SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...

water content prior soil freezing. In comparison of the two ungrazed sites, soil
water storage is identical in summer but different in winter. In winter, higher liquid
stored water in UG 79 indicates that the long-term ungrazed site is more
effective in preventing soil from freezing.
Amplitude ( o C)
Soil temperature ( o C)
15
12
9
6
3
0
30
20
10
0
-10
-20
WG
2 cm 8 cm 20 cm 40 cm 100 cm
9-Sep 19-Oct 28-Nov 7-Jan 16-Feb 28-Mar 7-May 16-Jun 26-Jul
9-Sep 19-Oct28-Nov 7-Jan 16-Feb28-Mar 7-May 16-Jun 26-Jul
Time (days)
Fig. 6.2. Soil temperature and amplitude in 2, 8, 20, 40, and 100 cm depths in WG
from August 2005 to July 2006.
Fig. 2 shows soil temperature and its amplitude as a function of soil depth
exemplified by the winter grazed site (WG). It is observed that depth variations of
soil temperature are season-dependent. During the summer time, soil
temperature decreases with increasing soil depth, indicating energy transfer
from soil surface to deeper soil layers. On the contrary, during the winter time,
soil temperature increases with increasing soil depth. In contrast to this, during
the whole year, the amplitude decreases with increasing soil depth. Especially at
the 100 cm depth, it keeps constant due to weak energy transfer. Expectedly, the
amplitude fluctuations are largest in the transition period from freezing to
thawing, but relatively constant in other periods. In 2005, the topsoil (2 cm)
began to freeze in 6 th November, i.e. the date from which the daily mean
temperature became successively negative. With increasing soil depth, the
freezing process started later. For instance, the soil at 100 cm depth did not
freeze until 12 th December. Also, the thawing process shows a similar trend with
depth, i.e. the deeper soil layers begin to thaw later. This is consistent with the
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