Elevated CO2 and Tree Species Affect Microbial Activity and Associated Aggregate Stability in Soil Amended with Litter

(1) Elevated atmospheric CO2 (eCO2) may affect organic inputs to woodland soils with potential consequences for C dynamics and associated aggregation; (2) The Bangor Free Air Concentration Enrichment experiment compared ambient (330 ppmv) and elevated (550 ppmv) CO2 regimes over four growing seasons (2005–2008) under Alnus glutinosa, Betula pendula and Fagus sylvatica. Litter from the experiment (autumn 2008) and Lumbricus terrestris were added to mesocosm soils. Microbial properties and aggregate stability were investigated in soil and earthworm casts. Soils taken from the field experiment in spring 2009 were also investigated; (3) eCO2 litter had lower N and higher C:N ratios. F. sylvatica and B. pendula litter had lower N and P than A. glutinosa; F. sylvatica had higher cellulose. In mesocosms, eCO2 litter decreased respiration, mineralization constant (respired C:total organic C) and soluble carbon in soil but not earthworm casts; microbial‐C and fungal hyphal length differed by species (A. glutinosa = B. pendula > F. sylvatica) not CO2 regime. eCO2 increased respiration in field aggregates but increased stability only under F. sylvatica; (4) Lower litter quality under eCO2 may restrict its initial decomposition, affecting C stabilization in aggregates. Later resistant materials may support microbial activity and increase aggregate stability. In woodland, C and soil aggregation dynamics may alter under eCO2, but outcomes may be influenced by tree species and earthworm activity

Plant community composition and an insect outbreak influence phenol oxidase activity and soil-litter biochemistry in a sub-Arctic birch-heath

Rates of decomposition in Arctic soils are regulated by temperature and moisture, but substrate availability is dictated by vegetation inputs, which are also subject to biotic influences. Here, we examine how leaf and litter inputs from individual dwarf shrub species influence soil enzyme activity in a sub-Arctic heath community in Abisko, Sweden. We further consider how foliar damage via insect herbivory (and outbreak) affects the soil community and decomposition. During the peak growing season (July 2011), we assessed how shrub community composition (Empetrum hermaphroditum, Vaccinium myrtillus, V. uliginosum and V. vitis-idaea) determined litter and soil phenol oxidase activity. A periodic severe outbreak of autumn moth larvae (Epirrita autumnata) affected this community in the following year (July 2012), and we used this to investigate its impact on relationships with phenol oxidase activity, soil respiration, soluble NH4 + and soluble phenolics; the soluble factors being directly associated with inputs from insect larval waste (frass). Pre-outbreak (2011), the strongest relationship observed was higher phenol oxidase activity with E. hermaphroditum cover. In the outbreak year (2012), phenol oxidase activity had the strongest relationship with damage to the deciduous species V. myrtillus, with greater herbivory lowering activity. For the other deciduous species, V. uliginosum, soil NH4 + and phenolics were negatively correlated with foliar larval damage. Phenol oxidase activity was not affected by herbivory of the evergreen species, but there was a strong positive relationship observed between E. hermaphroditum community abundance and soil respiration. We highlight the dominant role of E. hermaphroditum in such sub-Arctic shrub communities and show that even during insect outbreaks, it can dictate soil processes

Can the optimisation of pop-up agriculture in remote communities help feed the world?

Threats to global food security have generated the need for novel food production techniques to feed an ever-expanding population with ever-declining land resources. Hydroponic cultivation has been long recognised as a reliable, resilient and resource-use-efficient alternative to soil-based agricultural practices. The aspiration for highly efficient systems and even city-based vertical farms is starting to become realised using innovations such as aeroponics and LED lighting technology. However, the ultimate challenge for any crop production system is to be able to operate and help sustain human life in remote and extreme locations, including the polar regions on Earth, and in space. Here we explore past research and crop growth in such remote areas, and the scope to improve on the systems used in these areas to date. We introduce biointensive agricultural systems and 3D growing environments, intercropping in hydroponics and the production of multiple crops from single growth systems. To reflect the flexibility and adaptability of these approaches to different environments we have called this type of enclosed system ‘pop-up agriculture’. The vision here is built on sustainability, maximising yield from the smallest growing footprint, adopting the principles of a circular economy, using local resources and eliminating waste. We explore plant companions in intercropping systems to supply a diversity of plant foods. We argue that it is time to consume all edible components of plants grown, highlighting that nutritious plant parts are often wasted that could provide vitamins and antioxidants. Supporting human life via crop production in remote and isolated communities necessitates new levels of efficiency, eliminating waste, minimising environmental impacts and trying to wean away from our dependence on fossil fuels. This aligns well with tandem research emerging from economically developing countries where lower technology hydroponic approaches are being trialled reinforcing the need for ‘cross-pollination’ of ideas and research development on pop-up agriculture that will see benefits across a range of environments

Spatial co‐localisation of extreme weather events: a clear and present danger

Extreme weather events have become a dominant feature of the narrative surrounding changes in global climate with large impacts on ecosystem stability, functioning and resilience; however, understanding of their risk of co‐occurrence at the regional scale is lacking. Based on the UK Met Office’s long‐term temperature and rainfall records, we present the first evidence demonstrating significant increases in the magnitude, direction of change and spatial co‐localisation of extreme weather events since 1961. Combining this new understanding with land‐use data sets allowed us to assess the likely consequences on future agricultural production and conservation priority areas. All land‐uses are impacted by the increasing risk of at least one extreme event and conservation areas were identified as the hotspots of risk for the co‐occurrence of multiple event types. Our findings provide a basis to regionally guide land‐use optimisation, land management practices and regulatory actions preserving ecosystem services against multiple climate threats