Tree induced drought?

Discussion in 'Planting, growing, nurturing Plants' started by Peter Warne, May 3, 2005.

  1. Peter Warne

    Peter Warne Junior Member

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    We live on 14 acres of regenerating land with cattle pasture on three sides. The fourth side is a 100-acre eucalyptus plantation, which comes to within 20 m of the boundary. The eucalypts have been there for about 5 years and are now about 8 - 10 m high. We have a dam about 20 m on our side of that boundary, fed partly by springs and partly by a seasonally wet gully. The level of the dam is lower than it's ever been since we have owned the property, and despite the (light) rain we have had it seems to be going still lower. The seasons are no longer reliable in terms of what is normal rainfall etc, but last summer in these parts was wetter than the preceding ones. According to our cattle farming neighbour, the two dams on the property where the eucalypts are growing are almost empty. The owner of the land, another cattle farmer, was grazing a few cattle on and around the trees, but he has had to stop because of the lack of water.

    Has anyone experienced this or heard of it before? It raises all sorts of questions: first, is it really the fault of the trees? If it is, will regenerated rainforest have the same effect? (We are planning regeneration for that whole side of our land). Is it just another example of the negative effects of monoculture?

    Puzzled
    Peter Warne
     
  2. gardenlen

    gardenlen Group for banned users

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    g'day peter,

    probably won't get anything scientific as they are there to support the government and vested interest.

    but for me it is the continued removal of forest and trees from our environment causing the lack of rain, and also the drop in the aquafa, no trees no water can get underground and the other result salt degraded land.

    i don't believe in mono-culturing it is only a temporary forest without any bio-diversity, so it is never going to become habitat it is their for the money much as the pine forests are and much habitat and bio-diversity was removed to create them. and quiet often they aren't indemic species they are manipulated fast growing species.

    i reckon it's about time everyone got out and about with eyes wide open and see waht is happening. if we rely on science we will once again be led astray just like with those damn cane toads.the reason we get frost here is almost no trees between us and the great dividing range. well no pristine forests anyway, just regrowth in small holdings.

    also saw a reuters news story not long ago that some aussie scientists are actually saying it is the removal of trees causing the lack of rain fall and the degradation of the top soil there under is causing what they term as climate change.

    to me mate from where istand and see waht is happening it's that simple. there have benn 2 major impacts on the australian environment european settlement with their inefficient house designs and european agriculture which is slash and burn degrade sell off to would be hopefulls, then move on and do it all over a gain.

    there is much more in this issue but that'll do for now.

    len :x
     
  3. funkyfungus

    funkyfungus Junior Member

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    Its quite likely it is teh Eucalypts doing this

    They have been planted in many places around the world to drain marshy areas as they can pump out large volumes of water

    They transformed the lives of ethiopians near addis ababa by giving timer, fuel and shelter where derorestation had left none

    but one of the negatives is the water table has dropped significantly - meaning wells must be deeper

    Eucalyptus are very useful but therir placenet needs to be well considered
    many speciues do naturally occur as virtual monoculture stands (see mountain ash for example) and this is their nature - species that do thius are godsends to broadscale agriculture as speies that can exist in lhigh density are usually disease resitsant and can be cash cropped.

    In this cae id say there are many problems - bad palcemnet, lack of consideration for nighbours hydrology etc etc
    I dont hink theres alot u can do though except adapt
    the drier soils can be useful for other things in a wteer climate

    re rainforests
    A rainforest can help hold mositure better by forming closed canpoies with mulch layers. but their productivity can be much lower and they need better soils
    The best rainforests in your situation would be dry ones
    they hav ethe benefit of holding more moisture but tolerate considerable drought, they have mnay useful species and do suppress fire to a greater degree than comparable vegetation
    They hold high endemic species diversity and are probably the most dynamic and evolutionary important rainforest in australia as this margin in flux is where the rainforest species are actively adapting to the drylands

    species like Hoop pine, bunya nut, kurrajongs and red cedar are ecomnomic species from drier rainforests.
    there are many more
    and overseas species also come from drier rainforest areas like the jakfruit or mangos
     
  4. Cly

    Cly Junior Member

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    I agree, it's the eucalypts, they suck up water like there is no tomorrow.
     
  5. gardenlen

    gardenlen Group for banned users

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    boy doesn't matter where you hang out you get the misinformation about the we hate eucalypts sector.

    this is permaculture are we not supposed to imrove, repair maintane and live sustainably within our natural habitat? is not habitat part of permaculture?

    around here my lushest grasses & systems are under eucalypt trees, strange hey. our best wind breaks are eucalypt trees another oddity. the irrigators in the murray/murrumbidgee basin already know that if they hadn't removed the trees mostly eucalypts from the high ground a slope they wouldn't have the salt problem they now have.

    eucalypts trap heavy dew and fog some of this moisture is taken by the leaves the rest is condensed and drip off to water the grass below and to create the environment for mulching to take place.

    eucalypts send their roots down a long way that is where the draw their moisture from so far down it has no effect on surface moisture, they keep the salt water table down, they allow for water from rain to travel down into the aquafa and maintane a healthy aquafa.

    lets get it righ permaculturists. yes there is no benefit at all for the habitat or environment from agri-forestry the only benefit is the environment of someones bank account.

    if we remove eucalypts from the habitat because we say this or that about them then where is the bio-diversity?

    i have water holes that ever dry a dam that never drops below a certain level. if dams aren't holding water then there is another problem and that could be location, the lack of effective catchment or simply badly built by someone who realy only thinks a dam is created when you make a hole in the ground, more to it than that folks.

    there are enough disenters out their ready to demolish bio-diversity let us not support that surely?

    len :(
     
  6. Peter Warne

    Peter Warne Junior Member

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    Hi Len,
    I can't agree with some of the things you say in your last. We are not talking about removing eucalypts from their habitat, this is a wet sub-tropical rainforest zone, with a sprinkling of eucalypts which are fine. Next door we have 100 acres of planted eucalypts, so they are the habitat invaders. Admittedly they were planted into old cattle pasture, so they didn't go in AT THE EXPENSE OF native habitat, but it's interesting to compare our block, also recovered from cattle pasture about 14 years ago. We are seeing the local rainforest slowly but steadily reclaim this land, mainly via seed transported by birds from the Nightcap Nat Park, less than 1 km from us on 2 and a 1/2 sides. We are encouraging this process by attacking the weeds which would otherwise take over completely, mainly lantana and camphor laurels. I have also counted over 50 local birds on our block, whereas the times I've been into the eucalyptus plantation next door I've seen hardly any birds at all.

    You say that it can't be the eucalypts causing the dropping of the level of the dam. Let me give you a couple of additional facts:

    1. There was a permanent boggy wet patch in the 20 m margin which runs between the plantation and our common boundary - too boggy to drive a tractor through. This was located just a little further up the slope from our dam. Now that patch has dried up completely - walking through it you won't even get your feet wet. The dam used to always have water seeping in through the clay on the same side as this wet patch in their property. It seems pretty clear to me that the springs that fed their wet patch also provided a lot of (most? all?) the water that seeped underground into our dam.

    2. On the other side of our block, about 150 m away, is another dam, fed by a similar boggy patch that you can't walk through without sinking up to your knees in slop, which is holding its level fine. And it held its level all the way through the dry years which may or may not have just ended.

    3. As for a badly built dam, well for years it always held a reasonable level up until very recently; it's just since last summer that it's gone right down.

    So this is not a hate-the-eucalypts session - I like eucs in their place, including a good number of them already on our block. But I remain highly suspicious of the effects of the 100 acre plantation next door.

    Cheers

    Peter Warne
     
  7. gardenlen

    gardenlen Group for banned users

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    i think i agreed with you in the first instance peter,

    that was that mono culturing be it eucalypts of pine trees is out of place. the agro-forestry has in fact replaced habitat the habitat that was there before it was clear felled for pasture us.

    adn yes non indemic species are probably the ones that are going to cause the probelm. but i was basically respondin to cly's post which appeared as a blanket blame for eucalypts.

    and also not sure about down nimbin way but up around here people are finding out just how fragile their systems are as the drought once again takes hold.

    sorry if you thought i was having a shot at you i had already answered your first post as i saw it. so there could be other factors related to the fall in water holdings. but right up front the agro-forestry will have all sorts of support gov' and other so they won't be taking any of the blame.

    len
     
  8. Cly

    Cly Junior Member

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    Blanket blame? I was adding my two cents and certainly not suggesting any drastic measures, I don't see why this has caused such a weird and frankly disturbing response. I have no problems with eucalypts, if they're there they're there and that's their right and their business, they're pretty, they're part of the biodiversity and the ones out the back where I am now have four koalas that visit often and one is on the historical register in Lawnton as it's bloody HUGE so huge infact it's scary, I've had dealings with them sucking water like a bat out of hell on a few farms and two properties but I certainly wouldn't dream of ripping them down. There could very well be many other factors and I'm sure there are though my dealings with them led me to add my five cents on the subject as the eucalypts haven't been kind to me water wise in any situation.

    The question has been raised a number of times in landcare and reforrestation groups and is currently the hot topic again as to whether the amount that are replanted should be diversified with other native trees as their water hogging is causing trouble here and there but then you have to take into account that the wrong species are being planted in the wrong area in some cases which is most certainly what the darn problem is. I see their point, I see your point, and I'm in the middle of the two. I believe if we can't work around any problem we have on the land that occurs naturally or with our help (native regeneration) without knocking it down is a sad thing indeed, henced I never knocked any down I just learned to live around it.

    As for the original topic, we used a technique we saw in Grass Roots I think (could have been Mother Earth) on a farm just west of Bowen in Nth Qld to stop a good deal of natural evaporation by using PET bottles painted white on the inside (weighted a little so they wouldn't blow away) that we crammed onto the surface of the dam - covering it entirely and it worked very well. You could add this to whatever solution you decide to go with, just gives you a bit more water security, it's also very cheap to do and is a great way to reuse. This technique has probably been revised and made more efficient by now (this was about 6 years ago).
    My great uncle also used this technique on his turf farm in Thuringowa a little after the Bowen project was complete which was met with great success.
     
  9. SueinWA

    SueinWA Junior Member

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    Mussolini had trees planted to dry out the Pontine marshes in Italy. It worked. I've never heard what kind of trees they were.

    And I read (Mollison, I think) that trees can suck up something like 4,000 gallons of water a day. In the U.S., we have an invasive small tree called the Tamarisk (or Saltcedar) that has taken over a million acres of wetland.

    Our National Park Service: "Tamarisk can usually out-compete native plants for water. A single, large tamarisk can transpire up to 300 gallons of water per day. In many areas where watercourses are small or intermittent and tamarisk has taken hold, it can severely limit the available water, or even dry up a water source."

    It would be nice to know specifically what other trees can do this. I'm sure that most trees do it to some extent. If you labor building swales to keep the groundwater available, it would be counterproductive to plant similar trees nearby. If you WANT some trees to transpire 4,000 or 5,000 gallons of water into the atmosphere, fine. But if you're trying to keep it in the water table....

    One of my main problems with permaculture is trying to find lists of plants that serve certain purposes. It's like trying to invent the wheel all over again, for everyone.

    Sue
     
  10. funkyfungus

    funkyfungus Junior Member

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    Sue i think they would probably be Eucalyptus globulus - Tassie bluegums
    these were the most commonly grown overseas species for that purpose

    Tassies have trouble turning off though
    theres a split into 2 physilogical traits in Eucalyptus
    the ones that can shut down in drought and those who pump till the last drop

    Globulus is in the latter
    it shows in plantataions cos they start dying off as the water runs out

    Eucalyptus wandoo from WA might be better though because it pumps up to 1.5 x as much as bluegums and can shut off in drought (it sthen shed branches - bad for towns but great for firewood)


    Eucalyptus are great - but theyre not compatible with many other types of vegetation .
    They are ecosystem engineers in that once dominant they define the system (nurtrients, fire, hydrology)
    u shouldnt take their placemnet lightly
     
  11. Ichsani

    Ichsani Junior Member

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    Hi Peter,

    Regarding your dam......
    From what I can make out from your description of the location and conditions surrounding the dissappearing dam (that there is/was a boggy patch upslope from the dam yet downslope(?) from the plantation that fed the water level of the dam....?)

    ...as a tentative explanation (as the topography makes a BIG difference to this, as does the condition of the B-horizon of the soil profile) it would seem that the local hydrological cycle has shifted. This actually happens far easier than most people think..... if the land surrounding your property has been cattle pasture for some time then the water tables have been operating under a far different dynamic than the one that is developing under the plantation...... this really doesn't have much to do with the type of eucalyptus (or the type of deep-rooted tree really!) as one of the common features of this genus is that the tap-root is capable of-

    a) breaking through perched water tables (this is one possible explanations for the boggy areas especially if there is high levels of sub-surface clay)

    b)simply altering the water table locally due to the deeper level of the roots compared to pasture (this will be the main influence if there is no perched water table....something that can really only be established by a texture profile of the soil)...

    What seems more likely from the situation that I can gather is that the area has slumped water tables and the plantation has begun to locally alter this.
    You're going to have to bear with me on this, if I could draw you a picture it would be so much easier to explain...

    .......If you can imagine the water table following the topography of a hill at depth, so the actual level of saturation rises and falls with the undulations of the surface, then you have a typical picture of a water table under forest cover... (this of course is influenced by many factors I know)
    ... now if the land is cleared and put to pasture then the undulations of the water table flatten out (this is proportional to the change in evapo-transpiration rate, the infiltration rate, run-off, sub-surface drainage etc, etc) and the water table comes into contact with the surface. In short the sub-surface drainage becomes surface drainage on the sides of hills that have been cleared (this is the cause of dryland salinty in places where the soil is highly sodic). This sounds like the source of your boggy area that is being affected (note that this sounds like its not actually an artesian spring).......

    Now as to what is actually causing the dam levels to drop.... if as you say Peter, the recharge of your dam is lessening but the other dam is constant...... then I would point the finger directly at the plantation..... if this is correct then the actual level of the water table below the now forested hills will be higher at the tops (whereas they would have been drastically lower under pasture), and therefore the slumping caused so many years ago by a pasture environment is being changed again....

    ...so what can be done? I would suggest that you look for points of lower elavation that new drainage could be developing from (you're probably going to need more rain to find these), as it appears that your dam will now be seasonal in its current position above the new water table. Can you relocate the dam to a new site? Or another option would be to make it deeper, as the same water will be there, just lower down. Pumping the water to a new holding dam would also be an idea as extracting the water from this point (the problem dam) will yeild more water (related to the hydralic conductivity of the soil) at the expense of a small part of the plantation, an expense that seems justifiable in this case. Water is there to share!

    I sympathise with you over the distress this must be causing, doesn't seem very fair does it?
    Don't despair over this, if this is indeed what is happening then the effect shouldn't spread to your other dam. You might have to change some of the water harvesting systems (I would advise increasing them) but this problem is not insurmountable.

    But if it makes any difference I can assure you that the majority of commercial enterprises involving living organisms show a systematic lack of conceptual understanding, let alone recognition of, the impacts of their actions. A very irresponsible set-up, but not a personal one.

    This is only my opinion, one that I have had checked by a fellow hydrology student but it is still highly dependant on the actual characteristics of your area. This is also quite a simplified explanation of water tables as the details of your problem are quite sparse (do you know what type of soil you have?)

    Hope this has been some help... happy to take any questions you may have to higher authorities on the subject...

    Best of luck Peter,

    Regards, Ichsani.
     
  12. Ichsani

    Ichsani Junior Member

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    Just another note on your original questions Peter...

    Water retention is higher in rainforests (or wet sclerophyll that has already been mentioned) because of the higher levels of organic matter in the soil (better pore spaces is this biggest contributer to this), the effects of plantation farmed eucalypts will be different as this design (the monocultural one) will not create the same litter conditions as natural stands of eucs. These comparisons are NOT straight forward. What works in one area can have deliterious effects in another. It is possible to incorporate eucs into effective design but I think the ratios have to be right.

    That said, if you are planning to regenerate rainforest, work on the organic componant of the soil as this will up the plant available water capacity (which has far more influence on growth than water tables!!!!!!!!!!). Look for some books on soil science, (Aust ones) and when you get confused by all the conflicting info, throw them behind the sofa, go outside, sit down and have a look around.... those concepts that make sense to you and your property keep, and those that don't -compost.

    Sorry for the length..... hope you can get at least something useful out of it :)

    NB.....in the first message where I wrote 'sodic soils' I should have said 'saline soils'......sorry about that, there're related but sodic is to do with high erosion levels, not salinty

    All right, I promise no more on this. :)

    Regards, Ichsani.
     
  13. Peter Warne

    Peter Warne Junior Member

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    Ichsani - I must apologise for taking so long to respond to your comprehensive replies to the problem I talked about. I didn't actually notice them until just now, I haven't been at the computer so much. I must thank you for your detailed response. It will be really useful, and I will a better understanding of what elements maybe involved and some idea of options if I decide to do something about it. At present we are not using the lowered dam, it's just that it's much more esthetically pleasing when it's full, and worrying when it goes down. Actually the rains over the last couple of months have filled it again and it's looking nice now. It will be interesting to see how long this lasts.

    Anyway, many thanks for your information and suggestions,

    Peter Warne
     
  14. Ichsani

    Ichsani Junior Member

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    Confessions of a trainee whitecoat....

    Peter,

    Glad to hear that you've got some rain! Thought that I might have scared you off with my replies......I wondered if I was becoming the evil scientist who's advice wasn't welcome! Seriously though, I have to admit that I am studying to be a land and water scientist.....and though I am being institutionalised by Sydney University, I can get access to some very fair dinkum proffs who seem to know what they are talking about (and some who haven't the foggiest either).

    Permaculture One (the big book by Mollison), was the first book that I read about humans and the natural world that made any practicle sense whatsoever. Many books on similiar subjects followed. Most uni texts seem to be too enthnocentric and too narrow minded in their application to be realistic in the long term, but fundamental concepts are quite useful. While university tends to be a little depressing with its traditions, there are some really encouraging (and discouraging) projects. One that has had me somewhat impressed recently was that some plant scientists, biologists, and agronimists who lecture undergrads, got together to espouse native foods, and to warn against biopiracy, (which does happen and Aust. will be of particular interest if we look into our native species as most Aussie plants have some amazing analgesic properties) with some very sound reasons. But there was also involvement with roundup ready cotton, so it seems the uni is playing both sides against the middle.

    Anyway, I'm rambling, trying to avoid studying for my exams. Hope the advice at least helped a little. And for the record, farms and food systems are my favourite subject which is why I find permies so inspiring, and why this forum (and many alternative mags) are so good to read. Its important for me to keep perspective in the face of so much traditionalism and this site helps enormously. I feel there is so much that academics have no idea about.

    And to gardenlen, no not all white coats are here to serve the government and capatilistic investors. I can attest to that. But I do encourage a healthy amount of scientist bashing where it's due.

    Cheers, Ichsani.
     
  15. LittleFish

    LittleFish Junior Member

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    I have a bit of a theory (probably wrong, it may just be the final proof that I am actually a total fruit-loop) that eucalypts are in part responsible for the low soil fertility in Australia.
    The oil in the leaves, apart from being allelopathic (discoraging the growth of competing species) is also flammable and encourages high intensity fire events which (while producing conditions favourable for eucalypt germination, can effectively kill off a lot of other fire intolerant species).
    High intensity fire events can also destroy a lot of the organic matter in the soil, as well as promoting soil drying and encouraging erosion from the loss of soil-surface cover.
    I have a few areas of my block that I want to replant and I will be choosing non-eucalypt fire intolerant local species and eventually thinning out some of the eucalypts nearer the house.

    just an idea

    Stephen
     
  16. ecodharmamark

    ecodharmamark Junior Member

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    G'day Peter, Everyone,

    Great topic!

    Professor Ross McMurtrie from the UNSW School of BEES (Biological, Earth and Environmental Sciences) is conducting studies into this very situation. A brief synopsis of his findings to date can be found here:

    https://www.bees.unsw.edu.au/school/staf ... orest.html

    David Holmgren discusses this issue in his book "Permaculture: Principles and Pathways Beyond Sustainability" and comes out firmly on the side of growing long-rotational mixed species forests, as opposed to short-rotation mono-cultural plantations (2003: pp.41-2).

    Another excellent article (in summary form) pertaining to this issue is available at the following RIRDC page:

    https://www.rirdc.gov.au/pub/shortreps/sr39.htm

    The science is avialable, and anecdotal evidence is rife - Eucs do consume vast amounts of available groundwater. The trick is to do our homework and to ensure that only suitable species are grown in site-specific areas.

    As to what we can do about the commercialised short-rotational monocultural plantation 'empires' that are springing up all over the place...perhaps nature will prevail and disease/fire/drought will put an end to these unsustainable practices?

    I love Eucs, they are my Temple's of Refuge, but I am greatly aware of the damage that they can cause when inappropriately planted in unsuitable landscapes/climate zones/bioregions/etc. Another good reason why it pays to observe nature, and then mimic it, rather than to try and exploit it at all costs.

    Cheerio All, and please hug a tree today (I did!) :)

    Mark.
     

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