32
Joan Josep Ibanez, Maria Jose Lled6, Juan Rafael Sanchez and Ferran Roda
Let us only remark here that the consequences of having low production
propagate throughout the ecosystem. Namely, carbon and nutrient fluxes
between the vegetation and the soil will be correspondingly limited.
The objectives of this chapter are: (I) to describe the structure of the holm
oak forests of the Montseny and Prades experimental areas, (2) to estimate
their aboveground biomass and production, and (3) to place them within the
wider context of Mediterranean holm oak forests. Biomass and production
data will be used later in this book, e.g. for modelling ecosystem functioning
(Chap. 12) and computing nutrient pools and fluxes (Chap. 18).
3.2 The Database
Oata used in this chapter have been obtained from forest surveys carried out
in our experimental are,as described in Chapter 2. For Montseny, we will use
data from the Torrent de la Mina catchment at La Castanya, where stem diameters greater than 5 cm were measured at 1.30 m from the ground (dbh).
For Prades, we will use data from the Avic and Teula catchments and from
the plot manipulation experiments in the Torners area (Chaps. 2, 13 and 23).
In the latter case, only data from undisturbed plots are presented (Le. from
control plots or plots before treatment application). At Prades, given the generally shorter stature of the trees, stem diameters greater than 2 cm were
measured at 50 cm from the ground (050). We define the tree layer as those
stems of diameter ~ 5 cm (either dbh or 0 50, depending on site). Stems of diameters 2-5 cm are considered part of the shrub layer. Table 3.1 summarizes
the characteristics of the sampling plots.
Aboveground biomass was estimated through dimensional analysis
(Whittaker and WoodweIl1968). The allometric regressions for holm oak at
Prades (Lled6 1990) and Montseny (Can adell et al. 1988) are as follows:
Prades:
log dry wt. = -1.01 + 2.34 log 0 50 ; r2 = 0.975, P < 0.0001, n = 20;
Montseny: log dry wt. = -1.05 + 2.46 log 0 50; r2 = 0.934, P < 0.000 I, n = 70;
log dry wt. = -0.66 + 2.22 log dbh; r2 = 0.908, P < 0.0001, n = 69,
where dry wt. = total aboveground dry weight (kg); 0 50 = diameter measured
at 50 cm above ground level (cm); dbh = diameter measured at 130 cm above
ground level (cm). At Prades, aboveground biomass of the major companion
tree species was estimated by the species-specific regressions of Lled6 (1990).
Resurveys of the sampling plots furnished data on demographic changes
and diameter growth rates of the trees, thus allowing the computation of
biomass increments. Aboveground net primary production was taken as the
sum of the annual woody biomass increment and the annuallitterfall, which
was collected in traps emptied monthly or every 2 weeks.
Joan Josep Ibanez, Maria Jose Lled6, Juan Rafael Sanchez and Ferran Roda
Let us only remark here that the consequences of having low production
propagate throughout the ecosystem. Namely, carbon and nutrient fluxes
between the vegetation and the soil will be correspondingly limited.
The objectives of this chapter are: (I) to describe the structure of the holm
oak forests of the Montseny and Prades experimental areas, (2) to estimate
their aboveground biomass and production, and (3) to place them within the
wider context of Mediterranean holm oak forests. Biomass and production
data will be used later in this book, e.g. for modelling ecosystem functioning
(Chap. 12) and computing nutrient pools and fluxes (Chap. 18).
3.2 The Database
Oata used in this chapter have been obtained from forest surveys carried out
in our experimental are,as described in Chapter 2. For Montseny, we will use
data from the Torrent de la Mina catchment at La Castanya, where stem diameters greater than 5 cm were measured at 1.30 m from the ground (dbh).
For Prades, we will use data from the Avic and Teula catchments and from
the plot manipulation experiments in the Torners area (Chaps. 2, 13 and 23).
In the latter case, only data from undisturbed plots are presented (Le. from
control plots or plots before treatment application). At Prades, given the generally shorter stature of the trees, stem diameters greater than 2 cm were
measured at 50 cm from the ground (050). We define the tree layer as those
stems of diameter ~ 5 cm (either dbh or 0 50, depending on site). Stems of diameters 2-5 cm are considered part of the shrub layer. Table 3.1 summarizes
the characteristics of the sampling plots.
Aboveground biomass was estimated through dimensional analysis
(Whittaker and WoodweIl1968). The allometric regressions for holm oak at
Prades (Lled6 1990) and Montseny (Can adell et al. 1988) are as follows:
Prades:
log dry wt. = -1.01 + 2.34 log 0 50 ; r2 = 0.975, P < 0.0001, n = 20;
Montseny: log dry wt. = -1.05 + 2.46 log 0 50; r2 = 0.934, P < 0.000 I, n = 70;
log dry wt. = -0.66 + 2.22 log dbh; r2 = 0.908, P < 0.0001, n = 69,
where dry wt. = total aboveground dry weight (kg); 0 50 = diameter measured
at 50 cm above ground level (cm); dbh = diameter measured at 130 cm above
ground level (cm). At Prades, aboveground biomass of the major companion
tree species was estimated by the species-specific regressions of Lled6 (1990).
Resurveys of the sampling plots furnished data on demographic changes
and diameter growth rates of the trees, thus allowing the computation of
biomass increments. Aboveground net primary production was taken as the
sum of the annual woody biomass increment and the annuallitterfall, which
was collected in traps emptied monthly or every 2 weeks.