Friday, December 16, 2016

Invasive Control - Sprouts from Bird Droppings

I believe I have reached the maintenance stage in my efforts to control invasive shrubs at Blue Jay Barrens.  After eliminating all of the large, fruit producing specimens, I spent a couple of years dealing with masses of root sprouts surrounding the dead stumps.  Now I deal primarily with newly arrived two to three year specimens.  The Autumn Olive in the photo above shows what I typically find during my searches for invasive shrubby species.

Birds are the primary transport mechanism bringing seeds of invasive plant species onto the property.  Seeds passed through the gut of a bird arrive via bird droppings.  The bird’s digestive process softens the hard seed coat, making it a high likelihood that the seeds will germinate come the next growing season.  Seedlings arising from this type of process are usually found growing in a closely packed clump only a few inches across.

A typical clump consists of 8 – 12 individual plants, identifiable here by the light colored stumps that remained after the tops were removed.  The seeds are most often deposited in the fall.  By the time the seeds germinate in the spring, they have been separated slightly through the action of the soil fauna feeding on the non-living portion of the bird dropping, along with climatic factors such as rain, wind and frost-heave. 

I sometimes find first year seedlings, but they are hard to see because their height rarely exceeds a few inches.  It’s more usual to discover the two or three year old clumps.  A plant that reaches only six inches one year can easily grow to three feet by the following year. 

The seedlings within a clump are in fierce competition with each other.  Only those that make the most efficient use of the resources within their root zones will survive.  Within each clump are one or two stronger stems that overtop the others.  Stems on the outskirts of the pack frequently grow horizontally along the ground and form roots away from the group.  Here they can develop with less competition and increase their chances of survival.

The seeds in this group failed to disperse much beyond the limits of their original deposition.  Horizontal growth was the only way for many of the plants to access sunlight.

I don’t know how many thousands of seeds are brought into Blue Jay Barrens by birds each year.  It’s usually not difficult to find fresh seeds on the ground in areas frequently used by birds for feeding, roosting or loafing.  A good example is this pan of fresh water that I keep near my bird feeding station.

On the deck beside the pan is an assortment of seeds left behind by birds coming in to drink or bathe.  From late summer through mid-winter, new seeds are added daily to the collection.  When I empty the old water, done once or twice each day, there are always a few seeds in the pan.  Not all of these seeds come from invasive species.  The majority are Eastern Red Cedar, a native that happens to be a threat to open grassland and prairie.  There are enough invasive seeds though, to make alien shrub seedlings a permanent fixture here.  Fortunately, there are no more invasive shrubs at Blue Jay Barrens that are mature enough to produce fruit.  I am no longer contributing to the problem, I am just dealing with it.

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