Overview and summary:

Managing conservation values - "seral tussock grassland workshop"

Landcare Research Seminar Room, Dunedin

Tuesday 10 September, 1996

Introduction
Key Points
Agenda
Summary of workshop outcomes
- Why are tussock grasslands important?
- Goals for conservation in the high country
- What factors are important in succession
Participants
Notes from focus talks

INTRODUCTION:

The purpose of the workshop was to gather the best knowledge on South Island tussock grassland conservation management that is currently available. This will provide the basis for a first version of a use- friendly computer decision support system which aims to help conservation managers, and others, to manage these grasslands for nature conservation. The workshop represents an integral part of a joint Dept of Conservation/Office of Crown Lands/Ministry for the Environment funded participatory project to provide decision support tools and processes for key issues and areas identified by South Island conservancies. Whilst it is recognised that there are many other plant communities in the high country (e.g. forest, shrublands, wetlands etc.), this workshop focuses primarily on the management of tussock grassland communities, which may or may not have a shrubland component.

This project is being coordinated by the Alexandra-based Landcare Research Knowledge Integration Processes Team. Kate Wardle and Willy Allen facilitated during the day, and Kate Wardle also undertook the background research and organisation for the workshop.

In a participatory or cooperatively-based project such as this, however, the most valuable input comes from all of those who participate, and collectively develop the workshop outputs. This workshop brought together representatives from the Department of Conservation, Knight Frank (agent to OCL), Otago University, Lincoln University, AgResearch and Landcare Research (see Appendix I). Focus talks were kindly provided by Professor Alan Mark, Dr Geoff Rogers, Professor Kevin O'Connor, Dr Bill Lee and Dr Ian Payton.

In the same context, this document attempts to represent a summary of what was generally agreed on in regard to tussock grasslands by those present. It should be read as minutes of the meeting which can be added to, amended or corrected by those at the next workshop on 17 October in Christchurch.

KEY POINTS

Workshop brief

It was agreed that the focus of the day was to develop and document sound strategies to manage seral tussock grasslands - within a range of different systems - in order to maintain/enhance conservation values. (This recognises the reality that while some tussock grasslands will always be managed primarily for nature conservation, there will be others that are managed as part of a production system.)

Workshop outcomes

During this workshop participants outlined the issues and considerations that (even if they are not explicitly addressed) must be taken into account in order to provide sound decision support for managers. These were developed through group sessions which looked specifically at: i) the goals sought by conservation managers; ii) the factors that influence tussock grassland dynamics; and iii) the management tools that are available. More detail on the outcomes of these workshops is provided in the following pages in the same order that occurred on the day. Copies/notes of the focus talks are provided as Appendix II.

The next step

Although a start was made on identifying strategies for the management of tall tussock grasslands late in the day, it was agreed that a further workshop to develop strategies for a range of grassland states should be held in Christchurch. This should be designed to build on the outcomes of this workshop. It was also suggested that the project coordinators develop a rough draft of strategies for specific grassland types as a basis for discussion at this second workshop.

It was also noted that the development of strategies/management actions for tussock grasslands outside of the conservation estate were complicated at a regional level by the implication of legislation such as the Resource Management Act, and by the variety of sets of goals that operated at an individual land manager level. Accordingly, it was agreed that this series of workshops would, in the first instance, be most productively aimed at conservation goals within the conservation estate.

And some important questions

i) Clearly there is a need to address the development of strategies/management actions for tussock grasslands outside of the conservation estate at some time. This would also need the involvement of groups such as regional/district councils and land managers.

ii) During the workshop session on goal setting it was noted that to effectively develop both representative areas and areas to be managed for natural succession consideration needed to be given to spatial factors at a regional and landscape scale. It was appreciated that this could not be addressed at this series of workshops, but is something that is needed to assist sound decision-making regarding the management of tussock grasslands for conservation purposes.

MEETING AGENDA

Introduction

Workshop 1: Why are tussock grasslands communities important to you?

Speaker: Alan Mark "Vegetation history of the high country and experiences at Black Rock"

Workshop 2: Outline the broad conservation goal in terms of type and state of high country vegetation that should be aimed for

Speaker: Dr Geoff Rogers "Shrubland succession in tussock grasslands"

Workshop 3: What factors are important in tussock grasslands succession processes ?

Speaker: Professor Kevin O'Connor "Disturbance and stress in tussock grassland communities & tools for management"

Workshop 4: Management tools available to help manage the conservation values of tussock grasslands (for conservators and farmers).

Speaker: Dr Bill Lee "Factors influencing tall tussock regeneration"

Speaker: Dr Ian Payton "Risks and benefits of burning tall tussock grasslands"

Workshop 5: Strategies for tall tussock grasslands

SUMMARY OF WORKSHOP OUTCOMES

Workshop 1: Why are tussock grassland communities important to you?

Refer to Diagram 1.

Workshop 2: Goals for the conservation of vegetation in the high country

Refer to Diagram 2.

There are two broad goals (complementary)

To allow processes for the succession of natural vegetation to continue towards the baseline of 1840 vegetation.

Some participants queried whether this 1840 goal is realistic when it is not really known what these past states were.
Maintain representative areas to ensure a suite of natural soils and vegetation. Need to maintain different ecosystems and communities including pioneer through to mature stages of tussock grassland communities.

The need to maintain range of ecosystems & communities (patchiness); can this diversity be achieved through natural disturbance, or will it need to require active management?

Both these goals are better achieved through a regional scale of landscape and catchment.

Both goals require active management in terms of weed and pest control. The need to maintain some ecosystems and stages of tussock grassland succession is also likely to require active management.

Diagram 1: Why are tussock grassland communities important to you ?

Diagram 2: Goals for the conservation of vegetation in the high country

Workshop 3: What factors are important in succession?

A. Vegetation attributes:

Vulnerability of species to disturbance depends on:

Vegetation structure, composition and dynamics. The structure of the vegetation determines the density, stature and openness of the community. The seedbank present in the soil as well as the adjacent vegetation type are important.

Species attributes: How competitive is it dependent on: longevity, palatability, flammability, response to defoliation/biomass destruction and disturbance. Plant life history is an important factor determined by such things as masting, seed production, germination, pollination, and vectors.

B. Bio-physical environment

N.B. All these factors influence at both local and wider levels (catchment, region, etc.)

Characteristic of Factors influenced:

environment:

Topography: Soils, moisture, desiccation, humidity, wind drift, fire, reserve design, land use, biota

Soils: Nutrients (capital and flows), moisture regimes, biota

Climate: Biota (wind drift), soils, fire vulnerability/pattern, recover/growth rates, (at wider levels consider influence of climate change)

C. Grazing and burning disturbance:

Burning: All considerations relate to intensity, frequency and seasonality

Impact of burning depends on:

Pre-burn species composition and structure (native and introduced), survival of perennating parts, vulnerability to weed invasion, state and composition of seed bank in soil (both desired and undesired), impact on soil health (nutrients, microbial and water holding capacity)

Grazing:

Impact of domestic stock grazing depends on:

Vegetation structure and composition, thereby affecting biomass. Results in selective removal of species (palatability), landscape nutrient redistribution, net loss of nutrients through stock removal and desiccation of soil. The impact is restricted to accessible country, and there is a degree of control of impact, as stock can be moved.

Impact of feral animals & invertebrate browsing depends on:>

Vegetation structure and composition, thereby affecting biomass. Results in selective removal of species (palatability), landscape nutrient redistribution, seed predation (invertebrates), desiccation of soil and disturbance (eg. rabbit scuffing). They are difficult to control, collectively impact on wide range of habitats from bluffs to mountaintops.

Factors affecting succession of tussock grasslands by shrubland vegetation (From overhead: Geoff Rogers)

Seed components: Source pattern, dispersal agents (wind dispersed seeds spread further than bird dispersed seeds), periodicity.

Invasability: plant vigour, topography and system productivity

Population growth: Systems productivity, disturbances (e.g. browsers)

Commented that species that can overtop desired vegetation are considered to be actual or potential weed problems (e.g. wilding pines), and low growing plants such as Hieracium (in terms of tall tussock grasslands) are not such a problem.

Workshop 4: Management Tools for Conservation

Refer to Diagram 3.

Note: Same set of tools for anyone (including farmers) but need recognition that their use is dependent on other factors such as finance, time, desire, competing goals etc.

Given that you want to maintain a range of tussock grasslands (seres/stages), and this is likely to require disturbance or active management .... how could you use these tools to achieve this goal?

Diagram 3: Management tools for Nature Conservation

Workshop 5: Management strategies for tall tussock grassland communities

Due to lack of time, this workshop was amended to a discussion. The umbrella management strategy for tall tussock grasslands discussed was:

Destock and burn only where scrub control is deemed necessary. Weed and pest control where feasible.

General Discussion

Mixed tall tussock grasslands and short tussock grasslands with adventive component are less management than tall tussock grasslands due to their altered nutrient status.

Chionochloa macra often occurs in a high stress environment, but should still be managed by excluding grazing.

Buffer zones (either on pastoral land or conservation estate) should be established around core conservation values. These would be periodically burnt to reduce fire loadings, and thereby protecting the core area from accidental fire. This approach could appease neighbouring property owners, who fear that high fire loading of conservation areas is a threat to their livelihoods.

Not all tall tussock grasslands should be used for nature conservation. Where used for pastoral use, got to recognise that they have different objectives to nature conservation.

Defining tall tussock grasslands. Recognised that there exists a continuum of stature, along nutrient, stress and disturbance gradients. Conservation managers need to have different conditions defined, so that they can apply the best management strategy. However, it is difficult to say when a tall tussock grassland no longer behaves like one.

Suggestions:

As long as there is some tall tussock component, the grassland will have some regenerative capacity.

20% tall tussock component is adequate for regeneration

Bare ground is OK

You can't just assess the grassland in terms of the tall tussock cover. Depends on type and extent of adventive plant component.

Red tussock may require more fertility improvement than other Chionochloa species.

Recognised that many semi-natural ecosystems do and will exist outside of the conservation estate. The need to develop management strategies for these was considered important. To be addressed in a future series of workshops.

APPENDIX II: Talks presented at workshop
A vegetation history of the High Country- Alan Mark

What is seral?
Following the succession climax model of Clements, when climax vegetation is disturbed, pioneer species establish first, followed by a number of seres. Eventually the climax state is reached again.

This model can be applied in some instances, e.g. plant succession after fire in Arthur's Pass; snow tussock grassland succession at Flagstaff Reserve, Otago; landslide events in Fjordland forests. Clements' model implied a progressive change through different vegetation states. This is not occurring in the South Island interior.

Kinetic models are considered more appropriate for these tussock grassland communities, where a landscape disturbance results in a gap phase. Therefore, a better term for these grasslands is indigenous induced tussock grasslands.

Black Rock Scientific Reserve, Otago is an example of tall tussock grasslands, which, after 18 years of monitoring after destocking, have remained an intact tussock grassland community. If this grassland was seral, it would have gone to shrubland (Hebe odora), but there is no evidence for this.

Vegetation History- see paper:- Mark, A.F. 1992. Temporal changes in the indigenous vegetation pattern of Otago, eastwards from the Lakes District. NZ. Ecol. Occ. Pub. No. 2. In Hunter, G.G.; Mason, C.R;. and Robertson, D.M. (Eds). Vegetation change in tussock grasslands, with emphasis on hawkweeds.

Shrubland sucession in tussock grasslands - Geoff Rogers

This talk was based on Geoff's North Island work, presented in the follwing paper:-

Rogers, G.M. & Leathwick, J.R. 1994: North Island seral tussock grasslands 2. Autogenic succession: change of tussock grassland to shrubland. NZ J. Botany 32: 287-303.

Disturbance and Stress in Tussock grassland communities- Kevin O'Connor

Updated version of Figure 5.4 from McKendry & O'Connor 1990- The relationship of habitat conditions and vegetation management options.

The talk drew on work presented in McKendry & O'Connor 1990, chapters 1 and 2, which are included here.

Key points made:

We shouldn't depend on overseas data to fill the deficiencies in our knowledge regarding e.g. impacts of burning on tussock grassland communities

Burning:

Grassland sites can take as little as 4 years, and over 15 years to recover from burning. Recovery rate is dependent on the particular site's attributes, and post-burn grazing regimes.

Short tussock grasslands respond to N P K fertiliser. However, cocksfoot has a higher response rate to fertiliser than blue tussock of fescue tussock.

A farmer's goal is to achieve high intertussock diversity, with a slow rate of recovery of tussocks post burn. If this is achieved, he won't have to burn so often

There is little role for burning or grazing to meet conservation goals.

Grazing:

Grazing acts both as a disturbance and stress inducing factor.

Disturbance can be reduced through adoption of a no grazing- no burning regime

Stress can be reduced through application of fertilisers

Disturbed tussock grasslands in poor condition may be problematic when disturbance is reduced, especially where aggressive weed species are already present. These grasslands may need moderate disturbance to maintain their value.

Such grasslands would be less vulnerable where native species which respond well to disturbance occur, and occupy those sites instead of weed species.

Factors influencing regeneration of tall tussock grasslands - Dr Bill Lee

Reproductive ecology of Chionochloa species

lon-lived bunch grass

irregular flowering reflected in both intensity and frequency

seedling recruitment only in mast years (1 in 5)- climatically induced

restricted seed and regeneration shadow - within small area around adult

long juvenile phase of tillers/tussocks

moderate seed viability (50 - 70%)

short-lived seed bank (~300 days (Spence))

limited vegetative reproduction via fragmentation (more so in C.rubra than C.rigida)

Management impacts on tussock regeneration

Burning - natural disturbance (once per century)

induces mass flowering (forced flowering; size of seed is different)

germinates some dormant seed (depends on time period since last burn)

facilitates large-scale seedling recruitment

reduces subsequent reproductive effort for several decades (see Allen & Payton)

rejuvenates tiller/tussock population

provides temporal window for invasion of other plant species

retards succession to indigenous scrubland

Mammalian grazing - novel disturbance (e.g. rodents, stock etc)

Stock grazing is primary way for weed introduction

dominated by tall tussock forms poorly adapted to mammalian grazing

decreases reproductive vigour of adult plants

increased seedling mortality (different animal select different species)

retards post-burn recovery (decimate seedlings and remaining adults)

spatially uneven (tussocks get selectively grazed when snow cover protects everything else

may increase species diversity and intertussock cover

grazing can control weeds in grasslands, but the range of unpalatable weeds make grazing as a tool tricky

Maximising regeneration in current tall tussock grassland communities

recognise that the past century of feral (deer, rodents, rabbits, hares) and stock (sheep, cattle) grazing, and frequent burning, has reduced the reproductive vigour of many tall tussock grasslands

reduce/eliminate mammalian grazing as ill-adapted to any form of mammalian grazing

abandon goal of maximum alpha diversity in indigenous tall tussock grassland (we can't manipulate grasslands to maintain this)

accept slow and variable rates of tussock grassland recovery/expansion

control local infestations of woody weeds

accept natural successions to woody vegetation, while maintaining local examples of induced tall tussock grassland (10%?) where periodic burning is practicable

The risks and benefits of burning tall tussock grasslands - Ian Payton

In last 6 years at least 5 documents partially or wholly concerned with impact of fire on tussock grassland communities. Several of the authors here today.

Fire has traditionally been regarded as an integral part of pastoral management practice in tall tussock grasslands
* stock access
* palatable regrowth
* control of woody vegetation

Burning of tall tussock grasslands now much reduced
* still areas where farmers jealously guard what they regard as their right to burn

Don't have tradition of fire as a grassland management tool for conservation purposes
* land tenure review process, significant areas tall tussock coming into Conservation Estate
* concern that buildup of flammable biomass in grasslands no longer grazed or burned could pose risk if there is an accidental fire when conditions are dry
* irrespective of whether you think the risk is real, the perception that there is a risk is real
* within DoC those with fire control responsibilities appear to be accepting of the need to use fire as a tool for managiing tussock grasslands
* elsewhere within DoC I suspect there is much less acceptance of the deliberate use of fire

In a pastoral management setting fire seen as something affecting sustainability
- soil fertility, productivity
From a Conservation standpoint retention of indigenous biodiversity is primary issue
In reality these two issues are linked because factors such as site fertility affect the ability of species to establish, compete and dominate.

For DoC key issues relating to the use of fire in tall tussock grasslands appear to be
* how does fire affect populations of native plants and animals
* are "hot" fires more detrimental than "cool" fires
* what effect does the interval between fires have on the outcome

For C. rigida grassland we have quite alot of information about the dominant tussock species. Similarly for C. macra and C. rubra.
* don't appear to have this type of information for many other parts of the system.

* now beginning to get a few papers that look at the rates and direction of vegetation change after fire, but I know of nothing of this nature for the faunal components of New Zealand grassland ecosystems

As part of our Output 15 tussock grassland programme this year we're starting project to look at the effects of fire on both biomass and nutrient pools and fluxes and biodiversity in tall tussock grasslands.
* initially look at C. rigida grasslands in Otago
* hope to be able to extend this to a comparison of C. rigida/C. rubra communities

One other point I'd like to make

In the next 6-9 months Landcare and AgResearch will be relooking at where their tussock grassland research effort is directed
* the question of tactical relevance will be an important consideration in these discussions
* for those of you not up with Foundation-speak, tactical relevance is the term used to describe the requirement by end-users for the research, the extent to which end-users are prepared to assist by committing their own resources
* I'm hopeful that today may provide a useful beginning to this process

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