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Abstract "Heft 18"

Freiburger Bodenkundliche Abhandlungen

Schriftenreihe des

Institut für Bodenkunde und Waldernährungslehre
der Albert-Ludwigs-Universität Freiburg i.Br.
Schriftleitung: F. Hädrich

Heft 18

Erich Mies

Elementeinträge in tannenreiche Mischbestände
des Südschwarzwaldes

Freiburg im Breisgau 1987

ISSN 0344-2691


Elementinput in mixed forest stands of Silver fir, Norway spruce and beech in the Southern Black Forest
At the higher elevations of the Southern Black Forest investigations were carried out to determine the amount and chemical composition of open land precipitation, throughfall, stemflow and litterfall from August 1982 to September 1984. Simultaneously the physical and chemical properties of the soils, the nutritional status and increment growth of the Norway spruce and Silver fir stands was investigated.
Two plots, Kalbelescheuer (KS) and Gabler Eck (GE) are located close to the Rhine Valley at an altitude of 800-900 m a.s.l. The third plot is located 30 km east at a similar altitude in a remote area near St. Blasien (SB). pH, granulation, exchangeable cations, sesquioxides and the total content of N, P, C, S, K, Na, Mg, Ca, Fe, Mn, Al, Zn, Cu, Pb and Cd were analysed for the soils of the trial sites.
The contents of the same elements (except for Na and C) were determinded in the current needles of the first and fourth whorl of spruce and fir.
At the sites near the Rhine Valley the parent material is soli-fluction debris of base poor granite ("Miinsterhalden-granite") (site KS) and base rich gneiss-anatexite (site GE). At the site SB the soil is formed by moraine material of granite and gneiss. The soils of the three plots are distric carabisols with pH (CaCl2) values of 3.2 - 3.9 (plot KS), 4.1 - 4.2 (plot GE) and 3.0 - 4.5 (plot SB).
The total contents of Na, K, Mg, Ca, Fe, Mn, Al, Zn, Cu, Pb and Cd are primorily determined by the mineral composition of the periglacial solifluction debris. The sulfur contents correlate well with the contents of organic material and thus are highest in the soil of SB, as well as the N, P and C contents. The lowest content of exchangeable K, Mg and Ca was found in the soil of KS. At this  site the H contents are higher than the sum of K, Mg and Ca; ca. 90% of the total exchangeable cations are Al ions. In the soil of GE the exchangeable contents of Ca are about ten times, of K and Mg about two to six times higher than in the soil of KS. In 25 cm soil depth at site SB (comparable to the Ah-horizon of KS) similar contents of exchangeable K, Mg, Ca, H and Al were found as in the KS soil. The high humus content of the profile SB is related to higher contents of exchangeable Mg and Ca in the upper 20 cm of the solum. The foliar analysis indicates a low status of nutrition particulary for K and Ca of Norway spruce, and for Ca of Silver fir at site KS. At all investigated sites the Mg supply of both species is sufficient. The content of ca. 1 mg-g-1 d.m. S in the current needles does not indicate an increased atmospheric load of sulphurdioxide.
The Pb contents of 0.3 - 0.9 ug-g-1 d. m. in the current needles are distinctly lower than the values of former investigations in the Southern Black Forest.
Bulk precipitation was sampled weekly and analized for H+,NH4- N, Na, K, Mg, Ca, Mn, Zn, Cu, Pb, Cd, SO4_S, NO3_N, Cl and PO4-P. Due to similar amounts of bulk precipitation at all sites (1560 mm: average Sept. 82 - August 84) the input data can be compared. Input is higher at the west edge of the Southern Black Forest than at the site SB located more to the east. The smallest differences are found for Na. Thus, trial plots are effected by similar rain events. The different contamination results from the emissions in the Rhine Valley. The mean annual input of H+, NH4 -N, NO3-N and SO4-S at the sites KS and GE is 40 - 50% higher as compared to the site SB. The input of the heavy metals Zn, Cu, Pb and Cd is here also increased. The likewise higher inputs of K and Ca indicate that the industrialized and densly populated Rhine Valley is not only an important emission source of acidic precursors and heavy metals but also of alkaline particles. Similar west-east-differences as for the open land precipitation appear in throughfall chemistry. Among those elements that play a important role in the internal ecosystem flux (K, Mg, Ca and Mn) the input via throughfall is clearly higher than via bulk precipitation. Less pronounced is the increased input of the other elements with exception of NH^-N, Cn and Pb where the input by throughfall is lower than the input by bulk precipitation. In comparison to average deposition data of West Germany the input of Na, Ca, NH4-N, SO4-S and Cl~ of the investigated sites are distinctly lower. Higher inputs are found for NO3-N due to
regional emissions. The inputs of K and Mg are similar to average values. Due to the distance to the Sea coast the values for Na and Cl- are lower than average data of West Germany. The lower input of NH4-N, Ca and SO4-S is a result of the relatively low fraction of dry deposition at the elevations of the investigated plots.
The contribution of the stemflow of Silver fir, investigated for the first time, is less than 1% when related to the amount of water and element load. Nevertheless the calculation of the stemflow input reveals that close to the stem the input of most elements is two fold higher when compared to the whole stand area.
The litterfall analysis also reveals the above mentioned west-east-differences in the contamination of the stands via higher contents of N and Pb in the stands KS and GE as compared to SB.

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