Monday, 13 October 2014

Counting Glossodia major

On our property the commonest orchid is Glossodia major, the Waxlip.
It is widespread over about 2/3 of the property with a very concentrated colony in a patch of Kunzea ericoides (Burgan).  This year I decided to monitor the colony primarily to assess the patterns of appearance of the flowers.

The colony chosen is at about 800m AMSL at the top of an East-facing slope.  The site is approximately 2.5m (EW) x 11m (NS)  or 27.5 sq m in extent.  Most of the area in the site is covered with Burgan although to give a simple shape (plus to include a small buffer zone) some grassier area (mainly Joycea pallida tussocks) is included on the Eastern side.  A few marsupial (I suspect mainly Wombat, but Eastern Grey Kangaroo and Swamp Wallaby are also present in the vicinity) tracks weave more or less randomly through the patch. allowing vision to all parts of the site.

I had wondered about trying to sample the area rather than counting every flower but:

  1. I didn't really know enough about the characteristics of the site to ensure I had a representative sample;
  2. the nature of Burgan meant it would be rather difficult to mark the boundaries of sampling areas; and
  3. it wasn't too difficult to do a full count.

WRT to point 3 the main problem was ensuring that I didn't duplicate some counts by seeing flowers from two tracks.  So perhaps next year, having reduced issue 1 by this study, I might have a furteher thought about sampling - now essentially reduced to overcoming issue 2!

I found the first flowers in the site on 21 September, and by 12 October the peak flowering was clearly over so I have stopped recording.

This shows a typical view of part of the colony at the peak flowering in that part of the site:
So what is the story?  The simplest measure from this 'study' is that the maximum number of flowers visible at one timewas 219 on 6 October.  However by that time many of the earliest flowers will have 'gone over' and thus not be countable.  Taking 7 days as an approximate 'life' of a flower and perpetrating some very rough demographics (better than a blind guess, but not by much) I come up with an estimate of the number of plants in the area as being 312 equivalent to about 11 plants per square metre across the site (but this would vary between 0 and 50 in subareas within the site - see below).

This chart shows the number of flowers counted by day, together with a 4th order polynomial fitted - rather well -  to the data by EXCEL.
Another set of "big picture" observations relate to the location of the flowers within the site. That is illustrated in the next schematic graphic and (hopefully) explained in the following text.
The orange spots show the grassier area.  In simple terms the distribution of flowers across the site is shown by the two ovals.  The more significant points that I have got from this study are:

  1. Very few flowers were on the western side of the plot (so perhaps morning sun is important);
  2. The earliest flowering was concentrated in the SE corner of the plot;
  3. After a period of about a week when flowers were all along the Eastern edge, the focus became concentrated in the NE corner.

I shall ponder this a little more and perhaps cobble together an article for the ANPS journal comparing the experience this season with this species and my earlier investigation of Cyanicula caerulea.  (Of course, the flowering of Diuris sp.has not yet commenced out here!)


4 comments:

Denis Wilson said...

Great collection of Glossodia major. Martin.
Speaking personally, I have trouble with charts which show north as anywhere other than the top of the page. I know it probably works best for type setting to show it horizontally, but with the S/E corner in bottom left, I find that confusing to my brain.
Regards ... Denis

Flabmeister said...

Denis

I think this may be one of those things that some psychologists reckon is good for stimulating some part of one's anatomy (but possibly I am confusing them with doctors who use headlamps).

However I have now rotated the image and, proving my total committing to user feedback have also rotated the labels on the ovals!

Martin

Denis Wilson said...

I am deeply touched, Martin.
Only problem is what direction is "Z"? :)

Denis

Flabmeister said...

Denis

I will use a polite (apparently) word and say "Oh copulate it".

There are two possible answers to the question in your second comment:
1) for Seth Efrican readers, 'Z' would clearly be an abbreviation of "Zuid" which unfortunately means South and is thus 180 degrees wrong.
2) for the rest of you it means Znorth.

Another fix has been applied (and I am not rearranging the label for the fence line!

Martin