Invasive speciesZoltán Botta-Dukát, Edit Molnár and Katalin Szitár

Institute of Ecology and Botany of HASbdz@botanika.hu

European contribution to GEO BON, Workshop organised by Biostrat(www.biostrat.org), 25-27 September 2008, Cegléd, Hungary

Biodiversity

Observation

Network

Introduction

Besides habitat loss and fragmentation, biological invasion is a major driver of biodiversity loss. Nature conservation actions need information about invasibility of natural habitats at different scales from the national level to the local fine scale studies.

Materials and methods

The MÉTA-survey provides data on invasion from national to regional scale. Its resolution is 35 ha, but some vegetation properties were estimated only at 5 by 6 km scale. In the framework of the Kiskun LTER finer scale studies were conducted at the natural sandy vegetation of the

Danube-Tisza Interfluve. A fine-scale study on the occurrences of invasive plant species was completed in the open sandy grassland and poplar-juniper thicket complex in a 0.5 km² area in the strictly protected FülöpházaSand Dune Area.

Results

Analysis of the data collected in the MÉTA-survey revealed that the most endangered vegetation in the

region is the complex of open sandy grasslands and poplar-juniper thickets (Figure 1). Riverine forests,which are regarded as highly invasible worldwide are only the second in this respect. Figure 2 shows the majority of stands of this vegetation type,

endangered by invasion. Previous studies show that the main invaders of this vegetation type are Robinia pseudo-acacia and Asclepias syriaca.

Ten woody and one herbaceous invasive species were detected in the studied area. The majority of the woody species prefer the vicinity of poplar or juniper trees for their establishment (Figure 3). Pinusnigra occurs throughout the studied area, and its abundance depends on the distance from propagulesource.

Fig. 1. Proportion of the area threatened by plant invasion in the main vegetation types in Hungary.Fig. 2. Occurrences of

open sandy grasslands in the Kiskunág region at 35 ha resolution according to the META- survey. Stands threatened by invasion marked by red, while uninvaded stands by green hexagons.

0%0%0%0% 20%20%20%20% 40%40%40%40% 60%60%60%60% 80%80%80%80% 100%100%100%100%

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non-invaded area area threatened by invasion

Eu- and mesotrophic wet meadows and sedge beds

Fens

Marshes

Euhydrophyte habitats

Dry deciduous woodlands

Mesic deciduous woodlands

Riverine shrublands and woodlands

Dry and semi-dry closed grasslands

Open sandy grasslands and poplar-juniper thickets

Halophytic habitats

The complexes sandy grassland and poplar-juniper thickets are susceptible to invasion in the Kiskunság Region. The majority of the stands have already been invaded by several non-indigenous plant species or are directly threatened by invasion.

Discussion

Fig. 4. The spread of Asclepias syriaca in the 0.5 km² studied area.

Fig. 3. The occurrences of invasive woody species in the 0.5 km² studied area of the Fülöpháza Sand Dunes.

Asclepias syriaca invades primarily the bottom of the sand dunes, the former habitat of wet meadows (below 110 m) that have been impoverished in species due to the regional decrease of the

water table and became especially vulnerable to invasion (Figure 4).