Figure 1: Stock age map of Norway spruce (Picea a&es) stands at the study sites. Num- bers denote percentage of admixed Scats pine (Pinus sylvestris). V-notch weirs are situ- ated in the eastern part of the catchments.
Bulk precipitation was collected bi-weekly in a clearing within the forest at Lysina.
Bulk precipitation was not measured at Pluhuv Bor due to the absence of clearings.
Throughfall was collected monthly in each catchment. The outflow from the catchments was monitored continuously using V-notch weirs and water level recorders. Streamwater was collected weekly for chemical analysis. The flow from the catchment was monitored continuously from September 1989 at Lysina and from November 1991 at Pluhiiv Bor. In each catchment, two lysimeter pits were excavated in 1993. One zero-tension lysimeter was inserted just beneath the organic horizon and beneath the first mineral horizon in each pit (depth 5-30 cm below the surface). Soil solution was sampled at approximately monthly intervals beginning in June 1994. Soils were sampled at nine locations at Lysina
66
--____ _ ..-- ..___-. __._^____,___.I. -_
and at four locations at Pluhiiv Bor. Spruce tissue samples were obtained from four representative trees, which were cut within each catchment. Detaiis of laboratory methods were described in Krbm et al. (1997).
3 Results and discussion
For the 1992-1994 water years mean measured rainfall was 999 mm yr-l at Lysina, and stream runoff was 442 mm yr-’ at Lysina and 244 mm yr-l at Pluhdv Bor (Krim 1997).
An assessment of the contribution of throughfall for the mature forested areas in conjunc- tion with bulk deposition for open areas (30 % at Lysina, 6 % at Pluhdv Bor) resulted in
a
water input to the soil of 814 mm yr-’ at Lysina and 630 mm yr-l at Pluh8v Bor.f Lvsina fPluhuv Borl
1600
i Q- 800 2.
600
Cams Anions Cations Anions
Figure 2: Mean charge balance in stream water at Lysina and Pluhfrv Bor. Ali, is inorganic monomeric AL, Fei, is inorganic monomeric Fe, RCOO- is naturally occurring organic anion.
Bulk precipitation to the study catchments was characterized by large inputs of NH:, NO,, H+ and SO:-. Overall, the bulk deposition of ionic solutes showed a strong anthro- pogenic influence. Throughfall fluxes were greater than bulk precipitation inputs for all
+
solutes except for NH, . Throughfall fluxes were dominated by SO:-, H+, NO,, and K+.
The high throughfall fluxes of SOi- reflect the high loading of dry deposition of sulfur to the region. Dry deposition was a significant source of acidic deposition as indicated by a SO, 2- throughfall/bulk pre cl station flux ratio of 3.4 (108 vs. 32 mmol mm2 yr-r at ‘p’
Lysina, 1992-1994).
At Lysina, acidic throughfall (pH 3.8) b e ow 1 the spruce canopy was further acidified by organic acids leached from the 0 horizon, resulting in low pH (3.6) of soil solution in the 0 and E horizons. In contrast, the acidic throughfall (pH 3.9) at PluhlPlv Bor was neutralized by the upper soil as reflected by the increases of soil solution pH in the 0 (pH 4.6) and A horizons (pH 5.4). Magnesium, the dominant cation in soil solution at Pluhfiv Bor, ranged between 300 and 1700 pmol l-l. In contrast, concentrations of Mg2+
in soil solution at Lysina were low (5-14 pm01 1-l ).
67
Weathering of feldspars in the Lysina catchment resulted in stream water with rela- A13+ (toxic form) was approximately 40 %, and Al-F complexes (relatively non-toxic) were roughly 35 % of Al;, during high-flow events. During baseflow, aquo A13+ decreased to albite, amphibole, orthoclase, antigorite, and talc. Concentrations of exchangeable base cations and soil pH were markedly different. Pluhiiv Bor exhibited high concentrations of exchangeable Mg, base saturation increased with depth, reaching essentially 100 %
3.6 - I I I 1
Now91 May-92 Nov-92 May-93 Now93 May-94 Nov-94
s20 2 15-
:10 - .
1 3 0, 5- h-J.,
Nov-91 May-92 Now92 May-93’
Date
Nov-93 May-94 Nov-94
Figure 3: Temporal patterns of stream water pH and concentrations of cations, mean daily runoff (curve) and instantaneous runoff at the time of sampling (circle or arrow) at the study sites in 1992-1994 water years (November-October).
s 0
~-100 f -200
s 400 2 300 6 200
* 100 30 s 120 LL
10 s60
$30 0
= 0 s90 g50 10 F20
E 15 L-10 g 5
s 0
Nov-9 1 Mav-92 Nov-92 Mav-93 Nov-93 Maw94 Nov-94
s-120
. . .
2 80- . .
%d . .A=-.
-1 J
-0. l
,--
Nov-91 May-92 Nov-92 May-93 Nov-93 May-94 Nov-94
Figure 4: Temporal patterns of stream water ANC and concentrations of anions, mean daily runoff (curve) and instantaneous runoff at the time of sampling (circle or arrow) at the study sites in 1992-1994 water years (November-October).
70
em---- -.-_ --.--.1.-.11”-~-..- -_ . . .x~. ._.
4 Conclusions
The experimental catchments served as valuable end-members of ecosystem sensitivity to severe levels of acidic deposition.
Soils at Lysina showed smalI pools of exchangeable base cations, and low soil and soil solution pH. Weathering and exchange processes in the catchment were unable to neutralize the high inputs of atmospheric acidity, resulting in elevated stream H+ and Al concentrations. Concentrations of potentially toxic Al (inorganic monomeric Al;,; and mainly A13+ species) were extremely high in Lysina stream water. Elevated concentrations of Al reflected a limited supply of base cations from granitic bedrock and podzolic soils, which were unable to neutralize strong acid inputs from atmospheric deposition. Visible symptoms of forest decline by needle yellowing were probably caused by Mg deficiency at Lysina.
The Pluhdv Bor catchment, underlain by the faster weathering serpentinite, showed extremely large pools of exchangeable Mg but smaller pools of other base cations. Ex- changeable concentrations and pools of soil Ca were relatively large at Pluhtiv Bor, despite the fact that Ca was found only in trace amounts in the serpentinite. Weathered amphi- Environmental Institute map of relative sensitivity to acidic deposition in Europe’.
In: J. P. Hetteligh; R. J. Downing and P. A. M. de Smet (eds.) Mapping critical loads chemistry and nutrient budgets for forested watersheds in New England: variability and management implications’. Forest Ecology and Management, Vol. 93, p. 73- 89.
[6] Krim, P. (1997) ‘Biogeochemistry of forest catchments in the Czech Republic with contrasting lithology under conditions of acidic deposition’. PhD dissertation, Syra- cuse University, Syracuse, New York, 179 p.
[7] Kram, P.; J. HruSka; C.T. Driscoll and C.E. Johnson (1995) ‘Biogeochemistry of aluminum in a forest catchment in the Czech Republic impacted by atmospheric inputs of strong acids’. Water, Air, and Soil Pollution, Vol, 85, p. 1831-1836.
[8] Kram, P.; J. HruSka; B. S. Wenner; C. T. Driscoll and C. E. Johnson (1997) ‘The biogeochemistry of basic cations in two forest catchments with contrasting lithology in the Czech Republic’. Biogeochemistry, Vol. 37, p. 173-202.
(91 K&m, P.; J. HruSka and C. T. Driscoll (1998) ‘Beryllium chemistry in the Lysina catchment, Czech Republic’. Water, Air, and Soil Pollution, Vol. 105, p. 391-397.
[lo] O’Brien, A. K.; K. C. Rice; 0. P. Bricker; M. M. Kennedy and R. T. Anderson (1997)
‘Use of geochemical mass balance modelling to evaluate the role of weathering in determining stream chemistry in five Mid-Atlantic watersheds on different lithologies’.
Hydrological Processes, Vol. 11, p. 719-744.
[ll] Roberts, B. A. and J. Proctor (eds) (1992) ‘The ecology of areas with serpentinized rocks. A world view’. Geobotany 17. Kluwer Academic Publishers, Dordrecht.
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