Catchment features controlling nitrogen dynamics in running waters above the tree line (central Italian Alps)

Abstract

Abstract. The study of nitrogen cycling in mountain areas has a long tradition, as it was applied to better understand and describe ecosystem functioning, as well as to quantify long-distance effects of human activities on remote environments. Nonetheless, very few studies, especially in Europe, have considered catchment features controlling nitrogen dynamics above the tree line with focus on running waters.In this study, relationships between some water chemistry descriptors -including nitrogen species and dissolved organic carbon (DOC) -and catchment characteristics were evaluated for a range of sites located above the tree line (1950-2650 m a.s.l.) at Val Masino, in the central Italian Alps. Land cover categories as well as elevation and slope were assessed at each site. Water samples were collected during the 2007 and 2008 snow free periods, with a nearly monthly frequency. In contrast to dissolved organic nitrogen, nitrate concentrations in running waters showed a spatial pattern strictly connected to the fractional extension of tundra and talus in each basin. Exponential models significantly described the relationships between maximum NO 3 and the fraction of vegetated soil cover (negative relation) and talus (positive relation), explaining almost 90 % of nitrate variation in running waters. Similarly to nitrate but with an opposite behavior, DOC was positively correlated with vegetated soil cover and negatively correlated with talus. Therefore, land cover can be considered one of the most important factors affecting water quality in high-elevation catchments with contrasting effects on N and C pools.

Dissolved organic nitrogen (DON) in seventeen shallow lakes of Eastern China

“…NO 3 -is often immobilized by microbial and plant uptake during the warmer months, while biological uptake and transformation of NO 3 -is highly reduced during the colder months due to the weaker ability of retaining NO 3 - (Black et al 1993;Edwards et al 1985;Balestrini et al 2013). However, in our data, no similar variation in concentrations was observed during different reasons.…”

“…Many studies of DON sources have focused on N cycling altered dramatically by human activities such as land use (Taylor et al 2005;Flint and Davis 2007;Balestrini et al 2013), which increase the rate of transformation from N 2 into reactive nitrogen (RN). Soil types and land use also could affect NH 4 ?…”

Macroinvertebrate communities in spring-fed alpine source pools

“…The major ion concentrations in the springs and source pools were very low with conductivities below 10 lS cm -1 , similar to previously reported Australian alpine waters (Silvester, 2009;Green, 2012;Chang et al, 2014) as well as some alpine spring waters in Europe (Balestrini et al, 2014;Wojtal et al, 2014) and in the Himalayas (Balestrini et al, 2013). The ionic concentrations are also very similar to the Mt Kosciuszko lakes (Williams et al, 1970) and of regional rainfall in south-east Victoria (Hutton & Leslie, 1958;Dean et al, 2014) suggesting that the groundwater recharge water is not strongly modified by rock interactions.…”

Water and solute dynamics during rainfall events in headwater catchments in the Central Swiss Alps under the influence of green alder shrubs and wetland soils

“…Mean DOC concentrations during base flow conditions were in general relatively low (0.6 to 1.8 mg l −1 ), which is comparable to headwater catchments in the Prealps of Central Switzerland (Hagedorn et al ., ) and the Italian Alps (Balestrini et al ., ). In Chämleten, the DOC concentrations were significantly higher than in the other catchments ( p < 0.0001, n = 51).…”