Tussock Grassland Sites Research Articles

Biodiversity of indigenous tussock grassland sites in Otago, Canterbury and the Central North Island of New Zealand VI. Coleoptera biodiversity, community structure, exotic species invasion, and the effect of disturbance by agricultural development

The diversity of Coleoptera communities in tussock grassland at two sites in Otago, one in Canterbury and one in the central North Island, was compared. The impact of agricultural disturbance on the communities was compared between native tussock, tussock oversown with exotic pasture species and cultivated sown pasture. Coleoptera were heat-extracted from turf samples taken in summer in two consecutive years. In native and oversown treatments, Staphylinidae and Curculionidae predominated in abundance at three of the four sites, and in species richness at all sites and treatments. Carabidae were more species-rich than Curculionidae in cultivated treatments at most sites. The mean density of Coleoptera in native tussock treatments ranged between 654/m2 and 97/m2. Carnivores were the predominant trophic group followed by herbivores. Species diversity was higher in the native or oversown treatments and the Otago sites were the most diverse overall, and the least disturbed. A total of 19 exotic species were found but there was no relationship with treatment, although their density was higher in cultivated treatments. There was no evidence to suggest that modified vegetation provides a source of exotic Coleoptera species to invade native tussock.

Variation in the effects of vertebrate grazing on fire potential between grassland structural types

Summary 1. Vegetation fires can have major social, economic and ecological consequences. Research into fire behaviour has aimed to give managers greater ability to predict and control fires. Fire and grazing are important and interacting disturbances in grasslands. Fire is known to widely affect grazing patterns, but the effects of grazing on the incidence of fire are less well known. There have been few tests of the idea that ‘grazing reduces blazing’, which has popular and political currency in some countries. This study addresses the hypothesis that grazing affects fire potential in native grasslands. 2. Paired grazed and ungrazed quadrats were established at five lawn and five tussock grassland sites. Fuel load, percentage dead fuel and the number of days sustaining fires where possible were compared between treatments. 3. In lawn grasslands, grazing markedly reduced fire potential through the removal of plant biomass and by preventing the vegetation escaping into the unpalatable and flammable tussock state. Grazing led to increased fire potential in tussock grasslands where animals selectively removed live shoots, leaving a high proportion of dead fuel. 4. The difference in flammability responses to grazing between lawn and tussock grassland appeared to be due to differences in palatability that in turn may relate to soil fertility and the constancy of intense grazing. These differences mean that grazing lawns and tussock grasslands are likely to be subject to differing disturbance regimes. This association between disturbance regime and vegetation structural type suggests that lawns and tussock grasslands represent alternative stable states within the grassland ecosystem. 5. Synthesis and applications. Grazing is only likely to reduce the probability of fire where the bulk of the vegetation consists of potential food for grazing animals. It is likely that the negative relationship between vegetation palatability and fire potential applies to grasslands generally and possibly to many other vegetation types. Grassland managers may need to manipulate disturbance regimes in order to maintain vegetation structural heterogeneity and thereby promote landscape‐scale biodiversity.

Biodiversity of indigenous tussock grassland sites in Otago, Canterbury and the central North Island. V. Penicillia and aspergilli

In the course of a series of investigations into the biodiversity of indigenous tussock grasslands, penicillia and aspergilli were isolated from soil samples from four locations: Deep Stream and Mt Benger in Otago, Tukino in the central North Island and Cass in Canterbury. Samples were collected in the summers of 2003 and 2005 and, at each locality, were taken from sites under indigenous tussock grassland, under oversown tussock grassland and under pasture cultivated from tussock grassland. Isolations were made on potato‐glucose‐chlortetracycline agar plates inoculated with soil suspensions. Thirty‐six Penicillium species were recovered, all cosmopolitan, and of the 12 most common, 10 species: P. canescens,P.janthinellum,P.janczewskii,P.jensenii,P. lividum, P. loliense, P. melinii, P. miczynskii, P. sclerotiorum and P. simplicissimum were isolated from samples from all four locations but P. montanense and P. novae‐zeelandiae were not recovered from Deep Stream or Mt Benger. P. lividum and P. sclerotiorum were recovered mainly from samples from indigenous sites and P. jensenii from oversown or cultivated sites. In other countries, some of these species have been associated with forest‐grassland rather than grassland soils and it was thought possible that they were relics associated with pre‐human forest vegetation which may have covered the localities. At the subgenus, not species, level, however, the pattern was typical of grassland, not forest, soils, with the subgenus Furcatum dominant. Six of the common species are known to have the potential to produce tremorgens, neurotoxins known to cause incoor‐dination when ingested by mammals but with little investigated effects on invertebrates. Aspergillus cervinus was the only Aspergillus species recovered, only from Tukino and principally from samples from the indigenous sites.

Biodiversity of indigenous tussock grassland sites in Otago, Canterbury and the central North Island of New Zealand IV. Vegetation and the effect of disturbance by agricultural development and fire

The effect of disturbance by agricultural development on plant biodiversity was assessed on a broad development gradient in three major New Zealand tussock grassland types. We compared undeveloped, semi‐developed, and pastorally developed snow tussock (Chionochloa rigida) grasslands in Otago; fescue tussock (Festuca no‐vae‐zelandiae) grasslands in Canterbury; and red tussock (C. rubra) grasslands in the central North Island volcanic plateau. Plant diversity and structure were measured using height‐frequency transects. The effect of disturbance by spring and summer burning was similarly assessed in coastal and inland Otago snow tussock grasslands. Non‐metric multidimensional scaling ordination showed agricultural development had the greatest effect on plant communities, reducing indigenous plant species diversity and dominance, and increasing adventive plant species dominance. Spring and summer burning significantly reduced indigenous plant species diversity in the montane coastal Otago snow tussock grassland, but spring burning did not significantly decrease total or indigenous plant diversity in the inland alpine grassland. For biodiversity conservation in tussock grasslands it is critical that representative lower altitude areas are retained, and that tall tussock grasslands should only be burnt when retaining sufficient moisture to minimise fire impact. The quantitative determination of the effects of these disturbance factors will assist further investigation of vegetation‐fauna interactions, and tussock grassland ecosystem studies.

Biodiversity of indigenous tussock grassland sites in Otago, Canterbury and the central North Island of New Zealand II. Nematodes

Soil samples were taken from around the base of tussock plants and paired areas of inter‐tussock vegetation at four native tussock grassland sites across New Zealand, in three consecutive summers. Seventy nematode taxa were identified with the plant associated nematode trophic group being the most abundant at three of the four sites. Of the plant parasitic nematodes, Criconema, Pratylenchus, and Helicotylenchus spp. were found at all sites, with Hemicycliophora, Longidorus, a putative Punctodera, and Rotylenchus found at only one site each. The observation of mermithid nematodes at three of the four sites, coupled with absence of insect parasitic Steinernema or Heterorhabditis sp. from microscopic observations and soil baiting suggests that the insect parasitism niche is occupied largely by mermithids in the tussock grassland habitats studied. A range of community indices were calculated, with Shannon‐Weiner (2.10–2.39), Simpson dominance (0.129–0.205), Maturity Index (2.67–2.92), and Structure Index (67.7–87.5) being significantly different among sites. Total nematode abundance was significantly greater beneath tussock than inter‐tussock vegetation, but the number of nematode taxa and species richness were significantly greater from inter‐tussock samples. This suggests that tussocks may provide a more productive habitat but that the increased diversity of the vegetation in inter‐tussock areas is reflected in some measures of nematode diversity. Comparisons are made and discussed with other studies of native grassland nematodes in New Zealand and worldwide.

Biodiversity of indigenous tussock grassland sites in Otago, Canterbury and the central North Island of New Zealand I. The macro‐invertebrate fauna

This contribution introduces a short series of papers on biodiversity of indigenous tussock grassland at four sites in New Zealand. A survey of invertebrates of tussock grassland sites was carried out in summer of 3 successive years, 2001–03. The sites included two in Otago in snow tussock grassland at Deep Stream and Mt Benger, a site at Cass in inland Canterbury, and one at Tukino in the central North Island. Sampling was carried out by taking turf samples from each site, and extracting the invertebrates with heat extractors. The invertebrates were divided into 30 major groups. This quantitative sampling method allowed the densities of invertebrate groups to be calculated. Total macro‐invertebrate density for all sites ranged between c. 1600 and 5600 m–2. Total invertebrate abundance was highest at the central North Island site, but this was very much dominated by Formicidae. Across all sites, Formicidae, Coleoptera, and Pseudococcidae were consistently the most abundant groups represented.

Biodiversity of indigenous tussock grassland sites in Otago, Canterbury and the central North Island of New Zealand III. Soil microorganisms

Bacterial and fungal communities in indigenous tussock grassland soils were studied at four locations, Mt Benger and Deep Stream (Otago), Cass (Canterbury) and Tukino (central North Island). Soil samples collected from inter‐tussock and tussock areas were used to enumerate total culturable bacteria (colony forming units (CFU)) as well as a number of specific groups of bacteria, fungal types and diversity, and soil microbial functional diversity. Soil microbial biomass carbon (C) and nitrogen (N) as well as extractable C and N were also determined. Fungal populations were lowest at Mt Benger while fluorescent Pseudomonas was lowest at Cass. In these indigenous soils, bacterial CFU were c. 30 times lower and fungal populations c. 10 times greater than in developed New Zealand pastoral soils. CFU of bacteria in complex media (r‐strategists) were similar in magnitude to bacteria growing on weak CA medium (K‐strategists). The microbial biomass C in indigenous grassland soils were also significantly greater than that found in developed pastoral soils, possibly due to dominance of fungi in indigenous soils. Microbial C and N were lower in Cass and Tukino sites compared to Mt Benger and Deep Stream sites. Microbial nitrogen was also significantly greater (P < 0.001) in inter‐tussock than under tussock samples. The functional diversity of soil microbes, was significantly greater (P< 0.01) in inter‐tussock samples compared to tussock samples at all sites except Mt Benger. The total microbial activity, as measured by the colour development in Biolog plates (Average Well Colour Development (AWCD)), was low in Cass soil compared to others. Eighty‐three types of fungi belonging to 30 genera were recovered from the four sites. The diversity of fungi found in Otago sites was greater than in the other two sites (P < 0.001). Fusarium spp. that are often common in pastoral soils were conspicuous by their rarity in indigenous soils.

Comparison of the weevil fauna (Coleoptera: Curculionoidea) in two tussock grassland sites in Otago, New Zealand

Invertebrates exhibit exceptional levels of diversity and endemism in New Zealand where, historically, they have received only limited consideration in land management decisions. Many species exist outside the habitats typically set aside for conservation, such as lowland to subalpine Chionochloa tussock grasslands. These habitats are under‐represented as protected areas due to their modified state and their invertebrate fauna is poorly understood. Compiling inventories has been suggested as one means of facilitating a greater awareness of invertebrate diversity and ecology. This study presents an inventory of Curculionoidea recorded during a single quantitative sampling event in mid summer 2001, from two Otago Chionochloa tall‐tussock grasslands. Species diversity is compared with that of other southern South Island tussock grassland areas, and notes on weevil ecology and distribution are given. Of the 35 species known from the two sites, only 17 were recorded from samples taken in January 2001, demonstrating the importance of factors such as seasonality and microhabitat to study design. Genera recorded showed affinities with those of grassland studies in neighbouring ecological districts. Almost 50% of the species collected from the two sites were undescribed; this not only limits the capability of land managers to compare areas under consideration for protection or other land uses, but also indicates an abundance of unrecorded and unprotected biological diversity.

Trifolium ambiguum (Caucasian clover) in montane tussock grasslands, south island, New Zealand

A field experiment was conducted at nine montane tussock grassland sites forming toposequences of soil temperature, moisture, and fertility in the southern Mackenzie Basin, South Island, to characterise the adaptational range and development dynamics of the above‐ and below‐ground growth of Trifolium ambiguum cv. Endura under different defoliation treatments over a two‐year period. Successful establishment, high productivity, and survival occurred on lower slopes and mid‐altitude north‐facing slopes, but this cultivar appears unsuited to mid‐altitude, shady aspects with dense Agrostis capillaris cover, and at higher elevation, tall‐tussock sites. Plant growth in the establishment year was mostly confined to primary crown and taproot/fibrous root growth, although early rhizome development occurred in plants on the lower sunny slopes. In the second year, growth was characterised by crown and rhizome shoots during spring and summer and by the expansion of the below‐ground rhizome/root components in summer and autumn. In Year 3, of the below‐ground components, only secondary rhizomes and secondary taproots were active centres of growth. Plant survival and all below‐ground components declined where defoliation occurred in spring and throughout the growing season in Year 2. Defoliation treatments did not affect the below‐ground components in Year 3. The potential of T. ambiguum as a pasture legume in these environments is discussed.

An inoculant Rhizobium strain for improved establishment and growth of hexaploid Caucasian clover (Trifolium ambiguum)

Strains of Rhizobium leguminosarum bv. trifolii present in New Zealand soils are ineffective on Caucasian clover (Trifolium ambiguum) and inoculation with an effective strain of rhizobia is essential for nodulation. However, problems have been encountered with nodulation of oversown Caucasian clover and this study was conducted to determine whether nodulation could be improved by the use of an improved strain of rhizobia. Five strains of rhizobia were compared with a re‐isolate (ICC 105) of the recommended New Zealand commercial inoculant strain (ICMP4073b) for their effect on the establishment of oversown hexaploid Caucasian clover in Canterbury and Otago, South Island, New Zealand. When strains were incorporated in peat inoculant and used to inoculate seed in a commercial pelleting process, one strain (ICC 148) increased the percentage of seedlings nodulated over that obtained with ICC105, from 23% to 49%. In a further evaluation of these two strains, seed was inoculated and lime‐coated in the laboratory and stored for either 1 or 20 days before oversowing on 7 tussock grassland sites. Inoculation with ICC 148 resulted in a 1.3‐fold increase in the percentage of seedlings nodulated over that obtained with ICC 105. In addition, dry matter (DM) weights of individual seedlings were increased with strain ICC 148. The dry weights of individual Caucasian clover plants after 6 and 13 months increased 1.5 and 3.0‐fold, respectively, when inoculated with strain ICC 148. Inter‐tussock Caucasian clover DM after 17 months was 1870 kg ha−1 for plants inoculated with ICC 105 and 3480 kg ha−1 for plants inoculated with ICC 148. Foliage N contents in spring were increased from 2.6% to 3.1%, when seed was inoculated with ICC 148. These results strongly support a change in the Rhizobium strain recommended in New Zealand for hexaploid Caucasian clover to strain ICC 148.

Strategies to maximise establishment and production of oversown caucasian clover

Caucasian clover (Trifolium ambiguum M. Bieb.) is an alternative legume for areas where white clover (T. repens L.) growth is limited. However, slow establishment has been a problem when caucasian clover has been oversown. Results from two tussock grassland sites have demonstrated the importance of the initial establishment of caucasian clover. Caucasian clover dry matter production after 6 years was still related to original seedling establishment. This result was obtained in ungrazed swards, conditions likely to maximise the ability of caucasian clover to spread by rhizomes and natural reseeding. The results indicate that caucasian clover may make little contribution to legume yield in these environments for at least 6 years unless satisfactory numbers of plants are established initially. Maintenance fertiliser application, in early years at least, appears similar to that required by white clover. Yields of caucasian clover swards in the 6th year when maintenance fertiliser had been applied were 3-7 times those when fertiliser had been applied only at sowing. The paper also provides possible explanations for establishment failures that have already occurred, and provides information on correct management techniques to maximise establishment of oversown caucasian clover. Keywords: caucasian clover, establishment, fertiliser, hill country, inoculation, nodulation, oversowing, pasture, Trifolium ambiguum

Recovery of Chionochloa rigida tussocks from fires in South Island, New Zealand

Tussock and tiller characteristics of snow tussock ( Chionochloa rigida ) were sampled at 13 tussock grassland sites in eastern Otago, New Zealand. The sites were located at 500 m to 1100 m altitude in areas with minimal grazing by introduced mammals. They were last burnt 1 to 26 years prior to sampling. Collective tiller area per m2 and maximum lamina length per tussock were significantly correlated with time since last fire. Using these parameters and a jack-knifing procedure, the time since the last fire for four of the 13 sites (30%) could be predicted within 3 years. The predictions were not improved by adding altitude as a factor. The time since the last fire for the most recently burnt sites or those burnt more than 25 years previously could not be predicted by any of the tussock or tiller characteristics. In montane and subalpine tussock grassland in eastern Otago, burnt tussocks, under low intensity pastoralism, are estimated to take 15–20 years to reach a state similar to that of tussocks which had not been burnt for at least 25 years. Grazing of recently burnt tussocks severely retards their recovery from fire.

Seedling establishment characteristics of alternative legume species in tussock grassland environments

Four alternative legume species, Caucasian clover (Trifolium ambiguum), zigzag clover (T. medium), crown vetch (Coronilla varia), and birdsfoot trefoil (Lotus corniculatus), were compared with white clover (T. repens) on four tussock grassland sites. Seed was inoculated and pelleted, and then oversown at a rate equivalent to 5 kg/ha viable seed. Germination, nodulation and survival of white clover, Monaro Caucasian clover, and zigzag clover were similar on the two lowest sites (600 and 830 m). However, low rates of zigzag clover germination occurred on the two higher sites (1090 and 1100 m). Germination of crown vetch appeared to be prevented or delayed by the low temperatures, and no plants established on any site. Low nodulation occurred in Treeline Caucasian clover and birdsfoot trefoil. Further research is required to select more suitable strains of rhizobia for both these legumes. The results provide information for estimating likely plant densities of these new cultivars when oversown in tussock grassland environments. Keywords Coronifla varia, establishment, germination, inoculation, Lotus corniculatus, nodulation, Trifoliumambiguum, Trifolium medium, Trifolium repens

Field trials assessing the effect of inoculating agricultural soils with endomycorrhizal fungi

SummaryFour field experiments were established to gauge the effect of inoculating white clover with selected strains of vesicular-arbuscular mycorrhizal (VAM) fungi. The four sites chosen ranged in fertility from undeveloped, phosphorus-impoverished tussock grassland to high fertility alluvial flats. As far as practicable conventional agronomic practices were followed prior to and during sowing. The soils were otherwise untreated and contained the normal complement of indigenous VAM fungi. Infested soil pellets were used to introduce the fungi into the soils as this was considered more appropriate to pastoral farming than for example transplanting infected seedlings.Initially the introduced fungi tended to have little or no effect on dry-matter yields but by the end of the first season there were significant responses to Gigaspora margarita, Glomus mosseae, Glomus macrocarpum or a mixed inoculum of Glomus pallidum and Glomus tenue. In the second season, dry-matter yields were increased on the two tussock grassland sites by up to 760 kg D.M./ha (ca. 30%), 825 kg D.M./ha on the moderately fertile site (14%) and 640 kg D.M./ha (5%) on the high fertility site. The growth responses tended to decrease with time probably owing to the spread of fungi from the inoculated to the control plots though growth responses were still present at the end of the 3rd year on two of the sites. Within each experiment the application of up to 50 kg P/ha per year did not reduce the size of the responses to inoculation. This and herbage chemical analyses suggested that a more efficient use of phosphatic fertilizers may have been only part of the reason for the responses to inoculation.

Influence of site on response of ‘Grasslands Maku’Lotus pedunculatusestablishment to seed pelleting and broadcast lime

Abstract The effects of seed pelleting and broadcast lime on the establishment of overs own ‘Grasslands Maku’, Lotus pedunculatus Cav., were investigated on a range of tussock grassland sites with pHs varying from 4.4 to 4.8 and devoid of lotus rhizobia. The addition of 10070 gum arabic to the peat inoculant slurry increased the percentage of nodulated plants on all sites. Pelleting the inoculated seed with rock-phosphate dolomite further increased nodulated plants on the 3 most acid sites (pH 4.4-4.5) in the absence of broadcast lime. With slurry inoculation treatments there was a consistent response to lime broadcast at 500 kg/ha over the pH range 4.4-4.6 but in the presence of rock-phosphate dolomite pelleting the increase in nodulated plants from broadcast lime was only apparent on 2 of these sites. Seed treatments in the present experiment were prepared 1 day before sowing. The use of seed pelleting to maximise the establishment of Maku lotus on the more acid soils cannot be recommended until pellets having satisfactory survival of rhizobia during the longer storage periods experienced under practical farming conditions have been developed and evaluated.

Distribution survey of soil insects at Millers Flat, Central Otago

Abstract A soil-sampling survey carried out between 100–900 m altitude in the Millers Flat area of Central Otago investigated pasture type preferences and altitude range of the main pasture pests. Costelytra zealandica (White) was commonly found at high densities up to 600 m, particularly in cultivated pastures. Odontria striata White showed no pasture type preferences but was most common at 460–600 m altitude. Pyronota spp. were common in tussock grassland sites above 600 m, a habitat to which tipulid larvae and cicada nymphs were almost exclusively restricted. Wiseana spp. were most numerous at 300–600 m, the zone in which most new pasture development by cultivation had taken place within the previous 5 years; undeveloped tussock sites supported lower numbers. Root-feeding weevil larvae were common, often at high densities.

FACTORS AFFECTING THE RESPONSE OF CLOVER ESTABLISHMENT TO INOCULATION AND PELLETING

Results of trials evaluating the effectiveness of different inoculation and pelleting techniques on the establishment of clovers oversown in tussock grassland sites are discussed. These trials were carried out simulating as far as possible the practical applications. Response to inoculation and pelleting varied with environmental conditions (e.g., altitude, soil acidity and vegetative cover), time of sowing, and populations of rhizobia in the soil. On some soils, clover established reasonably Erom inoculated seed, while on some acid soils effective pelleting of inoculated seed was essential. Environmental conditions influenced the standards required for inoculants and pelleted seed. The importance of field testing in addition to laboratory testing is stressed.

Variation in soil pH under tussock grassland species

Abstract Three tussock grassland sites were sampled along a climatic-soil gradient in the Mackenzie Basin, South Canterbury. There was a range within sites of 0.5 pH units in the 1-5 cm soil layer beneath different species. The pH was highest beneath composite flatweeds and Rumex acetosella and lowest below Festuca novae-zelandiae.

An investigation and survey of insect damage affectingChionochloaseed production in some alpine tussock grasslands

Abstract Thirty-thousand florets from 5 Chionochloa species (Gramineae: Arundinoideae) were examined for insect damage in a survey of 22 alpine tussock grassland sites in the South Island. The five tall lussock species are C. flaveseens, C. maera, C. pallens, C. rigida, and C. rubra, and the investigation of floret damage was in two parts: (a) an annual assessment of seed damage over 5 years (1969–73) at one site; (b) a survey and assessment of seed damage at 21 further sites in 1 year only (1970). Three insect species were recorded feeding in florets: Megaeraspedus ealamogonus (Lepidoptera: Gelechiidae), Diplotoxa neozelandiea (?) (Diptera: Chloropidae), and an unidentified gall midge (Diptera: Cecidomyiidae). Larvae of the first two species feed on the developing ovary, and were shown to be capable of severely reducing seed production, at times causing 100% destruction in localised areas. At least in some grasslands, the occurrence of empty florets without any discernible trace of insect damage was shown to be caused by larval feeding by the moth M. ealamogonus. Little is known of the feeding hehaviour and damage caused by the gall midge, but empty florets and shrivelled seed were frequently abundant in grasslands where the midge was present. I t is concluded that consistently high levels of damage over sequences of flowering years might affect Chionochloa regeneration.

A survey and assessment of grasshoppers as herbivores in the South Island alpine tussock grasslands of New Zealand

Abstract A detailed assessment of grasshopper grazing pressures has been made for 10 alpine tussock grassland sites throughout the South Island of New Zealand. All sites were selected as reputedly high-density sites based on questionnaire returns from 61 observers, and a capture-recapture census of adult grasshoppers was made at each site. Standardised census procedures and timing permitted sites to be compared with a reference site where species biologies and population behaviour had been investigated in detail over a 4-year period. The comparisons were made using a behavioural grazing model that had been developed for populations at the reference site, given five major variables between survey sites: population density, consumption level of the population members, vegetation composition, percentage living ground cover, and site aspect. Variations in grazing pressure of up to 25-fold were demonstrated between sites, and these reflected the combined impact of all five variables rather than any particular one. All comparisons were necessarily calculated in relative terms, because appropriate data on vegetation productivity and the available crop are at present unavailable for any alpine tussock grasslands. However, evidence is given of the cumulative vegetation damage of low-volume grazing by grasshoppers, and this is shown to be serious in some grasslands. A general assessment of the importance of grasshoppers as herbivores is given for four classes of tussock grassland throughout the South Island.