New Zealand Indigenous Grasslands

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Contents

Introduction

New Zealand's indigenous grasslands represent a significant part of the country's native cover (Brake & Peart, 2013). At present indigenous grasslands account for 13% of New Zealand's total land cover, a significant reduction form its former range at the time european settlement of 31% (Mark & McLennan, 2005).

However, much of this remaining area is in some state of degradation (Ausseil, Dymond & Weeks, 2011), caused by intensification of land use and poor agricultural management and invasion from exotic species.

Figure 1: Big sky vista in the MacKenzie Country, NZ [1]

These tussock grasslands are home and habitat to a wide range of native flora and fauna, including some of New Zealand's most unique species such as the Haast Kiwi, Kea, Grand and Otago skinks and the Takahe (Brake & Peart, 2013).

These grasslands also play a major role in securing water supplies for urban use and mitigating flood events--providing invaluable ecosystem services. The structure of the tussock leaf makes these grasses highly efficient at capturing water; from rain, snow, and fog. Water is transferred directly into the soil where it flows into rivers and catchments (Mark & Dickinson, 2008) that supply our cities.

New Zealand's iconic tussock landscapes and big sky country are also a significant contributor to the tourism sector, in 2009 alone over 900,000 people visited the Mackenzie Country (Toki, 2013), these tourists bring themselves and their dollars to these areas, wanting to experience the solitude, jaw-dropping vistas, and wide open landscapes.

For these, and many more reasons, it is essential that we protect indigenous tussock habitats and their native diversity. The size, scope and diversity of these grasslands makes it difficult to monitor changes in their biodiversity, functioning and health. What we do know, is that the health of these grasslands are at risk and we need to develop methods to monitor and react to changes in these landscapes.

History

The indigenous tussock grasslands of New Zealand are very unique and support a large degree of biodiversity. New Zealand grasslands have been extremely modified since the arrival of humans (see figure 2). After the arrival of the Maori large areas of native forest and bush were burned for hunting of the Moa and other game species, increasing the tussock area, but encouraging more fire resistant species to persist (Mark et al., 2008). In 1840 it is estimated 31% of New Zealand was covered by tussock grassland. With the arrival of Euorpeans, there was further modification of the grasslands through burning and agricultural practices, reducing tussock area significantly; only 44% of this area remained in 2002 (Anne-Gaelle et al., 2011).

Figure 2. Changes in the extent of indigenous grasslands since the arrival of humans (Anne-Gaelle et al., 2011). After colonisation by Maori and before European arrival, large tracts of native forest and bush were cleared by fire to aid hunting. Thereby expanding the natural range of the tussock grasslands, which was then further reduced after European arrival and the advent of agriculture.

More recently there has been moves in conservation and protection of indigenous grasslands,: of the 44% remaining, 28% is protected--though these have focussed primarily on alpine grasslands. There has been an ever accelerating loss of low altitude grasslands, as agricultural and other intensification land use practices continue. Along with upcoming tenure review and privatization of land, there is little protection of these grasslands. All of this leads to more modification of grasslands, disrupting the ecosystems and affecting ecosystem services further (Anne-Gaelle et al., 2011).

Biodiversity

Flora

Tussocks are typical for their growth habit, where stems grow fanning up and outward from a central bunch. Their leaves grow from the base, not the tip, which means that the new growth is protected both by surrounding stems and the leaf litter that encircles each plant. (Brake & Peart, 2013)

There are two broad categories of tussock grasslands:

Table 1: Two categories of tussock grasslands (Brake & Peart, 2013)

Besides the tussocks, this ecosystem is home for a wide range of native plants, like the upland shrub Leonohebe cupressoides, the Hector’s tree daisy Olearia hectorii, native Peraxilla mistletoes and the parasitic mistletoe Tupeia antarctica. (Brake & Peart, 2013)

Fauna

Some bird species need grassland ecosystems for their survival, like the endangered Haast Tokoeka kiwi, which lives in the low-alpine grassland in the South Island or the tiny rock wren, which make nests from tussock grass. Another bird who prefer tussock grassland is the New Zealand pipit (Brake & Peart, 2013).

Lizard species play a very important role in grassland ecosystems. They are a natural pollinator, who disperse seeds and act both as predators and prey. (Brake & Peart, 2013) Even though most lizards worldwide live in warm conditions, the South Island’s sub-alpine tussock grasslands are a centre for lizard diversity (yet it is still not known how they can cope with such extreme conditions) (Wilson 2012). The critically endangered Grand and Otago skinks are particulary well adapted to the cold upland tussock grasslands (Brake & Peart, 2013).

Invertebrates are also an important part of these ecosystems, as they help to maintain soil fertility and provide food for many native birds. We can find litter-dwelling invertebrates like mites or miriapods as well as larger insects like flies, midges, and bugs. The damp litter of the South Island’s indigenous grasslands is habitat of terrestrial stoneflies. Most of the 15 native species of grasshopper in New Zealand live in alpine zone grasslands. Another dweller is the large flightless tussock weevils. Slags and snails live there, as well as the earthworm family Megascolecidae. But these earthworms stay only in areas where the vegetation and soil remains undisturbed. There are about 48 identified native earthworms (Brake & Peart, 2013).

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Ecosystem Services

Figure 7. (a) Special features of narrow-leaved snow tussock (Chionochloa rigida) grassland (pictured here in Dunedin City’s water supply catchment) make it particularly efficient for water yield, yielding its leaf anatomy. (b) A camera lucida outline of a cross section of part of a mature leaf. The stomata (not shown) are adjacent to the photosynthetic mesophyll tissue and confined to the innermost reaches of the furrows on the concave side of the leaf. These furrows tend to close when the leaf rolls in response to low humidity, thus further reducing water loss. Adapted from Mark (1975) and reproduced with permission. (c) The diffuse, fine, elongated leaves of tussock allow them to intercept water droplets from fog, up to 0.5 L hr-1 by a single tussock in dense fog without measurable rain. (d) An area of snow tussock planted in 1974, on the crest of the Old Man Range in south–central New Zealand, showing their ability to accumulate snow on this highly exposed site. [2]

The concept of ecosystem services has been developed within the Millennium Ecosystem Assessment (2005). Human societies as well as individuals are benefiting from functional ecosystems, as they provide many services. Some of them are essentially important for humans to survive through provision of resources, others provide cultural or regulating services. The concept comprises of 4 main categories:

1. Provisioning services – like food, drinking water, fibre and fuel.
2. Regulating services – climate, floods, diseases, wastes and water quality.
3. Cultural services – recreation, aesthetic values or spiritual fulfilment.
4. Supporting services – soil formation and protection, primary production process, biogeochemical cycles and dynamics of biodiversity – all functions necessary for providing other services.

Here is a list of ecosystem services by Lemaire et al. (2011) expecting from grasslands, focusing on provisioning, regulating and supporting services, which are directly related to domains of agronomy, ecology and environmental sciences:

- Domestic herbivore feeding and animal production.
- The regulation of biogeochemical cycles and its consequences for the environment.
- Dynamics of biodiversity hosted by grasslands.
- Integration of grasslands within sustainable animal production systems.
- Interaction of grassland areas with other land-use systems at the landscape level.

It is clear that tussock grasslands provide many more services, including the cultural services. Tussock grassland areas are one of the most iconic New Zealand landscapes and therefore provide valuable recreational services, as well as aesthetic values. Tussock grassland help with sustainable provision of freshwater, as they can maximize water yield relative to other vegetation cover types. Some catchments yield up to 86% of rainfall to waterways and ultimately into the drinking glasses, kettles, baths and showers. Studies have shown that the yields are better than from any other cover (even bare soil) since tussocks require very little water (Department of Conservation). A long-term hydrological paired-catchment study revealed reductions (up to 41% after 22 years) in water yielded annually from an afforested catchment relative to adjacent indigenous grassland (Mark & Dickinson, 2008). Carbon sequestration and therefore a regulation service is another possible benefit of tussock grassland, which is currently under the research (Brake & Peart, 2013). Control of soil erosion and provision of habitat are provided as well.

Threats

Agriculture

Though there has been recent action in protecting alpine grassland areas, most of the remaining low to mid elevation grassland areas are rapidly being transformed through intensification following the privatization of land from tenure review. The privatization has lead to grassland areas being burned or cleared for agricultural purposes like viticulture, dairying, over-sowing, and grazing for sheep. In other instances the land is cleared for subdivisions and other development (Mark et al., 2009). Many of these practices lead to soil erosion, loss of ground cover, and pest invasion. The indigenous grasslands support many native species of New Zealand and are shown to support a wide range of flora and fauna, characterized by high species diversity. The rapid transformation and degradation of these areas displaces many species. Declines in population of many species that inhabit grassland areas have been recorded and indicate a reaction to the disappearance and modification of indigenous grassland.

Figure 8. Burning has been a major threat throughout history and still today for tussock area, it has substantially modified the habitat or completely cleared it out for human uses like farming or hunting (Photo: Craig Baxter, 2012).
Figure 9. Tussock area used for livestock purposes have been heavily degraded and destroyed (Photo: National Geographic, 2004).

Invasive Species

Indigenous grasslands have been heavily modified and the introduction of exotic species into the ecosystem by humans has lead to the invasion of pest plant and mammalian species. Many Mammalian species introduced into the area for hunting and other purposes have persisted as pests and threaten the indigenous grasslands as they utilize the resources of the grassland before it can regenerate (Mark et al., 2008).


Some of the pests include; feral sheep, goat, deer, chamois, rabbit and hares, and wild boars. Invasion from other plant species is also a threat to the health of indigenous grasslands. Through the heavy modification of grassland areas, over-sowing, and intensification for agriculture many new species have developed in grassland areas stealing up resources and area. Wilding pines from forestry plantations are a persisting threat and take over huge areas of tussock grassland. The invasion of wilding pines greatly influences resource allocation; as the area adopted by the pines increases, water catchment has changes dramatically as tussock and pines utilize the water differently (Paul, 2013). Increased pine in areas, decreases water yield in a catchment (Mark et al., 2008). Other invasive plant species that threaten tussock area include, Hawkweeds and Thistle.

Impacts of threats to Indigenous grasslands are expected to increase along with a reduction of indigenous biodiversity. The rate of change depends heavily on land usage, but will have significant impacts on the grasslands ecosystem structure and ecosystem services, such as water catchment (Anne-Gaelle et al., 2011).

Figure 10. Pine farms and forestry practices have led to the invasion of wilding pines in tussock area, which take over the grasslands and severly effect water catchment and storage (Photo: Neville Peat).
Figure 11. V-notch weirs recording water yield from each of the adjacent Glendhu paired catchments at 460–670 m, Lammerlaw Range, south-central New Zealand. (a) Pinus radiata was planted in 1982 over 67% of the 310-ha catchment at 1250 stems ha-1 (b) while the adjoining lightly grazed (~ 1 sheep per ha) reference 218-ha catchment remains dominated by narrow-leaved snow tussock (Chionochloa rigida) grassland. (c) The annual water yield difference (pine–snow tussock) between the two catchments up to 2004 is shown at the base. Data provided by B Fahey.

Indicators

Environmental indicators are developed to help monitor changes in environmental qualities over time and to aid in making managerial decisions. Developing reliable indicators to assess biodiversity and ecosystem health is not an easy or straightforward task, and is one scientist's the world round are struggling with. In New Zealand indigenous grasslands, the populations of many key faunal species such as the Takahe, Haast Kiwi and the Kea are already so drastically reduced with their habitat so fragmented, that they cant be used as reliable indicators in of themselves.

Also, measuring overall system health and biodiversity requires combining both the abiotic and the biotic, assessing inputs from multiple factions such as changes within plant communities, animal communities and invertebrate populations as well as changes in habitat areas, soil erosion and invasion pressure from exotic species. Walker et el (2006) State that the two greatest threats to biodiversity are the loss and fragmentation of native habitat and invasion by exotic species. Both of these threats are being faced in the indigenous grasslands, making it imperative that we deduce some way of monitoring the impact of these threats on the health of these grassland systems.

Water Quantity - Potential Indicator?

Figure 16: (a) Lysimeter in snow tussock grassland on the Lammerlaw Range, measuring water yield associated with bare soil. Sheltering tussock has been cut. Other lysimeters are located in the undisturbed tussock grassland beyond. (b) Annual water yields associated with snow tussock grassland and bare soil in relation to precipitation at five sites on the Otago uplands: lysimeters at 1000 m on the Rock and Pillar Range; the weir measurements from the Glendhu catchment at ~600 m (G’dhu; Pearce et al. 1984); lysimeters at 1140 m on the Rock and Pillar Range (R&P), 870 m and 490 m on the Lammerlaw Range (L’law; Holdsworth and Mark 1990).[3]

Tussock grasslands play a significant role in helping to secure fresh water supplies, transporting it through the ground into tributaries and rivers which feed into and are used in urban areas. Studies by (Mark & Dickenson, 2008) have shown that a healthy functioning tussock grassland can yield as much as 80% of measured annual rainfall, whereas exotic short grasslands yield <1%.

However, this input is reliant on the tussock ecosystem being in a healthy functioning state. There is the potential here to develop an indicator of tussock health by measuring the amount of water captured by the tussocks. Using strategically placed lysimeters and rain gauges within catchment areas, the amount of water captured from the tussock lands can be measured and recorded, and once corrected for local rainfall, could be used to monitor trends over time.

A optimal range for percentage of rainfall captured in healthy systems would be estimated and variances from this range could indicate increasing or decreasing health of the ecosystem, and the need for managerial action.

In the 1980's Dunedin city council acknowledged the water capture benefits of tall tussock grasslands, purchasing the land in the upper catchment area around dunedin, developing the Te Papanui Conservation Park [6] (approximately 22 000 ha, dominated by tall tussock grassland) and their review of government held leases on adjacent properties, which were aimed at obtaining the long-term security of water supplies by ensuring the maintenence of tall tussock grassland in good condition (Mark & Dickinson, 2008).

An economic valuation conducted in 2003 assessed the value of the water produced by the Te Papanui Conservation Park to be about NZ$136 million (Butcher Partners Ltd, 2003, in Mark & Dickinson, 2008).


Environmental Trends in Tussock Ecosystems

Habitat Area: Tussock grasslands in NZ reached their largest extent in the 1840's directly prior to European colonisation, (Fig 12) covering approximately 31% (82 432 km2) (Mark & McLennan, 2005). Since then large tracts of this habitat have been modified or completely removed, in most cases to make way for increasingly intense farming practise, with the current extent (as at 2002) now only 13% (36 047 km2), (Fig 13), (Mark & McLennan, 2005).

Continuing to monitor declines or increases in habitat area/extent is the simplest and broadest indicator to quickly asses the state of the grassland ecosystem, as habitat areas is key to sustaining healthy levels of native biodiversity and proper ecosystem functioning.

But this form of monitoring does have it's drawbacks; The Land Cover Database (LCDB) 1 and 2 (used to develop Fig 12 & 13) are the first attempt in NZ at comprehensive vegetative mapping, however at this point it is fairly coarse assessment. With a 1 ha mapping unit, incremental losses of indigenous vegetation and gradual trends such as succession processes and degradation aren’t detected (Walker et el, 2006), and are the changes we want to know about - as at this point intervention to correct is easier, generally cheaper and more effective.

Figure 12. South Island baseline distribution and extent of the five major indigenous grassland types, associated high-alpine communities, and permanent ice and snow at the time of European settlement in the early 1840s [4]
Figure 13. Distribution and extent of tussock land cover categories in the South Island as at September 2002 [5]


Species Richness: Using data reported by Duncan, Webster & Jensen (2001), from their research on declining species richness in tussock grasslands we have constructed the following graphs (Fig 14, 15). Depicting the changes in mean species richness over a number of years (note that the data for 2010 is projected and not included in Duncan et el, 2001). Their study of vegetation change was conducted on 142 permanent transects throughout Otago and Canterbury, covering areas of both conservation and pastoral management as well as a range of elevations. Over most of the 142 transects included in Duncan et el (2001) study, mean species richness had declined, although two species showed an increase in local abundance, Chionochloa and Hieracium. Increase in Chionochloa is thought to be due to reduction in grazing pressure while the increase in Hieracium concurs with the well documented increase of this species in tussock grasslands over the past decades [7]. Most of the other native and introduced species have declined in abundance, leading to significant and widespread decline in species richness. The species that have suffered the greatest declines are the small herbs, rushes/sedges, ferns, large herbs and grasses (excluding the Chionochloa species) (Duncan, Webster & Jensen, 2001).

This type of monitoring effort is one of the best ways of assessing the state of a natural system, and help to understand and figure out what factors may be driving the changes observed, while assessment of species richness indexes can indicate changes in local biodiversity. Studies like this one need to be continued and expanded to help monitor the health of Indigenous tussock grasslands, and to help provide a broad framework to aid the understanding of changes in composition of tussock grasslands in response to management practices and invasion by exotic species (Duncan, Webster & Jensen, 2001), unfortunately the funding for this monitoring project was cut in 1999.


Figure 14. Trends in different species richness between 1980 and 2000 (2010 data is projected) from data collected by Duncan, Webster & Jensen (2001), from 142 transects across Otago and Canterbury
Figure 15. Trends in total species richness, native and introduced species richness between 1980 and 2000 (2010 data is projected) from data collected by Duncan, Webster & Jensen (2001), from 142 transects across Otago and Canterbury .

A Network of Monitoring Sites: Maintaining permanent plots such as used in this study, in a network covering the geographic extent of the tussock grasslands, would be invaluable in the long term monitoring of changes within these habitats. Geographically extensive monitoring methods such as this are able to give a much better idea to the extent and magnitude of changes occurring in these grasslands (Duncan,Webster & Jensen, 2001), that cannot be gained by single, local area studies. Data collected at these monitoring sites can also be expanded, in order to give a fuller picture, including bird and animal counts, invertebrate sampling and abiotic measurements such as snow and rainfall, soil and air temperatures, humidity, pest trapping and monitoring (tracking tunnels) etc.

Overall, It appears that indigenous tussock grasslands in New Zealand are declining both in area and biodiversity - although there is some hope with still more large areas of high country tussock being turned into conservation land through tenure review, however this does not stem the loss of species and local species richness, nor does it stop the invasive spread of exotic species and pests. Whats needed is methodical and continued monitoring - through permanent site annual monitoring or some equivalent that can be used as a basis for decision making at local, district, regional levels and inform policy making for the continued presence of tussock lands in a healthy functioning state.


References

Anne-Gaelle E., John R Dymond and Emily S. Weeks (2011). Provision of Natural Habitat for Biodiversity: Quantifying Recent Trends in New Zealand, Biodiversity Loss in a Changing Planet, PhD. Oscar Grillo (Ed.)

Ausseil, A. E., Dymond, J. R., & Weeks, E. S. (2011). Provision of Natural Habitat for Biodiversity: Quantifying Recent Trends in New Zealand, Biodiversity Loss in a Changing Planet, PhD. Oscar Grillo (Ed.), ISBN: 978-953-307-707-9, InTech, Available from: http://www.intechopen.com/books/biodiversityloss- in-a-changing-planet/provision-of-natural-habitat-for-biodiversity-quantifying-recent-trends-in-new-zealand

Baxter, C. McNeilly, H.(2012). Otago Daily Times: Hyde tussock fire still burning. Available from: http://www.odt.co.nz/regions/otago/218118/hyde-tussock-fire-still-burning

Brake, L., Peart, R., (2013) Treasuring Our Biodiversity. Environmetal Defence Society, Auckland.

Duncan, R. P., Webster, R. J., & Jensen, C. A. (2001). Declining plant species richness in the tussock grasslands of Canterbury and Otago, South Island, New Zealand. New Zealand Journal of Ecology, 25(2), 35-47. [8]

Lemaire, G. et al. (2011) Grassland Productivity and Ecosystem Services. CABI, 305 p.

Mark, A. F., Dickinson, K. J. M. (2008). Maximizing water yield with indigenous non-forest vegetation: a New Zealand perspective. Frontiers in Ecology and the Environment 6: 25–34. [9]

Mark, A. F., McLennan, B. (2005). The conservation status of New Zealand's indigenous grasslands. New Zealand Journal of Botany. 43(1). [10]

Millennium Ecosystem Assessment, (2005). Ecosystems and Human Well-being: Biodiversity Synthesis. World Resources Institute, Washington.

Paul, T. "New Zealand Wilding Conifer Management Group". Available at: http://www.wildingconifers.org.nz/

Peat, N. Available from: http://www.doc.govt.nz/conservation/threats-and-impacts/weeds/common-weeds-in-new-zealand/wilding-pines/

Toki, Nicola. (2013). The magic of the Mackenzie. [11]

Walker, S., Price, R., Rutledge, D., Stephens, T. & Lee, W. G. (2006). Recent loss of indigenous cover in New Zealand. New Zealand Journal of Ecology.30(2): 169-177. [12]

Water and Tussock, Department of Conservation. Available from: http://www.doc.govt.nz/documents/conservation/native-plants/tussock-factsheet.pdf

Wilson, K.J. 'Lizards - Lizards in their environment', Te Ara - the Encyclopedia of New Zealand, updated 13-July-2012 Available from: http://www.TeAra.govt.nz/en/lizards/page-3