EUCALYPTOLOGICS: GIT Forestry Consulting Information Resources on Eucalyptus Cultivation Worldwide :: EUCALYPTOLOGICS: GIT Forestry Consulting Recursos de Informacion sobre Cultivo Sostenible de Eucalyptus :: Information Resources on Eucalyptus Cultivation Worldwide

Eucalyptus poisoning soil? (I)

Seven key issues on Eucalyptus and alelopathy
Or seven reasons why stating eucalypts poison soils is mostly... bullshit

Gustavo Iglesias Trabado

GIT Forestry Consulting - Consultoría y Servicios de Ingeniería Agroforestal - www.git-forestry.com - EUCALYPTOLOGICS

We frequently receive inquiries at EUCALYPTOLOGICS from concerned gardeners, horticulturalists and even Eucalyptus timber plantation owners in regard to the widespread notion of these trees "being poisonous to the soil" and "dangerous for understorey flora". Today we hope to help throw some light over this myth.

Giant Eucalyptus camaldulensis and understorey at Inca Botanical Garden, Malaga, Spain, by Dan Anderson, Exploring the World of Trees, a Tree Species Blog / Eucalipto rojo gigante y sotobosque en el Jardin Botanico Inca de Malaga, España, por Dan Anderson, Tree Species / Gustavo Iglesias Trabado / GIT Forestry Consulting, Consultoría y Servicios de Ingeniería Agroforestal, Lugo, Galicia, España, Spain / Eucalyptologics: Information Resources on Eucalyptus Cultivation Worldwide / Eucaliptologics: Recursos de Informacion sobre el Cultivo del Eucalipto en el Mundo

Fig. 1: Healthy understorey plants growing under an Eucalyptus tree. Image courtesy Dan Anderson, www.tree-species.com (Click image to enlarge)

We picked this example to ellaborate on this particularly interesting topic due to the excellent conditions of this tree as evidence of myth being myth. Approaching one hundred years old, the giant E. camaldulensis at Inca Botanical Gardens has had enough time to deplete and poison the soil around it. Doom predictions would say nothing could be growing near it for more than 50 years. Then why a healthy understorey of bromeliads, palms and lush subtropical plants is thriving under this evil Eucalyptus?

Fig. 2: Monumental Eucalyptus camaldulensis growing among palms in the Inca Botanical Garden of Malaga, Spain. Image courtesy Dan Anderson, www.tree-species.com (Click image to enlarge)

The answer could not be more simple: because a plant causing alelopathic effects on its surrounding habitat is not equivalent to a plant keeping infinite arsenals for chemical warfare that affect everything around it.

SEVEN KEY QUESTIONS ON EUCALYPTUS POISIONING SOILS

Question 1: What is alelopathy?

Alelopathy defines a natural type of interaction between different plants, in which one of them has adapted to release to a defined space around it an amount of natural organic chemical compounds during their normal biologic cycle. These alelo-chemicals can, in certain circumstances, add to other natural competitive advantages result of evolutive adaptation to favour the survival, establishment or reproductive maturity of a certain plant against another in a defined space where resources (light, water, nutrients) are limited.

Question 2: Are Eucalyptus alelopathic plants?

Yes, since Eucalyptus are plants and all plants are alelopathic to some extent, as they all release organic chemical compounds when their discarded biomass degrades, and these natural organic chemical compounds leach on to the soil, where they interact with other elements of local biota.

Question 3: Does alelopathy in Eucalyptus have something to do with they being exotic species?

No. In Australia, where they are native, they also cause alelopathic impacts on surrounding flora. And in any habitat you can find native plants causing the same sort of impacts on surrounding biota in varying degrees. Alelopathic and exotic are two independent concepts, and linking both as the two parts of a cause-effect relationship shows deep ignorance on basic biological and ecological processes. Pay attention when you see both terms in the same sentence, statement or argument in a discussion, as it normally will give you hints on the speaker.

Question 4: How do Eucalyptus alelopathic effects impact other plants?

Following the same pattern than any other plant causing alelopathic effects: in several ways, but very rarely as a single factor.

The combined action of at least...

Natural events to which many Eucalyptus species have adapted their reproductive processes (e.g. fire) while other plants have not, making less desirable habitat for non adapted to some plants while favouring others
Fast development of root systems compared to some plants, which can give them quicker access to soil moisture and making less desirable habitat for water demanding plants there while favouring others
Quick canopy development and litter formation, meaning quick shading of understorey and making less desirable habitat for full sun plants there while favouring others
And the release of natural organic alelo-chemical compounds to the soil, which can inhibit germination of certain plant seeds while favouring others or contribute directly or indirectly to the slower growth of some plants while favouring others

... can cause impacts on any other element of the biota around Eucalyptus. Each of the other plants thrives between thresholds for any given natural factor affecting survival and growth. Probably many other factors could also be included, but those four are enough to illustrate the complex relationships of biota and environment.

For the case of alelo-chemical compounds considered as a single factor in this equation, each different plant taxon will behave differently, some totally tolerating the available amount of alelo-chemicals perfectly, some being affected to a certain degree, and some being non tolerant. It is a dynamic process, and it activates further adaptative processes in all the other plants. Those unaffected will keep growing and reproducing, those non critically affected will evolve towards tolerance given enough genetic variability so some will keep on growing and reproducing, and those non tolerant will be replaced in their ecologic niche by other organisms that will keep growing and reproducing. Evolution under our noses.

A dynamic ecosystem in continuous adaptation. But not anihilation, sterilisation or desertification. Again, pay attention when you any of these or similar terms together in the same sentence, statement or argument in a discussion, as it normally will give you hints on the speaker.

Question 5: Can we safely grow other plants under Eucalyptus in our gardens?

Yes, but results will largely depend on... what your garden is like, what your Eucalyptus are like, what plants you are planting under them and how you manage this small ecosystem. Each plant will have a maximum and minimum treshold for each main restriction to survival and growth, be it water availability and use, tolerance to shade, abundance of nutrients or tolerance to any of the organic compounds present in soil and being released by the Eucalyptus and any other plant nearby. Or any other factor having influence in the final outcome.

Each of your gardens will become a real laboratory and you will have the opportunity to observe what is going on and realize that you cannot blame alelopathy for your other plants dying if you have not watered them during that severe summer drought.

Question 6: What about cultivated forests based on Eucalyptus as main timber species?

This question alone could yield a very long argumentation. It is more suitable as a separate ellaboration, since multiple concepts need to be introduced during its discussion, many of them related to environmental impact assessment, landscape scale considerations, management regimes, and the dynamics in space and time of this more complex than a garden but yet simplified ecosystem any cultivated forest is, irrespectively of the tree species in consideration and its character of native or not to a particular ecosystem.

But, to not let you go with empty pockets, enough mentioning quickly that, the same way you can grow garden plants in the understorey of an eucalypt, many possibilities arise for a wider scale policulture (simultaneous cultivation on the same soil) involving Eucalyptus as tree cover. There are countless examples of these agroforestry systems in all five continents, from relatively simple ones involving pasture or natural grazelands plus Eucalyptus trees (silvopasture) to relatively complex serial crops (multicrop) as sugarcane plus Eucalyptus; maize plus Eucalyptus; pineapple plus Eucalyptus; coffee plus Eucalyptus; Leucaena plus Eucalyptus; cotton plus Eucalyptus; rice, beans and Eucalyptus... as many combinations as adventurous agronomists.

As you can imagine, if the myth of Eucalyptus sterilising soils or making it unusable for every other plant sustained itself, none of these would be possible. But they are. Yet once again, pay attention when you see any of these or similar terms together in the same sentence, statement or argument in a discussion, as it normally will give you hints on the speaker.

Question 7: Why is the myth of Eucalyptus poisoning soils so popular then?

Ahh... now that is a good question, isn't it? It has also many answers, but let's keep it simple.

Because the average urbanite Western citizen is deeply ignorant on agriculture, forestry, the dynamics of ecosystems or long term evolution of landscape parameters by human action.

Because the average gardener, farmer, landowner or investor in trees is too busy making a project work to find time for independent assessment of such questions.

And because there are individuals with either high levels of ignorance, narrow vision or enough knowledge but despicable moral behaviour who keep promoting myth over science and propagating fallacies to discredit one of the most versatile, efficient, productive and diverse plant groups in the world. Genus Eucalyptus.

To all these but especially the last kind, EUCALYPTOLOGICS cordially extends an invitation to join foresters, agronomists and farmers of the world for manual understorey control on those plants that do not grow under Eucalyptus, to grab a tool and labour the understorey crops of Eucalyptus based agroforestry systems that cannot grow on sterilised soils and to enjoy the wildlife that cannot live under the protection of these trees. You can bet that a huge percent of them won't abandon their comfortable chairs for the challenge and will keep behaving like ostriches.

GIT's Eucalyptology Topics

Eucalyptus Pulp & Paper in Spain: towards sustainability

A couple of weeks ago ASPAPEL (Asociación Española de Fabricantes de Pasta, Papel y Cartón) made public the Second Edition of a Sustainability Report (PDF, 5.2 MB) summarising the state-of-the-art for the Pulp & Paper industrial chain in Spain for the triennium 2004-2006.

This report is the result of a Public Consultation Process involving not just the Spanish Pulp & Paper Industry but also representative stakeholders concerned by sustainability as governmental agencies, large paper consumers, landowners, trade unions, non governmental organisations and universities, whose proposals and concerns have been incorporated into the current edition or have positively contributed to the addition of new criteria & indicators for a better monitoring of the sector within the frame of this ongoing participatory process.

GIT Forestry Consulting, Consultoría y Servicios de Ingeniería Agroforestal, Galicia, España, Spain / Eucalyptologics, information resources on Eucalyptus cultivation around the world / Eucalyptologics, recursos de informacion sobre el cultivo del eucalipto en el mundo

ASPAPEL - Papermaking Sustainability Receipt 2008
(Click image to download, PDF 5.2MB)

The opinions and contributions made during the Consultation Process were assessed, validated and verified as accurate and relevant by Bureau Veritas Certification, an independent third party with the role of securing neutrality of all contributions and providing a guarantee of transparency and traceability for the information and data processed.

Many of the macro-magnitudes presented in this report throw some light on key points for Spanish Pulp & Paper Industry Sustainability, as size of timber resources and timber sourcing rates, employment statistics for supply chains, sustainability of forest management practices, positive externalities derived from carbon sink effects, greenhouse gas emissions at mills, water & chlorine use, progresses with ISO & EMAS environmental management systems at industrial processes, residues and subproducts of pulp and paper-making, fibre recycling and a long etc.

EUCALYPTOLOGICS' staff frequently receives inquiries from concerned citizens worldwide about the sustainability of Eucalyptus cultivated forests wondering if the information provided by some media and some of the commonly spread general knowledge are accurate enough. It has been estimated there are some 300 myths on Eucalyptus cultivation that do not resist a logical examination or should at least be put into quarantine status.

Due to the insistence of one of our worried readers, there it goes a first batch of commented macro-magnitudes (facts) in a group of seven.

EUCALYPTUS "TAKING OVER THE WORLD"? Nope.

MYTH: Eucalyptus monocultures are taking over and destroying natural forests in Spain
FACT: +50% cellulosic pulpwood is produced in just 3% of Spanish forestland

Fig. 1: Forestland acreage in Spain and pulpwood resources (Click image to enlarge)

SPANISH FOREST INDUSTRY "PULPING THE SOUTH"? Nope.

MYTH: Spanish Pulp & Paper Industry is "Pulping the South"
FACT: 75% of mill capacity in Spain is fulfilled with locally grown timber, majority of which is Eucalyptus

Fig. 2: Timber resources used by Spanish pulp & paper industry. (Click image to enlarge)

GROWING EUCALYPTUS IS EVIL? Nope.

MYTH: Eucalyptus cultivation only creates irreversible negative environmental impacts
FACT: 1 hectare of Eucalyptus cultivated forest stores 580% more CO2 than the average hectare of forestland in Spain

Fig. 3: CO2 storage in Spanish forestlands. (Click image to enlarge)

EUCALYPTUS PULP MILLS ARE "ECOLOGICAL CRIMINALS"? Nope.

MYTH: Spanish pulp & paper industry is too pollutant and must be closed or relocated

FACT: 93% Cellulosic pulp mills in Spain are into Sustainability & Environmental Certification Processes for their factory processes and supply chains

Fig. 4: Custody-chain certified pulp mills and supply chains in Spain. (Click image to enlarge)

GROWING EUCALYPTUS IS NEGATIVE FOR THE ENVIRONMENT? Nope.

MYTH: Eucalyptus cultivation is an environmental catastrophe

FACT: Professionally managed Eucalyptus cultivated forests in Spain are certified to a 94% by third parties as sustainably managed under PEFC or FSC standards

Fig. 5: Sustainable management certification impact on industry managed timberland acreage. (Click image to enlarge)

EUCALYPTUS PULP MILLS WASTE AND POLLUTE WATER WITH NO CONTROL? Nope.

MYTH: Eucalyptus pulp mills are voracious consumers of water beyond what is acceptable
FACT: Eco-efficiency policies at Spanish pulp & paper mills yielded 1 million extra tonnage and 41% less water use since 1992

Fig. 6: Trends of water consumption and waste water generation at Spanish pulp & paper mills (1990-2006). (Click image to enlarge)

We are firmly convinced a good amount of myth propagators are just missinformed individuals with a narrow view of forestry in general and the interconnections of forestry, environment, industry and ecology in particular.

EUCALYPTOLOGICS must contribute to a proper dissemination of sound information and to the education of general audience on these important topics no matter if at local, regional, national or global scale. And renewable, recyclable and sustainable primary resources as Eucalyptus timber is can achieve the category of strategic from many standpoints. Our overpopulated greenish Gaia needs of a wise use of its finite resources to support itself in the long term or it will perish.

GIT's Eucalyptology Topics

Eucalyptus and soil depletion: quite a bit of a myth

Proper Eucalyptus crop management = Proper soil management

Gustavo Iglesias Trabado

GIT Forestry Consulting - Consultoría y Servicios de Ingeniería Agroforestal - www.git-forestry.com - EUCALYPTOLOGICS

One of the factors that have been used and abused for the demonisation of Eucalyptus trees is "their ability to deplete soils, so nothing can grow where eucalypts once grew". A myth very in the same line of the "nothing grows under gum trees" one. Pretty surely those propagating these ideas and those giving credit to the previous have never been to the natural habitat of these trees in Australia, whose rich agricultural and livestock production happens each day mainly on previously cleared land once covered with eucalypt forests. And quite possibly myth believers have never been into an eucalypt plantation either.

What is sure is that Eucalyptus can perfectly be grown under sustainable forestry principles, and that knowing your soils and your plants before taking opinion is very important. Soil management under sustainability philosophies relies basically on the simple principle of "what you get out of it should come back". Return nutrients that you extract, or at least try to minimise nutrient losses. Keep the balance. Think long term too.

Eucalyptus nitens early growth post harvest in Galicia, Northwestern Spain / Crecimiento temprano tras cosecha en plantación de Eucalipto nitens, Galicia, España / GIT Forestry Consulting. Consultoría y Servicios de Ingeniería Agroforestal

Here you have an example. Water, light and soil nutrients transformed into timber grown in short rotations. Timber extraction, but return of nutrients stored in bark, leaves and branches to the soil. Appropriate fertilisation to cover the minimum losses caused by water, cellulose and lignin storage in timber and to aid a next generation of trees to establish well. Et voilà! Healthy soil, and more fast growing timber.

Generalizing on the interaction of plant crops and soil is never wise. There are many types of soil, and many types of plants. Generalizing on the interaction of Eucalyptus and soils keeps being temerary, since there are several hundred species of the former and many dozen common types of the later. Generalizing on the interaction of a forestry production scheme with soil or other pieces of the ecosystem in which it is established is the equivalent of gossip.

The first persons interested in sustainability of tree farms (be them Eucalyptus based or not) by the implementation of good management practices are investors in such ventures, foresters in care of them and forestry engineers designing them. All in all, we have been following the same philosophy for some two hundred years of forestry science. And we may mistake, but surely learn from it. Some myth propagators apparently don't.

So, if earlier we took a trip from "nothing grows under eucalypts" to "nothing would grow without eucalypts", now we have taken one from "nothing grows where eucalypts once grew" to "crops keep growing where eucalypts once grew". Ironies of tree mythology.

GIT's Eucalyptology Topics