geranium phaeum L. replanted from natural stands to an urban environment. The flowering abundance and phenology, spectrum of insect visitors, nectar and pollen production, and the energetic value of nectar were investigated in Lublin, SE Poland. The apiarian value of G. phaeum was studied for the first time. The species bloomed abundantly from late April to early June and can be regarded as a valuable spring food resource for urban bees, mainly bumblebees, which accounted for >50% of all visits in both years of study. Bees collected mainly nectar. The highest daily pollen and nectar sugar amount offered by a plant reached 73.7 mg and 36.5 mg, respectively, with the caloric value of nectar of 146 cal. The estimated mean sugar yield, caloric value of nectar and pollen yield · m−2 were 1.7 mg, 6.9 kcal, and 3.4 mg, respectively. The current study confirms the advantage of using native plants in urban landscaping and proves their positive role in strengthening both wild and managed bee populations in cities. The finding that wild plants translocated from the natural habitat can develop a self-sustaining population in the urban environment and establish beneficial relationships with urban bees is of interest in terms of the conservation of both native plants and pollinators.

Identification of Alnus glutinosa L. and A. incana (L.) Moench. Hybrids in Natural Forests Using Nuclear DNA Microsatellite and Morphometric Markers

Two alder species (Alnus glutinosa and A. incana) have overlapping distribution, naturally occur in Lithuania, and are considered ecologically and economically important forest tree species. The objective of our study was to estimate the likelihood of spontaneous hybridizations between native alders in natural stands of Lithuania based on leaf morphology and nuclear microsatellite markers. The sampled trees were assigned to the three taxonomic groups of A. glutinosa, A. incana, and potential hybrids based on the leaf and bark morphological traits. The genetic differentiation and potential hybridization between these three groups was tested based on 15 nSSR markers. We identified studied Alnus spp. individuals as pure species and hybrids. Two microsatellite loci were reported as discriminating well between these species. We concluded that our results showed the highest likelihood of two genetic group structures, a clear genetic differentiation between the morphology-based groups of A. glutinosa and A. incana, and rather variable likelihood values in the putative hybrid group. The results provide important implications for genetic conservation and management of Alnus spp.

An Agronomic Approach to Pine Nut Production by Grafting Stone Pine on Two Rootstocks

Stone pine (Pinus pinea) grows in natural stands within the Mediterranean basin and its nut is highly appreciated for its nutritional profile. Nevertheless, a decline in this species due to biotic and abiotic damages is currently being clearly observed. This situation has led to its development as a nut crop, to try to save its production and obtain regular harvests over the years. Under this agronomic scenario, the aim of this work was to compare the behavior of the stone pine grafted onto two rootstocks, P. pinea (PP) and P. halepensis (PH), by evaluating cone productivity, tree growth response, mast seeding patterns and pine nut composition. The field test was composed of 14 PH and 14 PP, randomly distributed into groups of 4–5 trees/rootstock. Data were from seven productive growing seasons. The results show higher growth and ripe cone production on PP rather than PH, although the productivity (cones/m2 canopy) was similar. Any effect of rootstock was observed on the mast seeding pattern and weight of cones, while the pine nut composition showed differences in the fatty acids content. The global quality of production was similar in PH and PP.

Gum Arabic Production and Population Status of Senegalia senegal (L.) Britton in Dryland Forests in South Omo Zone, Ethiopia

Senegalia senegal (L.) Britton is a multi-purpose dryland tree species that produces gum arabic, a commercially valuable product. However, this resource is underused in Ethiopian dryland areas. The aim of this study was to evaluate the population status and potential gum yield of S. senegal growing in natural stands in South Omo Zone, Ethiopia. Forty-five sample plots, each measuring 20 × 20 m, were established at 500 m intervals along transects, with 1 m2 subplots located within the main plots to determine regeneration. S. senegal trees with a diameter at breast height of between 2 and 12 cm were most prevalent. Forty-two tree species were associated with S. senegal, of which 16 were gum- and resin-producing species. S. senegal was positively associated with Vachellia tortilis, Senegalia mellifera, Vachellia nilotica, Commiphora edulis, and Dobera glabra. Senegalia senegal comprised approximately 35% of regenerating trees. The maximum gum arabic yield obtained was 3948 g tree−1. Linear models of dendrometric variables indicated that gum arabic yield is better predicted by tree diameter than by height. Despite the limitations of this pioneer survey, the population status and yield potential suggest that gum arabic could be sustainably produced and commercialized in natural stands of S. senegal in the studied dryland areas, providing local communities with supplementary seasonal incomes.

Land use impacts on Boswellia dalzielii Hutch. an African frankincense tree in Burkina Faso

Boswellia dalzielii Hutch., an African frankincense tree, is a socio-economically important aromatic and medicinal tree. It is currently threatened by uncontrolled exploitation, and therefore requires action to ensure its sustainable management. This study assessed the population structure and regeneration of its natural stands across three land use types in Burkina Faso: woodlands, fallows and farmlands. Sixty, fifty and fifty 50 m × 20 m plots were established respectively in woodlands, fallows and farmlands. All the plots were surveyed for adult tree (dbh ≥ 5 cm) density, dbh, total height and health conditions. Data on regeneration density (dbh < 5 cm), source (generative, stem shoots, suckers), total height and collar diameter were also collected. The results show similar total tree heights (7.0 m-9.0 m) but significantly (p < 0.05) smaller tree dbh in woodlands (mean ± SD: 20.5 ± 0.49 cm) and fallows (29.3 ± 0.64 cm) than in farmlands (32.8 ± 0.15 cm). Adult tree density (trees/ha) was 1.3 and 2.7 times higher in woodlands (82.37 ± 6.57) than in fallows (62.00 ± 3.98) and farmlands (30.02 ± 1.63), respectively. The density of regeneration in woodlands was 28 and 6 times higher than in fallows and farmlands, respectively. The majority (> 50%) of regenerating plants were suckers and no seedling regeneration was found in farmlands. The distribution of trees in diameter classes was J-shaped in woodlands, bell-shaped in farmlands and positive asymmetric in fallows, indicating recruitment bottlenecks. We found that 80.18% of individuals encountered were unhealthy. Intensive debarking and cutting were the main threats to the species and no conservation strategy was in place in the study region. We suggest measures to reduce intensive debarking and cutting, which should contribute to better management of the species.

Improved management of species of the African Entandrophragma genus, now listed as vulnerable

Because of the quality of their wood and their many traditional uses, species of the Entandrophragma genus are being intensively logged, and this is likely to compromise their survival unless sustainable management is introduced. This study reviews the current status of the five main commercial Entandrophragma species: Entandrophragma angolense, E. congolense (often confused with E. angolense), E. candollei, E. cylindricum and E. utile. We suggest directions for research to improve sustainable management strategies for this genus. The study draws mainly on published scientific data, economic data (production and export statistics) and on relevant laws and regulations, but also on existing management plans and inventory reports. Although these species are reported as vulnerable on the IUCN Red List, knowledge on their management is still patchy. Industrial and artisanal logging is intensive and does not always follow a validated management plan or abide by the minimum rotation period, both of which would help to ensure the renewal of these resources. Managing them to ensure that logging is sustainable in the long term requires management measures to be developed and complied with. Sustainable use has to be based on appropriate management of natural stands and on reforestation and conservation measures. Research studies to be developed should encompass the growth rates of the species in the light of the changing climate, assessments of stocks (timber, biomass and carbon), updates of their spatial distribution, improvements to natural regeneration, reproduction processes and the anatomical and technical properties of each species. All these research topics are necessary to ensure the permanence of these Entandrophragma species.

Total and Merchantable Volume Equations for 25 Commercial Tree Species Grown in Canada and the Northeastern United States

Accurate estimates of tree bole volume are fundamental to sustainable forest management. Total inside and outside bark and merchantable volume equations were developed for 25 major commercial tree species grown in natural stands in eastern and central Canada and the northeastern United States. Data used to develop these equations was collected from 9647 trees sampled from natural stands across the study area. The number of trees sampled varied among species. Jack pine (Pinus banksiana Lamb.) had the most observations (1648 trees) and American basswood (Tilia americana) and red oak (Quercus rubra L.) had the fewest (28 trees each). Two mathematically consistent volume equations (dimensionally compatible and combined variable) were fitted to inside and outside bark and merchantable tree volume data from these tree species. The final volume equation was selected based on fit statistics, predictive accuracy, and logical consistency. Its predictive accuracy was compared with a volume equation previously developed by Honer. Both (total and merchantable) volume equations were fitted using a nonlinear mixed-effects modelling approach. However, random effects were significant for total volumes for only four tree species. A weight (power function) was used to address heteroscedasticity in the data. The modified form of the dimensionally compatible volume equation outperformed the combined variable volume equation in terms of fit statistics and predictive accuracy and was selected as the total inside and outside bark and merchantable volume equations for all tree species. This equation produced logically consistent estimates of total and merchantable volumes and was more accurate than that previously developed by Honer to estimate volumes for most of the tree species used in this study. This new equation can be used to estimate total inside and outside bark and merchantable volumes of major commercial tree species in eastern and central Canada and the northeastern United States.

Effect of nursery substrate on the growth of Pterocarpus erinaceus Poir. seedlings

The high pressures on Pterocarpus erinaceus Poir. severely affect its natural stands in West Africa. The measures taken to reverse this trend are still inefficient due to plantlets production constraints. This study aims to understand the importance of growing substrates on seedlings growth in nursery. Composite soil samples were collected at 20 cm depth from 4 seed trees in 5 different sites in Togo (West Africa). Two batches were made for each site, one of which was sterilized by autoclave and the other has received no treatment. Three growing parameters (length of stem, number of buds and number of leaves) of the plantlets obtained from sterilized seeds were measured during 20 weeks in the nursery. Results show for each site a significantly better growing rate of seedlings on unsterilized substrates, compared to sterilized substrates. At the end of the experiment, plantlets were 8.75 ± 2.32 cm mean height on sterilized substrates when they reach 19.20 ± 5.00 cm on unsterilized substrates. The mean number of buds and leaves per plantlet varies from 2.23 ± 1.71 buds and 3.00 ± 1.86 leaves to 10.73 ± 3.28 buds and 11.09 ± 2.48 leaves at the same date, respectively on sterilized and unsterilized substrates. The low growing rate on sterilized substrates should be linked to the low capacity of plantlets in mobilizing phosphorus, potassium and nitrogen without microorganisms. Negative impacts of sterilization were highlighted on seedlings by necrosis of buds and leaves from the 7th week of growth, demonstrating a positive effect of soil microorganisms on the proper development of the seedlings.

Coniferous plants as potential reservoirs of phytoseiid mites (Parasitiformes: Phytoseiidae) in Poland

Coniferous trees and shrubs growing in natural stands are important reservoirs of naturally-occurring predators belonging to the family Phytoseiidae (Mesostigmata: Phytoseioidea). The fauna of these mites on eight native coniferous species in Poland was surveyed and an exploratory statistical investigation was carried out into mite-conifer associations. The conifers were growing in forests, national parks and nature reserves throughout Poland. A total of 2,540 specimens of phytoseiids belonging to nine species was identified. Four species were new for the Polish fauna, i.e., Typhlodromus (Anthoseius) inopinatus (Wainstein), T. (A.) caucasicus (Abbasova), T. (A.) singularis Chant and Neoseiulus gracilentus (Hirschmann). Among the studied coniferous taxa, Picea abies (L.) H. Karst supported the greatest numbers of both species and individual mites. The highest biodiversity indexes for the phytoseiids were obtained for Taxus baccata L. and Juniperus communis L. Among the phytoseiid species found, T. (T.) tiliae Oudemans occurred on all eight host species surveyed. Typhlodromus (A.) bakeri (Garman) and T. (T.) tiliae were the most dominant species and occurred on conifers with high constancy. Amblyseius andersoni (Chant) co-dominated with them on J. communis and P. abies. New to the knowledge of Phytoseiidae-host plant records were T. (A.) singularis on P. abies, T. (T.) tiliae on Pinus mugo Turra, Pi. cembra L., J. communis and T. baccata, N. gracilentus on J. communis and Pi. mugo, and T. (A.) inopinatus on Abies alba Mill., Larix decidua Mill. and P. abies. Additionally, for Poland, new Phytoseiidae-host plant associations were T. (A.) inopinatus on Pinus sylvestris L., T. (A.) bakeri on J. communis and T. baccata, T. (A.) caucasicus on A. alba, T. baccata and P. abies, and T. (A.) singularis on L. decidua.