Stand Structure, Aboveground Biomass and Production
39
3.6 Aboveground Production
Net primary production in our experimental areas is rather low, as is usually
the case in holm oak forests. In the Avic catchment at Prades, total aboveground production during the period 1981-1986 was only 5.0 Mg ha- I year-I.
At Montseny, the mean aboveground primary production of the tree layer in
18 closed-canopy plots was 6.3 Mg ha- I year-I. These production rates are
much lower than the averages for temperate deciduous (10.0 ± SD 2.8 Mg ha- I
year-I) and temperate coniferous forests (8.4 ± SD 2.8 Mg ha- I year-I; Cole
and Rapp 1981). Figure 3.2 shows how holm oak allocates the net aboveground production to the main tree components. About half of the annual
aboveground production is devoted to leaf production, and 32-38% to production of woody tissues (wood and bark of boles and branches). Reproductive investment in male inflorescences and fruits consumes 8-11 % of the
aboveground production. Production of the shrub and field layer was very
small at both sites. Net primary production has not been corrected for the
minor consumption by phytophagous animals. There was no outbreak of
defoliating insects in our experimental areas during the studied periods, and
the consumed foliage was typically well below 10% of standing leaf biomass.
Mean fine litterfall in Prades varied between 2.2 and 5.8 Mg ha- I year-I,
depending on period, site and topographic position. Our best current estimate of the mean litterfall in the Avic catchment (3.4 Mg ha- 1 year-I) is
higher than the previously reported value (2.2 Mg ha- I year-I; Bellot et al.
1992) which was a 7-year average obtained in the upper part of the catchment where production is limited by thin soils. On the south-facing slope of
Tomers (Prades), the mean litterfall during 5 years was 4.2 Mg ha- I year- I
(V. Diego, unpubl. data). In the Montseny catchment, litterfall production in
Prades
leaves
2.3
Montseny
leavea
2.4
Fig. 3.2. Allocation of net aboveground primary production (Mg ha- I year-I) of the tree layer
into major components for Prades (Avic; 1981-1986 for woody biomass increment; 1982-1992
for Iitterfall) and Montseny (closed-canopy plots in the Torrent de la Mina catchment; 19851988 for woody biomass increment; 1985-1987 for Iitterfall)
39
3.6 Aboveground Production
Net primary production in our experimental areas is rather low, as is usually
the case in holm oak forests. In the Avic catchment at Prades, total aboveground production during the period 1981-1986 was only 5.0 Mg ha- I year-I.
At Montseny, the mean aboveground primary production of the tree layer in
18 closed-canopy plots was 6.3 Mg ha- I year-I. These production rates are
much lower than the averages for temperate deciduous (10.0 ± SD 2.8 Mg ha- I
year-I) and temperate coniferous forests (8.4 ± SD 2.8 Mg ha- I year-I; Cole
and Rapp 1981). Figure 3.2 shows how holm oak allocates the net aboveground production to the main tree components. About half of the annual
aboveground production is devoted to leaf production, and 32-38% to production of woody tissues (wood and bark of boles and branches). Reproductive investment in male inflorescences and fruits consumes 8-11 % of the
aboveground production. Production of the shrub and field layer was very
small at both sites. Net primary production has not been corrected for the
minor consumption by phytophagous animals. There was no outbreak of
defoliating insects in our experimental areas during the studied periods, and
the consumed foliage was typically well below 10% of standing leaf biomass.
Mean fine litterfall in Prades varied between 2.2 and 5.8 Mg ha- I year-I,
depending on period, site and topographic position. Our best current estimate of the mean litterfall in the Avic catchment (3.4 Mg ha- 1 year-I) is
higher than the previously reported value (2.2 Mg ha- I year-I; Bellot et al.
1992) which was a 7-year average obtained in the upper part of the catchment where production is limited by thin soils. On the south-facing slope of
Tomers (Prades), the mean litterfall during 5 years was 4.2 Mg ha- I year- I
(V. Diego, unpubl. data). In the Montseny catchment, litterfall production in
Prades
leaves
2.3
Montseny
leavea
2.4
Fig. 3.2. Allocation of net aboveground primary production (Mg ha- I year-I) of the tree layer
into major components for Prades (Avic; 1981-1986 for woody biomass increment; 1982-1992
for Iitterfall) and Montseny (closed-canopy plots in the Torrent de la Mina catchment; 19851988 for woody biomass increment; 1985-1987 for Iitterfall)