Longitudinal patterns of stream chemistry in a catchment with forest dieback, Czech Republic

Citation
M. Havel et al., Longitudinal patterns of stream chemistry in a catchment with forest dieback, Czech Republic, ENVIR POLLU, 104(1), 1999, pp. 157-167
Citations number
47
Categorie Soggetti
Environment/Ecology
Journal title
ENVIRONMENTAL POLLUTION
ISSN journal
02697491 → ACNP
Volume
104
Issue
1
Year of publication
1999
Pages
157 - 167
Database
ISI
SICI code
0269-7491(1999)104:1<157:LPOSCI>2.0.ZU;2-U
Abstract
Longitudinal streamwater sampling in a 210-ha forested catchment (Jezeri), Czech Republic, was conducted approximately quarterly from August 1992 thro ugh August 1994. The catchment has been severely impacted by atmospheric de position of pollutants and subsequent landscape manipulation for reforestat ion. The impact and landscape manipulations decrease with decreasing elevat ion. The concentration patterns reflect processes and dynamics that are not apparent from long-term monitoring at the basin outlet. Streamwater concen trations of many solutes are highly correlated with elevation, vegetation c over and landscape history. Concentrations of sulphate (SO42-), the dominan t anion, increased downstream. Low SO42- concentrations at the highest elev ations are attributed to a decrease in dry S deposition due to the loss of the forest canopy from Norway spruce dieback and subsequent logging. Furthe rmore, liming and higher moisture content and water movement through the so ils in the headwaters increases S mobility, resulting in lower SO42- concen trations at higher elevations. In contrast, highest nitrate (NO3-) concentr ations (300 mu eq liter(-1)) occurred at the highest elevations, decreased downstream to XO mu eq liter(-1) at the outlet, and the rate of change in c oncentration was the most pronounced in the headwaters. The NO3- pattern is attributed to increased nitrification of the forest floor due to landscape excavation for drainage and reforestation, and liming (dolomitic lime). Th e N demand by 10-25-year-old reforested vegetation at mid elevations (705-8 00 m above sea level) is much greater than in the very young regrowth and o pen areas at the highest elevations, causing concentrations to decrease thr ough this zone. Streamwater NO3- concentrations also vary seasonally due to vegetation demand during the growing season; but high NO3- concentrations (> 50 mu eq liter(-1)) persist at all sites, indicating N saturation. High streamwater calcium (Ca2+) and magnesium (Mg2+) concentrations and low to m oderate alkalinity (ALK) in the limed, deforested and reforested areas also occur, particularly during low runoff periods. ALK and hydrogen ion (H+), fluoride (F-) and dissolved aluminum (Al-DIS) concentrations are highly cor related, particularly H+ and Al-DIS The low streamwater ALK tin 90% of the samples ALK is less than 50 mu eq liter(-1)), moderately low pH tin 45% of the samples pH is less than 5.6) and the correlation with Al-DIS suggests t hat the acid-base status is controlled by inorganic Al and organic complexe s of Al and F. Published by Elsevier Science Ltd.