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Drought can induce phenotypic plasticity in a range of plant root and shoot traits. These traits have been shown to explain differences in root and shoot litter decomposability between species. However, it is unknown how drought-induced plasticity of root and shoot traits alters their decomposability. To investigate this issue across a range of species, we grew a grass Lolium perenne, a forb Plantago lanceolata and a legume Trifolium repens common to European temperate grasslands and subjected them to a 5-week moderate drought treatment. We compared morphological and chemical root and shoot traits of the droughted plants to well-watered controls. We then conducted a decomposition assay of the senesced root and shoot material over 16 weeks, with mass loss measurements at five timepoints. Drought had significant and sometimes strong effects on morphological and chemical root and shoot traits of all three species, sometimes similar to differences between species and generally in line with a shift to a more resource-conservative strategy. Drought also increased the labile litter fraction in roots of Lolium perenne, which was associated with a substantial increase in non-structural carbohydrates. Drought decreased the labile litter fraction in shoots of Plantago lanceolata, but this could not be explained by the traits we measured. Drought effects on litter decomposability were weaker than on plant traits. Our results suggest that plant trait-mediated effects of drought on litter decomposability can either increase or decrease vegetation feedbacks to climate change. They also show that drought-induced plasticity in root and shoot traits does not automatically translate into equivalent changes in litter decomposability.

Climate change currently manifests in upward and northward shifting treelines, which encompasses changes to the carbon (C) and nitrogen (N) composition of organic inputs to soils. Whether these changed inputs will increase or decrease microbial mineralisation of native soil organic matter remains unknown, making it difficult to estimate how treeline shifts will affect the C balance. Aiming to improve mechanistic understanding of C cycling in regions experiencing treeline shifts, we quantified priming effects in soils of high altitudes (Peruvian Andes) and high latitudes (subarctic Sweden), differentiating landcover types (boreal forest, tropical forest, tundra heath, Puna grassland) and soil horizons (organic, mineral). In a controlled laboratory incubation, soils were amended with substrates of different C:N, composed of an organic C source at a constant ratio of 30% substrate-C to microbial biomass C, combined with different levels of a nutrient solution neutral in pH. Substrate additions elicited both positive and negative priming effects in both ecosystems, independent from substrate C:N. Positive priming prevailed above the treeline in high altitudes and in mineral soils in high latitudes, where consequently climate change-induced treeline shifts and deeper rooting plants may enhance SOM-mineralisation and soil C emissions. However, such C loss may be compensated by negative priming, which dominated in the other soil types and was of larger magnitude than positive priming. In line with other studies, these results indicate a consistent mechanism linking decreased SOM-mineralisation (negative priming) to increased microbial substrate utilisation, suggesting preferential substrate use as a potential tool to support soil C storage. Graphical abstract

Nitrous oxide (N2O) is a potent greenhouse gas (GHG) with a global warming potential 265 times that of carbon dioxide (CO2) over 100 years. Contributing approximately 70% of global anthropogenic N2O emissions, agriculture represents the largest area of uncertainty for GHG reporting and the most challenging sector for emissions reduction: global N2O emissions are increasing at double the rate estimated by the Intergovernmental Panel on Climate Change (IPCC). The largest source of agricultural N2O emissions is from application of inorganic-N fertilisers, the manufacture of which produces more than 1% of global CO2 emissions and consumes 1% of global energy output.However, typical crop N uptake efficiency (NupE) means approximately half the fertiliser doesn’t reach the target plant, causing further ecological problems, such as biodiversity loss from eutrophication and atmospheric deposition. The extent to which microbial immobilisation of fertiliser N contributes to the NupE value of ca. 60% is currently unknown. If N immobilisation is found to be a large contributor to reducing N available to crops, this offers new opportunities to better manage fertiliser N inputs. Critically, with a growing global population, it is vital that we can increase food crop yields, and more efficient use of water and nutrients could help close the 70% ‘yield gap’ between potential and actual crop yields. Finally, inorganic N is the largest single cost in gross margins for wheat production and prices are rising. Increased NupE therefore represents a key opportunity for farmers to increase their financial sustainability. We hypothesised that under the conventional management of three applications of inorganic N in the spring, crops do not have the ability to outcompete the fast-growing soil microbial community for N, and that by supplying N to the crop in a ‘little and often’ approach, we could increase NupE by reducing immobilisation, and consequentially reduce N2O emissions. We conducted a field study of a winter wheat crop on a northern UK farm to investigate this, which compared conventional N fertiliser management (220 kg N ha-1 over three applications) of ammonium nitrate, to a little and often approach (220 kg N ha-1 over six applications) and an untreated (0 kg N ha-1) control. We followed the crop until harvest, and continuously measured N2O emissions and net ecosystem exchange of CO2 using a skyline2D automated flux system and also measured C and N pools in soil, plants and microbial biomass to assess changes in N uptake and allocation.We will present data which shows the outcome of plant-microbe competition for N in our agricultural system, and discuss the implications of different N fertiliser management for yield, profitability and GHG mitigation.

1. Microbial necromass is a large, dynamic and persistent component of soil organic carbon, the dominant terrestrial carbon pool. Quantification of necromass carbon stocks and its susceptibility to global change is becoming standard practice in soil carbon research. However, the typical proxies used for necromass carbon do not reveal the dynamic nature of necromass carbon flows and transformations within soil that ultimately determine necromass persistence. In this review, we define and deconstruct four stages of the necromass continuum: production, recycling, stabilization and destabilization. 2. Current understanding of necromass dynamics is described for each continuum stage. We highlight recent advances, methodological limitations and knowledge gaps which need to be addressed to determine necromass pool sizes and transformations. We discuss the dominant controls on necromass process rates and aspects of soil microscale structure including biofilms and food web interactions. The relative importance of each stage of the continuum is then compared in contrasting ecosystems and for climate change drivers. 3. From the perspective of the continuum, we draw three conclusions to inform future research. First, controls on necromass persistence are more clearly defined when viewed through the lens of the continuum; second, destabilization is the least understood stage of the continuum with recycling also poorly evidenced outside of a few ecosystems; and third, the response of necromass process rates to climate change is unresolved for most continuum stages and ecosystems. 4. Future mechanistic research focused on the role of biotic and abiotic soil microscale structure in determining necromass process rates and the relative importance of organo–mineral and organo–organo interactions can inform necromass persistence in different climate change scenarios. Our review demonstrates that deconstructing the necromass continuum is key to predicting the vulnerability and persistence of necromass carbon in a changing world.

Nitrous oxide (N2O) is a potent greenhouse gas (GHG) with a global warming potential 298 times that of carbon dioxide (CO2). Measurements of soil N2O emissions typically use manual chambers, with samples taken at low temporal resolution over long durations (months), or at higher temporal resolution (multiple samples per day) over short durations. Automated GHG flux systems have allowed the measurement of high frequency (sub-daily) N2O fluxes over longer periods (weeks to months), revealing that emissions can vary diurnally by up to 400% in agricultural soils.Contributing approximately 70% of global anthropogenic N2O emissions, agriculture represents the largest area of uncertainty for GHG reporting and the most challenging sector for emissions reduction: global N2O emissions are increasing at double the rate estimated by the Intergovernmental Panel on Climate Change (IPCC). Improvements to agricultural GHG emission estimates have increased the accuracy of GHG reporting, but N2O emissions from agricultural soils still contribute 25% of the uncertainty of total GHG emissions across all sectors. Our project, diurnal variation in soil nitrous oxide emissions (DIVINE), combines field and laboratory experiments that exploit high-resolution, robotic and continuous N2O measurement technology, to investigate the drivers and mechanisms underpinning diurnal variation in N2O.We will present work from a field study investigating the effect of soil properties and nitrogen (N) fertiliser management on diurnal variation in N2O emissions from a wheat crop. We assess how N fertiliser application (rate and frequency) and soil gas diffusivity (determined by bulk density and rain events), affect the depth of N2O production and N2O transport in the soil, and resultant impacts on the peak timing and amplitude of diurnal N2O emissions across the crop life cycle and seasons.N2O emissions will be compared in paired transects with contrasting bulk density but similar soil texture and history, with three ammonium nitrate fertiliser scenarios. N2O is being measured continuously using SkyLine2D automated flux chamber technology. To resolve depth/gas transfer coefficients after N fertiliser and rain events, we will measure soil N2O concentration profiles across the rooting zone in discrete campaigns during the crop life cycle.Further, we will discuss how our data will be used to improve the accuracy of N2O emission factors by accounting for environmental and diurnal variation. Bayesian statistical modelling will be used to represent the spatial and temporal distribution of emissions following fertilisation, and the effects of known environmental factors (e.g. temperature, soil moisture, light intensity), as well as the residual effect explicable by the diurnal cycle.

Greenhouse gas (GHG) fluxes from grasslands are affected by climate warming and agricultural management practices including nitrogen (N) fertiliser application and grazing. However, the interactive effects of these factors are poorly resolved in field studies. We used a factorial in situ experiment - combining warming, N-fertiliser and above-ground cutting treatments - to explore their individual and interactive effects on plant-soil properties and GHG fluxes in a temperate UK grassland over two years. Our results showed no interactive treatment effects on plant productivity despite individual effects of N-fertiliser and warming on above- and below-ground biomass. There were, however, interactive treatment effects on GHG fluxes that varied across the two years. In year 1, warming and N-fertiliser increased CO2 and reduced N2O fluxes. N-fertilised also interacted with above-ground biomass (AGB) removal increasing N2O fluxes in year one and reducing CO2 fluxes in year two. The grassland was consistently a sink of CH4; N-fertilised increased the sink by 45% (year 1), AGB removal and warming reduced CH4 consumption by 44% and 43%, respectively (year 2). The majority of the variance in CO2 fluxes was explained by above-ground metrics (grassland productivity and leaf dry matter content), with microclimate (air and soil temperature and soil moisture) and below-ground (root N content) metrics also significant. Soil chemistry (soil mineral N and net mineralisation rate), below-ground (specific root length) and microclimate (soil moisture) metrics explained 49% and 24% of the variance in N2O and CH4 fluxes, respectively. Overall, our work demonstrates the importance of interactions between climate and management as determinants of short-term grassland GHG fluxes. These results show that reduced cutting combined with lower inorganic N-fertilisers would constrain grassland C and N cycling and GHG fluxes in warmer climatic conditions. This has implications for strategic grassland management decisions to mitigate GHG fluxes in a warming world.

Tropical soils contain huge carbon stocks, which climate warming is projected to reduce by stimulating organic matter decomposition, creating a positive feedback that will promote further warming. Models predict that the loss of carbon from warming soils will be mediated by microbial physiology, but no empirical data are available on the response of soil carbon and microbial physiology to warming in tropical forests, which dominate the terrestrial carbon cycle. Here we show that warming caused a considerable loss of soil carbon that was enhanced by associated changes in microbial physiology. By translocating soils across a 3000 m elevation gradient in tropical forest, equivalent to a temperature change of ± 15 °C, we found that soil carbon declined over 5 years by 4% in response to each 1 °C increase in temperature. The total loss of carbon was related to its original quantity and lability, and was enhanced by changes in microbial physiology including increased microbial carbon‐use‐efficiency, shifts in community composition towards microbial taxa associated with warmer temperatures, and increased activity of hydrolytic enzymes. These findings suggest that microbial feedbacks will cause considerable loss of carbon from tropical forest soils in response to predicted climatic warming this century.

A global, unified dataset on Soil Organic Carbon (SOC) changes under perennial crops has not existed till now. We present a global, harmonised database on SOC change resulting from perennial crop cultivation. It contains information about 1605 paired-comparison empirical values (some of which are aggregated data) from 180 different peer-reviewed studies, 709 sites, on 58 different perennial crop types, from 32 countries in temperate, tropical and boreal areas; including species used for food, bioenergy and bio-products. The database also contains information on climate, soil characteristics, management and topography. This is the first such global compilation and will act as a baseline for SOC changes in perennial crops. It will be key to supporting global modelling of land use and carbon cycle feedbacks, and supporting agricultural policy development., Design Type(s)data integration objective • data collection and processing objective • factorial designMeasurement Type(s)amount of carbon atom in soilTechnology Type(s)digital curationFactor Type(s)climate • Species • experimental condition • ageSample Characteristic(s)Brazil • cultivated environment • Canada • United States of America • New Zealand • Italy • Germany • Cameroon • India • Sri Lanka • Venezuela • Kingdom of Denmark • Republic of Ireland • French Republic • United Kingdom • Kingdom of Spain • Costa Rica • Ethiopia • Ghana • Indonesia • Mexico • Nigeria • Republic of South Africa • Portuguese Republic • China • Malaysia • Turkey • Israel • Sweden • italy • Georgia • Puerto Rico • Tanzania • Australia Machine-accessible metadata file describing the reported data (ISA-Tab format)

Diurnal variations in soil nitrous oxide (N­2O) emissions have been documented for nearly four decades yet consensus on their significance is still lacking. Resolving this question is important as soil N2O emissions have some of the highest uncertainties in national greenhouse gas inventories. A major challenge for understanding diurnal variation is that conventional measurements rarely operate at temporal frequencies that can observe and report this phenomenon. Some higher frequency studies have observed daytime peaking of soil N­2O emissions and often ascribe it to the diurnal oscillation of soil temperature. However, night-time peaking and irregular diurnal N­2O patterns have also been reported in a number of studies.To investigate the prevalence and characteristics of diurnal N­2O variability, we systematically reviewed published studies that measured N2O at high temporal frequencies (≥ 5 times/day). We identified 46 published studies covering cropland, grassland and forest soils; and extracted sub-daily N­2O flux data and other soil parameters, yielding 286 individual days of data. Diurnal variability of N­2O emissions were found in ~80% of the data, with ~60% peaking during the day and ~20% at night. Diurnal N­2O patterns were associated with non-diurnal factors including soil texture and land use but the relationship between soil temperature and N­2O flux was inconsistent, with strong positive correlations (R > 0.7) only found in one-third of the datasets.This talk explores the implications of the review results on the time of sampling using conventional approaches (single time-point flux measurements), and the potential drivers of diurnal N­2O variations for future research. In addition, this talk will also introduce a novel automated measurement technique allowing flux measurements at high temporal resolutions and how its application could enable experimental investigations of potential drivers of diurnal N­2O variability.

The sensitivity of peatland carbon (C) fluxes to changes in climate and hydrology are uncertain due to the complex interactions between plants and peat properties. In this study we examine how peat cores taken from under three plant functional types (PFT) (bryophyte, graminoid and ericoid) differ in their biotic and abiotic properties and how this indirectly modulates the response of C fluxes to environmental change. Peat cores taken from under three PFTs had their aboveground vegetation removed to exclude direct plant-mediated effects, and were incubated in a temperature x water table factorial experiment at 12, 14 and 16 degrees C (air temperature) with the water table level -25, -15 or -5 cm below the peat surface. Carbon dioxide (CO2) and methane (CH4) fluxes were measured over 11 months. Emissions of CO(2)and CH(4)increased with temperature, with strong positive (CH4) and negative (CO2) interactions with increasing water table level. There were significant effects of removed PFT on the environmental sensitivity of CH4, but not CO(2)fluxes. CH(4)emissions were greatest in peat with graminoid PFT removed at the warmest temperature but these indirect effects were not explained by peat abiotic or biotic properties, which did not differ between PFTs. These results show that climate change-induced expansion of graminoids in northern peatlands will have direct and indirect effects on C fluxes and the stability of peatland C stores. These responses will be determined by the interactive effects of vegetation composition, hydrology and warming on methane-cycling microbial communities. Highlights Peatland carbon flux strength under a changing climate is influenced by PFT. Peat from under graminoid PFT emits more methane than peat from under bryophyte or ericoid PFT. Prior PFT cover influenced methane emissions, but did not affect peat abiotic or biotic properties. Increases in graminoid cover with climate change could indirectly increase peatland methane fluxes.

Manual measurements of nitrous oxide (N2O) emissions with static chambers are 2Department of Environment and Geography, University of York, Heslington, commonly practised. However, they generally do not consider the diurnal variability of N2O flux, and little is known about the patterns and drivers of such variability. We systematically reviewed and analysed 286 diurnal data sets of N2O fluxes from pub- lished literature to (i) assess the prevalence and timing (day or night peaking) of diurnal N2O flux patterns in agricultural and forest soils, (ii) examine the relationship between N2O flux and soil temperature with different diurnal patterns, (iii) identify whether non-diurnal factors (i.e. land management and soil properties) influence the occur- rence of diurnal patterns and (iv) evaluate the accuracy of estimating cumulative N2O emissions with single-daily flux measurements. Our synthesis demonstrates that diur- nal N2O flux variability is a widespread phenomenon in agricultural and forest soils. Of the 286 data sets analysed, ~80% exhibited diurnal N2O patterns, with ~60% peak- ing during the day and ~20% at night. Contrary to many published observations, our analysis only found strong positive correlations (R > 0.7) between N2O flux and soil temperature in one-third of the data sets. Soil drainage property, soil water-filled pore space (WFPS) level and land use were also found to potentially influence the occur- rence of certain diurnal patterns. Our work demonstrated that single-daily flux meas- urements at mid-morning yielded daily emission estimates with the smallest average bias compared to measurements made at other times of day, however, it could still lead to significant over- or underestimation due to inconsistent diurnal N2O patterns. This inconsistency also reflects the inaccuracy of using soil temperature to predict the time of daily average N2O flux. Future research should investigate the relationship between N2O flux and other diurnal parameters, such as photosynthetically active radiation (PAR) and root exudation, along with the consideration of the effects of soil moisture, drainage and land use on the diurnal patterns of N2O flux. The information could be incorporated in N2O emission prediction models to improve accuracy.

Microbial necromass dominates soil organic matter. Recent research on necromass and soil carbon storage has focused on necromass production and stabilization mechanisms but not15 on the mechanisms of necromass retention. We present evidence from soil incubations withstable-isotope labelled necromass that abiotic adsorption may be more important than biotic immobilization for short-term necromass retention. We demonstrate that necromass adsorbs not only to mineral surfaces, but may also interact with other necromass. Furthermore, necromass cell chemistry alters necromass-necromass interaction, with more bacterial tracer retained when there is yeast necromass present. These findings suggest that the adsorption and abiotic interaction of microbial necromass and its functional properties, beyond chemical stability, deserve further investigation in the context of soil carbon sequestration.

This study evaluates the dynamics of soil organic carbon (SOC) underperennial crops across the globe. It quantifies the effect of change fromannual to perennial crops and the subsequent temporal changes in SOCstocks during the perennial crop cycle. It also presents an empiricalmodel to estimate changes in the SOC content under crops as a functionof time, land use, and site characteristics. We used a harmonised globaldataset containing paired-comparison empirical values of SOC andincluding different types of perennial crops (perennial grasses, palms,and woody plants) with different end-uses: bioenergy, food, other bioproducts, and short rotation coppice crops. Salient outcomes include: a20-year period encompassing a change from annual to perennial cropsled to an average 20% increase in SOC at 0-30 cm (6.0 ± 4.6 Mg ha-1gain) and a total of 10% increase over the 0-100 cm soil profile (5.7 ±10.9 Mg ha-1). A change from natural pasture to perennial cropdecreased SOC stocks by 1% over 0-30 cm (-2.5 ± 4.2 Mg ha-1) and10% over 0-100 cm (-13.6 ± 8.9 Mg ha-1). The effect of a land usechange from forest to perennial crops did not have significant impacts,probably due to the limited number of plots; but the data indicated thatwhile a 2% increase in SOC was observed at 0-30 cm (16.81 ± 55.1 Mgha-1), a decrease of 24% was observed at 30-100 cm (-40.1 ± 16.8 Mgha-1); perennial crops generally accumulate SOC through time,especially woody crops; and temperature was the main driver explainingdifferences in SOC dynamics, followed by crop age, soil bulk density, claycontent and depth. We present empirical evidence showing that the FAOperennialization strategy is reasonable, underscoring the role ofperennial crops as a useful component of climate change mitigationstrategies.

BACKGROUND Responding effectively to climate change requires urgent action to halt net greenhouse gas (GHG) emissions and to adapt to changes that cannot be prevented. The Paris Agreement of the United Nations Framework Convention on Climate Change has committed governments to the following: keeping global temperature rise below 2°C, pursuing efforts to limit it to 1.5°C, and adapting to reduce the vulnerability of people and ecosystems to the damaging consequences of a changing climate. When protected, restored, or managed appropriately, natural and seminatural ecosystems make critical contributions to climate change mitigation and to helping people adapt to climate change. Ecosystems themselves are vulnerable to climate change, but by restoring natural ecosystem processes, resilience can be built, and a wide range of adaptation strategies can ameliorate the impacts. Both synergies and conflicts between different objectives can arise, and it is essential to have clarity about what constitutes success across the range of adaptation and mitigation outcomes and to track progress. The success of ecosystem-based mitigation can be measured in terms of falling net emissions and stabilization of atmospheric CO2 concentration. Although this is conceptually straightforward, it can be difficult to measure ecosystem fluxes accurately. Adaptation is more complicated because it encompasses a wide range of objectives, with respect to people and biodiversity, including both reducing vulnerability and managing unavoidable change. ADVANCES Many studies have investigated how nature-based solutions can contribute to climate change mitigation and adaptation. The evidence is now clear that protecting and restoring ecosystems is essential to holding global temperature rise to between 1.5° and 2°C. The value of different interventions for reducing GHG emissions and promoting carbon sequestration can be quantified with varying degrees of confidence. The evidence for the effectiveness, opportunities, and limitations of ecosystem-based adaptation in enabling people to cope with climate change is also growing, and these approaches are starting to be implemented. Adaptation to reduce the vulnerability of biodiversity and ecosystems themselves to climate change has been discussed over many years but proposed measures remain largely untested. This is starting to change, with recent studies gathering empirical evidence of the factors that influence the vulnerability of ecosystems and biodiversity. Nevertheless, evaluation and reporting of adaptation is currently focused on planning and implementation of actions rather than on assessment of whether these programs have successfully reduced vulnerability. OUTLOOK A picture is emerging of what successful adaptation and mitigation in terrestrial ecosystems looks like when it is built around protecting and restoring natural ecosystem processes. To realize the potential of ecosystems to ameliorate climate change requires integrated actions that are consistent with wider biodiversity and sustainable development goals. High-carbon ecosystems, particularly forests and peatlands, are essential, but other ecosystems, such as savannas, are also important elements of wider nature-based solutions and should be protected and restored. Pursuing mitigation objectives alone risks perverse outcomes that increase rather than reduce vulnerability. Further work is required to test the effectiveness of specific ecosystem-based mitigation and adaptation measures and what works best to support biodiversity in a changing climate. More-robust monitoring and evaluation are needed to drive progress. Measuring adaptation for biodiversity is particularly challenging, and monitoring and management will need to develop together as we learn from experience.

Soil organic matter (SOM) is an indicator of sustainable land management as stated in the global indicator framework of the United Nations Sustainable Development Goals (SDG Indicator 15.3.1). Improved forecasting of future changes in SOM is needed to support the development of more sustainable land management under a changing climate. Current models fail to reproduce historical trends in SOM both within and during transition between ecosystems. More realistic spatio-temporal SOM dynamics require inclusion of the recent paradigm shift from SOM recalcitrance as an 'intrinsic property' to SOM persistence as an 'ecosystem interaction'. We present a soil profile, or pedon-explicit, ecosystem-scale framework for data and models of SOM distribution and dynamics which can better represent land use transitions. Ecosystem-scale drivers are integrated with pedon-scale processes in two zones of influence. In the upper vegetation zone, SOM is affected primarily by plant inputs (above- and belowground), climate, microbial activity and physical aggregation and is prone to destabilization. In the lower mineral matrix zone, SOM inputs from the vegetation zone are controlled primarily by mineral phase and chemical interactions, resulting in more favourable conditions for SOM persistence. Vegetation zone boundary conditions vary spatially at landscape scales (vegetation cover) and temporally at decadal scales (climate). Mineral matrix zone boundary conditions vary spatially at landscape scales (geology, topography) but change only slowly. The thicknesses of the two zones and their transport connectivity are dynamic and affected by plant cover, land use practices, climate and feedbacks from current SOM stock in each layer. Using this framework, we identify several areas where greater knowledge is needed to advance the emerging paradigm of SOM dynamics-improved representation of plant-derived carbon inputs, contributions of soil biota to SOM storage and effect of dynamic soil structure on SOM storage-and how this can be combined with robust and efficient soil monitoring.

Biochar has the potential to increase crop yields on degraded, tropical soils. It can be readily produced in rural community settings using low-cost technology and is most economically feasible if produced from local biomass or waste residues. Biochar was produced from Leucaena biomass using low-cost pyrolysis and sequential pot experiments were then conducted in Malaysia on three degraded soils. We first evaluated the effect of Leucaena biochar on yields of Amaranthus, a leafy vegetable crop and measured changes to soil pH and nutrient availability over two growth cycles. We then tested whether any yield response to biochar was dependent upon the rate of biochar or fertilizer application. We found that biochar application at 30 t ha−1 with maximal fertilizer increased yields between 17 and 53% on very strongly acidic soil. Biochar added at 15 t ha−1 with maximal fertilizer increased yield by 54% on strongly acidic soil whilst there was no significant yield response on fertilized, slightly acidic soil. Unfertilized biochar treatments showed small yield responses across all soils over 2 growth cycles (9–11%), but yields were much lower than in fertilized treatments. Biochar also decreased short-term N availability when applied with fertilizers, which may improve nitrogen retention and substantially increased soil pH. This may reduce mobility of Fe, Mn and Al ions, which were negatively associated with yield. Our results suggest that Leucaena biochar can elicit a positive crop yield response but only when combined with fertilizer additions on very strongly to strongly acidic tropical soils.

1. Evidence suggests that the restoration of plant diversity in grasslands not only brings benefits for biodiversity conservation, but also the delivery of ecosystem services. While biodiversity- function experiments show that greater plant diversity increases resistance of plant productivity to climate extremes, it is not known whether real-world management options for grassland restoration likewise stabilise ecosystem responses to extreme climate events.2. We used a long-term (23 year) field experiment in northern England to test the hypothesis that management aimed at biodiversity restoration increases the resistance and recovery of ecosystem carbon (C) fluxes to short-term summer drought. This was tested by measuring plant, soil and microbial responses to a simulated drought in experimental grassland plots where fertiliser application and seed addition have been managed to enhance plant species diversity.3. The cessation of fertiliser application brought about small increases in plant species richness. Additionally, cessation of fertiliser application reduced overall plant productivity and promoted hemi-parasitic plants at the expense of grasses and forbs.4. Resistance of CO2 fluxes to drought, measured as ecosystem respiration, was greater in non-fertilised plots, as lower plant biomass reduced water demand, likely aided by proportionally more hemi-parasitic plants further reducing plant biomass. Additionally, legumes increased under drought thereby contributing to overall resistance of plant productivity.5. Recovery of soil microbial C and nitrogen was more rapid after rewetting than soil microbial community composition, irrespective of restoration treatment, suggesting high resilience of soil microbial communities to drought.6. Synthesis and applications. This study shows that while grassland diversity restoration management increases the resistance of C fluxes to drought, it also reduces agricultural yields, revealing a trade-off for land managers. Furthermore legumes, promoted through long-term restoration treatments, can help to maintain plant community productivity under drought by increasing their biomass. As such, grassland management strategies not only have consequences for ecosystem processes, but also the capacity to withstand extreme weather events.

More than 200 years ago, Alexander von Humboldt reported that tropical plant species richness decreased with increasing elevation and decreasing temperature. Surprisingly, coordinated patterns in plant, bacterial, and fungal diversity on tropical mountains have not yet been observed, despite the central role of soil microorganisms in terrestrial biogeochemistry and ecology. We studied an Andean transect traversing 3.5 km in elevation to test whether the species diversity and composition of tropical forest plants, soil bacteria, and fungi follow similar biogeographical patterns with shared environmental drivers. We found coordinated changes with elevation in all three groups: species richness declined as elevation increased, and the compositional dissimilarity among communities increased with increased separation in elevation, although changes in plant diversity were larger than in bacteria and fungi. Temperature was the dominant driver of these diversity gradients, with weak influences of edaphic properties, including soil pH. The gradients in microbial diversity were strongly correlated with the activities of enzymes involved in organic matter cycling, and were accompanied by a transition in microbial traits towards slower‐growing, oligotrophic taxa at higher elevations. We provide the first evidence of coordinated temperature‐driven patterns in the diversity and distribution of three major biotic groups in tropical ecosystems: soil bacteria, fungi, and plants. These findings suggest that interrelated and fundamental patterns of plant and microbial communities with shared environmental drivers occur across landscape scales. These patterns are revealed where soil pH is relatively constant, and have implications for tropical forest communities under future climate change.

Decarbonization of the world's energy supply is essential to meet the targets of the 2016 Paris climate change agreement. One promising opportunity is the utilization of second generation, low input bioenergy crops such as Miscanthus and Short Rotation Coppice (SRC) willow. Research has previously been carried out on the greenhouse gas (GHG) balance of growing these feedstocks and land‐use changes involved in converting conventional cropland to their production; however, there is almost no body of work understanding the costs associated with their end of life transitions back to conventional crops. It is likely that it is during crop interventions and land‐use transitions that significant GHG fluxes might occur. Therefore, in this study, we investigated soil GHG fluxes over 82 weeks during transition from Miscanthus and SRC willow into perennial ryegrass in west Wales, UK. This study captured soil GHG fluxes at a weekly time step, alongside monthly changes in soil nitrogen and labile carbon and reports the results of regression modelling of suspected drivers. Methane fluxes were typically trivial; however, nitrous oxide (N2O) fluxes were notably affected, reverted plots produced significantly more N2O than retained controls and Miscanthus produced significantly higher fluxes overall than willow plots. N2O costs of reversion appeared to be contained within the first year of reversion when the Miscanthus plots produced an average pregrass flux of 0.13 mg N2O m−2 hr−1 while for willow, this was 0.03 mg N2O m−2 hr−1. Total N2O emission from reversion increased the carbon cost over the lifetime of the Miscanthus from 6.50 to 9.91 Mg CO2 eq. ha−1 while for the willow, this increase was from 9.61 to 10.42 Mg CO2 eq. ha−1. Despite these significant increases, the carbon cost of energy contained in these perennial crops remained far lower than the equivalent carbon cost of energy in coal., There are likely to be greenhouse gas peak “hotspots” during land‐use change and agronomic interventions. This study investigated soil N2O flux at the end of crop life for two energy crops, Miscanthus and willow, during land‐use reversion to grassland (the previous land‐use). This is the first time in the literature that side‐by‐side energy crops and reversion systems have been compared and followed at a weekly resolution over 2 years. Mean and peak fluxes are quantified along with an indication of the time taken for these increased levels of emissions to return to a reasonable ambient for that particular land‐use.

The temperature sensitivity of soil organic matter (SOM) decomposition in tropical forests will influence future climate. Studies of a 3.5-kilometer elevation gradient in the Peruvian Andes, including short-term translocation experiments and the examination of the long-term adaptation of biota to local thermal and edaphic conditions, have revealed several factors that may regulate this sensitivity. Collectively this work suggests that, in the absence of a moisture constraint, the temperature sensitivity of decomposition is regulated by the chemical composition of plant debris (litter) and both the physical and chemical composition of preexisting SOM: higher temperature sensitivities are found in litter or SOM that is more chemically complex and in SOM that is less occluded within aggregates. In addition, the temperature sensitivity of SOM in tropical montane forests may be larger than previously recognized because of the presence of “cold-adapted” and nitrogen-limited microbial decomposers and the possible future alterations in plant and microbial communities associated with warming. Studies along elevation transects, such as those reviewed here, can reveal factors that will regulate the temperature sensitivity of SOM. They can also complement and guide in situ soil-warming experiments, which will be needed to understand how this vulnerability to temperature may be mediated by altered plant productivity under future climatic change.

Perennial bioenergy crops have significant potential to reduce greenhouse gas (GHG) emissions and contribute to climate change mitigation by substituting for fossil fuels; yet delivering significant GHG savings will require substantial land-use change, globally. Over the last decade, research has delivered improved understanding of the environmental benefits and risks of this transition to perennial bioenergy crops, addressing concerns that the impacts of land conversion to perennial bioenergy crops could result in increased rather than decreased GHG emissions. For policymakers to assess the most cost-effective and sustainable options for deployment and climate change mitigation, synthesis of these studies is needed to support evidence-based decision making. In 2015, a workshop was convened with researchers, policymakers and industry/business representatives from the UK, EU and internationally. Outcomes from global research on bioenergy land-use change were compared to identify areas of consensus, key uncertainties, and research priorities. Here, we discuss the strength of evidence for and against six consensus statements summarising the effects of land-use change to perennial bioenergy crops on the cycling of carbon, nitrogen and water, in the context of the whole life-cycle of bioenergy production. Our analysis suggests that the direct impacts of dedicated perennial bioenergy crops on soil carbon and nitrous oxide are increasingly well understood and are often consistent with significant life cycle GHG mitigation from bioenergy relative to conventional energy sources. We conclude that the GHG balance of perennial bioenergy crop cultivation will often be favourable, with maximum GHG savings achieved where crops are grown on soils with low carbon stocks and conservative nutrient application, accruing additional environmental benefits such as improved water quality. The analysis reported here demonstrates there is a mature and increasingly comprehensive evidence base on the environmental benefits and risks of bioenergy cultivation which can support the development of a sustainable bioenergy industry.

National governments and international organizations perceive bioenergy, from crops such as Miscanthus, to have an important role in mitigating greenhouse gas (GHG) emissions and combating climate change. In this research, we address three objectives aimed at reducing uncertainty regarding the climate change mitigation potential of commercial Miscanthus plantations in the United Kingdom: (i) to examine soil temperature and moisture as potential drivers of soil GHG emissions through four years of parallel measurements, (ii) to quantify carbon (C) dynamics associated with soil sequestration using regular measurements of topsoil (0–30 cm) C and the surface litter layer and (iii) to calculate a life cycle GHG budget using site-specific measurements, enabling the GHG intensity of Miscanthus used for electricity generation to be compared against coal and natural gas. Our results show that methane (CH4) and nitrous oxide (N2O) emissions contributed little to the overall GHG budget of Miscanthus, while soil respiration offset 30% of the crop's net aboveground C uptake. Temperature sensitivity of soil respiration was highest during crop growth and lowest during winter months. We observed no significant change in topsoil C or nitrogen stocks following 7 years of Miscanthus cultivation. The depth of litter did, however, increase significantly, stabilizing at approximately 7 tonnes dry biomass per hectare after 6 years. The cradle-to-farm gate GHG budget of this crop indicated a net removal of 24.5 t CO2-eq ha−1 yr−1 from the atmosphere despite no detectable C sequestration in soils. When scaled up to consider the full life cycle, Miscanthus fared very well in comparison with coal and natural gas, suggesting considerable CO2 offsetting per kWh generated. Although the comparison does not account for the land area requirements of the energy generated, Miscanthus used for electricity generation can make a significant contribution to climate change mitigation even when combusted in conventional steam turbine power plants.

Energy production from bioenergy crops may significantly reduce greenhouse gas (GHG) emissions through substitution of fossil fuels. Biochar amendment to soil may further decrease the net climate forcing of bioenergy crop production, however, this has not yet been assessed under field conditions. Significant suppression of soil nitrous oxide (N2O) and carbon dioxide (CO2) emissions following biochar amendment has been demonstrated in short-term laboratory incubations by a number of authors, yet evidence from long-term field trials has been contradictory. This study investigated whether biochar amendment could suppress soil GHG emissions under field and controlled conditions in a Miscanthus × Giganteus crop and whether suppression would be sustained during the first 2 years following amendment. In the field, biochar amendment suppressed soil CO2 emissions by 33% and annual net soil CO2 equivalent (eq.) emissions (CO2, N2O and methane, CH4) by 37% over 2 years. In the laboratory, under controlled temperature and equalised gravimetric water content, biochar amendment suppressed soil CO2 emissions by 53% and net soil CO2 eq. emissions by 55%. Soil N2O emissions were not significantly suppressed with biochar amendment, although they were generally low. Soil CH4 fluxes were below minimum detectable limits in both experiments. These findings demonstrate that biochar amendment has the potential to suppress net soil CO2 eq. emissions in bioenergy crop systems for up to 2 years after addition, primarily through reduced CO2 emissions. Suppression of soil CO2 emissions may be due to a combined effect of reduced enzymatic activity, the increased carbon-use efficiency from the co-location of soil microbes, soil organic matter and nutrients and the precipitation of CO2 onto the biochar surface. We conclude that hardwood biochar has the potential to improve the GHG balance of bioenergy crops through reductions in net soil CO2 eq. emissions.

Biochar application to soil has significant potential as a climate change mitigation strategy, due to its recalcitrant C content and observed effect to suppress soil greenhouse gas emissions such as nitrous oxide (N2O). Increased soil aeration following biochar amendment may contribute to this suppression. Soil cores from a Miscanthus X. giganteus plantation were amended with hardwood biochar at a rate of 2% dry soil weight (22 t ha−1). The cores were incubated at three different temperatures (4, 10 and 16 °C) for 126 days, maintained field moist and half subjected to periodic wetting events. Cumulative N2O production was consistently suppressed by at least 49% with biochar amendment within 48 h of wetting at 10 and 16 °C. We concluded that hardwood biochar suppressed soil N2O emissions following wetting at a range of field-relevant temperatures over four months. We hypothesised that this was due to biochar increasing soil aeration at relatively high moisture contents by increasing the water holding capacity (WHC) of the soil; however, this hypothesis was rejected. We found that 5% and 10% biochar amendment increased soil WHC. Also, 10% biochar amendment decreased bulk density of the soil. Sealed incubations were performed with biochar added at 0–10 % of dry soil weight and wetted to a uniform 87% WHC (78% WFPS). Cumulative N2O production within 60 h of wetting was 19, 19, 73 and 98% lower than the biochar-free control in the 1, 2, 5 and 10% biochar treatments respectively. We conclude that high levels of biochar amendment may change soil physical properties, but that the enhancement of soil aeration by biochar incorporation makes only a minimal contribution to the suppression of N2O emissions from a sandy loam soil. We suggest that microbial or physical immobilisation of NO3− in soil following biochar addition may significantly contribute to the suppression of soil N2O emissions.

Energy from biomass is renewable and capable of providing heat, power or liquid fuels. Life cycle assessments of these renewable fuels have often shown positive energy balances and GHG savings, relative to fossil fuels. There are, however, large variations between studies and not all are positive, leading to recent reports questioning the long-term sustainability of bioenergy. Using a systematic review of life cycle assessments relevant to feedstocks grown in a temperate climate (three for heat and power and eight for liquid biofuels) we have defined these sources of variation, highlighting areas of uncertainty and priorities for future research. In addition, we have explored the challenges in comparing bioenergy and biofuels production chains and their fossil fuel equivalents and demonstrated how this can be done in a fair and consistent manner.

Historically. land use in Britain has been shaped by the environment's capacity to provide energy as well as food, water and shelter. Over the next decades, energy will again become a major driver in land cover change as we seek to capture the necessary energy to replace fossil fuels, reduce environmental damage and substitute for insecure supplies. Britain was one of the first places to exploit fossil fuels extensively. initially coal, and it has the potential to generate considerable amounts of renewable energy from tides, waves, the wind, biomass and sunlight. The UK Government's policy is to develop a suite of technologies that will provide a resilient supply without compromising its economy or its international commitments to environmental protection. This paper examines the three major terrestrial options for renewable energy and assesses each by successively filtering them for feasibility, achievability and practicality incorporating existing developments, designation and public opinion. Technology and opinion are dynamic, so the outputs need to be viewed as indicative of alternative scenarios rather than as fixed forecasts. Implications for changes in the energy supply infrastructure needed to match the new supply chains are highlighted. The demand for energy depends on the demographic profile (Population size, age distribution, lifestyle and expectations) and on economic activity. Here total demand is predicted using the UK Energy Research Centre's Energy 2050 model, which uses linear programming to balance economics and environmental capacity by major demand sectors in five-year time steps. The core model often generates challenging results. (C) 2009 Queen's Printer and Controller of HMSO

The introduction of Registration, Evaluation and Authorisation of Chemicals (REACH), requires companies to register and risk assess all substances produced or imported in volumes of >1 tonne per year. Extrapolation methods which use existing data for estimating the effects of chemicals are attractive to industry, and comparative data are therefore increasingly in demand. Data on natural toxic chemicals could be used for extrapolation methods such as read-across. To test this hypothesis, the toxicity of natural chemicals and their synthetic analogues were compared using standardised toxicity tests. Two chemical pairs: the napthoquinones, juglone (natural) and 1,4-naphthoquinone (synthetic); and anthraquinones, emodin (natural) and quinizarin (synthetic) were chosen, and their comparative effects on the survival and reproduction of collembolans, earthworms, enchytraeids and predatory mites were assessed. Differences in sensitivity between the species were observed with the predatory mite (Hypoaspis aculeifer) showing the least sensitivity. Within the chemical pairs, toxicity to lethal and sub-lethal endpoints was very similar for the four invertebrate species. The exception was earthworm reproduction, which showed differential sensitivity to the chemicals in both naphthoquinone and anthraquinone pairs. Differences in toxicity identified in the present study may be related to degree of exposure and/or subtle differences in the mode of toxic action for the chemicals and species tested. It may be possible to predict differences by identifying functional groups which infer increased or decreased toxicity in one or other chemical. The development of such techniques would enable the use of read-across from natural to synthetic chemicals for a wider group of compounds.

The aim of this study was to compare the monoterpene content and distribution in litters and roots of three conifer species: Picea abies (L) Karst, Picea sitchensis (Bong.) Carr. and Pinus sylvestris (L). We analysed the monoterpene content of green needles, needle litter, F (fermentation) layer material and roots collected from monoculture plots. The rate of loss of monoterpenes from freshly fallen litter in the field was also studied at two monthly intervals over 10 months, to assess the length of time that monoterpenes entering the litter layer remain. Monoterpene analysis was carried out by extracting homogenised samples in hexane and identifying and quantifying the resulting monoterpenes using gas chromatography with flame ionisation detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). Mean total monoterpene concentrations varied significantly between the three species examined (e.g. in freshly fallen litter 1531 +/- 96, 100 +/- 5 and 1175 +/- 122 mu g g(-1) d. wt for P. abies, P. sitchensis and P. sylvestris); each species had distinctive and consistent monoterpene profiles associated with each type of tissue, and total monoterpene concentrations in green needles varied between individual trees of the same species, particularly for P. sitchensis. A substantial proportion of the monoterpene content of green needles remained in the needles after litter fall for P. abies (42\%), P. sitchensis (11\%) and P. sylvestris (30\%). Although rates of monoterpene loss from needle litters varied initially (P sylvestris > P. abies > P. sitchensis), the majority of the monoterpene content was lost after 4-6 months. Maximum monoterpene emission rates from decaying litter were calculated of 39 (P abies), 1.7 (P. sitchensis) and 39 mu g m(-2) h(-1) (P. sylvestris). Monoterpene concentrations in F layer material were very low (

The fungal community in coniferous forest soils plays a pivotal role in ecosystem processes such as decomposition and carbon and nutrient cycling. Both saprotrophic (SP) and ectomycorrhizal (ECM) fungi occur throughout the upper soil horizons in coniferous forests and could therefore be exposed to high concentrations of monoterpenes occurring in the needle litter and roots of some tree species. Previous work has noted the differential effects of monoterpenes on the mycelial growth of a range of both SP and ECM fungi when grown in artificial nutrient media. This study used a novel experimental system to assess the effect of environmentally relevant concentrations of monoterpenes on the activity of ECM and SP fungi grown on more natural substrata. Exposure of the ECM fungus Paxillus involutus (Batsch) Fr. to vapours of either α-pinene or β-pinene resulted in a significantly greater proportion of root tips being colonised by the fungus when it was grown with seedlings of Picea abies (L.) Karst. Exposure to monoterpenes resulted in a significant decrease in respiration rate of two species of litter degrading SP fungi, Mycena galopus var. candida J. E. Lange and Collybia butyracea (Bull.) P. Kumm. There was no difference in response between the two SP species, despite the fact that previous tests in liquid nutrient media, with monoterpenes at higher concentrations, indicated that one species was sensitive and one was not. The high volatility and low solubility of monoterpenes in water make them challenging to work with. The experimental system developed here, although still artificial, provides a bridge between pure culture studies in defined media and all the complexities of forest soils in the field, by allowing the exposure of fungi to environmentally relevant monoterpene concentrations in more natural substrata.

The mycelia of saprotrophic (SP) and ectomycorrhizal (ECM) fungi occur throughout the upper soil horizons in coniferous forests and could therefore be exposed to high concentrations of monoterpenes occurring in the needle litter of some tree species. Monoterpenes are mycotoxic and could potentially affect fungi that are exposed to them in the litter layers. In order to investigate whether monoterpenes typical of coniferous litters could influence fungal communities, we analysed the monoterpene content of freshly fallen needles of Pinus sylvestris, Picea abies and Picea sitchensis. The most abundant monoterpenes were found to be α-pinene, β-pinene and 3-carene. We evaluated the effects of these three monoterpene vapours on the biomass production of 23 SP isolates and 16 ECM isolates. Overall, 75 % of ECM isolates and 26 % of SP isolates were significantly inhibited by at least one of the monoterpene treatments and both intra- and interspecific variations in response were observed. Monoterpene concentrations are highest in surface litters. The differential effects on fungal taxa may influence the spatial and temporal distribution of fungal community composition, indirectly affecting decomposition and nutrient cycling, the fundamental ecosystem processes in which fungi have a key role in coniferous forest soils.

Aboveground primary productivity is widely considered to be limited by phosphorus (P) availability in lowland tropical forests and by nitrogen (N) availability in montane tropical forests. However, the extent to which this paradigm applies to belowground processes remains unresolved. We measured indices of soil microbial nutrient status in lowland, sub-montane and montane tropical forests along a natural gradient spanning 3400 m in elevation in the Peruvian Andes. With increasing elevation there were marked increases in soil concentrations of total N, total P, and readily exchangeable P, but a decrease in N mineralization determined by in situ resin bags. Microbial carbon (C) and N increased with increasing elevation, but microbial C : N : P ratios were relatively constant, suggesting homeostasis. The activity of hydrolytic enzymes, which are rich in N, decreased with increasing elevation, while the ratio of enzymes involved in the acquisition of N and P increased with increasing elevation, further indicating an increase in the relative demand for N compared to P with increasing elevation. We conclude that soil microorganisms shift investment in nutrient acquisition from P to N between lowland and montane tropical forests, suggesting that different nutrients regulate soil microbial metabolism and the soil carbon balance in these ecosystems.

Nitrous oxide (N2O) from agricultural soil is a significant source of greenhouse gas emissions. Biochar amendment can contribute to climate change mitigation by suppressing emissions of N2O from soil, although the mechanisms underlying this effect are poorly understood. We investigated the effect of biochar on soil N2O emissions and N cycling processes by quantifying soil N immobilisation, denitrification, nitrification and mineralisation rates using 15N pool dilution techniques and the FLUAZ numerical calculation model. We then examined whether biochar amendment affected N2O emissions and the availability and transformations of N in soils.Our results show that biochar suppressed cumulative soil N2O production by 91% in near-saturated, fertilised soils. Cumulative denitrification was reduced by 37%, which accounted for 85-95 % of soil N2O emissions. We also found that physical/chemical and biological ammonium (NH4 +) immobilisation increased with biochar amendment but that nitrate (NO3 -) immobilisation decreased. We concluded that this immobilisation was insignificant compared to total soil inorganic N content. In contrast, soil N mineralisation significantly increased by 269% and nitrification by 34% in biochar-amended soil.These findings demonstrate that biochar amendment did not limit inorganic N availability to nitrifiers and denitrifiers, therefore limitations in soil NH4 + and NO3 - supply cannot explain the suppression of N2O emissions. These results support the concept that biochar application to soil could significantly mitigate agricultural N2O emissions through altering N transformations, and underpin efforts to develop climate-friendly agricultural management techniques.

Climate change is affecting the amount and complexity of plant inputs to tropical forest soils. This is likely to influence the carbon (C) balance of these ecosystems by altering decomposition processes e.g., “positive priming effects” that accelerate soil organic matter mineralization. However, the mechanisms determining the magnitude of priming effects are poorly understood. We investigated potential mechanisms by adding 13C labeled substrates, as surrogates of plant inputs, to soils from an elevation gradient of tropical lowland and montane forests. We hypothesized that priming effects would increase with elevation due to increasing microbial nitrogen limitation, and that microbial community composition would strongly influence the magnitude of priming effects. Quantifying the sources of respired C (substrate or soil organic matter) in response to substrate addition revealed no consistent patterns in priming effects with elevation. Instead we found that substrate quality (complexity and nitrogen content) was the dominant factor controlling priming effects. For example a nitrogenous substrate induced a large increase in soil organic matter mineralization whilst a complex C substrate caused negligible change. Differences in the functional capacity of specific microbial groups, rather than microbial community composition per se, were responsible for these substrate-driven differences in priming effects. Our findings suggest that the microbial pathways by which plant inputs and soil organic matter are mineralized are determined primarily by the quality of plant inputs and the functional capacity of microbial taxa, rather than the abiotic properties of the soil. Changes in the complexity and stoichiometry of plant inputs to soil in response to climate change may therefore be important in regulating soil C dynamics in tropical forest soils. Refereed/Peer-reviewed

Global energy demand is increasing as greenhouse gas driven climate change progresses, making renewable energy sources critical to future sustainable power provision. Land-based wind and solar electricity generation technologies are rapidly expanding, yet our understanding of their operational effects on biological carbon cycling in hosting ecosystems is limited. Wind turbines and photovoltaic panels can significantly change local ground-level climate by a magnitude that could affect the fundamental plant-soil processes that govern carbon dynamics. We believe that understanding the possible effects of changes in ground-level microclimates on these phenomena is crucial to reducing uncertainty of the true renewable energy carbon cost and to maximise beneficial effects. In this Opinions article, we examine the potential for the microclimatic effects of these land-based renewable energy sources to alter plant-soil carbon cycling, hypothesise likely effects, and identify critical knowledge gaps for future carbon research.

SummaryWe report a family ascertained for molecular diagnosis of muscular dystrophy in a young girl, in which preferential activation (≥ 95% of cells) of the paternal X chromosome was seen in both the proband and her mother. To determine the molecular basis for skewed X inactivation, we studied X-inactivation patterns in peripheral blood and/or oral mucosal cells from 50 members of this family and from a cohort of normal females. We found excellent concordance between X-inactivation patterns in blood and oral mucosal cell nuclei in all females. Of the 50 female pedigree members studied, 16 showed preferential use (≥ 95% cells) of the paternal X chromosome; none of 62 randomly selected females showed similarly skewed X inactivation (P < .0003). The trait for skewed X inactivation was maternally inherited in this family. A linkage study using the molecular trait of skewed X inactivation as the scored pheno-type localized this trait to Xq28 (DXS1108; maximum LOD score [Zmax] = 4.34, recombination fraction [θ] = 0). Both genotyping of additional markers and FISH of a YAC probe in Xq28 showed a deletion spanning from intron 22 of the factor VIII gene to DXS115-3. This deletion completely cosegregated with the trait (Zmax = 6.92, θ = 0). Comparison of clinical findings between affected and unaffected females in the 50-member pedigree showed a statistically significant increase in spontaneous-abortion rate in the females carrying the trait (P < .02). To our knowledge, this is the first gene-mapping study of abnormalities of X-inactivation patterns and is the first association of a specific locus for recurrent spontaneous abortion in a cytogenetically normal family. The involvement of this locus in cell lethality, cell-growth disadvantage, developmental abnormalities, or the X-inactivation process is discussed.

1. The Andes are predicted to warm by 3–5 °C this century with the potential to alter the processes regulating carbon (C) cycling in these tropical forest soils. This rapid warming is expected to stimulate soil microbial respiration and change plant species distributions, thereby affecting the quantity and quality of C inputs to the soil and influencing the quantity of soil-derived CO2 released to the atmosphere. 2. We studied tropical lowland, premontane and montane forest soils taken from along a 3200-m elevation gradient located in south-east Andean Peru. We determined how soil microbial communities and abiotic soil properties differed with elevation. We then examined how these differences in microbial composition and soil abiotic properties affected soil C-cycling processes, by amending soils with C substrates varying in complexity and measuring soil heterotrophic respiration (RH). 3. Our results show that there were consistent patterns of change in soil biotic and abiotic properties with elevation. Microbial biomass and the abundance of fungi relative to bacteria increased significantly with elevation, and these differences in microbial community composition were strongly correlated with greater soil C content and C:N (nitrogen) ratios. We also found that RH increased with added C substrate quality and quantity and was positively related to microbial biomass and fungal abundance. 4. Statistical modelling revealed that RH responses to changing C inputs were best predicted by soil pH and microbial community composition, with the abundance of fungi relative to bacteria, and abundance of gram-positive relative to gram-negative bacteria explaining much of the model variance. 5. Synthesis. Our results show that the relative abundance of microbial functional groups is an important determinant of RH responses to changing C inputs along an extensive tropical elevation gradient in Andean Peru. Although we do not make an experimental test of the effects of climate change on soil, these results challenge the assumption that different soil microbial communities will be ‘functionally equivalent’ as climate change progresses, and they emphasize the need for better ecological metrics of soil microbial communities to help predict C cycle responses to climate change in tropical biomes.

Across the energy sector, alternatives to fossil fuels are being developed, in response to the dual drivers of climate change and energy security. For transport, biofuels have the greatest potential to replace fossil fuels in the short-to medium term. However, the ecological benefits of biofuels and the role that their deployment can play in mitigating climate change are being called into question. Life Cycle Assessment (LCA) is a widely used approach that enables the energy and greenhouse gas (GHG) balance of biofuel production to be calculated. Concerns have nevertheless been raised that published data show widely varying and sometimes contradictory results. This review describes a systematic review of GHG emissions and energy balance data from 44 LCA studies of first- and second-generation biofuels. The information collated was used to identify the dominant sources of GHG emissions and energy requirements in biofuel production and the key sources of variability in published LCA data. Our analysis revealed three distinct sources of variation: (1) 'real' variability in parameters e.g. cultivation; (2) 'methodological' variability due to the implementation of the LCA method; and (3) 'uncertainty' due to parameters rarely included and poorly quantified. There is global interest in developing a sustainability assessment protocol for biofuels. Confidence in the results of such an assessment can only be assured if these areas of uncertainty and variability are addressed. A more defined methodology is necessary in order to allow effective and accurate comparison of results. It is also essential that areas of uncertainty such as impacts on soil carbon stocks and fluxes are included in LCA assessments, and that further research is conducted to enable a robust calculation of impacts under different land-use change scenarios. Without the inclusion of these parameters, we cannot be certain that biofuels are really delivering GHG savings compared with fossil fuels.

Question: Can useful realised niche models be constructed for British plant species using climate, canopy height and mean Ellenberg indices as explanatory variables? Location: Great Britain. Methods: Generalised linear models were constructed using occurrence data covering all major natural and semi-natural vegetation types (n=40 683 quadrat samples). Paired species and soil records were only available for 4% of the training data (n=1033) so modelling was carried out in two stages. First, multiple regression was used to express mean Ellenberg values for moisture, pH and fertility, in terms of direct soil measurements. Next, species presence/absence was modelled using mean indicator scores, cover-weighted canopy height, three climate variables and interactions between these factors, but correcting for the presence of each target species in training plots to avoid circularity. Results: Eight hundred and three higher plants and 327 bryophytes were modelled. Thirteen per cent of the niche models for higher plants were tested against an independent survey dataset not used to build the models. Models performed better when predictions were based only on indices derived from the species composition of each plot rather than measured soil variables. This reflects the high variation in vegetation indices that was not explained by the measured soil variables. Conclusions: The models should be used to estimate expected habitat suitability rather than to predict species presence. Least uncertainty also attaches to their use as risk assessment and monitoring tools on nature reserves because they can be solved using mean environmental indicators calculated from the existing species composition, with or without climate data.