1 CREAF, Campus Universitat Autònoma de
Barcelona, E08193 (Cerdanyola del Vallès), Catalonia, Spain
Keywords: terrestrial ecology, forest ecosystem functioning, long-term
trends, streamwater chemistry, atmospheric deposition, Mediterranean
catchment, holm oak, Quercus ilex , Montseny, La Castanya
Introduction and antecedents
Hydrological and biogeochemical studies in the Montseny holm oak
(Quercus ilex ) forests started in 1978 with funding from a
Hispano-American project that allowed the onset of terrestrial ecology
studies in Spain. Later funding was provided by a suite of projects from
the Spanish Government and the European Commission. This research
followed the small catchment approach developed at Hubbard Brook
(Bormann et al. 1979) and, sustained over several decades, has been
instrumental in showing the responsiveness of forested ecosystems to
atmospheric deposition changes (Avila and Rodà 2012; Bernal et al. 2013;
Avila et al. 2020) and the uniqueness of stream N response to deposition
in Mediterranean forests as compared to temperate forests (Templer et
al. 2022). The effects of forest management on (1) stream chemistry has
been modelled (Neal et al. 1995) and that of climate change on stream
chemistry (Avila et al. 1996) and on the habitat suitability for an
endangered amphibian species as well (Ledesma et al. 2019). Mineral
dust, originated in North Africa (Avila et al. 2007) has been shown to
be an important contributor of nutrients and alkalinity to these forest
ecosystems (Avila et al. 1997, 1998). Further research and new
hypothesis testing may take advance of the collected data series in
these long-term study sites. This is the motivation for the publication
of the quality-checked original stream and atmospheric deposition
chemistry files of well curated small catchments at Montseny whose links
accompany this paper.
Site description
Two catchments, named TM9 and TM0, were instrumented in La Castanya
valley (Montseny mountains; 41,774853 °N / 2,351109 °E) in the early
1980s within a broad-scope study on forest ecosystem functioning (Rodà
et al. 1999). A gauging station was built at each site, consisting of a
stilling pond and a V-notch weir. At TM0 the V-notch had a 120° angle,
while the smaller TM9 weir had a 60° opening.
La Castanya valley is 40 km to the NNE of Barcelona and 27 km from the
Mediterranean coast. Climate is subhumid mesomediterranean: annual
precipitation is around 900 mm with a typical summer drought, but
interannual variability is very high. The bedrock is a metamorphic
phyllite, with quartz, chlorite, albite and muscovite as major minerals.
Two catchments were instrumented in Torrent de la Mina stream, a major
stream draining La Castanya valley: TM0, the main catchment and TM9, a
small tributary (Fig. 1, Table 1). Relief is steep and there are some
rock outcrops in the upper slopes of TM0 and in the TM0 stream channel.
TM9 is located in the lower slopes of TM0 and is totally covered by holm
oak. In TM0, two distinct physiographic units can be distinguished:
holm-oak and beech forests on very steep slopes and heathlands and
grasslands in the upland plateau (Fig. 1). Soils in the slopes of TM0
are colluvial, stony, well drained, and spatially heterogeneous due to
the rugged topography. Typically, they are shallow with a 0-5-cm organic
layer and depths varying between 0.25 to 1.5 m (Hereter, 1990, Hereter
and Sánchez 1999). They are classified as Entisols (Lithic Xerorthents)
or Inceptisols (Typic, Lithic or Dystric Xerochrepts; Soil Survey Staff
1992).
Table 1. Site characteristics