34
Joan Josep Ibanez, Maria Jose Lled6, Juan Rafael Sanchez and Ferran Rodil
3.3 Stand Structure
Holm oak is the dominant species in both experimental areas. In Prades, it
accounts for 77-89% of total arboreal basal area (Table 3.2), with Arbutus unedo and Phillyrea latifolia being the more abundant companion trees (Lled6
et al. 1992). In Montseny, holm oak is practically the only species in the tree
layer.
Our holm oak forests show a high stem density, specially in Prades, where
the densities of the tree layer (Dso ~ 5 cm) at the Avic and Teula catchments
average around 4400 stems ha- I , compared to an average of about 2000 stems
ha- I (dbh ~ 5 cm) in the Torrent de la Mina catchment (Table 3.2). Total density of stools (i.e. genetic individuals) of holm oak is much lower, being in the
range of 700-1200 stools ha- I . In Prades, almost all stems are stump sprouts,
with an average of 4.0 sprouts stool- I (SD = 2.4). In contrast, 84% of holm
oak trees in the permanent plot at Montseny are derived from seed. The Torrent de la Mina catchment lies between these two extremes. In addition to
tree-sized stems, there are a large number of shrub-sized stump resprouts,
particularly at Prades where total densities (tree plus shrub layers) of living
stems average about 9000 stems ha- I in the Avic and Teula catchments and 18
500 stems ha- I in the south-facing slope of Tomers. Such extremely high densities are obviously the result of past coppicing, and make these forests difficult to penetrate by the wind and by humans.
Basal area averaged 16 m 2 ha- 1 in the Montseny catchment in 1985 and 3448 m 2 ha- I in the Prades areas (Table 3.2). Nevertheless, it must be taken into
account that basal area has been calculated at 50 cm from the ground in
Prades and at l30 cm in Montseny. The relationship between dbh and Dso for
Table 3.2. Density (stems ha- 1 ), basal area (m 2 ha- 1 ) and aboveground biomass (Mg ha- 1 ) of the
studied holm oak forests. Stem diameters were measured at 50 cm at Prades (Dso ::: 5 cm at Avic
and Teula; Dso::: 2 cm at Tomers) and at 1.30 m (dbh::: Scm) at Montseny
Locality
Site and year
Density
Basal area
Aboveground
biomass
Total
% Holm Total
% Holm
oak
oak
Prades
Avic 1981"
4226 71.6
34.3
80.2
} 104
Teula 1986"
4490 79.5
34.4
77.3
Torners S-facing 1988
18495 81.2
48.4
89.5
128
Montseny Torrent de la Mina, whole
1911 99.1
16.4
99.4
79
catchment 1985 b
Torrent de la Mina,
2645
21.5
104
closed-canopy plots 1985
Permanent plot 1977
2008 99.8
25.7
99.9
160
" If the shrub layer (Dso ::: 2 cm) is included, averaged values for the Avic and Teula catchments
are: density 9178 stems ha- 1 , basal area 37.9 m 2 ha- 1 , and aboveground biomass 113 Mg ha- I •
b Holm oak forest area only.
Joan Josep Ibanez, Maria Jose Lled6, Juan Rafael Sanchez and Ferran Rodil
3.3 Stand Structure
Holm oak is the dominant species in both experimental areas. In Prades, it
accounts for 77-89% of total arboreal basal area (Table 3.2), with Arbutus unedo and Phillyrea latifolia being the more abundant companion trees (Lled6
et al. 1992). In Montseny, holm oak is practically the only species in the tree
layer.
Our holm oak forests show a high stem density, specially in Prades, where
the densities of the tree layer (Dso ~ 5 cm) at the Avic and Teula catchments
average around 4400 stems ha- I , compared to an average of about 2000 stems
ha- I (dbh ~ 5 cm) in the Torrent de la Mina catchment (Table 3.2). Total density of stools (i.e. genetic individuals) of holm oak is much lower, being in the
range of 700-1200 stools ha- I . In Prades, almost all stems are stump sprouts,
with an average of 4.0 sprouts stool- I (SD = 2.4). In contrast, 84% of holm
oak trees in the permanent plot at Montseny are derived from seed. The Torrent de la Mina catchment lies between these two extremes. In addition to
tree-sized stems, there are a large number of shrub-sized stump resprouts,
particularly at Prades where total densities (tree plus shrub layers) of living
stems average about 9000 stems ha- I in the Avic and Teula catchments and 18
500 stems ha- I in the south-facing slope of Tomers. Such extremely high densities are obviously the result of past coppicing, and make these forests difficult to penetrate by the wind and by humans.
Basal area averaged 16 m 2 ha- 1 in the Montseny catchment in 1985 and 3448 m 2 ha- I in the Prades areas (Table 3.2). Nevertheless, it must be taken into
account that basal area has been calculated at 50 cm from the ground in
Prades and at l30 cm in Montseny. The relationship between dbh and Dso for
Table 3.2. Density (stems ha- 1 ), basal area (m 2 ha- 1 ) and aboveground biomass (Mg ha- 1 ) of the
studied holm oak forests. Stem diameters were measured at 50 cm at Prades (Dso ::: 5 cm at Avic
and Teula; Dso::: 2 cm at Tomers) and at 1.30 m (dbh::: Scm) at Montseny
Locality
Site and year
Density
Basal area
Aboveground
biomass
Total
% Holm Total
% Holm
oak
oak
Prades
Avic 1981"
4226 71.6
34.3
80.2
} 104
Teula 1986"
4490 79.5
34.4
77.3
Torners S-facing 1988
18495 81.2
48.4
89.5
128
Montseny Torrent de la Mina, whole
1911 99.1
16.4
99.4
79
catchment 1985 b
Torrent de la Mina,
2645
21.5
104
closed-canopy plots 1985
Permanent plot 1977
2008 99.8
25.7
99.9
160
" If the shrub layer (Dso ::: 2 cm) is included, averaged values for the Avic and Teula catchments
are: density 9178 stems ha- 1 , basal area 37.9 m 2 ha- 1 , and aboveground biomass 113 Mg ha- I •
b Holm oak forest area only.