Larch forests of Middle Siberia: long-term trends in fire return intervals

Fire history within the northern larch forests of Central Siberia was studied (65 + °N). Fires within this area are predominantly caused by lightning strikes rather than human activity. Mean fire return intervals (FRIs) were found to be 112 ± 49 years (based on firescars) and 106 ± 36 years (based on firescars and tree natality dates). FRIs were increased with latitude increase and observed to be about 80 years at 64°N, about 200 years near the Arctic Circle and about 300 years nearby the northern range limit of larch stands (~71° + N). Northward FRIs increase correlated with incoming solar radiation (r = ?0.95). Post-Little Ice Age (LIA) warming (after 1850) caused approximately a doubling of fire events (in comparison with a similar period during LIA). The data obtained support a hypothesis of climate-induced fire frequency increase.     

Fir decline and mortality in the southern Siberian Mountains

Regional Environmental Change - Increased dieback and mortality of “dark needle conifer” (DNC) stands (composed of fir (Abies sibirica), Siberian pine (Pinus sibirica) and spruce (Picea...     

Mapping atmospheric depositions of cadmium and lead in Germany based on EMEP deposition data and the European Moss Survey 2005

Background

The vertical migration of phytoplankton was investigated in natural waters using in situ fluorescence profiling, chlorophyll a concentrations and life counts at two study sites differing in coloured dissolved organic matter (cDOM) concentrations. The data from the corresponding water depths (50-cm intervals down to 10 m) and times (hourly, before dawn to sunset, several days) were related to the highly resolved (2 nm) underwater ultraviolet radiation (UVR)/photosynthetic active radiation (PAR) transparency (290 to 700 nm).

Results

Chlorophyll a maxima of mainly motile dinoflagellates were observed in situ at all days and at both study sites (open marine, brackish waters), independent on prevailing weather conditions or cDOM concentrations. Phytoplankton migration was triggered solely by irradiance in the 400- to 700-nm wavelength range (PAR) at the particular water depth, irrespective of PAR/UVR ratios and surface UVR (290 to 400 nm), after an illumination period of about 40 min. Interestingly, the PAR tolerance levels of the phytoplankton, which have been lower in cDOM-rich waters, matched their light acclimation values determined by parallel PAM measurements.

Conclusions

The response of the phytoplankton to PAR is not a sufficient protection strategy versus increasing UVR levels, which might have wide ecological implications beyond the level of primary producers to impact important ecosystem functions such as the delicate trophic interactions.     

Atmosphärische Deposition und Anreicherung von Schwermetallen und Stickstoff in Natura-2000-Gebieten Deutschlands

Purpose Under the Convention on Long-range Transboundary Air Pollution mosses are used to map the bioaccumulation of heavy metals and nitrogen throughout Europe. To this end, since 1990 mosses were sampled and analyzed chemically every five years. The goal of this article is to apply the moss survey data for assessing the bioaccumulation of Cd, Pb and N in German Natura 2000 Sites of Community Importance (SCI). Methods The temporal trends of the heavy metal bioaccumulation within SCIs were analyzed using a multi metal index (MMI) calculated by means of geostatistics and percentile statistics. For nitrogen, only monitoring values for 2005 were available for the assessment. The geostatistically estimated values of the metal and nitrogen concentrations in mosses were transformed to estimated deposition values by use of regression analyses. Subsequently, the results were integrated into the assessment of the German SCIs. Results Highest metal loads within SCIs were detected in 1990, followed by a continuous decrease to 2000 and a significant increase until 2005. Regarding N, a median of 1.5?% nitrogen in the dry mass was calculated. The deposition values calculated from the moss estimates resulted in median values of 0.33?g/ha/a for Cd, 8.2?g/ha/a for Pb and 16.7?kg/ha/a for nitrogen. Conclusions The Moss-Monitoring is the only environmental monitoring programme which enables statistically sound estimations of the exposure of SCI to environmental contaminants in terms of heavy metal and nitrogen deposition and bioaccumulation.     

Anreicherung atmosphärischer Depositionen von Metallen und Stickstoff in Moosen Mecklenburg-Vorpommerns von 1990 bis 2005

Background, aim and scope Since 1990 the UN ECE Heavy Metals in Mosses Surveys provide data inventories of the atmospheric heavy metal bioaccumulation across Europe. In the survey 2005 the nitrogen accumulation was measured for the first time in most of the participating countries. In Germany, the surveys were conducted in close cooperation of the relevant authorities of both the Federal Republic and the sixteen states. Therefore, statistical evaluations of the moss survey data with regard to the whole German territory and single federal states are of interest. This article concentrates on Mecklenburg-Western Pomerania, dealing with the mapping of the spatiotemporal trends of metal accumulation from 1990 to 2005, the spatial patterns of nitrogen accumulation in 2005, and the spatial variability of bioaccumulation due to characteristics of the sampling sites and their surroundings. Materials and methods The bioaccumulation of up to 40 trace elements in mosses was determined according to a Europe-wide harmonised methodology. The according experimental protocol regulates the selection of sampling sites and moss species, the chemical analysis and quality control and the classification of the measured values for mapping spatial patterns. In Mecklenburg-Western Pomerania all sampling sites were described with regard to topographical and ecological characteristics and several criteria to be fulfilled according to the guideline. Together with the measurements this metadata was combined with other information regarding land use in the surroundings of the sampling sites in the WebGIS MossMet. The spatial structure of the metal bioaccumulation was analysed and modelled by variogram analyses and then mapped by applying different kriging techniques. Furthermore, multi metal indices (MMI) were derived for both the sampling sites and raster maps with help of percentile statistics: The MMI_1990–2005 was calculated for As, Cd, Cr, Cu, Fe, Ni, Pb, Ti, V and Zn. The statistical association of the metal bioaccumulation, site specific characteristics as well as information on land use and emissions was analysed by bivariate nonparametric correlation analysis, contingency tables and Chi-square Automatic Interaction Detection (CHAID). Results The results of the quality controlled chemical analyses show a significant decrease of the metal bioaccumulation in Germany from 1990 to 2000 for all elements. However, in Mecklenburg-Western Pomerania the concentrations of Cr and Zn are even significantly higher than those found in 1990. From 2000 to 2005?a further non-significant increase can be stated for As, Cu, Ni and Ti. The concentrations of Cd and Pb decreased significantly throughout all four surveys. The MMI illustrates the temporal trend of the metal bioaccumulation as a whole: After a significant decrease from 1990 to 2000 it increased significantly till 2005. The N concentration in mosses in Mecklenburg-Western Pomerania reaches from 1.3 to 2.3?% in dry mass and is negatively correlated with the forest ratio in the surroundings of the moss sampling sites and to the same degree positively correlated with the area ratio of agricultural land uses. Except for Cd, Pb and Sb all metal concentrations in the mosses are negatively correlated with the forest ratio around the sampling sites. With the exception of Cr all metal concentrations are further negatively correlated with the precipitation sums of the accumulation periods. Only the Cu and Zn concentrations show no or rather a negative correlation with the tree height whereas all other elements exhibit positive correlations. Furthermore, all elements except Cr are significantly associated to the sampled moss species, the growth pattern and the frequency of occurrence of the mosses at the respective sampling sites. Exemplified for Cu multivariate correlations were furthermore detected by CHAID. It could be shown that the frequency of the mosses, the sampled moss species, the distance to motorways and the distance to the Baltic Sea are the statistically most significant boundary conditions of the Cu concentrations in the mosses sampled in Mecklenburg-Western Pomerania in 2005. No correlations were found between the modelled total depositions and the concentrations of Cd, Hg and Pb in the mosses at p < 0.1. For Pb in 1995?r is 0.52 at p = 0.012, for the other surveys no correlations at p < 0.05 could be found. Discussion The increase of the Cr bioaccumulation from 2000 till 2005 is particularly pronounced in Mecklenburg-Western Pomerania. This trend is confirmed with regional differences in the national average as well as in other participating countries like in Switzerland. Deposition measurements did not register this trend. In contrast to the UNECE area, the federal territory and several federal states no correlations were found between the modelled total depositions and the metal concentrations in the mosses. Conclusions The fact that no correlations were found between the modelled total depositions and the element concentrations in the mosses may be caused by the low spatial resolution (50?×?50?km) of the EMEP data. The moss surveys contribute to the heavy metal and the multi-component-model of CLRTAP because they prove on different spatial scales how air pollution control influences the accumulation of emitted substances in environmental subjects of protection like vegetation. In contrast to deposition measurement networks the moss monitoring identified a trend reversal in Mecklenburg-Western Pomerania: The continuous decrease of the metal bioaccumulation in mosses from 1990 till 2000 has changed to an increase of several metals between 2000 and 2005. This increase is significant for Cr and Zn. Recommendations and perspectives The spatial resolution of the EMEP deposition data should be enhanced based on the Europe-wide regression relationship between the element concentrations in the deposition and in the mosses. For regional studies the existing but so far not useable deposition measurement data of the federal states should be made available. It should further be investigated what caused the increase of the Cr concentrations above the level of 1990 – perhaps emissions or biogenic effects as a consequence of simultaneously increased nitrogen loads? The Heavy Metals in Mosses Surveys are a positive example for environmental monitoring activities reaching across three spatial and administrative levels: regional (e.?g. federal state or natural landscape), nation wide (e.?g. Germany) and continental (e.?g. Europe). In Germany the harmonised and quality controlled moss data are made available via a WebGIS portal. Therefore the moss data may easily be accessed for environmental monitoring purposes and the control of environmental political actions. Hence, the continuous task of environmental monitoring can be met and carried on in the future. It should further be considered to expand the moss monitoring on the survey of persistent organic pollutants and apply it in human-biomonitoring. This would facilitate the acquisition of indoor and outdoor pollution with the same receptor.     

Modelling spatial patterns of correlations between concentrations of heavy metals in mosses and atmospheric deposition in 2010 across Europe

Background

This paper aims to investigate the correlations between the concentrations of nine heavy metals in moss and atmospheric deposition within ecological land classes covering Europe. Additionally, it is examined to what extent the statistical relations are affected by the land use around the moss sampling sites. Based on moss data collected in 2010/2011 throughout Europe and data on total atmospheric deposition modelled by two chemical transport models (EMEP MSC-E, LOTOS-EUROS), correlation coefficients between concentrations of heavy metals in moss and in modelled atmospheric deposition were specified for spatial subsamples defined by ecological land classes of Europe (ELCE) as a spatial reference system. Linear discriminant analysis (LDA) and logistic regression (LR) were then used to separate moss sampling sites regarding their contribution to the strength of correlation considering the areal percentage of urban, agricultural and forestry land use around the sampling location. After verification LDA models by LR, LDA models were used to transform spatial information on the land use to maps of potential correlation levels, applicable for future network planning in the European Moss Survey.

Results

Correlations between concentrations of heavy metals in moss and in modelled atmospheric deposition were found to be specific for elements and ELCE units. Land use around the sampling sites mainly influences the correlation level. Small radiuses around the sampling sites examined (5 km) are more relevant for Cd, Cu, Ni, and Zn, while the areal percentage of urban and agricultural land use within large radiuses (75–100 km) is more relevant for As, Cr, Hg, Pb, and V. Most valid LDA models pattern with error rates of <?40% were found for As, Cr, Cu, Hg, Pb, and V. Land use-dependent predictions of spatial patterns split up Europe into investigation areas revealing potentially high (=?above-average) or low (=?below-average) correlation coefficients.

Conclusions

LDA is an eligible method identifying and ranking boundary conditions of correlations between atmospheric deposition and respective concentrations of heavy metals in moss and related mapping considering the influence of the land use around moss sampling sites.

     

Metalle und Stickstoff angereichert in Moosen Sachsens

Background, aim and scope Since 1990 the UN ECE Heavy Metals in Mosses Surveys provide data inventories of the atmospheric heavy metal bioaccumulation across Europe. In the survey 2005 the nitrogen (N) accumulation was measured for the first time in most of the participating countries. In Germany, the surveys were conducted in close cooperation of the relevant authorities of both the Federal Republic and the sixteen states. Therefore, statistical evaluations of the moss survey data with regard to the whole German territory and single federal states are of interest. This article concentrates on Saxony, dealing with the mapping of the spatiotemporal trends of metal accumulation from 1990 to 2005, the spatial patterns of nitrogen accumulation in 2005, and the spatial variability of bioaccumulation due to characteristics of the sampling sites and their surroundings. Exemplified for Cadmium (Cd), Mercury (Hg) and Lead (Pb) the metal loads in mosses are furthermore related to modelled deposition data provided from the European Monitoring and Evaluation Programme (EMEP). Materials and methods In Saxony Pleurozium schreberi (1990, 1995 most frequent moss species, thereafter second most), Hypnum cupressiforme (1990, 1995 second most, thereafter most frequent moss species), Scleropodium purum and Brachytecium rutabulum (1995, 2000) were sampled at up to 83 sites. All sampling sites were described with regard to topographical and ecological characteristics and several criteria to be fulfilled according to the guideline. Together with the measurements this metadata was combined with other information regarding land use in the surroundings of the sampling sites in the WebGIS MossMet. The spatial structure of the metal bioaccumulation was analysed and modelled by variogram analyses and then mapped by applying different kriging techniques. Furthermore, multi metal indices (MMI) were derived for both the sampling sites and raster maps with help of percentile statistics: The MMI_1990–2005 was calculated for arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), titanium (Ti), vanadium (V) and zinc (Zn). The statistical association of the metal bioaccumulation, site specific characteristics as well as information on land use and emissions was analysed by bivariate nonparametric correlation analysis, contingency tables and Classification and Regression Trees (CART). Results The results of the quality controlled chemical analyses show a decrease of the metal bioaccumulation in Saxony from 1990 to 2000. From 2000 to 2005?a significant increase can be stated for As, Cr, Cu, Fe, Ti and V. The element loads of Cd, Hg, Pb and Sb show a decreasing, although non significant, tendency. The MMI_1990–2005 decreased significantly from 1990 to 2000 and increased significantly from 2000 to 2005. The N concentration in mosses in Saxony reaches from 1.36 to 1.96?% in dry mass showing significant correlations to the agriculture density (+), the height of the surrounding trees (+), altitude (–) and the precipitation sum for the accumulation period (–). The ratios of forests around the monitoring sites show a negative correlation to all elements but for Pb, Sb and V. Unlike Cd the moss loads of As, Cr, Cu, Fe, Hg, Ni, Pb, Ti and V are positively correlated to the density of urban areas calculated from the Corine Landcover map 2000. The same holds true for Cr, Cu Fe and Ni regarding traffic density and Cd, Cu, Hg and Ni regarding agricultural density. The precipitation sum within the accumulation period is positively correlated with As, Cd, Cr (1990–2000), Ni, Pb, Sb und V, negatively with Cr (2005), Cu, Fe and Zn. Regarding altitude a similar tendency can be observed. The slope gradient shows significant association to Cd, Cu, Ni and Pb. Regarding the canopy effect negative correlation coefficients were calculated for As, Pb and Sb regarding the distance of the sampling site to the nearest tree crowns and positive correlations were calculated for Cd, Cr, Fe and Sb with respect to the height of the surrounding trees. The distance of the moss site to human settlements is significantly related to As, Cd, Cr, Hg, Ni, Pb and Sb. The impact of traffic becomes apparent for As, Cr, Cu, Ni, Pb, Sb, V and Zn which are all negatively correlated with the distance of the moss site to the nearest road. The multivariate statistical CART analysis identifies the urban land use density in a radius of 5?km around the sampling site as well as the height of surrounding trees as the statistically most significant factors for the Cu concentrations in mosses sampled in 2005. The modelled total deposition of Cd, Hg and Pb (EMEP) and the respective concentrations in Saxon mosses are correlated significantly (1995 Hg: r _s = 0.62, p = 0.004; 2005 Cd: r _s = 0.43, p = 0.07, Hg: r _s = 0.44, p = 0.06, Pb: r _s = 0.39, p = 0,099). Discussion Unlike in e.?g. Baden-Württemberg the metal accumulation in mosses in Saxony increased between 2000 and 2005, Cr thereby increased dramatically. For Cd, Hg and Pb it could be shown that the metal loads in mosses are significantly correlated to the modelled total deposition provided by EMEP. Nevertheless, this does not hold true for all elements in all campaigns. Taking this into account, it can be verified that positive relationships between the metal bioaccumulation and the deposition for Saxony exist. Conclusions Contrary to deposition measurements that exhibit a higher temporal resolution the moss surveys provide measurement data on a wide range of elements. Some of these elements are important with regard to human-toxicological aspects (e.?g. Al, As, Hg, Sb, V). The standardised biomonitoring of atmospheric pollution with mosses is an important link between the technical acquisition of depositions and the accumulation in biological material. To claim that the element concentrations in mosses and in the deposition should correlate to a high degree is not appropriate since both approaches are physically related but are not identical. The degree of correlation thereby depends on the boundary conditions of the physical processes, like regional and site-specific meteorological conditions within the accumulation period, the vertical and horizontal vegetation structure or land use conditions. Recommendations and perspectives The Heavy Metals in Mosses Surveys are a positive example for environmental monitoring activities reaching across three spatial and administrative levels: regional (e.?g. federal state or natural landscape), nation wide (e.?g. Germany) and continental (e.?g. Europe). It can therefore be claimed that the moss survey is the only environmental monitoring network that provides high density and surface covering information on the metal and N exposition of near-natural and agricultural ecosystems. The correlations of the metal bioaccumulation and the modelled deposition should therefore be used to complement the deposition measurement activities across Europe.     

European Critical Loads of Cadmium, Lead and Mercury and their Exceedances

Critical loads of cadmium, lead and mercury were computed by 18 countries of the LRTAP Convention. These national data were collated into a single database for the purpose of identifying sensitive areas in Europe. Computing exceedances, i.e. comparing the critical loads to atmospheric deposition, shows that cadmium was not a widespread risk in 2000, that the risk from lead deposition has decreased since 1990 but was still widespread in 2000, and that the risk from mercury remains high without much change from 1990 to 2000 in most of the countries.