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| Titel |
Spatial and temporal variability of throughfall at the plot scale in the Italian pre-Alps |
| VerfasserIn |
Giulia Zuecco, Omar Oliviero, Daniele Penna, Ilja van Meerveld, Luisa Hopp, Giancarlo Dalla Fontana, Marco Borga |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250097026
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| Publikation (Nr.) |
 EGU/EGU2014-12563.pdf |
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| Zusammenfassung |
| The redistribution of rainfall in the forest canopy affects many hydrological and
biogeochemical processes. Although many studies have focused on the quantification of
throughfall, the controls on the spatial variability and temporal persistence of throughfall
patterns are still poorly understood. This study therefore aims to: i) quantify throughfall at
the plot scale for a pre-Alpine forested hillslope in Italy; ii) assess measurement
differences between two different throughfall collectors; and iii) investigate the
spatial and temporal variability of throughfall patterns and their relation to canopy
characteristics.
Throughfall measurements were taken from April to November 2013 in a 500 m2
experimental plot on the hillslope of a small and densely forested catchment (Ressi) in the
Italian pre-Alps. The main tree species in the plot are beech and chestnut. The median
Diameter at Breast Height of the trees in the plot is 4 cm (range 1-61 cm). Two different
rainfall collectors were used: buckets (collecting area: 556 cm2; capacity: 162 mm) and rain
gauges (collecting area: 47 cm2; capacity: 80 mm). Fifty buckets were randomly distributed
in the plot, while 40 rain gauges were installed on a regular grid (spacing 2.5x3 m). One
bucket and one rain gauge collected rainfall in a nearby open area. A tipping bucket rain
gauge was installed in the open area as well. Rainfall and throughfall were measured for 20
events by manually emptying the collectors and measuring the volume of water in the
collectors. Canopy openness was determined by taking pictures with a 24 mm lens upward
from each sampler and selecting thresholds between dark (canopy) and light (sky)
areas.
For the measured events, rainfall in the open area ranged from 4 mm to 122 mm.
Plot-average throughfall for these events ranged between 69%-94% and 68%-100% of
precipitation for the buckets and rain gauges, respectively. Throughfall measured by
the two types of samplers was statistically similar (Mann-Whitney rank sum test,
p>0.05). However, despite the smaller number of rain gauges than the buckets,
the standard deviation and the coefficient of variation were typically higher for
the rain gauges, likely due to their smaller area. Measured throughfall in the plot
ranged between 25%-178% and between 13%-379% of the precipitation in open area
for the bucket and the rain gauge measurements, respectively. This suggests an
important role of dripping points in shaping plot-scale variability in throughfall,
especially during small rainfall events, and underlines the greater variability in
throughfall measured by the rain gauges than by the larger buckets. Throughfall as a
percentage of precipitation tended to increase with increasing rainfall depth and
rainfall intensity. The spatial variability of throughfall, expressed by the coefficient
of variation, decreased asymptotically with increasing total rainfall and rainfall
intensity.
Canopy openness (quantified for buckets) was poorly correlated with the mean relative
difference of throughfall and significantly correlated (r=0.58, p |
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