The effect of reduced atmospheric deposition on soil and soil solution chemistry at a site subjected to long-term acidification, Načetín, Czech Republic

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<ul><li><p>continued, although the Ca concentration decreased from 110 eq l1 in 1997 to 25 eq l1 in 2005 in the mineral soil solution at</p><p>1. Introduction</p><p>Science of the Total Environment 330 cm depth. This dramatic change was not observed for Mg concentration in soil solution, because its deposition remained stableduring the observed period. Similar patterns were observed in the deeper soil solution at 90 cm. The reduction in Ca availabilityresulted in lower uptake by tree assimilatory tissues, measured as concentration in needles.</p><p>Since 2005, the leaching of nitrate observed in soil solution at 30 cm depth has disappeared. By 2003 a similar situationoccurred at 90 cm. Higher incorporation into the trees after 1997 could be an important factor. With respect to the formerly highsulphur deposition and consequently released aluminium, which could have negatively influenced the biotic immobilization drivenby microbes and fungi, the recovery may have positively impacted and therefore improved retention in the ecosystem during recentyears. The delay in the successful retention of nitrogen in the ecosystem was probably caused by the high mineralization of organicmatter after improvement of chemical parameters in the organic horizon (increase in pH and decrease in Al concentration). It seemsthat high mineralization of stored organic matter after decades of high acidic deposition could be an important factor affecting thehigh losses of nitrogen in spruce forest ecosystems. 2006 Elsevier B.V. All rights reserved.</p><p>Keywords: Long-term monitoring; Recovery; Soil solution; Base cations; Nitrogen; Norway sprucechemistry at a site subjected to long-term acidification, Naetn,Czech Republic</p><p>Filip Oulehle a,, Jek Hofmeister a, Pavel Cudln b, Jakub Hruka a</p><p>a Czech Geological Survey, Department of Environmental Geochemistry and Biogeochemistry, Klrov 3, 118 21 Prague, Czech Republicb Institute of Systems Biology and Ecology, Academy of Sciences of the Czech Republic, Department of Forest Ecology,</p><p>Na Sdkch 7, 370 05 esk Budjovice, Czech Republic</p><p>Received 20 March 2006; received in revised form 19 July 2006; accepted 21 July 2006Available online 28 August 2006</p><p>Abstract</p><p>During the 1990s the emissions of SO2 fell dramatically by about 90% in the Czech Republic; the measured throughfalldeposition of sulphur to a spruce forest at Naetn in the Ore Mts. decreased from almost 50 kg ha1 in 1994 to 15 kg ha1 in 2005.The throughfall flux of Ca decreased from 17 kg ha1 in 1994 to 9 kg ha1 in 2005; no change was observed for Mg. Thedeposition of nitrogen ranged between 15 and 30 kg ha1 with no statistically significant trend in the period 19942005.</p><p>The desorption of previously stored sulphur and the decrease of Ca deposition are the main factors controlling the recovery ofsoil solution. The pH of the soil solution at a depth of 30 cm remains unchanged, and the Al concentration decreased from320 mol l1 in 1997 to 140 mol l1 in 2005. The enhanced leaching of base cations relative to no acidified conditions hasThe effect of reduced atmospheric deposition on soil and soil solution Corresponding author.E-mail address: oulehle@cgu.cz (F. Oulehle).</p><p>0048-9697/$ - see front matter 2006 Elsevier B.V. All rights reserved.doi:10.1016/j.scitotenv.2006.07.03170 (2006) 532544www.elsevier.com/locate/scitotenvDuring the second half of the 20th century, elevatedinputs of acid deposition have affected natural cycles of</p></li><li><p>otal Emany elements, leading to the disruption of numerousnatural processes. The most affected environs includemostly forested areas in central Europe (e.g. Schulzeet al., 1989). Particularly, in the area of the Ore Mts.in the north-west part of the Czech Republic, about25,000 ha of spruce forests were killed or severelydamaged by 1990 (Kubelka et al., 1993). After WorldWar II, coal mining in a nearby basin was rapidly steppedup. The S-rich coal, for which the sulphur content rangesfrom 1% to 15% (Moldan and Schnoor, 1992), has beencombusted in several local power plants, which lackedabatement technology until 1994. Such intensive coalcombustion resulted in extremely high SO2 concentra-tions in ambient air (average SO2 for the 1980s N100 gm3) (Peters et al., 1977). By 1999, the power plantemissions had declined by about 90% and SO2 con-centration decreased to b10 g m3 (Czech Hydrome-teorological Institute, unpublished data).</p><p>In the last 20 years, anthropogenic emissions of SO2together with mineral dust and subsequent deposition ofH+, SO4</p><p>2, Ca andMg to forest ecosystems in Europe andNorthern America have decreased substantially (Stod-dard et al., 1999; Hedin et al., 1994). The previous highrates of acidic deposition raise questions concerning thetime-scale of soil and forest ecosystems recovery. Therelease of formerly stored SO4</p><p>2 from the soil (namelyfrom the O horizon) can markedly delay the recovery ofsoil solution and streams for decades (Mrth et al., 2005;Alewell et al., 1997; Novk et al., 2000). The low ex-changeable pools of Ca andMg in soils affected by long-term deposition are sensitive to changes in atmosphericinputs of these elements. This could lead, together withcontinuous Al stress caused by low soil pH, to worseningCa and Mg supplies for the tree assimilatory tissues(Alewell et al., 2000). As indicators of tree root damage,molar ratios of Mg/Al (Jorns and Hecht-Buchholz,1985), Ca/Al (Cronan and Grigal, 1995) and BC/Al(Sverdrup and Warfvinge, 1993) are commonly used.Moreover, the molar ratios of base cations to aluminiumare often used for calculating critical loads for acid de-position (Blaser et al., 1999).</p><p>Despite the high reduction of S inputs, the N depo-sition during the last two decades has been more or lessconstant. However, N deposition is characterized by adistinct year-to-year variation, primarily due to varyingmeteorological conditions, thus complicating the detec-tion of time trends (Wright et al., 2001). The artificialinputs of nitrogen highly exceed the natural backgroundin European forests (MacDonald et al., 2002). This leadsto nitrogen saturation, in which the availability of inor-ganic nitrogen is in excess of biological demand so that</p><p>F. Oulehle et al. / Science of the Tthe ecosystem is unable to retain all incoming nitrogen(Wright et al., 1995). One of the effects caused bychronic high N deposition is forest decline (Nihlgrd,1985) and NO3</p><p> pollution of ground and surface waters(Stoddard, 1994). The nitrate leaching to groundwater isassociated with flux of cations, which could leads toserious changes in the soil chemical properties. There isalso evidence that at high N inputs the storage of humusmay increase (Berg and Matzner, 1997; Nadelhofferet al., 1999). To understand N behaviour, studies inEurope and in the United States have been initiated(Gundersen et al., 1998a; Magill et al., 2000). Some ofthese studies have been focused on the effects of in-creasing nitrogen input and defined conditions in whichnitrogen availability exceeds the capacity to accumulatenitrogen (Aber et al., 1998), while other groups haveexperimentally reduced nitrogen and acid inputs by roofmanipulations (Wright and van Breemen, 1995). Theexperiments studying the response of an ecosystem toadded nitrogen have shown that mycorrhizal assimila-tion and exudation is the dominant process involved inimmobilization of added nitrogen (Aber et al., 1998).Loss of mycorrhizal function during nitrogen saturationcould be a key process leading to increased nitrificationand nitrate mobility (Aber et al., 1998). The results fromN-reduction experiments have shown that nitrate leach-ing is efficiently reduced to very low levels in a rathershort-term (12 years after start of manipulation)(Bredemeier et al., 1998).</p><p>This paper provides an analysis of long-term trends ofbulk precipitation, throughfall, and soil water, soil andtree tissue chemistry from the experimental site Naetnin the Ore Mts., Czech Republic. Our intent was (1) todescribe the response of soil and soil solution chemistryto decreasing atmospheric deposition, and (2) to evaluatewhether the possible changes in the soil environmentwere related to nutrient content in tree needles and an-nual radial increment.</p><p>2. Materials and methods</p><p>2.1. Site description</p><p>The monitored site is located near the Czech andGerman border in the Ore Mountains (Fig. 1), close tothe villages of Kienhaide (Germany) and Naetn(Czech Republic), with an average annual temperatureof 6.3 C (19912004), average annual precipitation842 mm (19912004, meteorological station at NovVes, 745 a.s.l.), aspect to the north-west and slope 2.5.The bedrock consists of paragneiss with a low content ofMgO (2.21%) and CaO (0.66%). The dominant soil type</p><p>533nvironment 370 (2006) 532544is represented by dystric cambisol with sandyloam</p></li><li><p>in the</p><p>otal Etexture and a moder-mor type of humus horizon. Thestudied stand (503526N, 131514E) lies at anelevation of 784 m a.s.l. and is covered by 70-year-oldNorway spruce (Picea abies/L./Karst.). The spruce for-est at this site is one of the very few remaining maturespruce stands in the Ore Mts. that has never been limedbecause of the vicinity of the German border.</p><p>2.2. Methods</p><p>In April 1994, a sampling network of 25 samplers</p><p>Fig. 1. Naetn site location</p><p>534 F. Oulehle et al. / Science of the Tspaced in a regular 1010 m grid was installed forthroughfall measurements. Bulk precipitation was sam-pled at a nearby (ca 150m) open field. From1994 to 1996,precipitation was collected fortnightly and later monthlyup to the end of measurements in March 1999.Polyethylene funnels (area of 122 cm2) were replaced inwinter by open plastic vessels (area 380 cm2) with PEbags. Since May 2003, a new set-up for throughfallmeasurements consisting of a 1515 m grid with 9 sam-plers has been installed at the same place as the former.Precipitation was sampled monthly by polyethylenefunnels (area of 122 cm2) replaced in winter by openplastic vessels (area of 167 cm2).</p><p>Soil water has been collected since the 1990s usingPRENART suction lysimeters at depths of 30, 60 and90 cm in the mineral soil (7 lysimeters at 90 cm, and 4lysimeters at 30 and 60 cm each). We used Prenart superquartz soil water sampler, which is made of PTFE/quartz(50/50%). It can be applied for soil water sampling in allsoil types and is most applicable for investigations ofsoil nutrient status and heavy metal content. All ly-simeters were sampled monthly, from 1994 to 1996fortnightly, and bulked at the end of the month to createone sample from each depth for each month. The sam-pling was finished in March 1999 and has been re-established since May 2003 with the original set-up as inthe 1990s.</p><p>Water pH was measured using a Radiometer TTT-85pH meter with a combination electrode (Radiometermodel GK-2401C). Cl, SO4</p><p>2, NO3 were measured by</p><p>ion exchange chromatography, and F by a potentiometricion selective electrode after TISAB addition. Ca, Mg, Na,</p><p>Ore Mts., Czech Republic.</p><p>nvironment 370 (2006) 532544K, and Al were determined by flame atomic absorptionspectrometry (FAAS), and NH4</p><p>+ by indophenol bluecolorimetry. Ionic concentrations ofCa2+,Mg2+, Na+, andK+ were assumed to equal the total concentrations. Alka-linity was measured by strong acid (0.1 M HCl) titrationwith Gran plot analysis. ANC was calculated as thedifference between base cations and strong inorganicanions.</p><p>The quantitative soil samples were based on four pitsin 1994 and six pits in 2003. Soil masses were estimatedby excavating 0.5 m2 pits by the method described inHuntington et al. (1988). This technique entailedcollection of the Oi plus Oe (litter and fermented layers)horizons as a single sample, and then the Oa (humus)horizon. The soil samples were weighed, and then afterair-drying sieved (mesh size of 5 mm for organichorizons and 2 mm for mineral horizons). Soil moisturewas determined gravimetrically by drying at 105 C.Soil pH was determined in deionized water and in0.01 M CaCl2 (1994) and 1 M KCl (2003). Exchange-able cations were analyzed in 0.1 M BaCl2 extracts by</p></li><li><p>otal Ethe AAS method. Exchangeable acidity was determinedby titration of 1 M KCl (1994) and 0.1 M BaCl2 (2003)extracts. Cation exchange capacity (CEC) was calculat-ed as the sum of exchangeable Ca, Mg, K, Na andexchangeable acidity. Base saturation (BS) was deter-mined as the fraction of CEC associated with basecations (Ca, Mg, K and Na). The content of total S wasmeasured gravimetrically as BaSO4. Total C and N weredetermined simultaneously using a Carlo-Erba Fusion1108 analyser in 2003. The C and N data from 1997were taken from Schulze (2000), and C/N ratios in 1989from Dambrine et al. (1993).</p><p>The biomass material was slowly combusted up to550 C then dissolved in concentrated HF and H3BO3.After evaporation the samples were dissolved in HCland measured by the AAS method for Na, Ca, Mg, Kand Al. The samples were annealed with Eschka mixturein oxidizing atmosphere and sulphur content was gravi-metrically measured as BaSO4. The N concentrationwas determined using an Carlo-Erba Fusion 1108analyser. The litter fall has been collected two timesper year (MayOctober and NovemberApril) using 5collecting frames (11 m) since 1994. The viableneedles of 5 trees were collected in 1994 and 2003 fromthe upper part of tree crown and divided into 1st and 2ndyear classes.</p><p>For time series with a higher sampling frequency, theseasonal MannKendall (MK) test (Hirsch et al., 1982)was applied (Libiseller). This test is widely used inenvironmental science, because of its simplicity, robust-ness and ability to cope with missing values and valuesbelow the detection limit. For more details about MannKendall statistics see Ulrich et al., 2006. A significancethreshold of pb0.05 was applied to the test trends. Asecond threshold of pb0.20 was also used to identifyweak, but potentially genuine, trends (Evans et al.,2001).</p><p>For estimation of differences between groups, theANOVA test was used with significance at a p-level of0.05.</p><p>3. Results</p><p>3.1. Atmospheric deposition</p><p>The measured annual precipitation amount rangedbetween 790 and 1320 mm with an average of 945 mm,with no trend during the observed period 19942005. Theseasonal MannKendall (MK) model indicated a de-creasing trend in SO4</p><p>2 concentration ( p=0.002) in bulkprecipitation (Fig. 2). The bulk S deposition decreased</p><p>F. Oulehle et al. / Science of the Tfrom 13 kg ha1 in 1992 to 5.6 kg ha1 in 2005. Therewas no change in NO3 and NH4</p><p>+ concentrations. Alongwith the decreased concentration of SO4</p><p>2, pH of bulkprecipitation has significantly increased (p=0.009), from4.29 in 1992 to 4.45 in 2005, while there was no change inGran alkalinity (average 50 eq l1). There was nosignificant trend observed in cation concentrations, exceptfor Ca, which decreased significantly (p=0.022) and aweak decrease in Na concentration (p=0.060). The Cabulk deposition was 4.4 kg ha1 in 1992 and decreased to2.1 kg ha1 in 2005.</p><p>More pronounced changes were observed during theperiod 19942005 in throughfall precipitation (Fig. 3).There was a significant decrease in SO4</p><p>2...</p></li></ul>

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