Urban Forest Sites Research Articles

The economic situation and ways to solve the environmental problems in the city of Ust-Kut

<p>The Ust-Kutsky district and its center, the Ust-Kut city, have become the fastest growing in the Irkutsk region of Russia in the last decade. Ust-Kut is a very important settlement for the economic development of the northern territories of the Irkutsk region and the southern territories of the Republic of Sakha (Yakutia). The city is a key transport hub, where various types of transport routes converge: railway, aviation, automobile, river, and product pipeline. There are deposits of various minerals near Ust-Kut. The timber mining and timber-processing industries are represented here as much as possible. On the other hand, Ust-Kut is one of the ten most air-polluted cities in the Irkutsk region. Most of the air pollution consists of substances formed as a result of fuel combustion. The unfavorable air regime of the city is influenced by climatic conditions: relatively weak winds and temperature inversions in winter. The oil and gas deposits located nearby may help solve the problem of air pollution by gasification of Ust-Kut. In addition, water and soil pollution have been noted in the city due to technological problems of wastewater disposal, garbage collection, and recycling, as well as certain types of industrial waste processing. Therefore, the main task of the sustainable development of the city is to solve its environmental problems. Ust-Kut's environmental problems are solved at the expense of financial resources from government programs, which are not sufficient. But the tax on mining is completely federal, as these funds do not remain in the territory. Through this research, we have searched for ways to achieve a balance between economic development and environmental well-being in Ust-Kut. Specifically, we have explored additional types of economic activities that are safe for nature and public health. For Ust-Kut, located in the north of Eastern Siberia, it is important to increase the area of green spaces within the central part of the city. The development of a system of parks and squares involves their improvement and the formation of a connection into a single natural framework through linear landscaping objects and connections with urban forest sites. The use of sanitary protection zones around enterprises that emit into the environment will contribute to the formation of a comfortable environment and expand landscaping opportunities.</p>

Branching Songs

In cities, trees are seen predominantly as entities that beautify streets, parks and gardens. Often they’re regarded as obstacles to urban development, where their importance to ecosystem health plays a secondary role to economic growth. How can multispecies art offer new perspectives on trees and their crucial contributions to urban life? Branching Songs is a project with old trees in the Vancouver area, including the ‘1308 Trees’, urban forest sites where trees are being cleared for the Transmountain Pipeline expansion. The intention is to bear witness to trees who are supporting the well-being of human and nonhuman life. The project combines new technologies, such as 360° photography and video, ambisonic and geophonic sound recording, biomidi data, and contact mic recording, with approaches from acoustic ecology, multispecies creativity, and performance. The Branching Songs team produced methods for working collaboratively with trees and composed a collection of soundscapes and accompanying 360° photos and videos. The soundscapes present the complex biophony and anthropophony of each site, weaving in soundings from electromagnetic fields produced by the trees and our touch interactions with the tree bodies. The touch gestures are improvisational, responding to the emergent sounds heard on site, and the specific features of the participating tree. Multiple microphones allow us to listen to varied perspectives refracted across the tree body. Our video article includes an introduction to the project, the methods we developed, two soundscape compositions and accompanying visuals with the trees in the collaboration.@font-face{font-family:"Cambria Math";panose-1:2 4 5 3 5 4 6 3 2 4;mso-font-charset:0;mso-generic-font-family:roman;mso-font-pitch:variable;mso-font-signature:-536870145 1107305727 0 0 415 0;}@font-face{font-family:"Helvetica Neue";panose-1:2 0 5 3 0 0 0 2 0 4;mso-font-charset:0;mso-generic-font-family:auto;mso-font-pitch:variable;mso-font-signature:-452984065 1342208475 16 0 1 0;}p.MsoNormal, li.MsoNormal, div.MsoNormal{mso-style-unhide:no;mso-style-qformat:yes;mso-style-parent:"";margin:0in;mso-pagination:widow-orphan;font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-font-family:"Times New Roman";}.MsoChpDefault{mso-style-type:export-only;mso-default-props:yes;font-family:"Calibri",sans-serif;mso-ascii-font-family:Calibri;mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-font-family:Calibri;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";mso-bidi-theme-font:minor-bidi;}div.WordSection1{page:WordSection1;}

The Effect of Urban Green Spaces on Air Pollution Reduction: A Case of Ahmedabad

Ahmedabad city struggles with one of the highest ambient air pollution levels in India. To reduce the air pollutants, urban green spaces can be considered one of the best options. In the study, few physical variables, like plant stature and morphology, are considered. This paper covers the aspect of vegetation for analysing pollution mitigation. Four Urban Forest (UF) sites from four different zones, differentiated by the land use of each site, of the city of Ahmedabad have been selected, Physical variables of each of these Urban Forest sites were collected. Consequently, an air monitoring station was selected from within 4 km radius of these sites. The selected urban forests were introduced in 2019-20. Pollutant concentration data from before UF and after UF (2016-2021) of each site was extracted from all the stations. This data was then compared with the physical variables of UF to determine the AQI change in the area throughout the years. The findings showed improved the concentration of pollutant in each of the 4 sites. Factors like number of trees and tree species in each site played an important role in pollutant reduction. To understand the role of urban forests, NDVI analysis was conducted of the sites.

Thermal Regulation of Coastal Urban Forest Based on ENVI-Met Model—A Case Study in Qinhuangdao, China

Urban forests can improve human comfort by improving the near-surface microclimate. Exploring the microclimate characteristics of urban forests and their impact on human comfort is particularly important to improve the urban thermal environment through scientific urban forest design. Since most previous studies were conducted under typical inland urban climates and little is known about the thermal regulation services of coastal urban forests, this study field measured the thermal surface radiation temperature of 16 open spaces in the urban forest site in Qinhuangdao. Then the ENVI-met software was used to simulate and analyze the microclimate characteristics before and after the park’s building-up, and compare the differences in the human comfort index in different scenarios. Results indicated that: (1) Vegetation have a significant cooling effect on surrounding environment. The farther away from vegetation area, the higher the average surface temperature. (2) Water bodies have the best cooling and humidifying effect on the 9–18 m surrounding environment with the best human comfort index. (3) In summer, air temperature in park decreased by 0.4~1.4 °C, and the relative humidity increased by 0.07~2.81%. (4) After the park’s built-up, the average human comfort index was optimized by 0.02~1.87. Arranging the leisure open space around the water bodies and forest edge space of the deciduous broad-leaved forest could improve human comfort. This research is expected to provide a scientific basis and planning inspiration for the construction of coastal urban forests in the same latitude area.

Economic Value of Recreation as an Ecosystem Service in Ayer Keroh Recreational Forest, Malaysia

Economic values of various ecosystem services of recreational forests are not well understood in many countries, including Malaysia. Policymakers and resource managers with a lack of such information may make inappropriate decisions to manage forest resources. To address the information problem, this study used data and estimated the economic value of recreation as a cultural ecosystem service of the Ayer Keroh Recreational Forest (AKRF) in Malaysia using the Travel Cost Method (TCM). The study estimated an economic value of USD 20,346/ha/year for cultural services, including recreation. These findings provide some useful information that might be needed for those involved in planning and management for the development of urban forest sites, especially in AKRF.

Hoverflies (Diptera: Syrphidae) as biodiversity indicators for assessing urban forest habitats

Urban and peri-urban forests are important habitats for maintaining biodiversity in cities. In this paper, we report a method for using hoverflies as biodiversity indicators in urban forest habitats. As a case study, forest habitats in three peri-urban and urban forests were assessed and compared to rural forests in Slovenia. Rožnik (Ljubljana) was chosen as the urban forest site, Mestni log (Ljubljana) and Brdo (Kranj) were chosen as the peri-urban sites, and eight sites were chosen in rural forests in different ecoregions in Slovenia. Forest hoverfly species richness and the species composition of different biological traits were compared between the peri-urban forests, urban forest and rural forest sites. In addition, species richness was assessed for changes in response to weather conditions between years. The number of species with the investigated traits in the urban and peri-urban forests was within the range of the number of species observed in the rural forests. The number of saproxylic species was higher in the urban forest but lower in the peri-urban forests compared to the rural forests. The proportions of species with different feeding modes and different development times were similar between the peri-urban, urban and rural forests. The proportions of species with development times of less than 2 months or more than 1 year and of predatory species were similar in the urban and peri-urban forests but higher in the rural forests. The species composition of the other biological traits differed between the peri-urban, urban and rural forests. Species richness and abundance displayed large differences in phenological patterns between 2012 and 2013; these differences are related to differences in the minimum temperature for these years. The results are discussed in relation to forest management in urban forests, the usefulness of hoverflies as a biodiversity indicator and possible extrapolation to other species groups.

Variation in Urban Forest Regulation of Air Particulate Matter Concentration

Urban forest was vital to adjusting Air Particulate Matter Concentration (APMC). The purpose of this study was designed to provide a more detailed analysis of the urban forest long-time scales effect on APMC. The paper assessed effect of forests (urban greening) on APMC in an urban environment, where an urban green center (nearly 2 km2) and a nearby (5 km away) bare-ground site (at a road intersection) in Yuhua District of Changsha, China, were chosen to delve into daily, seasonal, and annual variation of APMC in an urban forest and a non-forested site respectively. It was found that: (1) on a daily basis, APMC in both the urban forest and the non-forested site was high in the morning and evening, but low at noon, demonstrating a “two-peak-one-trough” or V-shaped pattern. Additionally, APMC in the morning was higher than evening. (2) in terms of season, APMC was high in spring and winter, but low in summer and fall. (3) the annual change of the APMC showed a “bimodal” annual trend in urban forest and non-forested site, with a peak concentration in the urban forest coming later than the non-forested site. (4) temperature and average wind speed composed main factors affecting APMC in Changsha’s ecotope. The paper characterized the change pattern in APMC in urban environment (forested and non-forested), suggested appropriate recreational periods in the urban forest, and gave insight in planning and construction of urban greening projects.

Traces of urban forest in temperature and CO<sub>2</sub> signals in monsoon East Asia

Abstract. Cities represent a key space for a sustainable society in a changing environment, and our society is steadily embracing urban green space for its role in mitigating heat waves and anthropogenic CO2 emissions. This study reports 2 years of surface fluxes of energy and CO2 in an artificially constructed urban forest measured by the eddy covariance method to examine the impact of urban forests on air temperature and net CO2 exchange. The urban forest site shows typical seasonal patterns of forest canopies with the seasonal march of the East Asian summer monsoon. This study shows that the urban forest reduces both the warming trend and urban heat island intensity compared to the adjacent high-rise urban areas and that photosynthetic carbon uptake is large despite relatively small tree density and leaf area index. During the significant drought period in the second year, gross primary production and evapotranspiration decreased, but their reduction was not as significant as those in natural forest canopies. We speculate that forest management practices, such as artificial irrigation and fertilization, enhance vegetation activity. Further analysis reveals that ecosystem respiration in urban forests is more pronounced than for typical natural forests in a similar climate zone. This can be attributed to the substantial amount of soil organic carbon due to intensive historical soil use and soil transplantation during forest construction, as well as relatively warmer temperatures in urban heat domes. Our findings suggest the need for caution in soil management when aiming to reduce CO2 emissions in urban areas.

Urban Forest Governance in the Face of Pulse Disturbances—Canadian Experiences

"The sustainable provision of urban forest benefits can be threatened by the occurrence of sudden, major disturbance events, such as forest fires, insect outbreaks, and extreme weather events, which are considered to be “pulse” disturbance events from a socio-ecological systems perspective. Sound urban forestry programs are needed to prepare for these disturbances and reduce their negative impacts. To investigate the role of governance in building more resilient urban forest socio-ecological systems, the relation between pulse disturbances and urban forest governance was studied in 4 Canadian cities. Our study of local urban forestry included expert interviews with local urban forest governance actors, document analysis, and site visits. The Policy Arrangement Approach was applied to structure and analyse urban forest governance. Findings show that all cities had seen a development of their urban forestry programs and governance over time, such as development of staff and formal plans, as well as alliances with key partners. Pulse disturbances seem to have played an important role in the development and sometimes reorientation of urban forestry programs. Although disturbances often had devastating impacts, having a strong urban forestry program in place, including strong alliances with, e.g., industry partners or NGOs, was considered important for handling the aftermath of these events. Efforts had also been made to be better prepared for future disturbances through further professionalization, development of plans, guidelines, and best practices, capacity building through partnerships, and setting up better real-life information systems in support of decision making. Results can inform urban forest governance and urban forestry programs in Canadian cities and elsewhere."

Urban forests valuation and environmental disposition: The case of Puerto Rico

Contingent valuation is used to examine the influence of environmental engagement and beliefs on willingness to pay (WTP) for urban forest preservation. We survey surrounding residents of two urban forest sites in Puerto Rico with distinct environmental experiences and beliefs about ecosystem services. We find that WTP for preserving the urban forest where the surrounding residents are involved in forest management is $118/year. On the other hand, WTP for preserving a larger urban forest where surrounding residents are not engaged in management is $81/year. In addition to the respondents' characteristics and environmental engagement, WTP also depends on the beliefs about urban forest ecosystem services.

Photosynthesis, fluorescence, and biomass responses of white oak seedlings to urban soil and air temperature effects.

Urban forest patches can provide critical ecosystem services and their ability to regenerate native tree species is critical to their sustainability. Little is known about native tree seedling establishment and physiological function in urban ecosystems. This growth chamber study examined the effects of urban soil and air temperatures on white oak (Quercus alba L.) germination, seedling growth, and leaf-level physiology. A split-plot design tested effects of field collected soils from urban and reference forest sites in Baltimore, Maryland, and warm (urban) versus cool (rural) growth chamber temperature regimes. Seedlings were harvested at the end of the 23-week experiment to assess foliar chemistry and biomass allocation. Seed germination was unaffected by treatments and was high in both soil types and temperature regimes. Urban soils supported significantly higher total seedling biomass and had a significant effect on leaf-level physiological parameters, with seedlings grown in urban soils having greater Anet , Vcmax , ETRmax , Jmax , PNUE, gs , Anet /Rd , and PIabs (an integrated chlorophyll fluorescence parameter). PIabs measurements taken throughout the experiment revealed a significant time × temperature interaction effect. Baltimore urban forest patch soils were higher in nutrients than reference soils, but also higher in heavy metals. Despite higher levels of heavy metals, these results demonstrate that urban forest patch soils are able to support robust white oak seedling growth and enhanced seedling physiological parameters. However, interactions with temperature suggest that warming air temperatures may cause seedling stress and reduced growth.

Natural regeneration in urban forests is limited by early-establishment dynamics: implications for management.

Urban forested natural areas are valuable ecological and social resources, but long-term sustainability of these habitats is challenged by environmental and social factors associated with urban ecosystems. Advances in city-scale assessments of urban forests have increased the resolution of forest community types and conditions, allowing for improved understanding of ecological function, such as natural regeneration, in these urban habitats. By applying metrics of tree regeneration that are commonly used for the management of rural forests, urban ecologists can test the potential for traditional forest management strategies within our cities. In this study, we compare urban and rural oak-hickory forest composition and structure and the capacity for natural regeneration in the New York metropolitan area. Specifically, we use two metrics of advance regeneration that describe the abundance of seedlings and saplings at different size classes to test whether this management for natural regeneration is a viable option. We found differences in recruitment dynamics between urban and rural forests that have implications for the sustainability of these forests and new management strategies. First, after controlling for forest community type, species composition in urban and rural sites was significantly different across multiple strata and within the seed bank. Species-specific capacity for natural regeneration was different in urban and rural sites, signaling the possibility of divergent successional trajectories. Second, while differences in species composition exist, both urban and rural sites were dominated by native species across all forest strata except for urban seed banks. Third, despite finding significantly lower average annual seedling abundance in urban (1.9 seedlings/m2 ) compared to rural (7.1 seedlings/m2 ) sites, we observed greater density of saplings in urban forests, and no significant difference in stocking index between sites. These findings suggest that early-establishment barriers to recruitment are greater in urban forest sites. However, once established, seedling transition into advance regeneration stages may not be different between site types, and advance regeneration may, in some cases, be more viable in urban forested natural areas. These results highlight functional differences between urban and rural forest recruitment dynamics that may impact on the future community composition of oak-hickory forests in the two landscape settings.

Detecting Tree Species Effects on Forest Canopy Temperatures with Thermal Remote Sensing: The Role of Spatial Resolution

Canopy temperatures are important for understanding tree physiology, ecology, and their cooling potential, which provides a valuable ecosystem service, especially in urban environments. Linkages between tree species composition in forest stands and air temperatures remain challenging to quantify, as the establishment and maintenance of onsite sensor networks is time-consuming and costly. Remotely-sensed land surface temperature (LST) observations can potentially acquire spatially distributed crown temperature data more efficiently. We analyzed how tree species modify canopy air temperature at an urban floodplain forest (Leipzig, Germany) site equipped with a detailed onsite sensor network, and explored whether mono-temporal thermal remote sensing observations (August, 2016) at different spatial scales could be used to model air temperatures at the tree crown level. Based on the sensor-network data, we found interspecific differences in summer air temperature to vary temporally and spatially, with mean differences between coldest and warmest tree species of 1 °C, and reaching maxima of up to 4 °C for the upper and lower canopy region. The detectability of species-specific differences in canopy surface temperature was found to be similarly feasible when comparing high-resolution airborne LST data to the airborne LST data aggregated to 30 m pixel size. To realize a spatial resolution of 30 m with regularly acquired data, we found the downscaling of Landsat 8 thermal data to be a valid alternative to airborne data, although detected between-species differences in surface temperature were less expressed. For the modeling of canopy air temperatures, all LST data up to the 30 m level were similarly appropriate. We thus conclude that satellite-derived LST products could be recommended for operational use to detect and monitor tree species effects on temperature regulation at the crown scale.

First western Canadian records of Nebria brevicollis (Coleoptera: Carabidae) and establishment of populations in Coquitlam, British Columbia, Canada

AbstractThe first western Canadian records of the European carabid, Nebria brevicollis (Fabricius) (Coleoptera: Carabidae), are reported from Vancouver, Coquitlam, and Delta, British Columbia, Canada. A species description is provided to facilitate identification of this new invasive species. In addition, pitfall trap data are presented that demonstrate establishment of populations at four locations in Coquitlam. Trap catches were substantially higher at one anthropogenic meadow site than at three urban forest sites. Potential for further expansion of the range of N. brevicollis in British Columbia and beyond is discussed.

Characterizing Tree Spatial Distribution Patterns Using Discrete Aerial Lidar Data

Tree spatial distribution patterns such as random, regular, and clustered play a crucial role in numerical simulations of carbon and water cycles and energy exchanges between forest ecosystems and the atmosphere. An efficient approach is needed to characterize tree spatial distribution patterns quantitatively. This study aims to employ increasingly available aerial laser scanning (ALS) data to capture individual tree locations and further characterize their spatial distribution patterns at the landscape or regional levels. First, we use the pair correlation function to identify the categories (i.e., random, regular, and clustered) of tree spatial distribution patterns, and then determine the unknown parameters of statistical models used for approximating each tree spatial distribution pattern using ALS-based metrics. After applying the proposed method in both natural and urban forest sites, our results show that ALS-based tree crown radii can capture 58%–77% (p < 0.001) variations of visual-based measurements depending on forest types and densities. The root mean squared errors (RMSEs) of ALS-based tree locations increase from 1.46 m to 2.51 m as the forest densities increasing. The Poisson, soft-core, and hybrid-Gibbs point processes are determined as the optimal models to approximate random, regular, and clustered tree spatial distribution patterns, respectively. This work provides a solid foundation for improving the simulation accuracy of forest canopy bidirectional reflectance distribution function (BRDF) and further obtain a better understanding of the processes of carbon and water cycles of forest ecosystems.

White oak and red maple tree ring analysis reveals enhanced productivity in urban forest patches

Many aspects of the urban environment have the potential to affect tree growth and physiology in forest patches, including higher temperatures, elevated CO2 concentrations, and modified soil biogeochemistry from increased nutrient and heavy metal inputs. However, these changes in tree growth are likely to vary by species and across urban areas, reflecting the local environmental conditions associated with the idiosyncratic trajectory of development in a city. Here, we examine growth rates of two dominant native tree species (white oak (Quercus alba L.) and red maple (Acer rubrum L.)) across urban and reference forest sites of three major cities in the eastern United States (New York, NY (NYC); Philadelphia, PA; and Baltimore, MD). We also characterized soil physical and chemical properties around each tree and monitored air temperature over three growing seasons at each site. Throughout the growing season, the urban sites had consistently warmer daytime and nighttime temperatures than reference sites. Urban forest patch soils also had elevated calcium, magnesium, and heavy metal concentrations compared to reference forest soils. Urban vs. reference tree growth rates varied by species, by city, and over time. Despite differences in the two native species’ ecophysiology, both grew more rapidly in the urban environment than at nearby reference sites, particularly in recent decades. Over the entire 145-year tree ring record analyzed, white oak basal area increment was significantly higher in urban trees compared to reference trees. Changes in the relative production of white oak earlywood and latewood between site types in each city and over time may relate to precipitation patterns. Perhaps due to their ability to persist in a wide variety of environmental conditions, mature trees of both species appear to be acclimating to urban forest patch conditions of the eastern U.S. and in some cases are experiencing enhanced growth rates compared to trees in nearby reference forests. An understanding of past and present growth rates of trees in urban forest patches can provide insight into future ecosystem functioning of these urban green spaces as well as that of more rural ecosystems experiencing environmental change factors similar to those associated with urbanization.

Carabidae assemblages in pine forests with different recreation regimes within and outside a megalopolis

The expansion of cities highlights the need for studies of the biodiversity on urban territories and factors affecting the structure and functioning of communities. In 2010–2011, we compared the abundance and diversity of carabid beetles in pine forests of natural origin within the Russian megalopolis Yekaterinburg and outside. To estimate the effects of recreation (R+: trampling, soil compaction, eutrophication) and other urbanization factors (U+: pollution, habitat fragmentation, adventive species), we selected 12 urban and non-urban forest sites with contrasting recreation regimes (U + R+, U + R−, U − R+, U − R−; three sites in each combination). We hypothesized that both urbanization and recreation decrease the abundance and diversity of carabids; the combination of two factors enhances negative effects. The total activity density of carabids and the abundances of all ecological groups increased in urban forests compared to non-urban ones. In urban forests, the Simpson dominance decreased, while Shannon diversity, total species richness, and mean number of species per site increased. The most abundant species in all forests were Pterostichus oblongopunctatus, P. mannerheimii, and P. magus, while Carabus nemoralis was abundant in urban forests only. Proportion (by the number of individuals) of forest species was lower and that of generalists and large-sized species higher in urban forests. High recreation load resulted in lower total abundance and diversity of ground beetles. Negative effect of recreation load on carabids leveled positive effect of urbanization: both abundance and diversity of ground beetles were lower at urban sites with intense recreational use compared to forest sites closed for townspeople.

Trace Elements in Surface Soils and Megascolecidae Earthworms in Urban Forests Within Four Land-Uses Around Poughkeepsie, New York, USA.

Amynthas agrestis and Metaphire hilgendorfi are being distributed across North America with unknown ecosystem impacts. Forest soils in urban areas sequester trace elements and earthworms may be bioaccumulating them. This study examined Cd, Cr, Co, Cu, Mn, Ni, Pb, V, and Zn in soils and earthworm tissues at 28 urban forest sites in and surrounding Poughkeepsie, NY, USA. Megascolecidae were present at 22 sites with means of 12 to 27 individuals m-2 and 4 to 12dryweightgm-2. Urban forest soils within commercial uses had Mn, Pb, and Zn concentrations higher than within residential and agricultural uses. Earthworm trace element concentrations were poorly predicted by their respective soil concentrations, except for Pb. Urban forests in commercial uses and land-preserves, earthworm Cd and Pb concentrations were at or above concentrations known to negatively impact small mammal and bird health ( > 10mgkg-1) with Co and V approaching toxic concentrations.

Photosynthetic traits as indicators for phenotyping urban and peri-urban forests: A case study in the metropolitan city of Rome

Abstract Phenotyping for functional traits associated with photosynthetic machinery could be a promising approach for studying the performance of green infrastructures in metropolitan areas. Trait-based indicators hold important information about ecosystem processes and how environmental constrains may influence the provisioning of services. This work aims to apply a high-throughput phenotyping approach to an urban and a peri-urban forest, in order to evaluate the functionality of vegetation through direct measures of photosynthetic traits such as spectroscopy indices, chlorophyll a fluorescence (ChlF) and leaf chemistry (nitrogen and carbon content). Quercus ilex L. was chosen as the target species for its wide distribution in natural and urban greening, sampled at two distances from a high traffic road (urban forest) and in a natural preserved area (peri-urban forest). The reflectance index most related to the general functionality of photosynthetic machinery was the Fluorescence Ratio Indices FRI740/800, whereas the highest informative indicator traits to differentiate the functionality of Q. ilex in different periods of the year in the urban and peri-urban forest were Normalized Difference Vegetation Index (NDVI), Structure-Insensitive Pigment Index (SIPI) and Normalized Difference Nitrogen Index (NDNI). Interestingly, Photochemical Reflectance Index (PRI) was not only correlated to functional parameters connected to PSII light absorption side, but also with ChlF parameters related to carbon assimilation such as regeneration capacity of the end acceptors. ChlF parameters are effective indicators for highlighting differences between sites, pointing out that the urban forest sites have lower functionality compared to peri-urban one.

Regional differentiation of foliar N/Ca in Fagus americana and F. sylvatica on acid soils

Prolonged periods of air pollution depleted soil Ca and increased N supply in forests of Eastern North America and Central Europe. We compared a cool rural to a warm urban forest site to explore the geographic range of foliar N, Ca, and N/Ca on naturally regenerated saplings of American beech and European beech in Nova Scotia (Canada) and Saarland (Germany), respectively. Foliar N/Ca of beech saplings remained variable due to geo-climatic gradients and bio-climatic site factors, tight internal cycling of Ca, and varying pollution history. Our data suggest that deep and extreme soil Ca depletion renders climatic factors the drivers of foliar N/Ca in beech forests. Global warming will therefore amplify the potential risks of changing nutrient supply ratios in regions with a prolonged history of severe acid rain. Existing forest site classifications usually capture regional differentiation of climatic factors but often fail to assess impacts of acid rain history on foliar Ca that will be required for regional differentiation of foliar nutrient ratios on acid soils. However, homogenization of foliar Ca can be expected in regions with a history of severe acid rain.