206
A. Escarre, A. Carratahi, A. Avila, J. Bellot, J. Pinol and M. Millan
ha- 1 year- 1 in bulk deposition, 46% corresponded to NH4-N, 28% to NOrN,
and 26% to organic N. If the proportion of organic N was similar in our holm
oak forests, the total N input in bulk deposition should be 7.0 kg ha- 1 year- 1
at Montseny and 4.6 kg ha- 1 year- 1 at Prades. Even these estimates corrected
for organic N are rather low in a European context, and indicate that excessive N deposition is not a major threat to these Mediterranean forests.
The importance of atmospheric inputs in the nutrient dynamics of these
holm oak forests can be evaluated by comparing the magnitude of the input
flux with the intrasystemic nutrient fluxes or pools. Here, we will use the annual nutrient retention in new aboveground woody tissues (Chap. 18) as the
relevant flux for comparison. For N, the input in bulk deposition (corrected
for organic N as explained above) amounted to 152% (Montseny) and 139%
(Prades) of the N yearly incorporated in the aboveground woody biomass.
For S, the relationship between the inputs and the biomass net increment
calculated for the mid 1980s was 74% at Prades, but in later years it should be
lower due to the decreasing trend in S deposition. Bulk precipitation is also
an important input for base cations to these holm oak forests, as dissolved
inputs amounted to the following percentages of the annual aboveground
retention: 28% for K+, 60% for Ca 2 +, and 71 % for Mg2+ at Montseny, and 62,
55 and 100%, respectively, at Prades. Red rains inputs in particulate plus dissolved form accounted for around 60% of the total measured bulk precipitation inputs for these cations (.Avila et al.1997).
In conclusion, bulk precipitation delivers nutrients in amounts that can be
relevant in relation to the needs of these holm oak forests. It is convenient to
remember that bulk precipitation measures only part of the atmospheric inputs to a forest. Dry deposition of gases and aerosols onto forest canopies is
poorly captured by bulk deposition collectors. These additional atmospheric
inputs can be, however, reflected in throughfall and stemflow, which are the
subjects of the next chapter.
References
Aber JD (1992) Nitrogen cycling and nitrogen saturation in temperate forest ecosystems. Trends
Ecol Evol 7:220-224
Abrahamsen G, Seip HM, Semb A (1989) Long term acidic precipitation studies in Norway. In:
Adriano DC, Havas D (eds) Acid precipitation, vol 1. Case studies. Springer, Berlin, pp 137-179
Agren C (1994) New figures presented. Acid News 5:14-15
Avila A (1988) Balan~ d'aigua i nutrients en una conca d'alzinar del Montseny. Estudis i Monografies 13, Diputaci6 de Barcelona, Barcelona
Avila A (1996) Time trends in the precipitation chemistry at a mountain site in north-eastern
Spain for the period 1983-1994. Atmos Environ 30:1363-1373
Avila A, Queralt I, Alarc6n M, Martin-Vide J (1996) African dust over north-eastern Spain: mineralogy and source regions. In: Guerzoni S, Chester R (eds) The impact of African dust
across the Mediterranean. Kluwer, Dordrecht, pp 201-205
A. Escarre, A. Carratahi, A. Avila, J. Bellot, J. Pinol and M. Millan
ha- 1 year- 1 in bulk deposition, 46% corresponded to NH4-N, 28% to NOrN,
and 26% to organic N. If the proportion of organic N was similar in our holm
oak forests, the total N input in bulk deposition should be 7.0 kg ha- 1 year- 1
at Montseny and 4.6 kg ha- 1 year- 1 at Prades. Even these estimates corrected
for organic N are rather low in a European context, and indicate that excessive N deposition is not a major threat to these Mediterranean forests.
The importance of atmospheric inputs in the nutrient dynamics of these
holm oak forests can be evaluated by comparing the magnitude of the input
flux with the intrasystemic nutrient fluxes or pools. Here, we will use the annual nutrient retention in new aboveground woody tissues (Chap. 18) as the
relevant flux for comparison. For N, the input in bulk deposition (corrected
for organic N as explained above) amounted to 152% (Montseny) and 139%
(Prades) of the N yearly incorporated in the aboveground woody biomass.
For S, the relationship between the inputs and the biomass net increment
calculated for the mid 1980s was 74% at Prades, but in later years it should be
lower due to the decreasing trend in S deposition. Bulk precipitation is also
an important input for base cations to these holm oak forests, as dissolved
inputs amounted to the following percentages of the annual aboveground
retention: 28% for K+, 60% for Ca 2 +, and 71 % for Mg2+ at Montseny, and 62,
55 and 100%, respectively, at Prades. Red rains inputs in particulate plus dissolved form accounted for around 60% of the total measured bulk precipitation inputs for these cations (.Avila et al.1997).
In conclusion, bulk precipitation delivers nutrients in amounts that can be
relevant in relation to the needs of these holm oak forests. It is convenient to
remember that bulk precipitation measures only part of the atmospheric inputs to a forest. Dry deposition of gases and aerosols onto forest canopies is
poorly captured by bulk deposition collectors. These additional atmospheric
inputs can be, however, reflected in throughfall and stemflow, which are the
subjects of the next chapter.
References
Aber JD (1992) Nitrogen cycling and nitrogen saturation in temperate forest ecosystems. Trends
Ecol Evol 7:220-224
Abrahamsen G, Seip HM, Semb A (1989) Long term acidic precipitation studies in Norway. In:
Adriano DC, Havas D (eds) Acid precipitation, vol 1. Case studies. Springer, Berlin, pp 137-179
Agren C (1994) New figures presented. Acid News 5:14-15
Avila A (1988) Balan~ d'aigua i nutrients en una conca d'alzinar del Montseny. Estudis i Monografies 13, Diputaci6 de Barcelona, Barcelona
Avila A (1996) Time trends in the precipitation chemistry at a mountain site in north-eastern
Spain for the period 1983-1994. Atmos Environ 30:1363-1373
Avila A, Queralt I, Alarc6n M, Martin-Vide J (1996) African dust over north-eastern Spain: mineralogy and source regions. In: Guerzoni S, Chester R (eds) The impact of African dust
across the Mediterranean. Kluwer, Dordrecht, pp 201-205