Societal Impact Statement Mixed species plantings present an attractive alternative to monoculture reforestation through their added benefits to biodiversity. Yet there is ambiguity in the use of the term ‘biodiversity’ in carbon and biodiversity markets, which may create perverse outcomes when designing schemes and projects. Here, we review how the concept of biodiversity is defined and applied in reforestation projects, and restoration more broadly. Improved transparency around the use of the term biodiversity is urgently needed to provide rigour in emerging market mechanisms, which seek to benefit the environment and people. Summary Reforestation to capture and store atmospheric carbon is increasingly championed as a climate change mitigation policy response. Reforestation plantings have the potential to provide conservation co‐benefits when diverse mixtures of native species are planted, and there are growing attempts to monetise biodiversity benefits from carbon reforestation projects, particularly within emerging carbon markets. But what is meant by ‘biodiverse’ across different stakeholders and groups implementing and overseeing these projects and how do these perceptions compare with long‐standing scientific definitions? Here, we discuss approaches to, and definitions of, biodiversity in the context of reforestation for carbon sequestration. Our aim is to review how the concept of biodiversity is defined and applied among stakeholders (e.g., governments, carbon certifiers and farmers) and rights holders (i.e., First Nations people) engaging in reforestation, and to identify best‐practice methods for restoring biodiversity in these projects. We find that some stakeholders have a vague understanding of diversity across varying levels of biological organisation (genes to ecosystems). While most understand that biodiversity underpins ecosystem functions and services, many stakeholders may not appreciate the difficulties of restoring biodiversity akin to reference ecosystems. Consequently, biodiversity goals are rarely explicit, and project goals may never be achieved because the levels of restored biodiversity are inadequate to support functional ecosystems and desired ecosystem services. We suggest there is significant value in integrating biodiversity objectives into reforestation projects and setting specific restoration goals with transparent reporting outcomes will pave the way for ensuring reforestation projects have meaningful outcomes for biodiversity, and legitimate incentive payments for biodiversity and natural capital accounting.

Translocation is commonly used in the conservation of threatened species to help mitigate the risk of local extinctions. However, translocations are often limited by knowledge of the species ecological requirements that promote persistence in the landscape. Small translocation trials with a strong experimental design can help to address species knowledge gaps and identify effective strategies for the successful establishment of a threatened species prior to implementing full‐scale planting regimes. In this study, we experimentally translocated 128 plants of the endangered Persoonia hirsuta (Proteaceae) at a dry sclerophyll mining offset in New South Wales (NSW), Australia, and investigated the effects of propagation type (seeds and vegetative cuttings), plant guards, and mulching on short‐term plant growth and survival. Transplants were impacted by herbivory and unprecedented extreme temperatures over summer 2019–2020 with 25 of the 128 plants surviving after 20 months of monitoring. Among the surviving individuals, all but one were seed propagated and 72% of survivors were protected by a plant guard. Short‐term survival and establishment of P. hirsuta translocants was increased by producing plants from seeds, and the use of plant guards with localized mulch. We also identified significantly greater root volume, projected area, and diameter for seedlings than cuttings grown plants. Our study successfully identified several key factors that should be considered for the ongoing management of P. hirsuta and vindicates the importance of small experimental trials when planning threatened plant translocations.

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Background and aims Field surveys across known populations of the Endangered Persoonia hirsuta (Proteaceae) in 2019 suggested the soil environment may be associated with dieback in this species. To explore how characteristics of the soil environment (e.g., pathogens, nutrients, soil microbes) relate to dieback, a soil bioassay (Experiment 1) was conducted using field soils from two dieback effected P. hirsuta populations. Additionally, a nitrogen addition experiment (Experiment 2) was conducted to explore how the addition of soil nitrogen impacts dieback. Methods The field soils were baited for pathogens, and soil physiochemical and microbial community characteristics were assessed and related to dieback among plants in the field and nursery-grown plants inoculated with the same field soils. Roots from inoculated plants were harvested to confirm the presence of soil pathogens and root-associated endophytes. Using these isolates, a dual culture antagonism assay was performed to examine competition among these microbes and identify candidate pathogens or pathogen antagonists. Results Dieback among plants in the field and Experiment 1 was associated with soil physiochemical properties (nitrogen and potassium), and soil microbes were identified as significant indicators of healthy and dieback-affected plants. Plants in Experiment 2 exhibited greater dieback when treated with elevated nitrogen. Additionally, post-harvest culturing identified fungi and other soil pathogens, some of which exhibited antagonistic behavior. Conclusion This study identified candidate fungi and soil physiochemical properties associated with observed dieback and dieback resistance in an Endangered shrub and provides groundwork for further exploring what drives dieback and how it can be managed to promote the conservation of wild populations.

Climate change and land management decisions have considerably altered fire regimes globally resulting in increased risks of extreme fire seasons. Fire intensity is one characteristic of fire regime which is projected to increase. However, the magnitude and impact of intense fires on plant habitat and life history characteristics (such as the soil environment or seedling recruitment) remain unclear for many species. The widespread 2019-2020 black summer fires across Eastern Australia provided the opportunity to examine the impact of these fires on the short-term regeneration of the endangered Persoonia hirsuta (Proteaceae), an obligate seeding (reliant on regeneration from seed following fire) shrub presently threatened by population decline and dieback (plant death from branch and root tips backwards) of an unknown cause. We measured fire severity in the field at 22 plots across three fire-affected populations which were used as a proxy to understand the relative impacts of fire intensity on P. hirsuta post-fire regeneration. We also recorded the post‐fire recruitment, growth, dieback and survival of P. hirsuta seedlings at these plots over 21 months and examined whether the post-fire soil environment was related to fire severity and post-fire seedling responses (recruitment, growth, dieback, and mortality). Seedling recruitment, and growth were variable across sites and showed no relationship to fire severity. However, seedling dieback and mortality were significantly higher among plots exposed to high severity fires. Additionally, characteristics of the post-fire soil environment varied by fire severity and explained variation in seedling recruitment, growth and dieback. Our work provides critical evidence that already vulnerable populations of P. hirsuta may be further threatened by increasing fire severity, highlighting the importance of understanding the effects of fire on habitat and life history characteristics for threatened plants.