Tree Preference and Temporal Activity Patterns for a Native Ant Community in an Urbanized California Woodland

Anthropogenic disturbances, including land use change and exotic species, can alter the diversity and dynamics of ant communities. To examine foraging behavior in an urbanized habitat in northern California, we surveyed the presence of 9 ant species on 876 trees across 4 seasons during both day and night in a 9.5-hectare urbanized oak-exotic woodland. Ants were more likely to be observed on native, evergreen trees, suggesting that native evergreen species may help maintain ant diversity. Species showed clear patterns of temporal partitioning of foraging activity. Ant species varied in their use of native evergreen Quercus agrifolia trees across season and day/night axes. Of the 3 ant species most frequently observed, Camponotus semitestaceus was most active during spring and summer nights, Formica moki was most active during spring and summer days, and Prenolepis imparis was most active during both day and night during fall and winter. Liometopum occidentale was the second most active species during summer day and night, and winter day. Our findings demonstrate that an oak-exotic urban woodland in Northern California was able to maintain a native ant community, and strong temporal partitioning within that community.

Soil Mesofauna Community Changes in Response to the Environmental Gradients of Urbanization in Guangzhou City

There has been a recent increase in interest on how urbanization affects soil fauna communities. However, previous studies primarily focused on some limited land use types or line transects of urban-rural gradients. At family and higher taxonomic levels, we investigated the changes of soil mesofauna communities (abundance, species richness, and community structure) with urbanization intensity along different disturbance features in 47 sites evenly located in downtown Guangzhou and adjacent regions. The 47 research sites were classified into four ecosystem types mainly according to the location (rural/urban), vegetation cover, and management intensity. In turn, the four types with increasing urbanization intensity were rural forest, urban forest, urban woodland, and urban park. Firstly, the role of urban soil property (soil physicochemical characteristic and soil heavy metal content) in regulating soil mesofauna community was investigated. The results showed that soil mesofauna abundance and diversity decreased with increasing soil pH, total nitrogen content (TN), and heavy metal comprehensive index (CPI). Soil Pb decreased soil mesofauna species richness (taxa number) and regulated soil mesofauna community structure. Secondly, we examined the effects of landscape changes on the soil mesofauna community. We found impervious surface (IS) ratio did not predict changes in soil mesofauna abundance, species richness, or community structure. Instead, IS ratio was positively correlated with soil pH, soil TN, and CPI. After excluding sites that belonged to rural forests and urban parks, site area was positively correlated with soil mesofauna abundance. Thirdly, our results revealed significant differences in soil property, landscape trait, and soil mesofauna community among the four ecosystem types. Interestingly, urban forest, the one lightly disturbed by urbanization, but not rural forest, had the highest soil mesofauna abundance. Soil mesofauna abundance in urban woodlands was similar to that in urban parks, which was about half of that in urban forests. Species richness in urban parks was 21% lower than that in rural forests. Our results also showed that urban woodland and urban parks had distinct mesofauna community structures compared to those in rural forests and urban forests. In conclusion, the present study suggested that (1) soil property changes due to urbanization, such as increased pH and heavy metal enrichment in urban soil, decreased soil mesofauna abundance and species richness, changed community structure, and mediated the effect of landscape change on soil mesofauna community; (2) however, soil and landscape changes could not explain the increase of abundance in urban forests, which supported the intermediate disturbance hypothesis.

Mitigation of greenhouse gas emissions from households by urban woodland in Ibagué-Colombia

Trees are essential in the city to capture CO2, and, at the same time, to contribute to the mitigation of climate change. Carbon storage and fixation in aboveground biomass was estimated in the urban woodland of Ibagué with a census from 2013-2016, and a new measurement of 15% on individuals in the 2019-2020 period. The number of trees of the main species required to mitigate emissions of greenhouse gases from households was estimated. Urban woodland captures about 3.81 Gg CO2/year, which represents only 2,3% of the city emissions. The mitigation of 169.2 Gg CO2/year of the city households would be achieved by having between 412,000 and 1.2 million trees of the most dominant species. Efforts based on green infrastructure to compensate urban emissions at municipal level must be coordinated with territory policies at large scales.

Heavy Metals Bioindication Potential of the Common Weeds Senecio vulgaris L., Polygonum aviculare L. and Poa annua L.

In recent years, heavy metals (HMs) levels in soil and vegetation have increased considerably due to traffic pollution. These pollutants can be taken up from the soil through the root system. The ability of plants to accumulate HMs into their tissues can therefore be used to monitor soil pollution. The aim of this study was to test the ruderal species Senecio vulgaris L., Polygonum aviculare L., and Poa annua L., as possible candidates for biomonitoring Cu, Zn, Cd, Cr, Ni and Pb in multiple environments. The soils analyzed in this work came from three different environments (urban, woodland, and ultramafic), and therefore deeply differed for their metal content, texture, pH, and organic matter (OM) content. All urban soils were characterized by high OM content and presence of anthropogenic metals like Pb, Zn, Cd, and Cu. Woodland soils were sandy and characterized by low metal content and low OM content, and ultramafic soils had high Ni and Cr content. This soil variability affected the bioindication properties of the three studied species, leading to the exclusion of most metals (Zn, Cu, Cr, Cd, and Pb) and one species (P. aviculare) due to the lack of linear relations between metal in soil and metal in plants. Senecio vulgaris and Poa annua, conversely, appeared to be good indicators of Ni in all the soils tested. A high linear correlation between total Ni in soil and Ni concentration in P. annua shoots (R2 = 0.78) was found and similar results were achieved for S. vulgaris (R2 = 0.88).

The Impact of Resident Participation on Urban Woodland Quality—A Case Study of Sletten, Denmark

Despite the potential of urban woodlands for recreational use and participatory management, citizens’ perception of urban woodland quality, as well as the impact of citizens’ co-management on urban woodland quality, have not been thoroughly studied to date. The present study investigated how residents in Holstebro, Denmark define urban woodland quality in their neighborhood named Sletten and how they perceive the quality impact of their participation in the management and maintenance of a transition from private gardens to public urban woodland—the so-called co-management zone. Field survey of participation for all housing units with a co-management zone (n = 201) informed strategic selection of residents for individual interviews (n = 16). It was found that social, experiential, functional, and ecological dimensions are all part of residents’ perception of urban woodland quality, whereby maintenance, accessibility, and nature are dominating aspects of these dimensions. While these aspects are already integrated in quality assessment schemes for other types of urban green space, our study revealed the importance of structural and species diversity between and within woodland stands as central for the perceived woodland quality—a quality aspect that distinguishes woodland from other types of urban green space. Participation in the management and maintenance positively influenced the perceived woodland quality. Residents found that their participation in the co-management zone created functional and ecological, physical qualities in the woodland. Moreover, the active participation provided the residents with a range of social and experiential benefits, many of which they themselves argue that they would have missed out on if they were only allowed to use the woodland “passively”. These findings suggest a large—but also largely untapped—potential of participatory urban woodland management to contribute physical qualities to urban woodlands and benefits to its users.