•Emissions of volatile organic compounds (VOC) from vegetation combined with anthropogenic emissions of NOx produce ozone.•We assess the scientific evidence of biogenic induction of ground-level ...ozone concentrations in urban and sub-urban areas around the world.•Policies targeting reduction of ground-level ozone in urban and suburban areas must consider a massive reduction of the NOx levels.•Limiting emissions of VOC from both plants and anthropogenic sources should be contemplated until NOx concentrations in cities and sub-urban areas are diminished.•We argue that it is feasible and beneficial to implement measures necessary to limit biogenic contributions to air pollution.
Fast-track programs to plant millions of trees in cities around the world aim at the reduction of summer temperatures, increase carbon storage, storm water control, provision of space for recreation, as well as poverty alleviation. Although these multiple benefits speak positively for urban greening programs, the programs do not take into account the drastic differences between urban and natural systems. Elevated temperatures together with anthropogenic emissions of air and water pollutants distinguish the urban system. Although the potential for emissions of volatile organic compounds from urban vegetation combined with anthropogenic emissions to produce ozone has long been recognized, the municipalities actively enlarging their green spaces still generally either overlook or ignore this fact. Here we assess the scientific evidence of biogenic induction of ground-level ozone concentrations in urban and sub-urban areas and argue that it is feasible and beneficial to implement measures necessary to limit biogenic contributions to air pollution. With the example of biogenic induction of ground level ozone concentrations we demonstrate that interactions between plants and urban ambient conditions have to be taken into account in all efforts of creating “naturopolises”. We explore the mechanisms behind these interactions and propose a pathway to improve our understanding of these interactions.
We present a new synthesis, based on a suite of complementary approaches, of the primary production and carbon sink in forests of the 25 member states of the European Union (EU-25) during 1990-2005. ...Upscaled terrestrial observations and model-based approaches agree within 25% on the mean net primary production (NPP) of forests, i.e. 520±75 g C m⁻² yr⁻¹ over a forest area of 1.32 x 10⁶ km² to 1.55 x 10⁶ km² (EU-25). New estimates of the mean long-term carbon forest sink (net biome production, NBP) of EU-25 forests amounts 75±20 g C m⁻² yr⁻¹. The ratio of NBP to NPP is 0.15±0.05. Estimates of the fate of the carbon inputs via NPP in wood harvests, forest fires, losses to lakes and rivers and heterotrophic respiration remain uncertain, which explains the considerable uncertainty of NBP. Inventory-based assessments and assumptions suggest that 29±15% of the NBP (i.e., 22 g C m⁻² yr⁻¹) is sequestered in the forest soil, but large uncertainty remains concerning the drivers and future of the soil organic carbon. The remaining 71±15% of the NBP (i.e., 53 g C m⁻² yr⁻¹) is realized as woody biomass increments. In the EU-25, the relatively large forest NBP is thought to be the result of a sustained difference between NPP, which increased during the past decades, and carbon losses primarily by harvest and heterotrophic respiration, which increased less over the same period.
► We present the development of the Biome-BGC model to improve its performance in herbaceous ecosystems. ► Phenology representation and soil hydrology were improved, and drought-related processes ...were implemented. ► Management modules were also included in the model. ► The performance of the model was evaluated using eddy covariance-based measurement data.
Apart from measurements, numerical models are the most convenient instruments to analyze the carbon and water balance of terrestrial ecosystems and their interactions with changing environmental conditions. The process-based Biome-BGC model is widely used to simulate the storage and flux of water, carbon, and nitrogen within the vegetation, litter, and soil of unmanaged terrestrial ecosystems. Considering herbaceous vegetation related simulations with Biome-BGC, soil moisture and growing season control on ecosystem functioning is inaccurate due to the simple soil hydrology and plant phenology representation within the model. Consequently, Biome-BGC has limited applicability in herbaceous ecosystems because (1) they are usually managed; (2) they are sensitive to soil processes, most of all hydrology; and (3) their carbon balance is closely connected with the growing season length. Our aim was to improve the applicability of Biome-BGC for managed herbaceous ecosystems by implementing several new modules, including management. A new index (heatsum growing season index) was defined to accurately estimate the first and the final days of the growing season. Instead of a simple bucket soil sub-model, a multilayer soil sub-model was implemented, which can handle the processes of runoff, diffusion and percolation. A new module was implemented to simulate the ecophysiological effect of drought stress on plant mortality. Mowing and grazing modules were integrated in order to quantify the functioning of managed ecosystems. After modifications, the Biome-BGC model was calibrated and validated using eddy covariance-based measurement data collected in Hungarian managed grassland ecosystems. Model calibration was performed based on the Bayes theorem. As a result of these developments and calibration, the performance of the model was substantially improved. Comparison with measurement-based estimate showed that the start and the end of the growing season are now predicted with an average accuracy of 5 and 4 days instead of 46 and 85 days as in the original model. Regarding the different sites and modeled fluxes (gross primary production, total ecosystem respiration, evapotranspiration), relative errors were between 18–60% using the original model and 10–18% using the developed model; squares of the correlation coefficients were between 0.02–0.49 using the original model and 0.50–0.81 using the developed model.
Although urban areas occupy a relatively small fraction of land, they produce major disturbances of the carbon cycle through land use change, climate modification, and atmospheric pollution. In this ...study we quantify effects of urban areas on the carbon cycle in Europe. Among urbanization-driven environmental changes, which influence carbon sequestration in the terrestrial biosphere, we account for: (1) proportion of land covered by impervious materials, (2) local urban meteorological conditions, (3) urban high CO2 concentrations, and (4) elevated atmospheric nitrogen deposition. We use the terrestrial ecosystem model BIOME-BGC to estimate fluxes of carbon exchange between the biosphere and the atmosphere in response to these urban factors. We analysed four urbanization-driven changes individually, setting up our model in such a way that only one of the four was active at a time. From these model simulations we found that fertilization effects from the elevated CO2 and the atmospheric nitrogen deposition made the strongest positive contributions to the carbon uptake (0.023 Pg C year−1 and 0.039 Pg C year−1, respectively), whereas, the impervious urban land and local urban meteorological conditions resulted in a reduction of carbon uptake (−0.005 Pg C year−1 and −0.007 Pg C year−1, respectively). The synergetic effect of the four urbanization-induced changes was an increase of the carbon sequestration in Europe of 0.058 Pg C year−1.
Urbanization Impacts on the Climate in Europe Trusilova, K.; Jung, M.; Churkina, G. ...
Journal of applied meteorology and climatology,
05/2008, Volume:
47, Issue:
5
Journal Article
Peer reviewed
Open access
The objective of this study is to investigate the effects of urban land on the climate in Europe on local and regional scales. Effects of urban land cover on the climate are isolated using the ...fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) with a modified land surface scheme based on the Town Energy Budget model. Two model scenarios represent responses of climate to different states of urbanization in Europe: 1) no urban areas and 2) urban land in the actual state in the beginning of the twenty-first century. By comparing the simulations of these contrasting scenarios, spatial differences in near-surface temperature and precipitation are quantified. Simulated near-surface temperatures and an urban heat island for January and July over a period of 6 yr (2000–05) agree well with corresponding measurements at selected urban areas. The conversion of rural to urban land results in statistically significant changes to precipitation and near-surface temperature over areas of the land cover perturbations. The diurnal temperature range in urbanized regions was reduced on average by 1.26° ± 0.71°C in summer and by 0.73° ± 00.54°C in winter. Inclusion of urban areas results in an increase of urban precipitation in winter (0.09 ± 00.16 mm day−1) and a precipitation reduction in summer (−0.05 ± 0.22 mm day−1).
Although more than 80% of carbon dioxide emissions originate in urban areas, the role of human settlements in the biosphere evolution and in global carbon cycling remains largely neglected. ...Understanding the relationships between the form and pattern of urban development and the carbon cycle is however crucial for estimating future trajectories of greenhouse gas concentrations in the atmosphere and can facilitate mitigation of climate change. In this paper I review state-of-the-art in modeling of urban carbon cycle. I start with the properties of urban ecosystems from the ecosystem theory point of view. Then I discuss key elements of an urban system and to which degree they are represented in the existing models. In conclusions I highlight necessity of including biophysical as well as human related carbon fluxes in an urban carbon cycle model and necessity of collecting relevant data.
Over the last two decades, a disproportional increase of urban land area in comparison with the population growth has been observed in many countries of Europe, and this trend is predicted to ...continue. The conversion of vegetated land into urban land leads to a higher proportion of impervious surface area, to decline and change of vegetation cover, to artificial heat sources, and therefore to changes in climate. This study focuses on the implications of the expansion of urban land for the European climate at the local and regional scales. Regional climate simulations with the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) coupled to the Town Energy Budget model are used to isolate effects of urban land expansion on temperature and precipitation. The study suggests that the expansion of current urban land by 40% would lead to an enlargement of regions affected by thermal stress by a factor of 2, whereas the intensity of the thermal stress does not change significantly. Precipitation in urban areas would be reduced by 0.2 mm day−1in summer as a result of disturbances of the water cycle caused by urban surfaces. The area in which precipitation was altered increased nearly linearly with the urban land increment.
Globally, the year 2003 is associated with one of the largest atmospheric CO2 rises on record. In the same year, Europe experienced an anomalously strong flux of CO2 from the land to the atmosphere ...associated with an exceptionally dry and hot summer in Western and Central Europe. In this study we analyze the magnitude of this carbon flux anomaly and key driving ecosystem processes using simulations of seven terrestrial ecosystem models of different complexity and types (process-oriented and diagnostic). We address the following questions: (1) how large were deviations in the net European carbon flux in 2003 relative to a short-term baseline (1998–2002) and to longer-term variations in annual fluxes (1980 to 2005), (2) which European regions exhibited the largest changes in carbon fluxes during the growing season 2003, and (3) which ecosystem processes controlled the carbon balance anomaly . In most models the prominence of 2003 anomaly in carbon fluxes declined with lengthening of the reference period from one year to 16 years. The 2003 anomaly for annual net carbon fluxes ranged between 0.35 and –0.63 Pg C for a reference period of one year and between 0.17 and –0.37 Pg C for a reference period of 16 years for the whole Europe. In Western and Central Europe, the anomaly in simulated net ecosystem productivity (NEP) over the growing season in 2003 was outside the 1σ variance bound of the carbon flux anomalies for 1980–2005 in all models. The estimated anomaly in net carbon flux ranged between –42 and –158 Tg C for Western Europe and between 24 and –129 Tg C for Central Europe depending on the model used. All models responded to a dipole pattern of the climate anomaly in 2003. In Western and Central Europe NEP was reduced due to heat and drought. In contrast, lower than normal temperatures and higher air humidity decreased NEP over Northeastern Europe. While models agree on the sign of changes in simulated NEP and gross primary productivity in 2003 over Western and Central Europe, models diverge in the estimates of anomalies in ecosystem respiration. Except for two process models which simulate respiration increase, most models simulated a decrease in ecosystem respiration in 2003. The diagnostic models showed a weaker decrease in ecosystem respiration than the process-oriented models. Based on the multi-model simulations we estimated the total carbon flux anomaly over the 2003 growing season in Europe to range between –0.02 and –0.27 Pg C relative to the net carbon flux in 1998–2002.
Intensive use of the chernozem soils of Northern Kazakhstan since the development of virgin lands has led to soil erosion and loss of humus. Since 1954, according to researchers, 1.2 bln tons of ...organic matter have been irretrievably lost. During this period, the methods of tillage have changed significantly from surface to subsurface tillage, which led to a change in the method of accumulation of organic residues in the soil. The purpose of this study was the short-term monitoring of spring wheat cultivation technologies to observe their influence on crop productivity and soil agrocenosis. A virgin plot was used as a standard of soil fertility. Determination of nutrients in the soil was carried out by using the method of "wet chemistry" with spectrophotometric termination. An infrared analyzer was used to assess the grain quality. The identification of soil microorganisms was carried out on nutrient microbiological media, such as meat-and-peptone agar, starch-and-ammonia agar, and Czapek-Dox agar. The results of three-year studies showed that the humus content in the variants with permanent wheat decreased to 3.26-3.38%. The greatest decrease in humus content was observed in the two-field grain and fallow crop rotation (2.48%). The decrease in the amount of humus occurred as a result of insufficient intake of plant residues and mineral fertilizers. The content of nitrate nitrogen and mobile phosphorus in virgin soil is low. Soil micromycetes dominate on virgin lands, whereas ammonifiers and immobilizers dominate on cultivated soils. The high level of carbon dioxide emissions on virgin land (3.0 C2 kg/ha/hour) is due to the presence of a large amount of plant biomass. The most optimal variant out the considered technological backgrounds from the point of view of increasing yields up to 15.8 c/ha and preserving soil fertility (3.26% humus content) is the cultivation of permanent wheat with the introduction of fertilizers and herbicides. The use of two-field grain and fallow crop rotation leads to irreplaceable losses of organic matter (2.48%).
Summary
Seventeen global models of terrestrial biogeochemistry were compared with respect to annual and seasonal fluxes of net primary productivity (NPP) for the land biosphere. The comparison, ...sponsored by IGBP‐GAIM/DIS/GCTE, used standardized input variables wherever possible and was carried out through two international workshops and over the Internet. The models differed widely in complexity and original purpose, but could be grouped in three major categories: satellite‐based models that use data from the NOAA/AVHRR sensor as their major input stream (CASA, GLO‐PEM, SDBM, SIB2 and TURC), models that simulate carbon fluxes using a prescribed vegetation structure (BIOME‐BGC, CARAIB 2.1, CENTURY 4.0, FBM 2.2, HRBM 3.0, KGBM, PLAI 0.2, SILVAN 2.2 and TEM 4.0), and models that simulate both vegetation structure and carbon fluxes (BIOME3, DOLY and HYBRID 3.0). The simulations resulted in a range of total NPP values (44.4–66.3 Pg C year–1), after removal of two outliers (which produced extreme results as artefacts due to the comparison). The broad global pattern of NPP and the relationship of annual NPP to the major climatic variables coincided in most areas. Differences could not be attributed to the fundamental modelling strategies, with the exception that nutrient constraints generally produced lower NPP. Regional and global NPP were sensitive to the simulation method for the water balance. Seasonal variation among models was high, both globally and locally, providing several indications for specific deficiencies in some models.
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