Tussock Grassland Research Articles

Review of ecological restoration programme on subantarctic Macquarie Island: Pest management progress and future directions

Summary The establishment of exotic species of vascular flora and vertebrate fauna on subantarctic Macquarie Island since its discovery in 1810 has resulted in major changes in the biota. A management programme aims to reduce the numbers of exotic plant and animal species and assist with the recovery of pre‐existing communities and processes. This paper reviews the integrated vertebrate pests management programme on Macquarie Island since 1974 and outlines future management considerations. As part of this programme, the responses of some native and exotic species of vascular flora and vertebrate fauna were monitored following control of European Rabbit (Oryctolagus cuniculus) numbers. Changes in the vegetation recorded over 10 years showed that approximately half of all the vascular species had benefited from rabbit grazing, including several which formed a major part of the rabbit’s diet. After rabbit control, some adversely affected plants responded rapidly to a reduction in grazing pressure while others will require an almost total cessation of grazing in order to re‐establish their former distributions. With the decrease in rabbit numbers it was also necessary to control Feral Cats (Felis catus) due to their increased predation on native burrow‐nesting birds. Feral Cat predation on introduced fauna also increased, one result of which was the eradication from the island of the introduced Weka (Gallirallus australis scotti). Reduced rabbit grazing is leading to re‐establishment of the native Tall Tussock (Poa foliosa) grassland and with it the spread of the introduced Ship Rat (Rattus rattus). This review indicates that an integrated approach to pest management, with monitoring of the responses of both target and non‐target species, is the most effective way to restore pre‐existing communities and processes.Key words grazing pressure, introduced species, predation, recovery, vertebrate pest management.

Hillslope and wetland hydrodynamics in a tussock grassland, South Island, New Zealand

AbstractPrevious research on two experimental catchments at the Glendhu Forest (Otago) showed that runoff dynamics from this landscape differ substantially from other areas in New Zealand. In particular, the recession curves from these catchments have two distinct phases: a rapid decline for a period of several hours, followed by a slow decline that may last many days to weeks. In the current study, soil water matric potential measurements indicated that perched saturated zones develop very rapidly in the surface (0–30 cm) soil horizons. Deep (50–250 cm) loess horizons remain moist throughout the year and may be near or at saturation at the bedrock contact, and respond only slowly to rain events. Soils in the middle horizons are often drier than the surface soil above or the deep soils below. Throughflow measurements showed that storm runoff occurs primarily as interflow through a retentive but pervious mat of mosses, litter, and roots at the soil surface. Despite the presence of abundant earthworm burrows, less water is transmitted through the soil horizon just below this surface mat. Only a small fraction of stormflow was transmitted through the deep, mineral horizons. However, baseflow could be sustained for long periods (up to 4 weeks) from unsaturated flow of soil moisture stored in the deep loess horizons. Water storage in bog peats and associated riparian soils (which are numerous in this area) is insufficient to sustain baseflow for more than a few days. The results from this study are consistent with previous hydrometric, soils, and isotopic observations and suggest that any land‐use practices that disrupt the surface soil horizons are likely to change the runoff characteristics of this area. Copyright © 2001 John Wiley & Sons, Ltd.

High altitude C 4 grasslands in the northern Andes: relicts from glacial conditions?

The altitudinal vegetation distribution in the northern Andes during glacial time differed from the present-day conditions as a result of temperature and precipitation change. New evidence indicate that as a response to a reduced atmospheric partial CO 2 pressure ( pCO 2), the competitive balance between C 3 and C 4 plants have changed. Effects may have remained virtually undetected in pollen records, but can be observed using a stable carbon isotope analysis. Vegetation dominated by C 4 taxa, belonging to the families Cyperaceae (e.g. Bulbostylis and Cyperus) and Poaceae (e.g. Muhlenbergia, Paspalum and Sporobolus), may have been able to replace for a significant part the modern type C 3 taxa (e.g. species belonging to Carex, Rhynchospora, Aciachne, Agrostis, Calamagrostis, and Chusquea). Impact of reduced glacial atmospheric pCO 2 levels and lower glacial temperatures on the composition and the elevational distribution of the vegetation types is discussed. The present high Andean vegetation communities may differ from the glacial equivalents (non-modern analogue situation). We identified dry Sporobolus lasiophyllus tussock grassland and Arcytophyllum nitidum dwarfshrub paramo as the possible relict communities from glacial time. The effect on previous estimates of paleo-temperatures is estimated to be small.

Comparison of the flora and vegetation of the southern Andes and New Zealand

The annual range of temperatures in the southern Andes is similar to that in New Zealand, although they are cooler at comparable latitudes. South of 45°S in Chile the precipitation regime is also similar to New Zealand, but northwards and also east of the Andes there is an increasing period of Summer dryness. There are corresponding similarities in vegetation, especially in evergreen Nothofagus forests, tussock grassland in eastern rain shadows, and cushion bogs. Deciduous Nothofagus species are absent from New Zealand, but dominate widely in drier and colder environments of the southem Andes. In the southern Andes deciduous Nothofagus forms the subalpine forest and krummholz although, in the northern part of the region, there is also Araucaria araucarna growing as erect, emergent trees. Volcanic eruptions may lower the tree limit so that it intersects with evergreen Nothofagus forest. In New Zealand, evergreen Nothofagus species, which are less cold‐resistant than the deciduous Andean species, form most tree limits, and a belt dominated by tall Chionochloa tussocks intervenes between forest and low‐growing alpine vegetation. The absence of very hardy tree species in the New Zealand mountains may be related to isolation and late uplift. Extrapolation to tree limit indicates southern Andean warmest‐month mean temperatures from around 7°C in northern localities to only 5.7°C at 55°S, compared with 10°C which prevails in New Zealand. Since tree limit altitudes in the Southern Andes exceed those of New Zealand by at least 250 m, this indicates that in temperature terms New Zealand tree limits are 550 m lower than those of the southern Andes, corresponding with summer isotherms 3.3°C warmer. Vascular species were listed from equivalent vegetation types in the southern Andes and New Zealand, including forest, rain‐shadow grassland, alpine, coastal, swamp, lake‐edge and bog vegetation, and also from communities near the upper tree limit without close equivalents, notably deciduous forest in the Andes and Chionochloa grassland in New Zealand. Phytogeographic categories were assigned to all species, genera, and families. These were grouped as shared‐austral, shared with wider distributions, ‘’realm‐endemic‘’ confined to either south America or Australasia, and non‐shared with wider distributions About 90% of the 465 species listed from the southem Andes and 522 listed from New Zealand are realm‐endemics. Forty species or closely related pairs of species are shared, nearly half of these being coastal. Among genera, realm‐endemics are the largest element overall and exceed 30% in forests of both regions and in New Zealand subalpine, grassland, alpine, successional, and bog vegetation. Shared genera that extend to north temperate regions form the next most important, reaching over 40% in southern Andean swamp and New Zealand coastal samples. Shared genera with austral distributions reach 21–32% in all New Zealand vegetation classes and southern Andean bog, compared with 5–20% in other southern Andean vegetation classes. They contribute disproportionately to the physiognomic similarities between the two regions, notably in Nothofagus forests and bogs. Non‐shared genera with austral or subtropical distributions are most numerous in forest samples from each region. Non‐shared genera with north temperate distributions constitute only 2% in New Zealand, contrasting with the southern Andes where they constitute 19% overall and 20–29% in subalpine, grassland, alpine, successional, and coastal vegetation. Distribution of families among phytogeographic categories is similar to that of genera, except that more are shared‐widespread and fewer are shared‐austral and realm‐endemic. Sequencing of the gene rbcL for pairs of taxa in shared‐austral genera and for populations of Hebe salicfolia yields divergence estimates ranging from 130 ± 75 to 7 ± 4 million years. Divergences among tree species in shared genera may predate the separation of Australasia from Antarctica and South America, but not the separation of New Zealand from Australia. Taxa of open habitats show the most recent divergences, and their presence in both regions demands some mode of transoceanic dispersal. Possibly as late as the Pliocene, this may have involved a partly vegetated Antarctica.

Behaviour of the static pressure around a tussock grassland–forest interface

A field experiment was executed to measure static pressure differences around a forest edge. So-called ‘Quad-Disks’ were used to measure static pressure unaffected by the dynamic pressure induced by the probe itself. Flow obliquity appeared to have little influence on the results. For a smooth to rough transition, the results showed a maximum pressure difference within the forest at x=0.6 h relative to the probe at x=−4 h, where the height of the forest h=25 m. For a rough to smooth transition the normalised pressure differences were only weak. A maximum pressure difference was found just outside the forest at x=0.6 h relative to the probe at x=4 h probably related to a reattachment point. A negative pressure was present at the probe at x=−4 h.

Status of white-chinned petrels Procellaria aequinoctialis Linnaeus 1758, at Bird Island, South Georgia

The white-chinned petrel (Procellaria aequinoctialis) is an abundant, widespread petrel breeding in tussock grassland at sub-Antarctic islands. Over the last decade it has been killed in large numbers in temperate and sub-tropical longline fisheries. However no data are available on the global population status. We assessed the status of white-chinned petrels at Bird Island, South Georgia by comparing the distribution and density of occupied burrows in 1981 and 1998. In both surveys white-chinned petrel burrows occurred in one-quarter of the 460–477 36-m2 quadrats surveyed. The total number of burrows in each quadrat was consistent between each survey but we estimate an overall decrease of 28% in those occupied (with considerable variation between sites). Concurrent data on breeding frequency and success showed that white-chinned petrels are essentially annual breeders at Bird Island; breeding success was consistent at around 44%. Significant factors determining densities of occupied burrows were crown height and percent tussock cover (accounting for 77% of variance). The former has decreased significantly, the latter increased significantly between 1981 and 1998 but there was no relationship between white-chinned petrel occupancy rate and habitat modification due to the presence of fur seals (Arctocephalus gazella). This suggests that any population decline is due to factors operating away from the breeding colony, such as those attributed to fishing.

BRDF Correction of Vegetation in AVHRR Imagery

In this article we present a method for correcting AVHRR visible and near-infrared imagery for varying satellite and solar zenith angles. This method is based on the WAK BRDF model for closed canopies. The parameters required to perform BRDF correction can be derived from consecutive pass AVHRR imagery pairs. This imagery provides two views of the land surface close together in time but with large differences in phase angle. It is reasonable to assume that both the surface and the atmosphere will change little between orbits, and that after BRDF correction reflectances of given targets should be the same in both orbits. Before BRDF parameters can be fitted, atmospheric correction must be performed. To improve this process, average monthly atmospheric profiles and aerosol optical depths are used as radiative transfer model inputs in conjunction with a digital elevation model. Using atmosphere corrected reflectance data from 12 NOAA-14 AVHRR image pairs, BRDF parameters were extracted for predominant vegetation groups in New Zealand: indigenous forest; exotic forest; scrub; pasture; and tussock grassland. For each of these vegetation groups significant non-Lambertian reflectance behavior was observed, and BRDF correction using the derived parameters successfully minimized this variation. Measuring the spread of the corrected results from the desired equal reflectance line gives a measure of the accuracy of the method. After correction, the RMS reflectance errors were approximately 0.01 in the visible and 0.02 in the near-infrared. A vegetation map specifying the proportions of the vegetation groups at any given location can be used to perform regular BRDF correction. Reflectance standardization to a fixed view and sun angle can then be performed using the pre-derived BRDF parameters and proportional BRDF correction.

Soil organic matter transformations induced by Hieracium pilosella L. in tussock grassland of New Zealand

To study the effect of Hieracium pilosella L. invasion on the transformations of soil organic matter of New Zealand tussock grassland soils (Ustochrepts), plant material and soils underneath Hieracium, the surrounding halo, and the adjacent herbfield (depleted tussock grassland) were examined for their chemical composition. An attempt was made to reveal possible changes in chemical composition of the soil organic matter induced by H. pilosella invasion. Small differences were detected by solid-state 13C nuclear magnetic resonance (NMR) spectroscopy in the composition of the plant and soil materials from these zones. Most of the differences in soil organic matter occurred due to differences in the amount and quality of plant-residue inputs. Comparable amounts of phenolic C were detected in the solid-state 13C NMR spectra of H. pilosella and herbfield vegetation, while alkaline CuO oxidation yielded considerable lower lignin oxidation products for H. pilosella. A slightly higher proportion of these compounds in H. pilosella soil revealed an accumulation and a low degradation rate of lignin compounds under H. pilosella. The HCl hydrolysis and solid-state 15N NMR spectroscopy showed similar chemical compositions of the N fractions of the three different soils. The absence of 15N NMR signal intensity assignable to aniline derivatives or aromatic heterocyclic N indicates that the condensation of phenolic compounds with N groups plays a minor role in N sequestration in these soils.

Close-Range Vertical Photography for Measuring Cover Changes in Perennial Grasslands

We describe a method of close-range vertical photography and digital image analysis for measuring changes in total projective cover in perennial tussock grasslands of semi-arid Australia. Repeated photographs of permanent plots (1 m 2 ) were classified using supervised image analysis, providing a clear and objective record of the effects of single-burns on grass cover relative to controls. Computer simulations of the photographic set-up indi cated that errors due to camera perspective were consistently less than 4% across a range of cover classes. Other errors, including misclassification error, were not quantified because simplified laboratory tasks indicated that conventional field methods, such as point sampling and visual estimation, provided unreliable esti mates of grass cover and were therefore not suitable benchmarks for assessing the photographic method. However, the presented data indicate that the photographic method was sufficiently accu rate and precise to measure treatment effects over time and to elucidate relationships between independent growth parameters across a range of cover conditions. In addition, the photographic method was inexpensive, involved minimal field time, and utilised commercial software to classify images. It has the clear advantage over more traditional methods of providing outputs that are readily archived for retrospective studies.

Rodents of the arid Northern Territory: conservation status and distribution

At the time of European entry, 18 species of rodent occurred in the arid zone of the Northern Territory, including two endemic species, Zyzomys pedunculatus and Pseudomys johnsoni. The tally is somewhat inflated, as the arid Northern Territory is on the margins of the distribution for seven of these species. The historical record for this fauna is generally reasonably good, due to important collections around the end of the nineteenth century, some landmark studies (notably by H.H. Finlayson) earlier this century, documentation of Aboriginal knowledge, and the recent discovery and analysis of fossil and sub-fossil deposits. Notwithstanding this good historical baseline, recent research has added three native species to the fauna, and re-discovered one species, Z. pedunculatus, earlier feared extinct. Over the last 200 years, four species (Leporillus apicalis, Notomys amplus, N. longicaudatus and Pseudomys fieldi) have disappeared, and a further five species (N. cervinus, N. fuscus, P. australis, Rattus tunneyi and Z. pedunculatus) have declined considerably, with several of these perhaps no longer present in the area. The decline in this rodent fauna is matched, or indeed surpassed, by declines in the arid-zone bandicoots, small macropods and large dasyurids. But notably the small dasyurids have generally suffered few declines. There has been differential decline within the rodent fauna, with declines mainly affecting larger species, species with the most idiosyncratic diets, and species occurring mainly in tussock grasslands and gibber plains. The main conservation and management actions required to safeguard what is left of this fauna are carefully targetted studies examining the effect of threatening processes, complemented by landscape-wide amelioration of these threats. Additional autecological studies are also needed for some species, and some exceptionally poorly known areas should be surveyed. Current work examining the distribution, ecology and management requirements of the endangered Z. pedunculatus is a major priority.

Vegetation of the Wessel and English Company Islands, North-eastern Arnhem Land, Northern Territory, Australia

Vegetation patterning is described for two neighbouring continental island chains off Arnhem Land, Australia. A total of 684 species was recorded from 57 islands, with reasonably comprehensive lists for 36 of these islands. Almost 90% of the deviance in plant species richness was associated with island size. The richness of plants dispersed by sea and/or vertebrates was proportionally greater on small islands; that of relatively poor dispersers was greater on larger islands. Twelve vegetation communities were defined by classification of plant species composition in 226 50 × 50-m quadrats. There was no relationship between island size and species richness at the quadrat level, at least for the most extensive vegetation types. The vegetation of the islands is now composed of two main elements—an original set of communities (mostly of heath, tussock grassland and eucalypt open forest) whose species have poor inter-island dispersal, and a set of more recent colonists (mostly of strand, mangrove and coastal thicket communities). The former group is allied to the sandstone flora of western Arnhem Land, but is species-poor in comparison, as the islands lack the deep gorges which drive much of the species richness of western Arnhem Land. The latter group comprises many species with a broad geographic range across tropical coastal areas, including many species which have been shown elsewhere to be highly vagile. Many species of the former set appear to have been lost from the smaller islands. The island flora has been influenced by three sets of human managers. Aboriginal use of the islands has been long-standing and probably resulted in a fire regime which may have accentuated environmental patchiness. Centuries of wet-season use of some islands by Macassan trepang-harvesters, ending early this century, has apparently left few effects other than the persistence of occasional small populations of an introduced food tree. In contrast, European use of these islands has been minimal and fleeting, but is associated with the introduction of most weeds.

Nowhere Spelled Backwards: The Quest for Region in the Tussock Grasslands of New Zealand

Nowhere Spelled Backwards: The Quest for Region in the Tussock Grasslands of New Zealand

Vegetation change and soil quality in central Otago tussock grasslands, New Zealand.

Vegetation change and soil quality in central Otago tussock grasslands, New Zealand.

Close-range vertical photography for measuring cover changes in perennial grasslands

We describe a method of close-range vertical photography and digital image analysis for measuring changes in total projective cover in perennial tussock grasslands of semi-arid Australia. Repeated photographs of permanent plots (1 m2) were classified using supervised image analysis, providing a clear and objective record of the effects of single-burns on grass cover relative to controls. Computer simulations of the photographic set-up indicated that errors due to camera perspective were consistently less than 4% across a range of cover classes. Other errors, including misclassification error, were not quantified because simplified laboratory tasks indicated that conventional field methods, such as point sampling and visual estimation, provided unreliable estimates of grass cover and were therefore not suitable benchmarks for assessing the photographic method. However, the presented data indicate that the photographic method was sufficiently accurate and precise to measure treatment effects over time and to elucidate relationships between independent growth parameters across a range of cover conditions. In addition, the photographic method was inexpensive, involved minimal field time, and utilised commercial software to classify images. It has the clear advantage over more traditional methods of providing outputs that are readily archived for retrospective studies.

Plant effects on soil carbon storage and turnover in a montane beech (Nothofagus) forest and adjacent tussock grassland in New Zealand

Land cover is a critical factor that influences, and is influenced by, atmospheric chemistry and potential climate changes. As considerable uncertainty exists about the effects of differences in land cover on below-ground carbon (C) storage, we have compared soil C contents and turnover at adjacent, unmanaged, indigenous forest (Nothofagus solandri var. cliffortiodes) and grassland (Chionochloa pallens) sites near the timberline in the same climo-edaphic environment in Craigieburn Forest Park, Canterbury, New Zealand. Total soil profile C was 13% higher in the grassland than in the forest (19.9 v. 16.7 kg/m2 ), and based on bomb 14C measurements, the differences mainly resulted from more recalcitrant soil C in the grassland (5.3 v. 3.0 kg/m2 ). Estimated annual net primary production was about 0.4 kg C/m2 for the forest and 0.5 kg C/m2 for the grassland; estimated annual root production was about 0.2 and 0.4 kg C/m2 , respectively. In situ soil surface CO2 -C production was similar in the grassland and the forest. The accumulation of recalcitrant soil C was unrelated to differences in mineral weathering or soil texture, but was apparently enhanced by greater soil water retention in the grassland ecosystem. Thus, contrary to model (ROTHC) predictions, this soil C fraction could be expected to respond to the effects of climate change on precipitation patterns. Overall, our results suggest that the different patterns of soil C accumulation in these ecosystems have resulted from differences in plant C inputs, soil aluminium, and soil physical characteristics, rather than from differences in soil mineral weathering or texture.

Changes in soil microbial biomass, metabolic quotient, and organic matter turnover under Hieracium ( H. pilosella L.)

In New Zealand Hieracium is an opportunistic plant that invades high country sites more or less depleted of indigenous vegetation. To understand the invasive nature of this weed we assessed the changes in soil C, N and P, soil microbial biomass C, N and P contents, microbial C : N and C : P ratios, the metabolic quotient, and turnover of organic matter in soils beneath Hieracium and its adjacent herbfield resulting from the depletion of tussock vegetation. The amounts of soil organic C and total N were higher under Hieracium by 25 and 11%, respectively, compared to soil under herbfield. This change reflects an improvement in both the quantity and quality of organic matter input to mineral soil under Hieracium, with higher percentage organic C and a lower C : N ratio. The microbial biomass C, N and P contents were also higher under Hieracium. The amount of C respired during the 34-week incubation indicated differences in the nature of soil organic matter under Hieracium, the unvegetated "halo" zone surrounding Hieracium patches, and herbfield (depleted tussock grassland). Decomposition of organic matter in these zones showed that the Hieracium soil had the greatest rate of CO2 respired, and the halo soil had the lowest. We relate the enhanced organic C turnover to the invasive nature of Hieracium. Net N mineralization was significantly lower from the Hieracium soil (57 mg N g–1 soil N) than from herbfield and halo soils (74 and 71 mg N g–1 soil N, respectively), confirming that the nature of organic N in Hieracium soil is different from adjoining halo and herbfield soils. It seems plausible that specific compounds such as polyphenols and lignins released by Hieracium are not only responsible for increased organic N, but also control the form and amount of N released during organic matter transformations. We conclude that the key to the success of Hieracium in the N-deficient South Island high country of New Zealand lies in its ability to control and sequester N supply through modifying the soil organic matter cycle.

EFFECTS OF LAND USE ON STREAM METABOLISM AND ORGANIC MATTER TURNOVER

We measured ecosystem metabolism and organic matter transport seasonally in five streams draining catchments dominated by native forest, exotic pine plantation, grazed tussock grassland, or developed pasture. All streams are tributaries of the Taieri River in southeastern New Zealand. Whole-stream metabolism was estimated by both two-station and single-station open-channel methods, allowing comparison between these techniques. Transfer of oxygen across the stream surface was estimated using reaeration coefficients determined from three different procedures: tracer gas injections (propane), analysis of the oxygen record, and empirical velocity–depth equations. Measurements of gross primary production (GPP) and community respiration (CR) showed differences among streams that reflected method rather than ecosystem process. The ratio of GPP:CR and net ecosystem metabolism, however, showed strong concordance among methods, suggesting that bias involved in standardizing estimates to areal units may be more impo...

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.

Alternative Classifications in the Intrinsic Guild Structure of a New Zealand Tussock Grassland

Guild structure was determined in the inter-tussock vegetation of a New Zealand grassland. Twenty-one sites were sampled by shoot presence/absence in 10 × 10 cm quadrats. for all macroscopic plants. Using these data, intrinsic guilds were derived (intrinsic guilds are those that are defined by the observed restrictions on species co-occurrence, not by a priori characters). Such guilds were found by heuristic searches for the guild classification that was optimal, as measured by an index of community structure, RV gp . The optimisation was for minimum RV gp . i.e. maximum guild proportionality, relative constancy in guild representation. One hundred searches were carried out on the data, each starting from a different initial random configuration. When the quadrats were split at random into an Optimisation subset and a Test subset, a guild classification that showed significant guild proportionality in the Test subset was found in a significantly greater number of searches than expected by chance (28 out of 100). The ten of those 28 classifications that gave the tightest community structure comprised three groups. Further optimisation of representatives of these groups using the whole dataset confirmed that the community contained at least two genuinely independent, alternative guild classifications. It is concluded that two or more guild classifications can exist within the same set of species in a community. These classifications can be orthogonal in the sense that they are unrelated to each other and operate simultaneously. Attempts to correlate the demonstrated guild membership with known characteristics of the species showed some, but limited, relation to growth form height.

The influence of prey distribution on the foraging strategy of the lizard Oligosoma grande (Reptilia: Scincidae)

The grand skink, Oligosoma grande, is a diurnal rock-dwelling lizard from the tussock grasslands of Central Otago, New Zealand, whose diet includes a variety of arthropods and fruit. We conducted a field experiment to examine the influence of prey distribution on foraging behavior and spacing patterns. On sites where prey distribution was unaltered (control sites), males and females differed in diet and foraging behavior. Most male feeding attempts were directed at large strong-flying insects, and males used a saltatory search pattern that involved relatively infrequent moves of long duration. Females spent more effort catching small weak-flying insects and visiting fruiting plants. Their search behavior involved frequent moves of short duration. The placement of meat-bait on experimental sites led to a redistribution of large flies without influencing other prey types. Experimental females switched foraging strategy by adopting a search pattern of relatively infrequent moves of long duration, increasing the frequency of attempts to capture large prey, and reducing the importance of fruit in their diet. The experimental manipulation appeared to influence space use. On control sites, both sexes had comparably sized home ranges. On experimental sites, male home ranges were significantly larger than female home ranges.