Re: Eucalyptus Trees.

[Carefreeland@aol.com]

In a message dated 7/31/02 12:16:25 AM Eastern Daylight Time, graeme@powerlink.co.nz writes:

> Dan's comments in text 
> Dear Biomass Colleagues
> This forum is a little quiet of late and I wonder if its an opportune time
> to share some thoughts and hopefully receive some answers to questions I
> have since I returned from Australia last week.
>
> While normally my interest in biomass is limited to chopping it up and
> gasifying it, its also true that this work goes hand in hand with planting
> fuel wood plantations where they don'e exist, and managing existing fuel
> resources to ensure their sustainability.
>
> Eucalypts have always interested me having grown up on Queensland,
> Australia, and I have often recommended their use to establish new fuel wood
> plantations.  With over 2000 of this species to choose from, there would
> seem to be one suitable for alsmost every country and environmental
> situation.


> I am curious if this variety is a result of selective breeding, or are the majority of the these varieties result of natural evolution? 

> During this visit to Queensland. I revisited the area of my teen age years
> (l950s) and was quite shocked at the effect on the environment, that in part
> I helped to create.  The tree cover was thin with an absence of larger
> trees, and the golden sands of the creek filled with silt as were the deep
> billabongs, once fish filled, but now no more than a sunken depression in a
> dried up landscape.
>
> I worked with the loggers extracting all the scattered blue gums (eucalypts)
> while the railway sleeper cutters cut down the next largest trees the
> ironbarks (eucalyptus sideraphloia). Large eucalypts still remained but they
> were not considered a millable resource, and in the last 46 years they were
> ringbarked and left to die.
>
> The sclerophyll forests of Australia are quite ancient, and the mix of
> eucalypts, acacias and banksias have colonised a very difficult environment
> bringing a balance and stability to the soils.  You could say the forsts had
> evolved a sustainable environment.
>
> Q1: My first question is in relation to the soil, which any road cutting or
> creek bank will reveal multi layers.  Do eucalypts individually tap
> different soil layers for minerals and nutrients and in  turn share these
> via mixed forest litter which bush fires turn to potash?

> I am not knowledgeable of eucalyptus.  Most tree varieties adapt to the soil conditions that they grow in. Most varieties favor one type of soil above all, but are found growing in many other soil types. What determines the location and health of a tree, is the sum of all growing conditions relative to that tree's ability to adapt to them. This is in turn relative to the competition offered by other plant life. 
> It requires a dozen or more elements present in the soil to accommodate plant life.  A tree, being larger and deeper rooted, has more soil from which to extract those minerals from than would a smaller plant or shrub.  Any decay process, weather fire or natural slow breakdown will leave most of these minerals in the surface soil.  The primary difference with fire is the additional loss of carbon and nitrogen. These form the organic media which supports lower (and higher) forms of life, and retains moisture. 

> Q2: In the removal of larger trees excluding them from what was a healthy
> forest mix, would the remaining trees be less healthy or slower growing.  Or
> could it affect the ability of the top soils to release their nutrient?

> Both of these could be true to some extent.  The remaining trees would benefit from less competition for resources such as sunlight, water, and minerals.  The drawbacks of this scenario are more pronounced when simple water retention is the weakest link in the growth support system.  Each plant present stores water in some relationship to it's total biomass.  Less biomass, less water stored per surface area.
> Dry climates rely on recycling dew and fog as much as rainfall to replace plant moisture. Removal of the large trees surely removed much of the moisture source available in the canopy for recycling.  Day night temperature swings are regulated to some degree by the availability of moisture to condense and evaporate, releasing and absorbing heat.  These factors are widely ignored, possibly just not understood yet.  I have spent much time educating people about these considerations. 
> The lack of shading of the earth degrades soil rapidly in an arid environment. Microorganisms die off with higher soil temperatures and the soil oxidizes carbon and nitrogen from humus. The result is both soil sterilization and surface erosion. 
> Leaf litter, decaying branches and seeds, as well as animal wastes from animals consuming vegetation, all contribute to the health of the soil.  Less large trees means less of all of these. The highest forms of life on the food chain generally depend the most on the largest trees. 
> Degraded topsoil results in both degraded rootmass and less soil moisture retention.

> Q3: If we clear original sclerophyll forests and replace them with a
> singular eucalypt species, would the soil remain healthy and sustain mono
> forestry?

> That is dependent on your ability to mimic the natural balance present before tampered with by man.  Certainly doing just what you describe alone is a recipe for disaster without consideration of all of the factors involved.  It is almost impossible to create the balance created over time by nature.  Things like building retaining ponds and replacing some of the organic content of the soil with balanced vegetation programs can make it much less of a disaster. 
> My limited hands on experiance in this area, is with observing and managing regrowth of an ecosystem over a construction waste landfill. This is however, in a wetter environment and not on the scale you have there. The surrounding vegetation and animal life supports the regeneration tremendously.  This leads to a conclusion that leaving large sections of the land natural and untouched should contribute greatly to the rejuvination of the degraded areas beside them. 
 > The single worst thing about monostands are their lack of ability to adapt to single pest problems which become epidemic.  Another problem with this approach is the clearing cycle which leaves the whole ecosystem to start from scratch each time it is clear cut.  

> Whilst its true  that Queensland has a policy controlling vegetation
> management, and excellent mapping of all regional ground cover,
> deterioration of the environment is there to see.  The trouble is that it
> takes a long time for the problems to surface once the trees are removed and
> it becomes almost impossible to restore the balance.
>
> I have to say that I am uneasy about deteriorating environments being an
> accepted cost to economic development, or resulting from economic activity
> in unsustainable regaions.  To that end I would like to improve my
> understanding of what might be possible or indeed what might be alredy
> happening to restore some of these cleared areas of theAustralian landscape.
>
> All comments will be appreciated.
> Regards.
> Doug Williams.


> The best approach to managing deteriorated environments is to compare them to the natural environment and try to mimic what is missing in the chain.  It takes a balance of plants and animals to optimize any ecosystem. Some plants are adapted well toward repairing damage but not as productive in a balanced environment.   >Knowing each of the stages of repair and choosing the proper management technique is way beyond the scope of this letter. Choose people who live in the region and know the natural balances that exist there, as they will work best as managers, provided profit motive is considered. 
       Good luck, good topic, 
  
       Daniel Dimiduk 
       Carefree Landscape Maintenance Co. 
       Dayton, Ohio, USA