Tuesday, January 24, 2012

Interspersed Denuded Zones (IDZs): their ecology and conservation significance

This morning I got a chance to kick around ideas about Interspersed Denuded Zones (IDZs) with the Wise Lab in University of Illinois Chicago.  You may not have heard the term IDZs before.  The fact is I coined the term along with Vassia Pavlogianis very recently for a piece in 3quarksdaily. com entitled “A Tiny DyingSuch As This”. 

I wager the following: right now you doubt their existence, a year from now you’ll acknowledge them and perhaps recognize an IDZ when you see it, in five years you will argue with those that dismiss their ecological significance, and in ten years time you’ll vaguely recall having coined the term!  You may even be attending the first international meeting on IDZs by 2022.

An IDZ is one of a number of patches of exposed soil in a habitat which more typically has a well developed and contiguous leaf litter layer.  An IDZ can occur naturally where, for a variety of reasons, leaf litter decomposed more rapidly than it is replaced through leaf fall.  Alternatively IDZ can develop in response to a variety of anthropogenic disturbances.  If a non-native species with highly decomposable leaf litter replaces species with more recalcitrant litter then an IDZ can develop.  Similarly modification of the decomposer community (e.g. introduction of non-native earthworms) can accelerate the breakdown of litter.  Other factors may contribute – nitrogen deposition, elevated temperature etc can result in the altered dynamics of soil organic matter.

The ecological significance of IDZs have not to my knowledge been investigated (that is, under any name) though Kristen Ross from UIC, a post-doc with Chicago Wilderness, tells me that there is now some interest in looking at biodiversity of invaded patches in Eastern deciduous forest where invasive species have radically altered the litter layer.  However, in cases where the litter completely disappears the consequences will be quite different.

In A Tiny Dying I was primarily interested in the conservation implications – my suspicion is that with the intermittent loss of litter the effective habitat size for litter dwellers disappears and the populations crash.  As a result there may be a lot of local extinction as a result.  If I am correct this may be one of the most significant conservation crises of our times.  This is because there a huge proportion of the diversity of organisms of most terrestrial systems living in the litter layer. 

I appreciated getting great input on this idea from all my colleagues at David Wise’s lab at UIC this morning. Basil Iannone, Cristian Martínez, Dan Milz (especially for the hover-board suggestion!), Kristen Ross, Matthew McCary, Monica Farfan, Robin Mores, and Susan Kirt Alterio.

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