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To ensure the good chemical status of surface water across Europe, it is necessary to increase research on the comprehensive impact of land use and land cover changes, i.e., deforestation, on the natural environment. For this reason, we used data from 9-year environmental monitoring in the Wüstebach experimental catchment of the TERENO (Terrestrial Environmental Observatories) network to determine the impact of partial deforestation on solute fluxes and stream water ionic composition. In 2013, a partial deforestation experiment was conducted in the study area using a cut-to-length logging method. To this end, two headwater catchments were compared: one partially deforested (22% of the catchment area) and one untreated control catchment. The concentrations of ions in stream water, groundwater, and precipitation were analyzed: Ca2+, Mg2+, Na+, K+, Al3+, Fetot, Mn2+, NO3−, SO4−, and Cl−. Most of the ions (Na+, Ca2+, Mg2+, Cl−, and SO4−) showed decreasing trends in concentrations after deforestation, indicating a dilution effect in stream water due to the reduction of the supply of solutes with precipitation in the open deforested area. The fluxes of these ions decreased by 5–7% in the first year after deforestation, although the stream runoff increased by 5%. In the second year, the decrease in ion fluxes was greater, from 6% to 24%. This finding confirms that only limited soil erosion occurred after the deforestation because the soil was well protected during logging works by covering harvester lanes with branches. Only K+ and NO3− ions showed increasing trends in both concentrations and fluxes in the partially deforested catchment in the first two to three years after deforestation. Spruce die-offs, common in Europe, may decrease the concentration and fluxes of base cations in surface water in a nutrient-limited environment. However, the simultaneous planting of young broad-leaved trees with post-harvesting regrowth could create a nutrient sink that protects the catchment area from nutrient depletion. [ABSTRACT FROM AUTHOR]

Forest canopies present irregular surfaces that alter both the quantity and spatiotemporal variability of precipitation inputs. The drop size distribution (DSD) of rainfall varies with rainfall event characteristics and is altered substantially by the forest stand properties. Yet, the influence of two major European tree species, European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) H. Karst), on throughfall DSD is largely unknown. In order to assess the impact of these two species with differing canopy structures on throughfall DSD, two optical disdrometers, one above and one below the canopy of each European beech and Norway spruce, measured DSD of both incident rainfall and throughfall over 2 months at a 10‐s resolution. Fractions of different throughfall categories were analysed for single‐precipitation events of different intensities. While penetrating the canopies, clear shifts in drop size and temporal distributions of incoming rainfall were observed. Beech and spruce, however, had different DSD, behaved differently in their effect on diameter volume percentiles as well as width of drop spectrum. The maximum drop sizes under beech were higher than under spruce. The mean ± standard deviation of the median volume drops size (D50) over all rain events was 2.7 ± 0.28 mm for beech and 0.80 ± 0.04 mm for spruce, respectively. In general, there was a high‐DSD variability within events indicating varying amounts of the different throughfall fractions. These findings help to better understand the effects of different tree species on rainfall partitioning processes and small‐scale variations in subcanopy rainfall inputs, thereby demonstrating the need for further research in high‐resolution spatial and temporal properties of rainfall and throughfall. [ABSTRACT FROM AUTHOR]

A continuous, 36-year measurement record of atmospheric carbon dioxide (CO2) at three measurement sites of Mount Zugspitze, Germany was studied. The CO2 trend and seasonality were analyzed by decomposing the long-term time series into trend and seasonal components. The mean CO2 annual growth rate over the 36 year period at Zugspitze is 1.8 ppm yr-1, which is in good agreement with the Mauna Loa station and the global means. The peak-to-trough amplitude of the mean CO2 seasonal cycle is 11.67 ppm at Mount Zugspitze, which is significantly less than nearby measurement sites at Mount Wank and Schauinsland, but which follow similar patterns. To characterize this mountain site better, analyses of weekly periodicity and the diurnal cycle were performed to provide evidence of local sources and sinks of CO2. Together, with an atmospheric trace gas (CO and NO) and the number of site visitor case study, clear weekday-weekend differences were detected, indicating potential CO2 sources in the near vicinity. [ABSTRACT FROM AUTHOR]

Headwaters are a source of fresh water and material transported to the downstream sections of river channels. In most regions of Europe, the natural environment of headwaters has been significantly transformed by human activities, which is reflected in the quality of surface waters and the rate of solute fluxes. The aim of the study was to determine the anthropogenic impact on solute fluxes in a headwater catchment in Germany. The study area (Wüstebach experimental catchment) is located in the Eifel Mountains and is part of the TERENO (Terrestrial Environmental Observatories) network. The catchment is currently subject to the following anthropogenic pressures: the use of de-icing salts on the motorway running through the catchment and the logging of 22% of the forest area in 2013 by the National Park to promote the regeneration of near-natural beech forest. We used data from almost 13 years (June 2009-April 2022) of environmental monitoring in the Wüstebach catchment to calculate monthly and annual rates of solute fluxes. The concentrations of ions in stream water and precipitation were determined: Ca2+, Mg2+, Na+, K+, Al3+, Fetot, Mn2+, NH4+, NO3−, SO4−, and Cl−. Data from the Wüstebach catchment were compared with data from the control (untreated) catchment. The average annual rate of total dissolved solids in the Wüstebach catchment was 83 t/km2/a. Only the loads of four ions performed a significant difference after deforestation (SO4−, NH4+, Al3+, Fetot). However, total dissolved solids and loads of most of the ions did not show any significant differences after deforestation, which indicates a slight impact of logging on the chemical denudation. This resulted from the limited soil erosion that followed deforestation as the soil was well protected during logging works by covering harvester lanes with branches. However, there is a significant impact of road salting on the solute fluxes in the headwater catchment. Assuming that the control catchment is not affected by using de-icing salts, the road salting inputs in the Wüstebach catchment calculated based on the precipitation share for Na+, Ca2+, Mg2+, K+, and Cl− ions were, on average, 88%, 53%, 18%, 53%, and 90%, respectively, of the original ion loads. The input with road salting was so large that elevated concentrations of Na+ and Cl− were noted throughout the study period with slight seasonal fluctuations. This proves the subsurface build-up of salt due to the long-term application of de-icing salt. Without the input of de-icing salts, the average annual rate of chemical denudation in the catchment would be about 19 t/km2/a. Thus, on average, this ion storage effect in the soil has increased the total dissolved solids rate by 62%. In summary, it can be concluded that long-term intensive road salting in winter has a greater impact on the solute fluxes than the clear-cut of 22% of the catchment area. [ABSTRACT FROM AUTHOR]

Climate change has affected plant phenology; increasing temperatures are associated with advancing first flowering dates. The impact on flowering duration, however, has rarely been studied. In this study, we analysed first flowering dates and flowering durations from a 27 year dataset of weekly flower observations on 232 plant species from the island of Guernsey in the English Channel. The aim of this study was to explore variation in trends and relationships between first flowering dates, flowering duration and temperature. We specifically looked for evidence that traits, such as life forms and phylogenetic groups, explained variation in sensitivity of first flowering and flowering duration among species. Overall trends revealed significantly earlier flowering over time, by an average of 5.2 days decade−1 since 1985. A highly significant shortening of flowering duration was observed by an average of 10 days decade−1. Correlations between first flowering, flowering duration and year varied between different species, traits and flowering periods. Significant differences among traits were observed for first flowering and to a lesser degree for flowering duration. Overall, in comparison to first flowering, more species had significant trends in flowering duration. Temperature relationships revealed large differences in strength and direction of response. 55% of the species revealed a significant negative relationship of first flowering dates and temperature. In contrast, only 19% of flowering durations had a significant negative temperature relationship. The advance in first flowering date together with a shortening of flowering duration suggests potentially serious impacts on pollinators, which might pose a major threat to biodiversity, agriculture and horticulture. Human health, in terms of pollen allergies, however, might benefit from a shortening of specific plant pollen seasons. [ABSTRACT FROM AUTHOR]

Fine fuel moisture content is a key parameter in fire danger and behaviour applications. For modelling purposes, equilibrium moisture content (EMC) curves are an important input parameter. This paper provides EMC data for central European fuels and adds methodological considerations that can be used to improve existing test procedures. Litter samples of Norway spruce (Picea abies (L.) Karst), Scots pine (Pinus sylvestris L.), European beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L.) were subjected to three different experiments using conditioning in a climate chamber and above saturated salt solutions. Climate chamber conditioning yielded the best results and can generally be recommended, however saturated salt solutions are able to produce lower relative humidities, which are relevant to forest fire applications as they represent the highest fire danger. Results were within the range of published sorption isotherms for forest fine fuels. A fairly clear gradation was present with higher EMC values in leaf litters than in needle litters. These differences are in accord with values from the literature and suggest general differences in the sorption properties of leaves and needles, which may be caused by differing chemical and physical properties. The influence of temperature on EMC described in the literature could be confirmed. [ABSTRACT FROM AUTHOR]

The vertical temperature structure in the area of Garmisch-Partenkirchen between the Loisach river valley and the highest mountain in Germany (Zugspitze, 2962 m a.s.l.) is analysed. Using long time series (1936-2008) of daily mean, minimum and maximum temperatures from two meteorological stations, in the valley floor and on the mountain top, we studied seasonal variations in temperature lapse rates. By using daily data on weather types, significantly different altitudinal temperature lapse rates and daily temperature ranges for low and high pressure weather situations were found. There was no significant influence of snow cover in the valley on the lapse rate. At both stations, there has been an increase in temperature during recent decades. As there was a slight difference between these trends, the lapse rate has tended to become more negative, i.e. the difference between the mountain top and the valley has become more pronounced. In order to investigate the lapse rates in more detail, unpublished temperature data from 1989 to 1990 on slope transects near Garmisch-Partenkirchen were evaluated. Despite the fact that an exact description of the vertical structure of the atmospheric temperature is possible only from free air measurements, there are some indications that major inversions occur in the first 500 m above the valley ground, depending on season, weather situation and time of day. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Abstract: During the TRAMP field campaign in August–September 2006, C2–C10 volatile organic compounds (VOCs) were measured continuously and online at the urban Moody Tower (MT) site. This dataset was compared to corresponding VOC data sets obtained at six sites located in the highly industrialized Houston Ship Channel area (HSC). Receptor modeling was performed by positive matrix factorization (PMF) at all sites. Conditional probability functions (CPF) were used to determine the origin of the polluted air masses in the Houston area. A subdivision into daytime and nighttime was carried out to discriminate photochemical influences. Eight main source categories of industrial, mobile, and biogenic emissions were identified at the urban receptor site, seven and six, respectively, at the different HSC sites. At MT natural gas/crude oil contributed most to the VOC mass (27.4%), followed by liquefied petroleum gas (16.7%), vehicular exhaust (15.3%), fuel evaporation (14.3%), and aromatics (13.4%). Also petrochemical sources from ethylene (4.7%) and propylene (3.6%) play an important role. A minor fraction of the VOC mass can be attributed to biogenic sources mainly from isoprene (4.4%). Based on PMF analyses of different wind sectors, the total VOC mass was estimated to be twofold at MT with wind directions from HSC compared to air from a typical urban sector, for petrochemical compounds more than threefold. Despite the strong impact of air masses influenced by industrial sources at HSC, still about a third of the total mass contributions at MT can be apportioned to other sources, mainly motor vehicles and aromatic solvents. The investigation of diurnal variation in combination with wind directional frequencies revealed the greatest HSC impact at the urban site during the morning, and the least during the evening. [Copyright &y& Elsevier]

In 2006, a controlled infection study was performed in the ‘Kranzberger Forst’ to address the following questions: (1) Will massive artificial inoculation with Apiognomonia errabunda override the previously observed inhibitory effect of chronic ozone? (2) Can biochemical or molecular markers be detected to account for the action of ozone? To this end six adult beech trees were chosen, three ozone fumigated (2× ozone) and three control trees (ambient = 1× ozone). Spore-sprayed branches of sun and shade crown positions of each of the trees, and uninoculated control branches, were enclosed in 100-L plastic bags for one night to facilitate infection initiation. Samples were taken within a five-week period after inoculation. A. errabunda infestation levels quantified by real-time PCR increased in leaves that were not fumigated with additional ozone. Cell wall components and ACC (ethylene precursor 1-amino cyclopropane-1-carboxylic acid) increased upon ozone fumigation and may in part lead to the repression of fungal infection. [Copyright &y& Elsevier]

Within the CO2 time series measured at the Environmental Research Station Schneefernerhaus (UFS), Germany, as part of the Global Atmospheric Watch (GAW) program, pollution episodes are traced back to local and regional emissions, identified by δ13C(CO2) as well as ratios of CO and CH4 to CO2 mixing ratios. Seven episodes of sudden enhancements in the tropospheric CO2 mixing ratio are identified in the measurements of mixing/isotopic ratios during five winter months from October 2012 to February 2013. The short-term CO2 variations are closely correlated with changes in CO and CH4 mixing ratios, achieving mean values of 6.0 ± 0.2 ppb/ppm for CO/CO2 and 6.0 ± 0.1 ppb/ppm for CH4/CO2. The estimated isotopic signature of CO2 sources (δs) ranges between −35‰ and −24‰, with higher values indicating contributions from coal combustion or wood burning, and lower values being the result of natural gas or gasoline. Moving Keeling plots with site-specific data selection criteria are applied to detect these pollution events. Furthermore, the HYSPLIT trajectory model is utilized to identify the trajectories during periods with CO2 peak events. Short trajectories are found covering Western and Central Europe, while clean air masses flow from the Atlantic Ocean and the Arctic Ocean. [ABSTRACT FROM AUTHOR]

Abstract: The Alps are affected by high nitrogen deposition, particularly in the fringe of the Northern and Southern Alps. In the framework of a two-year monitoring study performed in 2010 and 2011, we investigated the ammonia and nitrogen dioxide air concentration and ammonium and nitrate deposition at different altitudes between 700 and 1600ma.s.l. in the Garmisch-Partenkirchen district in the Upper Bavaria region (Germany). Four-weekly measurements of deposition collected with bulk open field samplers and under-crown were performed in a profile perpendicular to the axis of the Loisach valley; measurements were conducted at eight sites. Whereas open field deposition ranged from 5 to 11kgha−1 a−1, nitrogen throughfall has reached up to 21kgha−1 a−1. Data from the valley and the slopes were compared with measurements performed on the platform of the Environmental Research Station Schneefernerhaus (Zugspitze) at an altitude of 2650ma.s.l. For the rough estimation of the total yearly deposition rate of nitrogen, the canopy uptake model was applied. By regarding nitrogen uptake by the trees, total deposition can exceed the throughfall in all sites by up to 50%. Additionally, we estimated the total deposition from the sum of wet and dry deposition. On the one side, the wet deposition could be extrapolated from the open field deposition. On the other side, we used the inferential method to calculate the dry deposition on the basis of NH3 and NO2 air concentrations and their literature based deposition velocities. Since fixed deposition velocities are inappropriate particularly in complex orography, we tried to find correction factors based upon terrain characteristics and meteorological considerations. Temperature monitoring at the eight sites and wind measurements at two sites provided some evidence for the semi-empirical parameterization. Due to numerous imponderabilities, the results of the two methods were not consistent for all sites. [Copyright &y& Elsevier]

Abstract: A radiative transfer model and photochemical box model are used to examine the effects of clouds and aerosols on actinic flux and photolysis rates, and the impacts of changes in photolysis rates on ozone production and destruction rates in a polluted urban environment like Houston, Texas. During the TexAQS-II Radical and Aerosol Measurement Project the combined cloud and aerosol effects reduced j(NO2) photolysis frequencies by nominally 17%, while aerosols reduced j(NO2) by 3% on six clear sky days. Reductions in actinic flux due to attenuation by clouds and aerosols correspond to reduced net ozone formation rates with a nearly one-to-one relationship. The overall reduction in the net ozone production rate due to reductions in photolysis rates by clouds and aerosols was approximately 8 ppbv h−1. [Copyright &y& Elsevier]

Abstract: Both similarities and differences in summertime atmospheric photochemical oxidation appear in the comparison of four field studies: TEXAQS2000 (Houston, 2000), NYC2001 (New York City, 2001), MCMA2003 (Mexico City, 2003), and TRAMP2006 (Houston, 2006). The compared photochemical indicators are OH and HO2 abundances, OH reactivity (the inverse of the OH lifetime), HO x budget, OH chain length (ratio of OH cycling to OH loss), calculated ozone production, and ozone sensitivity. In terms of photochemical activity, Houston is much more like Mexico City than New York City. These relationships result from the ratio of volatile organic compounds (VOCs) to nitrogen oxides (NO x ), which are comparable in Houston and Mexico City, but much lower in New York City. Compared to New York City, Houston and Mexico City also have higher levels of OH and HO2, longer OH chain lengths, a smaller contribution of reactions with NO x to the OH reactivity, and NO x -sensitivity for ozone production during the day. In all four studies, the photolysis of nitrous acid (HONO) and formaldehyde (HCHO) are significant, if not dominant, HO x sources. A problematic result in all four studies is the greater OH production than OH loss during morning rush hour, even though OH production and loss are expected to always be in balance because of the short OH lifetime. The cause of this discrepancy is not understood, but may be related to the under-predicted HO2 in high NO x conditions, which could have implications for ozone production. Three photochemical indicators show particularly high photochemical activity in Houston during the TRAMP2006 study: the long portion of the day for which ozone production was NO x -sensitive, the calculated ozone production rate that was second only to Mexico City''s, and the OH chain length that was twice that of any other location. These results on photochemical activity provide additional support for regulatory actions to reduce reactive VOCs in Houston in order to reduce ozone and other pollutants. [Copyright &y& Elsevier]

Abstract: Concentrations of CO, SO2, NO, NO2, and NOY were measured atop the University of Houston''s Moody Tower supersite during the 2006 TexAQS-II Radical and Aerosol Measurement Project (TRAMP). The lowest concentrations of all primary and secondary species were observed in clean marine air in southerly flow. SO2 concentrations were usually low, but increased dramatically in sporadic midday plumes advected from sources in the Houston Ship Channel (HSC), located NE of the site. Concentrations of CO and NOx displayed large diurnal variations in keeping with their co-emission by mobile sources in the Houston Metropolitan Area (HMA). CO/NOx emission ratios of 5.81 ± 0.94 were observed in the morning rush hour. Nighttime concentrations of NOx (NOx = NO + NO2) and NOY (NOY = NO + NO2 + NO3 + HNO3 + HONO + 2∗N2O5 + HO2NO2 + PANs + RONO2 + p-NO3 − + …) were highest in winds from the NNW-NE due to emission from mobile sources. Median ratios of NOx/NOY were approximately 0.9 overnight, reflecting the persistence and/or generation of NOZ (NOZ = NOY − NOx) species in the nighttime Houston boundary layer, and approached unity in the morning rush hour. Daytime concentrations of NOx and NOY were highest in winds from the HSC. NOx/NOY ratios reached their minimum values (median ca 0.63) from 1300 to 1500 CST, near local solar noon, and air masses often retained enough NOx to sustain additional O3 formation farther downwind. HNO3 and PANs comprised the dominant NOZ species in the HMA, and on a median basis represented 17–20% and 12–15% of NOY, respectively, at midday. Concentrations of HNO3, PANs, and NOZ, and fractional contributions of these species to NOY, were at a maximum in NE flow, reflecting the source strength and reactivity of precursor emissions in the HSC. As a result, daytime O3 concentrations were highest in air masses with HSC influence. Overall, our findings confirm the impact of the HSC as a dominant source region within the HMA. A comparison of total NOY measurements with the sum of measured NOY species (NOYi = NOx + HNO3 + PANs + HONO + p-NO3 −) yielded excellent overall agreement during both day ([NOY](ppb) = ([NOYi](ppb)∗1.03 ± 0.16) − 0.42; r 2 = 0.9933) and night ([NOY](ppb) = ([NOYi](ppb)∗1.01 ± 0.16) + 0.18; r 2 = 0.9975). A similar comparison between NOY–NOx concentrations and the sum of NOZi (NOZi = HNO3 + PANs + HONO + p-NO3 −) yielded good overall agreement during the day ([NOZ](ppb) = ([NOZi](ppb)∗1.01 ± 0.30) + 0.044 ppb; r 2 = 0.8527) and at night ([NOZ](ppb) = ([NOZi](ppb)∗1.12 ± 0.69) + 0.16 ppb; r 2 = 0.6899). Median ratios of NOZ/NOZi were near unity during daylight hours but increased to approximately 1.2 overnight, a difference of 0.15–0.50 ppb. Differences between NOZ and NOZi rarely exceeded combined measurement uncertainties, and variations in NOZ/NOZi ratios may have resulted solely from errors in conversion efficiencies of NOY species and changes in NOY composition. However, nighttime NOZ/NOZi ratios and the magnitude of NOZ − NOZi differences were generally consistent with recent observations of ClNO2 in the nocturnal Houston boundary layer. [Copyright &y& Elsevier]

Forests account for nearly 90 % of the world's terrestrial biomass in the form of carbon and they support 80 % of the global biodiversity. To understand the underlying forest dynamics, we need a long-term but also relatively high-frequency, networked monitoring system, as traditionally used in meteorology or hydrology. While there are numerous existing forest monitoring sites, particularly in temperate regions, the resulting data streams are rarely connected and do not provide information promptly, which hampers real-time assessments of forest responses to extreme climate events. The technology to build a better global forest monitoring network now exists. This white paper addresses the key structural components needed to achieve a novel meta-network. We propose to complement - rather than replace or unify - the existing heterogeneous infrastructure with standardized, quality-assured linking methods and interacting data processing centers to create an integrated forest monitoring network. These automated (research topic-dependent) linking methods in atmosphere, biosphere, and pedosphere play a key role in scaling site-specific results and processing them in a timely manner. To ensure broad participation from existing monitoring sites and to establish new sites, these linking methods must be as informative, reliable, affordable, and maintainable as possible, and should be supplemented by near real-time remote sensing data. The proposed novel meta-network will enable the detection of emergent patterns that would not be visible from isolated analyses of individual sites. In addition, the near real-time availability of data will facilitate predictions of current forest conditions (nowcasts), which are urgently needed for research and decision making in the face of rapid climate change. We call for international and interdisciplinary efforts in this direction., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Zweifel Roman reports financial support was provided by Federal Office for the Environment., (Copyright © 2023 Elsevier B.V. All rights reserved.)

[This corrects the article DOI: 10.1186/s13007-017-0166-6.].