Mind Map to Nowhere

I have no recollection of putting this together - from a few months ago, but I may write an essay around it.  I am especially fond of the node "St Patrick max guler Munich Studio"

Rhamnus cathartica (buckthorn) in Ireland - the definitive sighting

A few posts back I had excitedly wondered if I had found common buckthorn in Muckross Abbey in Killarney. I was determined to find this shrub which is a relative rarity in Ireland but has become a dominant woody invasive plants in the US Midwest.  With the help of Helana Twomey in Killarney we worked out that the plant I found was not buckthorn and was spindle (Euonymus europeaus) which keys out quite close in Irish floras.  I am not inclined to easily give up and I proceeded with my search.

Working on a tip from Dr Declan Little of Woodlands of Ireland, I made my way up to Clonbur Woods on the Galway/Mayo border.  Despite being  festooned by a small plagues of flies we found buckthorn close to the lake (Lough Mask) and growing on the limestone. The population is reasonably large.  Though not dominant is certain is prevalent enough.  Unlike the situation in Chicago where this species can be a virtual monoculture, buckthorn in Ireland seems to be more generously inclined towards its neigbours.

SEKsy Restoration: A Design for a Restoration Experiment employing Soil Ecological Knowledge to reduce Re-invasion by European Buckthorn

This work was undertaken with Lauren Umek who is the project manager and with the assistance of Tom Murphy from DePaul and a crew of dozens.

This recent restoration experiment directly addresses the hypothesis that successful prevention of the re-invasion of species like European buckthorn, Rhamnus cathartica, will be promoted by reducing soil nitrogen (N) levels.  High N in soils may be a legacy of long-term invasion by buckthorn, and other invaders, which have high N levels in their leaf litter.  As a consequence of reducing N as we attempt to do in this experiment, and perhaps this is counter-intuitive, the success of native plant diversity may be increased since the native community does not then have to complete with an aggressive invasive species.

In this experiment we chose those strategies for manipulating N availability in the upper soil horizons that managers might be expected to adopt if our experiment demonstrates desirable outcomes. These management techniques included mulching with buckthorn woodchips or with commercial mulch, a two-year corn-harvesting regime, and mowing and removal of a cover crop. Both of these strategies are expected to  reduce N levels in the soil and therefore reduce reinvasion rates.

Graph-Post 1: Soil phosphorus after removal of invasive shrub (Rhamnus cathartica)

 

 

This graph shows the soil phosphorus levels during the first year after an invasive shrub, European or Common buckthorn (Rhamnus cathartica), was cut and removed from our experimental site (controls are uncut buckthorn).  Each bar represents 5 separate plots per treatment.

In this experiment, conducted in collaboration with Lauren Umek and other colleagues at DePaul university, we removed the invasive species and then implemented a variety of treatments:

Best Management Practice (BMP 1) is to cut and then seed with natives;  

BMP + cc, is cutting of invasive follower by planting of a cover-crop of grasses;  

Corn is removal followed by growing a rotation of corn; 

The commercial mulch treatment is incorporated into the soil and native seed is planted; 

A mulch is prepared out of the wood from Rhamnus and incorporated into soul for the final two treatments (with cover crop, or with native seed).

The idea that we are playing with here is that a manipulation of the soil - wood mulches are especially important in this regard - reduces that availability of key soil nutrients, nitrogen in particular, which in turn reduce the rates of reinvasion by invasive species, and create an environment favorable to species of conservation interest.  Mulches may reduce availability of some nutrients because the microbes that decompose the wood "mop up" any extra nutrients making them less available to plants.

The results of an analysis of soil nutrients (sampled with a probe buried for approximately a month in Spring of 2008) revealed that mulched treatments generally had more phosphorus available in the soil.  The uncut control plots had the least phosphorus.  Contrary to our expectation nitrogen is not altered by any of our treatments.

I'll show, in later graph-posts whether this corresponds to changes in the vegetation (spoiler - there are interesting patterns in the reinvasion of the plots after invasive species removal and treatment).