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Original article Fluxes of dissolved mineral elements through a forest ecosystem submitted to extremely high atmospheric pollution inputs (Czech Republic) E Dambrine V Kinkor D J Jehlicka 1 Gelhaye 1 INRA-CRF, Champenoux, 54280 Seichamps, France; 2 Geological Institute,Malostranske 19, 11821 Prague, Czech Republic (Received 3 September 1992; accepted 20 December 1992) Summary — Fluxes of dissolved mineral elements have been monitored in a declining spruce stand in northern Bohemia. This area is subjected to very high atmospheric pollution. Mean annual throughfall pH was 3.15 and monthly mean values as low as 2.6 were recorded. Measurements show deposition values per ha and per year as high as 150 kg S, 60 kg Ca and 12 kg Al as well as a proton input > 5 keq/ha/yr H Part of the input was immobilized in the litter layer and the remaining . + acid load was buffered by Al release in the mineral horizons. High nutrient inputs may explain why no mineral deficiencies have been detected, although tree mortality is extremely high in this area. atmospheric pollution / acidification / forest soils / forest decline / Czech Republic Résumé — Flux d’éléments minéraux dans un écosystème forestier hyper-pollué du nord de la Bohème (Réblique tchèque). Les flux d’éléments minéraux en solution dans un peuplement d’épicéa dépérissant du nord de la Bohème ont été mesurés au cours de l’année 1989. Cette région subit une effroyable pollution atmosphérique due à l’exploitation minière et à la combustion de lignite riche en soufre et en cendres dans un bassin industriel voisin ainsi que dans plusieurs centres in- dustriels du sud de l’Allemagne (ex-RDA). Nous avons mesuré des dépôts atmosphériques sous le couvert forestier considérables : respectivement 150 kg de S, 60 kg de Ca, 46 kg de N, 12 kg d’Al par ha et par an. Ces valeurs, environ 5 fois supérieures à celles couramment mesurées dans les sont attribuables aux émissions importantes de cendres de combustion dont peuplements vosgiens, la dissolution neutralise une partie du dépôt acide. Néanmoins, le dépôt atmosphérique acide dé- passe 5 keq H avec des pH moyens mensuels dans les pluies sous couvert descendant à /ha/an + 2,6. Curieusement, la vague de mortalité qui dévore ces peuplements (40 000 ha de forêts étaient déclarés morts en 1987), ne s’accompagne pas de symptômes de carences minérales visibles (Mg, Ca ou K) du type de celles généralement observées en France et en Allemagne dans les peuple- ments d’épicéas dépérissants. Les considérables apports atmosphériques de nutriments mesurés pourraient expliquer ce phénomène. La cause directe des mortalités est attribuée aux effets directs de la pollution atmosphérique (acidité et teneurs en SO accentués par les phénomènes climati- ) 2 ques (fortes gelées). En ce sens, les dépérissements observés diffèrent fortement de ceux étudiés en France. Les conséquences à long terme, dans cette région, des dépôts acides et de métaux
lourds sur les propriétés des sols, la qualité des eaux, mais aussi la santé humaine, sont telles, sur que l’interruption des émissions est extrêmement souhaitable. pollution atmosphérique / acidification/ sois forestiers / dépérissement / République tchèque INTRODUCTION ing of mineral fluxes within this ecosystem over a 1-yr period. During the eighties, the existence of large of forest damaged by atmospheric areas SITE GEOGRAPHY AND ECOLOGY pollution in the East European regions was (KUBELKA, 1987) described by the western media and dra- matic pictures of this ecological disaster The Krusne Hory mountains in northern shown in the press. At the same were Bohemia consist of Hercynian crystalline time, symptoms of a new type of disease, rocks. They are formed by a plateau which rapidly called forest decline (Waldsterben) slopes gradually towards the north of the were observed in many forested areas in German border. From the edge and to- West European countries. Such a coinci- wards the south, this range drops steeply dence, and the fact that forest damage in into the Krusne Hory piedmont basin. The the East was indisputably caused by at- forests are composed of beech (Fagus syl- mospheric pollution led many foresters vatica) in the piedmont and spruce, whose and scientists to consider that atmospheric development above 400 m has been fa- pollution was the main cause of forest de- voured by foresters. The soils vary from an cline in the West European forests. acid oligotrophic brown earth to podzolic Collaboration between Czech and types on the slopes, and peaty soils devel- French scientists was initiated in 1988 in op on the flat surfaces of the plateau. order to analyse the differences between This range is subjected to extremely the causes of forest decline in East and high levels of atmospheric pollution due to West European countries. the intensive mining and burning of brown The influence of high pollutant inputs on coal in the basin. Brown coal is composed hydro-geochemical cycles at the catch- of 26-44% ashes and 0.5-3% sulphur. ment level had been studied in northern Winds blowing from the south-east carry Bohemia for several years by the Geologi- gaseous and solid pollution to the higher cal Institute of Prague (Paces, 1985; Mol- altitudes where they meet cold air masses dan and Dvorakova, 1987). However, al- coming from the north east. Fogs enriched though the chemical properties of the soils with pollutants develop in the area of con- had been analysed on a broad scale by tact, ie between 600-800 above lev- m sea foresters (Materna, 1989), no data were el. This represents the site of the zone available on dynamic budgets at the soil heaviest emission-induced damage. Obvi- scale. The following study was designed to symptoms of decline consist essential- ous the chemical changes occurring of reddening and needle losses. No ly assess within the soil of a living spruce stand un- large-scale discolouration linked to mineral der the influence of such high inputs. It deficiencies has been reported in this area presents the results of continuous monitor- (Pfans and Beyschlag, 1993).
described, they were sampled. Several samples Until 1930, the forest in this area was of each horizon were bulked and a homogen- considered healthy. In 1950, after the first ised sample of each horizon was analysed. Ex- survey of forest health, 30 000 ha were changeable base cations and acidity were deter- considered to be endangered. Forest die- mined after 1 M KCI extraction. CEC was back has increased gradually since 1977. calculated as the sum of the exchangeable base Mortality has increased significantly, pre- cations and acidity. Total sulphur was deter- mined by X-ray fluorescence. sumably under the cumulative influence of increased emissions, prolonged tempera- In the autumn of 1988, throughfall collectors and soil solution samplers were set up. Each ture inversions and abrupt climatic chan- throughfall collector consisted of a polyethylene ges. In 1986, > 65% of the forest in this guttering 10 cm deep with an area of 1 800 cm. 2 area was considered seriously damaged One was set up in the immediate vicinity of a and 16% was dead. tree trunk and 2 others within the space be- tween 2 trees. One bulk precipation collector Mechanised techniques including scrap- was set up in June 1989 in a clearing, a few ing of the humus (considered to be too hundred m from the stand. acid), drainage, liming and fertilisation, and Zero tension lysimeters were inserted into plantation with pollution-resistant species the front of several soil pits: in the F horizon and are currently being applied in order to reaf- at -10 cm (E horizon), -30 cm (Bs), -70 cm forest this area. (BC2). Lysimeters in the humus (BC1),-100 cm (Ø =3 cm) open polyethylene were narrow in length. Nine of them were insert- pipes 50 cm ed in the transition zone between the F and H MATERIALS AND METHODS horizon of a Vaccinium myrtillus zone, with 9 others in a grass area. Lysimeters in the mineral The forest stand was located on a gentle north- soil consisted of 50 cm x 40 cm polyethylene west slope facing the East German border near plates. Three lysimeters per sampling depth the village of Nacetin, 10 km north of Chomutov. were carefully inserted by pushing them into the It was chosen because defoliation was limited, soil parallel to the terrain slope with a hydraulic and soils were known not to be limed in this device. Nylon tubes were connected to the ly- simeter exit and led along a trench to a second area; the stand is at an altitude of 780 m. Mean pit located a few m dowslope in which collecting precipitation is 800 mm per year and mean = barrels were set up. The pits in which lysimeters temperature is 6 °C. In comparison with these were inserted were refilled afterwards with the average values, the period studied (1988-1989) soil taking into account the natural horizon or- was relatively dry, especially during the winter. der. In order to collect water during periods of The trees were 70-90-yr old spruce with a mean slow drainage, a set of 3 teflon cups (Prenart height of 25 m. Defoliation was noticeable and = type) were set up at -100 cm. A tension of 500 was estimated to be ≈ 30-40%. The needles mbar was applied once a month via a manual were sometimes red in colour, generally attribut- ed to the direct effects of SO or to interaction pump. , 2 between SO and frost. The density of the 2 Solutions were sampled monthly and bulked stand, which was considerably reduced by fell- for each depth except for the organic layer for ing of dead trees during the last decade, was which the solutions originating from the Vaccin- currently 440 trees/ha in the area studied. This ium and grass areas were analysed separately. recent opening of the stand permitted strong Solutions were filtered through 0.45-μm micro- growth of the ground vegetation which covered pore filters under air pressure and analysed by the entire soil surface except at the foot of the standard methods in the Geological Survey la- trees, where large amounts of litter accumulat- boratory. The mineral element budget was cal- ed, composed of 5-50 m patches of Vaccinum 2 culated by multiplying the volume weighted mean annual values of concentration by either myrtillus and dense herbaceous species (Des- champsia flexuosa, Calamagrostis sp). Four pits the measured annual amount of throughfall, or a calculated amount of drainage water. Taking were dug in the soil, and after their main mor- into account the poor crown conditions of the phological characters and root density had been
trees, the low density of the stand, and the studies dealing with far less polluted areas which occurred during the summer, we drought (Kinkor, 1988; Probst et al, 1990; Feger et assumed that the transpiration of the forest al, 1991). Of interest is the relatively high stand was equal to 100 mm/yr. This value is = base saturation of the H horizon, which de- 50% of that derived from direct transpiration notes a significant accumulation of these measurements on defoliated mature spruce elements. This might reflect the dissolution stands in rather similar climatic conditions of soluble salts during KCI extraction. Tot- (Dambrine et al, 1992). The ground vegetation was assumed to take up 50 mm/yr. Uptake of tal sulphur concentration is high in the or- water was distributed within the soil assuming ganic layer and decreases markedly with that it was proportional to the observed root depth. density. Thus, we related 20% of the water up- take to the humus layer, 30% to the 0-10 cm layer, 30% to the 10-30 cm layer and the re- Mineral element dynamic mainder to the deeper horizons. Figure 1 presents the average volume RESULTS AND DISCUSSION weighted mean concentrations of anions and cations in solutions throughout their pathway from open land precipitation to Soil chemical characteristics deep drainage. Bulk precipitation The soil is podzolic type soil developed a gneissic saprolite. Table I coarse a on Bulk precipitation is strongly acid (table II): the main soil analytical character- presents pH of monthly samples varies between 3.8 istics. pH is extremely low except in the H layer. In spite of these low pH values, and 4.4, which is within the range of the base saturation values are in the same values measured in industrialised coun- tries (Semb and Dovland, 1987; Cape and range as those measured in numerous
most 50% of the acidity associated with Fowler, 1987). However, most concentra- the dissolution of sulphuric acid is buffered tions are relatively high compared with oth- er data from less polluted areas. In con- by the dissolution of these cations (Hodg- trast, concentrations appear rather low son et al, 1982). compared with those measured by Paces (1985) in a catchment located on the Forest floor southern slope of the massif, facing the brown coal power station. The limited A considerable decrease of concentrations number of bulk precipitation samples col- for most of the elements occurs within the lected in this study does not allow any fur- humus layer. Sulphate is divided by a fac- ther comparison to be made. tor of 2.2, chloride by 1.6, and calcium by 1.5 (table III). The reduction is greater un- Canopy der the grass area compared to the area with Vaccinium. Because both areas are When passing through the canopy, con- located in similar positions in relation to the centrations increase considerably, far trees, this difference is probably derived more than the concentration effect due to from the effect of the ground vegetation it- interception: as a mean, conductivity is self rather than from the spatial variability multiplied by 9. pH drops to a mean value of deposition. of 3.15 with extreme monthly values as low as 2.6 (March 1989). The homogene- Mineral soil ity of the ratios between throughfall and open land precipitation concentrations, ex- Concentrations remain rather stable from cept for K and Mn which are known to be the humus layer to the E horizon, except leached from the canopy, show that this in- for silica which increases markedly and for crease is derived mainly from the deposi- the nitrogen compounds: NH decreases 4 tion of gas and airborne ash, originating as Al and H increase, parallel to NO + . 3 from the combustion of brown coal (table This change can be attributed to nitrifica- II). It is worth noting the very high concen- tion of deposited NH In spite of the strong . 4 trations of basic cations as Ca, but also of acidity of the solutions, the input of Ca Fe and Al, which are more typical of acid maintains a rather high Ca:Al ratio (2.5). soil solutions than throughfall. Assuming that most of these elements come from The main change occurs within the wind-blown ash, one can calculate that al- upper Bs horizon where Al is released
while protons are consumed (fig 1).Figure Mg, Al and heavy metals in throughfall, as- 2 shows a clear relationship between Al 3+ sociated with atmospheric inputs; 2) the 4 2- SO and ions in solution at different strong decrease in concentrations from depths. This leads to high Al concentra- throughfall to the litter layer. This decrease tions and to a rather low Ca:Al ratio (0.6 at may be attributed to different causes: a) -30 cm; 0.5 at -100 cm). However, it the measurements of throughfall might should be noted that those ratios are not slightly overestimate the deposition be- particularly low compared with those collectors were placed in an area cause measured in various healthy or declining where the canopy was slightly denser than spruce stands (Bredemeier et al, 1990; in the neighbouring area where the lysime- Probst et al, 1990). This is due to the high ters were located. However, the overesti- concentration of basic cations linked to the mation of the deposition should not exceed large inputs of these elements. Neither the 20%. Moreover, the measured amount of basic cations nor Si concentration in- throughfall is relatively low compared with crease significantly in solution from -10 to the open land precipitation, taking into ac- -100 cm. Thus the release of such ele- count the poor crown conditions; b) the ments by weathering may be very low, in ground vegetation, which recently has de- spite of the strong acidifying conditions. Al veloped very rapidly takes up a large release may be derived from the dissolu- amount of elements. This is likely when tion of amorphous Al compounds, as comparing the first set of lysimeters in the shown by Mulder et al (1989). forest floor which was placed under a large area of Vaccinium with the second set un- The following aspects of changes in der dense grasses; c) elements are tempo- concentrations throughout the ecosystem rarily immobilised in the litter layer because are relatively original as compared with of the relatively dry conditions. None of other studies: 1) the extremely high con- these explanations is fully satisfactory be- centrations of sulphur but also of Ca and
cause of the very substantial reduction in change in the canopy, the acidity input as- concentration of all the elements including sociated with free protons, Al and Fe ions chloride, but a combined effect is likely; 3) remains extremely high (5.2 keq/ha/yr). All in spite of the rather low C:N ratio of the element fluxes are reduced when passing forest floor, solutions passing through this through the forest floor. One should bear in layer do not show the peak in basic cations mind that this horizon shows a relatively and nitrogen concentrations commonly high base saturation in spite of its low pH. found in other studies and generally attrib- In fact, whatever the artefacts due to the uted to organic matter mineralisation. This short period of study, this accumulation of might be due to a low mineralisation asso- basic cations in the humus may be linked ciated with the drastic deposition chemistry to the flux reduction measured in this layer. (Lettl, 1990) and/or to the development of It is interesting to note that the sulphur flux ground vegetation. is that which is reduced the most drastical- ly. Even if we use chloride as an index, the importance of the reduction within the hu- Mineral element budgets mus layer is limited, but remains. Sulphur might accumulate in the humus (David and Mitchell, 1987; Vannier, 1992), or be lost Table IV shows the budget of major ions as a gas (Goldan et al, 1987). The strong from open land deposition to deep seep- smell in the air in this area could be partly age water. The depositions of sulphur, cal- derived from these emissions. A similar dif- cium and magnesium in throughfall ference between S input and output was amount respectively to 150, 58 and 8 kg/ noticed by Kinkor (1988) for a catchment ha/yr which are among the highest values located 10 km south of this stand. Thus, reported in the literature (Hauhs et al, = this sulphur reduction process in the hu- 1990). The amounts of Ca, Mg and Al in mus layer appears possible although unex- throughfall buffer ≈ 50% of the acidity as- plained. Although mineral drainage is re- sociated with the sulphur input. These ba- duced compared to the input, the leaching sic cation inputs might explain why the of acidity as free protons and Al amounts 3+ trees do not suffer from Ca or Mg deficien- to 2.85 keq/ha/yr which is buffered at cies. However, even if we neglect the pro- present in the regolith. ton load neutralised by base cation ex-
CONCLUSION REFERENCES Bredenmeir M, Matzner E, Ulrich B (1990) Inter- spite of the In short period covered by this nal and external proton load to forest soils in several interesting features have study, northern Germany. J Environ Qual 19, 469- been observed and confirm previous inde- 477 pendent investigations. The stand studied Fowler D (1987) Rainfall acidity in Cape JN, receives extremely high amounts of a northern Britain-exploring the data. In: Proc large number of chemical elements which Int Symp Acidic Precipitation Muskoka (Mar- are acidifying compounds, nutrients and tin H, ed) D Reidel, Dordrecht, 239-244 heavy metals. Because of the presence of Dambrine E, Carisey N, Pollier B, Girard S, Gra- nutrients in this cocktail of pollutants, the nier A, Lu P, Biron P (1992) Dynamique des acidifying effect of such an input into the éléments minéraux dans la sève xylémique soil is probably not the driving force of for- d’épicéa de 30 ans. Ann Sci For5 (in press) est damage in this area (Pfans and MB, Mitchell MJ (1987) Transformation of David Beyschlag, 1992). In fact, although proton organic and inorganic sulphur: importance to deposition is very high, basic cation input Adirondack forest soil. JAP- sulfate flux in an seems high enough to prevent basic cat- CA 37, 39-44 ion deficiencies, at least for the moment. Zöttl HW, Brahmer G (1991) Assess- Feger KH, Because the main buffering process within ment of the ecological effects of forest fertili- the soil is the dissolution of aluminium zation using an experimental watershed ap- compounds, acidity is transferred down to proach. Fertil Res 27, 49-61 the regolith. Thus, the risks of groundwater Goldan PD, Kuster WC, Albritton DL, Fehsen- pollution are very serious. feld FC (1987) The measurements of natural sulfur emissions from soils and vegetation: The absence of a release of nitrogen three sites in the Eastern United States revis- and base cations in the soil solutions of ited. J Atmos Chem 5, 439-467 the forest floor suggest a low rate of de- Hauhs M, Rost Siebert K, Raben G, Paces T, composition, which might be linked to the Vigerust B (1990) Summary of European acidity of the deposition or to its heavy data. In: The Role of Nitrogen in the Acidifica- metal content. In fact, little is known about tion of Soils and Surface Waters (Malanchuk the deposition rates of heavy metals in this and Nisson, eds) Nordic Council of Ministers, area, in particular beryllium and arsenic 500-536 which are present in brown coal clays (Ku- Brown DA (1982) Neutrali- Hodgson L, Dyer D, biznakova, 1987) and may have disas- sation and dissolution of high-calcium fly ash. trous effects on living organisms. J Environ Qual 11, 93-98 Kinkor W (1987) Acidifcation of two small basins The extremely high sulphur input does in the Krusne Hory mountains. In: Extended to be transferred entirely to the not seem Abstr, Geomon Congr May 1987 (Moldan deeper soil horizons, nor to the streams. and Paces, eds) Prague, 204-206 Accumulation of sulphur in the humus Kinkor W (1988) Influence of acid rain on chemi- layer and/or gaseous sulphur compound cal properties of soils in the Bohemian massif emissions are possible mechanisms which (Czechoslovakia). In: Int Rep Agric. Univ Wa- could contribute to this process. geningen, The Netherland, p 35 Because very large forest areas (sever- Kubelka L (1987) Forestry in the Krusne Hory al hundred thousand ha) in Czechoslova- mountains. In: Excursion Guide, GEOMON kia, Eastern Germany and Poland have Workshop, May 1987 (Paces and Moldan, been and are still damaged by this type of eds) Prague, 19-26 pollution, a great reduction of the emis- Kubiznakova J (1987) Behaviour of beryllium in sions is urgently required. the Sokolov district. In: Extended Abstr GEO-
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