The North American long-term soil productivity experiment: Findings from the first decade of research

First decade findings on the impacts of organic matter removal and soil compaction are reported for the 26 oldest installations in the nation-wide network of long-term soil productivity sites. Complete removal of surface organic matter led to declines in soil C concentration to 20 cm depth and to reduced nutrient availability. The effect is attributed mainly to the loss of the forest floor. Soil C storage seemed undiminished, but could be explained by bulk density changes following disturbance and to decomposition inputs of organic C from roots remaining from the harvested forest. Biomass removal during harvesting had no influence on forest growth through 10 years. Soil compaction effects depended upon initial bulk density. Soils with densities greater than 1.4 Mg m⁻³ resisted compaction. Density recovery was slow, particularly on soils with frigid temperature regimes. Forest productivity response to soil compaction depended both on soil texture and the degree of understory competition. Production declined on compacted clay soils, increased on sands, and generally was unaffected if an understory was absent.     

Vitalitätsansprache von Fichten auf der Grundlage spektraler Rückstrahlungsmessungen

Zusammenfassung Ziel des Projekts ist die Erarbeitung spektraler Rückstrahlungscharakteristiken von Einzelb?umen und Bestandesoberfl?chen zur Erfassung und kontinuierlichen Beobachtung von Vitalit?tsunterschieden bzw. Sch?digungen an Waldb?umen, insbesondere an Fichten. (Ammer et al. 1983;Hildebrandt 1976). Die für die Spektroradiometermessungen wichtigen objektunabh?ngigen Einflu?parameter wie Sonnenstand, Me?richtung, Neigungswinkel, ?ffnungswinkel und Beleuchtungsverh?ltnisse sind durch eine Vielzahl von Voruntersuchungen bestimmt worden. Erste Me?ergebnisse an Testfl?chen im H?glwald und im Erbersberger Forst lassen deutliche Reaktionen im Spektralverhalten erkennen, die auf Vitalit?ts- und ph?nologische Unterschiede zurückgeführt werden k?nnen.

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Judging vigor of spruces on the basis of spectral reflection measurements

Summary Objective of the research project is the evaluation of characteristic spectral signatures for single trees and stands to assess and continuously monitor differences in vigor, or damages of trees, respectively, especially for spruce. The object-independent parameters which are important for the spectro-radiometer measurements, such as angle and elevation of the sun, inclination, measuring direction, angle of view, and illumination have been determined by numerous previous investigations. First results from the testsites “H?glwald” and “Ebersberger Forst” show distinct differences in the spectral curves which can be related to different degrees of vigor and phenology.

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Beitrag Nr. 16 der H?glwald-Serie 1986     

Long-term changes in forest floor processes in southern Appalachian forests

Soil nutrient concentrations decreased in an aggrading southern Appalachian forest over a 20-year period. Construction of nutrient budgets showed significant nutrient sequestration aboveground including increased forest floor mass. We hypothesized that the changes in forest floor mass resulted from decreased litter decomposition rates because of decreased litter quality. In 1992 and 1993, we repeated a litter decomposition experiment conducted in 1969 and 1970 to test this hypothesis. In addition, we examined microarthropod populations and functional groups as litter decomposed. For four of the five species tested, first-year decomposition rates were about the same in both experiments. Initial litter nutrient concentrations of P were lower in all tree species in the most recent sampling. N, Ca, and Mg concentrations also declined in some species. These declines often resulted in decreased nutrient release rates during decomposition. Microarthropod populations differed significantly among litter species, as well as between years (probably resulting from differences in growing-season rainfall). For some litter species we found significant relationships between microarthropod populations and nutrient concentration (primarily C and N); however, most r²-values were low. Data suggest that changes in forest floor mass probably resulted from decreased litter quality and that those changes may have an effect on microarthropod populations.