7 - Soil Biota in New Zealand's Agricultural Landscapes

7.1 - The importance of soil biota and the international concerns

A brief general description of the soil biota

The soil biota provides one of the most diverse areas of biodiversity. They include organisms ranging in size from microns (bacteria) to square kilometres (mycorrhizal fungi). At any particular site the soil biota vastly outnumber all other forms of life by many factors. Because of their great diversity and the hidden nature of the soil-dwelling lifestyle, they are one of the least known areas of life. This lack of knowledge of soil biology is only now becoming recognised beyond the groups of researchers engaged in this area, largely as a consequence of the current concerns for global biodiversity. Recognition of this knowledge gap overseas is giving rise to large soil research programmes. The development of molecular and labelled element techniques are to be used to identify pathways of energy flow - to see what organisms do what in the field247.

Up to 10 percent of soil may be organic material, and about 15 percent of this comprises living biota. Of the living biota, up to 90 percent may be microorganisms, with the remainder consisting of roots and fauna248. The fauna includes nematodes, earthworms, macro- and micro- arthropods and protozoa. The microorganisms include decomposers, N2 fixers, algae, mycorrhizal fungi and denitrifying organisms. Processes and products include microbial respiration, nutrient mineralisation, enzymatic activity and aggregate stabilisation.

This brief listing does no justice to the complexity and variability of the soil biota. In particular it is unable to illustrate the constantly changing integration and complementarity of the organisms present in the soil as they respond to the dynamics of the wider environment. Perhaps the most intriguing aspect that is emerging from research is the degree of integration and collaboration of system components.

Soil forms a vital and finite resource, the biological components of which are inextricably integrated with the above-ground ecosystems. Sustaining human society is dependent on our sustaining the productive capacity of the soil, but recent inventories indicate severe degradation on well over 10 percent of the earth's arable land249. When this is viewed in the context of the increase currently occurring in the earth's human population, it can be appreciated that problems for civilisation are imminent. This concern has given rise to a search for biological indicators of soil health and soil quality.

7.2 - Soil health and quality

Most New Zealanders are gardeners and many operate their own compost heap, based on the natural recycling of organic material by numerous biological entities. Gardeners realise that the organic content is crucial to the growing properties of the soil and addition of compost was the traditional solution to most physical, structural and biological problems of the soil250. Like most crop managers, gardeners know 'healthy' soil when they handle it, and particularly when they are growing things in it.

However a definition of a 'healthy' soil in terms of its biological constituents has proven to be an elusive task. This is partly because of the vastness of the biological unknowns but also because, although there is an intuitive understanding by the farmer/gardener of what is 'healthy', this concept does not easily translate to perceptions of natural ecosystems. Some vegetation systems may be undeniably healthy, even though sited on soils that no crop farmer would wish to manage.

In addition, the term health is itself somewhat nebulous at larger spatial and temporal scales relative to the organism. For example, although we might be easily able to label an individual tree as 'healthy' or 'unhealthy', an ecologist recognises that unhealthy trees form part of a healthy forest. Wide-scale dieback of trees may be a natural (healthy) response of the system to environmental changes. This happened, for example, with NZ beech forest after droughts in the early 1970's251. Such change encapsulates the history of the New Zealand ecosystems over geological time. When we then descend to the microcosmic spatial and temporal scales of the soil biota, within the agricultural environment where the system is continually subjected to a range of large scale climatic and anthropogenic disturbance, it can be appreciated that there are huge problems with applying simplistic labels.

So even within managed systems, an evaluation of 'health' from the biological components of the soil seems virtually impossible in comparison with the pragmatic approach of simply measuring crop output. In an effort to evaluate soil biological properties as potential bioindicators of soil health, Pankhurst and Hawke (1995) examined many biological properties over a wide range of management regimes. Properties monitored included total bacteria, fungi, and actinomycetes, total pseudomonads, cellulolytic bacteria and fungi, mycorrhizal fungi, plant root pathogens, bacterial-feeding protozoa, soil mesofauna, earthworms, microbial biomass, C and N mineralisation, in situ CO2 respiration, cellulose decomposition, and acid soil enzyme activity. They found that some of these biological properties were responsive to management, and therefore may have potential as bioindicators, while others did not. However, several of the biological groupings used include a range of functional entities which are therefore involved in a range of processes. As a result total presence does not easily equate with any particular processes or functions. They did find that some organisms/processes were indicative of the different system managements. Tillage with stubble management significantly affected root pathogenic fungi, protozoa, collembola, earthworms, and cellulose decomposition. Crop rotation affected mycorrhizal fungi, protozoa, and soil peptidase activity, and N fertiliser had a significant effect on mycorrhizal fungi, protozoa, and cellulose decomposition.

Within the constraints of soil type and climate in long-term trials there was little consistent association between earthworm abundance and crop yields252. Although their presence is commonly associated with improved soil structure, their abundance was substantially more variable than plant production. This provides a glimpse into the difficulties that have been met by soil researchers in quests for biological indicators of 'soil health' and 'soil quality'. When we move from these very simple macro-faunal assemblages to the host of microorganisms that are present in all soil habitats, we find that researchers of all groups have difficulty in defining characteristics of soil communities that are associated with above-ground systems or land management regimes in any consistent fashion. This is largely because of the tremendous influence of soil types and environmental events such as rainfall and disturbance associated with management.

The term 'soil quality' can include a wide range of physical, chemical and biological properties, but was defined by suitability for a particular end use253. In which case it is probably best measured by the end use in question, such as, for example, crop output. In comparison, soil health can be seen as 'the continued ability of soil to function as a vital living system...' and defining factors substituted some of the physical characteristics used for soil quality with biological ones such as 'biodiversity attributes'254.

The realisation that the soil biota is an exceptionally variable complex over relatively small scales of space and time does not preclude the possibility that particular configurations of soil biotic subsets may be identified in conjunction with particular systems. A considerable amount of work has been done in New Zealand, particularly on nematodes. The distribution of many soil nematode taxa is strongly influenced by factors such as soil texture, soil temperature and broad vegetation types255.

7.3 - The integration of soil biota with other aspects of systems

One factor known to be central to the performance of individual plants, their interactions with each other, and even the species composition of the plant community itself, is the activity of mycorrhizal fungi, which are symbiotically associated with the roots of most land plants. The importance of mycorrhizal fungi for nutrient acquisition by individual plants has been known for some time. But only recently have we become aware that because access to nutrients is increasingly restricted under competitive circumstances, mycorrhizal fungi can in part determine the outcome of interactions between plants, to the extent of influencing the species composition of the community itself256. In return, plant litter may be important in influencing a range of above ground and below ground properties and processes, particularly as regards the ectomycorrhizal fungi257.

Different plant species can be compatible with the same species of mycorrhizal fungi and be connected to one another by a common mycelium. Transfer of carbon, nitrogen and phosphorus through interconnecting mycelia has been measured frequently in laboratory experiments, but bi-directional carbon transfer between trees and seedlings and also between different ectomycorrhizal tree species also occurs258. A 'source-sink' relationship is envisaged that reveals an ecological support network that could help explain the ability of shade-tolerant forest seedlings to persist in stasis for long periods until canopy breakdown stimulates their eventual growth259.

Strong linkages also exist between the fungi/tree mycorrhizal association and the wider biosphere. For example, foraging activities of particular small vertebrates are responsible for the movement of mycorrhizal spores into meadows created by former beaver dams, and this in turn controls vegetation succession to conifer forest260.

The increase in efficiency of nutrient uptake from soil by using mycorrhizal stimulation of trees has been mooted. Inoculation of tree species in the nursery is logistically feasible and inoculated arbuscular mycorrhizal trees, when planted out, may serve as inoculum sources for inter-row crops261.

There are methodological problems in identifying soil biota assemblages. For example both sporocarps and morphotyping are sometimes ineffective for defining mycorrhizal communities262. Molecular techniques for identification of mycelia promised to tell much more about the structure and composition of mycorrhizal populations263. Read (1995) noted that information would only be of value if species composition could be interpreted in terms of the function of the identified organisms in the ecosystem. This illustrated the value of ecological models to research, with a series of symbiotic interactions between researchers in various fields being required to elucidate the activities of ectomycorrhizal fungi in nature. As with the subject matter this emphasises collaboration rather than competition.

There are multiple positive effects on plant growth and maintenance of soil quality by arbuscular mycorrhizal symbiosis264. In spite of these potential benefits to agriculture, at present, the realisation of the full potential of this symbiosis is not being utilised265. The understanding of interactions existing among crops, fungal partners and environmental conditions must improve to allow for the efficient management of the mycorrhizal symbiosis through selected agronomic practices and inoculation of cultivated crops.

7.4 - Current understanding of New Zealand's soil biota in agricultural landscapes

The literature suggests that the soil biota of improved pasture in New Zealand is heavily dominated by exotic organisms266. This situation is not restricted to New Zealand. For example Doube and Schmidt (1997) state that agricultural soils around the world contain few indigenous earthworms and have been colonised by a suite of about a dozen peregrine species. Springett (1963) revealed that enchytraeid assemblages of agricultural soil were generalist in nature compared with forest soils.

The dominance of exotic fauna in our pastoral systems might be expected from our knowledge of the integrated nature of system components. In addition, large amounts of soil must have been transported here during the early settler period when plants were constantly being brought out from Britain. The New Zealand agricultural landscape is thus largely exotic above and below ground. However, despite the many exotic biota which were introduced here, the exotic system left behind many integral components. So the agricultural landscape may be far more representative of a system that has 'unfilled niches' than is the 'island systems' of New Zealand, particularly late successional native forest. It is well known that the shorter the disturbance cycle, the greater the opportunity for 'weedy' type taxa to establish. Weeding the garden is fighting the ecosystem, and very energy consuming. Wardle et al. (1995) found raised numbers of bacterial feeding nematodes associated with high weed numbers. Both groups are part of a rapidly cycling system which is obvious at the scale of the farmer. There are far more 'weeds' in the agricultural landscape than appear in native forest, and it is the disturbed, early successional native systems that are most susceptible to invasion by these weedy taxa. Many such taxa evolved in the highly competitive environments of the large continents, but additionally, regular disturbances from agricultural practices have selected for weed species that are far less reliant on associated biota such as mycorrhizal fungi, and so may more easily colonise disturbed ground.

While the dominance of exotic biota may be true also for many of the micro-organisms such as parasitic nematodes, many of these taxa have very poor dispersal capabilities and so some degree of indigenous mico-biota are likely. At the macro-arthropod level we can see that selection of native species appropriate to the habitat occurs, as has happened with grass grub and porina moth.

7.5 - Potential gains

Several areas of applied research on the soil biota in New Zealand have indicated the economic and ecological gains to be made from an increased knowledge of this part of the biosphere. For example, the presence of endophytic fungi in pasture grass is well known. Clavicipitaceous endophytes of lolium were found to not only cause 'rye grass staggers' in stock, but also to confer resistance of the grass to Argentine stem weevil267. Further investigation showed that parasitism of weevils feeding on pasture with the endophyte increased after a 'learning' period by the small wasp parasitoid. Knowledge of the interactions has been transferred into management and e.g. farmers can now buy various mixes of endophyte infected grass seed, with varying resistance to weevils and reduced effect on stock.

Two of New Zealand's most important insect pests, grass grub and porina, are endemic species which have successfully colonised the improved pastures. Population densities of these insects within this new environment are far greater than in the native plant systems in which they evolved. Within these high populations diseases have flourished, and high numbers of diseases are recorded from each of these pests. These include bacteria, fungi, nematodes, viruses and protozoa. Diseases have frequently been associated with population collapses in both grass grub and porina. They can be applied artificially and so have a useful role in pest management268.

Ectomychorrizae are very species rich and can form close associations with particular plant species. In New Zealand systems, they associate particularly with manuka, kanuka and the beech species, all of which are relatively early 'single species' colonising systems in vegetation successions. Endomycorrhizal fungi in contrast are apparently not particularly species rich, and are very promiscuous in their plant association. This group are predominant in tropical rainforest systems, and are associated with our broadleaf rainforest species with tropical affinities. As the manuka/kanuka successional stages develop, an associated shift in the underground mycorrhizal community occurs. This change is reflected in the presence of tree ferns, which can associate with both ecto- and endo- mychorhizae269.

Pine systems are also early succession ectomycorrhizal, single species systems, and show a similar incursion of ferns and broadleaved species toward the end of a rotation. This suggests a similar soil biotic change as occurs in the manuka/kanuka systems. Needle leaf litter of Pinus radiata is captured by the trees' mycorrhizal associates, such that other saprophytic organisms are excluded, thereby retaining the resource for the trees270. This explains the characteristic build up of needle litter in pine forests, and contributes to the low occurrence of other vegetation in early-stage, dense pine stands.

7.6 - Reversibility

The 'reversibility' of the faunal assemblages with changes in land use was highlighted by the National Science Strategy for Sustainable Land Management as a topic of concern271. The little information available suggests that changes may be rather complex. In one instance after conversion from pasture to unmanaged kiwifruit and a subsequent deep leaf litter build up, earthworms disappeared and Amphipoda (bush hoppers) moved in272. These are the major agent involved in break down of leaf debris in the indigenous systems of New Zealand273. Investigations of changes in mineral soil biota after pasture was planted in radiata pine suggested that there would be few problems in restoring the populations of soil organisms important in controlling nutrient cycling in pasture after tree harvest, because both soil microbial biomass and soil microfauna can readily recolonise depopulated areas274. In contrast, presence of the Cromwell chafer, a rare locally endemic beetle dependent on a silver tussock and Raoulia habitat, was found to have disappeared where part of the original habitat was planted in pines275.

7.7 - Methodologies

The clarity with which assemblage changes might have been evaluated from the literature has been reduced somewhat because studies have often been influenced by tools such as diversity indices. These have been demanded for many years by peer review and journals, but have several failings. They were generated by a desire to be able to numerically compare communities and this same desire for a 'number' that may be ranked is also revealed in current calls for 'indicator values' of biodiversity.

Such tools treat all species as functionally equal and contain much less information than does the data from which they are derived. Composite diversity indices confound species richness, abundance, function, identity and attributes. As such they have been found to be of limited use in several studies where discrimination of communities and their attributes was sought276. Tokeshi (1993) in a major review, noted that the imbalance of attention given to diversity indices was due more to conceptual appeal than to any scientific rigour or superiority. They have more recently fallen out of favour as ecologists have realised that it is species attributes rather than just their number that define system properties.

The very term 'biodiversity' and the fact there is a current loss of species drives us toward seeking numerical summations of the biosphere. But in evaluating biotic communities and our effects on them we need to understand what it is we are evaluating. This is evident for both utilitarian purposes (e.g. the greater importance of pest species) and for conservation (e.g. the greater importance given endemic species). The major difficulty this poses for experimental approaches to biodiversity study using 'random' species assemblages has recently been highlighted277 and has generated considerable discussion. Traditional statistical tools are designed for quantitative evaluation and their inappropriate use, and strong influence on sampling design has long been questioned278. Investigation of natural phenomena must begin with a descriptive phase followed by the formulation of testable hypotheses which can then be subjected to a more rigorous mensurative experimental approach, tracking the 'what, how, and why' sequence of investigation279. Wiegart (1988) observed that "the null hypothesis, which assumes that there is no explanation for observed phenomena because they are entirely random, and which is such a powerful tool when interpreting the results of mensurative experiments, does not assist in the erection of ecological hypotheses". There is no reason experimental sampling that is not based on these statistical techniques should not be conducted, and that deliberate omission of these statistical methods was preferable to their misuse280. Rapport et al. (1997) in considering assemblages of soil biota concludes that presently, methods employing classical statistics are inadequate for situations where replicates are not appropriate or not possible.

The first requirement from researchers is for a sampling method that obtains samples characteristic of the habitat at a larger scale. This may require approaches that do not fit traditional statistical models. The consequences of this debate and of the present aims of biodiversity evaluation, are that more than ever before, we need people who are skilled in taxonomy of our cryptic biota. Once linkage of samples to various habitat types has been demonstrated, an evaluation of their attributes and affinities may be conducted. Management of the larger scale environment can then be guided by the information. Functional groupings may be used in summary comparisons of biotic community attributes281, provided there is confidence in trophic assignment, and that this addresses the questions being asked. For example such an approach cannot reveal the degree of endemicity of communities, which may be of crucial importance to a manager seeking guidance in a choice between different regimes.

7.8 - Gaps in current understanding, research and applications to safeguard New Zealand's soil biota in agricultural landscapes

The lack of comprehension of the lack of knowledge of soil biodiversity

The current demand for 'indicators of human impacts' on biodiversity is generally unappreciative of the vast knowledge gap that exists about the nature of configurations of the more cryptic components of biodiversity. There is an assumption by policy makers and management that 'we know it all' and it just has to be entered on computer to help us understand it. Nothing could be further from the truth. That this perception is a world-wide problem was shown by recent comments on a European conference on multifunctional landscapes282.

Before we can measure the impacts of humans on the constituents of the biosphere it is necessary to know what the constituents are, how they are arranged in the context of our perceptions and management, and how they vary spatially and temporally within both natural and managed systems. There has been, and is, an avoidance of this aspect of biodiversity evaluation and management by most organisations, both within New Zealand and worldwide as revealed by an early 2001 e-conference on biodiversity assessment283.

In New Zealand, the lack of policy maker/management comprehension about this lack of knowledge and it's requirement for the future has resulted in a long break in hiring staff and consequently, a loss of institutional knowledge from a flow-on of hard won experience from elder to younger researchers. This hiatus can in many cases no longer be rectified as many of the older researchers have now passed on.

An incomprehensible example of science 'management' occurred when a major New Zealand science organisation attempted to make redundant an irreplaceably knowledgeable person in the field of soil biota. Many other biological researchers have simply left to do other things or to work overseas. The above example gives some indication of how progress in understanding biodiversity has been impeded rather than facilitated by the last decade of science management here in New Zealand.

That we face the current biodiversity crisis with this large knowledge gap is an indictment of society's past science priorities and the 'technological fix' mindset that grew from them.

Prioritisation of research to fill gaps in understanding and applications to safeguard New Zealand's soil biota in agricultural landscapes

The greatest priority for biodiversity research is to obtain knowledge of the relative biodiversity of various vegetation systems and management regimes represented in our landscapes. This knowledge can then be used to advocate appropriate landscape management.

Most biodiversity occurs at the fine scale of the insects, so we need to calibrate the vegetation systems against the insects in the various bioclimes around New Zealand. This should be seen as an opportunity to begin to access the richest information source there is, as well as to enable the retention of biodiversity.

New Zealand is a small country with the population of a small overseas city and the subject of biodiversity is extremely large. Hence there is a need for pragmatic and integrated approaches, combining biodiversity research with current concerns so that it is of benefit to both applied and basic research areas. Main areas of concern are biocontrol, biosecurity, and biodiversity. These all require a supportive infrastructure, integrated and collaborative taxonomic and diagnostic resources, training and integration with the wider community.

Biocontrol

The Serratia grass-grub biocontrol area provides a good illustration of how biodiversity research could benefit applied research. The grass grub biocontrol work benefited from researchers seeing the pest as being part of the broader biological system. The team involved realised that the best place to search for a control was where the pest species occurred284. Although seemingly obvious now, very early work had researchers looking overseas for biocontrol options.

Just as the increase in populations of grass grub was a response to the vast increase in its environmental requirements by farmers establishing extensive grassland, so the increased populations of grass grub provided the environmental resources for pathogens of the beetle285. Observations of grass grub disease led to the isolation and identification of the bacterial agent Serratia sp.

Microbial ecology suggested that among microbes present in the soil environment, a full range of interactions from synergistic to antagonistic could be expected. For example, when second instar larvae were inoculated simultaneously with the amber disease-causing bacterium, Serratia entomophila, and the fungal pathogen, Metarhizium anisopliae, there was increased mortality above that due to either pathogen alone286. In turn, when the pathogens were cultured for inundative biological control287, bacteriophages which attacked the biocontrol agent, were elicited from the biological environment288. The researchers then developed phage resistant agents289. They also researched and developed the most appropriate delivery method for the biocontrol agent such that it would be most efficacious, working closely with the farmers290. Student projects have also been incorporated into the research291. The research team is continuing to look further afield at other agents, pests and applications where an understanding of entomopathogens would be of benefit, for example against the European wasps292 and lymantriid moths293.

At every step there has been a biological community context that has enhanced the researcher's understanding and the subsequent success of the next stage. In the past, where there has been dependence on chemical control, an understanding of the wider biological context of pests has not been important, and the 'single minded' chemical approach has been a contributing cause to the present biodiversity losses. However, the biocontrol programme briefly touched on here is evidence of some of the potential economic benefit that may be hidden by our general ignorance of the great majority of the biodiversity.

If insect pest research were to include a standardised broad sampling system that could be replicated in various management regimes, this could also function as a biodiversity sampling programme. While providing an understanding of the community context of a pest it could also provide a measure of the biodiversity of the particular system and season. It would also provide a training ground and a focus for the development of diagnostic, analytical and interpretive tools required to deal with the subject.

Biosecurity

One of New Zealand's greatest resources is our protection through isolation from a number of devastating exotic organisms. Although we have gate watchers at ports and a few observers around various crops, a major help would be a network of sampling systems already in place with both trained and training personnel. The network would be web linked and could be immediately alerted on detection of any new organism both within and external to the group. Rapid broadcast of digital images could help provide an early delimitation survey response, thereby increasing the chances of being able to catch the 'eradication window'.

One of the major problems with biosecurity is an inability to tell whether something is exotic or not. It is estimated we have over 20,000 species of insects in New Zealand and maybe 55 percent have been described. If we don't know what is already here and have very few trained people looking we increase the probability of organisms establishing and spreading beyond the point where they are eradicable.

Biodiversity

Because of current concerns with species loss, the effect of biodiversity (genetic variety) on system function is currently of particular concern. Loss of single species interactions flowing on into eco-webs has been documented but overall effects are not clear. Many natural systems, especially those in harsh environments, are both species poor and remarkably robust. Attempts to experimentally investigate biodiversity effects on function are caught in a catch 22 situation. Species are not functionally equivalent, and as size of experimental assemblages is increased, species which more strongly affect the qualities being measured have a greater chance of being included in the community, so experimental 'error' influences the results. In addition, natural assemblages are not random, and present statistical tools have difficulty defining the degree of difference, from the null hypothesis of randomness of communities.

The situation may perhaps best be approached from a logical perspective. As all species represent pathways of energy flow, a greater number of species suggests a greater number of available pathways and thus greater turnover potential. However generalist species (which represent many of those in the anthropogenic environment), may replace the pathways of a range of specialist species. Several studies have been interpreted as suggesting high functional redundancy (many species performing the same task) in communities. However, because the environment is dynamic, no study at any one time can define the mechanisms that may apply over much longer periods. So such apparent redundancy may actually be system contingency.

Most recycling successional pathways are not only undescribed but unappreciated. This is true not only at the microbial scale, but also at the much larger scale of forests. So postulates of biota being functionally 'redundant' may be somewhat premature. With our current limited understanding, we may be best advised to regard biodiversity per se as an irreplaceable resource that has enabled humanity to succeed on the planet to an unprecedented degree, and to nurture it accordingly.

If we wish to retain biodiversity in the landscape we live in, we require guidance from biodiversity on how best to manage the elements of that landscape. At present we use vegetation, but most biodiversity exists as insects. Therefore we need to get that management guidance from the insects. Because of their wide-ranging and multifunctional interactions with the entire biological system, the insects can provide us with a much deeper perception of the characteristics of the systems that comprise our landscapes.

The abiotic requirements for many of the elements of biodiversity that concern us in the agricultural landscape are well known as they are relatively easily measured. However the biotic environment provides a range of interactions that ultimately determine persistence and abundance of a species. Although some community characterisation has been done, this is often achieved using only one layer of the biota such as the vegetation, reflecting the present lack of integration in the New Zealand science community.

Research and application requirements

The main knowledge gap was determined to be of the linkages between vegetation systems recognised by land managers and the biodiversity that these systems represent. Most biodiversity exists as insects, so before we can use vegetation as indicators of biodiversity the attributes of the insect communities of vegetation systems must be compared. A core method exists for researching this (see Section 3.5), although the necessary collaborative mechanisms to enable information comparison across sectors are not yet in place. Similar linkages to the larger scale landscape features are also required for soil biota, although further work on methodology development appears necessary.

Therefore most of our current practical research requirements revolve around the need for a better description and appreciation of the biotic environment. These include:

  • The relative endemicity present in various vegetation systems and management regimes
  • The biological factors contributing to persistence of forage crops (diseases etc.)
  • The tailoring of crops to obtain resources from their biological environment rather than from high cost management input
  • The development of biocontrol programmes, many of which are constrained by a lack of persistence of the control agent in the biological environment.

Addressing these concerns would contribute to conservation, biocontrol, biosecurity, and management concerns, as well as to the growing international requirements pertaining to both biodiversity conservation and to markets.

  • The other major requirement is research integration - as modelled by the systems being investigated.

The non-integration of disciplines even within sectors has led to situations of high output based on high cost management input. This has inhibited development of understanding of the biological systems being managed.

An example of the widespread nature of this problem can be seen from the wide range of crop breeding programmes, from pasture forage to trees, that have in the past been undertaken without inclusion of health specialists such as entomologists and pathologists. Such researchers have usually been called in during field trials when health problems begin to appear, contributing to a 'reactive' (often chemically based) response.

We therefore recommend that MAF commission three reports to:

  • Collate information available that allows standardised comparison of attributes of the insect communities and soil biota of various systems, and interpret this information from the perspective of system management within landscapes.
  • Assess feasibility and logistics of a collaborative research programme directed at linking the attributes of biodiversity to components at the landscape scale, and provide a plan for a collaborative pilot scheme. This would be expected to integrate a range of researchers across institutional boundaries and enable modular development of system comparisons, tool development and training mechanisms.
  • Evaluate where existing research programmes such as those involving biocontrol and biosecurity might provide benefits to, and benefit from, being integrated into a national biodiversity research programme directed at understanding the attributes of insect and soil biota communities of the system components in New Zealand landscapes.

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