The GEOMON network of Czech catchments provides long‐term insights into altered forest biogeochemistry: From acid atmospheric deposition to climate change

Abstract

In 1994, a network of small catchments (GEOMON) was established in the Czech Republic to determine input-output element fluxes in semi-natural forest ecosystems recovering from anthropogenic acidification. The network consists from 16 catchments and the primary observations of elements fluxes were complemented by monitoring of biomass stock, element pools in soil and vegetation, and the main water balance components. Over last three decades, reductions of SO 2 , NO x and NH 3 emissions were followed by sulphur (S) and nitrogen (N) deposition reductions of 75% and 30%, respectively. Steeper declines of strong acid anion concentrations compared to cations (Ca, Mg, Na, K, NH 4 ) in precipitation resulted in precipitation pH increase from 4.5 to 5.2 in bulk precipitation and from 4.0 to 5.1 in spruce throughfall. Stream chemistry responded to changes in deposition: S leaching declined. However at majority of catchments soils acted as a net source of S to runoff, delaying recovery. Stream pH increased at acidic streams (pH < 6) and aluminium concentration decreased. Stream nitrate (NO 3 ) concentration declined by 60%, considerably more than N deposition. Stream NO 3 concentration was tightly positively related to stream total dissolved nitrogen to total phosphorus (P) ratio, suggesting the role of P availability on N retention. Trends in dissolved organic carbon fluxes responded to both acidification recovery and to runoff temporal variation. An exceptional drought occurred between 2014 and 2019. Over this recent period, streamflow decreased by ≈ 40% on average compared to 1990s, due to the increases of soil evaporation and vegetation transpiration by ≈ 30% and declines in precipitation by ≈ 15% on average across the elevational gradient. Sharp decreases of stream runoff at catchments <650 m a.s.l. corresponded to areas of recent forest decline caused by bark beetle infestation on drought stressed spruce forests. Understanding of the interactions among legacies of acidification and eutrophication, drought effects on the water cycle and forest disturbance dynamics is requisite for effective management of forested ecosystems under anthropogenic influence.

Assess hydrological responses to a warming climate at the Lysina Critical Zone Observatory in Central Europe

“…Spruce forests in catchments with underlining acidic deposition, where are the groundwater resources typically considered as insignificant, may not survive future climate change conditions due to lack of available water during the drought spells. Oulehle et al (2021) showed negative water balance (using a rough estimation climatic water balance approach in (precipitation minus reference evapotranspiration) during the dry years 2003, 2015 and 2018 in several small forested Norway spruce catchments in the Czech Republic. Such conditions are causing a stress for forest stands.…”

“…Spruce forests in catchments with underlining acidic deposition, where are the groundwater resources typically considered as insignificant, may not survive future climate change conditions due to lack of available water during the drought spells. Oulehle et al (2021) showed negative water balance (using a rough estimation climatic water…”

“…The Lysina catchment is part of the Czech Republic national network GEOMON (GEOchemical MONitoring) of small forest catchments operated by the Czech Geological Survey (Fottová, 1995; Oulehle et al, 2021). The Lysina Catchment is one of two Czech sites within International Cooperative Program ‐ Integrated Monitoring network (Forsius et al, 2021).…”

Changes and dynamics of headwaters chemistry on the boundary of nature protected areas: Example of upper Blanice River catchment, Czechia

“…The acidification of precipitation has significantly affected the composition of soils. As a result, increased soil acidity reduces the microorganism's activity, causes calcium leaching and has negative effect on both plant resistance and consequently water quality (Oulehle et al 2021). Since the early 1990s, water quality in Czechia has improved due to changes in industrial and municipal practices (Langhammer 2010;Chalupová, Havlíková, Janský 2012).…”

Mercury cycling during acid rain recovery at the forested Lesní potok catchment, Czech Republic

“…The site of the present study, Lesní potok, has been the focus of biogeochemical research since 1993 (Skrivan et al, 1993). Lesní potok is one of 14 catchments in the Czech GEOMON network (Oulehle et al, 2021) and thus has been part of several cross-site comparisons (Bohdalkova et al, 2014;Fottov a & Skorepov a, 1998;Nov ak et al, 2005Nov ak et al, , 2010Oulehle et al, 2008Oulehle et al, , 2017Oulehle et al, , 2021. The catchment is well-characterized in terms of its physical properties (soils, geology, vegetation, hydrology;Janoušek et al, 2014;Navr atil et al, 2003).…”