Seedling Recruitment
Table 7.1. Density of holm oak seedlings8 (mean number of seedlings ha- 1 ± SE)
in plots of different aspect in two study areas at Montseny (El Figar6 and La
Castanya)
Study area
North
East-west
South
El Figar6
5938 ± 1915
3678 ± 1461
1736 ± 433
(n = 10)
(n = 15)
(n = 18)
La Castanya
18024 ± 7777
8279±2724
3409 ± 1116
(n = 17)
(n = 11)
(n = 36)
a Seed-derived individuals so.s m tall.
91
lings is thus greatest on north-facing slopes (i.e., more mesic areas), average
on east/west-facing slopes, and lowest on south-facing slopes (i.e., more xeric
areas; Table 7.1).
The availability of water rather than that of light may also control the
patterns of survival and, growth of holm oak seedlings in various microsites
during early phases following establishment. Espelta (1996) found greater
seedling survival in bare or litter microsites than in stony areas, and lower
seedling growth on mounds than in depressions or flat areas. This trend, also
suggested by Crow (1992) for Quercus rubra seedlings, may be related to differences in water availability: stony sites are drier than bare or litter sites,
while mounds are also drier than depressions or flat areas.
7.3 Responses of Holm Oak Seedlings to Different Light
and Water Levels
It is supposed that the recruitment of tree individuals is controlled by
changes in light levels in relation to the shade tolerance of species (Denslow
1987; Platt and Strong 1989; Whitmore 1989; Bazzaz and Wayne 1994). However, Mediterranean ecosystems are characterized by the scarcity of available
soil water during the warm season. This implies that water availability is also
of prime importance for the distribution of forest species (Pigott and Pigott
1993). Espelta (1996) tested the response of potted holm oak seedlings to
different light and water conditions. Under controlled conditions, he analyzed the effect of light intensity and water availability on survival, growth,
biomass allocation, and the water and gas exchange relations of holm oak
seedlings. A factorial experiment was carried out with five distinct light and
water levels. The five light levels were chosen within the range of light variation found in holm oak forests since the last disturbance (Espelta et al. 1995),
while the five water levels simulated the broad gradient found across the
geographic range of holm oak (Barbero et al.1992; Chap. 1).
The survival rate of potted holm oak seedlings fell under increasing incident radiation and decreasing water availability (Fig. 7.1). Both factors inter-
Table 7.1. Density of holm oak seedlings8 (mean number of seedlings ha- 1 ± SE)
in plots of different aspect in two study areas at Montseny (El Figar6 and La
Castanya)
Study area
North
East-west
South
El Figar6
5938 ± 1915
3678 ± 1461
1736 ± 433
(n = 10)
(n = 15)
(n = 18)
La Castanya
18024 ± 7777
8279±2724
3409 ± 1116
(n = 17)
(n = 11)
(n = 36)
a Seed-derived individuals so.s m tall.
91
lings is thus greatest on north-facing slopes (i.e., more mesic areas), average
on east/west-facing slopes, and lowest on south-facing slopes (i.e., more xeric
areas; Table 7.1).
The availability of water rather than that of light may also control the
patterns of survival and, growth of holm oak seedlings in various microsites
during early phases following establishment. Espelta (1996) found greater
seedling survival in bare or litter microsites than in stony areas, and lower
seedling growth on mounds than in depressions or flat areas. This trend, also
suggested by Crow (1992) for Quercus rubra seedlings, may be related to differences in water availability: stony sites are drier than bare or litter sites,
while mounds are also drier than depressions or flat areas.
7.3 Responses of Holm Oak Seedlings to Different Light
and Water Levels
It is supposed that the recruitment of tree individuals is controlled by
changes in light levels in relation to the shade tolerance of species (Denslow
1987; Platt and Strong 1989; Whitmore 1989; Bazzaz and Wayne 1994). However, Mediterranean ecosystems are characterized by the scarcity of available
soil water during the warm season. This implies that water availability is also
of prime importance for the distribution of forest species (Pigott and Pigott
1993). Espelta (1996) tested the response of potted holm oak seedlings to
different light and water conditions. Under controlled conditions, he analyzed the effect of light intensity and water availability on survival, growth,
biomass allocation, and the water and gas exchange relations of holm oak
seedlings. A factorial experiment was carried out with five distinct light and
water levels. The five light levels were chosen within the range of light variation found in holm oak forests since the last disturbance (Espelta et al. 1995),
while the five water levels simulated the broad gradient found across the
geographic range of holm oak (Barbero et al.1992; Chap. 1).
The survival rate of potted holm oak seedlings fell under increasing incident radiation and decreasing water availability (Fig. 7.1). Both factors inter-