Tussock Grassland Research Articles

Climate, fire, farming and the recent vegetation history of subantarctic Campbell Island

ABSTRACTCampbell Island is a small, uninhabited peat-covered island lying in the cool southern ocean 600 km south of the New Zealand mainland. Dracophyllum scrub is the main cover from sea level to 200 m, above which tussock grassland, macrophyllous forbs and tundra dominate. Seven peat profiles from sea level to the tundra zone provide an elevational transect for pollen and charcoal records spanning the last 500 years. Scrub density was relatively low between 200 and 400 cal yrs BP, possibly due to Little Ice Age cooling, but had recovered by the time Europeans discovered the island in AD 1810. Burning and grazing during a brief farming episode (AD 1895–1931) severely reduced scrub and palatable grasses and forbs. Vegetation recovery is now well advanced following cessation of farming and the later elimination of all feral grazing animals, cats and rats. Climates were cool in the southwest Pacific during the farming period, and since AD 1970 the island has warmed by c. 0·5°C. However, there has been no upwards movement of the scrubline despite vigorous regeneration of scrub at lower altitudes. The island's cloudy, highly oceanic climate appears to offset increasing summer warmth, and scrubline is likely to rise only if clearer and less windy, as well as warmer, summers eventuate.

Habitat selection in the Pampa de Achala toad, Bufo achalensis

AbstractHabitat selection in adult and juvenile Bufo achalensis was studied at La Ciénaga Stream, Pampa de Achala, Central Argentina from December 1998 to October 2001. Habitat preference was evaluated by comparing the observed use of each habitat type with its availability. Juveniles were surveyed on 32 occasions between January 1999 and March 2001 using 13 permanent transects. The effect of cattle on larval survivorship was also evaluated. Most adult and juvenile B. achalensis occurred within 300 m of each side of the breeding site stream. No correlation was found between body size and distances moved. Juveniles and adults selected granite outcrops after the breeding season and avoided the heavily grazed areas. Adults also selected the stream and used tall tussock grassland in proportion to its availability. Juveniles used loose, flat, relatively small stones as shelters whilst adults used larger rocks. The presence of cattle at the breeding sites directly reduced larval survivorship by trampling, and indirectly through sediment deposition at the breeding sites resulting from increased stream bank erosion. The habitat preferences of B. achalensis suggest that long term cattle grazing also affects them adversely through deterioration of their transition habitat from tall tussock grassland to short sward. Future conservation management plans for B. achalensis must include the protection of the breeding sites and the surrounding terrestrial area if they are to be effective.

Do plant clumps constitute microbial hotspots in semiarid Mediterranean patchy landscapes?

Three semiarid Mediterranean patchy landscapes were investigated to test the existence of a microsite effect (i.e. plant canopy vs. inter-canopy) on soil microbial communities. Surface soil samples were independently taken from both microsites under naturally changing conditions of humidity and temperature through the year. In gypsiferous soils covered with a shrub steppe, improved physical and chemical soil properties were registered underneath the plant canopy, where the densest and most active microbial communities were also detected (e.g. microbial biomass C averaged 531 and 202 mg kg −1 in canopy and inter-canopy areas, respectively). In calcareous perennial tussock grasslands, either growing on soils over limestones or alluvial deposits, the microsite effect was not so marked. Soil humidity, temperature and total organic C were homogeneously distributed over the landscape conditioning their uniform microbial activity under field moisture conditions (ATP content averaged 853 and 885 nmol kg −1 in canopy and intercanopy areas, respectively). However, readily mineralizable C and microbial biomass C were preferentially accumulated in soils underneath the tussocks determining their larger potential microbial activity (e.g. C hydrolysis capacity under optimal conditions). In conclusion, plant clumps either functioned as microbial hotspots where enhanced microbially driven ecosystem processes took place or as microbial banks capable of undergoing a burst of activity under favourable climatic conditions. Our results provide experimental evidence of a non-patchy distribution of certain soil microbial properties in semi-arid Mediterranean patchy ecosystems.

Impacts of fine sediment addition to tussock, pasture, dairy and deer farming streams in New Zealand

Summary1. Increased fine sediment input caused by agricultural development is expected to act as a stressor for stream ecosystems. In a large‐scale field experiment, we added fine river sand to 50‐m reaches of three second‐order streams in each of four categories of catchment development (ungrazed tussock grasslands, grazed pasture, dairying and deer farming) and measured the responses of macroinvertebrates and aquatic moss.2. Before addition, fine sediment cover differed between land uses, being lowest in tussock (7%), intermediate in pasture (30%) and dairy (47%) and highest in deer streams (88%). Sediment addition increased cover by one land‐use category (e.g. augmented sediment cover in tussock streams was similar to pre‐existing cover in pasture streams), and cover remained high in impact reaches (compared with controls) throughout the 5‐week experiment. Sediment addition did not change concentrations of phosphate, nitrate and ammonium, which were generally highest in dairy streams and lowest in tussock streams.3. Aquatic mosses (most common in tussock, absent in dairy and deer), invertebrate density (highest in deer, lowest in tussock), taxon richness (highest in pasture, lowest in deer) and diversity (highest in pasture and tussock, lowest in dairy and deer) all differed between land uses. Sediment addition resulted in reductions of moss cover, invertebrate taxon richness and richness of Ephemeroptera, Plecoptera and Trichoptera in impact relative to control reaches.4. The impact of sediment addition was strongest in pasture streams where pre‐existing sediment cover was moderate and richness and diversity of the invertebrate community highest. However, even in the already sediment‐rich and species‐poor deer streams, density of one common taxon was reduced significantly by sediment addition, and another two were affected in the same way in dairy streams, the second‐most intense land use.5. Our experiment has disentangled the impact of sediment addition from other concomitant land‐use effects that could not be reliably distinguished in previous research, which has mainly consisted of correlative studies or unrealistically small‐scale experiments.

Linking Land-use, Water Body Type and Water Quality in Southern New Zealand

Land-use and vegetation cover have been linked to the nutrient levels (nitrogen, phosphorus) of surface waters in several countries. However, the links generally relate to streams and rivers, or to specific types of standing water, for example shallow lakes in a geologically defined region. We measured physical variables and nutrient chemistry of 45 water bodies representative of the wide range of lentic wetland environments (swamps, riverine wetlands, estuaries, reservoirs, shallow lakes, deep lakes) in Otago, New Zealand, and related these to catchment variables and land-use in order to assess the potential influence of catchment modification on water quality of these diverse wetlands. Catchment boundaries and land cover were derived from maps using ArcView GIS software. Our predictions that concentrations of nutrients and other components of water quality would correlate positively with the nature and intensity of catchment modification were confirmed in multivariate analyses. Physical and chemical measures were positively related to the extent of modification in the catchment (percentage of the catchment in pasture, planted forest, scrub and urban areas), and negatively related to lack of catchment modification (more of the catchment in bare ground, tussock grassland and indigenous forest). The strong negative correlations between nutrient concentrations, suspended sediment, water colour and the percentage of tussock cover in the catchment imply that increased conversion of the␣native tussock grassland to pastoral farming in␣Otago will increase nutrient concentrations and␣reduce water quality of the diverse lentic ecosystems.

Effect of Fire on Microarthropods in New Zealand Indigenous Grassland

Indigenous tussock grassland in New Zealand has a history of extensive pastoralism, and burning has been used to remove litter to improve establishment of aerially oversown pasture species and to promote palatable tussock growth for livestock. In recent years, considerable areas of tussock grassland have been retired from grazing and formally protected. Conservation land managers, as well as farmers, require information on the impacts of both managed burns carried out in spring and accidental fires that usually occur in warmer, drier conditions in summer. This study investigated the impact of spring and summer tussock grassland burning on the predominant soil microarthropods, Collembola and Acari, at 2 sites in Otago, in the South Island of New Zealand. Quantitative sampling was carried out before and for up to 26 months after burning replicated 1-ha plots. Total density of microarthropods in unburnt plots covered a similar range at both sites with an average over 3 years of about 18 000‐ 20 000 � m � 2 at each site. Both sites shared a dominance of Mesostigmata and Oribatida (Acari) and Isotomidae (Collembola). Burning in spring reduced densities of Oribatida after treatment at both sites for the duration of the study. However, after initial postburn reductions in density, populations of Isotomidae and Poduroidea (Collembola) recovered in the second year after burning. Prostigmata (Acari) appeared to be unaffected by fire. The effects of spring and summer grassland fires on microarthropod densities were rarely different. It was concluded that longer-term sampling would be required to observe the full recovery period for microarthropod populations after fire but that results from this study indicate rapid recovery of some microfaunal populations after fire, which is not strongly influenced by seasonal effects.

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.

Nitrogen and boron fertiliser effects on Hieracium pilosella infestation

Foliar sprays of different nitrogen compounds promoted rather than inhibited Hieracium pilosella in the weeks following spray application on undeveloped tussock grassland. Continued annual granular applications promoted general vegetation growth to the detriment of H. pilosella in the absence of grazing. Single applications of boron at high rates had specific adverse effects on H. pilosella for up to 4–5 years, and possibly promotive effects on short‐term grasses.

Effect of Fire on Microarthropods in New Zealand Indigenous Grassland

Indigenous tussock grassland in New Zealand has a history of extensive pastoralism, and burning has been used to remove litter to improve establishment of aerially oversown pasture species and to promote palatable tussock growth for livestock. In recent years, considerable areas of tussock grassland have been retired from grazing and formally protected. Conservation land managers, as well as farmers, require information on the impacts of both managed burns carried out in spring and accidental fires that usually occur in warmer, drier conditions in summer. This study investigated the impact of spring and summer tussock grassland burning on the predominant soil microarthropods, Collembola and Acari, at 2 sites in Otago, in the South Island of New Zealand. Quantitative sampling was carried out before and for up to 26 months after burning replicated 1-ha plots. Total density of microarthropods in unburnt plots covered a similar range at both sites with an average over 3 years of about 18 000- 20 000 m2 at each site. Both sites shared a dominance of Mesostigmata and Oribatida (Acari) and Isotomidae (Collembola). Burning in spring reduced densities of Oribatida after treatment at both sites for the duration of the study. However, after initial postburn reductions in density, populations of Isotomidae and Poduroidea (Collembola) recovered in the second year after burning. Prostigmata (Acari) appeared to be unaffected by fire. The effects of spring and summer grassland fires on microarthropod densities were rarely different. It was concluded that longer-term sampling would be required to observe the full recovery period for microarthropod populations after fire but that results from this study indicate rapid recovery of some microfaunal populations after fire, which is not strongly influenced by seasonal effects.

Aspects of the ecology of swamp antechinus (Antechinus minimus maritimus) on a Bass Strait island

The swamp antechinus (Antechinus minimus maritimus) is a small insectivorous marsupial inhabiting closed heath and tussock grassland in south-eastern Australia. The species is considered ‘Near Threatened’ on the Australian mainland. Populations persist on coastal islands off Wilsons Promontory, but their current status is unknown. This study investigated the density, diet and reproduction of the swamp antechinus on Kanowna Island. Data were collected by live trapping in different vegetation types during four trips between August 2003 and January 2004. Higher animal densities (47–129 ha–1) were found for Kanowna Island than for previously studied mainland populations (1–18 ha–1). Examination of scats showed that this species eats a wide variety of prey types, with moth larvae a major dietary component, particularly during the breeding season. Births were estimated to have occurred between 28 June and 8 August, which is a longer period than reported for other populations of this species. Factors including reduced predation, restricted dispersal and increased food availability may be responsible for supporting this dense population.

Breeding of the Grey Petrel (Procellaria cinerea) on Macquarie Island: population size and nesting habitat

Breeding of the Grey Petrel (Procellaria cinerea) was confirmed on Macquarie Island, with 26 colonies located, and unconfirmed nesting activity found at two additional localities. Colonies comprised from one to 12 burrows in which nesting was confirmed, with the total number of burrows in which nesting confirmed for all colonies combined ranging from eight in 2000 to 59 in 2003. The total number of active burrows with breeding not confirmed in all colonies combined ranged from 58 in 2001 to 54 in 2002 and 21 in 2003. The total number of fledged chicks ranged from six (2000) to 20 (2002), with a success rate of 75% in 2000 and 80% in 2002. Breeding success declined in 2003 to 32%. Factors accounting for nest failure are discussed. Colonies were located in Poafoliosa tussock grassland on steep seaward-facing (n = 26) or near-coastal slopes (n = 2) in deep soil with little surface rock. Five environmental variables determined colony location. Numbers of burrows increased with increasing depth of soils and on distinct spur-crests with a westerly aspect. Increased breeding success at higher altitude was related to decreased Black Rat activity. Uncertainty in our estimation of the size of the breeding population on Macquarie Island was caused by the high proportion of burrows in which breeding could not be confirmed. However, based on numbers of burrows for which nesting confirmed, a minimum breeding population of 59 pairs was present in 2003. If unconfirmed nesting burrows are included, the breeding population of Grey Petrels on Macquarie Island was probably 79 and 80 pairs in 2002 and 2003 respectively.

Floristic heterogeneity of flooding Pampa grasslands: a multi-scale analysis

The present paper describes vegetation heterogeneity at contrasting spatial scales in order to analyse patterns of floristic diversity and vegetation – environment relations in the Flooding Pampa grasslands of Argentina. The overall grassland flora contains a large proportion of exotic species, which are mostly annual forbs. At a regional scale, there is a latitudinal turnover in relative abundance of major grass tribes, and C3 grasses become increasingly common in grasslands at higher latitudes. The principal gradients in overall vegetation composition were associated with landscape-level changes in topography and soil chemistry. Both native and exotic species richness increased with topographic elevation, and markedly decreased in flood-prone habitats with acidic or saline soils. In remnants of tussock grassland, the predominant physiognomy of the Pampas in pre-settlement times, the presence of the tall native grass Paspalum quadrifarium is a strong determinant of local community structure, reducing the percentage of exotic species. Heterogeneity analysis at the community scale revealed a fine-grained species packing that was in sharp contrast with spatial mosaics observed in other grasslands under livestock grazing. At this scale, spatial variation in floristic composition correlated with changes in various soil parameters, but not with subtle differences in topographic relief. The studied grasslands possess some unique features that contribute towards a better understanding of how current vegetation heterogeneity is controlled by historical, environmental and management factors.

Carbon dioxide and methane exchange of a north‐east Siberian tussock tundra

AbstractCarbon dioxide, energy flux measurements and methane chamber measurements were carried out in an arctic wet tussock grassland located on a flood plane of the Kolyma river in NE Siberia over a summer period of 155 days in 2002 and early 2003. Respiration was also measured in April 2004. The study region is characterized by late thaw of the top soil (mid of June) and periodic spring floods. A stagnant water table below the grass canopy is fed by thawing of the active layer of permafrost and by flood water. The climate is continental with average daily temperature in the warmest months of 13°C (maximum temperature at midday: 28°C by the end of July), dry air (maximum vapour pressure deficit at midday: 28 hPa) and low rainfall of 50 mm during summer (July–September). Summer evaporation (July–September: 103 mm) exceeded rainfall by a factor of 2. The daily average Bowen ratio (H/LE) was 0.62 during the growing season. Net ecosystem CO2 uptake reached 10 μmol m−2 s−1 and was related to photon flux density (PFD) and vapour pressure deficit (VPD). The cumulative annual net carbon flux from the atmosphere to the terrestrial surface was estimated to be about −38 g C m−2 yr−1 (negative flux depicts net carbon sink). Winter respiration was extrapolated using the Lloyd and Taylor function. The net carbon balance is composed of a high rate of assimilation in a short summer and a fairly large but uncertain respiration mainly during autumn and spring. Methane flux (about 12 g C m−2 measured over 60 days) was 25% of C uptake during the same period of time (end of July to end of September). Assuming that CH4 was emitted only in summer, and taking the greenhouse gas warming potential of CH4 vs. CO2 into account (factor 23), the study site was a greenhouse gas source (at least 200 g Cequivalent m−2 yr−1). Comparing different studies in wetlands and tundra ecosystems as related to latitude, we expect that global warming would rather increase than decrease the CO2‐C sink.

Delimitation of the alliances Caricion firmae (Seslerietalia albicantis) and Seslerion juncifoliae (Seslerietalia juncifoliae) in the southeastern Alps and Dinaric mountains

A syntaxonomic and phytogeographic delimitation of the calcareous open sedge swards in the alpine belt of the Alps (Caricion firmae) and subalpine and alpine tussock grasslands in wind-exposed habitats (Seslerion juncifoliae) in the area of the south-eastern Alps and of the Dinaric mountains was performed. Analyses based on hierarchical classification, ordination and chorology clearly showed the distinction between the syntaxa: stands from the Liburnian karst (Mt Snežnik – SW. Slovenia, Mts Risnjak and Snježnik – NW. Croatia), Lička Plješivica and the Velebit mountains belong to the Dinaric alliance Seslerion juncifoliae, whereas stands from the Trnovski gozd plateau (W. Slovenia, north-westernmost part of the Dinaric mountains), although somewhat transitional between the two alliances, and stands from the Alps, were classified in the alliance Caricion firmae. The alliance Seslerion juncifoliae of the Dinaric mountains vicariates Caricion firmae of the Alps.

Predicting bryophyte diversity in grassland and eucalypt‐dominated remnants in subhumid Tasmania

AbstractAim To determine the environmental factors associated with bryophyte diversity in remnants in a fragmented, agricultural landscape.Location Eighty‐two remnants of tussock grassland, eucalypt woodland and eucalypt forest in the subhumid Midlands region of Tasmania, Australia.Methods Remnants were surveyed for bryophytes and predictor variables, such as vascular plant cover, climate, and topography. Management histories for each remnant were compiled using both site observation and landowner surveys. Bryophyte cover, richness, and composition were related to the independent variables using simple correlation and general linear models.Results We found weak relationships between the dependent variables and the fragmentation variables (remnant area, remnant perimeter to area ratio, distance to nearest remnant, distance to nearest larger remnant, and remnant age). Instead, climatic variables were important in predicting bryophytes, in particular those affecting humidity (minimum temperature of the coldest month, precipitation). Despite extensive sheep grazing in this landscape, grazing was not correlated with bryophyte diversity. Bryophyte diversity was not explained by vascular plant richness and was only weakly explained by composition, but was predicted by the cover of vascular plants. There was greater bryophyte cover and richness and different composition where the cover of native vascular plants was lower.Main conclusions The implications of our results are that all remnants, regardless of area, age and isolation, appear to be valuable for bryophyte conservation in this highly altered landscape. Our results also suggest that the cover of the vascular plant community, rather than its diversity, holds promise as a guide to bryophyte diversity. Bryophyte composition was similar between sites and a focus on the most species‐rich sites may be the best conservation strategy in this ecosystem.

Floristic richness of three perhumid New Zealand alpine plant communities in comparison with other regions

Abstract Results are presented on vascular species richness in three representative alpine plant communities at 1040–1410 m on Mt Burns in the perhumid Fiordland region, a hotspot of alpine plant diversity, in south‐western South Island, New Zealand. Overall species richness was not dissimilar between the three communities in any of the eight plot sizes (mean values of 20.8–24.4 species in the largest plots of 100 m2), even though coefficients of floristic similarity were small (17.9; 23.5) between both low‐alpine communities (snow tussock‐shrubland and snow tussock grassland) and the high‐alpine cushion fellfield. Vascular species richness was generally similar to that in the few other oceanic New Zealand alpine communities for which data are available. The decline in richness from the low‐alpine to high‐alpine zones, revealed in more comprehensive records from two other regions with generally similar oceanic environments, was not recorded, indeed was reversed, on Mt Burns. Whether the recognized biodiversity hotspot of Fiordland has a generally richer high‐alpine flora than other regions in New Zealand needs further examination. The general pattern of alpine floristic richness in relation to elevation, in New Zealand, also prevails in most alpine regions abroad, usually under much more extreme continental environments. This pattern is usually ascribed to the associated decrease in temperature. Both the small size of the land mass and/or associated environmental conditions may be implicated but clarification awaits further data, preferably collected with standardized procedures.

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 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 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.

Effect of Vegetation Matrix on Animal Dispersal: Genetic Evidence from a Study of Endangered Skinks

Abstract: Maintaining connectivity in fragmented landscapes is a key principle of biological conservation. Although corridors are a widely accepted approach to connecting populations, their merits are still debated, and they may be impractical in many situations. A focus on management of the vegetation matrix between populations has been advocated as an alternative way to deal with habitat fragmentation and has theoretical support. We combined microsatellite DNA and demographic data to provide an empirical account of how two forms of agricultural land use affect the connectivity of insular populations of an endangered skink in southern New Zealand. The grand skink (Oligosoma grande) lives in small populations (approximately 20 individuals) on rock outcrops separated from one another by 50–150 m of inhospitable matrix vegetation (either native tussock grassland or exotic pasture). Skinks typically dispersed short distances, and the nature of the matrix both quantitatively and qualitatively affected dispersal dynamics. Skink populations in pasture were significantly more genetically structured and had less genetic variation than similar populations in tussock, implying less dispersal between populations in pasture than tussock. Furthermore, although female‐biased dispersal was a feature of populations in tussock, no sex bias was evident in pasture. In addition, Bayesian individual‐based genetic assignment tests that incorporated prior mark‐recapture information revealed that some populations produced many emigrants but received few immigrants, whereas other populations were relatively insular. Patterns of dispersal and response to matrix vegetation were complex, and the causes of these patterns deserve attention in future studies of habitat fragmentation. Managing the vegetation matrix may be a practical way to connect animal populations in some situations.