Hofmann, R., Bieber, E., Beudert, B., ScMeyei, R.
Federal Environment Agency
Pau1-Ehrlich-Stra1e 29, D-63225 Langen GERMANY
e-mail: ruediger.hofmann@uba.de, ruprecht.schleyer@uba.de
The research area forellenbach (trout-brook) in Germany is apart ofthe National Park at the Bavarian Forest. The area is up to 95 % covered by forests and can be described as representafive of the main forest types of the mner Bavanan Forest region. The area of the transect is 0.69 km2. It extends in length for 2.9 km, altitude ranges between 787 m and 1292 m a.s.1.. Average elevationandmcinafion are 88$ m a.sJ. and 12%. Moderately sloping parts of the hifiside (3-8%)account for 69 % of the total area.
The geological basement mainly consists of crystalline bedrock (oider Finsterauer crystal granite), soils are dominated by sandy-loamy cambisol and hydromorphic soils. A periglacial surface stratum supplies initial matenal for pedogenesis in the lower parts of the hiilside. Dominating soil texture (58 %)is a sandy-loamy dystric cambisol, which is developed to a depth of 60-100 cm, partly showing signs of podzolic degradation. In the more erodedparts of theupper hiilside this soil type occurs in association with rankers, liffiosols and well developed podzols. In the soils which have constitutionaily a low nutrient content and low buffenngcapacity there is a dis%nct acidffication and in particular the content of magnesium and calcium is reduced to poverty (base saturation status in mineral soil < 10 %). Mineral top soils of low base saturafion (< 10 %) are in the A]/Fe buifer range. Organic layers (raw humus), having base saturation of 32 % under beech und 25 % under spruce, are relafively favourable in regard of nutrient supply of the forest stands.
Table 6.2 Proportion ol impaired trees in the IM observation area.
Year Beech Spruce
Distinctly im- Mean Ioss of Distinctly im- Mean loss of paired trees (¾) leaves (¾) paired trees(%) leaves (¾)
1990 38 13 74 3!
1991 44 24 79 34
1992 67 30 79 33
1993 84 34 88 36
1994 95 36 91 40
1995 96 38 87 36
1996 95 36 92 37
1997 53 27 62 39
1998 84 33 83 47
1999 83 32 84 56
The stock of trees is dominated by spruce (Picea abies). Beech (Fagus sytvatica) stands are also present but are found nearly exclusively at the temperature favoured siope posfflons. A prevailing part of the spruce and beech stand shows distinct features of impairment (defoliation, needle Ioss > 25 %, Table 6.2) This is partly due to deposition of air poflutants but espedaily in spruce stands mainly the effect of
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The Finnish Environment 427infestation of the trees with bark beeile. The percentage of significantly defoliated beech trees (55 individuals) increased from about 40 % (1990, 1991) to more than 80
% since 1994, determined by analysis of CIR-photography. The percentage of defoliated spruce trees (253 individuals) changed ftom 74 % (1990) to more than 80
% since 1993. Dead standing trees are amounffng to 14 % of total volume stock at altitudes above 900 m a.s.L. Such development was substantially favoured by climafic condffions (e.g. outstanding dry and hot summers).
Conditions of gaseous atmospheric pollutants in 1999 are characterized by relatively low mean concentrations of suifur dioxide (0.1-1.6g/m3) and nitrogen dioxide (3.7-7.9g/m3). Occasionally occurring peaks were in the range of 11 gfm3 S02 and 24.8g/m3NO2. Mean ozone concenfrations in 1999 ranged between 31 g/
m3 (minimum) and 50 ug/m3.
On base of the deposition data of the years 1992 B 1995 it was calculated the total deposifion by Ulrich’s model using sodium interception to derive partide intercepfion. 56 % and 45 % of total Ca, K, and Mg fluxes were related to leaching processes in spruce (Fi) and beech (Bi) canopy. Particular deposifion was of minor importance (7 % and 3
%).
Total proton deposition was 0.7 to 0.9 kg/ha a in spruce (Fi) and 0.5 to 0.6 kg/ha a in beech (Bi). Sulphur deposition was measured with 11.1 to 14.5 kg/ha a in spruce (Fi) and 8.4 -10.2 kg/ha a in beech (Bi). Nitrogen deposifion amounted to 13.8 to 16.9 kg’ha a in the spruce (Fi) and to 11.6 to 14.2 kgfha a irL the beech stand (Bi).The total deposifion of the whole area was calculated with regard to the surface contribution of spruce and beech stands and under consideration of altitude dependent deposifion rates. The elemental output via headwater was measured by continuous recording of water leveis and by weekly sampies for chemical analysis.
The elemental balance of input (total deposition) and output data showed nearly equffibnum for C1 Ions (-1.1 kg/ha a) and sulphur. There were high values of net output for sodium and caldum and input of protons was completely buffered in the whole area.
On base of the input and output data of inorganic N in the years 1992-1995 it could he shown that there was an average reduction of 44 % (17.2 kg/ha a to 9.7 kg/
ha a). About 90 % of NH4 and 27 % of NO3 ions (related to the total deposition) were retained, but only m the beech stands the ions were nearly completely used for synthesis of biomass. It should he pointed out ffiat the supplying of needies and leafs with nitrogen seemed to he sufficient through ail the years. from both, the elemental balance data of nitrogen and the course of nitrate concentrations m the brook water (run off water from the trout-hrook valley) the Forellenbach valley related to nuffient supplying can he characterized as a nitrogen-saturated ecosystem.
A higher biological actMty of beech stands compared to spruce was confirmed hy outstanding rates of increment, by higher metabolism rates in litter fail, and by higher rates of microbial N liberation and N metabolism. The massive infestation of spruce trees with bark beetle since middle of the nineteenth is stili influendng the elemental fluxes and the cycing of matter. E.g. the nutrient use effidency is reduced because of smaller surfaces (loss of Ieafs as input receptors from the atmosphere) but on the other side the forest decine is attended by smaller requirements for nutrients.
The chemical composffion of soil water was dramatically influenced by the bark beetle effected forest decine and espedaily the concentrations of nitrogen, aluminium, caldum, and magnesium in percolating (gravitafional) water under spruce (surface layer, 40 cm depth, 100 cm depth) showed marked increases by about 2 to 10 fold. Nitrogen concentrations increased since 1996 from about 1-4 mg 1’ to a maximum of 45 mg 1 (199$). In 1999 the concentrations were in a range of 10 to about 25 mg P. The concentrations of aluminium showed a similar pattem. The normal concentration range of 1 to 2 mg4unifi 1996 was sharply increased in the
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years 1997 and 1998 (maximum values of about 27 mg 1) and dropped back again to values of about 7 to 14 mg 1 in 1999. Mthough less pronounced, the concentrations of Ca2- and Mg2-ions (0.02-0.7 mmol 1) showed similar patterns with maximum values in 1998. As results of such changes there is seen an increasing risk of higher nifrate loads in groundwater and surface water and the anyway low nutrient supplying condifion may be strengthened by loss of other nutrients.
The state of the biological parameters (e.g. increment, sprout length, dry maifer and nutrient content of needies and leaf, litterfail)depends on quite different factors which arestifinot understood in detail. There is a high dependency on the weather conditions during a vegetafion penod but temperature and deposition rates are not sufficient to declare the wide ranges of variafion of these parameters dunng the whole observation penod of the integrated monitoring program. E.g., in the years 1992 and 1995 there were high rates of frucbfication (production of beech-nuts) in the beech stand. Among other things such years of outstanding mcrement were charactenzed by an increment decrease of new sprouts inthetreetops of spruces (length of first-order branches dropped down) and a reduced mass of needies and leafs. Following bark beetle infestafion in June 1996, spruce stand f2 (one of two spruce stand observations areas) completely died, while in Fi mdividuals survived.
Beside the normal annual investigations the measurements of the year 2000 wffl addffionally indude some of the opfional subprogrammes which are performed in intervais of 1 to 5 years. Thiswillbe soil chemistry (SC), trunk epiphytes (EP), mventory of birds (55), vegetation (VG-mtensive piot), vegetafion structure and species cover (VS), and partly tree bioelements and tree indicafion (51).
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