I. Popovici, M. Ciobanu Applied Soil Ecology 14 2000 27–36 33
Fig. 2. Dendrogram showing the clusters of soil nematode communities from grasslands according to the Ics similarity coefficient at generic level sites codes as in Table 1.
developed on podzol and alpine meadow soil lower left-side which, at the same time, show negative
correlations with other soil variables Fig. 3. For a large group of nematode genera from grasslands
evolving on a wide range of soil types, from rendzina to argillic soil lower right-side of Fig. 3, no clear
correlations with environmental variables could be detected.
4. Discussion
Nematode abundance in some European grasslands ranges between 0.5 × 10
6
and 12 × 10
6
individualsm
2
Gerber, 1985; Wasilewska, 1994; Hodda and Wan- less, 1994b; Hanel, 1995; De Goede and Bongers,
1998; Ilieva, 1998. Nematode diversity and abun- dance in grasslands were positively correlated Hanel,
1995 and dependent upon variations in environmen- tal conditions Wasilewska, 1994.
The composition of nematode communities in grasslands is characterized by high specific and
generic richness Wasilewska, 1979, 1994; Gerber, 1985; Popovici, 1993, 1998; Hodda and Wanless,
1994a; De Goede and Bongers, 1994, 1998; Hanel, 1996, 1998; Ilieva, 1998; Popovici and Ciobanu,
1998. The index of generic diversity H
′
described here confirms the results given for grasslands by
Wasilewska 1979, 1994 H
′
= 3.7–4.9 and Hanel
1993 H
′
= 2.4–3.6.
Clear patterns in the trophic structure could be dis- tinguished. The proportion of trophic groups, domi-
nated by plant feeding and bacterial feeding nema- todes, was similar to that recorded for chalk grassland
Hodda and Wanless, 1994b and permanent pastures Wasilewska, 1979, 1994 and Valocka and Sabova,
1997.
Our data on the ratio of Bf + HfOPP show val- ues close to those published by Wasilewska 1994 for
34 I. Popovici, M. Ciobanu Applied Soil Ecology 14 2000 27–36
Fig. 3. Canonical correspondence analysis diagram CCA for 32 soil nematode communities of grasslands from Romania [the numbers represent site numbers Table 1. Abbreviations on arrows: Humus, humus content ; Ntot, total nitrogen ; pH, in water; SB,
total exchangeable bases meq100 g soil; SH, total hydrolytic activity meq100 g soil; CEC, cation exchange capacity ; V, base saturation ; Abbreviations for genera: Agle, Aglenchus; Apha, Aphanolaimus; Apmi, Aporcelaimium; Apmu, Aporcelaimus; Aqua,
Aquatides ; Axon, Axonchium; Buno, Bunonema; Cric, Criconema; Coom, Coomanus; Cple, Ceratoplectus; Epdo, Epidorylaimus; Hemi,
Hemicriconemoides ; Merl, Merlinius; Ogma, Ogma; Ptri, Paratrichodorus; Stei, Steinernema; Tric, Trichodorus; Tyll, Tylencholaimellus].
permanent meadows. The total number of plant feed- ing nematodes is dominated by non-obligatory plant
parasites as shown by the ratio of OPPPf. All these re- sults reflect the different level and distribution of food
sources between various types of grasslands.
Clusters with different similarity of nematode com- munities are presented by Hanel 1995, 1996. Generic
composition of the nematode fauna showed the most stable community in meadows Hanel, 1995.
There are few published results and comments con- cerning correlations of grassland nematode communi-
ties with environmental variables. Such relevant cor- relations with edaphic factors Yeates, 1984, with the
ecosystem type Hanel, 1995 or both biotic and abi- otic variables De Goede and Bongers, 1994 could
contribute to the elucidation of causal relationships between the nematode fauna and physical parameters
of terrestrial habitats.
I. Popovici, M. Ciobanu Applied Soil Ecology 14 2000 27–36 35
5. Conclusions
