H. W. Zöttl

Dynamik Der Stickstoffmineralisation Im Organischen Waldbodenmaterial

ZusammenfassungDer Einfluß des Stickstoffgehaltes auf die Mineralstickstoff-Nachlieferung wird in Laborbrutversuchen mit Waldhumusmaterial geprüft. Es zeigt sich eine gewisse Abhängigkeit der Mineralstickstoff-Nachlieferung vom Gesamtstickstoffgehalt des organischen Materials (C : N-Verhältnis).Der Faktor „mikrobielle Zersetzbarkeit“ überlagert jedoch diese Beziehung. Daher kann man aus dem C : N-Verhältnis keine allgemein gültigen Schlüsse auf die Mineralstickstoff-Nachlieferung ziehen. Nur beim Vergleich von Material mit ähnlicher mikrobieller Zersetzbarkeit besteht eine enge Abhängigkeit zwischen den beiden Größen. Eine solche Beziehung ist für die untersuchten Rohhumus- und Moderproben zu erkennen. Bei diesem Humusmaterial liegt die Mineralisationsquote um so höher, je enger das C: N-Verhältnis ist. Die Korrelation ist nach 6 Wochen Brutversuch besser als nach 3 oder 15 Wochen.Für Mullhumus und für Humus aus der Humusstofflage sowie dem A1-Horizont von Bodenprofilen mit organischer Auflage ergeben sich trotz engem C : N-Verhältnis meist nur sehr geringe Mineralisationsquoten. Die Zahlen liegen ähnlich niedrig wie bei ungünstigen Rohhumusformen mit weitem C : N-Verhältnis. Ursache hierfür dürfte der hohe Gehalt dieser Humusformen an stabilen Huminstoffen sein. Proben aus der F-Lage von Moder haben hingegen häufig hohe Mineralisationsquoten. Die höchsten Werte von Brutto-und Nettomineralisation treten bei Material aus der Streulage auf.Mineralstickstoff-Zusätze während der Bebrütung bleiben ohne Einfluß auf den Mineralisationsablauf — außer man gibt Nitrat zu nicht nitrifizierenden Rohhumus-Proben. In diesem Fall ist eine Hemmwirkung auf einen Teil der Mikroflora zu beobachten. Die Kohlendioxyd-Produktion sinkt, die Mineralstickstoff-Anhäufung ist jedoch erhöht. Zu Beginn der Bebrütung zugegebener Mineralstickstoff unterliegt der Immobilisation.SummaryThe influence of the nitrogen content on the mineral-nitrogen supply was investigated in laboratory incubation studies with humus material of forests. It shows a certain dependence of the mineral-nitrogen supply on the total nitrogen content of the organic matter (C : N ratio).However, the factor “microbial decomposability” directly influences this correlation. Therefore one cannot draw generally valid conclusions of the mineral-nitrogen supply from the C : N ratio. Only when comparing material with similar microbial decomposability is there a close correlation between both the quantities. Such a relation is seen for the raw-humus and moss-humus samples which were tested. In this humus material the higher the mineralization rate the lower is the C : N ratio. The correlation after 6 weeks incubation is closer than after 3 or 15 weeks.Mull humus, and also humus from the H-layer and from the A1-horizon of raw-humus profiles generally show very low mineralization rates in spite of their low C : N ratio. These mineralization rates are mostly as low as the rates for poor raw-humus samples with high C : N ratio. The cause is the high content of stable humin substances. In contrast samples from the F-layer of moss humus often have high mineralization rates. The highest values of gross-and net-mineralization appear in material from the L-layer.Addition of mineral-nitrogen during the incubation has no influence on the mineralization of organic nitrogen — except for the addition of nitrate to non-nitrifying raw-humus samples. In this case a check effect upon a part of the microflora is observed. The CO2 production decreases, but the mineral-nitrogen accumulation increases. At the beginning of incubation, added mineral-nitrogen is immobilized.

Heavy metal levels and cycling in forest ecosystems

51 Reents, H., Die Entwicklung des sektoralen Endund Nutzenergiebedarfs in der Bundesrepublik Deutschland, Ber. 1452, KFA Jfilich 1977. 52 Reichelt, G., Zur Frage des Zusammenhangs zwischen Waldsch~iden und dem Betrieb yon Atomanlagen vorlfiufige Mitteilung. Forstwiss. ZentB1. 103 (1984) 290-297. 53 Reichelt, G., Zusammenh/inge zwischen Radioaktivit~it und Waldsterben, in: t~kologische Konzepte, pp. 25-53. Halbjahresschrift der G. M. Pfaff Stiftung, Kaiserslautern 1984. 54 Rentz, O., and Weibel, M., Acid rain, the international problem, in: 6th Int. Conf. on Air Pollution, pp. 1-38. Pretoria, S.A. 1984. 55 Rose, D. J., Miller, M. M., and Agnew, C., Global energy futures and CO2-induced climate change, US Dept. of Commerce, NTIS PB 84-145 895, Washington, DC 1983. 56 Rosenfeld, A.H., Colborne, W.G., Hollowell, C.D., Meyers, S.P., and Schipper, L.J., Building energy use compilation and analysis (BECA): An international comparison and critical review. Pt. A: New Residential buildings. Energy Buildings 3 (1981) 315-332. 57 Ruske, B., und Teufel, D., Das sanfte Energie-Handbuch. rororo actuell, Rowohlt, Reinbek 1980. 58 Sant, R.W., A Strategic Look at Energy Markets 1980-2000: The Least-Cost Energy Strategy Revisited. Carnegie-Mellon Univ. Press, Arlington (Va.) 1981. 59 Scheifele, M., Zum Waldsterben in Baden-Wiirttemberg. Allg. Forstz. 43/44 (1984) 1071-1074. 60 Schfitt, P., Der Wald stirbt am Stress. Bertelsmann, Mfinchen 1984. 61 Seiffert, U., and Walzer, P., Development trends for future passenger cars, paper pres. at 5th Automotive News World Congress, reprint Res. Div., VW, Wolfsburg 1980. 62 SERI (Solar Energy Research Institute), A New Prosperity: Building a Sustainable Energy Future. Brick House, Andover (Mass.) 1981. 63 Sorensen, B., Energy choices: Optimal path between efficiency and cost, paper pres. at 1st U. S.-China Conf. on Energy Res. and Environment, Peking 1982. Experientia 41 (1985), Birkh~iuser Verlag, CH-4010 Basel/Switzerland

Remarks on the effects of nitrogen deposition to forest ecosystems.

The effects of increased deposition of nitrogen compounds on forest sites are discussed based on literature data and own results from both earlier fertilization experiments and the ARINUS study area in the Black Forest. The influence on mycorrhiza is stated suppressive as well as stimulating so that no general conclusion can be drawn. The nitrogen nutrition status of coniferous forests is still sub-optimal over wide areas with a yearly deposition of 10–20 kg N ha-1. Under considerable higher input rates the insufficient supply of other nutrients and imbalances in the nutritional status of trees are possible. When discussing ‘nitrogen saturation’ of ecosystems, the nitrogen storage capacity of soils has to be considered as a decisive factor which varies from site to site. Any actual input/output balance is strongly influenced by the internal turnover processes resulting from former land use.

Zeitliche Änderung der Chlorophyll- und Elementgehalte in den Nadeln eines gelb-chlorotischen Fichtenbestandes

ZusammenfassungDie Gelbfärbung von Fichten im Südschwarzwald betrifft vor allem die älteren Nadeln; der jüngste Nadeljahrgang ist jeweils grün. Wir untersuchten die zeitliche Entwicklung der Vergilbung durch Chlorophyll- und Elementanalysen.Die Vergilbung der letztjährigen Nadeln setzt mit dem Knospenaustrieb im Spätfrühjahr ein und ist mit einer starken abnahme der Gehalte an Mg und Zn gekoppelt. N, P, K, und S verändern sich nur wenig. Fe und Al, weniger stark Ca und Mn, nehmen mit dem Nadelalter zu. Cu, Pb und Cd zeigen keine Korrelation mit dem Vergilbungsgrad Ein Anstieg des Chlorophyllgehaltes ist nur schwach ausgeprägt.Aus dem zeitpunkt des Vergilbens und den Veränderungen der Elementgehalte schließen wir, daß Mobilisierung und Verlagerung von unzureichend angebotenen Nährelementen (Mg, Zn) die Vergilbung der Nadeln maßgeblich beeinflussen.SummaryThe yellow discoloration of spruce in the southern Black Forest primarily affects the older needles; the current years needles remain green.We investigated the chronological development of yellowing through chlorophyll and element analyses.The discoloration of last years needles begins at bud burst in late spring and occurs along with a great decrease in the contents of Mg and Zn. N, P, K. and S are scarcely altered. Fe and Al, less so Ca and Mn, increase with needle age. Cu, Pb, and Cd show no correlation with the degree of yellowing. An increase in chlorophyll content is only weakly pronounced.From the onset of yellowing and the changes in element contents we conclude that mobilization and translocation of the deficient nutrient elements (Mg, Zn) decisively influence needle discoloration.

Die Mineralstickstoffanlieferung in Fichten- und Kiefernbeständen Bayerns

The mineral nitrogen-supply was tested in 47 stands of pine and spruce on different sites in Bavaria using the incubation method. A comparison of the incubation method with the conditions on not too extreme sites shows that the accumulation of mineral-nitrogen, obtained after a comparatively short incubation time (6 weeks) under standard laboratory conditions may be valuable as a standard for the nitrogen-supply on the sites. The net-amount of mineral-nitrogen supplied in the incubation method, or on the sites, represents the only available nitrogen-supply for the higher plants which are competing for it with the microorganisms. The plant root ist not able to use a higher percentage of the grossmineralization. The calculated average annual rate of nitrogen-mineralization (net-amount) in the humus samples tested, amounts to 5% of the total nitrogen. This means a yearly supply of at least 31 kg mineral-nitrogen per hectar (35 pounds per acre). For mesophytic sites, with not too extreme a water-supply, it is demonstrated that in poorly growing stands which are judged by the results of needle analyses as being poor in nitrogen, the mineral nitrogen-supply of the soil is also low. There is a close correlation between the mineral nitrogen values of the incubation method (converted to kg/ha by means of the thickness of humus layers) and the nitrogen content of needles of pine- and sprucestands. A similar close correlation exists between needle nitrogen and tree growth, and between mineral-nitrogen supply of the soil and tree growth. Also the carbon:nitrogen-ratio of the F-layer gives information about the mineral nitrogen-supply of the soil. Comparison of pine and spruce on the basis of equal wood production, shows similar demands as regards the mineral nitrogen-supply for both tree species.

Element budgets of two contrasting catchments in the Black Forest (Federal Republic of Germany)

Abstract Rainfall and throughfall inputs of all major cations and anions, via open-field bulk precipitation and canopy throughfall, are compared with streamwater outputs in two forested catchments at higher altitudes of the Black Forest. The sites differ considerably in terms of bedrock geology, soil type, soilwater characteristics, topography, and forest management history. Deposition at both sites is almost equal and, in contrast to other forest areas in Central Europe, of a low-to-moderate level. Dry deposition does not seem to play an important role. Distinct differences in the elemental output emerge owing to the differing site conditions. At Villingen, deposited nitrogen is almost totally retained, whereas at Schluchsee, nitrogen output and input are of the same order of magnitude. This is consistent with the different nitrogen nutrition level of the stands, microbial turnover in the soil, and former management practices (change of tree species, excessive nutrient export). Sulphur is not retained in either of the catchments. At Schluchsee, sulphur export exceeds input from canopy throughfall by a factor of 2.5. The higher output rates, both of nitrogen and sulphur at Schluchsee, are due to the much higher microbial mineralization of organic matter as shown by previous incubation tests. Differences in cation and proton export are mainly caused by a different drainage pattern. In contrast to the Schluchsee catchment, where vertical water pathways prevail, the streamwater solute output at Villingen is dominated by a shallow subsurface runoff. Atmospheric deposition is a contributing, but not the dominant, factor in the biogeochemical cycling at these sites. Hence, a generally applicable quantitative definition of ‘critical loads’, especially for nitrogen, is illusory and the use of such numbers will be misleading.

Ernährung und Düngung der Fichte

ZusammenfassungDer Ernährungszustand von Fichte ist durch Nadelanalysen anhand erprobter Grenzwerte gut zu erkennen. Die Versorgung hat sich bei Stickstoff und Phosphor verbessert, bei Kalium verschlechtert. Magnesiummangel tritt verbreitet auf, wenngleich deutliche Erholungen bemerkenswert sind. Toxische Wirkungen von Aluminium und Schwermetallen sind auf Waldstandorten nicht nachgewiesen. Überernährung mit Stickstoff ist nur bei sehr hohem Ammoniumeintrag zu beobachten.Durch Düngung läßt sich festgestellter Nährelementmangel beheben. Bei Magnesiummangel wirkt Magnesiumsulfat rasch und ohne negative Effekte. Auf Rohhumusstandorten ist dolomitischer Kalk empfehlenswert. Düngung und waldbauliche Maßnahmen tragen zur Stabilisierung der Ökosysteme bei.SummaryThe nutritional status of Norway spruce can be well recognized through needle analysis and comparison of findings with approved threshold values. Recently, the nitrogen and phosporus supply has improved, but potassium supply has been impaired. Areas of magnesium deficiency had become widespread, but more recently a remarkable recovery has taken place. Toxic effects of aluminium and heavy metals have not been proven under natural forest conditions. Excessive nitrogen nutrition has only been observed under conditions of high ammonia depositions.Confirmed nutrient element deficiencies can be eliminated through fertilization. In the case of magnesium deficiency, application of magnesium sulfate fertilizer brings about rapid responses without negative effects. On rawhumus sites, dolomitic lime is recommended. Fertilization and appropriate silvicultural measures contribute to further stabilization of the forest ecosystems.Der Ernahrungszustand von Fichte ist durch Nadelanalysen anhand erprobter Grenzwerte gut zu erkennen. Die Versorgung hat sich bei Stickstoff und Phosphor verbessert, bei Kalium verschlechtert. Magnesiummangel tritt verbreitet auf, wenngleich deutliche Erholungen bemerkenswert sind. Toxische Wirkungen von Aluminium und Schwermetallen sind auf Waldstandorten nicht nachgewiesen. Uberernahrung mit Stickstoff ist nur bei sehr hohem Ammoniumeintrag zu beobachten.

Die Wirkung von Ammoniakgas- und Stickstoffsalzdüngung in Kiefernbeständen

Fertilizing experiments have been established in the years 1955/56 in pine stands(Pinus silvestris) of very bad site quality in the forest districts of Amberg and Schwabach (Bavaria). The sites have a pure nutrient supply and have been gathered of forest litter in former time. In the plots unhydrous ammonia is compared with solid nitrogen fertilizers. In part the nitrogen fertilization is combined with application of lime, phosphate and KMg-fertilizer. The effects on the humus, the mineral nutrition of the trees, and their growth are investigated. Solid nitrogen fertilizers had only a weak effect in the soil. Unhydrous ammonia, which was injected in the humus layers and the mineral soil respectively, caused point by point chemical changes of humus and microbial conversions. 2 years after the application no higher mineral nitrogen supply was stated any more by incubation tests. The needle analysis, which were made every autumn showed, that after application of solid N-fertilizer the N-concentration in the half-year old needles had risen strongly (until the value, which is observed in well growing stands) already in the year of fertilization. Unhydrous ammonia caused only a moderate rising of the N-concentration. In the following years until 1961 the concentrations felt down again to the level of the non-treated plots. The weights of the needles increased very much in the first years, especially in the plots with solid N-fertilization. The concentrations of the other important elements remained on the same level. The current tree-growth rised in the 3 years after the year of fertilization in the plots with 200 kg/ha N in solid form at 95 %, in the plots with unhydrous ammonia at 46 %. This means in the case of solid N-fertilization already a lucrative rent.

Transport of trace elements in ecosystems of the Barhalde watershed in the southern Black Forest.

Concentrations of trace elements and macroelements in rainfall, canopy drip, runoff, and soil solution have been determined each week at four free-drained and three hydromorphic sites at an altitude of 1000–1300 meters above sea level in the very humid, cool Black Forest. Among these elements, the turnover of beryllium, cadmium, copper and lead are discussed in detail. Beryllium had the lowest input and the highest output of these four elements. It was primarily mobilized in the mineral topsoil, and only a small amount was readsorbed by humic acids or subsoil or taken up by plants. Lead concentrations were highest in precipitation, but only about 5 percent of the input appeared in the output. Cadmium, Cu, and Pb were all adsorbed by the humus and iron oxide accumulation horizons of podzols and Ockererde. Copper was adsorbed in all soils except podzols, and fixation of Cu was especially obvious in the Ockererde. Cadmium was not highly adsorbed in mineral soil. The recent increase in atmospheric input resulted in an enrichment and rise of turnover for Cd, Cu, and Pb throughout the watershed.

Assessment of the ecological effects of forest fertilization using an experimental watershed approach

In the research project ARINUS, the effects of restabilization measures (fertilization with readily soluble MgSO4) on the element cycling of Norway spruce ecosystems in the Black Forest (SW Germany) are studied. The objective is to quantify the natural and anthropogenic components of element cycling. Interrelations between the terrestrial and aquatic subsystem are assessed using an integrated approach which combines flux measurements in representative plots with input/output balances of small experimental watersheds. The paper discusses the initial effects of a whole-watershed treatment with Kieserite (750 kg ha−1 MgSO4 · H2O) based on the Mg and S cycling in the control watershed. With the fertilizer, 130 kg ha−1 Mg and 170 kg ha−1 S were introduced into the system. Fertilization resulted in increased levels of Mg and S in the needles. Despite high inorganic Al concentrations and extremely low Ca/Al ratios in soil solution, there was no evidence for ‘Al toxicity’. Since fertilizer losses from the system 1 1/2 years (2 growing seasons) after the treatment have been modest, surface water was hardly been affected. More than 75% of the applied Mg has remained in the ecosystem, primarily in the intensively rooted upper soil layer. Also S has been retained to a considerable extent. The mobility of fertilizer sulfate in acidic forest soils is substantially lower than has been hitherto assumed from laboratory experiments. Therefore, fertilization with readily soluble sulfate-based Mg fertilizers is recommended as an efficient and — in comparison to liming — less risky restabilization measure on sites with a high potential for nitrification.