Data/hora: 22/06/2024 02:11:06

Biblioteca(s): 	Embrapa Florestas.	
Data corrente: 	23/09/2008	
Data da última atualização: 	23/09/2008	
Autoria: 	NUUTINEN, V.; BUTT, K. R.; KETOJA, E.	
Título: 	Earthworms in constant trouble ? Impacts of drought and frost in boreal arable clay.	
Ano de publicação: 	2008	
Fonte/Imprenta: 	In: INTERNATIONAL COLLOQUIUM ON SOIL ZOOLOGY, 15; INTERNATIONAL COLLOQUIUM ON APTERYGOTA, 12., 2008, Curitiba. Biodiversity, conservation and sustainabele management of soil animal: abstracts. Colombo: Embrapa Florestas. Editors: George Gardner Brown; Klaus Dieter Sautter; Renato Marques; Amarildo Pasini. 1 CD-ROM.	
Idioma: 	Inglês	
Conteúdo: 	The need to predict the consequences of climate change in terrestrial ecosystems underlines
the importance of understanding how variation in weather conditions influence soil communities.
In the prevailing climate of northern Scandinavia, winter frosts and summer droughts are key
factors limiting the activity and population growth of soil fauna. In arable systems of this region,
earthworms are a prominent component of soil macrofauna, so we used a simple earthworm
community to investigate the impacts of weather extremes on soil life. The study system was an
arable grass-cereal rotation on subsurface drained sandy clay in south-western Finland.
The population density of the deep burrowing earthworm Lumbricus terrestris L. was
determined in two consecutive autumns, after a moist summer and then a very dry summer.
Samples were collected in relation to subsurface drain positions in the field. After the moist
summer, population densities were twice as high and biomasses five times higher above subdrains
than between the sub-drains. After the dry summer, population densities were markedly
reduced in the field and between the sub-drains, earthworm density had dropped beyond
detection level. Above sub-drains, the burrows of L. terrestris were deeper than those found
between the drains and had direct contacts with the moist and aerated surroundings of these
tile drains. This may have assisted population persistence near the sub-drains during the drought.
To investigate the adaptation of earthworms to winter conditions in the same field, the
depth distribution of earthworms was investigated in one winter during the maximum depth of
frost (0.55 m). L. terrestris had retreated below the frost depth to the bottom of their burrows
(max. depth 1.0 m) where they remained seemingly active. Aporrectodea caliginosa Sav. were
found aestivating throughout the frost layer, juveniles higher in the profile than the adults. All
aestivating individuals recovered rapidly when taken into a higher temperature environment. A.
caliginosa were also found actively burrowing below the frost depth, with maximum detection
depth at approximately 1.0 m. Viable cocoons of both A. caliginosa and L. terrestris were obtained
from the frozen soil at the depth of 0 - 0.25 m. The findings support an earlier hypothesis, based
on indirect evidence, that in the local arable clays A. caliginosa escapes frost by burrowing
markedly deeper than during summer drought.
For the study region, climate scenarios predict increased likelihood of summer droughts
and milder and more rainy winters. In local arable clays L. terrestris provides valuable soil services
and based on our results more frequent and severe droughts could have negative effects on its
densities. Winter ecology observations of A. caliginosa and L. terrestris suggest good adaptation
for living in and below frozen soil. However, less severe winters, with more shallow frosts would
likely benefit their population growth compensating for possible negative effects of droughts.
Our results point to one potentially negative effect of milder winter conditions: shallower frost
depth would suggest smaller maximum depth of burrowing by A. caliginosa, an important provider
of subsoil macroporosity in the clay fields of the region.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Florestas (CNPF)	
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