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Abstract "Heft 16"


Freiburger Bodenkundliche Abhandlungen

Schriftenreihe des

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


Heft 16


Reinhard Hüttl

"Neuartige" Waldschäden und Nährstoffversorgung von
Fichtenbeständen (Picea abies Karst.) in Südwestdeutschland



Freiburg im Breisgau 1985

ISSN 0344-2691


Summary:

Acute nutritional disturbances are discussed as symptomatic findings for the "new type" of forest decline. The insufficient nutritional status of forest trees is seen as an important disposing stress factor.
To characterize the present-day nutritional status of Norway spruce (Picea abies Karst.) in the Southwest of West-Germany needle samples were taken from 150 sites in fall and winter 1983/84. The sites were chosen for later fertilization trials. Hence, the majority of the trial plots is located on geological units naturally poorly supplied with nutrients. Another objective was to sample only weakly to moderately damaged stands.
The selected plots are on gneiss and granite, on sandstone, on silt loam sites, on acidified moraine debris (RiS and Wiirm moraine) and on poor limestone. Preferably chosen were permeable and acid sites. Due to these site factors unfavorable humus forms are common and the stand age above 60 years dominates.
The investigated spruce stands are (based on the element contents in the needles of the top whorl) mostly well supplied with N. The P supply is at optimum whereas the K, Ca, Mg, Mn, and Zn contents all range from optimum to deficient supply. The Fe and Al values reveal normal concentrations.
The N and P values are positively correlated. Negatively correlated are Ca respectively Mg and Al as well as P and Zn.
The N, P, K, Mg, and Al contents of the current needles of the 1st and 4th whorl show distinct differences. The N and K values are generally higher in the 4th whorl, the P, Mg, and Al contents are significantly lower. The Ca, Zn, and Fe values reveal no differences.
The element contents of current and older needles of the 4th whorl show specific aging tendencies. Fe and Al is accumulated with age, Ca and Mn only when supply is sufficient or good. When the Mg (and Zn) supply is poor, lower Mg (and Zn) contents are found in older needles. The K contents of current and older needles are frequently negatively correlated. N and P values decrease with needle age. The evaluation of the nutritional status is much improved through the analysis of current and older needles.
Heavily discolored spruces (which often also show heavier needle loss) have lower K and partially also lower Zn contents. Yellowing symptoms are correlated with lower Mg, Ca , and Mn values. Reddish-brownish discolored spruces are characterized by low K, but also by low Mg and Ca contents. The damages apparently do not influence the N and P supply.
The P, K, Al, and Zn contents increase with altitude, Ca, Mg, and surprisingly Mn decrease. N and Pe oscillate without any trend. In relation to the site factor exposition Ca respectively Mg and Al as well as K and Mg values show "counteractive" curves, whereas P, K, Fe, and Al behave analogously. N and P contents show a clear relation with the humusform. The P supply is better on sites with duff mull— and rawhumus—like humusforms than on sites with mull. The N supply is lowest on rawhumus. The study of the nutritional status in relation to the geological formations reflects the substrate chemistry. The good respectively optimum N and P supply is confirmed. The K supply shows distinct differences. Good K supply is found on silicate rock; frequently deficient are K contents of spruces on moraine and limestone sites. Characteristically differentiated are the Ca and Al contents. The Mg values vary only to a relatively small extend. The minimum values indicate poor Mg supply on granite and gneiss sites. With the exception of gneiss sites Zn deficiency was detected on all geological formations. Noteworthy are the relatively low Mn contents for the acid, modestly fresh sites of the cristalline Black Forest.
Also for stand parameters relations can be found. With increasing stand age the N, P, and K contents tend to decrease. The Ca and Mg values seem to increase somewhat. Volume growth (DGZ100) and N contents are positively correlated. This also holds true for Mn. The other elements do not indicate any relation with volume growth. With heavier cone production the N, P, and K contents decrease. Mg and Ca increase slightly.
The discussion of the data in relation to growth regions underlines the decisive influence of the geological substrate on the nutritional status of forest stands.
By forming site groups various site factors which are important for nutrient supply can be studied simultaneously. The comparison of selected site groups manifests essential research results very well:
- Between nutritional status and site a close relation does exist. Only N and P supply - generally good or at optimum - is hardly differentiated. Amongst other things this is probably due to the increased N input causing an accelerated N and P mineralization.
- On acid,  base poor crystalline sites the Mg and Ca supply is poor, partially deficient. Granite and gneiss areas differ in Zn supply. Due to the mineral composition Zn supply is better on gneiss. The spruces on granite occasionally reveal Zn
deficiency.
- The status of nutrition of spruce stands on sandstone is similar to that on cristalline rock. However, the Mn values are substantially higher.  Although the substrate is acidic and
permeable no K deficiency was found as frequently observed on gravelly-sandy sites of the Riß and Würm moraine.
- Relatively high are the mean Zn and Mn values on calcerous sites. The often deficient K supply ist amongst other things explained by the K:Ca antagonism.
- Surprising is the widespread- K deficiency on Würm and Riß moraine sites.  It is found especially on loamy substrates. Connected with the K deficiency are often poor or deficient Zn contents. Partially poor is also the Mg and Ca supply.

The observed needle discoloration patterns must be considered as typical symptoms of nutritional disturbances;  for needle discoloration and status of nutrition are closely correlated. Whereas needle loss and element contents are often not correlated. The parameter "needle loss" is obviously unspecific.
Based on historical comparisons the acute and partly "new type" of nutritional disturbances of spruce stands in the moraine area and in the cristalline Black Forest are demonstrated. Striking is the dramatic decrease of K supply on moraine sites within the last two decades. On cristalline rock the appearance of the "new type" of decline (since 1976) coincides with decreasing Mg, and to a certain extend also with lower K, Ca, and Zn values.
The discussed needle analyses results indicate substantial nutritional disturbances. They are to be classified as acute and partly new. This applies to the elements Mg, K, Zn, Ca, and Mn.
In the presented (speculative) hypothesis the adverse influence of air pollutants (especially photooxidants) on the assimilation organs in combination with acid precipitation is seen as the inciting factor. Thus, leaching of physiologically mobil and easily exchangeable elements (K, Zn, Mg; Mn, Ca) is probably increased. The tree's reaction to compensate the nutrient losses from the crown area by increased uptake from the soil conflicts with the often poor nutrient supply of forest soils. This poor nutrient supply was presumably increased by soil acidification due to increased anthropogenic acidity inputs causing higher leaching of nutrient ions (Mg, Ca, K; Mn, Zn) from the top soil (disposing factor). Biotic factors and extreme climatic conditions are considered contributing factors.
For experimental testing of the hypothesis diagnostic fertilization trials were established on 40 sites in southwest Germany. Already within one vegetative period the specific improvement of the nutrient supply especially with Mg, K, Ca, Zn, and Mn had led to a decrease or to the di s appear ence of the symptoms. The needle analytical investigation in fall 1985 confirmed the obvious "revitalization" for the investigated trial plots on very different sites and for different age classes.
The preliminary results of the diagnostic fertilization trials indicate that for forest damages connected with nutritional disturbances the specific and balanced application of nutrients (right dosis) based on the knowledge of the nutritional status leads to the regeneration of the trees. However, once a certain degree of damage has been passed a " revitalization" by fertilization ist not possible any more.



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