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| Titel |
A Comparison of Water Balance Components of a Spruce and a Beech Canopy Based on Parallel Micrometeorological and Plant Physiological Measurements |
| VerfasserIn |
Uwe Spank, Christian Bernhofer, Falko Clausnitzer, Babara Köstner, Kai Schwärzel, Karl-Heinz Feger |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039822
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| Zusammenfassung |
| We present the investigations of water balances of two neighbouring canopies, a spruce and a
beech canopy. The water balances were analyzed on small scale of areas less than 0.5 km2
during two growing seasons. The investigations are based on a combination of different
meteorological (eddy-covariance measurements, EC) and plant physiological measurements
(sap flow measurements, SF), as well as on the integration of measurements of soil moisture.
The periods of investigation were very different concerning weather conditions.
One of the seasons was hot and dry, the other season was cool and rainy. Thus,
we are able to compare both canopies under different, however typical, prevailing
weather.
The first part of our study was the partitioning of gross precipitation P into components:
interception I, canopy drip Pc and stem flow Ps. The main focus was to arrive at net
precipitation Pn to quantify the plant available water Wa. Here, also the partitioning of Pc
into throughfall Pt and canopy drainage Pd was analysed. In the second part we investigated
the evapotranspiration ET as well as its partitioning into transpiration T, interception and soil
evaporation Es. The third part addressed the combination of micrometeorological measuring
methods and measurements of soil moisture Î to close water balance and to estimate seepage
R at canopy scale. In this context measuring errors have significant influences on the
interpretation of results. However, they had been often ignored in former studies.
Here, we try to give a robust approximation of measuring errors for the different
methods.
The analyses of partitioning of P showed that Pn and I were almost identical in both
canopies. That means water input was almost identical in both canopies and was around
two-thirds of P. This statement is confirmed especially against the background of
unavoidable measuring errors. However, the partitioning of Pn was completely different
for both canopies. Ps was 20 - 25% of P and around one-third of Pn at the beech
site. Ps is negligible in the spruce canopy. The statistical analyses of Pc showed
a Pt of 12 % at the spruce site and 14 % at the beech site, which correspond to
expectations, derived from measured sky view coefficients. In this context the important
regulating role of Pt for silvicultural, ecological and hydrological issues becomes
clear.
The analyses of ET, T and I as well as the integration of Î to close of water balance were
complex due to different scales of measurements. Which are different scales of EC
measurements (used for ET) and SF measurements (used for T) as well as spatial
heterogeneity of Î. To overcome the scale problem in components of ET somewhat an
inverse solution of Penman’s approach was used to separate T and I in the EC data. Here we
found: differences in T between both canopies are caused predominately by different Wa in
both canopies. However, influences due to differences of plant physiological characteristics
between beeches and spruces were found to be less important. The potential water supply
depends on two parameters: characteristics of soils and range of rooting zone. Therefore, soil
characteristics determine water balance significantly under all climate conditions.
However, the range of the rooting zone and the specifics of roots are only significant in
droughts and dry periods, when water supply is restricted. Differences in interception
between both canopies were found to be negligible during the growing season. |
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