[APWG] Ecosystem dynamics and alien species Re: Microstegium question [1/9]

Tue Sep 1 15:01:08 CDT 2009

Russ/APWG:

I hope you'll follow up with the results of the analysis. What follows is pure speculation/conjecture, but if it will serve as a stimulus toward a more solid course, maybe it will be worth considering. You have been forewarned! 

My first thought is that it may take additional lab work to identify "the cause." Sometimes natural phenomena, as you know, are complex. If an organism is found, or some chemical signature of one, that may or may not mean that "inoculation" with that organism will necessarily, in of itself, be effective as a "control" method. 

You might want to do some comparative field studies of areas where the stiltgrass is in various stages of decline, areas where it is "stable," and areas where it is advancing, and chart other characteristics of the sites, such as the species diversity, distribution, density, and age. It looks like the site is second-growth of significant age since the last disturbance, judging by the trees, the apparent diversity of companion herbs, and the downed timber. Judging by the colonization of some of that timber and the relatively "clean" nature of other pieces (which look like they might be split--intentionally, by lightning strike, or ?), there could be a history of multiple disturbances, some perhaps "major" and some relatively "minor." 

I have a gut feeling that this might be due to increasing diversity (shall we say "maturity?") of site soil characteristics (which can vary a lot from one small location to another, perhaps combined with simple factors such as the amount and intensity of solar radiation and ecosystem dynamics such as the buildup of vectors, populations of organisms, and increasingly favorable habitat conditions therefor. There may or may not be a single "silver bullet;" a number of big guns and little guns, and even lesser guns* may be "required" to achieve the die-off you have observed. 

A key player might be (mycorrhizal) fungi, nutrient sequestration/availability, which may be connected to other soil chemistry effects, which might be combined with biological ones. 

I look forward with interest to reports of your further work. 

WT

  ----- Original Message ----- 
  From: ForestRuss at aol.com 
  To: APWG at lists.plantconservation.org 
  Sent: Tuesday, September 01, 2009 6:48 AM
  Subject: [APWG] Microstegium question

  APWG:

  I am a forester in central WV and have been involved with fighting the spread of Japanese stiltgrass for most of the past decade.

  Everything I have read about stiltgrass indicates that there are no known diseases of  the plant that have an impact on its health or spread.

  A couple of years ago I started to notice that in some places the stiltgrass was dying.

  This year in some portions of WV there is a massive die off of stiltgrass with 100% of some populations dying.  My thought it that it could be a virus of some sort.

  I have taken a tremendous amount of photos of the changes in the stiltgrass plants and below are a few images.  When the plants die the thatch is different and the stiltgrass is decomposing much more rapidly than when they go their full life cycle.  There are many areas where there will be no seed produced this year.

  Samples of the grass were taken to WVU in Morgantown, WV last week to see what was killing the plants.

  Below are a couple of photos.

  Thank you for your thoughts or comments.

  Russ Richardson, Certified Forester
  Crummies Creek Tree Farm
  PO Box 207
  Arnoldsburg, WV 25234

  Spots on the leaves is the first sign that the plants are sick.

  It moves pretty quickly once lesions show up on the leaves.

  Most of the straw on the ground is stiltgrass that died already.

  The tan area in the center of the photo is dead and dying stiltgrass.

  The last plants in an area that was almost waist high a month ago.

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