3 Stand Structure, Aboveground Biomass
and Production
Joan Josep Ibanez, Maria Jose Lledo, Juan Rafael Sanchez and Ferran Roda
3.1 Introduction
Holm oak forests are structurally diverse (Gracia and Retana 1996). Marked
variations in the main structural variables, such as stem density, basal area
and canopy height, are induced by gradients of environmental heterogeneity
(David et al. 1979; Barbero 1988; Romane et al. 1988; Floret et al. 1989),
caused by the rough topography of the region and by historical differences in
human use (Di Castri 1973; Terradas 1991; Barbero et al. 1992). Moreover,
holm oak can reproduce through seeds (acorns) or vegetatively (sprouting
from stumps and, to a lesser extent, from roots). Stems of both origins are
usually found in the same stand, but, due to the slow rate of holm oak seedling establishment under managed coppice forests (Espelta et al. 1995; Chap. 7),
restocking of holm oak forests during the cutting cycle is left to occur by
natural regeneration from stump resprouting. Since each stool can produce
large numbers of sprouts after disturbances (Giovannini et al. 1992; Retana
et al. 1992), stem density can be very high in stands that have been harvested
or otherwise disturbed.
Management is thus an essential factor affecting structural development
of holm oak forests. Even protected forests that are now largely unmanaged,
as most of our experimental areas at Prades and Montseny, bear the imprint
of past management in their present stand structure. These forests were coppiced for charcoal at short cutting intervals (typically 10-15 years) until ca.
1950 (Ferres 1984; Lledo et al. 1992; Sect. 1.6). In most areas of Catalonia, including our experimental area at Figaro (Montseny), management of holm
oak forests has now shifted to firewood production by selective cutting repeated at longer intervals (about 20-30 years). In contrast, in other areas of
the Mediterranean Basin holm oak forests are managed mainly through
clear-felling (Romane et al. 1988).
Holm oak forests often have a moderate aboveground biomass and a low
net aboveground primary production. Reasons behind these facts will be explored in this chapter and elsewhere in this book (e.g. Chaps. 10, 12 and 13).
Ecological Studies, Vol. 137
Ferran Roda et al. (eds) Ecology of Mediterranean
Evergreen Oak Forests
© Springer-Verlag, Berlin Heidelberg 1999
and Production
Joan Josep Ibanez, Maria Jose Lledo, Juan Rafael Sanchez and Ferran Roda
3.1 Introduction
Holm oak forests are structurally diverse (Gracia and Retana 1996). Marked
variations in the main structural variables, such as stem density, basal area
and canopy height, are induced by gradients of environmental heterogeneity
(David et al. 1979; Barbero 1988; Romane et al. 1988; Floret et al. 1989),
caused by the rough topography of the region and by historical differences in
human use (Di Castri 1973; Terradas 1991; Barbero et al. 1992). Moreover,
holm oak can reproduce through seeds (acorns) or vegetatively (sprouting
from stumps and, to a lesser extent, from roots). Stems of both origins are
usually found in the same stand, but, due to the slow rate of holm oak seedling establishment under managed coppice forests (Espelta et al. 1995; Chap. 7),
restocking of holm oak forests during the cutting cycle is left to occur by
natural regeneration from stump resprouting. Since each stool can produce
large numbers of sprouts after disturbances (Giovannini et al. 1992; Retana
et al. 1992), stem density can be very high in stands that have been harvested
or otherwise disturbed.
Management is thus an essential factor affecting structural development
of holm oak forests. Even protected forests that are now largely unmanaged,
as most of our experimental areas at Prades and Montseny, bear the imprint
of past management in their present stand structure. These forests were coppiced for charcoal at short cutting intervals (typically 10-15 years) until ca.
1950 (Ferres 1984; Lledo et al. 1992; Sect. 1.6). In most areas of Catalonia, including our experimental area at Figaro (Montseny), management of holm
oak forests has now shifted to firewood production by selective cutting repeated at longer intervals (about 20-30 years). In contrast, in other areas of
the Mediterranean Basin holm oak forests are managed mainly through
clear-felling (Romane et al. 1988).
Holm oak forests often have a moderate aboveground biomass and a low
net aboveground primary production. Reasons behind these facts will be explored in this chapter and elsewhere in this book (e.g. Chaps. 10, 12 and 13).
Ecological Studies, Vol. 137
Ferran Roda et al. (eds) Ecology of Mediterranean
Evergreen Oak Forests
© Springer-Verlag, Berlin Heidelberg 1999