[APWG] flammable biomass

[maryann whitman]

This is something I sent to Mike last night. I don't know if APWG will carry
this large e-mail.

Maryann


Maryann Whitman, Journal Editor
Wild Ones: Native Plants, Natural Landscapes
 
www.for-wild.org
 
Wild Ones: Native Plants, Natural Landscapes promotes environmentally sound
practices to encourage biodiversity through the preservation, restoration
and establishment of native plant communities. Wild Ones is a
not-for-profit, environmental, educational, and advocacy organization.



-----Original Message-----
From: maryann whitman [mailto:maryannwhitman at comcast.net] 
Sent: Sunday, September 28, 2008 10:17 PM
To: 'Michael Schenk'
Subject: RE: [APWG] flammable biomass

Mike this was an article that I wrote for the Wild Ones Journal in 2004. I
think it will answer some questions for you.

Maryann


Maryann Whitman, Journal Editor
Wild Ones: Native Plants, Natural Landscapes
 
www.for-wild.org
 
Wild Ones: Native Plants, Natural Landscapes promotes environmentally sound
practices to encourage biodiversity through the preservation, restoration
and establishment of native plant communities. Wild Ones is a
not-for-profit, environmental, educational, and advocacy organization.



It’s All One Piece: An example of the dynamics of extinction
By Maryann Whitman

The main character in our tale is the longleaf, or southern yellow pine
(Pinus palustris). It is indigenous to the high sandy hills of North
American Atlantic and Gulf coastal plains, south of Virginia through to
eastern Texas. 

For over a century, until the mid-twentieth century it enjoyed a worldwide
reputation. Its even grained, durable, straight stems providing 12” by 12”
by 80’, all-heartwood timbers for shipmasts and later for structural
timbers. Often building its own railroads, the logging industry marched
across the south, to tap the westernmost stands of longleaf pine in Texas
before 1900. By 1940, the original longleaf pine forests existed only in
memory, replaced by controlled plantations.
Another actor in our tale is the red-cockaded woodpecker, which nests in
cavities that it excavates in the trunks of these living pines. The rarity
of old-growth stands has led to the designation of the woodpecker as
endangered, and thus the primary driver behind efforts to preserve the
remaining old stands and to restore such stands to a frequent fire regime.


Ecology of longleaf pines 

Pinus palustris is adapted to frequent low-intensity fire. It has a deep
taproot and a dwarf form or ‘grass stage’ during early growth. The grass
stage is an adaptation unique to the longleaf pine. Ground-hugging tufts of
needles surround the apical bud, resembling stiff-bladed bunch grass. This
short-shoot habit of growth during the seedling years has been attributed to
competition by plants for moisture and nutrients, to an inherent seedling
trait under rigid genetic control, and to an auxin, or plant hormone,
produced in buds during early stages of development. Environment also seems
to influence the amount of time seedlings remain ‘in the grass’. It may be
three years or less where soil moisture is adequate and plant competition
negligible, to twenty-five years on dry, xeric sites with dense overtopping
crowns of scrub oaks and ground cover of wiregrass (Aristida beyrichiana). 

A rule of thumb among foresters is that the trees begin height growth when
the dwarfed stem has swelled to an inch in diameter at the root-collar, and
not before. When that ground-line size is attained, height growth exceeds
three or four feet a year. In a region where forest floors are swept by
fires nearly every winter, longleaf pine protects itself by clinging to the
ground during those early years when most vegetation is so vulnerable to
fire damage. Then, well rooted and with ample food reserves, it spurts
upward, not as a slender, thin-barked shoot, but as a thick stem surrounded
by bark and a dense continuous array of long needles. Thousands of seedlings
survive low-temperature fires during the first few years of height growth.
After the stems are ten to fifteen feet tall, the trees are able to survive
with very few adverse effects from all but the most severe fires.

Extremely intolerant of shade and competition, the trees that do survive
suppression by these factors gain dominance and rarely touch crowns. Their
lower limbs die and drop off, mainly because of the shade cast by the
foliage of their own upper crowns. Profuse production and shedding of
needles and ready shedding of lower limbs provide a rapid accumulation of
fine fuels, sufficient to support ground fires at frequencies as often as
three years. An extremely flammable heartwood and sapwood are shielded by a
relatively fire-resistant bark.


Another dynamic in this story is the role of Brownspot needle blight. Caused
by a fungus present in most soils, it infects and kills the needles near the
ground. Three successive defoliations are enough to kill seedlings.
Foresters learned that controlled fires destroy spores of the disease along
with infected foliage, freeing the new needle growth from major infection
for a couple of years. Two controlled burns, two years apart, are usually
sufficient to launch a generation of seedlings into the sapling stage of
rapid height growth.

The controlled burns need to be cool fires that run quickly with the wind.
The needles are rapidly consumed by fire to within a couple of inches of the
bud. So dense and long are the needles that they insulate the bud during the
few seconds it takes the fire to pass. Needles are expendable. From the bud,
promptly sprouts lush-appearing, vigorous foliage to manufacture
carbohydrates by photosynthesis.

With the reintroduction of fire, by the early 1990s both longleaf pines and
red-cockaded woodpeckers appeared to be making a comeback.


Enter Cogongrass into this Balanced Equation

Into our story enters the villain. Native to the Philippines, southeast
Asia, China and Japan, cogongrass (Imperata cylindrical) was introduced to
North America accidentally in the 1920s, as packing material, and on purpose
in the 1940s as forage and as an attractive horticultural specimen. It is a
perennial, rhizomatous grass that grows from 2 to 4 feet in height. Mature
leaf margins are finely toothed and embedded with silica crystals, making
only the very early immature growth palatable to grazing animals. 

Cogongrass can invade disturbed ecosystems, forming a dense mat of thatch
and leaves that make it nearly impossible for other plants to coexist. The
grass displaces a large variety of native plant species used by native
animals as forage, host plants and shelter. It spreads rapidly by rhizomes.
Established stands can produce over 3 tons of rhizomes per acre. Another
attribute that helps cogon to dominate is that the rhizomes exude
allelopathic substances that inhibit growth of other plants.

Infestations alter the normal fire regime of a fire-driven ecosystem like
that of a longleaf pine plantation. Researcher Carol Lippincott has
determined that cogon burns differently than do native species like
wiregrass, which it displaces in the ground layer. Fires fueled by cogon
occur more frequently, burn hotter, and higher above the ground (to 5 and 6
feet) than do fires fueled by native vegetation (18 inches). These hotter,
slower, higher fires affect the cool-fire-adapted apical buds of the
longleaf pine, both in the grass stage and during its first year or two of
height growth. These fires kill large numbers of seedlings, but suppressing
fire among the longleaf pines is not an option. 
Time will tell
 

Sadly, we have delineated the major actors and forces in an unhappy tale of
potential extinction of at least two genera. The tapestry of interdependent
lives is an intricate one. Once again the element of Time, truncated by
man’s heavy-handed intervention, may be the telling factor.

-----Original Message-----
From: apwg-bounces at lists.plantconservation.org
[mailto:apwg-bounces at lists.plantconservation.org] On Behalf Of Michael
Schenk
Sent: Sunday, September 28, 2008 12:04 AM
To: apwg at lists.plantconservation.org
Subject: Re: [APWG] flammable biomass

There's been a lot of attention paid to invasive-fueled wildfires out West
(and rightly so), but has there been documentation of the fire impact of
stilt grass on Eastern forests? I recently threw a mass of dew-soaked green
stilt grass on a small wood fire, and it burned like the 4th of July. I'm
worried about how much more intense a ground fire will be with stilt grass
present. 

On an associated note, is anyone harvesting stilt grass for fuel? 

Mike