Zusammensetzung und Speziierung der Bodenlösung eines mit Schwermetallen belasteten kalkreichen Bodens

Composition and Speciation of Soil Solution collected in a Heavy Metal polluted calcareous Soil Close to a brass foundry, which had emitted heavy metal containing dusts for over 80 years, soil water was collected in the topsoil (18 cm) and in the subsoil (40 cm) of a severely polluted Calcic Fluvisol by means of polyethylen suction cups over a period of 2 years. The total metal content of the topsoil (extracted with 2M HNO₃ at 100 °C for 2 hours) was 38 nmol g^?1, 24 μmol g^?1, and 25 μmol g^?1 for Cd, Cu, and Zn, respectively. The mean heavy metal concentrations of the soil solution were 0.5 mol L^?1, 300 nmol L^?1, and 200 nmol L^?1 in the topsoil and 0.6 nmol L^?1, 90 nmol L^?1, and 30 nmol L^?1 in the subsoil for Cd, Cu, and Zn, respectively. Solubility calculations showed that the soil solutions were undersaturated with respect to heavy metal carbonates as well as to hydroxides. It seems that the heavy metal concentration is determined by sorption processes rather than by precipitation. The composition of the soil solution has been shown to be governed by the presence, of calcite, by the soil temperature and by the partial pressure of CO₂ in the soil air. The pCO₂ in the soil air (in both depths) has been estimated at 2 mbar during the winter term and at 20 mbar during the summer term. A corresponding increase of the concentration of macroelements (Ca, Mg, Na) as well as of total dissolved carbonate and of dissolved organic matter (DOC) has been measured in the summer half year. No significant seasonal variations of the heavy metal concentrations were detected and no correlations with concentrations of other components could be found.     

Estimating regional forest productivity and water yield using an ecosystem model linked to a GIS

We used the PnET-II model of forest carbon and water balances to estimate regional forest productivity and runoff for the northeastern United States. The model was run at 30 arc sec resolution (approximately 1 km) in conjunction with a Geographic Information System that contained monthly climate data and a satellite-derived land cover map. Predicted net primary production (NPP) ranged from 700 to 1450 g m² yr¹ with a regional mean of 1084 g m² yr¹. Validation at a number of locations within the region showed close agreement between predicted and observed values. Disagreement at two sites was proportional to differences between measured foliar N concentrations and values used in the model. Predicted runoff ranged from 24 to 150 cm yr¹with a regional mean of 63 cm yr¹. Predictions agreed well with observed values from U.S. Geologic Survey watersheds across the region although there was a slight bias towards overprediction at high elevations and underprediction at lower elevations.Spatial patterns in NPP followed patterns of precipitation and growing degree days, depending on the degree of predicted water versus energy limitation within each forest type. Randomized sensitivity analyses indicated that NPP within hardwood and pine forests was limited by variables controlling water availability (precipitation and soil water holding capacity) to a greater extent than foliar nitrogen, suggesting greater limitations by water than nitrogen for these forest types. In contrast, spruce-fir NPP was not sensitive to water availability and was highly sensitivity to foliar N, indicating greater limitation by available nitrogen. Although more work is needed to fully understand the relative importance of water versus nitrogen limitation in northeastern forests, these results suggests that spatial patterns of NPP for hardwoods and pines can be largely captured using currently available data sets, while substantial uncertainties exist for spruce-fir.     

Growth decline in red spruce and balsam fir relative to natural processes

Average annual growth of 3,001 red spruce (Picea rubens Sarg.) trees on plots randomly located across northern New England and upstate New York shows a regionally consistent decline starting soon after 1960. Depending on location, basal-area increment in 1980 was 13 to 40% less than in the peak growth year around 1960. The growth decline occurs in all size and age classes and is independent of elevation. Balsam fir (Abies balsamea (L.) Mill.) also shows a growth decline, but the start varies by tree age. The growth decline in both species is explainable at least in part by natural growth processes, complicating the task of evaluating the effects of atmospheric deposition.