The effect of ecosystem engineers invasion is context specific and depends of stage of invasion

With  melting of permafrost many changes of arctic soils can be expected.  Important changes are expected to be associated with invasion of  soil ecosystem  engineers such as earthworms and or other soil macrofauna. The effect of ecosystem engineers if context specific, not only in a way that environmental conditions such as soil texture, pH or litter quality may affect effect of engineers, but also in the way that ecosystem engineers change their environment which then alternate effect of engineers on the system. The latter effect made evaluation of engineer’s effect complex because it basically means that  when we do simple manipulation experiment when we manipulate presence of engineers we can get different response to that manipulation in different stages of invasion of better to say after system has been modified by engineers for some time. This is due to the fact that previous effect of engineers leaves some legacy of long-term effects and this legacy change immediate effects of engineers. Here we focus on earthworm invasion/colonization.  The aim of this contribution is to summarize our knowledge about  changes of earthworm  immediate effects on the soil along gradient of earthworm long term legacy in the system and formulate simple conceptual framework than may help to understood underlying mechanism of this phenomena, which may help in its implication to ongoing to future ecosystem invasions such as earthworm colonization of the arctic.