INFLUENCE OF VEGETATION COVER ON THERMAL REGIME OF MOUNTAINOUS
CATCHMENTS
1
Miroslav Tesar1, Miloslav Sir1, Lubomir Lichner2, Eva Zelenkova3
Institute for Hydrodynamics, Academy of Sciences of CR, Pod Patankou 5, 166 12 Praha 6,
Czech Republic. (msir@mereni.cz; tesarihas@iol.cz)
2 Institute of Hydrology, Slovak Academy of Sciences, Racianska 75, 831 02 Bratislava 38,
Slovak Republic. lichner@uh.savba.sk
3 National Park of the Sumava Mts., 1. Maje 260, 385 01 Vimperk, Czech Republic.
The influence of deforestation and recurrent afforestation on the thermal regime was studied in
the National Park of the Sumava Mts. Experimental localities Kout, Doupe and Stolec lie in the cold
climatic zone in the National Park of the Sumava Mts. This region is the part of the metamorphic
complex – Moldanubicum. It is formed mainly by the metamorphosed rocks, paragneiss with smaller
injected localities. Three experimental catchments have very similar natural conditions. They
significantly differ in a vegetation cover only (Tab. 1). Catchments are covered with acid brown soil
developed on paragneiss. Vegetation completely covers soil surface. During the whole vegetation
season soil profile contains sufficient volume of water, and therefore, plant transpiration is not limited
by water shortage.
The Kout catchment is covered by dead forest and herb undergrowth – originally
Calamagrostis villosa-rich typical spruce forest. The height of herbs is about 40 cm. Dead trees are 5
to 10 m high, its density is 200 to 300 pieces per hectare. The Doupe catchment is a clearing covered
by herbs – originally Calamagrostis villosa-rich typical spruce forest. Trees are practically missing, the
height of herbs is about 30 cm. The Stolec catchment is the acidophilous mountain spruce-beech
forest. The majority of trees is older than 140 years (the height is about 29 m), about 20 % of trees are
younger than 40 years (the height is about 6 to 10 m). The herbs are 10 to 20 cm high.
The basic quantities (precipitation total and intensity, air and soil temperatures, global
radiation, suction pressures and soil moistures, discharge in the closure profile) are recorded in
experimental catchments.
Table 1: Characteristics of experimental catchments.
catchment
vegetation cover
Kout
Doupe
dead spruce forest with a clearing covered
herb undergrowth
by herbs
age of former forest (years)
150
150
age of new vegetation cover 0–5
0–5
(years)
catchment area (km 2)
0.1
0.17
elevation (m a.s.l.)
1210–1275
1180–1330
exposition
northern
northern
precipitation total in June– 361.1
342.4
September (mm)
runoff
depth
in
June– 25.6
40.9
September (mm)
runoff coefficient (%)
7.1
11.9
Stolec
mature
forest
130
none
spruce
0.07
1105–1251
northern
322.4
28.1
8.7
Fig. 1 shows the air temperature in the high of 5 cm above soil surface in clearing, dead forest and
mature forest on 19 and 20 August 2002. The increase of daily temperature results from the fact that
the dead non-transpiring stems are more heated during sunshine than the transpiring plant cover. The
heat emitted from the dead stems is the cause of the peak temperature in the midday hours in the
days with a great income of solar energy. Drop in the night temperature is the cause of lower
greenhouse effect of atmosphere. It can be explained so that the dead stems cause a drop in the
green vegetation area, and therefore, a drop in the total transpiration. The lower total transpiration
results in the lower content of vapour in the air. It is the cause of greater emission of heat from the soil
surface at night, accompanied with a drop in night temperature. Statistical characteristics of thermal
regime in forest, clearing and dead forest in the season from 29 July till 16 October 2002 are shown in
Tab. 2.
Conclusions were obtained by the interpretation of measured data: (1) The heat regime of the
catchment covered by the dead forest is less stabilised compared to the stands cover by clearing or
mature forest. (2) The heat regime of catchments covered by mature forest and by herbs is
comparable stabilised.
Results obtained are in a good accordance with the experimental findings gained in other
mountainous catchments in the Czech Republic. If the soil cover contains sufficient amount of water
for plant transpiration and the land is fully covered by transpiring vegetation, then the water- and
thermal regime of the whole landscape is not dependent on the species composition of vegetative
cover (Chlebek, Jarabac, 1994, Tesar et al. 2001). This finding is valid for cold climatic zone during a
vegetation season when the plant transpiration plays a governing role in the solar energy dissipation
(Pokorny, 2000).
Table 2: Statistical characteristics of thermal regime in forest, clearing and dead forest in the season
from 29 July till 16 October 2002.
height/
depth
(cm)
200
5
–15
–60
average (ºC)
forest
clearing
13.6
13.4
12.6
12.3
13.7
13.7
13.0
11.4
dead
forest
14.0
13.6
14.4
11.6
standard deviation (ºC)
forest
clearing dead
forest
2.6
3.8
3.6
2.4
4.4
5.2
0.9
1.1
1.1
0.4
0.5
0.4
variation coefficient (ºC)
forest
clearing dead
forest
6.9
14.7
12.8
5.9
19.3
26.7
0.7
1.3
1.1
0.1
0.3
0.2
Fig. 1: Air temperature in the high of 5 cm above soil surface in clearing, dead forest and mature forest
on 19 and 20 August 2002.
References
Chlebek, A., Jarabac, M. (1994): 40 years of hydrologic research of forest in Beskydy Mts. (in Czech).
Vodni hospodarstvi (Water Management), 44: 21–24.
Pokorny, J. (2000): Dissipation of solar energy in landscape – controlled by management of water and
vegetation. Renewable Energy, 24: 1641–1645.
Tesar, M., Sir, M., Syrovatka, O., Prazak, J., Lichner, L., Kubik, F. (2001): Soil water regime in head
water regions – observation, assessment and modelling. J. Hydrol. Hydromech., 49: 355–375.