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Nutrient cycling through leaf litter consumption is an essential ecological function performed by macrodetritivorous invertebrates such as isopods and millipedes. Leaf litter consumption rates can vary greatly depending on the environment, consumer identity and litter traits, but generalizations about the effects of plant traits on macrodetritivore leaf litter consumption, assimilation and growth are not well established and are mostly indirectly inferred.We conducted a systematic search of the global literature and obtained 456 standardized measures from laboratory experiments of relative consumption (RCR), assimilation (RAR) and growth (RGR) rates of terrestrial isopods and millipedes, extracted from 56 different articles. We investigated if commonly measured leaf traits, plant functional groups, prior microbial conditioning of leaves and climatic conditions affected these rates. We obtained data on commonly measured leaf traits from the TRY global plant trait database, inferred plant functional groups from taxonomic groupings and obtained climatic data from information reported within articles.RCR, RAR and RGR varied greatly among macrodetritivore and plant species, but overall, there were no differences between isopods and millipedes. Microbial conditioning of litter greatly increased RCR. Plant functional group was an important predictor of RCR, with eudicot trees and forbs being consumed in greater quantities than magnoliid trees and grasses. Fresh leaf N:P ratio had a positive effect on RAR, and leaf N and C:N ratio had positive and negative effects on RGR, respectively, while climatic variables had weak effects on the three rates.Our work shows that plant traits (both those associated with plant functional groups and commonly measured leaf traits) exert strong effects on resource processing rates by terrestrial macrodetritivores. Further, prior microbial conditioning of leaf litter has a large and globally consistent positive effect on macrodetritivore litter consumption, suggesting that they may consume little, if any, freshly senesced leaf material when microbially conditioned litter is available. Our results suggest that, where extremes of temperature or precipitation do not occur, variables reflective of food quality (leaf traits and microbe conditioning) are more important drivers of macrodetritivore leaf litter consumption than are extrinsic climatic variables. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Summary: Differences in demographic and environmental niches facilitate plant species coexistence in tropical forests. However, the adaptations that enable species to achieve higher demographic rates (e.g. growth or survival) or occupy unique environmental niches (e.g. waterlogged conditions) remain poorly understood. Anatomical traits may better predict plant environmental and demographic strategies because they are direct measurements of structures involved in these adaptations.We collected 18 leaf and twig traits from 29 tree species in a tropical freshwater swamp forest in Singapore. We estimated demographic parameters of the 29 species from growth and survival models, and degree of association toward swamp habitats. We examined pairwise trait–trait, trait–demography and trait–environment links while controlling for phylogeny.Leaf and twig anatomical traits were better predictors of all demographic parameters than other commonly measured leaf and wood traits. Plants with wider vessels had faster growth rates but lower survival rates. Leaf and spongy mesophyll thickness predicted swamp association.These findings demonstrate the utility of anatomical traits as indicators of plant hydraulic strategies and their links to growth–mortality trade‐offs and waterlogging stress tolerance that underlie species coexistence mechanisms in tropical forest trees. [ABSTRACT FROM AUTHOR]

Summary: Decomposition and fire are major carbon pathways in many ecosystems, yet potential linkages between these processes are poorly understood. We test whether variability in decomposability and flammability across species are related to each other and to key plant functional traits in tropical swamp forests, where habitat degradation is elevating decomposition and fire regimes.Using senesced and fresh leaves of 22 swamp tree species in Singapore, we conducted an in situ decomposition experiment and a laboratory flammability experiment. We analysed 16 leaf physical and biochemical traits as predictors of decomposability and components of flammability: combustibility, ignitability and sustainability.Decomposability and flammability were largely decoupled across species, despite some shared predictive traits such as specific leaf area (SLA). Physical traits predicted that thicker leaves with a smaller SLA and volume decomposed faster, while various cation concentrations predicted flammability components, particularly ignitability.We show that flammability and decomposability of swamp forest leaves are decoupled because flammability is mostly driven by biochemical traits, while decomposition is driven by physical traits. Our approach identifies species that are slow to decompose and burn (e.g. Calophyllum tetrapterum and Xanthophyllum flavescens), which could be planted to mitigate carbon losses in tropical swamp reforestation. [ABSTRACT FROM AUTHOR]

Tropical pitcher plants (Nepenthes) are carnivorous plants that trap and digest prey using highly modified fluid-filled leaves known as pitchers. Prey are digested by plant-secreted enzymes and pitcher symbionts. Pitchers exert control over abiotic properties of the digestive fluid such as pH levels that can influence its symbionts. Here we examine natural variation in pH and dissolved mineral concentrations in three sympatric Nepenthes species, assessing correlations between fluid properties and pitcher traits. We use addition experiments to investigate differences in protein digestion/absorption rates between species. Fluid pH and dissolved mineral levels both showed distinct patterns corresponding to pitcher developmental stages in N. gracilis and N. rafflesiana, whereas N. ampullaria differs from its congeners in exhibiting far less variation in fluid pH, as well as less clear evidence of protein depletion. This study further elucidates the properties of pitchers as habitats, revealing ways in which the host plant regulates that habitat. [ABSTRACT FROM AUTHOR]

Using black soldier fly (Hermetia illucens [L.], Diptera: Stratiomyidae) larvae (BSFL) to upcycle urban solid waste into a growing medium for vegetable cultivation is a potential solution to ease cities' over-reliance on food imports and excessive waste generation. However, rapid composting by BSFL may be insufficient to remove phytotoxins from the waste and further composting may be necessary. Through a growth experiment on pak choi (Brassica rapa), this study evaluated the optimum performance of BSFL frass at three composting stages (freshly produced, composted with forced aeration and naturally composted in larval rearing chambers) in biochar-based substrate cultivation. Plants cultivated in the composted BSFL frass treatments grew larger than those in fresh frass, with 10% naturally composted BSFL frass (v/v) producing the most biomass among all treatments. A seed germination test suggested the presence of phytotoxins in the fresh frass and frass Fourier-transform infrared spectroscopy (FTIR) analysis showed that the fresh frass potentially had the highest phenol concentration. In terms of greenhouse gas emission, a life cycle analysis showed that all three types of frass had a lower global warming potential compared to incineration, with the fresh frass having the lowest emission, the frass composted using forced aeration having the second lowest and the naturally composted frass, the highest emission. Therefore, further composting of BSFL frass with forced aeration would be the most feasible method considering both its compost quality and environmental impact. Image 1 • Black soldier fly larvae (BSFL) frass tested as a sustainable compost. • Rapid composting by BSFL resulted in immature compost. • Further composting increased available nutrients and reduced phytotoxin content. • Pak choi grown in 10–30% BSFL frass (v/v) achieved the highest yields. • Compared to incineration, composted BSFL frass had a lower GWP. [ABSTRACT FROM AUTHOR]

The modified-leaf pitchers of Nepenthes rafflesiana pitcher plants are aquatic, allochthonous ecosystems that are inhabited by specialist inquilines and sustained by the input of invertebrate prey. Detritivorous inquilines are known to increase the nutrient-cycling efficiency (NCE) of pitchers but it is unclear whether predatory inquilines that prey on these detritivores decrease the NCE of pitchers by reducing detritivore populations or increase the NCE of pitchers by processing nutrients that may otherwise be locked up in detritivore biomass. Nepenthosyrphus is a small and poorly studied genus of hoverflies and the larvae of one such species is a facultatively detritivorous predator that inhabits the pitchers of N. rafflesiana . We fitted a consumer-resource model to experimental data collected from this system. Simulations showed that systems containing the predator at equilibrium almost always had higher NCEs than those containing only prey (detritivore) species. We showed using a combination of simulated predator/prey exclusions that the processing of the resource through multiple pathways and trophic levels in this system is more efficient than that accomplished through fewer pathways and trophic levels. Our results thus support the vertical diversity hypothesis, which predicts that greater diversity across trophic levels results in greater ecosystem functioning.

The fluids of Nepenthes pitcher plants are habitats to many specialized animals known as inquilines, which facilitate the conversion of prey protein into pitcher-absorbable nitrogen forms such as ammonium. Xenoplatyura beaveri (Diptera: Mycetophilidae) is a predatory dipteran inquiline that inhabits the pitchers of Nepenthes ampullaria Larvae of X. beaveri construct sticky webs over the fluid surface of N. ampullaria to ensnare emerging adult dipteran inquilines. However, the interaction between X. beaveri and its host has never been examined before, and it is not known if X. beaveri can contribute to nutrient sequestration in N. ampullaria. Xenoplatyura beaveri individuals were reared in artificial pitchers in the laboratory on a diet of emergent Tripteroides tenax mosquitoes, and the ammonium concentration of the pitcher fluids was measured over time. Fluid ammonium concentration in tubes containing X. beaveri was significantly greater than those of the controls. Furthermore, fluid ammonium concentrations increased greatly after X. beaveri larvae metamorphosed, although the cause of this increase could not be identified. Our results show that a terrestrial, inquiline predator can contribute significantly to nutrient sequestration in the phytotelma it inhabits, and suggest that this interaction has a net mutualistic outcome for both species., (© 2018 The Author(s).)

The fluid-containing traps of Nepenthes carnivorous pitcher plants (Nepenthaceae) are often inhabited by organisms known as inquilines. Dipteran larvae are key components of such communities and are thought to facilitate pitcher nitrogen sequestration by converting prey protein into inorganic nitrogen, although this has never been demonstrated in Nepenthes Pitcher fluids are also inhabited by microbes, although the relationship(s) between these and the plant is still unclear. In this study, we examined the hypothesis of digestive mutualism between N. gracilis pitchers and both dipteran larvae and fluid microbes. Using dipteran larvae, prey and fluid volumes mimicking in situ pitcher conditions, we conducted in vitro experiments and measured changes in available fluid nitrogen in response to dipteran larvae and microbe presence. We showed that the presence of dipteran larvae resulted in significantly higher and faster releases of ammonium and soluble protein into fluids in artificial pitchers, and that the presence of fluid microbes did likewise for ammonium. We showed also that niche segregation occurs between phorid and culicid larvae, with the former fragmenting prey carcasses and the latter suppressing fluid microbe levels. These results clarify the relationships between several key pitcher-dwelling organisms, and show that pitcher communities facilitate nutrient sequestration in their host., (© 2017 The Author(s).)