Category: ecosystem services

The next big thing… arbuscular mycorrhizal fungi

Aotearoa’s nature is defined by its iconic species like kauri and pōhutukawa, kiwi and kea, and even insects like wētā. These species are undeniably important, but it’s now time for some credit to be given to a less visible group – arbuscular mycorrhizal fungi (AMF).

Little known to most, AMF have been an important part of the Earth’s ecosystems for 450 million years. Around 80% of all plant species live in symbiotic relationships with AMF.

AMF colonise plant roots and support the host plant by extending fine filaments, called hyphae, into the soil. These tiny hyphae can access water and nutrients that would otherwise be missed by the host plant’s roots. This gives plants a major boost. The extra intake of limited nutrients, like nitrogen and phosphate, enhances the plant’s resistance to environmental stressors – such as disease or climate change.

Native Forest, Tauranga. You can’t see them, but AMF are in this photo! Photo by Ngaire Ferriss

But it’s not all one-sided. AMF benefit too, receiving carbohydrates and fatty acids from the plants in return for their work.

It’s no secret that native Aotearoa ecosystems are struggling. Anthropogenic challenges, like climate change, deforestation, invasive species, and soil depletion (I could keep going), make it difficult for our native plants, and the fauna which they support, to thrive.

The same goes for our valuable agricultural systems, which struggle with similar challenges. Luckily, a recent review of AMF in Aotearoa’s ecosystems suggests that these fungi may be able to help us out.

Aotearoa is home to 38 identified species of AMF. It is thought that there is functional specialisation across species, meaning that each species can offer different benefits to its host plant.

Kānuka forest, Paparoa. Kānuka commonly interacts with AMF. Photo by Ngaire Ferriss

Studies show that AMF have the ability to improve plant growth. For example, kānuka and mānuka growth was significantly enhanced when AMF was added to the soil. Another study showed an increase in root and shoot growth in the sample apple trees. These benefits can assist with disease resilience, as greater size means greater defence.

Crop plants can also benefit from this growth. When New Zealand-made mycorrhizal products were applied to plants like lettuce and plantain it increased the size of the crops. Other plant species saw an improved nutrient uptake, which can assist with carbon storage in soils. Aside from helping plant health, this is a global warming win, locking carbon away and preventing it from accumulating in the atmosphere. And unlike chemical fertilisers, mycorrhizal products don’t contribute to soil depletion. While a great temporary solution, crops relying on fertilisers lack many of the components soil needs to thrive. On the other hand, AMF add organic matter, nutrient availability, and long-term soil health.

So far, it’s sounding pretty good. However, AMF isn’t the solution to all our problems yet. Research is expensive, and we currently lack knowledge on AMF species, functions, and relationships with plants. The next steps in advancing AMF research include increasing AMF culture collections, characterising communities at a precise level, and discovering associations with plant species. If this can happen, a whole world of benefits could be unlocked. Native plant diversity and abundance could shoot up with specific applications of AMF – increasing resilience to stress, enhancing growth, improving soil quality, and improving competition with invasive species. Agriculture could also be supported by these fungi, using crops which support diverse AMF communities. By making use of the skills of different AMF species, crop plants could enjoy increased nutrient uptake and resilience, creating more productive and sustainable farms.

It seems our secret weapon has been beneath our feet all along. Now that AMF have had their big introduction, perhaps they can help forge a new path toward healthier soils, healthier ecosystems, and a healthier Aotearoa.

This article was prepared by Postgraduate Diploma in Applied Science student Ngaire Ferriss as part of the ECOL608 Research Methods in Ecology course.

September 28, 2026
Is nitrogen the only driver of freshwater eutrophication?
Imagine a typical stream or river running through farmland. It looks clear enough at first glance, but you start to notice something is not right. Algae begins appearing over time. The water quality gradually declines. Something is leaking into the ecosystem and altering the natural environment.

So the question becomes: what is responsible?

For a long time, scientists suspected a single culprit. But, in the early 2000s, soil scientist Andrew Sharpley and his colleagues, including Lincoln University researcher Professor Richard McDowell, set out to investigate why water quality problems persisted even when nutrient management practices were in place.

Their research, published in Plant and Soil (Sharpley et al.,2001), revealed that nutrient loss from farms to freshwater was far more complicated than previously thought.

Instead of one obvious offender, the evidence pointed towards two main suspects: nitrogen and phosphorus.

Solving this mystery changed how we manage nutrients within agricultural landscapes.

Scoping the area over Waitaki River at Ikawai, Canterbury. Photo taken by author. CC-BY-NC

Suspect #1: Nitrogen- a.k.a ‘the quiet traveler’

Nitrogen moves easily through soil, making it difficult to trace back to its source.

Unlike phosphorus, which tends to stick to soil particles, nitrogen is highly mobile. It likes to dissolve in water and travels easily through the soil profile into groundwater systems, ultimately reaching streams and rivers. Because of this MO (Method of Operation/ Modus Operandi), nitrogen losses often occur out of sight below the surface, making them harder to catch and manage.

For a long time, nutrient management strategies focused heavily on the reduction of nitrogen loss. That made sense. If nitrogen moved easily through soil and into waterways, then controlling it should have solved the problem, right?

Well it didn’t.

Even when nitrogen losses were reduced and put under house arrest, freshwater quality issues often remained. This meant something else was involved… nitrogen had an apprentice picking up the slack.

Suspect #2: Phosphorus- a.k.a ‘the one hiding in plain sight’

Phosphorus has a different MO to nitrogen. Instead of traveling through groundwater channels, phosphorus often attaches itself to soil and sediment particles and is transported during rainfall and runoff events. Although dissolved phosphorus can also contribute to eutrophication, most phosphorus losses are strongly linked to surface processes, such as erosion and overland flow. It, essentially, disguises its movements during significant events, helping to evade detection.

Sharpley and colleagues showed that this difference between nutrients matters. Managing nitrogen alone was not enough, because phosphorus followed different pathways through the landscape.

Even more interestingly, strategies that were designed to reduce nitrogen loss sometimes came with unintended consequences. In some cases, the application of manure that was applied based on the crops nitrogen requirements, had repercussions that caused phosphorus to accumulate in soils, increasing the risk of phosphorus loss during runoff events.

So the investigation suddenly became more complicated.

It wasn’t just about catching one suspect anymore.

An event that our suspect uses to disguise its movements while being attached to soil particles. This example is the Leith River, Otago, in flood. Photo taken by author. CC-BY-NC

A breakthrough clue: location matters more than we thought

By this point, researchers realised that nitrogen and phosphorus behave differently, travel through landscapes in different ways, and require different management strategies.

One of the most important insights from this research was that nutrient loss doesn’t happen evenly across farms. Instead, it tends to occur in specific areas where high nutrient availability overlaps with the active transport pathways, such as runoff.

These are known as Critical source areas.

Think of them as the crime scene hotspots.

Not every paddock contributes equally to nutrient loss. Some areas of the farm are more prone to loss than others, especially where saturated soils, slopes or drainage pathways allow for nutrients to move quickly into waterways.

This changed the way scientists and researchers approached nutrient management. Instead of trying to control the nutrients everywhere at once, the attention shifted towards identifying the places where interventions would make the biggest difference.

Following the evidence: the phosphorus index

Once researchers realised that location played such an important role, they needed a way to identify where losses were most likely to occur. This led to the development of tools like the phosphorus index.

Rather than simply measuring how much phosphorus was present in the soil, the phosphorus index combines information about soil phosphorus levels with landscape features, such as slope, runoff risk and transport pathways. Together, these factors help identify where phosphorus is most likely to leave the farm and enter waterways.

Instead of treating entire farms the same way, the phosphorus index helps target management practices to the places that matter most.

Almost like predicting the potential next target location.

Example of potential critical source area where nutrient runoff and drainage pathways overlap. Photo CC BY-SA 2.0 by Doug Kerr.

Plot twist: solving one problem can create another

One of the most interesting outcomes from this research was the discovery that managing nitrogen and phosphorus separately can sometimes create trade-offs between them.

Practices that were designed to reduce nitrogen losses can increase phosphorus accumulation in soils simultaneously. At the same time, strategies that reduce phosphorus runoff can increase nitrogen losses through drainage pathways.

This meant nutrient management couldn’t focus on just one suspect anymore. Both needed to be considered together.

That shift in thinking helped to reshape how scientists and land managers approach water quality protection today.

Despite these advantages, the case is far from closed. Excess nitrogen and phosphorus continue to enter waterways in New Zealand and around the world, contributing to algal blooms, reduced water clarity, oxygen depletion and the degradation of freshwater ecosystems. While researches now have better tools to identify and manage nutrient losses, protecting water quality remains an ongoing challenge.

Why does this case still matter?

The work by Sharpley and colleagues helped move nutrient management away from simple nutrient solutions towards more integrated approaches that recognise how nitrogen and phosphorus interact across landscapes.

Instead of asking how many nutrients are present, researchers began asking: Where are they most likely to move to?

That question led to better tools, better targeting of mitigation strategies and a stronger understanding of how agricultural systems influence freshwater quality.

By recognising that both nitrogen and phosphorus contribute to eutrophication through different pathways, scientists and land managers are better equipped to reduce excessive algal growth and protect the health of rivers, streams and lakes.

The mystery of nutrient loss is far from completely solved. But thanks to research, we now know where to look and which suspects deserve the most attention.

This article was prepared by Master of Science student Emma Meikle as part of the ECOL608 Research Methods in Ecology course.
- Sharpley, A. N., McDowell, R. W., & Kleinman, P. J. A. (2001). Phosphorus loss from land to water: integrating agricultural and environmental management. Plant and Soil, 237(2), 287–307. https://doi.org/10.1023/a:1013335814593
September 21, 2026
A fiery topic: shining light on the acacia understorey

The story of the understorey

New Zealand is home to thousands of native plant species, of which a whopping 80% of these trees, flowering plants and, ferns are endemic – found only in Aotearoa and nowhere else!

A thousand years ago the forests of NZ were comprised of only natives. Since then exotic plants have made their way here – crossing the great seas on waka and sailing ships and riding the air in jets to beautify the human gardens of tomorrow. Sometimes these exotics do more than beautifying modern gardens, they expand and conquer, alongside the human colonists.

Plant invasions pose one of the most large-scale threats to the conservation of biodiversity worldwide. This issue is only getting worse with climate issues allowing for more habitats and niches to be exploited by plant invaders that were previously unavailable.

Acacia is a plant genus that is notorious for enacting the invade and conquer regime, often considered a problematic and invasive weed, with wanted posters in multiple regions of the world. Acacia are also well known by their street name: wattles.

Figure 1. Photo of Acacia dealbata. Image from Donald Holbern (CC-BY-SA-2.0)

But why is acacia considered an invasive weed?

Wattle is a grade-A problem maker, changing ecosystem structures and soiling the soil. It achieves these feats by changing the composition of the forest, altering the variety of species present in the forest and changing the microbiome of the soil (all the little bacteria and microscopic life we can’t see with the human eye). It also likes to participate in, and encourage, arson for its own benefit.

You can read more about how acacia messes with ecosystems and soils soil here:

Ecosystems -> https://repositorio.uchile.cl/bitstream/handle/2250/154809/art04.pdf?sequence=3
(Disclaimer – Requires translation from Spanish unable to provide pre-translated copy)

Soiled soils -> https://doi.org/10.1371/journal.pone.0086560

Acacia and fire

So, why does acacia love fire so much?

As Acacia benefits from fire. Wattles are light loving, early successional plants. They survive after fires through regeneration from seed. This means that after a fire, when there is lots of available light, the Acacia species is one of the first woody plants to start growing and can dominate the scene.

The Acacia genus is also a major fire hazard due to its leaf litter and twig structure increasing the flammability of the fuel giving the genus a moderate/high flammability. This means they catch fire relatively quickly and are able to sustain it as well.

This flammability creates a lovely little loop of increasing fire risk – fire burns acacia, acacia seedlings profit from the fire that opens up the canopy and grows like crazy, Acacia then dominate, increasing risk of fire once more.

Wildfires are an increasing risk as climate issues intensify, making wildfire management a more pressing topic. So, if we think of wildfire management in forests in New Zealand, we could expect that forests with high proportions of acacia to be at a high risk for wildfire.

Figure 2. Illustration of Acacia melanoxylon by Rosa Fiveash

The burning question

So, will Acacia remain present once it’s entered a forest scene, especially if its dominant there? Will it keep coming back, continuing to invade and conquer the forest?

Well…

Some scientists from Lincoln University (Tim Curran, Jon Sullivan and Azhar Alam) wanted to know exactly that. Heading off to investigate the story of the understorey of an wattle dominated forest.

The hot and heavy science:

The study was done in sunny Picton, Marlborough, in a forest found in Picton Bay. The forest was a mixture of native and exotic woody plants where the Acacia species were the most common.

Tim, Jon and Azhar devised 24 random 10×10 m plots that were about 3 km apart. These plots had two main acacia species invaders: Acacia dealbata and Acacia melanoxylon, with A. dealbata being the main invader and common canopy species in these plots. The plots were sampled by measuring the abundance of each species present in different height categories:

<0.3m, 0.3-2m, 2-5m, 5-12m, 12-25m.

To measure flammability, 70 cm offcuts were abducted from 8 mature and healthy acacia trees between the two species in the plots and sealed in black plastic bags and chilled.

Offcuts were then subjected to burning where their flammability was measured in four categories:

Ignitability: How many of the samples ignited per species,
Combustibility: The max temperature reached during burning,
Sustainability: How long the offcut burnt for after the source of the fire was removed,
Consumability: How much burnt after the flame stopped.

Figure 3. Demonstration of the plant BBQ being used to measure flammability (Video by Fire Emergency NZ | YouTube)

You can read more detailed versions of the methods and stats-> https://doi.org/10.1016/j.foreco.2023.121671

Methods for flammability -> https://doi.org/10.1071/WF15047

What was hot:

So, what did they find? How does a forest respond when it’s dominated by acacia? Do Acacia species continue to invade and conquer or…
Enter the underdogs of the acacia forest: the NATIVES!

The study found that in an Acacia dominated forest where disturbances, like landslides and fires, were not common that the Acacia seedlings did not survive beneath their own canopy. Instead the understorey was populated and dominated by native forest species! But why?

Well, the Acacia species is a light loving genus of plant, sunbathing is a favorite hobby. When there is a forest with a dense canopy you get shade. Shade is something that the Acacia species do not cope with.

But what does cope with shade you ask?

Well, none other than NZ natives of courses.

That doesn’t mean that Acacia species were absent in the understorey. The Acacia species dominated the height category of <0.3 m, making up most of the seedlings present. Native plant species dominated every other height category.

If the forest environment was to remain undisturbed then the next generation of forest species would be dominated by NZ native plants. The abundance of Acacia would also slowly decline over time.

This is great as we regain native forest. Another win is that a majority of Aotearoa’s native plants, such as broadleaf (Griselinia littoralis), have low flammability, meaning that they don’t catch fire very easily. Overall, this would likely lower the forest’s wildfire risk – YAY.

However, that is the future. For now, the forest still has an increased fire risk. Acacia dealbata was the 5th most flammable plant species in the plot and the most dominant.

A single fire could still change the entire game, causing a great forest reset due to this high flammability from the presence of the Acacia species. This is also a long-term risk as once A. dealbata is present in an ecosystem they tend to persist, even under native canopies.

_{“This is fine” meme, edited in imgflip by the author}

All it would take is a fire, or another large-scale disturbance, for the Acacia species to dominate once more, due to the existing canopy being cleared and the light-loving Acacia seedlings skyrocketing up to form the new canopy. Like a good villain, they can always come back.

The author, Kayley Wiffen, is a postgraduate student in the Postgraduate Diploma of Applied Science at Te Whare Wānaka o Aoraki Lincoln University. This article was written as an assessment for ECOL 608 Research Methods in Ecology.

Paper Reference: Alam, M. A., Curran, T. J., & Sullivan, J. J. (2024). Variation in understorey floristic composition regeneration and fire hazard under Acacia invaded forest canopy in New Zealand. Forest Ecology and Management, 554, Article 121671. https://doi.org/10.1016/j.foreco.2023.121671

September 15, 2026
The war beneath your feet: soil decides the fate of plants
You stride through lush grasslands. The scenery seems perfect. But lurking just below your feet is a battlefield.

It’s not an obvious one, of course. There are no bombs going off or explosions or yelling; but there are millions of tiny creatures locked in battle for resources and life. And whoever wins determines whether the plant life above it survives.

This blog post has been inspired by research published in 2015 by scientists of Lincoln University, AgResearch, and their international colleagues. They examined whether soils from different pastures in New Zealand naturally inhibit soil-borne plant pathogens.

Figure 1. Grass roots penetrating the soil. The majority of activities that affect plants occur below ground level. Source: iStock/Getty Images

The Invisible Threat

Many important plant diseases originate underground rather than from the aerial parts of plants, such as leaves. They attack plant roots and stems before visible symptoms appear above ground. By the time one notices any symptoms of disease, the damage may already have been done.

And here is the scary part: these silent killers can reduce pasture productivity by 40–50%. Can you imagine how devastating it is to lose nearly half of your production to something unseen? Such is the case in pastures where crop rotation and chemical controls cannot always solve the problem.

Instead of asking the conventional question, scientists started to wonder:

What if the soil could defend itself?

Soil Is Not Just Dirt

It is easy to think of the soil as lifeless material, but this is far from the truth. Soil is one of the most biologically diverse ecosystems on Earth. A complete microbiota lives within it: bacteria, fungi, and other microorganisms interact continuously. While some assist plants in absorbing nutrients, others … kill them.

Some soils inhibit diseases. Such soils are referred to as disease-suppressive soils, and their action falls into two categories:

General suppression: the microbiota competes with the pathogen,
Specific suppression: some microbiota attack the pathogen itself.

Soils with high plant diversity likely contain more diverse microbiotas, which suggests a high disease-suppression capacity.

But how can one measure such a phenomenon?

A Clever Way to Test Soil

The researchers developed an interesting experiment to test the soil under examination. Rather than using conventional grass or legumes that can be found on pastures, they opted for something completely out of the ordinary: kale.

And why kale? This plant is not usually used on pastures. If disease does not occur, then it shows that the soil is pathogen-resistant in general.

Furthermore, they exposed the plants to a well-known pathogenic fungus named Rhizoctonia solani. And this one leads to a specific disease called damping-off. Plants affected by the disease exhibit dark lesions near the base of the stem which cause plants to fall, like broken wires.

So, basically, the process works as follows:
Introduce the same plant into different soils;
Infect the plant with the same pathogen;
Observe the results.

Figure 2. Seedling damping off showing dark spots on stem bases. Seedling damping off may result in death of the seedling before establishment. Image credit: AA Seif and AM Varela, icipe. Source: CABI PlantwisePlus Knowledge Bank.

All Soils Are Not Equal

The experiment was conducted using four New Zealand pasture soils, including Lincoln, Eyrewell, Rotorua, and Kurow soils.

Same plant. Same pathogen. Entirely different results.

Some soils promoted rapid spread of pathogens; others reduced their effect considerably. There were significant differences between disease levels in the various soils.
- Final disease levels were highest in Rotorua soil.
- Disease progression rate was highest in Kurow soil.
- Lincoln soil displayed maximum resistance, with minimal disease levels in the control.
Same experiment. Different soil. Entirely different results.

And here comes the moment when it all becomes evident:

Soil is not just a neutral element. It actively influences the experiment.

If a soil keeps plants healthy, it’s suppressive. If plants collapse… not so much.

Figure 3. Sampling the soil is essential for research purposes on the properties and disease suppression abilities of soils. Image credit: William, Adobe Stock. Source: Farmers Weekly.

The Twist: Some Soils Had Been Infected Already

Without even having introduced the pathogen, some soils exhibited symptoms of infection. For instance, in Kurow soils, damping-off disease symptoms appeared in the control group as well. This indicated that the pathogen was already present but dormant until the required environmental conditions prevailed.

It could be termed an underlying threat embedded in the soil. Furthermore, pathogens, such as Rhizoctonia solani, can survive between successive cropping seasons, affecting both pastures and future agricultural crop growth.

It’s Not Only “How Many” but Also “How Quickly”

Besides assessing how many of the plants became diseased, the authors also took into account the dynamics of disease development. Why does this matter?

This is important because a slowly developing disease will allow the plants to develop properly before being affected. The faster moving disease will kill them much earlier.

Two metrics were used to assess this:
Disease Incidence (DI) – number of infected plants at the end;
Area Under Disease Progress Curve (AUDPC) – a measure of disease development over time.
Imagine that:
DI is the final result
AUDPC is the whole game
And often, their narratives may be very different.

Why It All Matters

It isn’t just scientific research for research’s sake. With knowledge of how soils resist disease, we could:
- Improve our soil management techniques,
- Cut down on chemical use,
- Increase productivity from our crops and pastures,
- Create a more sustainable agricultural process.
Rather than battling pathogens directly, we could fortify our soil against disease.

That’s where it gets revolutionary.

The Bigger Picture

Agriculture of the future may rely less on adding things to soil…
And more on what is already thriving beneath its surface.

When you look at a flourishing farm, remember this:
It is not only the plants that prosper. There is an entire ecosystem underground, sustaining all life. And in this unseen world, each microbe counts in the battle beneath our feet.

This blog was prepared by Vikram Shankar Malagi, a Master of Bioprotection student at Lincoln University, as part of an assignment for ECOL608 Research Methods in Ecology.

References:

Dignam, B. E. A., O’Callaghan, M., Condron, L. M., Raaijmakers, J. M., Kowalchuk, G. A., & Wakelin, S. A. (2015). A bioassay to compare the disease suppressive capacity of pasture soils. New Zealand Plant Protection, 68, 151–159.

http://www.nzpps.org/nzpp_abstract.php?paper=681510
September 7, 2026
Polka dots, patches and pinstripes? Productive pasture patterns

Do I need to apologise for the overly alliterative title? The excessive use of P’s aside, this title is still ridiculous, who has seen a polka dot pasture? Or a pinstripey paddock? They sound like a figment of Dr. Seuss’ imagination!

But they’re not, it’s science – an ingenious recipe, mixing landscape design, with a pinch of ecology, and a tablespoon of agriculture. Let’s get cooking!

When did we (and by we I mean the human race/ Homo sapiens/ mankind/ womankind/ humanity/ Earthlings), when did we decide that livestock grazing pastures were to be squares of fenced grass? It was probably somewhere around 12,000 years ago when we stopped being nomadic and started agricultural farming.

Fenced grass pastures work, they have been working for thousands of years. But times they are a’changing (insert a “back in my day…” quote here). The human population (no more we’s, it’s getting serious now) has swelled into the billions (8,286,120,266 at the time of writing), requiring massive agricultural landscape expansion to sustain us.

There is no better example of this than where I live; the Canterbury Plains of Aotearoa New Zealand. Less than 0.5% of Canterbury Plains’ native bushland has survived the ever-expanding agricultural and residential landscapes. This is where we run into our big pinch of ecology – if we were to put the native plants and animals back, where would they go?

The answer – into polka dots, patches and pinstripes.

I’ll explain what the patterns are about, as I know you’ve been waiting patiently. They are landscape design patterns of native woody plants within an agricultural livestock pastural setting. They are the answer – cohabitation of native habitats and productive farming, all within one landscape.

Lincoln University‘s multi-disciplinary researchers, James Eggers, Shannon Davis, Crile Doscher and Pablo Gregorini, are the large brains behind this pioneering conceptual design. In their study, they list ideal native woody plant species that can be used to both enhance livestock welfare and restore bush habitats for native birds.

Now we’re cooking with renewable energy, and we’re baking three cakes in one pan – through increasing foraging opportunities for livestock, providing shade and shelter for these livestock, and establishing native bird sanctuaries. Wow!

Picture this – you’re a farmer and this is your Canterbury Plains farm. Nice, right! You have multiple grass paddocks where you graze sheep and cattle. In reality, this is Lincoln University’s Ashley Dene Farm which was used as a case study for this research, but in this virtual Blog, it’s yours.

Figure 1: Aerial view of Ashley Dene Farm Image © 2023 by J. Eggers et. al. Licensee MDPI, Basel, Switzerland. CC-BY 4.0

Let’s say you want to increase foraging opportunities for your livestock. You know that foraging woody vegetation has long been recognised as beneficial. Woody vegetation tolerates poor soils and weather conditions. It provides a range of nutrients and medicinal properties for optimal livestock health. Also, a diversity of forage enhances livestock consumption and can lengthen the grazing season. Finally, foraging allows livestock to exhibit natural browsing behaviour, thereby boosting welfare.

Lucky for you, thanks to this research, we have a list of optimal foraging native shrubs and small trees (shorter plants for livestock access) selected for palatability, tolerance for browsing and growth rate. Now for the fun part – how to arrange these plants. We have three patterns…

Polka dots (or patches): vary in size and are placed within pastures. The central area is fenced to prevent overgrazing and to accommodate natural seedling regeneration.

Figure 2: Polkadots. Image © 2023 by J. Eggers et. al. Licensee MDPI, Basel, Switzerland. CC-BY 4.0

Spreading: balances access to forage, preventing over browsing through the use of a central fenced off strip. It preserves maximal grazing pasture by running along pre-existing fence lines. Livestock can be moved between paddocks/sides of the spreading forage to allow for regeneration on one side whilst the other is browsed.

Figure 3: Spreading. Image © 2023 by J. Eggers et. al. Licensee MDPI, Basel, Switzerland. CC-BY 4.0

Pinstripes (or just stripes): maximises foraging opportunities and is compatible with farming that uses large machinery. The stripes are within a single paddock, placed 40 m apart for optimal browsing, and temporary fencing is used to designate/restrict feeding areas.

Figure 4: Stripes. Image © 2023 by J. Eggers et. al. Licensee MDPI, Basel, Switzerland. CC-BY 4.0

Back to your hypothetical farm, you now have an amazing amount of native forage for your livestock. However, with your farm being on the Canterbury Plains, it is constantly hounded by northeasterly, hot northwesterly, and cold southwesterly winds. Your animals need shelter. Shade and shelter for livestock reduces heat/cold stress, excess moisture loss, improves animal wellbeing, increases feed intake and lamb survival rate.

Here is a native solution with multiple benefits, no more English hedgerows that provide little to no food for wildlife. Native trees and dense shrubs are selected for their height, shade, canopy, and provision of shelter. Unlike the foraging designs, these shelter patterns are fully fenced off to allow for optimal plant growth without the pressure of grazing.

Straight shelter: a pretty straight-forward design (see what I did there) providing shelter in areas of limited space.

Figure 5: Straight shelter. Image © 2023 by J. Eggers et. al. Licensee MDPI, Basel, Switzerland. CC-BY 4.0

Meandering shelter: similar to the straight design, however, with a greater width to act as a wildlife corridor and habitat.

Figure 6: Meandering shelter. Image © 2023 by J. Eggers et. al. Licensee MDPI, Basel, Switzerland. CC-BY 4.0

In-paddock shade trees: taller trees are placed through paddocks, in groups or individually, to provide shade. There is no underplanting to allow for a cooling breeze.

Figure 7: In-paddock shade trees. Image © 2023 by J. Eggers et. al. Licensee MDPI, Basel, Switzerland. CC-BY 4.0

Ah, that’s nice. Now your sheep and cattle are well fed and comfortable. The productive capacity of your farm is in order. But, you also care deeply about native wildlife and want to do everything you can to protect them (but not with a loss of productivity for your farm). Is this possible? Well, let’s see…

James and his team designed native bird bush habitats around a wetland corridor, an area of pre-existing mature trees, and a densely planted area. Densely planting native bushland are better at dealing with edge effects, reducing the distance that light and sound pollution can travel into the patch, and increasing bushland’s suitability for sensitive birds (like kererū). The mature trees act as nurse species for the native seedlings and the wetlands will breed waterborne insects – an additional snack for many bird species.

Whilst the forage and shelter plantings were determined by the needs and landscape of the farm, placement of bush habitats required consideration of the wider landscape. Preference was given to the native bird habitat locations as they had specific requirements. Native bird habitats must connect to a wider established ecological network for birds to be able to travel to the site (within 5-25km distance dependent on the bird species). Amazingly, native bird abundance can almost quadruple with the addition of restored bushland to agricultural landscapes. This research identified ultimate native plants that provide bird food sources and nesting sites.

Figure 8: A comparison of your farm with and without native woody vegetation additions in a combination of design patterns for livestock forage, shade and shelter and native bird bush habitats. Image © 2023 by J. Eggers et. al. Licensee MDPI, Basel, Switzerland. CC-BY 4.0

So now you have an ideal farm! It balances livestock productivity and native bird habitats through adding an abundance and variety of native plants (an increase of 30% woody vegetation in the case study farm). And yes, there may be a reduction in the grazing land area, but, this is offset by increased forage vegetation, combined with fallen organic matter improving soil health and productivity. The addition of native bird habitats will likely have little impact on farming operations.

Forage patterns can be integrated into shelter patterns to maximise land use for grazing. Likewise, forage plantings can be placed next to bush habitats to create multifunctional areas. Shelter and forage plantings can complement the bush habitats, by acting as wildlife corridors, edge habitats, and increase plant species diversity. Your imagination is the limit when it comes to combining and implementing the design patterns, however, site specifications, soil types, climate conditions, livestock density, paddock use, and wildlife reserve proximity need to be considered… so maybe your imagination isn’t the limit, as every farming landscape has different specifications.

We are achieving an agricultural ecological landscape in one location, with broader ecosystem benefits. Restoring and integrating native habitats into farming practice can encourage others to follow, and together we can support the revival of native birds to our currently fragmented landscape. This research kneads together two strong cultural identities of Aotearoa New Zealand – its rich farming history and outstanding natural biodiversity – fortifying and concentrating both.

As these Patches, Polka dots, and Pinstripes do sound like a Dr. Seuss story, it is only appropriate to end with,

“Unless someone like you cares a whole awful lot,

nothing is going to get better.

It’s not.” – Dr. Seuss’ The Lorax

So thanks to all of you reading this, farmers or not, I know that you care a whole awful lot.

This article was prepared by Klara Royster, Master of International Nature Conservation student, for an assignment in ECOL608 Research Methods in Ecology.

Reference Research Journal Article: Eggers, J., Davis, S., Doscher, C., Gregorini, P. (2023). Enhancing Multifunctionality in Agricultural Landscapes with Native Woody Vegetation. Sustainability Journal, 15, 11295.

August 11, 2026
Our plants are not being poisoned by 1080 possum baits

I’ll admit, before taking the 16 hour flight from Arizona to Christchurch, I didn’t know much about New Zealand besides ‘What We Do in the Shadows’, Karl Urban, and affordable yarn. I was especially excited to get my hands on possum yarn.

Possum yarn is coveted by the knitting community for its lightweightedness and warmth, only surpassed by the fur of arctic foxes and polar bears. And let me say that I absolutely think that the possum yarn was worth every dollar. With just 400 meters (one skein/ball) I was able to knit up a cabled hat, mittens, and still have some left over for some ankle length socks!

The feeling of possum yarn is incredibly soft and the natural brown color of the possum fur mixed with merino sheep wool makes for a more muted (in a good way) color palette. However, I recognise that the brushtail possum is a prevalent pest in New Zealand; so much so that drastic measures like Compound 1080 poison baits have been used since the mid-1950’s to control this introduced species.

Common Brushtail Possum by Catching The Eye, 2014 (CC BY-NC)

Compound 1080 for pest control in New Zealand

To put it simply, sodium fluoroacetate (AKA Compound 1080) is a vertebrate pesticide used to control introduced mammal species, such as rats, mice, feral cats, and possums. Without Compound 1080, these species decimate the population of endemic plants and animals only found in New Zealand. The compound is dispersed by aircraft(i.e. helicopters or fixed-wing planes) in either a carrot or cereal bait. 

According to my professors, everyone has an opinion on the use of 1080. While Compound 1080 is great when it works, there are concerns from both the general public and Māori communities. From a public perspective, 1080 does have the real danger of killing people’s cats and dogs if accidentally ingested. As a pet owner myself, this is especially scary because my cat and dog would likely eat the bait before I’d have a chance to recognise what it was. Additionally, the Māori community has concerns about Compound 1080 leaching into the soil and then poisoning plants used for food or medicinal purposes. 

Back in September 2003, a cooperative effort was made in New Zealand by the Ecology Department at Lincoln University, Landscape Research, Lake Waikaremoana Hapu Restoration Trust, and the Tūhoe Tuawhenua Trust to determine if Compound 1080 negatively impacts plant species used by the Ngāi Tūhoe Māori and if not, how to get this information spread among the iwi. To achieve this, a study was conducted on wild-growing pikopiko (AKA hen and chicken fern) and Karamuramu plants in State Forest Block 100, just south of Lake Waikaremoana.

Hen and Chickens Fern – Asplenium bulbiferum by John B, 2016 (CC BY-NC)

Ten individuals of each plant species were chosen and placed underneath wire mesh as protection against herbivory. Of the twenty plants, 3 of each species were exposed to a single Whanganui No. 7 cereal 1080 bait. Samples were taken from the plants throughout the study (days 0, 3, 7, 14, 28, and 56) as well as bait samples at the very beginning and end, to test for potential shift in potency over time.

More than 99% of the 1080 had disappeared from the baits by day 56 and all but one plant sample had no remaining amounts of 1080 within their systems. Of the twenty plants sampled, only one Karamuramu plant retained the toxin; and that was at most 5 parts per billion (ppb) and was completely gone by day 28. 

Foodweb database

Karamuramu plant – Coprosma robusta by eyemac23, 2025 (CC BY-NC)

I don’t know about you, but I’ve never been a huge fan of reading scientific articles. They’re always confusing, too long, and to be honest, a bit dry. Sometimes I wish I could, instead, just scroll through a presentation with all the information presented short and sweetly.

Oh wait, this article did just that and made up not only a comprehensive food web on the interactions of the forest environment with 1080, but also added hyperlinks to it that opens a PowerPoint!(Note: the article did not include the link to the original PowerPoint, only an image of one of the slides.) Each PowerPoint slide focuses on a single plant or animal species impacted by 1080, the intensity of 1080 impact, and additional reference sources. It’s easy to digest and leaves room for more research if one wanted to do so. 

Concerns from the Māori community

In conclusion, I get why using Compound 1080 is necessary against invasive species, like the brushtail possum and it will likely never impact me on a personal level unless it somehow leaches into a batch of yarn or something. However, I also can understand why the Ngāi Tūhoe Māori tribe are still hesitant as 1080 is still a toxin and we may not know the full impacts. While the decision to use Compound 1080 in the Te Urewera area is complicated, in 2016 those from the Ngāi Tūhoe tribe largely oppose aerial drops since it cannot be controlled.

Final thoughts

I think it’s important to note that for a 70 kg person to actually die from consuming 1080 that has remained in a Karamuramu plant, (and even in this example the probability of death is only 50%), they would have to eat 28 tons (28,000 kg) of the stuff. And that’s also if the plant is eaten raw, normally it’s boiled in water as a tea and diluted even more. Personally, after reading this I wouldn’t be too worried about Compound 1080 in my plants but I will still leave the risk assessment up to those in the Māori community on an individual level. 

For now, I will continue to enjoy knitting with the luxurious possum yarn until the pests are eradicated from New Zealand once and for all.

This article was prepared by Master of International Nature Conservation student Marie Frackiewicz as part of the ECOL608 Research Methods in Ecology course.

OGILVIE, S.C., ATARIA, J.M., WAIWAI, J., DOHERTY, J., MILLER, A., ROSS, J.G. and EASON, C.T. (2010), Vertebrate pesticide risk assessment by indigenous communities in New Zealand. Integrative Zoology, 5: 37-43. https://doi.org/10.1111/j.1749-4877.2010.00190.x 

November 19, 2025
Forests from grass: natural regeneration of woody vegetation on hill farms

If you’ve spent any amount of time travelling around Aotearoa New Zealand, you will have noticed the abysmal amount of forest trees in much of our country. Pre-human New Zealand was almost entirely covered in indigenous forest. You may have heard that statement before, but let’s just appreciate it for a second. 96% of the North Island and 72% of the South used to be lush with native podocarps, hardwoods, broadleaves, and beech trees.

Over the course of our relatively short history, we eventually destroyed a massive 14 million hectares of indigenous forest to make way for housing, industry, and farms. We were particularly keen on clearing drier and more arable regions like Canterbury and Central Otago, which have lost nearly 90% of their original vegetation.

By 2002, only a quarter of that indigenous vegetation remained. Don’t get me wrong, I like living here, that people can make money here, and I like eating fresh food. But, damn, I also like breathing oxygen…

Looking around Akaroa Harbour, the hills have mostly been cleared of indigenous vegetation at one point or another since human arrival to the area (own photos).

In all seriousness, native trees play much more important roles than that. Native forests can protect us from wildfires, help us avoid droughts, increase soil, water, and air quality, reduce erosion, and provide habitat for unique native species that do their part in making all of these ecosystem services available to us. As well as that, the land itself, the rugged forests, and activities like hiking through native trees forms part of our cultural identity, not to mention a reasonable chunk of our tourism industry.

What’s more, our native forests store an incredible amount of carbon – an estimated 1.7 billion tonnes.

In order for New Zealand to transition to a low-emissions economy and reach its climate change targets by 2050, we need to plant a lot more trees …up to 2.8 million hectares’ worth. The Productivity Commission suggested that most of this land could come from marginal farmland. As it turns out, there is an estimated 2.8 million hectares’ worth of suitable hill country that could be converted to forest. Hill country is essentially steep slopes at higher altitudes. It’s referred to as ‘marginal’ farmland because the economic gains are quite low compared to other landscapes. Steeper gradients are prone to erosion, and high-altitude climates don’t always lend themselves to agricultural productivity.

Steep slopes at high altitudes are key characteristics of New Zealand’s hill country (own photo).

So, how do we go about converting hill country farmland into a thriving native forest? Pedley, McWilliam, and Doscher discuss the factors that we must take into account.

Hill country revegetation projects are tough for the same reasons as hill country farming is tough, there are costs associated with buying nursery-raised seedlings and then planting on difficult terrain. As Pedley and colleagues suggest, the cheaper alternative is to simply let nature do its thing. Allowing forests to regenerate naturally is a form of passive or minimal interference management (MIM). Landowners, especially farmers, are among the most well-placed in the country to protect and expand our country’s native forest cover, and MIM is an attractive solution to the costs.

When it comes to revegetating farmland, Pedley and colleagues point out two major considerations.

One difficulty is that pasture grasses often suppress native seeds from establishing, so it’s important to help the seeds get a head start. The easiest way to do this is with nurse crops, which shade out the grass, shelter the natives, and protect them from browsers (particularly possums and ungulates, like deer and goats). Nurse crops can be exotic or indigenous shrubs and trees, and even existing weeds, like gorse, can be made useful. This is because NZ natives generally prefer to start out in the shade, eventually growing tall enough to overgrow the nurse crops.

Next is the issue of livestock that can be detrimental to natural regeneration. It does depend on which livestock species you have and which tree species are regenerating. Cattle can be extremely destructive to new plants, paddocks, and pre-existing vegetation. Sheep, on the other hand, don’t really seem to make a difference, though they tend to snack on broadleaved species that are a necessity for a healthy forest ecosystem.

Cattle should be reduced or excluded entirely from a revegetating area. Sheep can be reduced or excluded until there are a good amount of established seedlings, which usually aren’t as palatable to them. Just don’t forget to also keep out those pesky possums and unwelcome ungulates.

Cattle can be destructive to pastures and newly planted vegetation (“Cow Path to the Forest” by Tristan Schmurr, CC BY 2.0)

The most important part of natural regeneration is that the seeds have to come from somewhere. This means that the existing native vegetation on your property is one of your most important assets. This is the ‘passive’ part of the process and the money-saver, because you won’t need to buy seeds or establish nurse crops – the trees have got it covered. The native trees will shade out the grass in the space directly adjacent, enabling the seeds to gain a foothold and gradually expand the forest. Fencing off this area, or the paddock the trees are in, is enough to start the process.

A fair warning though: promoting natural regeneration with MIM can be slow, particularly through grazed pasture. Pedley and colleagues detected an annual regeneration rate of 0.2% from 2003 to 2019 at a southern Banks Peninsula station. At a time when New Zealand desperately needs to plant more trees, MIM is one of the ways landowners with limited resources can contribute, though more active management strategies will speed up the process. For example, consider pest management to exclude browsers (e.g. trapping, hunting, or fencing) and supplementary planting, especially if your remnant vegetation is limited to a few individual trees or species.

Policy and the barriers to getting involved

Finally, especially for those of us in the political and conservation sectors, I think it is our responsibility to encourage native tree planting among landowners, while understanding their barriers to doing so.

The most obvious barrier in converting farmland to forestry is the loss of income, however minor it is. Landowners meeting certain land and forest requirements may be eligible to participate in the New Zealand Emissions Trading Scheme (NZ ETS). With one hectare of ten-year-old forest, you might earn anything from 8-24 NZU per year, depending on the tree species. If sold at $58 per NZU, that’s an annual income of $464-$1392 per year – for essentially leaving the land alone. These figures grow as the forest matures, and with better policy, these figures could grow even more.

Our policies currently favour exotics over natives, and plantations over constantly-regenerating forest. Not all models consider the amount of carbon stored in the forest understory, which is much denser and richer in a native forest compared to a pine forest. New evidence shows that native ecosystems store much more carbon than previously thought, and over a much greater period of time than pine species.

Mature beech forest understory (own photo)

Mature pine forest understory (“Mount Thomas pines” by Jon Sullivan, CC BY-NC 2.0)

Another barrier to entry is our individualistic culture around climate change action. Many sheep and beef farmers report that pro-biodiversity action is not necessarily about a lack of resources, but the belief that their actions don’t benefit their own farms, or that they aren’t helpful in the bigger picture. It’s important that we change this mindset, because 89% of New Zealand’s emissions are created by our primary industries.

MIM cuts costs, but adding more trees to your property and protecting them not only benefits the landowner and the immediate environment, but also the rest of the country. It benefits the natural resources on which we all rely, stabilises the landscape, and protects us from fires and droughts. Natural regeneration of natives results in improved biodiversity outcomes, with higher richness and abundance of plants, birds and invertebrates, which not only make all of this possible, but also make the system sustainable. This means that landowners can cut costs in the long run by working with nature, using its natural characteristics and processes to their advantage.

In any case, growing a forest on a farm is not an overnight process

It requires a lot of patience, but those who are able to encourage native regrowth are safeguarding the country’s biodiversity and resources for all of us, and contributing to our sustainability. Native forests hold a much more strategic long-term position in the bid to plant more trees, and hill country farmers are the most well-placed to allow their regeneration.

Perhaps one day we will have the privilege of living and working alongside the lush and bustling forests that once supported us, as we learn to support them.

Mature beech forest (own photo).

This article was prepared by Master of Science student Sarah Gabites as part of the ECOL608 Research Methods in Ecology course.

Based on the article by Pedley, D., McWilliam, W. and Doscher, C. (2023). Forests from the grass: natural regeneration of woody vegetation in temperate marginal hill farmland under minimum interference management. Restoration Ecology 31:3. https://doi.org/10.1111/rec.13852

September 1, 2025
The Magical World of Grass and Clover

*Disclaimer: This article contains Harry Potter references

After four years of living and studying together, you would think you know someone pretty well. Alas, last week it turned out one of my flat mates had never seen (or read) Harry Potter… shocked, heartbroken, and outraged – the only way to solve this flat feud was to start from the beginning and watch Harry Potter and the Philosopher’s Stone.

The next day, it was back to study. However, I couldn’t get the wizarding world out of my mind, especially knowing that the second movie, the Chamber of Secrets, was scheduled for that night. It got me thinking. Every hero has a sidekick. Batman and Robin, Frodo and Sam, Harry and Ron. But what if these iconic heroes don’t only exist in the worlds of Gotham City, Middle-earth, or Hogwarts. What if the heroes on this earth have sidekicks too?

Legumes (like clovers) are heroes. Destined for greatness and capable of incredible things, they can capture nitrogen (N) from the atmosphere and convert it into ammonia, a biological form of nitrogen that fuels the ecosystem. Farmers often incorporate clovers into their pastures to provide nitrogen into the system. Because of their magic-like nitrogen capturing abilities, clovers boost the growth of neighbouring grasses and create an increase in food quality and quantity for grazing animals.

White Clover (Trifolium repens). CC BY 2.0. Harry Rose

It is generally understood that this is a one-way relationship, meaning clovers are humble heroes that provide N to the grasses and plants surrounding them. However, through my muggle research, I came across a recent study titled “Grasses procure key soil nutrients for clovers” by PhD student Zhang Wei.

Could it be? A sidekick to our green three-leaf (sometimes four if you’re lucky) hero?

Wei and his team questioned whether we properly understand the relationship between clovers and grasses. For the purpose of this article, let’s think of clovers and grasses as characters to understand better their relationship and how they work together.

Perennial Ryegrass (Lolium perenne). CC BY-SA 4.0. Michel Langeveld

Different plant species have various magic-like abilities to acquire nutrients. Grasses, for example, are potion makers and can release chemical substances into the soil to make elements such as iron (Fe), zinc (Zn), copper (Cu), and manganese(Mn) more available in the soil. Other plants call on the Room of Requirement and collaborate with fungi to increase access to nutrients through the fungal networks. Like how the Room of Requirement appears for those who need it most, fungi create symbiotic relationships with plants, enabling more nutrients to ‘appear’ and become more accessible in the soil. And clovers, as you now know, use their spellwork to fix atmospheric nitrogen (N).

However, just like the spell “Wing-gar-dium Levi-o-sa” requires a certain pronunciation, N fixation requires a certain nutrient – phosphorus. Phosphorus is a nutrient constantly in high demand for clovers due to N fixation being such a taxing process.

Zhang Wei and his research team carried out experiments to better understand how grasses influence the nutrient availability for clovers. Clovers and grasses were grown separately in individual pots, much like Harry living alone in the cupboard under the stairs. They were also grown together in shared pots, similar to Harry and Ron bunking together at Hogwarts. Measurements were then taken from the soil and leaves in all the pots to understand how the clovers and grasses influence each other’s growth.

The researchers found that grasses promoted the growth of clovers when grown together. This was evident when higher amounts of nutrients such as nitrogen (N), phosphorus (P), potassium (K), and sulphur (S) were found in clover leaves growing with grasses compared to clovers that grew alone. Grasses give clovers a boost in accessing essential nutrients, much like how Ron supports Harry, offering the strength and loyalty he needs to face He-Who-Must-Not-Be-Named.

Mixed sward of White Clover (Trifolium repens) and pasture grasses growing together. Nicole Parnell. 2025.

Additionally, more biomass was achieved when both clovers and grasses were grown together compared to when they were grown apart. How would Harry have gotten through his years at Hogwarts without his friends by his side? They achieve more when they work together. By sharing their resources, the plants could increase their biomass, which boosts livestock feed while lowering fertiliser demand.

The muggle authors acknowledge that more research is needed to fully understand the complexities of how nutrients move through the soil in plant communities like this, especially under field conditions. In 2023, Zhang Wei and his supervisors took the study into the field and, once again, saw enhanced legume growth when grown alongside a diverse range of pasture grass species. Think of Harry’s resilience and leadership, Ron’s loyalty and humour, and Hermione’s intelligence and discipline, all of which work together to create a strong, unbeatable partnership. Similarly, there is an enhancement of nutrient uptake in diverse pastures with legumes (including native legumes) and grasses. This suggests a possible reduction in fertiliser requirements in pastures with increased plant diversity.

A study that referenced Zhang Wei’s work similarly found that plant mixtures with various legume and grass species reduced intraspecific competition, a term that explains competition between individuals of the same species (think Gryffindor vs Slytherin). This means that the growth and productivity of both legumes and grasses were further enhanced when grown together.

Zhang Wei’s PhD study provided further insights into the flow of nutrients within plant communities, demonstrating that grasses also play a vital role in nutrient availability and enhancement. This study builds on the argument that pasture diversity can reduce reliance on artificial fertilisers and promote sustainable farming methods. These methods can increase the ecosystem’s stability, making it more resilient to disturbances such as droughts and/or floods. Like any partnership, growing together makes them stronger.

That’s where the magic happens.

This article was prepared by Master of Science student Nicole Parnell as part of the ECOL608 Research Methods in Ecology course.

July 10, 2025
Why don’t restored streams bounce back?

In New Zealand, many would agree that fresh water is one of our most loved natural resources. We drink it, we swim in it, we use it to farm and to make a living, we even use it to generate our power! Unfortunately, especially in Canterbury after some major earthquakes, many of our streams and rivers are struggling. They look something like this:

Kowhai River, Kaikōura. From Environment Canterbury, ND.

In stream restoration, we want to return the features of a stream back to their original state, before things like urban development or introduced species affected the quality. This includes adding native plants, allowing fish to make their way out to sea or further upstream, and making sure farm animals can’t walk straight into the stream. All of these things and more can help us to make healthier waterways.

It does not always go to plan, with some hardy introduced species putting a spanner in the works and refusing to co-operate with careful scientific methods. Imagine a beautiful stream that’s been through tough times—pollution, habitat destruction, earthquakes you name it. People step in – scientists, council members, developers, maybe the general public, and they work hard to restore it, but here’s the kicker: sometimes, things just don’t bounce back like they should. Why? That’s exactly what a recent study by Issie Barrett and her team set out to uncover.

To understand why streams struggle to recover even after the most thorough restoration efforts, we need to understand a few key factors.

1. Species Interactions: In a healthy stream, different plants and animals interact in specific ways, such as some animals eating others or different plants competing for space. When a stream is damaged and then restored, these interactions might not work the same way anymore. This can make it harder for the original species to come back and thrive.

A particular species of snail, the New Zealand mud snail (P. antipodarum) is particularly good at living in these degraded streams, they thrive under pressure and limited food sources. These snails are perfect species to take over a degraded environment and reduce the recovery ability! So even when original species are introduced, such as the mayfly, the same food source now has double the competition, meaning a negative reaction – that habitat can’t provide that much food even in a restored state.

New Zealand mud snail Potamopyrgus antipodarum. Photo Credit Michal Maňas 2014

2. Negative Resistance: This is a big concept, which in essence means that even when the physical conditions of a stream improve (like cleaning up pollution or adding new habitats), the plants and animals in the stream don’t always come back as quickly or fully as hoped.

During the stream’s degradation years, new species like the mud snails might move in – kind of like uninvited guests crashing a party. Even after things are cleaned up, these newbies can stick around and hog resources, making it harder for the original gang to make a comeback. This is what they call “negative resistance.” This can happen because the habitat is too degraded for the ideal species to thrive even if they did before.

3. Resilience Mechanisms: This means the ability of a system to absorb and adapt to change, ultimately returning to the restored ideal. This is where our negative resistance comes into play. If the species or the system is already not functioning as it should, we are going to have a hard time creating a resilient system that can adapt to a changing environment and overcome any future issues.

For example, a high level of nitrogen could change the make-up of the riverbed so drastically that a species sensitive to nitrates may never repopulate that system. Understanding the relationship between negative resistance and resilience is important for predicting and enhancing any successful restoration efforts.

What can we do?

Look at the Big Picture: When restoring a stream, it’s not just about fixing what we can see. We need to think about how all the different plants and animals interact with each other. This includes what nutrients are in the water and what microscopic invertebrates might be living in that water.

Keep Checking In: It’s important to keep watching restored streams over time to make sure they’re getting better and to fix any problems that come up. If we don’t see an improvement in 5 or 10 years, there must be something else we can do.

Be Flexible: Sometimes, we might need to change our restoration plans based on what we learn from watching how the stream responds. As scientists we have to be okay with admitting our first idea didn’t work, and then be willing to help come up with a better solution for the future.

Vegetated drain in Canterbury with optimum riparian planting. Photo credit Jon Sullivan, ND.

Why it matters

Overall, there are some pretty complex systems that are at play in stream restoration projects. It is not as simple as putting in some better plants and some bigger, cooler rocks and hoping it will all work out in 10 years. By paying attention to how plants, animals, and the environment all work together, perhaps we can work towards a deeper understanding of the best ways to help our New Zealand streams thrive for many more generations to come.

I think it would be pretty cool to keep swimming in our rivers and looking for fish in the summer, but next time you go to your local river, have a look and see what plants and other animals would really love to keep living there too.

This article was prepared by Postgraduate Diploma in Environmental Managemen t student Tayla Cross as part of the ECOL608 Research Methods in Ecology course.

September 16, 2024
Microbes matter in breaking down nitrogen in dairy pastures

Our eyes are captivated by the breathtaking diversity of the living world, where billions of plants and animals enchant us with their variety and richness, thriving above ground or in water. But we often overlook the organisms beneath our feet, in the hidden world of soil, where an equally mesmerizing realm teems with life.

E. R. Ingham: “Just one spoonful of soil can be home to millions of microbes“- the astonishing dynamic of these tiny, unseen organisms would blow our minds, if we only knew their story.

I am fascinated by the biodiversity of the massive underground community. Countless small living things, such as microbes, insects, and earthworms, are tirelessly at work, busily breaking down organic matter and waste like leaf litter, faeces, and other dead organisms.

Soil sample under the microscope, Image credit: © William Edge
from Dreamstime.com CC BY-NC 2.0

These organisms play fundamental roles in decomposition and also contribute to unlocking essential nutrients, like nitrogen and phosphorus, making these nutrients more available to plants. However, some microbial species can degrade useful substances, primarily affecting the cropping system and leading to lower crop yields in agriculture.

In New Zealand, our grazing pastures face a significant challenge of soil microbes depleting essential nitrogen (N) in the soil. The NZ dairy industry has a substantial economic impact. A report by Sense Partners highlights that DairyNZ accounted for a quarter of New Zealand’s total export earnings (26 million) in 2023, making it a crucial contributor to national prosperity. For dairy farmers, “grass is green gold” because high-quality pasture is the key to their success, supporting healthy and productive livestock.

Nitrogen boosts pasture supply, especially when N fertilizer is applied in mid to late spring. In most regions, this application results in an optimal and reliable grass response of around 10 to 15 kg DM/kg N. Why the need to apply synthetic fertiliser when nitrogen is abundant in the atmosphere, which contains 78% nitrogen. The catch is that atmospheric nitrogen is not directly available to most plants (except for legumes) due to its highly stable form (N₂).

Given the necessity of nitrogen fertilisers in grazing pasture systems, a go-to choice is urea. It’s most cost-effective and the most widely applied nitrogen fertiliser in NZ dairy pastures. The scale of its usage is staggering, with over 400,000 tonnes of urea being used annually in dairy farm systems since 2013.

Two Cows by Martin Gommel | Flickr | CC BY-NC 2.0

There is a downside. Ammonia-oxidizing soil microbes release an enzyme called urease that can break down over 80-90% of urea fertiliser when soil moisture is high. This leads to significant economic losses for farmers and contributes to environmental pollution through nitrate leaching.

Note: Urea is the substance of solid nitrogen fertilizer, while urease is an enzyme found in plant tissues, fungi, bacteria, and some invertebrates, but not in animals.

Dr. Hossein Alizadeh, a senior researcher in the Department of Agricultural Sciences at Lincoln University, leads a team focused on addressing the problem of nitrogen loss in soil. They have identified key culprits of rapid nitrogen loss in the soil – urease-producing microbes.

By understanding these microbes better, the team can develop solutions to enhance the uptake of nitrogen nutrients by pastures and reduce greenhouse gas emissions. This is crucial because nitrogen from livestock urine and agricultural fertilisers converts to nitrous oxide (N₂O), contributing to about one-sixth of New Zealand’s CO₂ equivalent greenhouse gas emissions.

To detect the nationwide urea degradation levels in dairy farm pastures, Dr. Alizadeh and his research team collected soil samples from various regions, including Auckland, Canterbury, Manawatu, Marlborough, Nelson, Otago, Taranaki, Waikato, Wairarapa, and the West Coast. The sampled pastures primarily consisted of ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.). Some grazing lands were relatively young, only nine months old, while others had 60 years of usage.

To determine whether urease-producing microbes are present in different soil samples, researchers measured ammonium production. Urease breaks down urea and nitrogen in the soil converts to ammonia gas (NH₃) and nitrate (NO₃-) leaching. In the lab, if the urease producer actively breaks down urea and releases ammonia, the Petri dish with cultured microbes will show a pink colour (see Figure below). Additionally, to identify microbial bacteria and fungi, they applied the PCR (polymerase chain reaction) technique, morphological identification methods.

Urease detection medium for isolation of soil urease producing microorganisms (left) and a purified urease (right). Own work CC BY-NC 2.0

Hossein found some novel microbial species, such as Pochonia bulbillosa, Mariannaea elegans, and Gliomastixsp., which were reported for the first time for their urease production. The study also revealed variations in urease activity among the isolates and a diverse microbial community composition across different locations. For instance, in Nelson, bacteria were the dominant urease producers in the soil, while in Oxford, it was fungi, marking a significant discovery in soil microbiology.

The groundbreaking research by Dr. Hossein and his team on identifying urease-producing microbes not only provides fundamental knowledge but also opens up possibilities for practical applications. The findings suggest the potential of manipulating these microbial populations in soil to reduce urease activity, a concept that is being further explored in the N-Bio Boost program led by Professor John Hampton of Seed Technology at Lincoln University. This project, funded by the New Zealand government and the fertilizer co-op Ravensdown, aims to harness a naturally occurring fungal species in the soil to enhance the nitrogen efficiency of plants, promising both environmental and economic benefits for New Zealand.

So next time you are walking on pasture, pause and appreciate the busy world that is found under your feet!

This article was prepared by Master of Pest Management postgraduate student Danyu Li as part of the ECOL608 Research Methods in Ecology course.

Alizadeh, H., Kandula, D. R. W., Hampton, J. G., Stewart, A., Leung, D. W. M., Edwards, Y., & Smith, C. (2017). Urease producing microorganisms under dairy pasture management in soils across New Zealand. Geoderma Regional, 11, 78–85. https://doi.org/10.1016/j.geodrs.2017.10.003

September 5, 2024