Eijsackers, H.J.P.

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Development of earthworm populations in abandoned arable fields under grazing management

Wageningen Yield 

Chapter 20 
Development of earthworm 
populations in abandoned arable 
fields under grazing management. 
H.J. P. EIJSACKERS 
20.1 I N T R O D U C T I O N 
An experiment was begun in 1972 on a nature reserve in the southern 
Netherlands with the object of incorporating adjacent abandoned arable 
land into the reserve. Icelandic horses were introduced as herbivores 
additional to the native rabbit population to graze the developing 
vegetation and so maintain the open character of the landscape and merge 
the boundaries between the reserve and the fields. This experiment 
created an opportunity to investigate the development of the earthworm 
population in relation to the vegetation succession. 
The low density of earthworm populations in arable land has been 
attributed partially to mechanical damage during cultivation but Evans 
and Guild (1948) considered the main limiting factor to be the low input 
of suitable plant residues. This study investigated the effect of plant 
residues from the developing vegetation on the earthworm population 
and the influence of earthworm activity on the soil conditions and 
vegetation. 
20.2 STUDY AREA AND SAMPLING M E T H O D S 
The nature reserve Cranendonck occupies 100 hectares of sandy soil 
comprising approximately equal areas of coniferous forest, heath and 
blowing sand, and abandoned arable fields (Fig. 20.1). Ten sampling sites 
were selected in abandoned fields and four in adjacent fields still under 
arable cultivation. Earthworms were sampled from 1975 by handsorting 
duplicate samples (30 x 30 x 30 cm) 3-5 times each year. Soil properties 
241 
242 Ear thworm Ecology 
I I Abandoned arable fields 
\ ^ | Coniferous forest 
\,/',\ Heath and blown sands 
)f Arable fields sampled 
1 -10 Sampling sites 
Fig. 20.1 Plan of Cranendonck nature reserve. 
were determined in 1973 as follows: pH in KCl; organic matter as loss on 
ignition; total N by destruction with phenol-H 2S0 4 + Se and distillation 
of NH 3 ; total P by extraction with Fleischmann acid; total K, total Fe and 
Cu by extraction in 0.1 N HCI+0.4N oxalic acid (1:10). Other workers 
monitored activities of horses and rabbits, and the development of the 
vegetation. 
20.3 F L U C T U A T I O N S I N E A R T H W O R M N U M B E R S 
Lumbricus rubellus comprised 95 % of all the worms sampled. In four sites 
(1-4) in the west of the reserve, numbers showed a distinct decline in 1976 
followed by an increase up to 1979 and a decrease in 1980. In four sites 
(6, 7, 8, 10) in the east of the reserve, numbers increased steadily from 
1975 to 1979 and fell in 1980 (Fig. 20.2). Two other sites (5, 9) showed 
irregular fluctuations and were not analysed further. 
The decrease in 1976 coincided with a period of very dry hot weather in 
spring and summer which reduced the populations on the sites with the 
lowest water tables (Table 20.1). The decrease in 1980 coincided with 
cold, wet weather conditions in 1979 and 1980. Of the sites in the east of 
the reserve, the two with the lower initial population densities (8 and 10) 
had caught up with the remainder. Throughout the whole period 
Earthworm populations in abandoned arable fields 243 
Sites on wesr of reserve Sires on easr of reserve 
100 
E 
D 
C 
E 
o 
* 10 
1975 1977 1979 1975 1977 
Year 
1979 
Fig. 20.2 Population densities (log n+ 1) of L. rubellus. 
T a b l e 20.1 Physica 
Site 
1 
2 
3 
4 
6 
7 
8 
10 
Highest ground 
water level 
(cm below 
surface) 
< 40/40-80 
> 80 
> 80 
> 80 
40-80/> 80 
40- 80/ > 80 
40 80, > 80 
40 80/ > 80 
and chemical proper t ies of t he sites. 
PH 
4.6 
4.8 
4 6 
4.6 
4.6 
4-9 
5 0 
4.8 
Organic 
matter 
( g k g - * ) 
33 
33 
36 
34 
32 
35 
25 
19 
Total 
N 
(gkg~ 
1.0 
0.8 
0.9 
0.8 
0.8 
0.9 
0.8 
0.6 
Total 
P 
' ) (gkg-
0.8 
0.9 
0.8 
0.9 
0.9 
0.9 
1.0 
0.9 
Total 
Fe 
' ) (gkg-1) 
l . l 
1.2 
1-4 
1-4 
2.1 
1-7 
2.1 
3 1 
K 
(mgkg-
5 
24 
5 
5 
7 
6 
6 
0.6 
Cu 
' ) (mgkg- ' ) 
4 2 
2.6 
2-4 
4 .0 
1.8 
2-3 
2-5 
4 1 
1975-80, the population densities in the adjacent fields under arable 
management remained low. A total of only 22 worms was found in 120 
samples. 
The proportion of juveniles in the population declined when total 
numbers fell (Fig. 20.3). L. rubellus has only a limited ability to retreat to 
deeper soil and under adverse weather conditions mortality was greatest 
amongst the smaller worms. 
244 Ear thworm Ecology 
Population density (No. m ) 
80 59 62 100 219 81 23 6 10 35 51 29 26 9 23 47 60 20 9 6 17 55 77 9 
6 7 8 
U Adults ^ ^ Sub-adults | | Juveniles 
Fig. 20.3 Age class distribution (%) of L. rubellus, 1975-80. 
20.4 S U C C E S S I O N 
During the period of observation, although the vegetation of the 
abandoned arable fields varied considerably from site to site, arable plants 
decreased and grasses, typically Agrostis stolonifera and A. tenuis, 
increased. This is part of a succession in which arable species are 
vioo 
E 80 
= 60 
= 20 
10 
o ï 
rU, 
\f 
I 
2 1 3 4 6 7 8 
[ _ J L rubellus [|j/4. caliginosa ^ 0 octaedra ^ L casAaneus 
10 
Fig. 20.4 Species composition of sites in supposed order of vegetation 
succession. 
Ear thworm populations in abandoned arable fields 245 
gradually replaced by species typical of dry sandy grasslands (Koelerio-
corynephoretd) or very poor grasslands tending to heath {Nardo-
calluneta). 
In the first two years of observations, the earthworm populations of all 
but two of the sites consisted exclusively of L. rubellus (Fig. 20.4). By the 
fourth year A. caliginosa had colonized all but one of the sites and between 
the third and sixth years Lumbricus castaneus was recorded in three sites 
and Dendrobaena octaedra in four. Though typically a coprophage, 
L. castaneus showed no relation between the year of colonization and the 
incidence of horse dung. Invasion by D. octaedra also showed no specific 
relationship with particular plant species but it is typically a species of 
heath and impoverished sites. The site with only L. rubellus was subject to 
high trampling pressure. 
20.5 C O N C L U S I O N S 
Observations have been made over a period of six years in a succession 
which can be expected to continue developing for several decades. 
Although the results are therefore preliminary, they nevertheless confirm 
the results of other studies on colonization. The four earthworm species 
so far recorded: L. rubellus, A. caliginosa, L. castaneus and D. octaedra 
have been reported as pioneer colonists, although not always in the same 
combination, in pulverized fuel ash (Satchell and Stone, 1977), municipal 
refuse (Brockmann et al., 1980), restored opencast coal mines (Dünger, 
1969) and pastures (Martin, 1977). These species seem to have little in 
common, - L. rubellus and L. castaneus are active surface migrants, 
A. caliginosa is not; D. octaedra tolerates sites with very acid organic 
horizons, A. caliginosa does not (Satchell, 1955); L. rubellus and 
L. castaneus have high reproductive rates, A. caliginosa does not (Evans 
and Guild, 1948). The success of these species as colonists is clearly not 
explainable in simple terms of mobility, fecundity or ecological category. 
Though convergent as pioneers their biology is individual to each species. 
20.6 A C K N O W L E D G E M E N T S 
I thank Mr J. Bodt and Mr D. van den Ham, for help with the earthworm 
sampling, Dr J. A. van Rhee who started this project and Dr J. E. Satchell 
for his valuable revision of the manuscript. 
20.7 R E F E R E N C E S 
Brockmann, W., Koehler, M. and Schriefer, T. (1980) Recultivation of refuse 
tips: soil ecological studies. In Soil Biology as Related to Land Use Practices 
246 Earthworm Ecology 
(ed. D. L. Dindal), Proc. Vllth Int. Soil Zool. Coll., EPA, Washington, D.C., 
pp. 161-168. 
Dunger, W. (1969) Fragen der naturlichen und experimentellen Besiedlung 
kulturfeindlicher Boden durch Lumbriciden. Pedobiologia, 9, 146-151. 
Evans, A. and Guild, W. J. McL. (1948) Studies on the relationships between 
earthworms and soil fertility. IV. On the life cycles of some British 
Lumbricidae. Ann. Appl. Biol., 35, 471-484. 
Martin, N. A. (1977) Guide to the lumbricid earthworms of New Zealand 
pastures. N. Z. J. Exp. Agric, 5, 301-309. 
Satchell, J. E. (1955) Some aspects of earthworm ecology. In Soil Zoology (ed. 
D. K. McE. Kevan), Butterworths, London, pp. 356-364. 
Satchell, J. E. and Stone, D. A. (1977) Colonization of pulverized fuel ash sites by 
earthworms. P. Cent. Pir. Biol. Exp., 9, 59 74. 


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Development of earthworm populations in abandoned arable fields under grazing management

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