Tree care for the Land Custodian: part two

Cassian Humphreys underlines how tree care attends to the bottom end of the pump.

Plants are living pumps for the nutrient cycles on which all life is dependent. They harvest inorganic nutrients from the atmosphere and make them organic by embodying them. A large amount of the carbon they store is also shared in the form of carbohydrate – sugars – below ground. This is gifted in exchange for water and elements like phosphorous, nitrogen, potassium, magnesium, copper, sulphur, zinc, calcium, molybdenum, iron, chromium, cobalt, iodine and so forth. Science observes that mycorrhizae – classical Greek for ‘mushroom-root’: part plant/part fungi – enable up to 10 times the nutrient assimilation compared to a tree’s root hair operating alone.

One thing is very clear with the science on the soil-food-web (often called the wood-wide-web): woody-plants in nature cannot succeed without association. We negate the natural plant/micro-biome by biologically desertifying soils, with the end result being stress, sickness, pests, disease, and short lifespans.

Though we can get away with short-lived plants in a nutrient-deficient cropping-cycle reflective of agriculture, with amenity trees, short-lived lifespans negate environmental benefits.

Syntropic farming

One of the current fringe landcare movements involving plant diversity is Syntropic farming, which involves the growing of five different genera of associate plants in a crop environment.

Syntropic Farming recognises the soilfood- web science, now shining a light on plant associations, is demonstrating the shared resources helping build resilience are more than just nutrients. Plant associates literally program each other to succeed with acquired experience and information via the micro-biome. This will sound far fetched to those who lack natural intelligence (NI), yet to the ‘street-smart’ it’s obvious. It’s true to refer to an intact ecosystem as a literal biological computer program, and in southwest WA there are still some pristine ecosystems.

To demonstrate my research I’ve provided a record of all the native understorey plants I found growing in association with Marri-gums within a two-month flowering time. All were photographed under the Brockman Highway ancient Marri-gum shown at the start of this article, and Maslin Reserve, Bridgetown, WA, a local Marri and Jarrah Gum woodland. There are up to 13 different associate genera in this record, with 30 different species.

There to see

In nature, natural intelligence unites all. Recognising the natural biological exchange between plants and their living associates, where via the rhizosphere trees bargain for minerals in exchange for sugars, is key. When we compare this to stripping soil life via mechanisation, fertilisation, pest and disease control, or biological desertification, it’s an illustration of artificial intelligence (AI) versus NI. We can call this humanity’s ego versus creation.

Regardless of what we believe, nature is a masterfully fine orchestration, and the other a drug-induced 1980’s rendition by comparison – Mozart V Culture Club, perhaps?

Experience of the oasification of southwest WA, famed for being one of the most biologically diverse regions on Earth, yet on the poorest of soils, is a huge awakener (there are parallels to the east-coast rainforests).

The nutrient cycle: Plants as pumps for the nutrient-cycle (the primary producers) harvest their own energy from sunlight. They harvest elements and water from both the soil and atmosphere (in association with the microbiome). They synthesise the sun’s energy with inorganic atmospheric elements, embody them and then make them available (in organic form) to all life. With animals and humans (secondary producers) that eat plants, or eat other animals that ate plants, so the cycle shifts from the Atmosphere to the Earth via the plant bodies, followed by the creatures. So it is true to say that functioning as living pumps and in being pumps for the nutrient-cycle plants unite our atmosphere and earth.

The goal

We have known of these associations in arboriculture for decades, yet it’s only now treating soils is starting to become mainstream practise, known as Plant Health Care. Tree Health Care is well established as a service in the US, although now, with the climate-change initiative, Australian arboriculture is starting to get serious as we unite cultural practises that attend both ends of the pump.

As a pioneer in the Australian Conservation Arboriculture movement, I am very excited to see trees, the living backbone of land-based ecosystems, are starting to get the attention they deserve. As part of my personal initiative to be integrated as a landcarer, I have shifted my focus from arboriculture into naturaculture. Under this banner, through education, I aim to make conservation arboriculture available to all who make up landcare, from professional vegetation-managers to land custodians.

In the mix of local understorey plant associates, we have the Australian Bluebell, Clematis, three species of Rice flower, a Grass tree, Pultenaea, Patersonia, Fringe Lily, Lomandra, Ptilotus, Kangaroo paw and the Southern cross (half the species have yet to be IDed). Not photographed, but seen on site, were species of Native Wisteria, Coral Vine, Tassel Flower, Cycad, Leucopogon, Nuytsia and Acacia – 30 species of tree-andplant associate. This list does not include those plants not in flower.

The nutrient cycle

What is it the land-custodian needs to know to be a landcarer?

It’s not enough to care for Earth in concept, statement or politically. This has to be as a field-cultural practice, otherwise there is no benefit to Earth. This is about managing, conserving, utilising, and co-creating resources in concord with Earth’s biology.

Unless programmed by NI, AI is of little use here.

Let’s make it simple – a challenge when we see how complex academic science makes natural science. To get sustainability, to literally rewild Earth, we need to understand the nutrient cycle. Misunderstanding this is a major roadblock that keeps land managers stuck in the loop of futile controls that yield a multitude of side effects which cost way more than they benefit.

In support of this series narrative, following are some naturacultural terms and practises, with explanations, I created:
• Naturaculture – Latin for the culture of nature
• Nutrient bed – the carbon component of an ecosystem
• Plant system – the plant component of an ecosystem
• Oasification – based on an oasis, the opposite to desertification
• Aeration – soil oxygenation, an essential strategy in the naturacultural toolkit
• Tree Health Care – tree health is insurance against tree failure, biologically and biomechanically. Like healthy humans, healthy trees are naturally resilient to disease and breakage. Tree diseases like Phytophthora, Phellinus, Chrysoporthe, Marri-Canker, Canker- Syndrome, and Polyphagous-Shothole Borer are common signs of desertification. Healthy trees are resilient. Stressed or ‘sick’ trees are not. Ensuring tree health is all about sustaining healthy, biologically diverse soils, supported by air, water, carbon, minerals, and the microbiome.

Fig 3. Dr Alex Shigo’s diagram from his book Modern Arboriculture is fundamental to help us recognise the critical why?

Alpha trees

I have witnessed natural rewilding of roadside verges adjacent to State Forest and National Parks in southern SA and southwest WA. As a result of decades of people pressure and herbicide application adjacent to urban and rural land, weeds are generally better supported than native-plant regeneration. This is also true of many failed revegetation projects when the below-ground microbiology is missing. In such growing conditions there is no reason to add biology. For the sake of the Ancient Marri-gum shown on these pages, all I would add is air via verticalfissure work. With historical roadsidegrading, it is likely compacted soil will still exist, and with natural microbial propagation in the face of re-opening the soil, and rewilding with understorey plant proliferation, nature will look after the rest.

However when it comes to treating this McLarty Street Bridgetown Marrigum shown in Figs 4-5, based on its turfbased growing environment, I would gift this forest legend the whole bottom-end package.

Why is this tree a legend?

As discussed in my podcast and in Part 1 of Tree-Care for the Land Custodian, Marri-gum is one of the best examples of a phoenix tree I have seen in WA, a specialist at transitioning from a forest tree into field-pasture tree. In Fig 6 we can see the original upper crown, formed when this tree stood in a high forest, in Fig 7 (delineated by a dotted line) we can see the lower crown forming since forest clearing. What I’ve witnessed of this legend genus to date is that with sufficient vitality, old-forest trees will generate canopies to the ground, optimising the full biomechanical benefits of being field pasture trees.

It’s the Alpha-trees that are adept at such transition.

Fig: 4-5. The Brockman Highway through Milyeannup State Forest and Blackwood River National Park between Nannup and Augusta. Despite roadside grading, it’s a classic example of natural rewilding, the environment the Brockman Highway ancient Marri-gum is growing in. Backed by a smell test, I validated the soil environment based on the science of the Soil Food Web. The ultimate test will be via a microscope.


With homage to such tenacity I would gift this tree a 25m by 25m treatment area, largely outlined by the tree’s dripline, excluding the Structural Root Zone, with three vertical fissures every square metre, and another three smaller fissures for tube-stock understorey plants (the species listed above), and hand forking the soil surface with mulching, framing the outer area and capping with logs to help mitigate future people pressure and soil compaction. This involves the establishment of a nutrient bed and plant system.

Based on study of Maslin reserve, I would include nature’s biochar in the mix. This cultural/contractual process is covered in my AA article The Heart of Arboriculture in the Oct/Nov 2021issue. With my new website and educational workshop series, this process is to be offered up to the landcare professions via a workshop Australia-wide, starting with Canberra.

A veteranised ancient Marri-gum – Corymbia calophylla – which also featured in part one. It’s a significant habitat tree with an active hollows and natural crown suppression. Study of its growing environment yields much in the benefits below ground, benefits that are best expanded on, and offered up to other ancient and veteran trees in similar locations. This tree is a very interesting study. Although it would certainly have been challenged by roadside construction – evidence of a history of Marri Canker is a sure sign of past stress – two thirds of its rootzone is plugged in to the kind of species diversity the tree evolved with. Species-diverse ecosystems Downunder are reflective of poor soils and nature’s tendency to grow species-rich ecosystems to assist with nutrient sharing and nutrient assimilation.

Phoenix trees

Another important transformational feature learned from Marri-gums is the capacity for this species to recover from major crown failure – to generate a new crown even from fractured snags.

The Marri-gum’s generation of buds, leaders and limbs from delaminated, fractured and decayed snags is second to none. Study of Maslin Reserve for some weeks, and a brown-rot decay fungi common to the forest and throughout southwest WA, has shown me this is a fungi that has co-evolved with the local gums. It assists the process of decaying internal ballast via processing the heartwood into compost.

An essential forest fungal organism – the many downed composting logs in the reserve are testament to this – this fungi is an important means to help rebirth new trees out of the old snags. The decayed heartwood itself is a significant resource, with the cellulose degraded by the fungi and lignified tissue retained, literally nature’s biochar. Manmade biochar has the cellulose burned from it, and as a porous, ligninrich resource, it is excellent at housing microbiology. Biochar commonly infused with compost tea is proving to be a popular resource throughout landcare. Examples of the limits of hot burns (overcooking) verses cold burns are across the board in nature (this relates to managing forest fuel load, as well as creating compost), therefore I aim to initiate a microbiologist’s analysis of man-made biochar verses aged brownrot. Knowing nature I suspect the wildbiochar is infinitely more superior.

Figs 7-8. A 40m leaning Bridgetown Marri-gum, adjacent to Maslin Reserve, with a forest-crown reiterating into a field pasture-crown.

Long live the tree, and long live conservation arboriculture.

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