Impacts from Deposition on Swedish Forest Ecosystems Identified by Integrated Monitoring

Integrated monitoring of ecosystems (IM) is an international co-operative programme (ICP) to control effects of air pollution and climate change on water, soil and biological systems. It is a part of the Convention on Long-Range Transboundary Air Pollution (CLRTAP) of the United Nations Economic Commission of Europe (UN/ECE). The ICP-IM is undertaken on sites/catchments to investigate acidification, eutrophication and heavy metals with an integrated approach. In Sweden, long-term time series from forest ecosystems, with a long and stable continuity, will reveal trends and changes in processes and enable modelling to be undertaken. Investigations of acidity/alkalinity in relation to mineral and organic acids indicated the importance of atmospheric deposition. Recent results show very high inorganic nitrogen retention (99%), a net loss of sulphur originating mainly from organic horizons, and a high inorganic aluminium content in the illuvial soil horizons which could be detrimental to forests. Forest deficiency could also be caused by an observed ongoing translocation of Zn to deeper soil layers implying a movement towards increased release to surface waters.     

Enigmatic biodiversity correlations: ant diversity responds to diverse resources

A pattern noted in ecology is that diversity at one level begets diversity at other levels. In the case of consumers competing for similar resources, the diversity of those resources is thought to provide some degree of niche diversification in which a diverse set of consumer species can coexist. If, however, the diverse resources are not sufficiently distinct from one another, from the standpoint of the consumer species, such niche diversification will not exist. We experimentally show that a diverse array of twigs attracted 80% more species of twig-nesting ants than a monospecific collection of twigs. The specific tree species from which the twigs were derived did not explain the pattern. It appears that diversity per se at one level (twigs) creates conditions that promote diversity at another level (nesting ants).     

Glutamatergic and dopaminergic neurons mediate anxiogenic and anxiolytic effects of CRHR1

The corticotropin-releasing hormone receptor 1 (CRHR1) critically controls behavioral adaptation to stress and is causally linked to emotional disorders. Using neurochemical and genetic tools, we determined that CRHR1 is expressed in forebrain glutamatergic and γ-aminobutyric acid-containing (GABAergic) neurons as well as in midbrain dopaminergic neurons. Via specific CRHR1 deletions in glutamatergic, GABAergic, dopaminergic, and serotonergic cells, we found that the lack of CRHR1 in forebrain glutamatergic circuits reduces anxiety and impairs neurotransmission in the amygdala and hippocampus. Selective deletion of CRHR1 in midbrain dopaminergic neurons increases anxiety-like behavior and reduces dopamine release in the prefrontal cortex. These results define a bidirectional model for the role of CRHR1 in anxiety and suggest that an imbalance between CRHR1-controlled anxiogenic glutamatergic and anxiolytic dopaminergic systems might lead to emotional disorders.     

Blood parameters in Swedish dairy herds with high or low incidence of displaced abomasum or ketosis

Sixty dairy herds were studied to investigate the association between long-term incidence of displaced abomasum and clinical ketosis and body condition score and blood profiles, including parameters estimating energy metabolism and hepatic lipidosis in the periparturient period and early lactation. Blood samples were taken around parturition and in early lactation from cows without apparent clinical symptoms of metabolic disorders. A difference in metabolism between high and low incidence herds was shown post-partum by a lower metabolic index (the revised Quantitative Insulin Sensitivity Check Index, RQUICKI), and tendencies for higher concentrations of glucose, insulin and non-esterified fatty acids in the high incidence herds. High incidence herds had more cows and produced on average 1400kg energy-corrected milk per cow per year more than the low incidence herds. No differences were found in parameters reflecting liver cell damage. In the first 3weeks post-partum the RQUICKI was a more sensitive marker of herds with a high incidence of displaced abomasum and clinical ketosis than any of the individual parameters, but further research is needed before practical applications of the RQUICKI can be foreseen.     

Metal fluxes to Swedis forest lakes

Data on atmospheric deposition, transport via run-off water and contents in soil were used to estimate the fluxes of Zn, Cd, Cu, Pb, and Hg to Swedish forest lakes. The calculations refer to a hypothetical lake with a surface area of about 9% of the total catchment area. There are clear differences in the pathways and transport mechanisms for the different elements. The dominating pathway for the input of Zn and Cd to lakes is via run-off from the drainage area. About 60 to 95% of the total load comes from run-off, highest in the acidified areas. The acidification status of the soil is by far the most important factor regulating the mobility of these elements. The amounts of Hg and Pb deposited on the drainage area are mainly accumulating in the surficial soil layers. The transport of these elements is primarily associated with humic substances. About 30 to 50% of the total load of Pb and 25 to 75% of the total load of Hg to lakes originates from run-off. The transport mechanisms for Cu are similar to those of Pb and Hg, but due to the lower anthropogenic airborne load, the direct deposition is of less importance.     

Determination of total folate in plant material by chemical conversion into para-aminobenzoic acid followed by high performance liquid chromatography combined with on-line postcolumn derivatization and fluorescence detection

A procedure involving chemical conversion of all forms of folate present in plant material into para-aminobenzoic acid (PABA) and a liquid chromatographic-fluorimetric determination with on-line postcolumn derivatization is reported. All folates are cleaved with liberation of PABA by hydrogen peroxide followed by acid hydrolysis using concentrated hydrochloric acid (37%) at 110 degrees C for 6 h. The reaction yield for individual folates conversion to PABA ranged from 44.4 to 97.3%. PABA could be determined sensitively by on-line postcolumn derivatization with fluorescamine, the detection limit for PABA being 3.02 nM. On the basis of this principle, a method for the determination of total folate in plant material, including a purification step on an affinity column, is presented, which offers a sufficient sensitivity and selectivity for routine analysis of total folate in natural samples. The total folate contents of tomatoes, carrots, white cabbage, and spinach were determined, and the results were quite comparable to the data reported. The recovery of PABA and the comparison of total folate analysis in spinach on different occasions (over 6 months) are also reported. The method is reliable, universal for all folates, including polyglutamate and monoglutamate forms, and eliminates the need for a deconjugation step and multiple conversion reactions.     

Do effects of soil compaction persist after ploughing? Results from 21 long-term field experiments in Sweden

The extent and persistence of the effect of soil compaction in a system with annual ploughing were investigated in 21 long-term field experiments in Sweden with a total of 259 location-years. Crop yield, soil physical properties and plant establishment were determined. All experiments had two common treatments: control (no extra traffic) and compacted (350 Mg km ha⁻¹ of experimental traffic in the autumn prior to ploughing), using a tractor and trailer with traditional wheel equipment and an axle load restricted to 4 Mg. During the rest of the year, both treatments were conventionally and equally tilled. The compaction was repeated each autumn for at least 7 years, and the yield was determined each year until 5 years after the termination of the compaction treatment.

Compaction decreased the porosity and the proportion of large pores and increased the tensile strength of dry aggregates. On clay and loam soils, it decreased the proportion of fine aggregates in the seedbed and the gravimetric soil water content in the seedbed.

The yield in the compacted treatment declined compared with the control during the first 4 years, after which it reached steady state. During this steady state, the compaction treatment caused a yield loss of 11.4%, averaged over 107 location-years. Within 4–5 years after the termination of the compaction treatment, the yield returned to the control level. The average yield loss at individual sites increased with increasing clay content.

Results from additional treatments indicated that yield loss was linearly correlated with the amount of traffic up to 300–400 Mg km ha⁻¹. With greater ground contact pressure or a greater soil water content at time of traffic, there was a greater yield loss.

Soil compaction effects on yield were similar for all spring-sown crops, and the percentage yield loss seemed to be independent of the yield. In a few location-years with winter wheat there was on average no yield decrease.

There were 5.1% less plants in the compacted treatment than in the control. The yield decrease was significantly correlated with the number of plants.

Between years results were highly variable, and no consistent correlations between yield loss and soil water content at the time of traffic or the weather conditions during the growing period were found. Soil compaction affected yield during years with good as well as poor conditions for crop growth.     

Blood pressure response to phenylephrine infusion in halothane-anesthetized dogs given acetylpromazine maleate

To quantitate acetylpromazine-induced alpha-adrenergic receptor blockade, phenylephrine was infused into dogs. The amount of phenylephrine necessary to increase the mean arterial blood pressure (MAP) 50% above base line, with or without the prior administration of acetylpromazine, served to quantify the degree of acetylpromazine-induced alpha-adrenergic receptor blockade. Seven dogs were anesthetized with thiopental, maintained on halothane in oxygen, and mechanically ventilated. All infusions were made through a catheter in the cephalic vein. Continuous recordings were made of MAP and a lead II ECG. After induction of anesthesia, instrumentation, and stabilization of heart rate, MAP, and ventilation, 6 group I dogs were infused with phenylephrine until a 50% increase in MAP was recorded (phenylephrine control). On subsequent research days, each dog was anesthetized, instrumented as described, and given (IV) 1 of 3 dosages of acetylpromazine in the following order--0.05, 0.125, and 0.25 mg/kg. The dose of phenylephrine necessary to increase MAP 50% in the presence of acetylpromazine was recorded. Five group II dogs were studied as in group I, but each dog was given (IM) atropine (0.04 mg/kg) before anesthetization. Two dosages of acetylpromazine were studied in the following order--0.05 and 0.25 mg/kg. Group I dogs, when compared with their phenylephrine controls, were given significantly more phenylephrine to raise MAP 50% at each dose of acetylpromazine studied. The same trend was observed in group II dogs, but at smaller doses of phenylephrine, probably as a result of the positive chronotropic effect of atropine on the heart.