The sensitivity of water chemistry to climate in a forested, nitrogen-saturated catchment recovering from acidification
•We measured fluxes of ions in N-saturated mountain forest catchment from 1998 to 2014.•Water chemistry rapidly recovers from acidification due to 90% reduced S deposition.•Export of base cations, P, organic N, and Al is governed by NO3− and DOC leaching.•NO3− and DOC exports are sensitive to climat...
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Veröffentlicht in: | Ecological indicators 2016-04, Vol.63, p.196-208 |
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Zusammenfassung: | •We measured fluxes of ions in N-saturated mountain forest catchment from 1998 to 2014.•Water chemistry rapidly recovers from acidification due to 90% reduced S deposition.•Export of base cations, P, organic N, and Al is governed by NO3− and DOC leaching.•NO3− and DOC exports are sensitive to climate-related factors and forest damage.•Climate becomes an important variable controlling ionic composition of waters.
Fluxes of major ions and nutrients were measured in the N-saturated mountain forest catchment-lake system of Čertovo Lake (Czech Republic) from 1998 to 2014. The lake has been rapidly recovering from atmospheric acidification due to a 90% decrease in sulphate (SO42−) deposition since the late 1980s and nitrate (NO3−) contribution to the pool of strong acid anion and leaching of dissolved organic carbon (DOC) have increased. Present concentrations of base cations, phosphorus (P), total organic N (TON), and ionic (Ali) and organically bound (Alo) aluminium in tributaries are thus predominantly governed by NO3− and DOC leaching. Despite a continuing recovery lasting 25 years, the Čertovo catchment is still a net source of protons (H+), producing 44mmolm−2yr−1 H+ on a catchment-area basis (corresponding to 35μmolL−1 on a concentration basis). Retention of the deposited inorganic N in the catchment averages 20%, and ammonium consumption (51mmolm−2yr−1) and net NO3− production (28molm−2yr−1) are together the dominant terrestrial H+ generating processes. In contrast, the importance of SO42− release from the soils on terrestrial H+ production is continuously decreasing, with an average of 47mmolm−2yr−1 during the study. The in-lake biogeochemical processes reduce the incoming acidity by ∼40%, neutralizing 23μmolL−1 H+ (i.e., 225mmolm−2yr−1 on a lake-area basis). Denitrification and photochemical and microbial decomposition of DOC are the most important in-lake H+ consuming processes (50 and 39%, respectively), while hydrolysis of Ali (from tributaries and photochemically liberated from Alo) is the dominant in-lake H+ generating process. Because the trends in water chemistry and H+ balance in the catchment-lake system are increasingly related to variability in NO3− and DOC leaching, they have become sensitive to climate-related factors (drought, elevated runoff) and forest damage that significantly modify the leaching of these anions. During the study period, increased exports of NO3− (accompanied by Ali and base cations) from the Čertovo catchment occurred |
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ISSN: | 1470-160X 1872-7034 |
DOI: | 10.1016/j.ecolind.2015.12.014 |