Abstract:
As part of an interdisciplinary research program, the
spatial and temporal variability of precipitation and
associated nutrient inputs in southern Ecuador have
been investigated since January 2002. The study site
is located at the northern margin of the Podocarpus
National Park in the vicinity of Loja, about 500 km
south of Quito, at altitudes ranging from 1800 to 3180
m.a.s.l. Due to its low density, the conventional rainfall
station network fails to register the highly variable
distribution of rain whereas fog is not accounted for
at all. Hence, a new measurement infrastructure had
to be installed. For the first time in a tropical montane
forest setting, a Weather Radar was used, covering a
radius of 60 km and reaching from the Amazon Basin
to the coastal plains of the region. Furthermore, a dense
network of sampling stations provided data about the
altitudinal gradient of fog water inputs and the
chemical properties of the different precipitation
types. This combined approach provided important
information on the formative processes of rain events
on the eastern escarpment of the Andes. Rainfall
distribution proved far more variable than previously
known and strongly coupled to the orographic
characteristics of the landscape. Maxima occurred
especially on the exposed mountain slopes in the
eastern parts of the Radar range, whereas the highest
crests of the Andes received less precipitation. The
study area has two cloud condensation levels, occurring
at 1500?2000 m and 2500?3500 m.a.s.l., respectively. Fog was estimated to provide an additional 5?35%
of water to conventionally measured rainfall. As with
rainfall, fog capture exhibited a marked altitudinal
gradient. Precipitation samples were analyzed for their
main chemical properties to calculate spatial gradients
as well as temporal trends of nutrient inputs. Although
average matter fluxes were fairly low, episodic events
contributed relevant amounts to the overall ecosystem
nutrient budget.
