The UK may be required to expand its bioenergy production in order to make a significant contribution towards the delivery of its 'net zero' greenhouse gas emissions target by 2050. However, some trees grown for bioenergy are emitters of volatile organic compounds (VOCs), including isoprene and terpenes, precursors in the formation of tropospheric ozone, an atmospheric pollutant, which require assessment to understand any consequent impacts on air quality. In this initial scoping study, VOC emission rates were quantified under UK climate conditions for the first time from four species of eucalypts suitable for growing as short-rotation forest for bioenergy. An additional previously characterised eucalypt species was included for comparison. Measurements were undertaken using a dynamic chamber sampling system on 2-3 year-old trees grown under ambient conditions. Average emission rates for isoprene, normalised to 30 °C and 1000 μmol m −2 s −1 PAR, ranged between 1.3 μg C g dw −1 h −1 to 10 μg C g dw −1 h −1 . All the eucalypt species measured were categorised as 'medium' isoprene emitters (1-10 μg C g dw −1 h −1 ). Total normalised monoterpene emission rates were of similar order of magnitude to isoprene or approximately one order of magnitude lower. The composition of the monoterpene emissions differed between the species and major compounds included eucalyptol, α-pinene, limonene and β-cisocimene. The emission rates presented here contribute the first data for further studies to quantify the potential impact on UK atmospheric composition, if there were widespread planting of eucalypts in the UK for bioenergy purposes.

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Soil emissions of NO and N2O from typical land uses across Lowland and Highland Scotland were simulated under climate change conditions, during a short-term laboratory study. All locations investigated were significant sources of N2O (range: 157–277 µg N2O–N m−2 h−1) and low-to-moderate sources of NO emissions (range: 0.4–30.5 µg NO–N m−2 h−1), with a general tendency to decrease with altitude and increase with fertiliser and atmospheric N inputs. Simulated climate warming and extreme events (drought, intensive rainfall) increased soil NO pulses and N2O emissions from both natural and managed ecosystems in the following order: natural Highlands < natural Lowlands < grazed grasslands < natural moorland receiving high NH3 deposition rates. Largest NO emission rates were observed from natural moorlands exposed to high NH3 deposition rates. Although soil NO emissions were much smaller (6–660 times) than those of N2O, their impact on air quality is likely to increase as combustion sources of NO x are declining as a result of successful mitigation. This study provides evidence of high N emission rates from natural ecosystems and calls for urgent action to improve existing national and intergovernmental inventories for NO and N2O, which at present do not fully account for emissions from natural soils receiving no direct anthropogenic N inputs.

GRAIN-SIZE ANALYSESSand-silt-clay distribution was determined on 10-cm 3 sediment samples collected at the time the cores were split and described. The results are listed in Table 1.The sediment classification used here is that of Shepard (1954), with the sand, silt, and clay boundaries based on the Wentworth (1922) scale (Fig. 1). Thus, the sand, silt, and clay fractions are composed of particles whose diameters range from 2000 to 62.5 µm, 62.5 to 3.91 µm, and less than 3.91 µm, respectively. This classification is applied regardless of sediment type and origin; therefore, the sediment names used in this table may differ from those used elsewhere in this volume, e.g., a silt composed of nannofossils in this table may be called a nannofossil ooze in a site-summary chapter.Standard sieve and pipette methods were used to determine the grain-size distribution. The sediment sample was dried and dispersed in a Calgon solution. If a sediment sample failed to disaggregate, it was treated with a sonic probe and, if necessary, hydrogen peroxide. Sediment samples which resisted this treatment were not analyzed.The sand fraction was removed by wet sieving, using a 63-µm sieve, and the silt and clay fractions were analyzed by standard pipette analysis. Sampling depths and times were calculated using equations derived from Stokes' settling-velocity equation (Krumbein and Pettijohn, 1938, pp. 95-96):where V = velocity, in cm/s t = time, in sec* D = depth pipette is inserted, in cm g = gravity, in cm/s 2 * r = radius of individual particles, in cm* d x = density of solid particles arbitrarily set at 2.675 g/cm 3 d 2 = absolute density of distilled water at different temperatures (Hodgman et al., 1960(Hodgman et al., , p. 2129

&lt;p&gt;Tropical oil palm (OP) plantations are major emitters of greenhouse gases (GHGs), but there are management options, which may reduce these emissions, including increasing understory biomass. Managing the vegetation within and around plantations could potentially minimise environmental damage and maximise co-benefits such as soil protection, pest control and diversity. Such practices include creating reserves, buffer strips and management of vegetation in the plantations themselves. The impact of these management practices is uncertain, and there is a real need for an evidence-base to guide improvements in the environmental sustainability of OP management.&lt;/p&gt;&lt;p&gt;The timing for research related to management options is critical for influencing current decision-making. In Indonesia, most OP plantations were established in the late 1980s and early 1990s and due to the 25 &amp;#8211; 30-year life cycle of OP plantations, nearly half are due to be clear-cut for replanting in the near-future. Hence, it is vital to understand replanting and restoration options which simultaneously allow for high productivity as well as supporting biodiversity and minimising GHG emissions.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;The scope and specific objectives of our study were:&lt;/p&gt;&lt;ul&gt;&lt;li&gt;1) To measure GHG emissions under different understory management techniques (with/without vegetation through use of herbicides).&lt;/li&gt; &lt;li&gt;2) To link GHG data to soil data to develop understanding of ecosystem function under different OP plantation management approaches.&lt;/li&gt; &lt;/ul&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;We will present monthly static chamber measurements of GHG emissions for the duration of one year starting October 2018, established on an existing long-term experiment investigating the impact of diversifying understory vegetation on biodiversity, ecosystem functioning and yield in Sumatra, Indonesia (The Biodiversity and Ecosystem Function in Tropical Agriculture Project (BEFTA)). The three different understory management treatments were:&lt;/p&gt;&lt;ul&gt;&lt;li&gt;1) Normal biodiversity complexity: standard industry practice, intermediate level of herbicide use in harvest circles.&lt;/li&gt; &lt;li&gt;2) Reduced biodiversity complexity: spraying/removing all understory vegetation with herbicides.&lt;/li&gt; &lt;li&gt;3) Enhanced biodiversity complexity: reduced-input management with no herbicide application and limited understory cutting.&lt;/li&gt; &lt;/ul&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;We measured the GHG fluxes of nitrous oxide (N&lt;sub&gt;2&lt;/sub&gt;O), methane (CH&lt;sub&gt;4&lt;/sub&gt;) and soil ecosystem respiration/carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;) using static chambers and analysis by gas chromatography (GC-&amp;#181;ECD/FID).&lt;/p&gt;&lt;p&gt;Preliminary results show little difference amongst the different understory treatments in terms of N&lt;sub&gt;2&lt;/sub&gt;O fluxes. Fluxes were generally low (0-0.1 &amp;#181;g m&lt;sup&gt;-2&lt;/sup&gt; h&lt;sup&gt;-1&lt;/sup&gt;) with high variability. However, there is a trend towards slightly higher emissions during the wetter months (Oct-Dec 2018) of up to 0.2 &amp;#181;g m&lt;sup&gt;-2&lt;/sup&gt; h&lt;sup&gt;-1&lt;/sup&gt;.&lt;/p&gt;&lt;p&gt;Methane (CH&lt;sub&gt;4&lt;/sub&gt;) fluxes were generally small and fluctuated around zero. During the wet months, (Oct to Dec 2018) small emission fluxes up to 3 &amp;#181;g m&lt;sup&gt;-2&lt;/sup&gt; h&lt;sup&gt;-1&lt;/sup&gt; were observed; whereas during the dry months uptake of methane, prevailed. No distinctive differences between the different treatments was observed.&lt;/p&gt;&lt;p&gt;Due to the age of the plantation and imminent replanting, none of the plots were being fertilised at the time of measurement &amp;#8211; greater differences between vegetation treatments may be observed under fertilisation.&lt;/p&gt;&lt;p&gt;In conclusion, initial results showed that the presence or absence of understorey did not increase soil emissions of N&lt;sub&gt;2&lt;/sub&gt;O and CH&lt;sub&gt;4&lt;/sub&gt;. This suggests that the within-crop ecological benefits do not result in an increased GHG burden.&lt;/p&gt;