Plants enhancing urban pollinators: Nectar rather than pollen attracts pollinators of Cotoneaster species

Urban green areas can play a crucial role in establishing spaces that are valuable for pollinators. However, to help ‘pollinator-friendly’ management of urban areas, complete information on the quantity and quality of available floral reward is needed. In this paper, the nectar and pollen of six Cotoneaster species (Rosaceae) were investigated in a two-year experiment established in Lublin city, SE Poland. In temperate climate, Cotoneaster species can ensure nectar and pollen in the full spring period (May/early June) or in early summer (June). A single species can support pollinators on average for 22.9 days. Flowers of Cotoneaster species produce high quantities of nectar (2.27–9.48 mg per flower) and low amounts of pollen (0.11–0.33 mg per flower). On average, the total sugar yield in Cotoneaster species was 11.5 g/m² (2.3–22.2 g/m²), whereas the total pollen yield was 1.3 g/m² (0.8–2.8 g/m²). Due to the high potential for total sugar yield, C. macrophyllus, C. lucidus, and C. horizontalis should be recommended to optimize the management of food resources in urban areas. Honeybee was the main insect visitor (70.1 % of the total number of visitors); therefore, Cotoneaster species can be considered valuable for urban beekeepers. However, conservation schemes for bumblebees (21.3 % of the total number of visitors) might also benefit from arrangements with these shrubs. Nevertheless, considering Cotoneaster species in conservation protocols, good-yielding pollen plants should be introduced to compensate for insufficient nutrient intake from pollen in spring.     

A nectar oasis for urban Glossophaginae bats: Temporal resource dynamics of the chiropterophilous Crescentia cujete (Bignoniaceae)

Pollinator-friendly plants are often a necessary component of the management of urban ecosystem that aim to reduce the impact of the artificial urban matrix on natural pollinator populations. Nectarivorous bats are neglected components of the urban pollinator community and there is a paucity of assessments on pollinator-friendly plants that may provide urban bats with reliable, year-long resources. Crescentia cujete is a bat-pollinated Bignoniaceae with very distinctive chiropterophilous features that is often used as an ornamental species in tropical urban areas worldwide. Its flowers are large and produce copious amounts of nectar, which accumulates in the flower’s storage-shaped flowers. Thus, the species is a potential bat-friendly urban plant. We assessed the species’ year-round flower emission and nightly nectar production dynamics in a green area in northeastern Brazil, and described the behavior of its floral visitors. C. cujete showed a steady, year-round flowering pattern, with no significant seasonality. Its flowers secreted copious amounts of diluted nectar and were visited exclusively by the Pallas long-tongued bat Glossophaga soricina throughout the night at high visiting frequencies, delivering successive visits to individual flowers spaced by short intervals. Our results suggest overexploitation of floral resources from C. cujete by urban bats. Moreover, its continuous flowering and copious nectar production may become a reliable resource in an artificial environment generally lacking bat-pollinated plants, thus mitigating the effects of food shortage for urban nectar bats.     

Spatiotemporal distribution of floral resources in a Brazilian city: Implications for the maintenance of pollinators,especially bees

Cities provide resources for the animals that live in them or their surroundings. There has been an increase in the number of ecological studies in urban areas, including interactions between plants and bees. Bees are pollinators that provide a vital ecosystem service to crops and wild plants. We assessed plant community structure in the campus of Universidade de São Paulo in Ribeirão Preto, Brazil, included in the neotropical Atlantic Forest biome, focusing on floristic composition, pollination syndromes, flowering phenology, and spatiotemporal distribution of floral resources for bees. Currently, the city is surrounded by sugar cane plantations. Once a month, from April 2011 to March 2012, we sampled plant species and individuals in bloom in an area with 500 m radius from the bee-rearing facilities of Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP), totaling 78 hectares. We sampled 289 plant species of 73 families; Leguminosae was the richest family. Plants pollinated by bees predominated (67%), followed by plants pollinated by hummingbirds (18%). Melittophilous species flowered throughout the year and, hence, food availability for bees was continuous. The flowering of plant individuals that provided pollen, nectar, and floral oil was seasonal in all vegetation (except for nectar in shrubs), with peaks in resource availability in the transition from the dry to the rainy season, and also in the rainy season. Our results show that the campus is able to maintain bee populations amid a monoculture matrix, acting as a refuge. In addition, it provides a list of several attractive native plants to different pollinator groups, coupled with a phenogram, that can be used in the design and planning of urban areas.     

Pollen meta-barcoding reveals different community structures of foraged plants by honeybees (Apis mellifera L.) along space-time gradient in Japan

The availability of pollen in urban-rural landscapes is an essential factor that influences the population dynamics of insect pollinators. The amount and diversity of pollen play a pivotal role in the foraging ecology of pollinators for their growth and health, but investigations on the spatio-temporal patterns of foraged plants remain rare, especially in cities as neo - ecosystems. Here, we explored the temporal foraging habits of a highly pollinator (Apis mellifera L.) in Tokyo, including different landscape classes from rural to urban areas. Mixed-pollen samples in each month and each location (N = 17) were analysed using DNA meta-barcoding to identify plants visited by honeybees. The results showed that the landscape class (rural, suburban and urban areas) explains spatial variations in pollen source-plant composition foraged by honeybees, but not in taxa richness. Furthermore, pollen diversity and pollen source-plant composition showed a strong seasonal dependence. A higher plant richness and foraged woody taxa was found to occur in spring, which was mainly dominated by the genera Prunus and Acer. In summer and autumn, the genera Trifolium and Plantago of the herbaceous stratum were the most visited plants. The Fabaceae, Rosaceae, Brassicaceae, Plantaginaceae, and Onagraceae plant families were the most frequently observed in all combined samples. The present study contributes to a deeper understanding of the foraging ecology of A. mellifera colonies across urban-rural gradient surrounding mega-cities such as Tokyo.     

Non-native plants and illegitimate interactions are highly relevant for supporting hummingbird pollinators in the urban environment

Urbanization leads to the restructuring of plant-animal interactions due to environmental changes and introduction of non-native species that become part of local ecological processes. The conservation of pollinators in urban areas has received increasing attention. However, detailed quantification of available floral resources and their use by pollinators are rarely conducted. Here, we characterized the interaction network between hummingbirds and native and non-native plants, the behavior of resource use by pollinators and the temporal availability of nectar resources in an extensive urban green area from Brazil. We found that more than half of the interactions between hummingbirds and plants were illegitimate, which do not constitute potential pollination. The interaction network was generalized, indicating low level of niche partitioning, which is usual for urban environments. Inclusion of non-pollination interactions increased specialization. Although native and non-native plants provide a similar amount of nectar when considering each plant species for a given month, the latter contributed most to the total nectar availability owed to their higher abundance and longer flowering phenologies. Importantly, non-native plants provided resources when native flowers were scarce. Our results show how non-native plants may sometimes have relevant contributions for maintenance of pollinators in cities throughout the year, supporting them during periods of resource shortage. At the same time, urban pollinator-plant communities may be characterized by high prevalence of illegitimate interactions, which highlights the opportunistic use of resources by animals. In conclusion, our study suggests that biodiversity-friendly urban planning should consider the relevant role played by non-native species and that pollinator support may require different types of interactions with flowers.     

Effects of vegetation structure and environmental characteristics on pollinator diversity in urban green spaces

With accelerating urbanization, insect pollinators in urban ecosystems face challenges such as reduced pollen sources, habitat fragmentation, and damage to the nesting environment. Urban green spaces (UGS) are essential for the stability of pollinator communities. However, little is known about the relationship between vertical layer heterogeneity and horizontal layer complexity of vegetation structure in UGS and pollinator communities. The present study aimed to assess how vegetation structure and environmental characteristics shape the insect pollinator community in UGS. To this end, this study was conducted with seven typical vegetation types which were selected according to the biotope mapping classification system (BMCS) in the ring parks around Hefei City, in Anhui province, China. A total of 11,401 pollinators belonging to 6 orders and 34 families were identified during the eight-month survey. Among the seven habitats under the BMCS, mainly successional short-cut shrub and partly open green space, trees two- or multi-layered broad-leaved mixed forest and partly closed green space, and mainly successional tall grass and partly open green space were identified as high-quality insect pollinator habitats. According to the results of the generalized linear regression, the explanatory power of the four best-fitting generalised linear models is relatively high (over 77%). In four optimal models, the effect of vegetation structure on pollinator community was greater than that of environmental characteristics. The redundancy discriminant analysis showed that the flowering abundance of nectar plants, herb richness, and shrub coverage rate were the three most important factors influencing insect pollinator communities, with a cumulative explanatory power of up to 78.8%. Pollinator abundance was positively influenced by spontaneous herbs and low-intensity management. However, high-intensity management, low diversity of plants, low nectar plant richness, ignoring seasonal nectar plant configuration, and dense tree distribution could limit pollinator reproduction and population growth. These results reflect the status of insect pollinator community in UGS in Hefei city and present a possible direction for improving urban green habitats and plant configurations.     

Pollination of urban meadows – Plant reproductive success and urban-related factors influencing frequency of pollinators visits

Pollination is a key ecological service for human food security and the reproduction of the majority of flowering plants. This plant-animal interaction is crucial in both wild and urban habitats, however, increasing urbanization and change in land use alter these interactions. The concerns regarding pollination have led to numerous efforts aimed at improving the quality of wildlife in cities, however, understanding the importance of these activities warrants further research. In Warsaw, the Polish capital, we analyzed the influence of urban-related factors such as floral resource richness, the proportion of green areas in the proximity of foraging sites, air pollution or temperature on plant-pollinator interaction in 14 meadows. We also analyzed the reproductive success and the heterospecific pollen transfer in the case of plants growing in the meadows. Our study revealed that the frequency of visits to flowers was related to city-related factors, but the reaction varied among different groups of pollinators. For example, bumblebees were negatively influenced by higher air pollution, while the rest of the flower visitors were not, Syrphidae flies were more frequent flower visitors when the proportion of green area was higher in the buffer of 150 m, while we did not observe this tendency in other groups of flower visitors. Plants growing in Warsaw meadows were frequently visited and effectively pollinated - urban pollinator assemblages seem to provide sufficient pollination services to plants growing in the city. Species-rich communities were not a threat to pollination; we found mostly conspecific pollen grains on the stigmas of the studied plant species. The results of our study show that species-rich communities make a valuable contribution to pollinator conservation. The conservation activities, however, should be adjusted to the target group of pollinators, since different groups of flower visitors respond differently to urban-related factors studied.     

Urban epiphytes: Bromeliad diversity in a green cover gradient across a Neotropical streetscape

The Neotropical region is undergoing high levels of urban expansion and harbors the greatest diversity of vascular epiphytes globally. In cities, it could be expected that the density of woody vegetation positively predicts epiphyte communities by providing substrate, resources for pollinators, and buffering microclimatic conditions. However, there is a dearth of knowledge regarding how urbanization intensity affects the diversity of vascular epiphytes. In this study, we assessed the relationship between a woody cover gradient and bromeliad species richness and community composition across a streetscape of the Neotropical city of Xalapa (Mexico). We recorded bromeliads in nine street segments and one peri-urban green space. These sites represent a gradient of woody cover ranging from 10.5% to ∼87% in a 100 m buffer, and 100% in the peri-urban green space. We recorded 824 individuals of 14 species (all from the Tillandsioideae subfamily). The most abundant species was Tillandsia recurvata and the most frequent ones were T. juncea and T. schiedeana. Results show that bromeliad species richness was positively related to the woody cover, as expected. Interestingly, community composition did not associate with the percentage of woody cover. These results suggest that additional factors such as microclimatic conditions and seed availability and/or dispersal may be key modulators on the establishment of bromeliad species. Nevertheless, wooded streets do show potential for harboring diverse bromeliad communities.     

Eignen sich die Mauerbienen Osmia bicornis und Osmia cornuta als Best?uber im Obstbau?

Mason bees have been successfully managed as orchard pollinators in Japan and USA for many decades. Recently, the European species Osmia bicornis (L.) and Osmia cornuta (Latr.) attract more interest as pollinators in fruit orchards in Germany. Several studies indicate the potential of these mason bees as pollinators of pome and stone fruit. Here, we investigated the composition of the pollen loads in the brood cells of these two mason bees in fruit orchards different in habitat characteristics. At eight study sites, trap nests and cocoons of O. bicornis and O. cornuta were installed. During fruit tree blossom, pollen was sampled every two weeks and the percentage of Rosaceae pollen was identified. Landscape characteristics were assessed in a radius of 250 m from the trap nests. At all eight study sites, O. bicornis and O. cornuta collected pollen of Rosaceae. The percentage of Rosaceae pollen in the samples and the local habitat quality of the foraging sites were negatively correlated. In fruit orchards with a low diversity of suitable foraging habitats, brood cells contained a relatively high percentage of fruit tree pollen. These results indicate the potential of O. bicornis and O. cornuta as efficient pollinators in intensively managed fruit orchards. However, intensive fruit orchards appear less suitable as habitats for these mason bees to establish an endogenous pollinator population. Hence, the introduction and management of mason bees in orchards will improve pollination.     

Planning for the conservation and sustainable use of urban forestry in Addis Ababa,Ethiopia

The planning and management of urban forest has become increasingly important as a focus of urban environmental management. The objectives of this study were to analyze the landuse/land cover and to map functional zones of the urban forest in the upper catchment area of Addis Ababa. This study identifies five landuse/land cover types: (i) Eucalyptus–Juniperus dominated forest, (ii) mixed native forest, (iii) built-up areas, (iv) Eucalyptus plantation (v) crop/grazing lands. The vegetation analysis shows 44 woody plant species representing 31 families, out of which 13 tree species, 29 shrubs and two species of lianas. The woody species diversity was 1.35 with the species richness and evenness of 44 and 0.80, respectively. This indicates that the forest has poor species diversity which is attributed to high anthropogenic pressure and monoculture plantation development strategies in the last decades. The density of plants ranged from 25 for Olea europea to 825 individuals per hectare for Eucalyptus globules from the tree layers and from 50 for Dombeya torrida and Erica arborea to 900 individuals per hectare for Myrsine africana from shrub layers. Based on importance value index (IVI), Eucalyptus globulus and Juniperus procera showed the highest IVI of 96.37 and 54.80, respectively as compared to other species. The forest structure showed higher contagious distribution where out of the recorded 44 species, 37 species showed contagious distribution. The result also showed poor regeneration potential in all studied forest layers. Based on the landuse/cover analysis, the phytosociological study and field observation, this study recommends six urban forest zoning. These include: (i) conservation zone, (ii) recreation zone, (iii) production zone, (iv) agroforestry zone, (v) reforestation zone, (vi) buffer zone between the green area and the built-up environment. The green area in the upper catchment has no definite boundaries and needs re-demarcation activities.     

Bird-flower interactions in an urban area: Ceiba pubiflora provides nectar and promotes biodiversity in the city

Urbanization has negative effects on plant-animal interactions by reducing plant richness and increasing resource limitations. However, it is possible to replant these areas, and plant species can be selected based on the resources they provide, as well as their relationships with animals. I observed several trees of Ceiba pubiflora (Malvaceae, Bombacoideae) to identify the bird species interacting with their flowers in an urban area. This plant may be especially important, as it blossoms during the dry season, when the overall flower availability in the study area is low. It may also be important during a short period of decline in the fleshy fruit supply. Even though C. pubiflora was growing in the city and had a low volume of nectar accumulating in its flowers (mean of 1.73 μl; SD = 1.39 μl), it attracted a variety of birds (25 species belonging to six families), some of which are usually regarded as forest dependent. Nectarivorous birds from the family Trochilidae (hummingbirds, n = 12 species) had the highest percentage of visits (64.08%), especially during periods of relatively high nectar sugar concentration and calorie availability (c. 18% and 1.5 cal., respectively). Hummingbirds primarily acted as nectar thieves but also sometimes as potential flower pollinators. In contrast, several nonnectarivorous birds (frugivore-granivores, frugivore-insectivores and omnivores) acted only as nectar robbers or flower predators. Ceiba pubiflora flowers appear to be an important source of energy for birds in the urban area. The data of this study show that C. pubiflora has utility as management tool to promote and conserve biodiversity in cities.     

Floral biology,pollination ecology and seed production of the ornamental plant Salvia splendens Sello

Summary

In this paper, the floral biology and pollination ecology of Salvia splendens are described. All flower characteristics (red corolla, large tubular flowers with abundant but dilute nectar) indicate that S. splendens is adapted to hummingbird pollination. Honeybees, however, were also found to be good pollinators of this plant. Apis mellifera was equally effective in pollinating S. splendens as hand pollination and open pollination, resulting in a 300% increase in seed set compared with bagged control plants. The much smaller stingless bee Tetragonisca angustula was not an effective pollinator of these flowers since during visitation its body failed to touch the stigma. Although pollination seemed not to be the only limiting factor in seed production, external pollinators enhance seed production in S. splendens, and Apis mellifera is an effective, commercially available pollination agent of this economically important ornamental plant.     

Growing on the street: Multilevel correlates of street tree growth in Montreal

Tree planting has been favoured in many North American cities, including Montreal which aims to increase its canopy from 20% to 25% in 2025. However, the mortality rate of street trees is especially high in the first few years after planting. Studies have shown that variables that are intrinsic to the tree and those related to its location, the urban form and the socio-demographic characteristics of the surrounding environment are significantly associated either with trees’ survival rate or with vegetation cover. In this research we examine variables that have statistical associations with tree growth, which is the diameter at breast height divided by the number of years on the ground, for approximately 28,000 street trees in Montreal. Independent variables were nested into three spatial scales: the tree (species and physical variables), the street section (urban form variables), and the census tract (socio-demographic variables). Multilevel models reveal that 65.51% of the growth variance is potentially explained by the species and planting physical conditions such as the east and north sides (positive associations with the growth), signage as an obstruction (negative association). 28.54% of the grow variance is potentially explained by the urban form, in our case building age (convex relationship with the growth), mixed zoning (negatively) and residential zoning (positively). At the neighbourhood level, although none of our variables is significant, 6.95% of the growth variance is be potentially explained by other missing variables. New planting programs should hence consider the urban form in order to improve tree growth.     

Pollination studies in large cardamom (Amomum subulatum Roxb.) of Sikkim Himalayan region of India

Pollination studies in large cardamom were carried out at the research farm of ICAR Sikkim Centre, Gangtok, Sikkim, India during 2009–2010 to assess the effectiveness and efficiency of pollinators. Polleniferous flowers (65,890 ± 11,346.5 pollen/anther) of large cardamom produce spherical, large (108.64 μm × 96.32 μm) and echinate pollen with high pollen/ovule ratio (585.2 ± 134.8). Native bumblebee (Bombus braviceps Smith.), a nectar forager, was identified as the most effective pollinator in terms of pollination potential index score (0.88), pollen removal (55.39%) and deposition rate (4.5%), pollination efficiency and pollen delivery mechanism whereas honey bee acted as a pollen robber. Flowers appeared to be generalized; however, functional specialization was exhibited indicating that only bumblebee is adaptable for pollination moreover, pollination mechanism was an indicative of “pollination syndrome”.     

Spatiotemporal availability of pollinator attractive trees in a tropical streetscape: unequal distribution for pollinators and people

Street trees integrate the urban green infrastructure and are important elements for the maintenance of biodiversity, including pollinators. Thus, assessments of the spatiotemporal distribution and composition of these trees can subsidize strategies of conservation for different groups of pollinators in the cities. Here, we evaluated the spatiotemporal distribution of trees attractive to pollinators across the streetscape of a large Brazilian metropolis with more than 2.5 million inhabitants. We used the georeferenced data of ca. 300,000 woody plant individuals cataloged across the streetscape. These plants were characterized according to their geographical origin, flowering season, and the floral visitor groups that are attracted based on a literature survey. We also tested the “luxury effect” hypothesis on the resource availability to pollinators by evaluating the relationship between the average family income of the population and the richness and abundance of trees. We found that the streetscape was characterized by the dominance of a few tree species, with a balanced representation of both native and non-native species. Bees were the most favored group (94.86%) while bats (1.43%) and moths (1.73%) were the least. The potential supply of resources was homogeneous across dry and wet seasons, but the density of trees was reduced in most of the landscape. We found a strong luxury effect since tree richness and abundance were positively related to regions with higher average family income. Our study highlights the need for better planning and management practices of urban green areas to support pollinators more uniformly across streetscapes. This will allow the benefits provided by pollinators to be more evenly shared among residents of urban landscapes.     

Intersubgeneric cross in Nymphaea spp. L. to develop a blue hardy waterlily

Five waterlily cultivars, with good pod setting and completely formed flowers, from the subgenus Nymphaea (hardy waterlily) were used as pod (female) parent. Waterlilies from subgenera Anecphya (2 entities) and Brachyceras (20 entities), specifically the blue-flowered ones, were used as pollen (male) parent for transferring blue-flowered characteristic to the hardy waterlily. Hybridization of subgenus Nymphaea with subgenus Anecphya was unsuccessful. A successful crossing was obtained between the subgenera Nymphaea and Brachyceras, yielding one pod with 244 seeds, from which only 39 seeds germinated and yielded 20 good intersubgeneric hybrid plants. The characteristics of the hybrids were categorized by their flower colors into two groups, a pink-flowered group with 17 hybrids and a blue-flowered group with 3 hybrids. In the blue-flowered group, there was a prominent one with beautiful blue-purple flower, which was determined by PCR-RFLP markers to be a hybrid between Nymphaea and Brachyceras subgenera, as well as inherited some plant characteristics, for example, ovary carpel, leaf (pad), rootstock, position of flower at flowering from the parent. The blue-purple flowered hybrid had important characteristics inherited from the hardy waterlily (subgenus Nymphaea); therefore, the hybrid has been named Nymphaea ‘Siam Blue Hardy’ to honor the birth place and its distinct flower color.     

苦苣苔科植物传粉生物学研究进展

根据苦苣苔科植物的地域分布,可将其分为新热带苦苣苔科植物和旧热带苦苣苔科植物。新热带苦苣苔科植物传粉媒介主要为脊椎动物,旧热带苦苣苔科植物的传粉媒介主要为无脊椎动物。据报道,蜂类、蜂鸟、蝙蝠等可为苦苣苔科植物传粉;不同的传粉媒介选择并适应不同的传粉特征,尤其是花部特征,其中蜜腺花蜜含量及其组成与传粉者的行为特征密切相关。而且,有的苦苣苔科植物具有雄蕊先熟或雌蕊先熟、镜像花柱等特殊现象,从而有效地避免自花传粉。但是,在恶劣环境下,为了能维持种的生存与发展,苦苣苔科的某些植物也会进行自花传粉。     

Is it sufficient? Assessment of two sampling methods for urban plant species richness investigations

Determining adequate sample size (ASS) and minimum plot size (MPS) are two fundamental issues in urban vegetation investigations. To estimate the ASS and MPS of urban plants, we introduced sampling completeness to the MPS calculation based on 54 samples in the urban area of Chongqing, China. Then, we examined the performance of the species-area curve method and CV_Jack1 (coefficient of variation (CV) for the first-order jackknife estimator (Jack1)) curve extrapolation method. We also tested the effectiveness and error distribution of extrapolating the ASS from CV_Jack1 curves using 180 samples from the urban area of Chongqing, China, and 222 samples from the urban area of Xiamen, China. The results of the urban plant analyses showed that (1) the constructed species-area accumulation curves fit a logistic function (R² > 0.990); (2) the MPS increased with sampling completeness, whereas unrecorded species exhibited the opposite trend; (3) the CV_Jack1 curves fit the allometric1 function (R² > 0.960) but might fail to reach a CV value of 0.05 for the calculation of ASS if the sample size was too small; and (4) the relative error values were below 5% when the error curves of extrapolation (by CV_Jack1 curve) approached a horizontal asymptote. The species-area accumulation curve with sampling completeness and the CV_Jack1 curve extrapolation method were promising approaches for determining the MPS and ASS of urban plants. The results and methods in this study provide a reference for determining the appropriate plot size and sample size for urban plant species richness investigations.     

How landscape,pollen intake and pollen quality affect colony growth in <Emphasis Type="Italic">Bombus terrestris</Emphasis>

Context

Abundance and diversity of bumblebees have been declining over the past decades. To successfully conserve bumblebee populations, we need to understand how landscape characteristics affect the quantity and quality of floral resources collected by colonies and subsequently colony performance.

Objectives

We therefore investigated how amount and composition of pollen collected by buff-tailed bumblebee Bombus terrestris colonies was affected by the surrounding landscape (i.e. the proportion of forest, urban, semi-natural habitats) and how they were related to colony growth.

Methods

Thirty B. terrestris colonies were placed at grassland sites differing in surrounding landscape. Colonies were established in spring when availability of flowering plants was highest, and their weight gain was monitored for 1 month. We additionally recorded the quantity and compared plant taxonomic composition and nutritional quality (i.e. amino acid composition) of pollen stored.

Results

Bumblebee colonies varied little in the pollen spectra collected despite differences in surrounding landscape composition. They collected on average 80 % of pollen from woody plants, with 34 % belonging to the genus Acer. Early colony growth positively correlated with total amount of woody pollen and protein collected and decreased with increasing proportions of semi-natural habitats and total amino acid concentrations.

Conclusions

Our results suggest that woody plant species represent highly important pollen sources for the generalist forager B. terrestris early in the season. We further show that colony growth of B. terrestris is predominantly affected by the quantity, not quality, of forage, indicating that several abundant plant species flowering throughout the bumblebees’ foraging season may cover the colonies’ nutritional needs.

     

The effects of land tenure and land use on the urban forest structure and composition of Melbourne

The urban forest provides valuable ecosystem services for enhancing human well-being. Its structure and composition determine the quantity and quality of these services. There has been little research on the heterogeneity in structure and composition of urban forests in the Australasian region, especially in the centre of a highly dynamic and rapidly urbanizing city. This paper quantifies the structure and the composition of the urban forest of Melbourne, Australia's city centre. The effects of land tenure and land use on the heterogeneity of canopy cover, tree density and canopy size were explored. Species and family composition by land use, land ownership and street type were also analysed using the Shannon–Wiener and Jaccard similarity indices. Most of the canopy cover in the city centre is located on public land and is unevenly distributed across the municipality. The mean canopy cover (12.3%) is similar to that found for whole city studies around the world, which often include peri-urban forests. Similarly to other cities, structure varied across different land uses, and tree size, density and cover varied with land tenure and street type. The diversity index shows that the urban forest is rich in species (H′ = 2.9) and is dominated by native species. Improving the distribution, and increasing tree cover and variety of species will result in a more resilient urban centre, able to provide multiple ecosystem services to their residents and its large population of visitors and workers. The study of the urban centre provides further understanding of compact city morphologies, and allows inter-city comparison independent of the size.