[Show abstract][Hide abstract] ABSTRACT: Mountain forests in National park Bohemian Forest (Czech Republic) were affected by bark beetle attack and windthrows in 2004–2008, followed by an extensive tree dieback. We evaluated changes in the biochemistry of the uppermost soil horizons with the emphasis on carbon (C) and nitrogen (N) cycling in a near-natural spruce (Picea abies) mountain forest after the forest dieback, and compared it with an undisturbed control plot of similar age, climate , elevation, deposition, N-saturation level, and land use history. We hypothesised that the high litter input after forest dieback at the disturbed plot and its consequent decomposition might influence the availability of C for microorganisms, and consequently, N transformations in the soil. The concentrations of dissolved organic C (DOC) and N (DON) in soil water extracts rapidly increased at the disturbed plot for 3 yeas and then continually decreased. Net ammonification exhibited a similar trend as DOC and DON, indicating elevated mineralization. Despite the high ammonium concentrations found after the forest die-back (an increase from 0.5 mmol kg-1 to 2–3 mmol kg-1), net nitrification was stable and low during these 3 years. After the DOC depletion and decrease in microbial biomass 5 years after the forest dieback, net nitrification started to rise, and nitrate concentrations increased from 0.2–1 mmol kg-1 to 2–3 mmol kg-1. Our results emphasize the key role of the availability of organic C in microbial N transformations, which probably promoted microbial heterotro-phic activity at the expense of slow-growing nitrifiers.
PLoS ONE 07/2015; 10(7). DOI:10.1371/journal.pone.0134165 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Glacial lakes in the Bohemian Forest (Šumava, Böhmerwald) belong to the most atmospherically acidified lake districts in the world. Available historical data and regular monitoring (since 1984) provide a valuable background for long-term ecological research of the catchment–lake ecosystems. This paper is an overview of recent projects covering the last two decades. The review of published papers provides details on the organization and aims of present research on the Bohemian Forest lakes that currently focuses on chemical and biological recovery of the catchment–lake systems from atmospheric acidification, and effects of climate change and forest vigour on biogeochemical processes in terrestrial and aquatic ecosystems.
[Show abstract][Hide abstract] ABSTRACT: Using relationships between the composition of precipitation and emission rates of sulphur and nitrogen compounds and dust from 1978 to 2012, we modelled concentrations of sulphate, nitrate, ammonium, chloride, and base cations and pH of precipitation in the Tatra Mountains (central Europe) back to 1900. The modelled precipitation chemistry exhibited a high degree of temporal coherence with the lake water chemistry in 1937 and during the period 1984–2014. The ionic composition of lake water reflected progress in their acidification until the late 1980s, and then a rapid recovery. The response of lake water chemistry to changes in precipitation chemistry differed for individual ions, nutrients, and among lakes, predominantly reflecting the proportions of soil in their catchments. Important differences occurred in nutrient concentrations. In-lake concentrations of dissolved organic carbon (DOC) and total organic nitrogen (TON) exhibited inverse patterns to nitrate. DOC and TON were higher in lakes with a higher proportion of soil in the catchments, and increased in many lakes during recovery from acidification, while nitrate concentrations were higher and decreased most steeply in the catchments with sparse soils. Lake water concentrations of total phosphorus (TP) were spatially similar to that of DOC and TON, but increased most steeply during recovery in lakes with a high proportion of till soils. Our results indicate that chemical recovery of mountain ecosystems is seriously modified by catchment biogeochemistry and may result not only in elevated DOC leaching, but also in an increase of terrestrial export of TON and TP to the receiving surface waters.
[Show abstract][Hide abstract] ABSTRACT: Purpose Numerous extraction procedures have been used to characterize phosphorus (P) forms bound to iron (Fe) and aluminum (Al) (hydr)oxides in soils and sediments. We propose a simple modification of a widely used P fractionation method that more precisely quantifies P associated with active Fe and Al (hydr)oxides, which are mostly responsible for P binding and its potential release to water. Materials and methods We modified the original sequential extraction [H2O, bicarbonate-dithionite (BD), NaOH, HCl] by adding short (10-min) extractions with BD and NaOH prior to the respective original steps. The method was verified using (1) dissolution kinetics of Fe and Al minerals of different crystallinity and (2) liberation of P, Fe, and Al from natural samples of soils, sediments, and settling seston, containing different proportions of amorphous and crystalline Fe and Al (hydr)oxides. Extracted P was analyzed for reactive and non-reactive (mostly organic) P forms. Results and discussion Both mineral and organic P forms associated with Fe and Al were almost completely liberated from the samples during the 10-min BD and NaOH extractions, respectively. Prolonged extraction period caused a partial P re-adsorption onto the solid phase in some samples. The 10-min extractions were able to dissolve amorphous Fe and Al (hydr)oxides (ferrihydrite, amorphous AlOOH) and a portion of more crystalline Fe and Al minerals, approximately related to their surface area. Conclusions The additional short extraction steps allow a rapid and more precise quantification of P associated with active Al and Fe (hydr)oxides, and better estimate the amounts of these Fe and Al forms in soils and sediments than the original method. Our simple modification of the traditional method thus provides new and useful information for environmental studies focused on potential P mobility across a solid phase-water interface.
Journal of Soils and Sediments 07/2015; 15(7). DOI:10.1007/s11368-015-1119-1 · 2.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Nitrogen (N) deposition is globally considered as a major threat to ecosystem functioning with important consequences for biodiversity, carbon sequestration and N retention. Lowered N retention as manifested by elevated concentrations of inorganic N in surface waters indicates ecosystem N saturation. Nitrate (NO3) concentrations in runoff from semi-natural catchments typically show an annual cycle, with low concentrations during the summer and high concentrations during the winter. Process-oriented catchment-scale biogeochemical models provide tools for simulation and testing changes in surface water and soil chemistry in response to changes in sulphur (S) and N deposition and climate. Here we examine the ability of MAGIC to simulate the observed monthly as well as the long-term trends over 10–35 years of inorganic N concentrations in streamwaters from four monitored headwater catchments in Europe: Čertovo Lake in the Czech Republic, Afon Gwy at Plynlimon, UK, Storgama, Norway and G2 NITREX at Gårdsjön, Sweden. The balance between N inputs (mineralization + deposition) and microbial immobilization and plant uptake defined the seasonal pattern of NO3 leaching. N mineralization and N uptake were assumed to be governed by temperature, described by Q10 functions. Seasonality in NO3 concentration and fluxes were satisfactorily reproduced at three sites (R2 of predicted vs. modelled concentrations varied between 0.32 and 0.47 and for fluxes between 0.36 and 0.88). The model was less successful in reproducing the observed NO3 concentrations and fluxes at the experimental N addition site G2 NITREX (R2 = 0.01 and R2 = 0.19, respectively). In contrast to the three monitored sites, Gårdsjön is in a state of change from a N-limited to N-rich ecosystem due to 20 years of experimental N addition. At Gårdsjön the measured NO3 seasonal pattern did not follow typical annual cycle for reasons which are not well understood, and thus not simulated by the model.
Science of The Total Environment 06/2015; DOI:10.1016/j.scitotenv.2015.05.047 · 4.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Good understanding of forest productivity and carbon (C) storage capacity is essential for better understanding of C dynamics and climate modeling. Studies of old-growth forest C dynamics from central and eastern Europe are rare and the few remaining pristine forests represent a unique opportunity to study natural forest dynamics in an otherwise managed landscape. We studied protected old-growth Norway spruce (Picea abies L.) stands in the Bohemian Forest, Czech Republic, to explore total ecosystem C pool (live and dead biomass and soil) variability in forest ecosystem as a function of stand age and elevation. These old-growth forest ecosystems store very high amounts of C, up to 570 t C ha -1 , and 393 t C ha -1 on average. Live biomass is the dominant C pool followed by mineral soil, forest floor and dead biomass. We found that total C significantly decreased with increasing elevation (1025–1338 m a.s.l) from 456 to 294 t C ha -1 , predominantly driven by decreases in live biomass and forest floor C pools. Significant changes take place in individual pools based on age and elevation gradients, but total C was not significantly different between stands age 116–145 years. Contrary to some recent findings that old-growth forest ecosystems continue to sequester C long after maturity, our data supports the hypothesis that old-growth forests reach a steady state and become C neutral. They accumulate same amount of C through photosynthesis than is lost by decay and leaching. This study provides a detailed overview of C pools of old-growth Bohemian Forests and highlights the importance of including all major C pools in forest ecosystem C studies.
[Show abstract][Hide abstract] ABSTRACT: We investigated litterfall chemistry and fluxes, and cellulose decomposition in litter floor in mature, unmanaged Norway spruce stands in the catchments of Plešné and Čertovo lakes (Czech Republic) during 2003–2013. The Plešné forest was infested by the bark beetle (Ips typographus) in 2004, and 88%–99% of trees had died by 2011. Total litterfall and its composition were similar in both catchments in 2003. The litterfall increased from 5.4 to 42 t ha−1 yr−1 after the infestation and remained relatively high (5.0 t ha−1 yr−1) until the end of the study even though > 52% of trees were already broken. The chemical composition of most spruce litter categories changed after infestation, with the most pronounced trends in C (decrease) and Ca (increase) concentrations. Moreover, Mg, K, and P concentrations increased in the total Plešné litter due to an increasing proportion of rowan litter. Cellulose decomposition increased in the litter floor after infestation.
Boreal Environment Research 06/2015; 20(3):305-323. · 1.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The photochemical release of inorganic nitrogen from dissolved organic matter is an important source of bio-available nitrogen (N) in N-limited aquatic ecosystems. We conducted photochemical experiments and used mathematical models based on pseudo-first-order reaction kinetics to quantify the photochemical transformations of individual N species and their seasonal effects on N cycling in a mountain forest stream and lake (Plešné Lake, Czech Republic). Results from laboratory experiments on photochemical changes in N speciation were compared to measured lake N budgets. Concentrations of organic nitrogen (Norg; 40-58 µmol L-1) decreased from 3 to 26% during 48-hour laboratory irradiation (an equivalent of 4-5 days of natural solar insolation) due to photochemical mineralization to ammonium (NH4+) and other N forms (Nx; possibly N oxides and N2). In addition to Norg mineralization, Nx also originated from photochemical nitrate (NO3-) reduction. Laboratory exposure of a first-order forest stream water samples showed a high amount of seasonality, with the maximum rates of Norg mineralization and NH4+ production in winter and spring, and the maximum NO3- reduction occurring in summer. These photochemical changes could have an ecologically significant effect on NH4+ concentrations in streams (doubling their terrestrial fluxes from soils) and on concentrations of dissolved Norg in the lake. In contrast, photochemical reactions reduced NO3- fluxes by a negligible (<1%) amount and had a negligible effect on the aquatic cycle of this N form.
PLoS ONE 12/2014; 9(12):e116364. DOI:10.1371/journal.pone.0116364 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mountain lakes in the Bohemian Forest, on both the Czech and German sides, were atmospherically acidified mainly in the 1960s–1980s and have since been recovering from acidification. In 2007, we performed the first complete study on littoral macroinvertebrates in all eight lakes. The goals of the study were to 1) compare macroinvertebrates in the lakes during the process of recovery and 2) investigate relations between the occurrence of taxa and water chemistry. Lake water pH varied from 4.6 to 5.7, concentrations of dissolved reactive Al and labile Al ranged from 118–601 and 11–470 μg l-1, respectively, and DOC concentrations were <6 mg l-1. Altogether 73 taxa were identified from all lakes; a positive relationship was found between pH and the number of macroinvertebrate taxa. The highest number of taxa was found in the least acidic lakes Laka and Grosser Arbersee, including the mollusk Pisidium casertanum. In contrast, the lowest diversity was found in the most acidified Čertovo jezero. Cluster analyses of macroinvertebrates and water chemistry suggested pH as the key factor influencing the occurrence of macroinvertebrate taxa. An interesting finding was the occurrence of the boreo-montane water beetle Nebrioporus assimilis in Prášilské jezero, which is the first documented record of this species in the Czech Republic since 1960.
[Show abstract][Hide abstract] ABSTRACT: Using data on long-term monitoring of water quality, mass budgets, and empirical models, we quantified chloride (Cl) leaching from major diffuse and point sources in a large central European catchment (upper Vltava river, Czech Republic) over a 110-year period (1900–2010), with the major aim to evaluate the influence of historical changes in land use and management practices on Cl leaching from agricultural land. The Cl input to farmland in synthetic fertilizers, livestock feed, and atmospheric deposition tripled in the 1950s–1980s (from 23 to 64 kg ha−1 year−1 on average), and then abruptly decreased to ~14 kg ha−1 year−1 during 1990–2010. The proportion of drained agricultural land rapidly increased from 4 % in the 1950s to its maximum of 43 % in the 1990s. Until the 1950s, the Cl leaching from agricultural land followed a simple dose–response function. Then, agricultural soils retained on average 16 ± 4 kg ha−1 year−1 of Cl during 1959–1985, when the most important changes in land use and management practices occurred, and subsequently became a net Cl source of 11 ± 3 kg ha−1 year−1 on average during 1986–2010, when Cl input to soils declined and drainage of new land ceased. Our data suggest that the temporal changes in the Cl storage in agricultural land are associated with changes in Cl concentrations in both permanent soil water and soils. Physico-chemical conditions in freshly drained soils, namely elevated aeration and high concentrations of soil organic matter (SOM), and high Cl inputs probably resulted in a Cl immobilization in soils by formation of organic chlorine (Clorg) and adsorption that was higher than the Cl production from Clorg mineralization and desorption. In contrast, Clorg mineralization and Cl desorption exceeded the Cl retention during the consecutive period of low Cl inputs and decreasing SOM concentrations in agricultural soils. Our study implies that changes in land use and agricultural management can significantly affect dose–response functions even for Cl, which is traditionally considered and modelled as a conservative ion.
[Show abstract][Hide abstract] ABSTRACT: Anthropogenically derived nitrogen (N) has a central role in global environmental changes, including climate change, biodiversity loss, air pollution, greenhouse gas emission, water pollution, as well as food production and human health. Current understanding of the biogeochemical processes that govern the N cycle in coupled human-ecological systems around the globe is drawn largely from the long-term ecological monitoring and experimental studies. Here, we review spatial and temporal patterns and trends in reactive N emissions, and the interactions between N and other important elements that dictate their delivery from terrestrial to aquatic ecosystems, and the impacts of N on biodiversity and human society. Integrated international and long-term collaborative studies covering research gaps will reduce uncertainties and promote further understanding of the nitrogen cycle in various ecosystems.
AMBIO A Journal of the Human Environment 07/2014; DOI:10.1007/s13280-014-0545-4 · 2.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We examined long-term data on water chemistry of Lake Rachelsee (Germany) following the changes in acidic depositions in central Europe since 1980s. Despite gradual chemical recovery of Rachelsee, its biological recovery was delayed. In 1999, lake recovery was abruptly reversed by a coincident forest die-back, which resulted in elevated terrestrial export of nitrate and ionic aluminum lasting ~5 years. This re-acidification episode provided unique opportunity to study plankton recovery in the rapidly recovering lake water after the abrupt decline in nitrate leaching from the catchment. There were sudden changes both in lake water chemistry and in plankton biomass structure, such as decreased bacterial filaments, increased phytoplankton biomass, and rotifer abundance. The shift from dominance of heterotrophic to autotrophic organisms suggested their substantial release from severe phosphorus stress. Such a rapid change in plankton structure in a lake recovering from acidity has, to the best of our knowledge, not been previously documented.
AMBIO A Journal of the Human Environment 02/2014; 43(2):207-217. DOI:10.1007/s13280-013-0415-5 · 2.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ionic and nutrient compositions of tributaries to Plešné Lake (PL, 4 inlets, granite bedrock) and Čertovo Lake (CT, 7 inlets, mica schist and quartzite bedrock) were analyzed in 3-week intervals from October 1997 to November 2012. Norway spruce stands, dominating both catchments, were damaged during this study: 93% of the PL mature trees died due to bark beetle infestation between 2004–2011; 14% of the CT forest was seriously damaged by windthrows and bark beetle in 2007–2011. Almost all dead biomass remained in the catchments. Prior to the forest damage, water chemistry of tributaries exhibited trends typical for areas recovering from strong atmospheric acidification, such as decreasing concentrations of strong acid anions, base cations, ionic aluminium (Al i), and protons (increasing pH). Chemistry of tributaries draining the af-fected sub-catchments rapidly changed after the forest damage. Concentrations of nitrate immediately in-creased, reaching the maximum values (up to 350 μmol.l –1) within 3–6 years after the forest dieback, then started to decline. Nitrate became the dominant anion and its leaching was accompanied by similar trends in Al i and potassium (K +) concentrations, and decreasing pH. Increases in magnesium (Mg 2+) and calcium (Ca 2+) leaching were less steep than those of Al i and K + , but continued at elevated rates until the end of the study. The elevated leaching of phosphorus (P) and dissolved organic carbon (DOC) and nitrogen (DON) occurred immediately after forest dieback. The DON concentrations increased more steeply than DOC, resulting in decreasing DOC:DON ratios. Because almost no biomass was removed from the damaged fo-rest, leaching of K +
[Show abstract][Hide abstract] ABSTRACT: Using dynamic, mass budget, and empirical models, we quantified sulphate-sulphur (SO4-S) leaching from soils in a large central European catchment (upper Vltava river, Czech Republic) over a 110-year period (1900-2010). SO4-S inputs to soils with synthetic fertilisers and atmospheric deposition increased in the 1950s-1980s, then rapidly decreased (~80%), and remained low since the middle 1990s. The proportion of drained agricultural land rapidly increased from 4 to 43% between the 1950s and 1990s; then the draining ability of the system slowly decreased due to its ageing. Sulphate concentrations in the Vltava exhibited similar trends as the external SO4-S inputs, suggesting that they could be explained by changes in atmospheric and fertiliser S inputs. The available data and modelling, however, showed that (i) internal SO4-S sources (mineralization of soil organic S in the drained agricultural land), (ii) a hysteresis in SO4-S leaching from forest soils (a net S retention at the high S inputs and then a net release at the lowered inputs), and (iii) hydrology must be taken into account. An empirical model was then employed, based on parameters representing hydrology (discharge), external SO4-S sources (inputs by synthetic fertilisers and atmospheric deposition), and internal SO4-S sources (mineralization related to soil drainage). The model explained 84% of the observed variability in annual SO4-S concentrations in the Vltava river during 1900-2010 and showed that forest soils were a net sink (105kgha(-1)) while agricultural land was a net source (55kgha(-1)) of SO4-S during 1960-2010. In the late 1980s, forest soils changed from a sink to a source of S, and the present release of SO4-S accumulated in forest soils thus delays recovery of surface waters from acidification, while S losses from agricultural soils increase the risk of future S deficiency in S-demanding crops.
Science of The Total Environment 10/2013; 470-471C:543-550. DOI:10.1016/j.scitotenv.2013.10.013 · 4.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Using mass budget and hydrological models, we quantified the contribution of major diffuse nitrogen (N) sources to surface water loading in a large heterogeneous catchment (upper Vltava river, Czech Republic, about 13,000 km2) over the last 52 years. The catchment reflects the typical development in central and eastern European countries, which witnessed socio-economic shifts from a market to a planned economy in the 1950s and back to a market economy in the 1990s. The former shift was accompanied by increasing N inputs to agricultural and forest areas with ranges for the 1950–1980s of 60–160 and 14–30 kg ha−1 year−1, respectively, and with intensive draining of waterlogged farmland. The shift in the 1990s resulted in ~40 and ~50 % reduction of N inputs to agricultural areas and forests, respectively, and farmland draining ceased. The N exports from agricultural land (E
) and from forests (E
) varied within 3–45 and 1.6–7.1 kg ha−1 year−1, respectively (with maxima in the 1980s). The E
fluxes exhibited several similar patterns, being dominated by NO3-N, increasing with N inputs, and having similar inter-annual variability related to hydrology. The N losses from forests were stable (19 % of N input on average), while those from agricultural land increased from ~10 % in the 1960s up to 32 % in the 2000s, due probably to the previous extensive drainage and tillage of waterlogged fields and pastures. These land use changes reduced the water residence time in agricultural land and induced mineralization of soil organic matter. Continuing mineralization of soil organic N pools thus was the most probable reason for the remaining high E
fluxes despite a ~40 % reduction in N inputs to agricultural land, while the E
fluxes decreased proportionally to the decreasing N deposition during 1990–2010.
[Show abstract][Hide abstract] ABSTRACT: In some of the eight glacial lakes in the Bohemian Forest we have observed first signs of zooplankton reco- very from acidity. The recovery has followed a drop in atmospheric sulphur and nitrogen deposition and consequent reversal in water chemistry of the lakes during the last decade. At present, stable populations of Ceriodaphnia quadrangula have returned to Lake Černé and Prášilské, and two circumneutral rotifers have recently occurred in the lakes with positive alkalinity: Laka, Großer Arbersee (Keratella testudo) and Kleiner Arbersee (K. valga). Moreover, in the mesotrophic, strongly acidified Lake Plešné, we documented increase in both phytoplankton and planktonic rotifers during the 1990s. A statistical comparison of seaso- nal data (1994, 1998, 2001 and 2003; Kruskal-Wallis test) showed a significant increase in pH and a signi- ficant drop in total reactive aluminium (Al T ). In parallel, a significant increase in chlorophyll a concentra- tion suggested the recovery of phytoplankton. In consequence, summer abundance of planktonic rotifers in Lake Plešné rose by more than two orders of magnitude during the 1990s.
[Show abstract][Hide abstract] ABSTRACT: We evaluated changes in the chemistry of the uppermost soil horizons in an unmanaged spruce forest (National Park Bohemian Forest, Czech Republic) for 3 years after dieback caused by a bark beetle infestation, and compared these changes with a similar undisturbed forest area. The soils below the disturbed forest received 2–6 times more elements via litter fall compared to the unaffected plot. The subsequent decomposition of litter and reduced nutrient uptake by trees resulted in a steep increase in soil concentrations of soluble N (NH4-N, organic-bound N) and P forms in the disturbed plot. The average concentrations of NH4-N and soluble reactive P increased from 0.8 to 4.4 mmol kg−1 and from 0.04 to 0.9 mmol kg−1, respectively, in the uppermost soil horizon. Decomposition of litter at the disturbed plot elevated soil concentrations of Ca2+, Mg2+ and K+, which replaced Al3+ and H+ ions from the soil sorption complex. Consequently, soil concentrations of exchangeable base cations increased from 120 to 200 meq kg−1, while exchangeable Al3+ and H+ decreased 66 and 50 %, respectively, and soil base saturation increased from 40 to 70 %. The Al3+ liberation did not elevate concentrations of ionic Al in the soil solution, because most of the liberated Al3+ was rapidly complexed by dissolved organic carbon (DOC) and transformed to DOC–Al complexes. The chemical parameters investigated at the unaffected plot remained stable during the study.
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[Show abstract][Hide abstract] ABSTRACT: Elevated and chronic nitrogen (N) deposition to N-limited terrestrial ecosystems can lead to ‘N saturation’, with resultant ecosystem damage and leaching of nitrate (NO3 −) to surface waters. Present-day N deposition, however, is often a poor predictor of NO3 − leaching, and the pathway of the ecosystem transition from N-limited to N-saturated remains incompletely understood. The dynamics of N cycling are intimately linked to the associated carbon (C) and sulphur (S) cycles. We hypothesize that N saturation is associated with shifts in the microbial community, manifest by a decrease in the fungi-to-bacteria ratio and a transition from N to C limitation. Three mechanisms could lead to lower amount of bioavailable dissolved organic C (DOC) for the microbial community and to C limitation of N-rich systems: (1) Increased abundance of N for plant uptake, causing lower C allocation to plant roots; (2) chemical suppression of DOC solubility by soil acidification; and (3) enhanced mineralisation of DOC due to increased abundance of electron acceptors in the form of SO42− SO 4 2 − and NO3 − in anoxic soil micro-sites. Here we consider each of these mechanisms, the extent to which their hypothesised impacts are consistent with observations from intensively-monitored sites, and the potential to improve biogeochemical models by incorporating mechanistic links to the C and S cycles.