48
J. Canadell, A. Djema, B. L6pez, F. 1., S. Sabate, D. Siscart and C.A. Gracia
In this chapter, we synthesize the information available on root system attributes of the Mediterranean evergreen holm oak (Quercus ilex L.), mainly,
but not exclusively, studied in two experimental areas: Montseny (Barcelona)
and Prades (Tarragona) in northeastern Spain (Chap. 2). We describe the
root system structure and its distribution in the soil proflIe, the total root
biomass, which we relate to the aboveground biomass, and the phenology of
fine roots. We expect this information to contribute to a better understanding of holm oak ecology and to the efforts to model system responses under
changing environmental conditions.
4.2 The Database
The data presented in this chapter are the result of various studies that have
been carried out over the past 13 years: root excavation campaigns, root proflIes on road cuts, soil coring, minirhizotron technology, and field observations.
At Montseny, the root systems of 32 single-stemmed holm oaks were excavated in the winter of 1985 in La Castanya (Chap. 2). Of these trees, 20 were
excavated in a mesic site (north-facing slope) near the permanent plot, and
12 in a nearby xeric site (south-facing slope). In addition, three multistemmed holm oaks were excavated at the xeric site. At Prades, the root systems of multi-stemmed holm oaks were dug out during 1993 on the northfacing slope of Torners (Chap. 2), in the context of the thinning experiment
described in Chapter 23. Here, we will use the data from the six trees excavated in the control (unthinned) plots. In all cases, roots were excavated
down to 1-m depth or to the bedrock, whichever came first, and to an end
diameter of 1 cm.
Biomass of roots of 0 < 1 cm was obtained by soil coring down to 0.6 m in
the permanent plot at La Castanya. ProflIes of roots of 0 > 1.5 mm were
studied on various road cuts down to 1.5 m deep in several additional places
in northeast Spain. At Prades, minirhizotron technology was used to study
the dynamics of fine root for a 2.5-year period (1994-1996) in the same plots
where root systems were excavated. Minirhizotron is an in situ nondestructive technique that minimizes point-to-point variation by allowing
repeated measurements at the same point over time (Taylor 1987). In the
stony Prades soils, rigid minirhizotron tubes would not allow a good soiltube contact, thus preventing normal development of fine roots around the
tubes. Instead, inflatable minirhizotrons were used which yielded good quality images (L6pez et al. 1996).
J. Canadell, A. Djema, B. L6pez, F. 1., S. Sabate, D. Siscart and C.A. Gracia
In this chapter, we synthesize the information available on root system attributes of the Mediterranean evergreen holm oak (Quercus ilex L.), mainly,
but not exclusively, studied in two experimental areas: Montseny (Barcelona)
and Prades (Tarragona) in northeastern Spain (Chap. 2). We describe the
root system structure and its distribution in the soil proflIe, the total root
biomass, which we relate to the aboveground biomass, and the phenology of
fine roots. We expect this information to contribute to a better understanding of holm oak ecology and to the efforts to model system responses under
changing environmental conditions.
4.2 The Database
The data presented in this chapter are the result of various studies that have
been carried out over the past 13 years: root excavation campaigns, root proflIes on road cuts, soil coring, minirhizotron technology, and field observations.
At Montseny, the root systems of 32 single-stemmed holm oaks were excavated in the winter of 1985 in La Castanya (Chap. 2). Of these trees, 20 were
excavated in a mesic site (north-facing slope) near the permanent plot, and
12 in a nearby xeric site (south-facing slope). In addition, three multistemmed holm oaks were excavated at the xeric site. At Prades, the root systems of multi-stemmed holm oaks were dug out during 1993 on the northfacing slope of Torners (Chap. 2), in the context of the thinning experiment
described in Chapter 23. Here, we will use the data from the six trees excavated in the control (unthinned) plots. In all cases, roots were excavated
down to 1-m depth or to the bedrock, whichever came first, and to an end
diameter of 1 cm.
Biomass of roots of 0 < 1 cm was obtained by soil coring down to 0.6 m in
the permanent plot at La Castanya. ProflIes of roots of 0 > 1.5 mm were
studied on various road cuts down to 1.5 m deep in several additional places
in northeast Spain. At Prades, minirhizotron technology was used to study
the dynamics of fine root for a 2.5-year period (1994-1996) in the same plots
where root systems were excavated. Minirhizotron is an in situ nondestructive technique that minimizes point-to-point variation by allowing
repeated measurements at the same point over time (Taylor 1987). In the
stony Prades soils, rigid minirhizotron tubes would not allow a good soiltube contact, thus preventing normal development of fine roots around the
tubes. Instead, inflatable minirhizotrons were used which yielded good quality images (L6pez et al. 1996).