Zentralstelle der Forstverwaltung - Landesforsten Rheinland-Pfalz

Gauger (2010) for the bze ii-plots exceed at
almost all grid points the critical load for acidity.
availability of nutrients
the added up nutrient storage from the organic
layer and the mineral soil down to the root depth
had been used for characterization of the short-
and medium-term nutrient elements supply of
the soil. the nitrogen supply in the root zone is
mainly classified as „medium" and „low". the
frequency distributions of the nitrogen storage
did not change significantly between the bze i
and the bze ii. the C/n ratio and the humus type
were used as indicators for nitrogen turnover. a
slight decrease appears for very wide C/n ratios
and humus types indicating serious decomposition
inhibition like mor humus and raw humus.
also the phosphorus storage mainly lies in the
classification level „medium" and „low" and no
significant changes were found between both
investigations.
the exchangeable fraction is used for the evaluation
of the nutrient supply for calcium, magnesium
and potassium. from the bze i to the bze
ii the calcium and magnesium content increased
considerably in consequence of compensation
liming. the emphasis of the Ca and Mg stock
moved from the classification level “very low”
and “low” to “medium”. on the other hand the
exchangeable potassium supply did not change
significantly. Most of the sites in both surveys
belong to the classification level „low”.
Concerning micronutrients manganese and iron
didn’t show any changes for exchangeable stocks
between the two investigations. no comparison
for copper and zinc is possible, because acid soluble
contents are only available for bze ii.
in a separate study the availability of the nutrient
content for calcium, magnesium and potassium
from the coarse fragments (2 - 63 mm) was checked.
the proportion of these nutrients available
in the coarse soil in relation to the total nutrient
content of the soil varies between less than 1 and
more than 70 percent. however, less than one
quarter of the plots show available fractions of
more than 10 % of the total supply in the coarse
soil.
nitrogen status
Content and storage of nitrogen in the humus
layer and in the mineral soil, C/n ratio, nitrogen
content in the 1:2 extract, nitrogen loss with
seepage water and critical load exceedance by
nitrogen deposition are used as indicators for the
nitrogen status of forest ecosystems. neither the
organic matter storage nor the nitrogen storage
in the humus layer, nor the ratio of nitrogen
storage in the organic horizon of the total nstorage
in humus layer and mineral soil showed
significant changes between the bze i and the
bze ii. so there is no indication of change in the
humus accumulation through exceeding nitrogen
deposition.
normally nine tenths of the forest nitrogen pool
(min1,7, max 21, median 7,0 tn*ha-1) is stored
in the humus layer and the mineral soil. the part
of the nitrogen in the growing stock is on the
average 7 %, the parts in soil vegetation and in
deadwood less than 1 %. the part of plots with
a wide C/n ratio has noticeably declined from
the bze i to the bze ii. the C/n ratios are still
suitable for the range, reported for the respective
natural humus forms however.
the nitrate concentrations of the soil solution
derived from 1:2 extract exceed at a third of the
plots 10 mg/l, at almost a quarter 20 mg/l. Considering
only values ≥ 0,1 mg n/l are considered
no significant differences of nitrate concentration
turned out between the bze i and the bze ii. the
nitrate flow rates in seepage water calculated
from these concentrations in combination with
the results of a water balance model show for almost
half of the points more than 5 kg n/ha*year
and for a quarter of the plots also more than 15
kg n/ha*year.
n deposition rates calculated by Gauger (2010)
for the bze grid points exceed 20 kg n/ha*year
at almost three quarters of the plots. therefore
the values of critical loads for nitrogen are not
maintained in many cases.
Carbon storage
Within the bze ii, the carbon pool was recorded
not only for the humus layer and the mineral soil,
but also for above and below ground tree biomass,
ground vegetation, tree regeneration and
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