Tom's Blog

Saturday, August 4, 2012

Are drought-killed plants really dead?

Eupatorium purpureum patch showing serious effects of this summer's drought.
As I have noted in previous posts, the plants in many areas at Pleasant Valley Conservancy have remained surprisingly robust during this year's extended drought. The principal "at-risk" area is the south-facing slope, where little bluestem has been greatly suppressed (although rarely killed yet), and many of the forbs are markedly stunted.The savanna areas are in fair shape, although even here patches are being killed or greatly suppressed.

Most populations of woodland Joe Pye weed (Eupatorium purpureum), a common savanna species, still seem OK, but in several areas the plants are crisp and brown. It is not obvious why these particular plant populations appear dead, whereas others remain healthy. Perhaps it reflects a difference in groundwater availability.

I was interested to determine whether these dried up plants were really dead, so I dug up a few and looked at their bases. The photo here shows what I found. Despite the fact that the stem and all the leaves of this plant are brown and crisp, a new shoot is arising from the base. The growth of this shoot was probably released when the apical dominance of the stem was abolished. The roots of this plant also look dead, although new root primordia probably are present in the area where the new shoot is growing.

I'm not sure whether shoots such as these, arising from "dead" plants, will continue to grow, breaking through the soil surface. Their fate may depend on whether rain will replenish the supply of soil moisture.

At least we can say that at this stage, these dead-looking plants still have life in them.


Blogger Good Oak said...

I would like inquire about a combination of your past two threads: is the drought-killed bluegrass really dead? I read somewhere recently that not only does the soil have to dry out nearly completely, but the soil, at least the root zone for the grass, needs to reach a certain temperature to kill the roots. Doesn't seem like this will happen in most prairies, but perhaps on your south facing slope.

August 13, 2012 at 10:29 AM  

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