30 I. Popovici, M. Ciobanu Applied Soil Ecology 14 2000 27–36
Table 2 The diversity index H
′
, numbers of taxa genera + species, abundance and trophic group ratios for nematode communities in Romanian grasslands
a
Site H
′
No. taxa Abundance No × 10
6
m
2
Ratio Bf + HfOPP
OPPPf HfBf
1 Bih 3.35
98 0.98
1.4 0.4
0.4 2 Bih
2.48 83
0.80 1.4
0.3 0.2
3 Bih 2.98
76 0.59
3.7 0.4
0.2 4 Vla
2.90 52
1.44 2.7
0.7 0.1
5 Vla 2.87
56 3.13
1.5 0.3
0.3 6 Vla
2.38 50
3.25 5.0
1.0 0.1
7 Vla 3.19
63 1.72
2.2 0.5
0.4 8 Vla
3.32 75
1.01 1.7
0.6 0.3
9 Vla 3.47
67 0.97
1.7 0.5
0.4 10 Vla
2.60 76
1.20 3.9
0.8 0.2
11 Tra 3.12
58 9
0.6 0.4
0.5 12 Tra
2.81 62
0.81 3.2
0.6 0.6
13 Tra 2.60
50 0.60
0.5 0.7
0.8 14 Tra
2.83 61
0.77 0.4
0.6 0.3
15 Met 3.33
97 0.67
3.8 0.6
0.6 16 Clu
3.04 68
0.84 2.2
0.3 0.2
17 Sem 3.13
61 3.55
2.1 0.7
0.4 18 Cer
2.86 40
2.35 2.1
0.4 0.2
19 Meh 2.94
56 1.72
4.4 0.5
1.0 20 Ret
3.30 77
1.93 1.3
0.4 0.2
21 Ret 3.11
99 1.12
4.9 0.5
0.6 22 Ret
3.05 67
0.41 2.4
0.8 0.5
23 Ret 2.80
80 1.60
6.5 0.3
0.5 24 Ret
2.65 70
1.62 4.8
0.2 0.8
25 Ret 3.07
88 0.56
10.9 0.2
0.3 26 Ret
2.94 88
0.74 17.5
0.1 0.4
27 Par 2.65
46 1.35
0.8 0.6
0.1 28 Par
2.85 60
0.68 2.8
0.4 0.3
29 Ciu 3.33
70 4.26
4.4 0.6
0.3 30 Has
3.45 78
0.57 3.2
0.6 0.4
31 Has 3.26
54 3.24
2.9 0.6
0.3 32 Rod
2.66 55
8.57 2.0
0.2 0.3
33 Cal 3.44
82 1.03
2.1 0.4
0.3 34 Cal
3.31 67
0.83 1.7
0.6 0.2
35 Bar 3.08
80 0.54
1.7 0.3
0.4 36 Gur
3.16 71
3.24 3.4
0.9 0.1
a
Bf + HfOPP — ratio of bacterial and hyphal feeding nematodes to obligatory plant parasites, OPPPf — ratio of obligatory plant parasites to total plant feeding nematodes, HfBf — ratio of hyphal feeding to bacterial feeding nematodes.
dance of genera, Shannon’s diversity index H
′
and similarity of nematode communities were analyzed
using the BIODIV program Baev and Penev, 1995. The ordination of samples 32 sites, nematode genera
and their relationships with environmental variables were analyzed by the canonical correspondence anal-
ysis method CCA using the CANOCO program Ter Braak, 1986, 1987. The genera abundance data were
transformed to logx + 1. Four sites nos. 13, 14, 17 and 22, without environmental data, were left out of
the CCA analysis.
3. Results
Nematode abundance in the 36 grasslands stud- ied ranged between 0.41 × 10
6
and 8.57 × 10
6
individualsm
2
Table 2. The abundance ranges
I. Popovici, M. Ciobanu Applied Soil Ecology 14 2000 27–36 31
Table 3 Composition of nematode feeding groups in various soil types and plant associations
Site Soil type
Plant association Bacterial
Plant Hyphal
Omni- Predators
feeding feeding
feeding vorous
1 Bih Brown earth
Festuco rubrae –Agrostetum
17 43
7 26
7 2 Bih
Rendzina Lolio
–Trifolietum repentis 20
58 5
12 5
3 Bih Alluvial vermic soil
Lolio –Trifolietum repentis
46 37
9 5
3 4 Vla
Acid brown,andic soil Scorsonero
–Festucetum nigricantis 51
31 8
9 1
5 Vla Feriilluvic podzol
Scorsonero –Festucetum nigricantis
21 60
7 10
2 6 Vla
Acid brown soil Scorsonero
–Festucetum nigricantis 71
15 5
7 2
7 Vla Acid black,andic soil
Scorsonero –Festucetum nigricantis
33 42
13 10
2 8 Vla
Acid brown, andic soil Festuco rubrae
–Agrostetum 33
40 8
13 6
9 Vla Rendzina
Seslerietum rigidae 29
21 12
32 6
10 Vla Brown podzolic soil
Violo declinatae –Nardetum
25 58
5 10
2 11 Tra
Lithic rendzina Melico
–Phleetum montani 31
36 15
15 3
12 Tra Rendzina
Agrostio –Festucetum sulcatae
14 66
8 11
1 13 Tra
Acid brown soil Festuco rubrae
–Agrostetum 11
69 9
11 14 Tra
Brown earth soil Asperulo capitatae
–Seslerietum rigidae 38
42 10
6 4
15 Met Brown earth soil
Festuco rubrae –Agrostetum
28 33
16 16
7 16 Clu
Chernozem Jurineo transsilvanicae
–Stipetum pulcherimae 22
63 5
9 1
17 Sem Alpine meadow soil
Festuco rubrae –Agrostetum
26 46
13 13
2 18 Cer
Typic lithosol Festuco rubrae
–Agrostetum 42
29 9
10 10
19 Meh Terra rossa
Festuco rubrae –Agrostetum
11 34
12 41
2 20 Ret
Acid black soil Festuco rubrae
–Agrostetum 49
30 10
10 1
21 Ret Brown earth soil
Festuco rubrae –Agrostetum
19 58
11 9
3 22 Ret
Alpine meadow soil Campanulo
–Juniperetum 21
52 11
12 4
23 Ret Typic lithosol
Poetum mediae 42
28 23
3 4
24 Ret Acid brown soil
Potentillo –Festucetum airoidis
24 46
20 5
5 25 Ret
Rendzina Festucetum xanthinae
48 28
13 9
2 26 Ret
Rendzinic lithosol Festucetum xanthinae
40 32
16 7
5 27 Par
Lithic podzol Violo declinatae
–Nardetum 27
62 3
5 28 Par
Alpine meadow soil Violo declinatae
–Nardetum 37
43 12
5 3
29 Ciu Cambic rendzina
Violo declinatae –Nardetum
41 21
14 18
6 30 Has
Acid brown soil Scorsonero
–Festucetum nigricantis 31
22 12
31 4
31 Has Acid brown soil
Diantho –Festucetum amethistinae
34 25
10 26
5 32 Rod
Alpine meadow soil Primulo
–Caricetum curvulae 21
66 6
5 2
33 Cal Argillic brown soil
Scorsonero –Festucetum nigricantis
25 40
9 18
8 34 Cal
Argillic brown soil Potentillo
–Festucetum airoidis 29
35 7
26 3
35 Bar Argillic brown soil
Festuco rubrae –Agrostetum
21 56
8 11
4 36 Gur
Acid black soil Festuco rubrae
–Agrostetum 52
19 6
21 2
were widest in rendzina 0.56 × 10
6
–4.26 × 10
6
individualsm
2
n = 7 and acid brown soils 0.57 × 10
6
–3.24 × 10
6
individualsm
2
n = 7. A total of 121 genera and 145 species were identi-
fied in soils from the different Romanian grasslands Tables 2–6 in Popovici, 1998; Table 1 in Popovici
and Ciobanu, 1998. There were 33–67 genera present in each site. The lowest diversity was noted in lithosol
18 Cer, 40 taxa represented by 33 genera and 29 identified species and the highest in brown earth
soil 1 Bih, 15 Met, 21 Ret 97–99 taxa repre- sented by 65–67 genera and 73–74 species Table
2. Overall there were 30 dominant nematode genera each representing more than 5.1 of the popula-
tions but only 2–7 were preponderant at any one site.
In alpine grasslands 27 Par, 32 Rod, Aglenchus, Filenchus
and Paratylenchus were the dominant gen- era. In subalpine grasslands, the genera Filenchus,
Acrobeloides , Gracilacus, Paratylenchus, Plectus and
Rotylenchus were prevalent. The genera with max-
imum occurrence in mountainous grasslands were
32 I. Popovici, M. Ciobanu Applied Soil Ecology 14 2000 27–36
Filenchus , Rotylenchus, Acrobeloides, Plectus, Ec-
phyadophora , Paratylenchus, Anaplectus and Tylen-
cholaimus .
The generic diversity H
′
of the 36 sites ranged be- tween 2.38 and 3.47, without clear differences between
the different nematode communities Table 2. Val- ues of the Shannon’s diversity H
′
for communities developed in rendzina, brown earth and acid brown
soils 17 sites had larger ranges 2.38–3.47 than those for communities in lithosol, podzol and alpine meadow
soils 2.65–3.13 nine sites.
The composition of the nematode communities comprised five main trophic groups: plant feeding
Pf, bacterial feeding Bf, hyphal feeding Hf, omnivorous O and predators P. The distribution
of feeding groups differed within the same type of mountainous grassland developed on varied soils
Table 3.
Plant feeding nematodes were the dominant group in 61 of the populations investigated. The bacte-
rial feeding group was dominant in 28 of the sites, mainly in communities developed in rendzina, acid
black soil, acid brown soil and lithosol.
In subalpine and alpine grasslands, plant feeding ne- matodes had higher representation 46–69 in com-
munities developed in acid brown, podzol and alpine meadow soil as compared to those from rendzina and
lithosol where the bacterial feeding group was domi- nant 40–49 Table 3.
The ratios of hyphal to bacterial feeding nematodes HfBf show a constant preponderance of the bacterial
feeding group Table 2. These values are an indicator of good soil fertility in the grasslands studied. The ratio
between nematodes living on bacteria and fungi, and obligate plant parasites Bf + HfOPP was between
0.4 and 6.5, with two exceptions having very high values sites 25 Ret and 26 Ret, subalpine grasslands
developed on rendzina Table 2. The plant feeding group was mainly composed of non-obligatory plant
parasites e.g., subgroups 1e, 1f, of Yeates et al., 1993, which explains the low values of the ratio OPPPf
Table 2.
The nematode communities of 30 grassland sites were grouped into several clusters of affinity, based
on the Czekanowski–Soerensen similarity coefficient of the genera Ics Pesenko, 1982 in Baev and Penev,
1995 Fig. 2. Six of the communities studied from site nos. 3, 5, 6, 16, 18 and 19, had very low affin-
ity values, and were successively excluded from the dendrogram.
At a similarity of 37–40 six main clusters are distinguished, grouping different types of grasslands
and soils. Each of these clusters is subdivided into groups having higher values of the nematode gen-
era affinity. The highest similarity 70–72 was shown by communities of subalpine grasslands on
rendzina sites 25 and 26, followed by those de- veloped on acid brown soil and lithosol sites 23
and 24. At a similarity between 60 and 70 the nematode communities of different types of grass-
lands on brown soil sites 21, 35 and 8, 30, 31 or on acid black and rendzina sites 20, 29 are
grouped.
Generally, the nematode communities developed in oligotrophic soils such as argillic brown, brown pod-
zolic, podzolic and alpine meadow soil sites nos. 10, 17, 22, 27, 28, 32, 35 are grouped apart from
those communities developed in eu-mesotrophic soils brown earth, rendzina sites nos. 1, 2, 14, 15, 25, 26.
CCA was used to assess the relative importance of environmental variables in explaining the patterns of
nematode occurrence in the grasslands. On the CCA diagram Fig. 3, Axis 1 is defined by the soil vari-
ables with long arrows: humus, pH, SB, P
2
O
5
and V; Axis 2 is defined by Ntot and soil type. The
eigen values are : X
1
= 0.155; X
2
= 0.102; genera
environmental correlations are X
1
= 0.927 and
X
2
= 0.947.
Most of the nematode genera are widespread, and are positioned in the center of the diagram.
Grasslands, and nematode genera such as Aquatides, Ceratoplectus
, Paratrichodorus, Coomansus, Ax- onchium
, Epidorylaimus and Chiloplacus in rendzina and brown earth soils sites nos. 1, 9, 21, 25, 26,
located on the upper right-side of the diagram, are positively correlated with soil pH and exchange-
able bases SB Fig. 3. Positive correlations with humus and total nitrogen [Ntot] can also be no-
ticed for communities in grasslands evolving on acid brown soil and lithosol sites nos. 6, 23, 24, located
on the upper left-side of the diagram. The genera Ogma
, Hemicriconemoides, Merlinius, Trichodorus, Criconema
and Aporcelaimus are positioned in this area. Soil type seems to be better correlated with
nematodes such as Aglenchus, Ecphyadophora, Ty- lencholaimellus
and Aporcelaimium from grasslands
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
