Search

Aim: Woody ecosystems provide critical ecosystem functions and services but are increasingly threatened as invasive pathogens spread globally. Myrtle rust, caused by Austropuccinia psidii, arrived in New Zealand in 2017 and infects at least 12 of 18 species in the susceptible Myrtaceae plant family. Among these are species of structural, successional and cultural importance. We aim to assess whether the functional consequences of Myrtaceae loss could be mitigated if co‐occurring species with shared functional attributes are able to replace them. Location: New Zealand (but with concepts and methodologies that apply globally). Methods: Using a nationwide forest and shrubland plot data set, we assessed community vulnerability to the loss of Myrtaceae species by analysing proportional changes in average trait values when they are absent and produced spatial predictions indicating where species loss might have the greatest impact on community functionality. We then assessed whether compensatory infilling by co‐occurring species would mediate community vulnerability. Results: Forests and shrublands containing Kunzea ericoides and Leptospermum scoparium are highly vulnerable to their loss. Areas most vulnerable overall are the central and south‐eastern North Island, north‐eastern South Island and Stewart Island. For all species, compensatory infilling moderated the impact of their loss. However, if co‐occurring Myrtaceae were unable to respond, possibly if they were also infected, community vulnerability almost always increased because infilling species had different functional attributes, compounding the functional impact. Main Conclusions: Early successional woody plant communities and Myrtaceae‐dominated old‐growth forests are at most risk. Our spatial assessment of species‐level functional impacts from myrtle rust will facilitate better‐informed landscape‐level responses. Management actions and monitoring can now be targeted to areas and communities at greatest risk of losing ecosystem‐level processes. [ABSTRACT FROM AUTHOR]

The widely observed negative scaling relationship between organism size and abundance is predicted to have a universal −0.75 scaling exponent across all life forms. However, factors influencing frequently observed deviations from this exponent, such as ecosystem succession and organism traits, remain poorly understood.We explore the dependence of size–density scaling on ecosystem succession and organism traits by analysing size–density relationships in trees and soil invertebrates across 183 temperate forest plots comprising urban secondary forests, urban old‐growth forests and non‐urban natural forests.Exponents of scaling relationships in urban tree and invertebrate communities progressively steepened with increasing restored (planted) forest stand age as small organisms increased in abundance. In contrast, non‐urban tree scaling relationships flattened during succession with exponents veering away from −0.75, whereas urban tree and invertebrate communities converged towards this prediction in later successional stages.Our results shed light on how the body size structure of tree and soil invertebrate communities spanning multiple trophic levels shift over successional time as the relative abundances of large versus small‐bodied organisms increase. This study emphasises the fundamental influence of organismal traits and ecosystem succession on scaling relationships of organism body size and abundance. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Although disturbance is considered a major driver of plant invasions across many systems, our understanding of the mechanisms by which disturbance mediates understorey invasions in natural forests is limited.We used a national natural forest inventory dataset spanning New Zealand's wide climatic and soil fertility gradients to disentangle disturbance‐mediated community characteristics driving abundance, species richness and functional composition of understorey plant invasions.Disturbance‐mediated declines in canopy tree abundance and increases in soil fertility and pH increased non‐native plant richness and cover relative to co‐occurring native plant assemblages. Cover of non‐native species also increased with proximity to anthropogenic land cover.Non‐native plant assemblages had higher community‐weighted mean (CWM) values for specific leaf area (SLA) but lower CWM values for height and woodiness relative to native assemblages irrespective of disturbance. However, greater nearby anthropogenic land cover drove increased woodiness in non‐native assemblages but decreased woodiness in co‐occurring native assemblages.Synthesis: Our study provides the first national‐scale evidence that canopy disturbance effects on soil properties increase both richness and abundance of non‐native plants in natural forest understories. We also revealed functional trait differences between native and non‐native assemblages (SLA in particular), which could alter fundamental forest ecosystem processes like litter decomposition and nutrient cycling. Finally, landscape‐scale anthropogenic impacts may exacerbate forest invasions by increasing non‐native abundance and favouring woody invaders, which may achieve dominance in future forest communities over the longer‐term. [ABSTRACT FROM AUTHOR]

Summary: Evolutionary radiations of woody taxa within arid environments were made possible by multiple trait innovations including deep roots and embolism‐resistant xylem, but little is known about how these traits have coevolved across the phylogeny of woody plants or how they jointly influence the distribution of species.We synthesized global trait and vegetation plot datasets to examine how rooting depth and xylem vulnerability across 188 woody plant species interact with aridity, precipitation seasonality, and water table depth to influence species occurrence probabilities across all biomes.Xylem resistance to embolism and rooting depth are independent woody plant traits that do not exhibit an interspecific trade‐off. Resistant xylem and deep roots increase occurrence probabilities in arid, seasonal climates over deep water tables. Resistant xylem and shallow roots increase occurrence probabilities in arid, nonseasonal climates over deep water tables. Vulnerable xylem and deep roots increase occurrence probabilities in arid, nonseasonal climates over shallow water tables. Lastly, vulnerable xylem and shallow roots increase occurrence probabilities in humid climates.Each combination of trait values optimizes occurrence probabilities in unique environmental conditions. Responses of deeply rooted vegetation may be buffered if evaporative demand changes faster than water table depth under climate change. [ABSTRACT FROM AUTHOR]

The timing of flowering is central to plant life‐history as it initiates sexual reproduction, thus controlling plant interaction with pollinators and climate factors. A fundamental question is: what are the drivers of flowering time strategy in a species?We assembled mean flowering times for the indigenous dicotyledonous flora of New Zealand (n = 1303 species, including 177 tree species) and used phylogenetic models to determine how climate, plant traits, and evolutionary history (phylogeny) controlled interspecific variation in flowering times across an island flora.Across all species, on average, flowering was 19 days earlier in abiotically pollinated species relative to biotically pollinated species, 23 days earlier in woody species, relative to herbaceous species, 45 days earlier in species with fleshy‐fruits, relative to species with dry fruits and 31 days earlier in gender dimorphic species, relative to cosexual species. Species in warmer and drier climates flowered earlier than those growing under cool, moist climates.When all factors were considered together, the strongest influence on flowering time was sexual system: gender dimorphic species flowered earlier than cosexuals, even after accounting for other factors.Synthesis. We propose that these differences in flowering time arise because of sexual selection for early male flowering and sexual conflict between male and female individuals. As sexual selection and conflict may be stronger in gender dimorphic species than in cosexual species, our study suggests that plant sexual system is an important force structuring the phenology of plant communities, with potential consequences for ecological interactions and ecosystem processes. [ABSTRACT FROM AUTHOR]

Biodiversity analyses across continental extents are important in providing comprehensive information on patterns and likely drivers of diversity. For vascular plants in Australia, community‐level diversity analyses have been restricted by the lack of a consistent plot‐based survey dataset across the continent. To overcome these challenges, we collated and harmonised plot‐based vegetation survey data from the major data sources across Australia and used them as the basis for modelling species richness (α‐diversity) and community compositional dissimilarity (β‐diversity), standardised to 400 m2, with the aim of mapping diversity patterns and identifying potential environmental drivers. The harmonised Australian vegetation plot (HAVPlot) dataset includes 219 552 plots, of which we used 115 083 to analyse plant diversity. Models of species richness and compositional dissimilarity both explained approximately one‐third of the variation in plant diversity across Australia (D2 = 33.0% and 32.7%, respectively). The strongest environmental predictors for both aspects of diversity were a combination of temperature and precipitation, with soil texture and topographic heterogeneity also important. The fine‐resolution (≈ 90 m) spatial predictions of species richness and compositional dissimilarity identify areas expected to be of particular importance for plant diversity, including south‐western Australia, rainforests of eastern Australia and the Australian Alps. Arid areas of central and western Australia are predicted to support assemblages that are less speciose or unique; however, these areas are most in need of additional survey data to fill the spatial, environmental and taxonomic gaps in the HAVPlot dataset. The harmonised data and model predictions presented here provide new insight into plant diversity patterns across Australia, enabling a wide variety of future research, such as exploring changes in species abundances, linking compositional patterns to functional traits or undertaking conservation assessments for selected components of the flora. [ABSTRACT FROM AUTHOR]

Questions: (1) What can be learned by extending a national classification into unsampled forest types? (2) Are both remotely sensed and environmental predictors needed to model and map associations? (3) For mapping, are LiDAR-generated canopy structure parameters or reflectance from spectral imagery more useful? (4) How can we assess uncertainty of a final map? Location: Warawara Forest, Northland, New Zealand. Methods: We sampled 205 vegetation plots and assigned them to an existing national classification using the fuzzy classification framework of noise clustering. Plots too distinct to be assigned were used to define new associations. We produced spatial models of each association using boosted regression trees. Predictors included 11 environmental, 11 canopy reflectance, and 17 canopy structure variables. We created a composite map by assigning each map pixel to the association with the highest occurrence probability. We evaluated uncertainty by examining locations where no class was predicted with probability above 0.2 and by creating a confusion map based on entropy. Results: Forty-five plots were assigned to six of 79 existing national associations and 147 plots were used to define two new forest associations. Three shrubland types are widespread nationally, whereas two young forest types are northern. Three mature forest types are narrowly distributed nationally, with the new "High-elevation hardwood forest" largely restricted to Warawara Forest. Three associations were mapped using remotely sensed predictors alone, whereas two also required environmental predictors. Overall, canopy reflectance predictors explained more deviance than canopy structure. Examining locations where no association was predicted well and where multiple associations were predicted equally showed areas mapped as younger forests to have greatest uncertainty. Conclusions: In answering our questions, we present a vegetation classification and map for Warawara Forest that provides a framework to guide the indigenous people's management responses to threats to valued communities and their species. [ABSTRACT FROM AUTHOR]

Aims: The Myrtaceae is a woody family that plays an important role in forest ecosystems globally. The recent spread of myrtle rust, caused by a fungal pathogen (Austropuccinia psidii), from its native South America into New Zealand (NZ), highlights the need to quantify the ecological importance of Myrtaceae in NZ woody ecosystems. Location: New Zealand. Methods: Using NZ nationwide forest and shrubland inventory data, collected from 2009 to 2014, we quantified the ecological importance of Myrtaceae based on its richness and abundance relative to co-occurring woody families. We then explored how climate and forest stand structure affect Myrtaceae importance in general and by tribe and growth form. Finally, we compared functional traits associated with plant growth and reproductive strategies with other dominant woody families and determined Myrtaceae's contributions to community-weighted mean (CWM) trait values. Results: Myrtaceae occurred in 74% of the study plots and its importance value was the second highest across the woody families. It was the only one in which climbers substantially contributed to the importance value (17%). Greater Myrtaceae importance values were associated with warmer and more mesic climates and early forest successional stages. Climate associations were similar within tribes and growth forms, whereas forest structure effects varied. Myrtaceae was functionally distinct from most co-occurring woody families. Contributions to CWM wood density, maximum height, and specific leaf area values were significantly greater than expected from its importance value. Conclusions: Myrtaceae is the second most ecologically important woody family in NZ woody ecosystems. The family has a distinctive functional trait spectrum associated with high wood density and tall stature, ensuring large and enduring carbon stocks. There will potentially be large and deleterious outcomes in forest ecosystems if taxon-specific pathogens, such as Austropuccinia psidii, spread and significantly reduce Myrtaceae importance. [ABSTRACT FROM AUTHOR]

The global spread of invasive plant pathogens is increasing, putting natural forests and ecosystem services under threat. Spatial data can quantify range non‐overlap between invasive pathogens and their hosts to identify existing and potentially restorable refugia to enable 'escape' from the pathogen.In 2017, myrtle rust Austropuccinia psidii was detected in New Zealand. New Zealand has 27 native woody and liana species in the plant family susceptible to the disease (Myrtaceae), many of which are ecosystem dominants and economically important. Spatial methods were used to compare the current New Zealand distribution of myrtle rust with the modelled distributions of its potential native hosts. To guide management and set priorities for conservation of at‐risk species, areas of potential refugia where a Myrtaceae species is predicted to occur outside the pathogen range were identified under two myrtle rust distribution scenarios.Myrtle rust will thrive in New Zealand's warmer regions. Many native Myrtaceae are distributed within this area, but several species occur extensively outside the core range of the disease. Species distributed in cooler southern regions will be best placed to persist in refugia.Myrtaceae species with specific habitat requirements and narrow geographical ranges in warmer (northern) areas are likely to require ex situ or active in situ management. Even widely distributed species will benefit from the restoration of suitable habitat that supports multiple species outside the myrtle rust range.Synthesis and applications. Spatial data can be used to identify refugia and restoration opportunities, and thus inform landscape‐level management responses to invasive pathogens. This approach can guide decisions over where to implement in situ (e.g. fungicide spraying) versus ex situ (e.g. seed banking, botanic gardens) management efforts. [ABSTRACT FROM AUTHOR]

Understanding influences of environmental change on biodiversity requires consideration of more than just species richness. Here we present a novel framework for understanding possible changes in species' abundance structures within communities under climate change. We demonstrate this using comprehensive survey and environmental data from 1748 woody plant communities across southeast Queensland, Australia, to model rank‐abundance distributions (RADs) under current and future climates. Under current conditions, the models predicted RADs consistent with the region's dominant vegetation types. We demonstrate that under a business as usual climate scenario, total abundance and richness may decline in subtropical rainforest and shrubby heath, and increase in dry sclerophyll forests. Despite these opposing trends, we predicted evenness in the distribution of abundances between species to increase in all vegetation types. By assessing the information rich, multidimensional RAD, we show that climate‐driven changes to community abundance structures will likely vary depending on the current composition and environmental context. [ABSTRACT FROM AUTHOR]

Aims Accurate field quantification of stem counts is time consuming and laborious, especially in ecosystems containing many small individuals where counts are immense. There are many large, long-term data sets worldwide that include various measures of woody plant abundance, such as crown cover, that are faster and easier to measure than true counts of individuals. Quantifying the number of individuals allows in-depth research into various topics including functional ecology, carbon accounting, conservation and metabolic theory. Here we test the accuracy of predicting the abundance of individual woody plants from cover and forest structure measures, and explore the implications of refined abundance measures for understanding the rarity of woody plant species across southeast Queensland. Location Southeast Queensland ( SEQ), Australia. Methods To supplement an existing data set of 1251 sites with measured crown covers for woody plants in various strata, we sampled stem counts in an additional 30 sites, forming a calibration data set. We ensured that these 30 sites covered the environmental variation in the study area. Generalized additive mixed effects models were used to predict stem counts for all woody plants in the original data set from their crown cover and forest structure values and a site-level variable accounting for water balance. We used these refined abundance data to investigate relationships between local and regional abundance for different size classes. Results Stem densities increased with crown cover in a non-linear fashion; slowing once crown cover reached ca. 5% for shrubs and ca. 50% for trees, depending on their maximum potential height. Using the predicted stem count data, we found that shrubs were more locally abundant than trees, but less regionally abundant. Larger trees (>20 m maximum potential height) showed a negative relationship between local and regional abundance; there was no significant relationship between other size classes. Conclusions Our study demonstrates how crown cover can be converted to stem counts using a calibration data set and flexible mixed-effects models. This enables further ecological analysis at a fraction of the investment required to re-survey. Analyses of abundances revealed that tree species are less locally abundant than smaller woody species, likely due to space filling constraints, but more regionally abundant. [ABSTRACT FROM AUTHOR]

Diatoms are unicellular photosynthetic algae with promise for green production of fuels and other chemicals. Recent genome-editing techniques have greatly improved the potential of many eukaryotic genetic systems, including diatoms, to enable knowledge-based studies and bioengineering. Using a new technique, transcription activator-like effector nucleases ( TALENs), the gene encoding the urease enzyme in the model diatom, Phaeodactylum tricornutum, was targeted for interruption. The knockout cassette was identified within the urease gene by PCR and Southern blot analyses of genomic DNA. The lack of urease protein was confirmed by Western blot analyses in mutant cell lines that were unable to grow on urea as the sole nitrogen source. Untargeted metabolomic analysis revealed a build-up of urea, arginine and ornithine in the urease knockout lines. All three intermediate metabolites are upstream of the urease reaction within the urea cycle, suggesting a disruption of the cycle despite urea production. Numerous high carbon metabolites were enriched in the mutant, implying a breakdown of cellular C and N repartitioning. The presented method improves the molecular toolkit for diatoms and clarifies the role of urease in the urea cycle. [ABSTRACT FROM AUTHOR]

Ecological studies of pairwise interactions are constrained by the methods available for rapid species identification of the interacting organisms. The resolution of data required to characterize species interaction networks at multiple spatio-temporal scales can be intensive, and therefore laborious and costly to collect. We explore the utility of high-resolution DNA melt-curve analysis ( HRM) as a rapid species identification method. An approach was developed to identify organisms at the pairwise interaction level, with particular application to cryptic species interactions that are traditionally difficult to study. Here, we selected a challenging application; to identify the presence/absence of pathogenic fungi ( Sporothrix inflata, Ophiostoma nigrocarpum and Ophiostoma galeiforme) transported by bark beetle vectors ( Hylastes ater and Hylurgus ligniperda). The technique was able to distinguish between different species of DNA within a single, pooled sample. In test applications, HRM was effective in the mass screening and identification of pathogenic fungal species carried by many individual bark beetle vectors ( n = 455 beetles screened) across large geographic scales. For two of the fungal species, there was no difference in the frequency of association with either of their vectors, but for the third fungal species there was a shift in vector-pathogen associations across locations. This technique allows rapid, mass screening and characterization of species interactions at a fraction of the time and cost of traditional methods. It is anticipated that this method can be readily applied to explore other cryptic species interactions, or other studies requiring rapid generation of large data sets and/or high-throughput efficiency. [ABSTRACT FROM AUTHOR]

1. Globally, temperate grasslands have been heavily modified by agricultural intensification. The ecological integrity of many remaining semi-natural grasslands is further threatened by the encroachment of invasive alien woody plant species, such as conifers. 2. Although the ecological impact of conifers is often inferred to be directly related to increasing conifer density at invaded sites, interpretation of these density-dependent effects on native biodiversity is almost always confounded by strong correlations between density and time since invasion. Here, we isolate the direct effects of exotic conifer density on native invertebrate assemblages from the confounding effects due to time since invasion, by establishing replicated experimental plantings of the invasive Pinus nigra (densities of 400, 800, 1600, 2500 and 3500 trees per ha, established in 1993) in New Zealand. 3. From the 29 549 invertebrates captured, the relative abundance of major classes and orders was largely unaffected by conifer invasion at densities below 800 trees per ha at age 14 years, but differed substantially in higher-density conifer stands (canopy cover >50%). At the species level, beetle species composition was highly sensitive to conifer invasion at densities as low as 400 trees per ha at age 14 years. Changes in beetle species composition were correlated with reduced soil moisture, increases in canopy cover, and trap distance from the nearest semi-natural grassland. 4. Synthesis and applications. The effects of exotic conifer invasion on grassland invertebrate assemblages were strongly dependent on conifer density. In our study, the negative effects of conifer invasion on biodiversity were comparatively low at densities below ≤800 trees per ha at 14 years after invasion. To conserve invertebrate diversity in semi-natural grasslands we recommend a dual focus of conservation actions targeting: (i) immediate control, or thinning, of high density conifer infestations (>800 trees per ha) to restore habitat to a state suitable for grassland species, and (ii) longer-term removal of sparse, pre-coning infestations in order to prevent further spread. We propose the use of canopy cover as a proxy for the confounded relationship between conifer density and time since invasion. [ABSTRACT FROM AUTHOR]