Publications

Studies evaluating plant-soil biota interactions in both native and introduced plant ranges are rare, and thus far have lacked robust experimental designs to account for several potential confounding factors. Here, we investigated the effects of soil biota on growth of Pinus contorta, which has been introduced from Canada to Sweden. Using Swedish and Canadian soils, we conducted two glasshouse experiments. The first experiment utilized unsterilized soil from each country, with a full-factorial cross of soil origin, tree provenance, and fertilizer addition. The second experiment utilized gamma-irradiated sterile soil from each country, with a full-factorial cross of soil origin, soil biota inoculation treatments, tree provenance, and fertilizer addition. The first experiment showed higher seedling growth on Swedish soil relative to Canadian soil. The second experiment showed this effect was due to differences in soil biotic communities between the two countries, and occurred independently of all other experimental factors. Our results provide strong evidence that plant interactions with soil biota can shift from negative to positive following introduction to a new region, and are relevant for understanding the success of some exotic forest plantations, and invasive and range-expanding native species.

Despite recent progress in understanding soil microbial responses to carbon (C) limitation, the functional shifts in microbial community structure associated with decreasing soil C availability and changes in organic matter chemistry remain poorly known. It has been proposed that Gram-negative (GN) bacteria use more plant-derived C sources that are relatively labile, while Gram-positive (GP) bacteria use C sources derived from soil organic matter that are more recalcitrant. Because these two groups may differ in how they influence the fate of different C forms in soils, it is important to understand how they vary across ecosystems that differ in their vegetation cover and ecosystem productivity or across environmental gradients. In this study, we used a 19-year plant functional group removal experiment across a long term post-fire chronosequence to assess how microbial community structure (assessed using phospholipids fatty acids; PLFAs) and the association of bacterial functional groups (specifically, the GP:GN ratio) responded to changes in organic matter chemistry (measured via nuclear magnetic resonance; NMR). We found that the GP:GN ratio increased upon removal of shrubs and tree roots and with decreasing ecosystem productivity along the chronosequence, thus showing the greater dependence of GN than GP bacteria on more labile plant-derived C. Overall, GN bacteria were associated with simple C compounds (alkyls) whereas GP bacteria were more strongly associated with more complex C forms (carbonyls). Therefore, we conclude that the GP:GN ratio has potential as a useful indicator of the relative C availability for soil bacterial communities in organic soils, and can be used as a coarse indicator of energy limitation in natural ecosystems.

Degraded tropical peat swamp forests are harsh environments so difficult to restore. Evidence from past restoration projects can inform selection of species for planting. As part of a systematic review, we collated and synthesised survival and growth monitoring data on trees planted in degraded tropical peat swamp forests across Southeast Asia. A key aim of the systematic review and meta-analysis was to determine which tree species survive best when planted to restore tropical peat swamp forests. We also investigated the impact of seedling and site treatments and climatic conditions (El Niño-Southern Oscillation) on tree seedling survival and growth and the potential to use plant functional traits to predict survival and growth. Full methodological details of the systematic review, including: search strategy, article screening and inclusion criteria, critical appraisal of screened articles, data processing and data analysis can be found in the published article and supporting information stated below. Smith SW, Rahman NEB, Harrison ME, Shiodera S, Giesen W, Lampela M, Wardle DA, Chong KY, Randi A, Wijedasa LS, Teo PY, Fatimah, YA, Teng NT, Joanne YKQ, Alam MJ, Brugues Sintes P, Darusman T, Graham LLB, Katoppo DR, Kojima K, Kusin K, Lestari DP, Metali F, Morrogh-Bernard HC, Nahor MB, Napitupulu RRP, Nasir D, Nath TK, Nilus R, Norisada M, Rachmanadi D, Rachmat HH, Ripoll Capilla B, Salahuddin, Santosa PB, Sukri RS, Tay B, Tuah W, Wedeux, BMM, Yamanoshita T, Yokoyama EY, Yuwati TW, Lee JSH. Tree species that ‘live slow, die older’ enhance tropical peat swamp restoration: evidence from a systematic review. <em>Journal of Applied Ecology. </em>DOI:10.1111/1365-2664.14232 In this data repository, we have uploaded the following data used in the meta-analysis to generate the findings presented in the systematic review, specifically: Screening sheets of eligible articles across languages (English, Indonesian, Japanese and German) read in detailed by multiple authors on the review Survival monitoring data, including predicted half-life (duration until 50% mortality) derived from functional line-fitting Height monitoring data, including standardized relative growth rates (cm × cm^-1month^-1) derived from functional line-fitting Plant functional traits, selected leaf nutrient contents and wood densities for those species used in the functional trait analyses Each data file has an associated meta-data file explaining the column headers and variables. Please note, data contributors from some studies wished to retain control over access to their monitoring data, but are willing to share this data on request. The relevant study-site code those studies used in the analyses in our systematic review can be found in the meta-data sheets. Details given include study-site code (used in the systematic review), site name and location, author name(s), author contact email(s). All these details have been provided with permission from relevant data contributor co-author(s).

Decomposition and fire are major carbon pathways in many ecosystems, yet the contribution of species identity to these processes can be difficult to predict. Plant decomposability and flammability have usually been studied separately but could be linked through shared predictive traits. We explored how decomposability and flammability were related to each other and to key plant functional traits in a tropical swamp forest in Singapore. Full methodological details <em>in situ</em> decomposition experiment in Nee Soon freshwater swamp forest, Singapore, laboratory flammability experiment, and leaf functional trait measurements can be found in the published article and supporting information stated below. Nur E. B. Rahman, Stuart W. Smith, Weng Ngai Lam, Kwek Yan Chong, Matthias S. E. Chua, Pei Yun Teo, Daniel W. J. Lee, Shi Yu Phua, Cheryl Y. Aw, Janice S. H. Lee, David A. Wardle. Leaf decomposition and flammability are largely decoupled across species in a tropical swamp forest despite sharing some predictive leaf functional traits. <em>New Phytologist</em> In this data repository, we have uploaded the following decomposition, flammability and trait data as well as secondary data used in our statistical analyses to generate the findings presented in the paper. Specific datasets include the following: litter_mass_loss.csv : raw data of leaf litterbag dry masses before and after 1 year in situ decomposition experiment in Nee Soon Swamp Forest flammability_leaf_temperature.csv : raw data of temperature recorded during flammability experiments of leaf litter and fresh leaves flammability_timings.csv : raw data of timings of flammability events, namely smouldering and pyrolysis recorded from video footage of flammability experiments senesced_leaf_dryweights_area.csv : senesced leaf raw data for calculating physical traits senesced_leaf_dryweights.csv: senesced leaf dry weights raw data freshtraits_measurements.csv: fresh leaf raw data for calculating physical traits decomposition_constants.csv: derived decomposition constants (k) for each species from the analysis of decomposition experiments. functional_traits_z_standardized.csv : all traits required for the analysis, consolidated following z-standardized transformation functional_traits_untransformed_decomposition_flammability.csv : all traits required for the analysis, untransformed (for back transforming axis labels) and species decomposition and flammability variables Raw leaf litter mass loss and leaf flammability data are associated meta-data file explaining the column headers and variables. For all other datasets please refer to the paper and supporting information.

Humans are altering the composition of biological communities through a variety of activities that increase rates of species invasions and species extinctions, at all scales, from local to global. These changes in components of the Earth's biodiversity cause concern for ethical and aesthetic reasons, but they also have a strong potential to alter ecosystem properties and the goods and services they provide to humanity. Ecological experiments, observations, and theoretical developments show that ecosystem properties depend greatly on biodiversity in terms of the functional characteristics of organisms present in the ecosystem and the distribution and abundance of those organisms over space and time. Species effects act in concert with the effects of climate, resource availability, and disturbance regimes in influencing ecosystem properties. Human activities can modify all of the above factors; here we focus on modification of these biotic controls. The scientific community has come to a broad consensus on many aspects of the relationship between biodiversity and ecosystem functioning, including many points relevant to management of ecosystems. Further progress will require integration of knowledge about biotic and abiotic controls on ecosystem properties, how ecological communities are structured, and the forces driving species extinctions and invasions. To strengthen links to policy and management, we also need to integrate our ecological knowledge with understanding of the social and economic constraints of potential management practices. Understanding this complexity, while taking strong steps to minimize current losses of species, is necessary for responsible management of Earth's ecosystems and the diverse biota they contain. Based on our review of the scientific literature, we are certain of the following conclusions: 1) Species' functional characteristics strongly influence ecosystem properties. Functional characteristics operate in a variety of contexts, including effects of dominant species, keystone species, ecological engineers, and interactions among species (e.g., competition, facilitation, mutualism, disease, and predation). Relative abundance alone is not always a good predictor of the ecosystem-level importance of a species, as even relatively rare species (e.g., a keystone predator) can strongly influence pathways of energy and material flows. 2) Alteration of biota in ecosystems via species invasions and extinctions caused by human activities has altered ecosystem goods and services in many well-documented cases. Many of these changes are difficult, expensive, or impossible to reverse or fix with technological solutions. 3) The effects of species loss or changes in composition, and the mechanisms by which the effects manifest themselves, can differ among ecosystem properties, ecosystem types, and pathways of potential community change. 4) Some ecosystem properties are initially insensitive to species loss because (a) ecosystems may have multiple species that carry out similar functional roles, (b) some species may contribute relatively little to ecosystem properties, or (c) properties may be primarily controlled by abiotic environmental conditions. 5) More species are needed to insure a stable supply of ecosystem goods and services as spatial and temporal variability increases, which typically occurs as longer time periods and larger areas are considered. We have high confidence in the following conclusions: 1) Certain combinations of species are complementary in their patterns of resource use and can increase average rates of productivity and nutrient retention. At the same time, environmental conditions can influence the importance of complementarity in structuring communities. Identification of which and how many species act in a complementary way in complex communities is just beginning. 2) Susceptibility to invasion by exotic species is strongly influenced by species composition and, under similar environmental conditions, generally decreases with increasing species richness. However, several other factors, such as propagule pressure, disturbance regime, and resource availability also strongly influence invasion success and often override effects of species richness in comparisons across different sites or ecosystems. 3) Having a range of species that respond differently to different environmental perturbations can stabilize ecosystem process rates in response to disturbances and variation in abiotic conditions. Using practices that maintain a diversity of organisms of different functional effect and functional response types will help preserve a range of management options. Uncertainties remain and further research is necessary in the following areas: 1) Further resolution of the relationships among taxonomic diversity, functional diversity, and community structure is important for identifying mechanisms of biodiversity effects. 2) Multiple trophic levels are common to ecosystems but have been understudied in biodiversity/ecosystem functioning research. The response of ecosystem properties to varying composition and diversity of consumer organisms is much more complex than responses seen in experiments that vary only the diversity of primary producers. 3) Theoretical work on stability has outpaced experimental work, especially field research. We need long-term experiments to be able to assess temporal stability, as well as experimental perturbations to assess response to and recovery from a variety of disturbances. Design and analysis of such experiments must account for several factors that covary with species diversity. 4) Because biodiversity both responds to and influences ecosystem properties, understanding the feedbacks involved is necessary to integrate results from experimental communities with patterns seen at broader scales. Likely patterns of extinction and invasion need to be linked to different drivers of global change, the forces that structure communities, and controls on ecosystem properties for the development of effective management and conservation strategies. 5) This paper focuses primarily on terrestrial systems, with some coverage of freshwater systems, because that is where most empirical and theoretical study has focused. While the fundamental principles described here should apply to marine systems, further study of that realm is necessary. Despite some uncertainties about the mechanisms and circumstances under which diversity influences ecosystem properties, incorporating diversity effects into policy and management is essential, especially in making decisions involving large temporal and spatial scales. Sacrificing those aspects of ecosystems that are difficult or impossible to reconstruct, such as diversity, simply because we are not yet certain about the extent and mechanisms by which they affect ecosystem properties, will restrict future management options even further. It is incumbent upon ecologists to communicate this need, and the values that can derive from such a perspective, to those charged with economic and policy decision-making.

The ecological consequences of biodiversity loss have aroused considerable interest and controversy during the past decade. Major advances have been made in describing the relationship between species diversity and ecosystem processes, in identifying functionally important species, and in revealing underlying mechanisms. There is, however, uncertainty as to how results obtained in recent experiments scale up to landscape and regional levels and generalize across ecosystem types and processes. Larger numbers of species are probably needed to reduce temporal variability in ecosystem processes in changing environments. A major future challenge is to determine how biodiversity dynamics, ecosystem processes, and abiotic factors interact.

Increasing evidence suggests that specific interactions between microbial decomposers and plant litter, named home‐field advantage (HFA), influence litter breakdown. However, we still have limited understanding of whether HFA relates to specific microbiota, and whether specialized microbes originate from the soil or from the leaf microbiome. Here, we disentangle the roles of soil origin, litter types and the microbial community already present on the leaf litter in determining fungal community composition on decomposing leaf litter and HFA. We collected litters and associated soil samples from a secondary succession gradient ranging from herbaceous vegetation on recently abandoned ex‐arable fields to forest representing the end stage of succession. In a greenhouse, sterilized and unsterilized leaf litters were decomposed for 12 months in soils from early‐ to late‐successional stages according to a full‐factorial design. At the end, we examined fungal community composition on the decomposing litter. Fungal communities on decomposed late‐successional litter in late‐successional soil differed from those in early‐ and mid‐successional stage litter and soil combinations. Soil source had the strongest impact on litter fungal composition when using sterilized litter, while the impact of litter type was strongest when using unsterilized litter. Overall, we observed HFA, as litter decomposition was accelerated in home soils. Increasing HFA did not relate to the dissimilarity in overall fungal composition, but there was increasing dissimilarity in the relative abundance of the most dominant fungal taxon between decomposing litter in home and away soils. We conclude that early‐, mid‐ and late‐succession litter types did not exert strong selection effects on colonization by micro‐organisms from the soil species pool. Instead, fungal community composition on decomposing litter differed substantially between litter types for unsterilized litter, suggesting that the leaf microbiome, either directly or indirectly, is an important determinant of fungal community composition on decomposing leaves. HFA related most strongly to the abundance of the most dominant fungal taxa on the decomposing litter, suggesting that HFA may be attributed to some specific dominant fungi rather than to responses of the whole fungal community. A plain language summary is available for this article.

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Functional trait plasticity is a major component of plant adjustment to environmental stresses. Here, we explore how multiple local environmental gradients in resources required by plants (light, water, and nutrients) and soil disturbance together influence the direction and amplitude of intraspecific changes in leaf and fine root traits that facilitate capture of these resources. We measured population‐level analogous above‐ and belowground traits related to resource acquisition, i.e. “specific leaf area”–“specific root length” ( SLA – SRL ), and leaf and root N, P, and dry matter content ( DMC ), on three dominant understory tree species with contrasting carbon and nutrient economics across 15 plots in a temperate forest influenced by burrowing seabirds. We observed similar responses of the three species to the same single environmental influences, but partially species‐specific responses to combinations of influences. The strength of intraspecific above‐ and belowground trait responses appeared unrelated to species resource acquisition strategy. Finally, most analogous leaf and root traits ( SLA vs. SRL , and leaf versus root P and DMC ) were controlled by contrasting environmental influences. The decoupled responses of above‐ and belowground traits to these multiple environmental factors together with partially species‐specific adjustments suggest complex responses of plant communities to environmental changes, and potentially contrasting feedbacks of plant traits with ecosystem properties. We demonstrate that despite the growing evidence for broadly consistent resource‐acquisition strategies at the whole plant level among species, plants also show partially decoupled, finely tuned strategies between above‐ and belowground parts at the intraspecific level in response to their environment. This decoupling within species suggests a need for many species‐centred ecological theories on how plants respond to their environments (e.g. competitive/stress‐tolerant/ruderal and response‐effect trait frameworks) to be adapted to account for distinct plant‐environment interactions among distinct individuals of the same species and parts of the same individual.

Concern about the functional consequences of unprecedented loss in biodiversity has prompted biodiversity–ecosystem functioning (BEF) research to become one of the most active fields of ecological research in the past 25 years. Hundreds of experiments have manipulated biodiversity as an independent variable and found compelling support that the functioning of ecosystems increases with the diversity of their ecological communities. This research has also identified some of the mechanisms underlying BEF relationships, some context-dependencies of the strength of relationships, as well as implications for various ecosystem services that humankind depends upon. In this chapter, we argue that a multitrophic perspective of biotic interactions in random and non-random biodiversity change scenarios is key to advance future BEF research and to address some of its most important remaining challenges. We discuss that the study and the quantification of multitrophic interactions in space and time facilitates scaling up from small-scale biodiversity manipulations and ecosystem function assessments to management-relevant spatial scales across ecosystem boundaries. We specifically consider multitrophic conceptual frameworks to understand and predict the context-dependency of BEF relationships. Moreover, we highlight the importance of the eco-evolutionary underpinnings of multitrophic BEF relationships. We outline that FAIR data (meeting the standards of findability, accessibility, interoperability, and reusability) and reproducible processing will be key to advance this field of research by making it more integrative. Finally, we show how these BEF insights may be implemented for ecosystem management, society, and policy. Given that human well-being critically depends on the multiple services provided by diverse, multitrophic communities, integrating the approaches of evolutionary ecology, community ecology, and ecosystem ecology in future BEF research will be key to refine conservation targets and develop sustainable management strategies.