Rachel Standish

1. Carbon plantings are a vital contribution to mitigate climate change. While plantings are primarily done for carbon sequestration, there is potential for biodiversity co-benefits, particularly when plantings mirror the local reference ecosystem and comprise a mix of native species with a variety of functional traits. With the continued rise of carbon plantings globally, the potential for biodiversity co-benefits also increases.

2. Biodiversity co-benefits are relevant to emerging biodiversity markets, new restoration laws in Europe and global aspirational goals for a Nature Positive future. Uncertainty among proponents is prevalent because measuring biodiversity co-benefits is more complex than measuring carbon sequestration. While there are standardised methodologies for measuring carbon sequestration, there is little guidance for practitioners on how to identify and quantify biodiversity co-benefits.

3. Here, we present practical guidelines, informed by a real-world case study, for identifying potential biodiversity values and their subsequent quantification in biodiverse carbon plantings. Key elements include desktop analyses to identify the landscape and ecosystem context, including threatened ecosystems and species, and threatening processes. We provide guidance on monitoring approaches for key abiotic and biotic ecosystem characteristics at baseline and reference states.

4. Practical implications. These guidelines allow integration of measured biodiversity outcomes with existing frameworks such as Natural Capital Accounting standards and Nature-related Financial Disclosure frameworks. These are increasingly implemented by businesses worldwide to assess and report their nature-related impacts, dependencies and risks. Together, these frameworks are necessary to ensure that corporations' financial investments in a Nature Positive future result in a net benefit for native ecosystems and people.

As droughts become longer and more intense, impacts on terrestrial primary productivity are expected to increase progressively. Yet, some ecosystems appear to acclimate to multiyear drought, with constant or diminishing reductions in productivity as drought duration increases. We quantified the combined effects of drought duration and intensity on aboveground productivity in 74 grasslands and shrublands distributed globally. Ecosystem acclimation with multiyear drought was observed overall, except when droughts were extreme (i.e., ≤1-in-100-year likelihood of occurrence). Productivity losses after four consecutive years of extreme drought increased by ~2.5-fold compared with those of the first year. These results portend a foundational shift in ecosystem behavior if drought duration and intensity increase, from maintenance of reduced functioning over time to progressive and profound losses of productivity when droughts are extreme.

The ability of restored sites to recover from subsequent disturbances is a key component of restoration success. Resilience is achieved when a restored site returns to its pre‐disturbance state, rather than shifts to a different one. In restored fire‐prone ecosystems, the drivers of post‐fire plant responses and resilience of plant assemblages to fire are underexplored. Exploration of these responses is used to predict and measure the resilience of restored ecosystems to disturbance, including whether the disturbance response was desirable or not. We implemented fine‐scale experimental fires in a post‐mining restoration chronosequence 14–27 years of age in Banksia woodlands, Western Australia. We sought to understand the effects of restoration age, fire impact, and soil conditions on post‐fire regeneration and survival of restored Banksia woodland plant assemblages. To assess early‐stage resilience to fire, we calculated four descriptors of ecosystem state: plant species density, species diversity, rarefied richness and functional redundancy, and compared how these changed following fire across the restoration ages and in comparison to nearby reference Banksia woodland. Ordinations and indicator species analyses were used to compare restored and reference sites. In restoration sites, restoration age, fire impact and soil conditions had little effect on plant regeneration and survival. Changes in diversity, rarefied richness and functional redundancy pre‐ to post‐fire in restored sites were typically similar to or less than that observed in reference sites. Broadly, our findings demonstrate the incomplete resilience of restored Banksia woodland to fire. Resprouters typically demonstrated poor resilience, through significant decreases in diversity and rarefied richness following fire in restored sites. They were under‐represented in restored Banksia woodlands, so further investigations into the establishment of resprouters in restored environments are required. Our findings also highlight the importance of utilising reference data and a broad range of descriptors to fully understand responses of restored plant assemblages to fire.

Global mining activities are critical for socio-economic prosperity yet threaten the biological diversity that underpins it. The risks of mining impacts on biodiversity are currently unknown because these impacts are underreported. The global ecosystem accounting standard offers a solution to monitor, mitigate, and report mining impacts comprehensively. This is urgently needed to achieve global targets to reverse biodiversity loss.

Mixed-species forestry is a promising approach to enhance productivity, increase carbon sequestration, and mitigate climate change. Diverse forests, composed of species with varying structures and functional trait profiles, may have higher functional and structural diversity, which are attributes relevant to a number of mechanisms that can influence productivity. However, it remains unclear whether the context-dependent roles of functional identity, functional diversity, and structural diversity can lead to a generalized understanding of tree diversity effects on stand productivity. To address these gaps, we analyzed growth data from 83,600 trees from 89 species across 21 young tree diversity experiments spanning five continents and three biomes. Results revealed a positive saturating relationship between tree species richness and stand productivity, with reduced variability in growth rates among more diverse stands. Structural equation modeling demonstrated that functional diversity mediated the positive effects of species richness on productivity. We additionally report a negative relationship between structural diversity and productivity, which decreased with increasing species richness. When partitioning net diversity effects, we found that selection effects played a dominant role in driving the overall increase in productivity in these predominantly young stands, contributing 77% of the net diversity effect. Selection effects increased with diversity in wood density. Furthermore, acquisitive species with lower wood density and higher leaf nitrogen content had higher productivity in more diverse stands, while conservative species showed neutral to slightly negative responses to species mixing. Together, these results suggest that combining acquisitive with conservative species allows acquisitive species to drive positive selection effects while conservative species tolerate competition. Thus, contrasting resource-use strategies can enhance productivity to optimize mixed-species forestry, with potential for both ecological and economic benefits.

Highlights
• Urban woody plantings can be maintained by coppicing, which stimulates resprouting.
• Coppiced and non-coppiced plants had similar survival in a common garden experiment.
• Species from drier regions had higher survival and maintained growth.
• Deeper rooted species had higher survival but lower vigour after coppicing.
• Woody plants from drier regions can create resilient urban plantings.

Woody plants can be used for resilient urban greening in cities with drying climates. Coppicing – regular cutting of plants to 10–20 cm aboveground – can be used to maintain plants in cities by stimulating resprouting and regeneration. Species selection could consider climate adjusted provenancing and the habitat template approach, yet little is known about how these methods translate to coppiced urban plantings. Therefore, we investigated resprouting survival and vigour of species from two bioregions with one representing the future climate of the other, and with a range of root traits. We also compared coppiced and non-coppiced plant survival and vigour under two watering regimes. Twenty-four woody species were grown in a common garden experiment for two years in southwestern Australia. There were four treatments based on water availability (summer watering and not watered) and coppicing (coppiced after one year and non-coppiced) with five replicates. Survival, vigour, and plant traits were measured on all plants after two years, including basal area, height, stem number, specific leaf area, total leaf area ratio, and root:shoot ratio. Coppiced (81 %) and non-coppiced (90 %) plants had similar survival, however survival of individual species was highly variable (range 0–100 %). Coppicing increased stem number and total leaf area. Summer watering increased survival of non-coppiced plants but did not change coppiced plant survival or traits. Species from the warmer and drier bioregion had the greatest survival in all treatments. Species with greater root:shoot ratio and/or with deeper roots had greater survival but lower vigour after coppicing. We found local plant communities were suitable for naturalistic woody plantings in an urban environment, and these could be maintained through coppicing. We suggest using climate adjusted provenancing and the habitat template approach, by using species from warmer and drier regions and with a range of root traits for short-term vigour and long-term survival.

Forests need to be resilient and adaptive in the face of global environmental change and mixed species forestry is a critical strategy for achieving this goal. It has been shown in many studies that mixed species forests can be more productive, more resilient to stress and disturbance while also providing a broader range of ecosystem services relative to mono-specific forests, yet the underlying mechanisms are not clear. Contrasting inter-specific functional trait expression and increased structural heterogeneity in mixtures may enhance community resource utilization, which could help explain synergistic effects on tree growth. Here, we conducted a meta-analysis of data from 21 tree diversity experiments across 5 continents to determine the extent to which mixed forestry can promote increased growth as measured by stand-level basal area and height mean annual increment. We then used structural-equation modeling to quantify the strength of linkages between species diversity and growth via vertical and horizontal structural heterogeneity, functional trait diversity, and functional stand composition. We will discuss our findings in terms of general growth trends identified, and potential mechanistic diversity-productivity pathways in tree species mixtures. The results can contribute to informing policy-makers and forest managers about the overall effectiveness of mixed forestry.

Arbuscular mycorrhizal fungi (AMF) facilitate ecosystem functioning through provision of plant hosts with phosphorus (P), especially where soil P is limiting. Changes in soil nutrient regimes are expected to impact AMF, but the direction of the impact may depend on context. We predicted that nitrogen (N)‐only enrichment promotes plant invasions and exacerbates their P limitation, increasing the utility of AMF and promoting AMF diversity. We expected that enrichment with N, P and other nutrients similarly promotes plant invasions, but decreases the benefit and diversity of AMF because P is readily available for both native and exotic plants. We tested these hypotheses in eucalypt woodlands of south‐western Australia, that occur on soils naturally low in P. We evaluated AMF communities within three modified ground‐layer states representing different types of nutrient enrichment and associated plant invasions. We compared these modified states to near‐natural reference woodlands. AMF richness varied across ground‐layer states. The moderately invaded/N‐enriched state showed the highest AMF richness, while the highly invaded/NP‐enriched state showed the lowest AMF richness. The reference state and the weakly invaded/enriched state were intermediate. AMF richness and colonisation were higher in roots of exotic than native plant species. AMF community composition differed among ground‐layer states, with the highly invaded/NP‐enriched state being most distinct. Distinctions among states were often driven by family‐level patterns. Reference and moderately invaded/N‐enriched states each supported distinct groups of zero‐radius operational taxonomic units (zOTUs) in Acaulosporaceae, Gigasporaceae and Glomeraceae, whereas Gigasporaceae and Glomeraceae were nearly absent from the highly invaded/NP‐enriched state. Further, Diversisporaceae and Glomeraceae were most diverse in the moderately invaded/N‐enriched state. Synthesis . Both the nature of soil nutrient enrichment and plant provenance matter for AMF. N‐only enrichment of low‐P soils increased AMF richness, likely due to the introduction of AMF‐dependent exotic plant species and exacerbation of their P limitation. In contrast, multi‐nutrient enrichment, decreased AMF richness potentially due to a decrease in host dependence on AMF, regardless of host provenance. The changes in AMF community composition with nutrient enrichment and plant invasion warrant further research into predicting the functional implications of these changes.

Background
Arbuscular mycorrhizas (AM) are the most widespread terrestrial symbiosis and are both a key determinant of plant health and a major contributor to ecosystem processes through their role in biogeochemical cycling. Until recently, it was assumed that the fungi which form AM comprise the subphylum Glomeromycotina (G-AMF), and our understanding of the diversity and ecosystem roles of AM is based almost exclusively on this group. However recent evidence shows that fungi which form the distinctive 'fine root endophyte’ (FRE) AM morphotype are members of the subphylum Mucoromycotina (M-AMF), so that AM symbioses are actually formed by two distinct groups of fungi.

Results
We investigated the influence of nitrogen (N) addition and wheat variety on the assembly of AM communities under field conditions. Visual assessment of roots showed co-occurrence of G-AMF and M-AMF, providing an opportunity to compare the responses of these two groups. Existing ‘AM’ 18S rRNA primers which co-amplify G-AMF and M-AMF were modified to reduce bias against Mucoromycotina, and compared against a new ‘FRE’ primer set which selectively amplifies Mucoromycotina. Using the AM-primers, no significant effect of either N-addition or wheat variety on G-AMF or M-AMF diversity or community composition was detected. In contrast, using the FRE-primers, N-addition was shown to reduce M-AMF diversity and altered community composition. The ASV which responded to N-addition were closely related, demonstrating a clear phylogenetic signal which was identified only by the new FRE-primers. The most abundant Mucoromycotina sequences we detected belonged to the same Endogonales clades as dominant sequences associated with FRE morphology in Australia, indicating that closely related M-AMF may be globally distributed.

Conclusions
The results demonstrate the need to consider both G-AMF and M-AMF when investigating AM communities, and highlight the importance of primer choice when investigating AMF community dynamics.