Agriculture Reference
In-Depth Information
the connectivity of burrow volume with the pore space of the matrix through the soil will govern
the extent of influence of the burrows. These two types of interactions have been described as axial
and radial effects in the case of gaseous diffusion (Arah and Ball 1994).
E
B
I
N
S
ARTHWORM
EHAVIOR
S
OT
TABLE
Earthworm species may change their behavior greatly when they are transferred from one soil
environment to another, despite apparently similar environmental conditions. It seems that there
are no specific behavior patterns at the level of species or even at the level of ÑecologicalÒ groups,
as defined by Lee (1959, 1985), Bouch (1977), and Lavelle (1983).
a
strictly endogeic species that makes short, disconnected burrows in soils in the Northern Hemi-
sphere, makes long vertical burrows in the temperate soils of the Southern Hemisphere, a burrow
shape that was reported by other authors to characterize anecic earthworm species. Similar obser-
vations can be made about
Aporrectodea caliginosa,
which has burrow patterns that are very different
in prealpine pastures in Switzerland and in forested hills north of Adelaide in South Australia
(personal observations).
Octolasium cyaneum,
which is considered a species with a strong potential
for population development in orchard soils (Daniel 1992), was observed to be unable to spread
in similar soil types and cultivation conditions (brown soil, orchards in organic farming system) in
New Zealand (Springett, personal communication and personal observations, 1991).
Interestingly, preliminary results about the burrow patterns of earthworm species introduced
into homogenized soil plots set in field conditions seem to demonstrate that
Lumbricus terrestris,
Allolobophora longa
and
have the expected burrow patterns, that is, patterns similar to the burrow patterns
they develop in their native environments (Springett, personal communication, 1991).
Although the apparent similarity of the soil conditions might be mainly caused by a lack of
suitable parameters to describe functional differences, such large variations in behavior indicate
the ecological plasticity of the species that can be used to respond to local soil conditions. Moreover,
the best examples of such a behavioral plasticity are observed among these northern European
lumbricid earthworm species introduced into temperate America or the temperate Southern Hemi-
sphere. Introduced species have to face soil conditions that result from interactions between natural
local soil evolution and introduced soil management practices. Such interactions could develop a
soil organization that might be regarded as deeply different from the soil conditions of places where
A. caliginosa
the introduced species originated (see
Chapters 5
and
13
, this volume).
It should be noted that, almost without exception, northern European earthworm species perform
well when introduced at the same time as new agricultural management practices are adopted,
despite variations in soil types and climates. The question is whether northern European earthworm
species, which resist or could adapt to northern European soil management, are at the same time
those species with the best aptitude to colonize new areas.
Simple experiments could confirm the ecological significance of the behavioral plasticity of
earthworms, for example, the intentional introduction of Southern Hemisphere earthworm species
into northern European areas. For instance, what would be the population success of
Microscolex
dubius,
which is well established in the temperate area of Australia, if it were introduced into
reclaimed polders in the Netherlands?
INTERACTIONS BETWEEN EARTHWORM BURROWS AND
SOIL PROPERTIES
I
E
B
O
S
P
NTERACTIONS
OF
ARTHWORM
URROWS
WITH
THER
OIL
ORES
A large variety of structures develop at the interface of the soil matrix and earthworm burrows.
Essentially, walls that are lined, cracked walls in empty burrows, and burrows filled partially or
completely with casts can be observed. Graff (1970) described the lining of earthworm burrow
