[APWG] A couple of thoughts on disturbance and ecosystems

[Steve Young]

I've been reading the recent ecosystem thread with interest. A couple of
thoughts about the disturbance thing. Some forms of disturbance can be
somewhat subtle. For example, how are non-native earthworms fostering the
spread of certain non-native plants? What about changes in soil chemistry
and microbial life associated with macro invasives?

Excessive nitrogen input is a "disturbance" that alas is now universal due
to pollution inputs into the atmosphere, although it is geospatially
variable, e.g. especially high in the northeast United States. How does
this form of disturbance affect invasive behavior?

Animals cause disturbance. We humans move organisms around, including
unwittingly even now due to poor equipment sanitation practices for boots,
equipment, etc. Proliferating deer appear to be hastening the spread of
Japanese stiltgrass, along with their mechanized brethren, ATVs, etc.

But then there is the absence of traditional forms of disturbance as a
disturbance. What about changes in fire regimes? How about the loss of the
Pleistocene megafauna? Are some "undisturbed" ecosystems more vulnerable
because they no longer experience the disturbance patterns that were the
norm for thousands of years during their evolution? I ponder orchids as an
example, where the "absence" of disturbance seems to be a factor in their
decline in some cases.

It's all complicated stuff and all these factors likely are interacting. I
still say it's better to do the adaptive management thing and try something
and learn from it and come up with better approaches rather than give up or
just do armchair speculation. Cheers,

Steve Young
Invasive destruction volunteer
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