Changes in organization and dynamics of the sand vegetation
along an ecological gradient
Edit Kovács-Láng*, György Kröel-Dulay, Gábor Fekete,
Sándor Bartha, Sándor Barabás, János Garadnai,
Barbara Lhotsky and Tamás Rédei
Institute of Ecology and Botany, Hungarian Academy of Sciences
H-2163 Vácrátót, Hungary
*corresponding author: [email protected]
Within the European forest-steppe transitional biome, an aridity gradient and the
corresponding changes of the biota can be detected in the Carpathian Basin.
These changes can be studied along a 200 km long NW-SE transect represented by
the Gönyû (at Gyôr), Csévharaszt (at Budapest) and Fülöpháza (at Kecskemét) sites
in Hungary, where the climate becomes drier and the growing season becomes
warmer from Gönyû to Fülöpháza indicating an increase in continentality (Figure 1).
The climatic differences between the two endpoints of the transect are similar to the
projected regional climate changes.
The Pannonian sand
Gönyû
Csévharaszt
Fülöpháza
forest-steppe appears as
a large-scale mosaic of
open sand grasslands,
xerothermic sand oakwoods, mixed juniperpoplar woodlands and
shrublands. While, at
the wet end of the
Figure 1. The frequency of droughts based on the 1931–1998
transect (Gönyû), forest
data series of the Pálfai Drought Indices.
patches cover 60%, the
landscape becomes more
years w/o droughts
slight droughts
severe droughts
open at Fülöpháza,
where small paches of sparse juniper-poplar woodland are scattered in the matrix of
dry sand grasslands (Figure 2).
The soils belong to the coarse sand soil group (Calcaric arenosol). Humus content
decreases and CaCO3 content increases in the SE direction. Soil formation processes
on the NW parts produced slightly developed Rusty-brown (Ramann) forest soils,
while towards the dry end soil profiles are not differentiated.
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a
b
Figure 2. Landscape at Gönyû (a) and Fülöpháza (b).
The analysis of the forest species ranges revealed the existence of a corresponding
floristic gradient in the region (Figure 3).
In the sand grassland the total number
of species as well as that of forest species
decreases, while the proportion of sand
grassland species and annuals of continental and submediterranean character
increases with increasing aridity (Figure
4, Table 1).
Role of disturbances
Natural disturbances are important
drivers of dynamics in arid and semiarid
communities. They generate non-equilibrium patch dynamics which can
maintain biodiversity in the community.
The main disturbing agents are:
• extremities of the limited precipitation,
• physical perturbations of animals,
wind or fires,
• herbivory and grazing.
Figure 3. Edges of regional distribution of forest
species in the Danube-Tisza Interfluve.
The disturbance regimes and recovery processes of the perennial open sand
grassland also change along the aridity gradient. Towards the dry end, general effects
of severe droughts proved to be the most important. Local animal disturbances – wild
boar (Sus scrofa) at the forested Gönyû and wood mouse (Apodemus sylvaticus) at the
open Fülöpháza – affected less than 0.1% of the surface of grasslands.
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Gönyû
Habitat characters
110
20
Total number of species (50 ha)
Number of species characteristic
for sand grasslands (50 ha)
Number of therophytes (16 m2)
Total cover of phanerogams %
Average mass of individuals
of the dominant grass Festuca vaginata (g)
Belowground phytomass per unit green leaves (g/g)
4
70
11.8
1.8
Fülöpháza
53
26
6
35
24.1
5.1
Figure 4 and Table 1. Differences in the composition and structure
of the open perennial sand grassland.
Experimental perturbations (digging of 1 × 1 m plots) and recovery studies showed
a reduction in the number of seedlings on the disturbed areas (Figure 5). While
recovery in the number of species was faster at Fülöpháza, where annuals rapidly
occupied and acquired resources, in the denser grassland at Gönyû, during a slower
process, dicots became dominant.
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a
b
Figure 5. Changes in the number of species after experimental disturbance
at Gönyû (a), and at Fülöpháza (b).
References
Fekete, G., Kun, A., Molnár, Zs. 1999. Chorological gradients in the forest flora of the Danube-Tisza
Interfluve. Kitaibelia 4: 343-346. (in Hungarian)
Kovács-Láng, E., Kröel-Dulay, Gy., Kertész, M., Fekete, G., Bartha, S., Mika, J., Dobi-Wantuch, I., Rédei,
T., Rajkai, K., Hahn, I. 2000. Changes in the composition of sand grasslands along a climatic
gradient in Hungary and implications for climate change. Phytocoenologia 30: 385–407.
Botta-Dukát, Z., Kovács-Láng, E., Rédei, T., Kertész, M. Garadnai, J. 2007. Statistical and biological
sampling in phytosociology: theoretical considerations and a case study. Folia Geobotanica 42:
141–152.
Kovács-Láng, E., Rédei, T., Lhotsky, B., Kröel-Dulay, Gy., Garadnai, J., Barabás, S. 2006. Changes in
diversity and dynamics of open perennial sand grasslands along a climatic gradient. In: Kalapos,
T. (ed.) Flora and vegetation as indicators. Scientia, Budapest, pp. 151–164. (in Hungarian)
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