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Contents I. II. III. IV. V. VI. VII. References Summary: Biological decomposition and wildfire are connected carbon release pathways for dead plant material: slower litter decomposition leads to fuel accumulation. Are decomposition and surface fires also connected through plant community composition, via the species' traits? Our central concept involves two axes of trait variation related to decomposition and fire. The 'plant economics spectrum' (PES) links biochemistry traits to the litter decomposability of different fine organs. The 'size and shape spectrum' (SSS) includes litter particle size and shape and their consequent effect on fuel bed structure, ventilation and flammability. Our literature synthesis revealed that PES-driven decomposability is largely decoupled from predominantly SSS-driven surface litter flammability across species; this finding needs empirical testing in various environmental settings. Under certain conditions, carbon release will be dominated by decomposition, while under other conditions litter fuel will accumulate and fire may dominate carbon release. Ecosystem-level feedbacks between decomposition and fire, for example via litter amounts, litter decomposition stage, community-level biotic interactions and altered environment, will influence the trait-driven effects on decomposition and fire. Yet, our conceptual framework, explicitly comparing the effects of two plant trait spectra on litter decomposition vs fire, provides a promising new research direction for better understanding and predicting Earth surface carbon dynamics.

Bark shedding is a remarkable feature of Australian trees, yet relatively little is known about interspecific differences in bark decomposability and flammability, or what chemical or physical traits drive variation in these properties. We measured the decomposition rate and flammability (ignitibility, sustainability and combustibility) of bark from 10 common forest tree species, and quantified correlations with potentially important traits. We compared our findings to those for leaf litter, asking whether the same traits drive flammability and decomposition in different tissues, and whether process rates are correlated across tissue types. Considerable variation in bark decomposability and flammability was found both within and across species. Bark decomposed more slowly than leaves, but in both tissues lignin concentration was a key driver. Bark took longer to ignite than leaves, and had longer mass-specific flame durations. Variation in flammability parameters was driven by different traits in the different tissues. Decomposability and flammability were each unrelated, when comparing between the different tissue types. For example, species with fast-decomposing leaves did not necessarily have fast-decomposing bark. For the first time, we show how patterns of variation in decomposability and flammability of bark diverge across multiple species. By taking species-specific bark traits into consideration there is potential to make better estimates of wildfire risks and carbon loss dynamics. This can lead to better informed management decisions for Australian forests, and eucalypt plantations, worldwide.

There is considerable evidence that both plant diversity and plant identity can influence the level of predation and predator abundance aboveground. However, how the level of predation in the soil and the abundance of predatory soil fauna are related to plant diversity and identity remains largely unknown. In a biodiversity field experiment, we examined the effects of plant diversity and identity on the infectivity of entomopathogenic nematodes (EPNs, Heterorhabditis and Steinernema spp.), which prey on soil arthropods, and abundance of carnivorous non-EPNs, which are predators of other nematode groups. To obtain a comprehensive view of the potential prey/food availability, we also quantified the abundance of soil insects and nonpredatory nematodes and the root biomass in the experimental plots. We used structural equation modeling (SEM) to investigate possible pathways by which plant diversity and identity may affect EPN infectivity and the abundance of carnivorous non-EPNs. Heterorhabditis spp. infectivity and the abundance of carnivorous non-EPNs were not directly related to plant diversity or the proportion of legumes, grasses and forbs in the plant community. However, Steinernema spp. infectivity was higher in monocultures of Festuca rubra and Trifolium pratense than in monocultures of the other six plant species. SEM revealed that legumes positively affected Steinernema infectivity, whereas plant diversity indirectly affected the infectivity of Heterorhabditis EPNs via effects on the abundance of soil insects. The abundance of prey (soil insects and root-feeding, bacterivorous, and fungivorous nematodes) increased with higher plant diversity. The abundance of prey nematodes was also positively affected by legumes. These plant community effects could not be explained by changes in root biomass. Our results show that plant diversity and identity effects on belowground biota (particularly soil nematode community) can differ between organisms that belong to the sa

1. In natural ecosystems, plants containing hosts for parasitoids are often embedded within heterogeneous plant communities. These plant communities surrounding host-infested plants may influence the host-finding ability of parasitoids. 2. A release-recapture-approach was used to examine whether the diversity and structural complexity of the community surrounding a host-infested plant influences the aggregation behaviour of the leaf-miner parasitoid Dacnusa sibirica Telenga and naturally occurring local leaf-miner parasitoids. Released and locally present parasitoids were collected on potted Jacobaea vulgaris Gaertn.plants infested with the generalist leaf-miner Chromatomyia syngenesiae Hardy. The plants were placed in experimentally established plant communities differing in plant diversity (1–9 species) and habitat complexity (bare ground, mown vegetation, and tall vegetation). Additionally, parasitoids were reared out from host mines on the trap plants. 3. Plant diversity did not influence the mean number of recaptured D. sibirica or captures of other locally present parasitoids but the number of recaptured parasitoids was influenced by habitat complexity. No D. sibirica parasitoids were recaptured in the bare ground plots or plots with mown vegetation. The mean number of recaptured D. sibirica generally increased with increasing complexity of the plant community, whereas locally present parasitoids were captured more frequently in communities with more bare ground. There was a unimodal relationship between the number of reared out parasitoids and diversity of the surrounding vegetation with the highest density of emerged parasitoids at intermediate diversity levels. 4. The present study adds to the thus far limited body of literature examining the aggregation behaviour of parasitoids in the field and suggests that the preference of parasitoids to aggregate in complex versus simple vegetation is association specific and thus depends on

The diversity of plant community can greatly affect the abundance and diversity of arthropods associated to that community, but can also influence the composition or abundance of arthropods on individual plants growing in that community. We sampled arthropods and recorded plant size of individual ragwort, Jacobaea vulgaris Gaertner ssp. vulgaris [synonym Senecio jacobaea L. (Asteraceae)], plants transplanted into 70 experimental grassland plots that differed in plant diversity (1–9 species) or that were kept without vegetation. The arthropod fauna was dominated by the specialist aphid Aphis jacobaeae Schrank (Hemiptera: Aphididae). The abundance of aphids on ragwort plants decreased significantly with increasing plant diversity. The abundance of other arthropod species was not affected by the diversity of the surrounding plant community. Plant size was also not affected by the diversity of the surrounding plant community, but varied significantly among monocultures. Ragwort plants were largest in monocultures of legumes. Aphid abundance on ragwort plants, however, was not related to the size of the individual ragwort plants, but was high in monocultures consisting of Tanacetum vulgare L. (Asteraceae) plants. This plant is morphologically similar to ragwort. Even though we observed significant effects of plant diversity, ragwort plants were considerably larger – and the abundance of aphids and other arthropods on ragwort plants substantially higher – in plots without vegetation than in vegetated plots. Our results show that the presence and the diversity of neighbouring plants can provide associational resistance to focal plants growing in that community. We conclude that the surrounding plant community directly affects the abundance of arthropods on focal ragwort plants, and not via the effects of neighbouring plants on the performance of the focal plants., The diversity of plant community can greatly affect the abundance and diversity of arthropods associated to that community, but can also influence the composition or abundance of arthropods on individual plants growing in that community. We sampled arthropods and recorded plant size of individual ragwort, Jacobaea vulgaris Gaertner ssp. vulgaris [synonym Senecio jacobaea L. (Asteraceae)], plants transplanted into 70 experimental grassland plots that differed in plant diversity (1–9 species) or that were kept without vegetation. The arthropod fauna was dominated by the specialist aphid Aphis jacobaeae Schrank (Hemiptera: Aphididae). The abundance of aphids on ragwort plants decreased significantly with increasing plant diversity. The abundance of other arthropod species was not affected by the diversity of the surrounding plant community. Plant size was also not affected by the diversity of the surrounding plant community, but varied significantly among monocultures. Ragwort plants were largest in monocultures of legumes. Aphid abundance on ragwort plants, however, was not related to the size of the individual ragwort plants, but was high in monocultures consisting of Tanacetum vulgare L. (Asteraceae) plants. This plant is morphologically similar to ragwort. Even though we observed significant effects of plant diversity, ragwort plants were considerably larger – and the abundance of aphids and other arthropods on ragwort plants substantially higher – in plots without vegetation than in vegetated plots. Our results show that the presence and the diversity of neighbouring plants can provide associational resistance to focal plants growing in that community. We conclude that the surrounding plant community directly affects the abundance of arthropods on focal ragwort plants, and not via the effects of neighbouring plants on the performance of the focal plants.