Sunday, 14 December 2014

Pollen Count on the Marshes

Katy,

Some thoughts about core samples and pollen analysis at Walthamstow Marsh.

There was a paleoenvironmental core sampling carried out by a Masters degree student along a transect of the South Marsh.  I can’t remember the date off-hand but I do have a copy of the draft thesis somewhere in the archives.  The transect was roughly along the line of the S. Marsh boardwalk.  This was sampling the Holocene deposits down to the surface of the floodplain gravels - so covering roughly the past 10,000 years.

If your aim is to determine what flora etc existed through the Holocene on the Marsh, it needs to be borne in mind that most of these deposits consist of silts and clays deposited by overbank flooding of the Lea.  Therefore much of the pollen etc will be derivative, having been swept down the valley from the higher reaches.

For more reliable data on what was local to Walthamstow Marsh you need to sample peaty deposits since these will contain identifiable in situ plant remains as well as pollens.  Unfortunately there are no extensive peat deposits at WM.  When we did our auger survey (1985)  to map the configuration of the buried gravel surface, we only occasionally found peat in small thin lenses and sometimes on the edge of the buried gravel channels and our coverage of the Marsh was comprehensive (around 500 boreholes – 2” diameter).  The purpose of the survey wasn’t to do analysis but we did log obvious changes in the sediments and so did build up an accurate 3D picture of the deposits..

I think that the Masters student also found a similar situation with the most valuable plant material coming from a small zone of peaty material on his one transect.  I think he may also have had some carbon dating of some material.  I must try to find his draft thesis.

So bear in mind that WM is not a FEN i.e based on peat deposits, but a MARSH i.e based on mineral deposits, even though Brian Wurzell once described the plant communities as being similar to those in a fen.

All the best,

John


> Date: Tue, 18 Nov 2014 12:39:46 +0000
> From: katyandrews2012@yahoo.co.uk


> I like Joan's idea (see thread and hyperlink) - but I rather suspect that it has already been done, either here on Walthasmtow Marshes or in similar locations.

> I know the valley has its own little microclimate (it can be pouring with rain in Clapton and Walthamstow yet sunny enough to play cricket at Marsh Lane Fields!, it can be dense fog near the reservoirs in west Walthamstow but bright and clear in Tottenham), but I doubt it is sufficiently different from the surrounding area to warrant such an undertaking if any similar local studies have already been done. I am copying this to Mike Punchard (Wildlife and Environment Officer at LBWF), Anne Woollett, Annie Chipchase, and Neil Houghton (Chair of the Walthamstow Historical Society), who might know.

> I am not sure it would be of very wide interest to know what specific flora was growing on a heavily-grazed water-meadow in Walthamstow in the past, sufficient to warrant the expenditure - both on the physical obtaining of the samples and their detailed expert analysis. However, I would willingly support any bid to have this project funded; after all, it is up to the HLF what they fund - we can only ask!

> Finding an area of marsh to do it in might be a bit difficult, as so much has been churned up during the 20th century, but it should be possible to find places where a deep core sample could be extracted. John Nash might be able to advise, as he has studied the underlying gravel beds in detail.
> I would be particularly fascinated to know if there was a change in mangement around the time of the Saxon settlement, for instance!

> I'm not familiar with the study quoted, and will try to follow the hyperlink later, but perhaps some suitable academic partners (Oxford or Bristol university?) could be suggested, and relevant researchers and postgrads approached with a view to assessing feasibility.
> Could Joan and Claire perhaps have a go at that, please?

> Good luck!
> Katy.
> --------------------------------------------

> To: claireweiss@hotmail.com

> Dear
> Claire

> There isn't much in the way of buildings on the marshes.  How about asking for money to explore pollen records on Walthamstow Marsh - like what Oxford University is doing on Marley Fen:

http://www.oxfordtoday.ox.ac.uk/culture/videos-podcasts-galleries/laboratory-leaves-3

> The pollen records in the layers will give snapshots of what was happening in the environment at different times going back the the last Ice Age.

> Kindest regards
> Joan


> Facebook
> Claire Weiss posted in Save Lea Marsh
> Claire Weiss 10:52pm Nov 10

> I received this from Alison Griffin: "Waltham Forest is a priority area at the moment, because it has received a relatively low share of funds. HLF are particularly interested now in getting more enquiries and applications from community groups in Waltham Forest, including groups who might like to do a funded project around the social or natural heritage of the marshes. Being a priority area at present sounds like you get some additional weighting for any application (likely to last for around the next 9 months); you can also get pre-application support - including with finding a suitable project to apply for - from Gillian. She’s very interested to talk to groups who might bring projects to the table and I thought of you. Please feel free to share with the marshes campaigns groups and get in touch with her if you would like to find out more." 

> Anyone interested perhaps get in touch with Alison for contact details of Gillian from Heritage Lottery Fund. 

> I am also sharing this with Don't Be Harsh page and with the Save Lea Marsh email group.

> Posted by: Claire Weiss [snip]
__._,_.___

Posted by: Katy Andrews <katyandrews2012@yahoo.co.uk>

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