Browsing by Subject "Lumbricidae"

Earthworms act as ecosystem engineers. As such, they have a large impact on many ecosystems. However, little is known about how they will respond to climate change. Substantial quantities of carbon pass through soil's macro-decomposers of which earthworms are the largest group in terms of biomass. They are drivers of soil bioturbation and play a major role in soil's organic carbon input and nutrient availability. Through their actions they increase soil's microbial activity, as well as the primary production in ecosystems. Earthworms have a great impact on soil and atmospheric carbon levels. Earthworm activity leads to direct and indirect increases in the CO2 flux between soil and the atmosphere. Earthworms directly impact soil CO2 flux only a little, whereas the indirect impacts are more substantial and are caused by earthworm-driven increases in microbial activity. The aim of this thesis is to find out how two common earthworms species in Finland, Lumbricus terrestris L. and Aporrectodea caliginosa Sav., respond to environmental changes brought on by climate change. According to climate models, the average temperature and precipitation during growth season will increase in Northern Europe during the next 100 years. Laboratory experiments were performed to examine the interactive effects of changes in precipitation and temperature on these earthworm species from two different ecological groups. The earthworms were incubated in two different temperature and precipitation treatments and measurements were performed to monitor impacts on soil pH, C, and N content as well as CO2 flux. Earthworm survival, growth and leaf litter consumption were also monitored. The results indicate that the presence of another earthworm species has a larger impact on the survival of individuals than climate conditions have. It is important to find out how climate change will affect interspecies competition, the distribution of earthworm species, and the composition of earthworm communities which all have implications on soil CO2 flux through the earthworm community. The results indicate that temperature, precipitation, and the presence of another species have a positive correlation with soil CO2 flux. However, L. terrestris, mainly a detritivore, did not increase their consumption of leaf litter in higher temperature or precipitation conditions compared to ambient climate conditions. This result needs further investigation in longer-lasting laboratory experiments as well as in field conditions, as a possible positive feedback mechanism between earthworm activity and climate change might be revealed.