R. Vanek et Gpj. Draaijers, ESTIMATES OF ATMOSPHERIC DEPOSITION AND CANOPY EXCHANGE FOR 3 COMMON TREE SPECIES IN THE NETHERLANDS, Water, air and soil pollution, 73(1-4), 1994, pp. 61-82
During one year, dry and wet deposition onto thirty forest stands is s
tudied by sampling throughfall and bulk precipitation. Nine measuremen
t sites are situated in Douglas fir (Pseudotsuga menziesii Mirb. Franc
o) stands, ten in Scotch pine (Pinus sylvestris L.) and eleven in Oak
(Quercus robur L.) stands. Because the stands are situated in each oth
er's proximity (i.e. within a radius of approximately 1.4 km) it is as
sumed that they experience an approximately equal air pollution load.
For the acidifying compounds SO42-, NO3- and NH3+ spatial variability
in wet deposition was small within the area studied. Dry deposition, a
s estimated by net throughfall, displayed a much higher spatial variab
ility. Significant differences existed between tree species and growin
g seasons. Douglas fir mostly displayed the highest, Oak the lowest an
d Scotch pine intermediate values for net throughfall fluxes of acidif
ying compounds. The annual net throughfall fluxes for nitrogen compoun
ds were significantly higher for the coniferous tree species than the
broadleaved tree species. For SO42-, however, Oak showed a relatively
high throughfall flux during the summer. By comparing the temporal pat
tern of net throughfall fluxes between the three tree species it was c
oncluded that considerable canopy leaching occurred for SO42-, Mg2+, P
O43-, HCO3- and K+ in Oak stands during the sprouting of leaves in spr
ing. From surface wash experiments in the laboratory it is concluded t
hat canopy leaching of these ions may also be enhanced when Oak leaves
are infected by Oak mildew, a fungal disease caused by the fungus Mic
roshaera aliphilitoides.