A. De Schrijver

Comparison of nitrate leaching under Silver birch (Betula pendula) and Corsican pine (Pinus nigra ssp laricio) in Flanders (Belgium)

In a forest in Flanders (Belgium), situated in a region of intensive livestock production, comparable stands of Corsican pine and silver birch were studied for (1) NH4+ and NO3- concentrations in throughfall water and soil solution and (2) depositions and leaching of NH4+ and NO3- to groundwater. In each stand, throughfall collectors and porous cup lysimeters at three depths (0.1m, 0.5m and 1m) were installed in three replicated sets. Throughfall concentrations of ammonium and nitrate were significantly different for both species as well as soil solution concentrations of nitrate at all depths. Under pine, nitrate concentrations of the soil solution at 1m depth clearly exceeded the Belgian critical level for drinking water (50 mg.1-1). Under birch, this level was only sporadically exceeded. During the sampling period, the depositions of NH4+-N and NO3--N reached respectively 21.6 kg/ha and 6.3 kg/ha under birch and 81.3 and 15.2 kg/ha under Corsican pine. Nitrate-N leaching under silver birch amounted 25.4 kg/ha whereas 56.4 kg/ha was measured under Corsican pine.

Hepatitis B Vaccination Coverage in Belgian Health Care Workers

Abstract.Background:The hepatitis B virus (HBV) vaccination policy for health care workers (HCW) started in Belgium in 1983. An update of vaccination coverage and rates of seroconversion and seroprotection among HCW can give an insight into the actual status and encourage further development of vaccination programs.Patients and Methods:5,064 HCW were tested for anti-HBs. We considered those who had a positive anti-HBs test as seroconverted (SC) and those who had an anti-HBs titer > 10 IU/l as seroprotected (SP).Results:4,771 HCW were eligible for vaccination; 84.9% of them were effectively vaccinated. Among high-risk professions (nurses, care and laboratory workers), 94.79% were vaccinated; for other professions the vaccination coverage was 69.26%. Of the 1,015 non-vaccinated persons, 293 were anti-HBs positive. Among these 54.95% declared they had had a previous hepatitis infection that was serologically proven to be HBV (anti-HBc positive). Of the remaining 132 positives, 70.45% had previously undergone surgery and/or transfusion. Among these 1,015 non-vaccinated HCW, 59.03% were anti-HBs positive. Of these, 373 were nurses, care or laboratory workers. This contrasts with the results for HCW in other sectors, where 11.49% were anti-HBs positive.Conclusion:In our sample, high vaccination, seroconversion and seroprotection rates were achieved, at least for higher risk HCW. The same conclusion can be drawn if we consider hospital departments which carry a higher risk of bloodborne infections.

Patterns of throughfall deposition along a transect in forest edges of silver birch and Corsican pine

In two adjacent forest stands in Flanders, one dominated by Corsican pine (Pinus nigra subsp. laricio Maire) and another dominated by silver birch (Betula pendula Roth), throughfall deposition was monitored along a transect per- pendicular to the forest edge exposed to the prevailing wind direction. Throughfall deposition of Na + ,K + ,C a 2+ ,M g 2+ , NH4 + ,N O3 - ,C l - , and SO4 2- was examined on forest edge patterns expressed in the depth of influence of the edge effect (forest edge distance) and the level of enhancement at the edge (forest edge enhancement). In addition, an integrated forest edge enhancement factor was computed that incorporates these two parameters. Our results show that the edge effects on throughfall deposition of Na + ,C l - , the sum of so-called base cations, the sum of potentially acidifying ions, and the sum of inorganic nitrogen (NH4 + +N O3 - ) are more pronounced in the pine stand. The edge zone of the pine stand receives as a result of the edge effect 9.4 times more extra potentially acidifying ions and 12.7 times more extra inorganic nitrogen than the birch stand. We conclude that an appropriate design or conversion of the edge structure, from high-density Corsi- can pine plantations into lower density deciduous forests, can reduce the input of acidifying and eutrophying pollutants in the forest edge.

A latitudinal gradient in seed nutrients of the forest herb Anemone nemorosa

The nutrient concentration in seeds determines many aspects of potential success of the sexual reproductive phase of plants, including the seed predation probability, efficiency of seed dispersal and seedling performance. Despite considerable research interest in latitudinal gradients of foliar nutrients, a similar gradient for seeds remains unexplored. We investigated a potential latitudinal gradient in seed nutrient concentrations within the widespread European understorey forest herb Anemone nemorosa L. We sampled seeds of A. nemorosa in 15 populations along a 1900-km long latitudinal gradient at three to seven seed collection dates post-anthesis and investigated the relative effects of growing degree-hours >5 °C, soil characteristics and latitude on seed nutrient concentrations. Seed nitrogen, nitrogen:phosphorus ratio and calcium concentration decreased towards northern latitudes, while carbon:nitrogen ratios increased. When taking differences in growing degree-hours and measured soil characteristics into account and only considering the most mature seeds, the latitudinal decline remained particularly significant for seed nitrogen concentration. We argue that the decline in seed nitrogen concentration can be attributed to northward decreasing seed provisioning due to lower soil nitrogen availability or greater investment in clonal reproduction. This pattern may have large implications for the reproductive performance of this forest herb as the degree of seed provisioning ultimately co-determines seedling survival and reproductive success.

Soil Water Chemistry and Revegetation of a Limed Clearcut in a Nitrogen Saturated Forest

A clearcut stand of Pinus sylvestris in Flanders (Belgium) was limed with 3 ton/ha dolomite and reforested with Acer pseudoplatanus and Fagus sylvatica. Soil water monitoring revealed an overall decrease of ion concentrations and an annual peak in September due to seasonal nitrification. Liming reduced concentrations of NO3- and Al3+ and raised concentrations of K+ and Mg2+ and the molar ratio of (Ca+Mg)/Al. Liming also stimulated release of SO42-, which prevented a rise of pH, except during nitrification peaks. Liming had no effect on height increment of Fagus but stimulated Acer, which suffered from severe deficiencies of calcium (Ca), magnesium (Mg), potassium (K), and phosphorus (P) without treatment. Nitrogen (N) was not growth-limiting for Fagus or Acer and liming had no effect on N concentrations in leaves of both species. Liming had a strong impact on ground vegetation. Nutrient-demanding species expanded while species that tolerate nutrient-poor conditions decreased. It is argued that changes in ground vegetation had a greater impact on reduction of NO3- concentration in soil water than increased tree growth.

Negative effects of temperature and atmospheric depositions on the seed viability of common juniper (Juniperus communis)

BACKGROUND AND AIMS Environmental change is increasingly impacting ecosystems worldwide. However, our knowledge about the interacting effects of various drivers of global change on sexual reproduction of plants, one of their key mechanisms to cope with change, is limited. This study examines populations of poorly regenerating and threatened common juniper (Juniperus communis) to determine the influence of four drivers of global change (rising temperatures, nitrogen deposition, potentially acidifying deposition and altering precipitation patterns) on two key developmental phases during sexual reproduction, gametogenesis and fertilization (seed phase two, SP2) and embryo development (seed phase three, SP3), and on the ripening time of seeds. METHODS In 42 populations throughout the distribution range of common juniper in Europe, 11,943 seeds of two developmental phases were sampled. Seed viability was determined using seed dissection and related to accumulated temperature (expressed as growing degree-days), nitrogen and potentially acidifying deposition (nitrogen plus sulfur), and precipitation data. KEY RESULTS Precipitation had no influence on the viability of the seeds or on the ripening time. Increasing temperatures had a negative impact on the viability of SP2 and SP3 seeds and decreased the ripening time. Potentially acidifying depositions negatively influenced SP3 seed viability, while enhanced nitrogen deposition led to lower ripening times. CONCLUSIONS Higher temperatures and atmospheric deposition affected SP3 seeds more than SP2 seeds. However, this is possibly a delayed effect as juniper seeds develop practically independently, due to the absence of vascular communication with the parent plant from shortly after fertilization. It is proposed that the failure of natural regeneration in many European juniper populations might be attributed to climate warming as well as enhanced atmospheric deposition of nitrogen and sulfur.

Nutrient cycling in two continuous cover scenarios for forest conversion of pine plantations on sandy soil. I. Nutrient cycling via aboveground tree biomass.

Conversion of coniferous pine plantations into mixed-species forests on sandy soils is an important concern for forest and nature management in Europe. However, little is know of the effect of the applied sylvicultural strategy on biogeochemical cycling throughout the conversion process. This study examined the aboveground biomass production and nutrient (N, P, K, Ca, and Mg) cycling in terms of litterfall, immobilization in stems and branches, canopy exchange, and yearly root uptake in two scenarios of continuous cover forestry a decade after the first intervention for converting a homogeneous Scots pine (Pinus sylvestris L.) forest. Four regeneration types were studied: silver birch (Betula pendula L.) and pine after a shelterwood cutting and birch and pine after a group cutting. In conclusion, it can be stated that both the tree species and the conversion scenario influence the circulation of nutrients through the forest ecosystem: cycling of N, P, and K is determined by the tree species as well as the...

Nutrient cycling in two continuous cover scenarios for forest conversion of pine plantations on sandy soil, II: nutrient cycling via throughfall deposition and seepage flux

This study examined ion throughfall deposition and seepage fluxes in silver birch (Betula pendula L.) and Scots pine (Pinus sylvestris L.) regenerations a decade after a forest conversion intervention in two continuous cover scenarios (shelterwood cut versus group cut), as well as a 70-year-old control stand of Scots pine. Ion throughfall deposition was significantly influenced by the conversion scenario, being higher in the shelterwood cut than in the group cut. Compared with the control stand, nitrogen and acidifying throughfall deposition was significantly lower (–60%) in all regeneration types except for the birch regeneration under shelter. After shelter removal, ion throughfall deposition was significantly lower in all regeneration types than in the control stand. Seepage of NO3– and SO42– was significantly affected by the tree species, being higher in the birch than the pine regenerations, and SO42– seepage was significantly higher under shelter than in the group cut. After shelter removal, neither...