|
Handling |
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A known amount of test substrate, dried at 40 to 60 °C, is placed
inside each MC (Fig. 4). The water and mineral content of the test substrate
is independently assessed by oven drying (105 °C) and ashing (600 °C)
a separate subsample. Commonly, 150 to 300 mg of the test substrate (depending
on litter type) is used to fill a MC. In our work to-date, we have used
leaves of beech, pine and spruce needles, rye straw and lucerne crop residues.
It must be noted that the commonly larger pieces of the test material have
to be fragmented, e.g. by shortening of needles or cutting a leaf into
smaller pieces which may accelerate the decomposition rate. This disadvantage
should be compensated by using the same material on all test plots. After
weighing the filled MC is closed with the second gauze disc and an end
ring, and inserted into a hole in the PVC-bar. When all MCs are in place,
the bar is wrapped in cling-film, to avoid losses of the test substrate
during transport.
|
Patterns of exposure |
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The MC bars can be placed on the soil surface or into the soil in different
ways. Fig. 8 shows three patterns of use on an agricultural site: 1) horizontal
insertion into the top soil, 2) vertical insertion to depths ranging up
to 25 cm (nearly down to the ploughing level) and 3) exposure on soil surface
(used for special tests). For common use in forest soils, we recommend
the use of long bars placed horizontally into the organic surface layers
(L, F) or alternatively short bars implanted vertically (Fig. 9).
The number of bars used depends upon the aim of the study and the experimental
design. From a statistical viewpoint, we recommend the use of a minimum
of 12 individual MCs for each sample estimate. The MCs can be regarded
as independent replicates, if they are inserted randomly within bars and
the bar exposed horizontally. But the position within a bar is important
if the bars are implanted vertically because the mass loss depends on soil
condition in the different strata. Some of our results during exposure
in winter and spring have shown that the temperature difference between
top and sub soil influences the decomposition within MCs significantly.
During the period of investigation a temperature inversion occurred in
the soil profile which was followed by an inversion of the decomposition
rates.
 |
Fig. 8: Patterns of exposure of
Minicontainer bars in agricultural
top soils |
 |
Fig. 9: Patterns of
exposure of the
Minicontainer bars
in a spruce forest
top soils |
|
Analysis of minicontainer data |
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The bars should be recovered carefully from the soil and any attached
larger soil particles be cleaned from the outside. Then they should be
covered with cling-film again and stored in a cold box for transportation.
In the laboratory, the MCs are pushed out from the bars using a PVC-rod
(Fig. 2). Some of them can be placed immediately into a modified ‘high
gradient’ soil fauna extractor using miniaturised extraction units. Especially
Acari and Collembola are the dominant microarthropod groups easily extracted
from the MC. Larink (pers. comm.) reported that a lot of Diptera larvae
has been found within MCs. Because the volume of a MC is only 1.5 ml, faunal
extraction can be completed within 8 to 10 days increasing the temperature
in steps of 5 °C to a final temperature of 50 to 60 °C. The extracted
MCs are then opened and their contents transferred to a small Petri-dish.
Any unextracted animals, larger mineral soil particles, and roots are picked
out by hand. Thereafter, the material is dried at 40 to 60 °C and weighed.
A subsample of MCs is ashed to determine mineral contamination, and a further
subsample is homogenised and analysed for C/N ratio.
If the investigation is focused on the dynamics of the decomposition
processes, experiments have to be designed as time series. To detect the
effect of leaching during the early phase of exposure, the sampling intervals
should not be longer than 14 days. When the main leaching effect decreases
(usually after 4 to 8 weeks), we propose sampling intervals of 4 weeks
or longer. Using the net mass values of the litter remaining within the
MCs, the decay constant k can be calculated by regression analysis using
e.g. an exponential decay function, e.g. mt = m0 · e- k ·
t (or ln mt = ln m0 - k · t) where: m0 =
test substrate mass at time t = 0 (100%), mt = corrected substrate
mass at time t (in days, weeks or months) and k = decay constant (rate
of decomposition).
The calculation can be performed for the total time of exposure (single
compartment model) or for separate intervals of time (sequential compartment
model). The latter is necessary when intensive leaching losses occur during
the first weeks of exposure. This depends largely on the age and quality
of the tested material. If non-aged litter material is used, leaching initial
losses are usually large, resulting in a bimodal pattern of mass loss.
In the case of aged litter, the decay process usually follows an unimodal
pattern.
|
Some results |
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Fig. 10 shows the results of a pilot study with two groups of MCs each
containing 15 MCs filled with three sorts of litter and randomly arranged
within bars. The bars were exposed horizontally for four weeks into the
upper horizon of a pine forest soil. Each column represents the value of
a single MC (mass loss or Cmic respectively). It is shown that the differences
between the litter subsamples are smaller than those between litter groups.
Especially in the case of linden leaves higher mass loss seems to correspond
with microbial biomass C. The differences between both mass loss and Cmic
of linden and the respective values of the other litter types are highly
significant (Mann Withney U-test, p < 0,01). It is known that the materials
used for this test are very different with respect to litter quality, e.g.
C/N ratio, content of sclerified tissues etc. The results indicate that
the method used is able to show effects even within few weeks.
 |
 |
| Fig. 10: Results of
a field study worked out by students during a soil ecological course. The
diagramm shows data of two sets of MCs. Exposure time: 4 weeks at the
same soil plot |
|
Conclusions |
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The Minicontainer-system is a modification of the litterbag technique,
used to study the process of litter decomposition both on the soil surface
and in soil. Up to now, the test has been used in forest and agricultural
habitats to measure the effects of soil management, e.g. soil liming, amelioration
of degraded soils and tillage practices. The modular concept of the system
readily facilitates inter-site comparisons. It is evident that the system
allows simultaneous but separate measurements of a number of biological
soil parameters in studies with a variety of objectives, e.g.:
-
Loss of the litter mass (rate of decomposition)
-
The influence of litter quality on decomposition rate
-
Measurement of microbial biomass during the decomposition process
-
Comparison of the effects of different soil biota (microorganisms, mesofauna
and smaller specimen of the macrofauna, e.g. Diptera larvae) on decomposition
using different mesh sizes of gauze discs
-
Assessment of interactions between soil fauna, soil microorganisms and
litter, e.g. steps of succession in the exposed litter
-
Assessment of abiotic factors affecting litter decomposition dynamics,
e.g. temperature, pH, etc.
-
Assessment of soil contamination, e.g. by heavy metals or chemicals.
Further advantages of the method are the small sample size which allows
a high number of replicate experimental units, the ability to insert test
substrates with minimal soil disturbance and facilitation of simultaneous
measurement of a broad range of soil parameters. On the other hand there
are some limitations which arise from the comparatively small size of the
MCs:
-
The decomposition rate may be slightly increased because the material has
to be fragmented before exposure
-
The maximum mesh size of about 2 mm of gauze discs limits the access of
the larger soil macrofauna.
If you are interested in minicontainers for your research or teaching
methods, feel free to contact
me.
|
Papers |
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EISENBEIS, G. (1993):
Zersetzung im Boden. - In: Ehrnsberger, R.: Bodenmesofauna
und Naturschutz Bedeutung und Auswirkungen von anthropogenen Maßnahmen.
- Inf.
Natursch. Landschaftspfl. 6: 53-76. Naturschutzverband Niedersachsen (NVN),
Verlag Günter Runge, Cloppenburg.
EISENBEIS, G. (1994): Die Biologische
Aktivität von Böden aus zoologischer Sicht. -
Braunschw. naturkdl. Schr. 4: 653-658.
EISENBEIS, G., DOGAN, H., HEIBER,
H., KERBER, T., LENZ, R. & F. PAULUS
(1995): Das Minicontainersystem - ein bodenökologisches Werkzeug für
Forschung
und Praxis. - Mitt. Dtsch. Bodenkundl. Ges. 76: 585-588.
EISENBEIS, G., LENZ, R. &
HEIBER, T. (1996): Vergleichende Dekompositions-
messungen mit dem Minicontainer-System auf Agrar- und Waldstandorten in
Rheinland-Pfalz. - Mitt. Dtsch. Bodenkundl. Ges. 81: 21-24.
LENZ, R. & G. EISENBEIS
(1996): Die Auswirkungen unterschiedlicher
Bodenbewirtschaftung im ökologischen Landbau auf Nematodenfauna und
Mikroflora. – Mitt. Dtsch. Bodenkundl. Ges. 125-128.
EISENBEIS, G., LENZ, R., DOGAN,
H. & G. SCHÜLER (1996): Zur biologischen
Aktivität von Nadelwaldböden: Messung der tierischen Fraßaktivität
mit dem
Köderstreifen-Test sowie die Bestimmung von Streuabbauraten mit dem
Minicontainer-Test. - Verh. Ges. Ökol. Dresden 26: 305-311.
EISENBEIS, G., WEBER, M., FRITSCH,
N. & R. LENZ (1996): Bodenfauna und
Waldkalkung. - In: Min. Umwelt und Forsten Rheinland-Pfalz (ed.): Waldschäden,
Boden- und Wasserversauerung durch Luftschadstoffe in Rheinland-Pfalz -
Ökosystemschäden und Gegenmaßnahmen. – S. 47-66.
LENZ, R. & G. EISENBEIS
(1996): Die Auswirkungen unterschiedlicher
Bodenbewirtschaftung im ökologischen Landbau auf Nematodenfauna und
Mikroflora. – Mitt. Dtsch. Bodenkundl. Ges. 81: 125-128.
LENZ, R. & G. EISENBEIS
(1997): An extraction method for nematodes adapted in
decomposition studies using the minicontainer-method. – Plant & Soil
198: 109-116.
EISENBEIS, G. & R. PAULUS
(1997): Bodenbiologische Untersuchungen auf forstlichen
Dauerbeobachtungsflächen in Rheinland-Pfalz mit dem Minicontainer-
und
Köderstreifen-Test. - Mitt. a.d. Forstlichen Versuchsanstalt Rh-Pf.
40/97: 1-25.
EISENBEIS, G. (1998a): Die Untersuchung
der biologischen Aktivität von Böden I. Der
Köderstreifen-Test. - Praxis der Naturwissenschaften Biologie 4/47: 15-21.
EISENBEIS, G. (1998b): Die Untersuchung
der biologischen Aktivität von Böden II. Der
Minicontainer - Test. - Praxis der Naturwissenschaften Biologie 4/47:
22-29.
EMMERLING, C. & G. EISENBEIS
(1998): Influence of modern soil restoration
techniques on litter decomposition in forest soils. - Applied Soil Ecology
9:
501-507.
LENZ, R. (1998): Der Einfluß
differenzierter Bodenbearbeitung auf die Aktivität von
Bodenfauna und Bodenmikroflora und auf die Populationsstruktur bodenlebender
Nematoden. – Dissertation (Thesis), Fachbereich Biologie, Mainz.
LENZ, R. & G. EISENBEIS (1998): The vertical distribution of decomposition
activity
and
litter-colonizing nematodes in soils under different tillage. – Pedobiologia
42:
193-204.
MEBES, K.-H. (1998):
Collembolengemeinschaften in Agrarökosystemen - Steuerung durch
Umweltfaktoren - Einfluss auf den Stoffumsatz.
- Dissertation, FAM-Bericht 33, Shaker
Verlag. Aachen.
EISENBEIS, G., LENZ, R. & T.
HEIBER (1999): Organic residue decomposition: The
Minicontainer-system - a multifunctional tool in decomposition studies.
- Environ.
Sci. & Pollut. Res. 6: 220-224.
EISENBEIS, G. & T. HEIBER (1999): Aspects of decomposition of rye straw
fragments within
minicontainers. – In: Tajovsky,
K. & Pizl, V. (eds.) Soil Zoology in Central Europe -
31-36, Proc. of the 5th Central
European Workshop on Soil Zoology, Ceské Budejovice.
GEISSEN, V. & G.W. BRUMMER
(1999): Decomposition rates and feeding activities of
soil fauna in deciduous forest soils in relation to soil chemical parameters
following
liming and fertilization. - Biology and Fertility of Soils. 29: 335-342.
HEIBER, T. & G. EISENBEIS (1999): Vergleich wendender und nichtwendender
Bodenbearbeitung im ökologischen Landbau: Messungen zum Strohabbau
mit
Minicontainern bei Vertikalexposition. - Mitt. Dtsch. Bodenkundl. Ges. 91:
621-624.
LENZ, R. (1999): Der Einfluss der Bodenbearbeitung auf die
biologische Aktivität des
Bodens und auf bodenlebende Nematoden. - Verlag Agrarökologie,
Bern, Hannover.
HÄTTENSCHWILER,
S., BÜHLER, S. & C. KÖRNER (1999): Quality,
decomposition and
isopod consumption of tree litter
produced under elevated CO2. - Oikos 85:
271-281.
PAULUS, R.; ROEMBKE, J.; RUF, A.; & L. BECK (1999): A
comparison of the
litterbag-, minicontainer- and bait-lamina-methods in an ecotoxicological
field
experiment with
Diflubenzuron and Btk. - Pedobiologia-. 43: 120-133.
Dittmer, S. & S. Schrader (2000): Longterm effects of soil
compaction and tillage on Collembola and
straw decomposition in arable soil.
- Pedobiologia 44: 527-538.
HEIBER, T. & G. EISENBEIS (submitted): Soil
tillage effects on the vertical distribution of
decomposition
activity and seasonal effects on litter-colonizing Collembola. -
STURM,
M., STURM, M. & G.EISENBEIS (submitted): Recovery of the biological activity
within a vine-
yard soil after reparcelling and soil
restoration: a three-year study using the Bait-lamina-method. -
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