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Abstract "Heft 14"


Freiburger Bodenkundliche Abhandlungen

Schriftenreihe des

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


Heft 14


João B. Silva Ferraz


Standortsbedingungen, Bioelementversorgung und Wuchsleistung
von Fichtenbeständen (Picea abies Karst.) des Südschwarzwaldes



Freiburg im Breisgau 1985

ISSN 0344-2691


Summary:

Forty-seven widely different spruce stands in the southern Black Forest were investigated in this study, in order to elucidate the relationships between nutritional status, heavy metals levels, site factors and growth. All forest sites were situated in granite or gneiss areas or in periglacial solifluctions deposits resulting there from.
The altitude of the sites lay between 450 and 1250 m a.s.l., mostly on slopes with differing exposures. In the low sites, the average rainfall, temperature and vegetative growth duration were, respectively: 1072 mm, 9.2 °C, 172 days. In the high mountain sites, the corresponding values were: 1819 mm, 4.2 °C, 82 days.
The forest stands were aged preponderantly between 40 and 60 years. They were afforestation on sites of old forests or in the 1st. or 2nd. generation following pasture or agricultural utilization.
The majority of the stands grew upon very deep "Braunerde" (brown earths). "Ockererde" (slope gley with oxide enrichment), and "Podsol" occasionly occured.
All soils are either acid or strongly acid with a moderate to low base saturation. The physiological rooting depth is low in the case of "Podsol", "Podsol-Braunerde", "Stagnogley" and "Pseudogley", medium for "Okkererde" and "Moderbraunerden" and high for "Mullbraunerden".
Needles from the current year ("l.Jg.") and from the 4th. growing season ("4.Jg.") as well as those of the topmost litter were analysed to determine the levels of the following elements: N, P, K, Ca, Mg, Mn, Fe, Cu, Zn, Co, Pb, Cd, Be and Al. The levels of these elements were also determined in humus layers and soil horizons for 15 selected sites, for which the total amounts of humus and the elements were also calculated.
The growth of the spruce in the southern Black Forest was primarily dependent upon climate, in particular the temperature. The influence of exposure and humus form was largely an effect of temperature.
An influence of precipitation on growth was not observed, because in normal years this was always sufficient. On the other hand dependence of growth upon topsoil pH, C/N ratio and C/P ratio was detected.
The N and K supply of most of the spruce stands was good; deficiencies did not occur. However, dependence of the N-levels upon temperature and N mineralisation became apparent after stratification according to altitude. Of the elements investigated, only N showed a correlation when the levels in litter were compared with those in needles of the "l.Jg." and "4.Jg.".
The P nutrition was very good. The higher the level of P, the more closely the values measured in both  needle ages resembled one another. The P content of the older needles revealed a relationship to the Ptotai amount in the fine earth.
A greater P amount was found in granite as compared to gneiss sites. However this difference had hardly any effect on the P nutrition of the spruce.
The Ca nutrition was critical: insufficient supply considerably reduced accumulation in the older needles, which better reflected the supply than the younger ones. Ca levels in litter were related to those of the older needles.
All Ca levels were dependent upon Ca amounts in the fine earth, a closer relationship being found with regard to the older needles and the Cacitr acid amounts.
The average Ca content of the older needles from warm, dry sites was more than twice that of those from cool, moist sites.
The Mg supply of younger needles ("l.Jg.") was mostly sufficient. The low values of the older needles clearly revelead, however, a critical or inadequate supply. The differences between the two needle groups became less marked as the supply increased. Virtually no dependence between Mg levels in litter and both needle groups could be detected.
The Mg levels of the younger needles were dependent upon the Mgtotal amounts of fine earth.
The amounts in topsoil from gneiss sites were higher than those from granite sites.
Higher Mg levels were shown by older needles from sites with high temperatures during vegetative growth period (high transpiration).
The Mn nutrition was very good, achieving luxury consumption levels. A large scatter in the needle Mn values was found. The levels were not dependent upon the amounts in soil, but upon Mn mobility, which is larger at granite sites (low pH) than at gneiss sites. Stands on old forest sites revealed lower Mn levels than were found in afforestations following pasture.
The Fe supply was generally very good. Fe content of older needles was only related to that of younger needles at low levels. At higher levels ("l.Jg."), the extent of Fe accumulation was determined by soil type or Fe availability. The Fe content of needle litter was tenfold that of the living needles.
The  Fe supply was more strongly dependent upon availability than upon Fe amounts in soil. The Fe levels in the needles increased with the degree of podsolisation of "Braunerde".
The Cu nutrition was either just above or, in a few cases, below the critical values. No relationship between this parameter and growth could be determined. If nutrition was sufficient Cu levels of the "4.Jg." were lower than those of the "l.Jg."; the reverse was true if nutrition was critical.
A significantly positive correlation existed between the Cu levels in the topsoil and in the "l.Jg." needles. The higher Cu levels found in needle litter were probably due to Cu immissions. This may be seen in a positive light in view of the poor Cu supply at some sites at least.
Zn nutrition was largely critical, and was deficient in some of the higher located stands. In spite of this, no signs of deficiency or reduction in growth were apparent. Evaluation of the Zn nutritional status was only possible by comparing the levels in "l.Jg." and "4.Jg." needles. Differing amounts and/or availability of Zn in soil were only detectable in the older needles. Co levels of both needle age groups were similar. However at low Co levels a relatively higher accumulation in the older needles was found. The large variation in Co levels resulted from dependence on soil factors such as acidity and water regimen. For this reason, Co levels were clearly higher on granite sites despite lower Co amounts.
Stands with lower transpiration rates (high location) revealed lower Co levels in the older needles, which better reflected the site characteristics than the younger needles. Pb levels rose with needle age, i.e. with duration of exposure. The values reported here are higher than those found in subsequent studies. This discrepancy is presumably the result of lower atmospheric Pb levels.
As a result of strong Pb binding to organic material Pb levels were highest in needle litter and humus layers. This accumulation was probably immission-dependent.
At sites with with high precipitation, lower needle ("l.Og.") Pb levels were found.
At the western border of the Black Forest and at sites affected by mountain and valley wind systems,considerably higher Pb levels were determined in the older needles. However all Pb levels may generally be regarded as low.
Cd levels likewise indicated a low degree of immission at the sites. Again, the needle litter showed the highest values. By contrast to the Pb levels, Cd values for the older needles were lower than those of the younger ones.
Since Cd is principally absorbed by the roots its level in needles was influenced by the amount of humus as well as the acidity. Low levels ("l.Jg.") in stands at high locations indicated a stronger leaching of Cd from the needles.
Immited Cd is apparently more clearly reflected in levels in younger needles than in older ones.
Strong variation was observed in Be levels. The accumulation in "4.Jg." needles was clearly related to the levels in the younger needles. The needle litter had the highest Be level, despite the fact that Be is scarcely bound to organic material.
Al levels increased nearly linearly with needle age. Higher values in needles were the result of higher Al mobility in more acidic soils.
Aloxalate  contents of the fine earth were clearly different comparing granite and gneiss sites. The higher Al mobilisation in the soils originating from gneiss was evident from the higher Al levels in both needle age groups.
Stands with deeper root penetration also revealed higher Al levels. Given similar amounts of Al in the soil, more is passively absorbed the better the growth of the stand. No deleterious effects of Al on the trees could be detected.
Relationship between the levels of different bioelements in needles were also investigated. Clear positi.ve correlation between N and K was demonstrated, whereas inverse relationships existed between N - Ca, N - Mg. These result clearly show the antagonism between K - Ca and K - Mg.
Posi-tive correlation also existed between: K - Fe, K - Al, Ca - Mg, Ca - Zn, Fe - Al, Zn - Pb, Zn - Cd, Zn - Co and Pb - Co.
Only a weak negative correlation between the antagonists Ca – Al was found.
The nutrient supply of the stands was largely sufficient so that correlations with growth parameters could hardly be detected, particularly in view of the strong influence of the altitude of the sites.
However N and K were correlated with growth during the previous 5 and 10 years.
A dependence of the top height at age 50 years upon N levels ("l.Jg.") became evident following stratification of the data according to altitude.
It was striking that several growth parameters were positively correlated with Al levels. This clearly contradicts the view that this element exerts a negetative influence on norway spruce growth.
The humus types varied clearly with altitude. Temperature and water principally determined the type and thickness of humus layer. The moder humus form was thicker above granite with low base saturation than above gneiss.
In the former case there was a tendency towards raw humus formation. Previous agricultural utilization could still be detected by its influence on present day humus form. Stands on land previously cultivated had more favourable humus forms. On the other hand pasture, forest meadow and straw utilization showed a negative influence on humus formation.
The widespread occurrence of Lumbricus badensis may be regarded as an important factor for the formation of favourable humus forms.
Total humus amounts clearly increased with altitude. Human activity can have both positive and negative consequences for the amount of humus. A high proportion of the total humus may be stored above the soil in the case of the unfavourable humus forms: for the favourable forms this proportion is at most 5 %.



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