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The vegetation of subantarctic Campbell Island consists mainly of lowland Dracophyllum scrub and upland tussock grassland and tundra. Soon after the island was discovered in 1810, occupation by sealers and whalers led to localized burning and cutting of scrub. Further burning and cutting took place as a result of sheep farming between 1894 and 1931. Since the earliest photographs and vegetation descriptions of the island in the late nineteenth century, scrub cover has expanded markedly. Also, since the 1960s, the island has become warmer and drier. The aim of this paper is to quantify scrub changes as depicted in photo-sequences from the island, and to establish if the spread of scrub is a result of the cessation of anthropogenic activities or a response to global warming. Campbell Island, an isolated island 600 km south of New Zealand mainland (52°33.7′S, 169°09′E). Changes in scrub cover in the island were established through analysis of 33 photographic sequences in the island, the earliest photos dating back to 1888. Visual estimates were made of percentage woody cover in matching areas of repeat photographs, and of changes in scrub distribution with altitude and landscape type. Dracophyllum scrub was restricted at the time of the first photographs (1888) relative to its present extent, and earlier written observations suggest that there had been little change from the 1840s. Scrub cover has subsequently increased in most areas. Most of the spread occurred after the cessation of farming. Change has mostly consisted of a thickening and expansion of pre-existing scrub patches. There is no indication that the upper elevational limit of scrub has increased. Initial reduction of scrub was probably due to anthropogenic fire in the early nineteenth century, although it is possible that less favourable climates had also restricted its distribution. Failure of the scrub to regenerate significantly between 1840 and c. 1895 may also have been a consequence of generally cooler, wetter climates at this time. Rapid scrub expansion began between the end of farming and burning in 1931 and 1988 when the remaining feral sheep were removed. Sheep grazing in the absence of fire reduced competition, and encouraged regeneration and growth of woody scrub. Spread was probably assisted by a pronounced shift to warmer, drier climates in the second half of the twentieth century. Upper elevational limits of scrub have not increased, suggesting that factors other than summer temperature are controlling scrub line in this superoceanic environment. [ABSTRACT FROM AUTHOR]

Disturbed (de‐vegetated) coastal dunes can follow divergent evolutionary pathways, evolving to one of a range of possible morphologies in response to spatial and temporal variations in windiness (i.e. the speed and direction of competent winds) or vegetation cover (i.e. the magnitude and rate of vegetation loss). Here we examine the influence of these factors on the evolution of two adjacent barriers during a sustained dune restoration programme, at Doughboy Bay, Aotearoa/New Zealand. We document a shift from a stable prograded foredune barrier to a mobile dune state over a 15‐year period. The spatial and temporal patterns of sedimentation across the barriers reflect alongshore variations in incident wind direction. Changes in vegetation resulted from an alongshore gradient in wind speed, with little decline in vegetation cover recorded towards the more sheltered sections of the dunes and almost total loss of vegetation towards the centre of the bay. Subsequent changes in vegetation cover continued to reflect these gradients in wind speed and direction, with an increase in vegetation cover associated with relatively sheltered sections of coast and a continued decline or no change in vegetation cover across the more exposed parts of the barriers. Finally, localized sediment accumulation across both barriers is strongly associated with the presence of dune‐building species. This case demonstrates the influence of wind speed, wind direction and vegetation on post‐disturbance foredune morphologies and barrier development. We propose a three‐stage conceptual model of barrier evolution consistent with existing biogeomorphic disturbance models: (1) an initial 'reaction' phase, characterized by high vegetation cover and relatively little topographic change; (2) an 'activation' phase, characterized by low vegetation cover and rapid rates of topographic change; and (3) a 'stabilization' phase, characterized by increasing vegetation cover and topographic stability. Dune restoration interventions of this type would clearly benefit from an analysis of incident wind conditions prior to commencement and careful consideration of where and how to reintroduce native sand‐binding species. [ABSTRACT FROM AUTHOR]

In 2020, the Australian and New Zealand flux research and monitoring network, OzFlux, celebrated its 20th anniversary by reflecting on the lessons learned through two decades of ecosystem studies on global change biology. OzFlux is a network not only for ecosystem researchers, but also for those 'next users' of the knowledge, information and data that such networks provide. Here, we focus on eight lessons across topics of climate change and variability, disturbance and resilience, drought and heat stress and synergies with remote sensing and modelling. In distilling the key lessons learned, we also identify where further research is needed to fill knowledge gaps and improve the utility and relevance of the outputs from OzFlux. Extreme climate variability across Australia and New Zealand (droughts and flooding rains) provides a natural laboratory for a global understanding of ecosystems in this time of accelerating climate change. As evidence of worsening global fire risk emerges, the natural ability of these ecosystems to recover from disturbances, such as fire and cyclones, provides lessons on adaptation and resilience to disturbance. Drought and heatwaves are common occurrences across large parts of the region and can tip an ecosystem's carbon budget from a net CO2 sink to a net CO2 source. Despite such responses to stress, ecosystems at OzFlux sites show their resilience to climate variability by rapidly pivoting back to a strong carbon sink upon the return of favourable conditions. Located in under‐represented areas, OzFlux data have the potential for reducing uncertainties in global remote sensing products, and these data provide several opportunities to develop new theories and improve our ecosystem models. The accumulated impacts of these lessons over the last 20 years highlights the value of long‐term flux observations for natural and managed systems. A future vision for OzFlux includes ongoing and newly developed synergies with ecophysiologists, ecologists, geologists, remote sensors and modellers. [ABSTRACT FROM AUTHOR]

Wood‐inhabiting fungal communities are a diverse and ecologically critical part of forest ecosystems, yet the spatial structure of fungal biodiversity in these ecosystems is largely unknown. Legislation allowed harvesting of deadwood from temperate rainforests on conservation lands in New Zealand following Cyclone Ita in 2014. Harvesting guidelines specified widely spread harvesting, on the assumption that rare fungal species may be highly spatially restricted, but were not based on quantitative assessment. We sampled fungi in and on logs of Dacrydium cupressinum (Podocarpaceae) a long‐lived, common, canopy tree in lowland New Zealand forests. DNA was extracted from 81 logs varying in decay state across a 40 km long region of West Coast (South Island) forests, and sequenced using general fungal primers for metabarcoding to identify OTUs (operational taxonomic units). We examined three axes of rarity: occupancy, dominance when present, and niche breadth (as spatial extent and decay state specialization). Low‐occupancy fungi were common, including a group of infrequently occurring but dominant when present fungi, the majority of which were Ascomycota. Despite this, there was an overall positive relationship between occupancy and dominance. Widespread, dominant fungi were most commonly Basidiomycota. Testing all fungal OTUs, there were no more fungi with maximum range sizes < 4 km than would be expected at random. Of the 351 low‐occupancy OTUs found two to four times, only 12 had maximum range sizes < 900 m, and there was no more spatial restriction at scales < 900 m than would be expected by random chance, although there was some evidence of niche breadth restriction based on decay state similarity. The results show that fungal communities in deadwood are highly diverse, and include many rare taxa. Nonetheless, the lack of fungal OTUs with spatial restriction at scales < 900 m suggests that spatially dispersed timber harvesting will not mitigate risks of harvesting to rare fungal biodiversity. [ABSTRACT FROM AUTHOR]

In species that form dense populations, major disturbance events are expected to increase the chance of establishment for immigrant lineages. Real‐time tests of the impact of disturbance on patterns of genetic structure are, however, scarce. Central to testing these concepts is determining the pool of potential immigrants dispersing into a disturbed area. In 2016, a 7.8 magnitude earthquake occurred on the South Island of New Zealand. Affecting approximately 100 km of coastline, this quake caused extensive uplift (several metres high), extirpating many intertidal populations, including keystone intertidal kelp species. Following the uplift, we set out to determine the geographic origins of detached kelp specimens which rafted into the disturbed zone. Specifically, we used genotyping‐by‐sequencing (GBS) approaches to compare beach‐cast southern bull‐kelp (Durvillaea antarctica and Durvillaea poha) samples to established populations throughout the species' ranges, and thus infer the geographic origins of potential colonists reaching the disturbed coast. Our findings revealed an ongoing supply of diverse lineages dispersing to the newly uplifted coastline, suggesting potential for establishment of "exotic" lineages following disturbance. Furthermore, we found that some drifting individuals of each species came from far‐distant regions, some >1,200 km away. These results show that diverse lineages – in many cases from very distant sources – can compete for new space in the wake of an exceptional disturbance event, illustrating the potential of long‐distance dispersal as a key mechanism for reassembly of coastal ecosystems. Furthermore, our findings demonstrate that high‐resolution genomic baselines can be used to robustly assign the provenance of dispersing individuals. [ABSTRACT FROM AUTHOR]

The infrequent and unpredictable nature of earthquakes means that their landslide‐generated impacts on forests are rarely investigated. In montane forests, landslides are the main cause of tree death and injury during earthquakes. Landslides range from soil movements that uproot and bury trees over extensive areas to rock falls that strike individual trees. We examined unexplored relationships between tree survival and distance from an epicentre, soil‐available phosphorus (P) as an indicator of soil development and tree diameter. We expected decreased tree growth in damaged forests because of tree injury.We used a plot network, established in 1974 and resurveyed regularly ever since, to quantify survival and growth responses 6–30 km from the epicentre of a 1994 earthquake in New Zealand's Southern Alps. Our Bayesian analysis used 8,518 trees from 250 plots that representatively sampled a naturally monospecific Nothofagus forest. As the time‐scales over which responses could emerge were unknown, we compared relationships for a pre‐earthquake period with 0–5 years post‐earthquake, and with 5+ years post‐earthquake.Not all plots were affected by the earthquake. We found that 0–5 years post‐earthquake survival increased logarithmically with distance from the epicentre with lowered survival up to 20 km from the epicentre. Survival was low on plots with high soil‐available P. An inverted U‐shaped relationship between survival and diameter pre‐earthquake was not found 0–5 years post‐earthquake. This was because of surprisingly high survival by large trees. The earthquake most often suppressed 0–5 years post‐earthquake growth up to 15 km from the epicentre, but this was only apparent after accounting for more general growth differences among periods. The positive relationship between growth and soil‐available P pre‐earthquake and 5+ years post‐earthquake reflected enhanced growth on young soils. This contrasted with a negative effect of soil‐available P on growth 0–5 years post‐earthquake.Synthesis. Soil‐available P, tree diameter and distance from the epicentre independently determined how tree survival and growth responded to an earthquake. The impacts on survival and growth largely occurred 0–5 years post‐earthquake and suggests a level of resilience in mountain beech forests. [ABSTRACT FROM AUTHOR]

Aim To examine the relationship between diadromy and dispersal ability in New Zealand’s freshwater fish fauna, and how this affects the current environmental and geographic distributions of both diadromous and non-diadromous species. Location New Zealand. Methods Capture data for 15 diadromous and 15 non-diadromous fish species from 13,369 sites throughout New Zealand were analysed to establish features of their geographic ranges. Statistical models were used to determine the main environmental correlates of species’ distributions, and to establish the environmental conditions preferred by each species. Environmental predictors, chosen for their functional relevance, were derived from an extensive GIS database describing New Zealand’s river and stream network. Results In terms of geography, most diadromous species occur in a scattered fashion throughout extensive geographic ranges, and occupy large numbers of catchments of widely varying size. By contrast, most non-diadromous species show relatively high levels of occupancy of smaller geographic ranges, and most are restricted to a few large catchments, particularly in the eastern South Island. In terms of environment, there is marked separation of diadromous from non-diadromous species, with diadromous species generally caught most frequently in low-gradient coastal rivers and streams with warm, maritime climates. With a few notable exceptions, most diadromous species have lower occurrence in river segments that are located above obstacles to upstream migration. Non-diadromous species are usually caught in inland rivers and streams with cool, strongly seasonal climates, typified by a low frequency of high-intensity rainfall events. Main conclusions We interpret the contrasting biogeographies of New Zealand’s diadromous and non-diadromous species as reflecting interaction between their marked differences in dispersal ability and a landscape that is subject to recurrent, often large-scale, natural disturbance. While both groups are likely to be equally susceptible to local, disturbance-driven extinction, the much greater dispersal ability of diadromous species has allowed them to persist over wide geographic ranges. By contrast, the distributions of most non-diadromous species are concentrated in a few large catchments, mostly in regions where less intense natural disturbance regimes are likely to have favoured their survival. [ABSTRACT FROM AUTHOR]

1. We investigated the effects of local disturbance history and habitat parameters (abiotic and biotic) on the microdistribution of benthic invertebrates during several floods in two streams, the Schmiedlaine in Germany (four events) and the Kye Burn in New Zealand (two events). 2. Bed movement patterns were quantified using metal-link scour chains. Before and after each flood, quantitative invertebrate samples were taken from replicate bed patches that had experienced sediment scour, fill or remained stable. 3. Patterns of invertebrate density in the different bed stability types (i.e. scour, fill, stable) varied between floods, sampling dates and streams, but invertebrate density was highest in stable patches in >50% of all the patch type effects detected and lowest in fill patches in 75% of all detected effects. Stable bed patches acted as a refugium for Liponeura spp. and Leuctra spp. in the Schmiedlaine and for Hydracarina and Deleatidium spp. in the Kye Burn. 4. Averaged across both streams, only near-bed current velocity was correlated with invertebrate distribution on the streambed more often than disturbance history. In the Kye Burn, disturbance history and water depth were the most influential habitat parameters. 5. Our results suggest that a thorough understanding of the microdistribution of benthic invertebrates requires knowledge of disturbance history, as well as more readily measured habitat parameters such as current velocity or water depth. [ABSTRACT FROM AUTHOR]

1. We investigated the effects of a flood on the fauna and physical habitat of the hyporheic zone of the Kye Burn, a fourth order gravel-bed stream in New Zealand.2. Freeze core hyporheic samples (to 50 cm depth) and benthic samples (to 10 cm) were taken, along with measurements of vertical hydrological gradient, before, 2 days after and 1 month after the flood (estimated return period: 1.5 years, estimatedQmax = 10.4 m3 s−1).3. The composition of the hyporheos differed over the three sampling occasions with fewer taxa collected immediately postflood than preflood. The equitability of the community was higher on both postflood occasions, consistent with the reduced densities of two abundant taxa (Leptophlebiidae and Copepoda).4. Total invertebrate abundance was lower on the postflood occasions than preflood in both benthic (0–10 cm) and hyporheic (10–50 cm) sediments. Several taxa, including asellotan isopods and amphipods, recovered within 1 month of the event. Hyporheic densities of larvalHydoraand nematodes did not differ among the three sampling occasions, but the water mitePseudotryssaturuswas more abundant 1 month after the flood than preflood. There was no evidence of vertical movements (to 50 cm) by any taxa in response to the flood.5. The proportion of fine sediments (<1 mm) in the subsurface sediments (10–50 cm) increased over the three sampling occasions and median particle size declined, but sediment porosity did not change. More particulate organic matter was found in the sediments after the flood.6. Our study provides little evidence that the hyporheic zone (to 50 cm) acted as a significant refuge during the flood event, although movements to or recolonisation from sediments deeper than 50 cm could explain the recovery of many crustacean and mite taxa within 1 month. [ABSTRACT FROM AUTHOR]

1. Perturbation pathways affecting interactions between feeding habitat, food supplies and diet of a lotic avian predator, blue duck ( Hymenolaimus malacorhynchos Gemlin), were tracked in a New Zealand river following substantial inputs of sediment from a volcanic eruption. Sediment impacts were separated temporally into two distinct phases: (i) deposition of fine ash from volcanic fall-out, and (ii) pulsed releases of volcanic sand and gravel retained by an upstream dam. 2. Levels of interstitial suspendable inorganic sediments increased by several orders of magnitude following ash inputs to the river, but returned to low levels within 3 months. Flushing of volcanic sand and gravel retained by the dam resulted in sediment deposition upstream of a large island where coarse material lodged firmly between larger benthic substratum elements in blue duck feeding habitat. 3. Changes in algal biomass appeared to largely reflect seasonal and hydrological influences, but the percentage inorganic content of periphyton increased significantly during both posteruption phases. 4. Diversity and abundance of blue duck food supplies on boulders and on the riverbed declined following the eruption, whereas significant impacts on biomass were only detected in benthic habitats which were more susceptible to sediment deposition. However, percent composition of the benthic and boulder invertebrate food resources appeared largely unaffected by the eruption. 5. There was no apparent association between the eruption and the composition or electivity ( E*) of blue duck diet, but there was a significant increase in the percent inorganic content of faeces, suggesting a reduction in the quality of food rations. 6. Changes in food quantity and quality associated with deposition of volcanic sediments were linked to an observed decline in blue duck population density and fecundity following the eruption. An interacting continuum of adaptive responses to perturbation intensity and impact duration is proposed for blue duck, and potentially other long-lived, riverine birds, that enable them to cope with disturbances in highly variable and heterogenous lotic environments. [ABSTRACT FROM AUTHOR]

SUMMARY 1. The effects of physical disturbance in terms of wave exposure, shore slope and substrate mobility on the presence, species richness, cover and depth limits of the low-growing, shallow water macrophyte community (called the low mixed community) were examined at 41 shore sites in Lake Wanaka, South Island, New Zealand. 2. Wave exposure at a site was described by the previous year's maximum depth of sediment motion and maximum vertical extension of waves, determined from a computer wave model. Shore slope at each site was recorded from -1 to 0 m depth, and sediment stability was assessed as the cover of small gravel. 3. The low mixed community was only present on sites where the previous year's maximum depth of sediment motion was <8 m, maximum wave run-up was <0.3 m, shore slope <0.12 m m-1 , and small gravel cover <78%. 4. Species richness, cover and depth limits of the low mixed community decreased with increasing disturbance on the sites. Sixty-two percentage of the variation in species richness could be explained by physical disturbance variables when all sites were included (N=41). When only sites with a low mixed community were included (N=22), only 18% of the variation was explained. Species richness within sites supporting a low mixed community is thus poorly explained by physical disturbance, whereas presence or absence is better explained. There was no evidence to support the intermediate disturbance hypothesis in this study. 5. Disturbance as a result of waves explained 86% of the variation in cover among sites with a low mixed community and accounted for 68 and 58% of the variation in upper and lower depth limit of the low mixed community, respectively. 6. The models obtained in this study can be used as predictive models for the low mixed community in New Zealand lakes in relation to natural physical disturbance on the shore. By integrating these results with previous studies on the effect of water level fluctuation, we describe... [ABSTRACT FROM AUTHOR]

1. Environmental variables, benthic algal biomass and macroinvertebrate fauna were examined from September 1999 to January 2000 (austral summer) along two glacier-fed rivers in South Island, New Zealand. 2. The rivers were characterized by high flow variability, high turbidity and physically disturbed beds. Water temperature ranged from <1 °C near the glacier margin to 10 °C further downstream. 3. Epilithic algal biomass was very low (<0.1 mg m–2) in months characterized by heavy rainfall, but ranged from 1.1 to 14.4 mg m–2 following an extended period with negligible precipitation. 4. Abundance and diversity of invertebrates in both rivers was low. Dominant taxa were Chironomidae (Orthocladiinae, Podonominae, Diamesinae), although mayfly species (Deleatidium: Leptophlebiidae) also occurred at most sites. A species of Eukiefferiella (Orthocladiinae) was collected at all sites and was the most abundant invertebrate close to the glacier margins. No meiofauna were found in either river. 5. Faunal diversity increased at the lowermost stations where species of Plecoptera, Trichoptera, Coleoptera and non-chironomid Diptera also occurred. 6. The faunas of the two New Zealand rivers conformed to the conceptual model of Milner & Petts (1994) in that taxon richness increased downstream with water temperature. However, invertebrate abundance increased downstream in only one of the two rivers. Also in contrast to the model predictions, Leptophlebiidae and Orthocladiinae, rather than Diamesinae, dominated the fauna at the coldest sites. [ABSTRACT FROM AUTHOR]

1. The hyporheic zone has long been regarded as a potential refugium for lotic invertebrates during disturbance. However, there have been few attempts to quantify the stability of this habitat during high flow events. In a New Zealand stream with an unstable bed, the present authors monitored spatial patterns of scour and fill in a riffle in a wide flood plain and at two sites in a constrained reach: a pool-riffle with bedrock outcrops and a plane-bed (a bedform characterized by long stretches of planar stream bed). 2. At each 20-m site, 100 scour chains were installed in a systematic grid with about 1 m between chains. Scour was measured by comparing the length of chain exposed before and after a high flow event, whereas filling depth was equivalent to the thickness of the sediment deposited on top of the chains during the event. For each chain, the present authors noted dominant particle size and degree of packing of the surrounding bed, water depth and presence or absence of large stones upstream. Chains were re-located after four smaller spates, one intermediate event and one large flood. 3. Most events caused a complex mosaic of bed patches which experienced scour, fill or remained undisturbed. These patterns, which were mostly site- and event-specific, were often significantly influenced by the longitudinal or lateral position of the chains in the spatial grids. 4. The cumulative effect of the six high flow events differed substantially between sites. The first site experienced predominantly scour, the second both scour and fill, and the third almost exclusively fill. These differences were partly explained by channel geomorphology. The bedrock outcrops at the constrained pool-riffle site forced the flow at high discharge, causing deep scour in these areas, whereas a backwater effect at the third site reduced near-bottom shear stress during larger events and led to sediment deposition. 5. Except for a single event at the second site, scour affected mainly the uppermost 10–15 cm of the stream bed. Therefore, almost the entire hyporheic zone below this depth would have been available as refugium for invertebrates, in addition to the often consider-able number of bed patches which remained undisturbed during the six high flow events. 6. Fill without earlier scour during the same high flow event was common at all sites. Most previous studies have assumed that lotic invertebrates are mainly affected by scour during high flow events, but the consequences of sediment deposition may be just as far reaching. [ABSTRACT FROM AUTHOR]

Patterns of mortality, recruitment, and forest turnover were investigated using permanent plot data from temperate forests in 14 localities throughout New Zealand. Tree mortality and recruitment rates were calculated from tagged trees =/> 10 cm diameter at 1.4 m on individual 400 m2 plots, and turnover rates were calculated as the mean of mortality and recruitment rates. Turnover rates (1.4% per year) were very similar to those recorded for tropical forests (i.e. 1.5% per year). As was shown in tropical forests, we also found significant relationships between forest turnover and species richness. In New Zealand forests there was also a decrease in species richness and turnover rates with increasing latitude. Although species richness is well known to decline with latitude, our study provides support for apossible link between seasonality and disturbance with tree turnoverand species diversity. While tree mortality and recruitment rates were approximately in balance at some localities, in others there were imbalances between mortality and recruitment rate. [ABSTRACT FROM AUTHOR]