EcoLincNZ

Category: Soil

  • The Magical World of Grass and Clover

    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.

  • Enemies with benefits

    Enemies with benefits

    The idea of ‘friends with benefits’ is reasonably widespread and understood. Having good interactions with others will often lead to even more productive outcomes. But what about ‘enemies with benefits’? Are there times where your enemy can give you some positive benefits?

    Invasive species cause ecological harm worldwide, threatening biodiversity, disrupting nutrient cycling and displacing native species. Pacific islands, with their characteristically high rates of endemism, experience out-sized effects from plant invasions (Bellard et al. 2014). In biodiversity hotspots, such as New Zealand, exotic invasive plant species now outnumber native species in area and in number.

    But, how do they do it?

    New Zealand habitats are prone to invasion by exotic plant species. Why is this?

    A study by Lauren Waller and other Lincoln University and University of Canterbury colleagues, published in Journal of Ecology attempts to find some answers. Lauren shows that exotic plants may gain their competitive edge by accumulating enemies in the soil and sharing them with neighbouring native plants, a phenomenon that plant ecologists call pathogen spillover.

    Lauren set up a large mesocosm (self-contained area) experiment. These were areas where new species could be added to a known group of native species in a very manageable process. The health and growth of all plants could be measured and microorganisms both present at the start and brought in on the introduced plants could be identified.

    Lauren expected exotic plants to experience improved growth due to escape from pathogens (leaving the burden of enemies behind when they come to NZ). This assumption comes in large part from two well-known hypotheses, the Enemy Release Hypothesis and the Evolution of Increased Competitive Ability (EICA) Hypothesis. Enemy Release states that exotic plants can gain incredible success when they move to a new location lacking the enemy pressure they experienced in their home range, particularly co-evolved specialist enemies. EICA goes a step further to suggest that if exotic plants can escape enemy pressure in their new range, those plants will have more resources to allocate to growth over defence.

    Somewhat supporting Enemy Release, exotic plants did not appear to suffer much from specialist fungal pathogens. However, exotic plants did associate with generalist pathogens. Also, in support of Enemy Release, exotic plants did not appear to allocate resources to defence. Instead, exotic plants appeared to tolerate generalist pathogen pressure without reducing their growth.

    Native Poa grown in a native versus exotic dominated plot.

    Lauren did not expect to see big impacts by exotic plants on native plants, and boy, did they! Native plants just wasted away when grown with exotic plants. It was very sad to watch. This photo shows an example of a native bunch-grass, grown with all native neighbours (left) or in communities dominated by exotic plants (right).

    What explained the out-sized effect of exotic plants on native plant growth? Our network analysis showed that exotics not only accumulated and tolerated generalist pathogens, but they shared their pathogens with native plants. Native plants did not appear to have the same tolerance for this enemy pressure like the exotic plants did. 

    We started by asking ‘are there times where your enemy can give you some positive benefits?’. It turns out that yes there are times when your enemies can help you a lot. In this case if species cause you problems it will be OK for you if they cause competing species even more problems! With invasive species, your microbial enemies can do you a good turn but taking out the opposition.

    Now that’s a real enemy with benefits!

    Lauren Waller and Adrian Paterson wrote this together (and not as enemies!). They are lecturers in the Department of Pest-management and Conservation.

    Bellard, C., Leclerc, C., Leroy, B., Bakkenes, M., Veloz, S., Thuiller, W., & Courchamp, F. (2014). Vulnerability of biodiversity hotspots to global change. Global Ecology and Biogeography, 23(12), 1376-1386

  • 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

  • Dirty little secrets or tiny heroes of the soil world?

    Dirt was one of my first friends. My earliest days were spent collecting worms from the backyard and trying to convince my parents I hadn’t done any dirt taste testing that day (I probably had, but for purely scientific reasons). I was fascinated by what seemed like an entirely different world in the soil of my parent’s garden. I could find all kinds of goodies from insects to plant roots.

    At university I was introduced to the truly magical world in soil: microbes. Although not visible to the naked eye, the tiny worlds inhabited by fungi, bacteria, viruses, and other unbelievably small things, should not be overlooked. These tiny worlds are called the microbial community and they have important roles in New Zealand forests.

    Photo of soil microbes under a microscope. Photo by Pacific Northwest National Laboratory (CC-BY-NC-SA 2.0)

    A good place to start thinking about microbial communities is our own bodies. Most people have heard of their gut microbiome. The microbes in our digestive system are important for our health from immune function to digestion (especially for dirt tasters). However, some microbes, such as the COVID-19 virus, can make us sick. Soil microbes in forests are not so different.

    Forests are dependent on microbes that cycle nutrients, decompose waster, and aid plants in nutrient uptake. Like humans and the common cold, some soil microbes hurt their associated plants. An example of this is kauri dieback disease, a disease spread by a spore in the soil that attacks tree roots and trunks. This disease hinders the tree’s ability to uptake and transport nutrients, essentially starving and killing the tree. Kauri dieback is incurable and fatal for kauri.

    Tāne Mahuta, the largest surviving kauri. Photo by Jodie Wiltse (Author)

    Kauri dieback is named after the tree it infects, New Zealand’s mighty kauri tree. The Department of Conservation explains that kauri can grow up to 16 m in circumference and live over 2000 years. The legendary status of kauri is clear in the language used to describe them. The largest surviving kauri is called Tāne Mahuta, which means ‘lord of the forest’. If you were to visit Tāne Mahuta today, you would find boot cleaning stations, warning signs, and only be able to view the great tree from a platform. Moreso, entire trails have been shutdown to stop people from spreading soil around kauri. Why?

    A soil microbe, Phytophthora agathidicida, travels under the name of kauri dieback. This microbe cannot be seen with the naked eye but has the power to kill tremendously large kauri trees. In humans, the heroic microbes of our immune system save us when nasty microbes make us sick. Are there unseen heroes hiding in the soil that can help kauri?

    During a PhD project at Lincoln University, Dr. Alexa Byers studied soil microbial communities under kauri to find out. The goal was to identify microbes that suppress kauri dieback and can aid in kauri conservation.

    The first step was to understand how microbial communities under kauri react to kauri dieback disease. Alexa infected kauri seedlings with kauri dieback and looked for changes in the soil microbial community. When humans are attacked by illness causing microbes, our immune system amps up to protect us. When soils were infected, Alexa found bacteria that were involved in disease suppression. This was a promising result suggesting that heroic soil microbes could build up their numbers to fight off kauri dieback.

    Kauri tree bleeding resin, a common symptom of kauri dieback disease. Photo by Onco p53 (CC BY-SA 4.0).

    Next, Alexa looked into how specific strains of bacteria from kauri soil impacted the development of kauri dieback. She identified Paraburkholderia and Penicillium microbes that inhibited the growth of kauri dieback in soils. Paraburkholderia are known to enhance plant growth and fix nitrogen. Penicillium are fungi that can kill or stop growth of other bacteria. We officially have some heroic contenders!

    The battles between heroic microbes and kauri dieback in the soil could determine the fate of the kauri above them. Hopefully, researchers can find a way to rig microbial battles in favour of these unseen heroes. More research is needed to determine their true potential, but these soil microbes could be called to action in the near future.

    The world under kauri is just one example of fascinating soil microbes. Soil microbes have been found to be key for carbon storage, impact the taste of tea, and reduce nitrogen runoff from agriculture, among many other amazing things. This is your reminder to appreciate the little things, even the things so little you cannot see them. Next time you play in a garden or walk through a forest, I hope you take a moment to think about all the tiny microbes working away in the soil to help (or hinder) plants and make the natural world work.

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

    Research Paper: Byers, A.K. (2021). The soil microbiota associated with New Zealand’s kauri (Agathis australis) forests under threat from dieback disease: A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University. Lincoln University. https://hdl.handle.net/10182/13887

  • Farming and biodiversity: what’s on 0.5% of Canterbury Plains?

    Imagine the Canterbury Plains blanketed in tall trees interwoven with small hardwoods. This beautiful, unique landscape is then singed into dry grassland with the arrival of Māori. Continue to imagine European settlers introduce weedy exotics that infest the landscapes, once again modifying the region. Now, picture the current landscape – a monotonous cover of dairy farms. Which of these images would you think is best for our native and endemic species?

    Prior to humans or today? (Think from an insect’s perspective)

    The plains have been a dynamic landscape ever since humans stepped foot in our vulnerable country. They will continue to experience dramatic changes in the future with the ever growing population leading to climate change, urban expansion and agriculture intensification.

    The 1940s saw the commencement of irrigation on the plains so that farmers could have a reliable water source to enhance the production of pasture and crops. Water facilitated the development of dairying from sheep farming, into the landscape we see today. Between 2002 and 2012, the Canterbury herd increased by 115%, accounting for 13.5% of the Aotearoa dairy herd.

    These drastic landscape changes have been detrimental to many of our precious native species by creating unfavourable conditions and habitats, species such as the bellbird (Anthornis melanura) have suffered. Some species, such as paradise shelducks (Tadorna variegata), have exploded in population numbers due to the favorable wet conditions caused from irrigating.

    Within the Canterbury Plains, less than 0.5% of this area is still the original remnant forest. Canterbury has been described as the most biological deprived and most modified environment in Aotearoa due to the intensification of agriculture. However, agriculture is a big portion of the country’s economy, bringing in approximately $10.6 billion (5%) of the country’s Gross Domestic Product (GDP).

    The food and fiber sector are major employer, providing jobs to over 359,000 people. Not only does it feed New Zealanders, it is also a big player in the global food market. in order to come to terms with this environmental dilemma, farms need to incorporate more sustainable agricultural practices, to feed the world and to support biodiversity. Currently through education and awareness this is already becoming a point of discussion.

    There has been a push to introduce native vegetation into farming systems. Several studies have examined the impacts of intensive dairy farming on soil health, vegetation, and life below ground. Farmers are now starting to see the benefits of even simple things, such as planting native vegetation. Such plantings not only positively impact farms, but also our are good for our native species, from small bugs to cryptic skinks and chatty birds.

    Mike Bowie from Lincoln University, like me, grew up on a family farm, and went on to tertiary education in ecology. This brings a helpful perspective to topics around the interaction of agriculture and ecology. It led Bowie to check out the biodiversity in the Bankside dryland remnant that is surrounded by an intensive dairy farming landscape. The Bankside Scientific Reserve in a 2.6-hectare area established in 1969. Mike wanted to know how adjacent agricultural land impacts the soil composition and fauna in this reserve area.

    Aerial photograph of the Bankside Scientific Reserve with kānuka and matagouri dotted throughout. (From Bowie et al., 2015)

    In 1970, an initial vegetation survey was conducted by Molloy within the new reserve. Bowie’s survey in 2015 found that only 31% of plants that Molloy surveyed still remained and that 27 new exotic species were present. The fauna found in the remnant were different to that of the neighbouring agricultural land. Bowie discovered the presence of four native earthworm species along with six exotic species. The number of the exotic worm species decreased with distance into the reserve.

    Bowie and his fellow researchers found 112 specimens of invertebrates, including many beetles as well as a significant native species, the ground weta! Soil pH, nitrate, and phosphate levels were all lower in the reserve compared to the surrounding paddocks.

    These observations highlight the need to retain existing dryland remnants and to establish other reserves throughout the plains. A diverse landscape will support a diverse range of species. I think farmers and the community are now starting to see the value of incorporating native vegetation and agroecological principles into their system, such as mixed species pasture systems.

    We don’t all need to put three hectares away into a reserve. Even small steps, such as planting a row of diverse natives along a fence line or waterway, will make a huge difference, if many farms join in.

    One thing that is highlighted in this study is the need for continued maintenance of restoration and remnant projects. It is not a plant and leave situation (no pun was intended…). Weed and pest control should be continually applied in these areas to prevent exotic weeds and animals from becoming established and smothering and displacing the natives.

    An example of this is in practice Te Ara Kakariki group that is establishing green dots (tiny native areas) from the Southern Alps to Lake Ellesmere/Te Waihora on private properties. This increases the connectivity of native planting, further increasing the power that these small areas can make overall. Animals and invertebrates will be able to spread throughout these dots and over the region.

    Farming has transformed the landscape of the Canterbury Plains. Image from Adrian Paterson.

    Farmers are becoming more aware of sustainable principles through education from organisations such as Te Ara Kakariki, DairyNZ, Landcare trust, and councils. Through education, ecology is becoming more interwoven into their practices. It will be a trick balancing the need for feeding the world and protecting the environment. Ecology is an excellent way to find this balance in agriculture, it can be adapted to any farming system to suit their needs and desires.

    Mike wants to help bridge this gap, not only in this study, but also others that he has conducted throughout his time at Lincoln University. Mike has examined how native plantings encourage native and beneficial invertebrates on Canterbury dairy farms, plus many more. I too believe that ecology and agriculture can work together to create a more sustainable agriculture sector that can efficiently produce food and improve food security, whilst supporting the health of the soil, water and biodiversity.

    This article was prepared by Master of Science postgraduate student Sam Fitzgerald as part of her ECOL608 Research Methods in Ecology course.

    Further reading

    Practical guide for landowner and farmers for landcare

    Improving biodiversity – Beef + lamb

  • Tricks of the underground trade: networking below the vines

    Life in the soil can be a tricky business for plants and microbes. Nutrients are a limited commodity for some, and competitors may swindle and cheat to gain the upper hand. Strategic partnerships are highly sought after enabling exchange of one commodity for another within elaborate networks.

    In a tough economy, well-connected networks promote resilience, sharing of ideas and opportunity to those participating in mutual exchange. However, an efficient network should be an intentional one. Making simple connections is one thing, but choosing the right friends and trade partners is another.

    Although it may not appear that obvious on the surface, most land plants are proficient networkers. Below ground, plants form selective partnerships with microorganisms in the soil to access nutrients, water, and protection from pathogens. Those with strong networks are favoured in times of scarcity and change.

    Fungal mycelium consisting of thread-like hyphae. Photo by Lex vB at Dutch Wikipedia, (CC0 1.0)

    Within soil communities, fungi known as mycorrhizae play a major role in the growth and survival of plants. It is estimated that more than 80% of vascular plants form partnerships with mycorrhizae, an ancient evolutionary network approximately 450 million years old.

    Mycorrhizae are of particular importance in the viticultural industry as grapevines are highly reliant on these partnerships for growth and nutrient uptake influencing grape composition, vine health and occurrence of disease. In fact, grapevines form associations with entire communities of mycorrhizae known as arbuscular mycorrhizal fungi (AMF).

    AMF form close associations within the root tissue of plant hosts through specialized tree-like structures called arbuscules. These allow exchange of mineral nutrients from the soil for carbon fixed by the plant host which is transferred through the extensive hyphal network in the soil. These hyphae form interconnected “superhighways” within the soil, linking neighbouring vines and nearby crops transferring nutrients, such as nitrogen, from one host to another.

    Arbuscule of Rhizophagus irregularis colonising a plant root. Photo by Hector Montero, Flickr (CC BY-SA 2.0)

    AMF are highly diverse and have different effects on nutrient uptake and growth on grapevines. Depending on the situation, AMF can have positive, neutral, or negative effects on plant growth and stress resistance. However, under field conditions, plants are selective in the networks they build. These communities perform a diverse range of functions which collectively contribute to plant health and characteristics. Therefore, investing in the right trade partners is crucial.

    Until recently, the effects of whole AMF communities on grapevines had been largely unexplored. A research project at Lincoln University lead by Dr. Romy Moukarzel sought to understand how AMF different communities influence nutrient uptake and growth of different grapevine rootstocks. 

    In other words, who are the trade partners behind the vines and what is the return from these communities?

    To answer these questions, AMF communities were recovered from the roots of three different grapevine rootstocks across three different vineyards. Each rootstock was inoculated with its own (“home”) community or communities from other rootstocks (“away”) within three different vineyards. Vine growth, nutrient uptake, and chlorophyll levels were measured to find out if different communities had positive or negative effects on the different rootstocks.

    Consistent with previous work, different vineyards and rootstocks had their own unique communities. Growth and nutrient uptake differed depending on the composition of the community and rootstocks responded differently to the same communities. While some species in these communities improved nutrient uptake, others improved growth. In particular, a diverse community with a large representation of AMF of the Glomeraceae family resulted in the greatest increase in grapevine growth.

    In one vineyard, home advantage was also evident with “home” communities having greater increase in vine growth compared to “away” communities. Interestingly, when the amount of each AMF inoculum was equalised, home advantage was no longer observed.

    By changing the community composition, the positive effects on plant growth were reduced.

    New Zealand vineyard. Photo by Jorge Royan (CC BY-SA 3.0)

    Moukarzel and colleagues suggested that altering the composition may have resulted in competition between AMF leading to reduced positive effects on the host. AMF are known to compete for host resources, soil nutrients and colonisation sites. As a result, cooperation, and rivalry between AMF within different communities may have major implications for vine productivity.

    So, what can grapevines teach us about networking?

    Basically, choose your trade partners wisely. Identify friends and adversaries within the network and invest in those relationships with the greatest return.

    As proposed by marketing expert, Porter Gale: the so-called ‘new model’ of networking should focus less on ‘handing out as many business cards as possible’ and more on making connections based on how you want to grow. In other words, efficient networking should focus on investing in specific needs and interests. A well connected network with diverse partners offers wide opportunity and stability if components are co-operative.

    Overall, the findings generated from the study will be an invaluable insight towards leveraging AMF communities to target specific growth and nutrient requirements of grapevines. This is of particular importance to the viticultural industry as the composition of these communities play an important role in determining vine health, yield, nutrition, grape composition, and wine characteristics.

    Featured image: vineyard inter-row by rawpixel.com (CC0 1.0)

    While this study has provided a step towards understanding the communities below the vines, soil is a complex system with a wide range of players and there is much to learn about the orchestration of these networks. There are likely many more tricks of the underground trade to uncover.

    Moukarzel, R., Ridgway, H. J., Waller, L., Guerin-Laguette, A., Cripps-Guazzone, N., & Jones, E. E. (2022). Soil Arbuscular Mycorrhizal Fungal Communities Differentially Affect Growth and Nutrient Uptake by Grapevine Rootstocks. Microbial Ecology. https://doi.org/10.1007/s00248-022-02160-z

    This article was prepared by a Master of Science postgraduate student Malina Hargreaves as part of the ECOL608 Research Methods in Ecology course.

  • Make boysenberries juicy again: the fight against downy mildew

    “Yes, why not!! Hi! I am Boysenberry. I will tell you the whole story, how I fight this destructive fungus. Before delving into the subject, I just want to tell you a little bit more about me.”

    Boysenberries Photo by simplyAutumn 2009 from Flickr

    I am a rich source of micronutrients and have great health benefits. My origin was in California, USA and I was introduced to New Zealand in the early 1940s. New Zealand has become a major producer and exporter of my fruits. The fruits are produced on the second-year canes ‘floricanes‘, whereas the first-year canes that only possess leaves known as ‘primocanes’. Those that grow quickly are known as ‘hurricanes’. Hah – an old joke amongst us boysenberries.

    Propagation of my plants is done either by cutting or tissue culture. Sadly, there is a fungus, Peronospora sparsa, who is my enemy and develops a disease, known as Downy mildew, systemically in tissue cultured plants. It causes huge damage and is will often cause losses of 50%, when I am grown with conventional management methods, to 100 %, when grown organically. It produces symptoms of mycelial growth of fungus, on my leaves in early spring and then later then premature reddening, shriveling, and hardening of my fruits and ultimately, the leaves become dull. That’s why it is sometimes called “Dry berry“.

    Downy Mildew of Boysenberry by Jones and other researchers

    “Unfortunately! I was struggling with this disease when some traditional methods, like removal of leaf litter, rooted ends of primocanes, and root suckers besides the fungicide sprays, that were being used to fight against it, but those were unfortunately not enough to beat it. I know, you are thinking, then how do I overcome this disease?”

    Some scientists from Lincoln University; Anusara Herath Mudiyanselage, Hayley Ridgway, Monika Walter, Marlene Jaspers, and Eirian Jones, came up with some solutions and experimented on me. They thought that heat and fungicides could help treat and stop the growth of the disease.

    To test if these ideas could work, fifteen symptomatic plants (2-year-old) were selected, repotted and cold stored at freezing temperature for 6 weeks to induce dormancy in them. Dormancy is a state where my plants hang tough and save their energy without undergoing their active growth. Dormancy allows my plants survive on their reserved food as they are cut off from the supply of food. The plants were transferred to a greenhouse until 2-3 primocanes developed. Thereafter, the plants were divided into three groups with five plants in each and given three different treatments to each group.

    The first group remained in the greenhouse for a month and was then given a heat treatment by being placed in a growth chamber at 34°C for 4 more weeks. The second group was sprayed twice with phosphoric acid and mancozeb (fungicide), the first spray was given two weeks afterward in greenhouse and second was given two weeks after the first spray. Plus, this group was also heat treated for a month. But the last group was left untreated and remained in the greenhouse for two months.

    Well! The main reason for giving the heat treatment with or without fungicide spray was to check the ability of my propagation material to limit the systemic infection of fungus prior to tissue culture to produce fungus free plants with verification done by PCR.

    Tissue Culture grown plants. Photo by EcoFert Inc. 2010 from Flickr

    After each of the treatments were complete, the plants were ready for the next step: propagation.

    “Do you remember how I am propagated? Yes, the tissue culture.“
    The single-bud stem cuttings from each plant were washed in antimicrobial soap, followed by surface sterilisation and washing in distilled water. These steps were followed in order to make my cuttings free from any contamination and washed with water to remove excessive chemicals/disinfectants. The cuttings were then placed in a liquid medium that made it possible for them to grow and multiply in a sterile condition.

    “You know what!” 125 plants survived in total and were potted after this. The largest group of survivors were from the heat treatment group.

    Cuttings/plants with roots were placed in the greenhouse for a couple of weeks where they were misted to maintain moisture. Afterwards they were shifted to the shade house and were kept for about five months under conditions that favor systemic symptoms. As the cool and wet conditions induce the growth of fungus, these conditions were provided to check the ability of my plants to resist it after given treatments.

    “Are you curious, to know what happened next, then?“

    Polymerase chain reaction machine Photo by USAID Laos 2020 from Flickr

    Twenty-two weeks after potting, all the untreated plants become sick with the disease. However, the other two treatments gave phenomenal results. Only 13 % and 17 % of plants showed visible symptoms, treated with heat only and fungicide + heat, respectively. The seventy-six plants (of 125) from both treatments (Heat and Fungicide + Heat) survived well without any symptoms several weeks after potting.

    Because some plants could have the fungus but not show any signs of infection, the researchers used the modern molecular technique (PCR) to confirm that there were no asymptomatic plants. This test was carried out regularly at certain interval for about a year and all of the tests gave a negative result. Fortunately, only a few plants with heat and fungicide + heat treatments got infected as compared to 100 % infection in untreated ones.

    “Well! this was my story, and now I can say that I can fight against this destructive disease, if I am given heat treatment with or without fungicide. I think you are also curious to know how the heat treatment affect the fungus.“

    The answer is the high temperature. The higher temperature destroys the essential chemical activities and inactivates micro-organisms like viruses. Similarly, this fungus has the nature of only being rely upon the living matter to eat and survive like the viruses. Therefore, the high temperature restricts the growth of fungus into the shoot tips and stops the infection.

    This is the first time that researchers have found a solution to a key challenge in managing dry berry disease. This opens the door to disease free propagation of my plants in nurseries with the uptake of heat treatment and without fear of fungicide resistance to fungi.

    “So now we can all be happicanes!”

    This article was prepared by Master of Science postgraduate student Manjot Kaur as part of the ECOL608 Research Methods in Ecology course.

    Reference: Herath Mudiyanselage AM, Ridgway HJ, Walter M, Jaspers MV, Jones E. 2019. Heat and fungicide treatments reduce Peronospora sparsa systemic infection in boysenberry tissue culture. European Journal of Plant Pathology. 153: 651–656.

  • Buried treasure: the hidden gems of alpine peatland

    Growing up, I had a fascination with pirates.

    I’m not sure if it was the fact that they stole buried treasure, sailed the seven seas, and broke all the rules or if I liked that they used the term “swashbuckling” to describe themselves. All I know is that I wanted to be exactly like Captain Jack Sparrow. Granted, Johnny Depp does quite well at making Jack Sparrow seem like the best and worst pirate at the same time, which definitely influences the likeability and comedy factor of the character.

    Peat Area in Perigi village, Pangkalan Lampam District, Ogan Komering Ilir Regency.
    Photo by Rifky/CIFOR cifor.org, CC BY-NC-ND 2.0 (Flickr)

    For the majority of the first Pirates of the Caribbean: The Curse of the Black Pearl, Sparrow, with the help of his slightly awkward, bumbling, and unlikely traveling companion, Will Turner (played by Orlando Bloom), attempts to chase down his precious pirate ship and crew of the Black Pearl.

    To steal back his ship and find treasure along the way, Sparrow and Turner must make their way through various tunnels and streams until they finally reach the be-all-and-end-all of all treasure rooms, full of the loot that the pirates have collected over the years.

    Oftentimes, to get to these places of “great treasure”, the pirates would use maps to find the hidden jewels they so desired, and if they were underground, well, they would dig for them!

    But what if hidden gems are not always jewels?

    Even Sparrow, the death-defying pirate who escapes prison, steals ships, drinks copious amounts of rum and loves treasure, says:

    “Not all treasure is silver and gold, mate.”

    Treasure is “wealth stored up or hoarded, something of great worth or value” and “a collection of precious things,” according to Merriam-Webster Dictionary. In terms of natural resources, water is a treasure.

    Water is crucial for humans. Water is also a critical worldwide currency and supports life as we know it. Beyond using water for cooking, cleaning, or washing, water is critical for supporting agricultural crops, farms and, therefore, our food sources. In many communities, water also has a spiritual value, more than a monetary or physical value. In New Zealand, the Whanganui River even has personhood status, highlighting just how important water is.

    Considered a natural treasure, water is extremely precious in dry, arid regions with little rainfall or annual precipitation, meaning plants and animals must adapt to limited water sources. The same applies to agriculture; farmers must adapt in dry regions, using water sparingly and wisely. In these regions, it is essential to understand where water comes from and goes to and how it is potentially stored underground upstream from agricultural land.

    Buried treasure, some might say.

    In the arid Chilean Andes, this treasure is buried in mountain peatland.

    Peatlands are wetlands with layers of compact and partially decomposed plants and organic material (i.e., dead and decaying plants) in water-logged soil. If you’ve heard of the “Tollund Man” (a well-preserved body from the Iron Age), then you’ve heard of peatland. Peatland may have standing water or vast swaths of very soggy ground, as pictured below. This makes it difficult to immediately understand their capacities to hold water.

    Great Kemeri Bog, Latvia. Photo by: Runa S. Lindebjerg, CC BY 2.0 (Flickr)

    Shelly MacDonell (Lincoln University) and a team led by Remi Valois and Nicole Schaffer investigated the ability of Chilean peatland in the Elqui Valley to store water and estimated its role in delivering water to agricultural areas via streams.

    The researchers chose a peatland (bofedal) in Spanish, called “Piuquenes” for their study because of its central location compared to surrounding peatlands and its elevation (approximately 3000 meters above sea level), making it a great representation of other Chilean alpine peatlands. This peatland was also chosen based on a proposal to place a dam at the edge of Piuquenes for agricultural water control downstream.

    To study the inner workings of Piuquenes, the researchers had to look below the surface. Picture someone on the beach using a metal detector to find potentially valuable items under the surface (like a modern-day pirate), and that is a very simplified view of the tools used to visualize the geology and structure of the peatland below the surface. However, using Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT), the researchers were able to create a 3D image of what might be under the surface. Through this 3D image, they could calculate the potential storage capacity (volume) of the studied peatland and estimate the role of high-alpine peatland in the area’s water cycle.

    According to estimates by researchers, the peatland itself could hold between 164,000 and 243,000m3 of water. That’s between 66 and 97 Olympic-sized swimming pools worth of water!

    The study found that the Piuquenes peatland can actually contribute water to lower agricultural regions downstream. However, the peatland is also vulnerable to water loss through evapotranspiration, which is a fancy word for water that evaporates and is lost from the vegetation and soil.

    Despite this water loss, researchers determined that Piuquenes was still important for supporting the surrounding ecosystems and could still act as a significant reservoir (i.e., source of water) for downstream agriculture and livestock grazing. They also discovered that the peatland could shield the area from drought impacts because of its water capacity. This means Piuquenes peatland could deliver water to grazing and low land agricultural areas via streams and limit the most severe effects of drought even in low-rain seasons.

    In addition to storing water, the Piuquenes peatland can also help produce soil from the slow build-up of decaying plants, store carbon, help plants grow and provide watered grazing areas for livestock.

    Understanding the inner workings of Piuquenes advances our knowledge of high-alpine peatland and its natural benefits to lowland agriculture. This study also adds valuable information to the discussion of if and how a dam should be built at the edge of this high-alpine peatland.

    Piuquenes, although located in the Chilean Andes, is an excellent example of how critical preserving and conserving peatlands worldwide.

    Studies have further investigated the secrets and treasures of peatlands, such as the carbon storage capacity, internal chemistry and nutrient cycling effects on methane emissions, proving that peatland continues to be a valuable ecosystem and that there is indeed treasure hidden beneath the surface.

    Peatland in Torronsuo National Park, Tammela, Finland. Photo by: Tero Laakso, CC BY 2.0 (Flickr)

    Current efforts have also focused on how to conserve these valuable landscapes and how local management initiatives could be applied worldwide. For example, Global Peatlands Initiative is a group dedicated to informing people about the importance of peatlands and keeping you updated on peatlands around the world.

    I’m pretty sure Jack Sparrow wasn’t referring to peatland as the treasure in his quote about silver and gold, but he was on the right track. If only he had known about the inconspicuous treasure hidden in the high reaches of the Andes!

    So, next time you’re on a swashbuckling adventure, keep your eyes open for what might be lurking under the surface and could be even more precious than silver or gold.

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

    P.S. Here is a really cool (and short) video about Peatland Protection from the UN!

  • The legacy of Smaug: Exotic worms conquer New Zealand’s soils

    My armour is like tenfold shields, my teeth are swords, my claws spears, the shock of my tail is a thunderbolt, my wings a hurricane, and my breath death!” Smaug from The Hobbit, by JRR Tolkien.

    Wyrms or worms? It’s probably not the introduction you’d expect from your typical friendly neighbourhood earthworm, but as it turns out, they’re not as harmless as they may seem. Could it be that introduced specimens are actually taking over the home-soils of worms native to Aotearoa New Zealand?

    I am king under the mountain!
    Image by whadatobexy (CC)

    An invasion as ruthless as that of Smaug (you know, the “specially greedy, strong and wicked worm” described in JRR Tolkiens “The Hobbit”), when he drives the dwarves from their tunnels beneath the Lonely Mountain? Well, maybe.

    New Zealand is actually one of the countries with the highest number of endemic earthworms (“endemic” meaning they exist nowhere else in the world). It has over 200 different species, all of them in the Megascolescidae family.

    They thrive in soils of native vegetation but rarely survive in land used for agricultural purposes. For this reason, it’s fair to assume that the land-use-change, caused first by the Māori, then the Europeans, was not appreciated by the worms living in that ground. With the introduction of agriculture and pastures, it didn’t take long for native earthworms to disappear, only hanging on in areas that were still covered with the original vegetation.

    Twenty-three species of European earthworms (from the Lumbricidae family) were introduced. They quickly took over the changed habitats and ecological functions from their New Zealand worm-cousins, which themselves continued to live in exile, deep within the realms of untouched soils (this, and further information can be found here).

    Can we mingle?
    Image by Petr Kratochvil (CC0)

    As described here, European species have been moving from agricultural land into adjacent native vegetation. We know from other parts of the world, like the US, that the presence of invading exotic earthworms causes changes in the soil, such as nutrient levels. This has effects on the entire ecosystem as well as on the native worms living there.

    One of the first studies to look at the co-existence of the exotic and native earthworm species in New Zealand was done by researchers from Lincoln University in 2016. The study was called “Response of endemic and exotic earthworm communities to ecological restoration“. The goal of the project was to find out if endemic earthworm species would come back to recolonise areas where native vegetation has been restored. The study looked at  two sites, located on the east and on the west coasts of New Zealand’s South Island. On one of them, plant restoration had been happening for over 30 years, on the other for 8 years.

    The team of researchers excavated soil from each site and hand-sorted out all worms present. In the lab, they were carefully identified as either endemic or exotic. After the slimy work was done, the following conclusion was reached: the populations of endemic worms increases alongside the length of the restoration period. In the meantime, the population of exotics remained more or less stable.

    In restored sites exotic and endemic earthworms can co-exist in native soil. However, exotics may make life more difficult for New Zealand’s endemic worms, perhaps by making the soil less favourable for them, or just eating up the yummy leaf-debris. Further studies are urgently needed! However, despite these negative implications, are exotic earthworms just another invasive species in New Zealand, something we should get rid of to save the natives?

    Care for a handful?
    Image by Sippakorn Yamkasikorn (CC)

    The endemic worms are definitely not as feisty as JRR Tolkiens dwarves (I imagine them perhaps with more of a sedate and gentle character, more hobbit-like really, lots of second breakfasts and idling around the Shire). They most likely aren’t planning a revolt to reconquer their homeland that has been turned into pastures and cropland.

    Today, agriculture plays an immense role in New Zealand, and the European worms have become indispensable to the farmland areas, as as they provide many benefits in terms of waste recycling, soil fertility and crop productivity. This has encouraged efforts to continue increasing the dispersion of exotic earthworms in New Zealand’s agricultural land in recent years. It seems the exotic worms, like Smaug, are already hoarding the “gold” of the New Zealand’s fertile lowland agricultural soils and have begun expanding their sovereignty into the depths of the native land.

    Our native worms may need their own King Under the Mountain to come and save the day!

    This article was prepared by international exchange postgraduate student Nicola Wegmayr as part of the ECOL608 Research Methods in Ecology course.

    The study this blog is based on can be read here. It is the source of most of the factual knowledge that has been included.

    Boyer, S., Kim, Y.-N., Bowie, M., Lefort, M.-C., and Dickinson, N. (2016). Response of endemic and exotic earthworm communities to ecological restoration. Restoration Ecology, 24(6):717-721. https://dx.doi.org/10.1111/rec.12416

  • Making a splash: Protecting the manu with Mānuka and Kānuka

    The art and joy of bombing off a bridge. Photo: Gen Toop. Dec, 2022

    “Do a manu” “Do a bomb”. On a hot summers day these are the chants that ring out across Aotearoa as packs of kids and adults line up on bridges or climb atop rocks and get ready to jump into a lake or a river. A ‘bomb’ or a ‘manu’ is a very precise manoeuvre that involves jumping from somewhere high, curling into a ball and making the biggest splash you can when you hit the water. Some would argue that a manu involves more technical aerial acrobatics than a simple bomb. Either way, the bomb or the manu is a rite of passage for many New Zealand kids.

    But increasingly this treasured national pastime is under threat. The Ministry for the Environment painted a grim picture of waterway health in its recent Our Freshwater report. Nearly half of New Zealand’s lakes are in poor or very poor health. Only two in every hundred lakes are in good or very good health. Many rivers have become so polluted that they are now unsafe for swimming at times. And it is not only humans who can no longer safely swim in some of the country’s rivers. Native freshwater fish are struggling to survive. More than three-quarters of them are threatened with extinction.

    The native freshwater birds that depend on rivers, lakes and estuaries, are also in peril. More than two thirds of them are threatened with extinction or at risk of becoming threatened. Introduced predators, like trout and stoats, are one of the main culprits behind the decline in native freshwater fish and bird populations. The degradation of freshwater habitat by pollution is another driver that is pushing these precious species closer to extinction. Cleaning up waterways is important not only for protecting the long-held tradition of doing a ‘manu’, it’s also critical to the protection ngā manu (the birds) of Aotearoa.

    Algal Bloom in the Waikirikiri, Selwyn River. Photo Credit: Gen Toop. Jan 2021

    Nitrogen pollution is one of the leading causes of the degradation of New Zealand’s freshwater ecosystems. When excess nitrogen on the land seeps down through the soil past the rootzone of plants it can get into the groundwater. From there it can move into the aquifers that many communities and cities get their drinking water from, or it can re-emerge in springs and get into lakes and rivers. Once in those lakes and rivers nitrogen can cause algal blooms, which can suck oxygen out of the water making it difficult for freshwater fish to survive. These algal blooms also make rivers a lot less appealing for jumping into on a hot summers day. Some algae are even toxic and can cause human health issues as well as kill sensitive animals like dogs.

    There are lots of different forms of nitrogen, but one of the main forms that leaches in this way is nitrate. The vast bulk of nitrate pollution getting into New Zealand’s freshwater comes from agriculture. That’s mainly because New Zealand’s pastures are loaded up with synthetic nitrogen fertiliser and the urine of the livestock feeding on these pastures has huge amounts of nitrogen in it. When livestock, particularly dairy cows, urinate the plants can’t always use all the nitrogen for their growth and so the excess nitrate can leach into waterways.

    Mānuka (Leptospernum scoparium) flowers. Photo Credit: Vil Sandi, Flickr, licensed under CC-BY-ND 2.0

    A promising new solution to this nitrate leaching problem has been explored by researchers from Lincoln University, Canterbury University and Plant and Food Research. In 2017, the scientists simulated a dairy cow urinating (not something many of us do in our day jobs) and compared the nitrate leaching rates under three tree species that could be planted into dairy pastures; radiata pine (an exotic species), mānuka (native) and kānuka (native). They found that mānuka and kānuka leached far lower amounts of nitrogen (2 kg/ha) than pine (53 kg/ha).

    Speaking about the project Dr Juergen Esperschuetz, the lead researcher from Lincoln university said, “These results show mānuka and kānuka could be even more effective at protecting water systems than anyone expected.”

    Intentionally planting trees into pasture where animals continue to graze is a farming system called silvopasture. Silvo is derived from the latin word for forest and pasture, well we all know what that is. Silvopasture is not just about shelterbelts, windbreaks, and riparian buffers, systems which relegate trees to the margins of a farm. Instead, silvopasture systems often plant trees into the paddock itself. It has been said that silvopasture, and other agroforestry systems like it, represent a shift away from monocultural production and towards an agricultural system that more closely mimics natural forest ecosystems. Mānuka and kānuka are native trees to Aotearoa so incorporating them into dairy pastures also provides a way to bring more native biodiversity back into farming landscapes.

    The researchers also found that soils under the mānuka and kānuka emit far less nitrous oxide, with the mānuka soils emitting the least of the three. Nitrous oxide is an extremely potent greenhouse gas, it is long lived and in Aotearoa, the vast bulk of nitrous oxide emissions come from livestock farming. So planting mānuka and kānuka into dairy pastures could also help in the fight against climate change. On top of that, both trees produce high-value products in the form of oils and honey and that could be used to supplement farm income.

    Cows grazing in a silvopasture. Photo Credit: Gayle Weaver,pixabay.com, licensed under CCO

    Since the publication of this study, other researchers have gone on to use parts of its methodology and draw on its findings in their research. In the Wairarapa, a study done in the field found much lower nitrate levels under manuka than under pasture, corroborating the findings from this glasshouse study done by Dr Esperchuetz and his team. In Spain, researchers also drew on the study when they investigated nitrate leaching risk under walnut silvopasture.

    This study has added to the toolkit of options available to help reduce the environmental impact of pastoral farming in Aotearoa. Incorporating mānuka and kānuka trees into pastures will not only bring biodiversity into farming landscapes. Thanks to this research, we now know it will likely help clean up our lakes and rivers too, protecting both ngā manu and the manu now and into the future.

    This article was prepared by Master of Science postgraduate student Genevieve Toop as part of the ECOL608 Research Methods in Ecology course.

    You can read the full article here: Esperschuetz, J., Balaine, N., Clough, T., Bulman, S., Dickinson, N. M., Horswell, J., & Robinson, B. H. (2017). The potential of L. scoparium, K. robusta and P. radiata to mitigate N-losses in silvopastural systems. Environmental pollution, 225, 12-19.