Raffaella Balestrini

Wet and dry atmospheric deposition at prealpine and alpine sites in northern Italy

Abstract Modified wet and dry samplers that use a water surface to collect dry deposition were used in a pluriannual field campaign in five sites in alpine and prealpine areas of Lombardy (Italy). SO 4 2− , NO 3 − , Cl − and NH 4 + concentrations in rainfall increased from north to south; the southern area being closest to industrialised areas of the Po Valley. In dry deposition the spatial pattern of sulphur and nitrogen species was ostensibly linked to local pollution sources. In winter, the SO 4 2− concentration in dry deposition samples from Morbegno (urban) and Longone (semi-urban) was about 3 times that in summer in association with low pH, explained as due to a higher rate of SO 2 dissolution in winter followed by oxidation to sulphuric acid. The dry deposition of Ca 2+ , Mg 2+ and K + formed 41–60, 35–64 and 57–67% of the total flux, respectively; furthermore 25–50% of total SO 4 2− , 21–37% of total NH 4 + , and 23–31% of total NO 3 − came from dry deposition. Only at the remote high-altitude site was the dry deposition of these species insignificant. The sum of the wet and dry deposition rates indicated that current nitrogen loads exceed the nutrient critical loads by several kgxa0Nxa0ha −1 at all investigated sites. Measured nitrogen loads at Longone and Castione (rural) were about 4 times higher than critical values.

Atmospheric deposition and canopy exchange processes in alpine forest ecosystems (northern Italy)

Abstract Throughfall and bulk precipitation chemistry were studied for five years (June 1994–May 1999) at two high elevation forest sites (Val Gerola and Val Masino) which were known to differ in terms of tree health, as assessed by live crown condition. The ion concentration of bulk precipitation samples did not differ significantly between sites, except for Mg2+, while the throughfall concentrations differed in the measured values of H+, N-NO3−, Cl−, Na+, K+, DOC and weak organic acids. The results of the application of the canopy exchange model indicated a higher contribution from the dry deposition of N-NO3−, N-NH4+ and H+ at Val Gerola, where the damage symptoms were more evident. In addition, the canopy leaching of Ca2+, K+ and weak organic acids were 47%, 21% and 27% higher at Val Gerola than at Val Masino. Annual SO42− deposition fluxes (21.3xa0kg ha−1xa0yr−1 at Val Masino and 23.6xa0kgxa0ha−1xa0yr−1 at Val Gerola) were similar to those reported for moderately polluted European and U.S. sites. Annual N loads were 13.6 and 13.1xa0kgxa0ha−1xa0yr−1 in the bulk input, and 15.0 and 18.0xa0kgxa0ha−1xa0yr−1 in throughfall inputs, at Val Masino and Val Gerola, respectively. The contribution of the organic fraction to the total N atmospheric deposition load is significant, constituting 17% of the bulk flux and 40% of the throughfall flux. Measured nitrogen loads exceed the critical nutrient loads by several kgxa0Nxa0ha−1 at both stations. In particular the nitrogen throughfall load at Val Gerola was about 3 times higher than the critical values.

Characterising hydromorphological features of selected Italian rivers: a comparative application of environmental indices

The purpose of this study was to test the applicability of different methods of river habitat assessment and their respective indices in a series of sample sites in Italy. These investigations were carried out within the EU AQEM project with the aim of combining the macroinvertebrate information with that achieved by investigating the hydromorphological characteristics of the river ecosystem as well as the surrounding landscape features. The River Habitat Survey (including the derived indices Habitat Modification Score and Habitat Quality Assessment) from U.K., and three Italian indices (Index of Fluvial Functioning, Buffer Strip Index and Wild State Index) were applied at 33 AQEM sites distributed in three different Italian river types. The obtained results indicate the overall ability of the applied indices to detect the degradation gradient, including river morphology and habitat, in the studied riverine ecosystems. Index of Fluvial Functioning seems useful to promptly describe the ecological quality of rivers as suggested by the good correlation with the AQEM multimetric biotic index. The Buffer Strip Index, showing a clear affinity with the Habitat Quality Assessment, seems suitable to assess richness and quality of the physical structure of a riverine site. The Habitat Modification Score recorded efficiently the morphological impact where present (e.g., North Apennine river sites), while the Italian indices appear to be not appropriate for differentiating this impact type from the general degradation of rivers.

The validation of common European class boundaries for river benthic macroinvertebrates to facilitate the intercalibration process of the Water Framework Directive

The Water Framework Directive (WFD) requires that all the water bodies in Europe be protected and enhanced to achieve Good Ecological Status by 2015. The intercalibration of the biological monitoring results of Member States has to be carried out in relation to classification tasks to guarantee a common understanding of ‘Good Ecological Status’ at a European level. An intercalibration exercise was carried out within the framework of different Geographical Intercalibration Groups (GIGs), each composed of a group of countries that share similar river types and have a discrete geographical range. By means of the intercalibration exercise, common European boundaries were proposed for river invertebrate assessment methods within each GIG. The purpose of this study was to validate the boundaries proposed for the formal intercalibration exercise. A benchmark data set was used, which comprised data, collected in different European countries that satisfied WFD requirements. The data set included a set of reference sites and provided evidence of a high degree of comparability among countries. The STAR Intercalibration Common Metric index (STAR_ICMi) was calculated for benchmark samples and was selected as the index in which national assessment boundaries were expressed. It was applied for the intercalibration exercise in two GIGs. For the STAR_ICMi, the coefficient of variation was also calculated, demonstrating a comparable variability with indices that are based on species level identification. A fixed percentile of reference samples STAR_ICMi values was selected as the boundary between High and Good status. The range from this fixed percentile to the lowest possible value was divided into four equal parts to obtain the remaining class boundaries. The resulting High/Good and Good/Moderate boundaries were compared to the boundaries proposed by GIGs and proved to be in line with those defined in the intercalibration exercise. Even if, for the intercalibration exercise, some procedures to check the Member States (MS) data sets where put into practice, it is the responsibility of each state to guarantee the WFD compliancy of their reference conditions and methods. Accordingly, the process of validation explained in this article, or similar ones, can be an important step forward and demonstrate the comparability of the actual boundaries.

Interannual Variability of Soil N and C Forms in Response to Snow—Cover duration and Pedoclimatic Conditions in Alpine Tundra, Northwest Italy

ABSTRACT In alpine tundra the influence of snow-cover duration (SCD) and pedoclimatic conditions on soil nutrient forms during the growing season has received little attention. The hypothesis that SCD influences the soil temperature, which in turn can affect the annual changes in topsoil nitrogen (N) and carbon (C) forms, was tested for five growing seasons at three study sites in the alpine tundra of the NW Italian Alps. Among the pedoclimatic conditions studied (soil temperature, soil moisture, and number of freeze/thaw cycles), the mean soil temperature of the growing season was inversely correlated with the SCD (p < 0.01), which ranged from 216 to 272 days. Independently from the soil characteristics (e.g., degree of evolution), the microbial carbon (Cmicr) of the growing season was inversely correlated with the SCD and the mean soil temperature of the snow-covered season, suggesting the consumption of soil resources made by the Cmicr under the snowpack. During the growing season ammonium (N-NH4+), dissolved organic carbon (DOC), and Cmicr were positively correlated with soil temperature and moisture. Path analysis shows that the interannual variability of topsoil N and C forms was significantly controlled by the pedoclimatic conditions recorded in both the snow-covered and the subsequent growing seasons, which in turn were influenced by SCD. Therefore, SCD played a fundamental role in terms of pedoclimatic conditions during the growing season, contributing to explaining the interannual variability of soil N and C forms, and may be a key factor for predicting the nutrient cycling in alpine tundra in the context of a changing climate.

Detecting the impact of bank and channel modification on invertebrate communities in Mediterranean temporary streams (Sardinia, SW Italy).

We hypothesized that reach-scale, bank and channel modification would impact benthic communities in temporary rivers of Sardinia, when pollution and water abstraction are not relevant. A range of variables were considered, which include both artificial structures/alterations and natural features observed in a stream reach. Multivariate regression trees (MRT) were used to assess the effects of the explanatory variables on invertebrate assemblages and five groups, characterized by different habitat modification and/or features, were recognized. Four node variables determined the splits in the MRT analysis: channel reinforcement, tree-related bank and channel habitats, channel modification and bank modification. Continuity of trees in the river corridor diverged among MRT groups and significant differences among groups include presence of alders, extent of channel shading and substrate diversity. Also, the percentage of in-stream organic substrates, in particular CPOM/Xylal, showed highly significant differences among groups. For practical applications, thresholds for the extent of channel reinforcement (40%) and modification (10%) and for bank alteration (≈30%) were provided, that can be used to guide the implementation of restoration measures. In moderately altered river reaches, a significant extent of tree-related habitats (≈5%) can noticeably mitigate the effects of morphological alteration on aquatic invertebrates. The outcomes highlight the importance of riparian zone management as an opportune, achievable prospect in the restoration of Mediterranean temporary streams. The impact of bank and channel modification on ecological status (sensu WFD) was investigated and the tested benthic metrics, especially those based on abundance data, showed legible differences among MRT groups. Finally, bank and channel modification appears to be a potential threat for the conservation of a few Sardo-Corsican endemic species. The introduction of management criteria that openly use information on endemic species seems crucial to reduce the risk of improving overall ecological status while depleting biodiversity.