Hedgerow agroforestry in England and Wales: increasing width to sequester additional carbon

Hedgerow systems are one of the more prominent agroforestry systems in temperate European agriculture, and the UK has the second largest extent of these in the European Union (Herzog 2000; den Herder et al. 2016). An estimated 456 000 km of hedge in England and Wales has been actively managed (Carey et al. 2008); which limits hedge outward growth, and maintains an effective barrier to livestock (Pollard et al. 1974). This management consists of a short period trimming cycle every 1 - 3 years, and a long period structural restoration cycle, after approximately 40 years growth (Staley et al. 2015). A mechanical flail is used for the short period trimming cycle by 92% of farmers in England and Wales (Britt et al. 2011). Typical ‘Enclosure’ hedges in England and Wales were planted with only hawthorn (Crataegus monogyna), in single, or double rows, from the 16th Century onwards (Maclean 2006). Hawthorn is still the dominant woody species, found within 90% of hedges in England and Wales, but a mix of woody species is common, and blackthorn (Prunus spinosa) is the second most frequent species, found within 50% of these hedges (Barr et al. 2000). The potential for temperate agroforestry to sequester carbon (C), and mitigate rising levels of Green-House Gasses (GHG), is beginning to receive more attention (Udawatta and Jose 2012). Axe et al. (2017) showed the potential to sequester C where wider managed hedges had greater C stocks (t C km-1 ). Allowing such hedges to grow wider from lateral branch growth only, without increasing planting density, may not be the most effective way to accumulate Above Ground Biomass (AGB) C. It also introduces uncertainty in using area C stock values (t C ha-1 ) to estimate AGB C (t C), as this parameter assumes a linear relationship with hedge width. Here new data on the contribution made by blackthorn to AGB C stock, and the correlation between hedge width and t C km-1 , from the pilot study of triennially flailed hedge biomass (Axe et al. 2017), along with supporting evidence on shrub growth in unmanaged hedges (Küppers 1985), is examined to advance how atmospheric C could be sequestered by increasing hedge width

Carbon storage in hedge biomass—A case study of actively managed hedges in England

Farmland hedges could be managed for carbon sequestration, but empirical data on their carbon (C) stock in the UK is lacking. Lowland hedges managed by hedge laying and triennial trimming using a mechanical flail formed a dense woody structure (mean 81,368 stems ha−1). Hedges untrimmed for 3 years (mean height 3.5 m, widths 2.6–4.2 m), contained an above ground biomass (AGB) C stock of 42.0 ± 3.78 t C ha−1 (14.0 ± 1.94 t C km−1); when trimmed to 2.7 m high, and subsequently 1.9 m high, AGB C stocks were reduced to 40.6 ± 4.47 t C ha−1 (11.4 t C km−1) and 32.2 ± 2.76 t C ha−1 (9.9 t C km−1), respectively. A 4.2 m wide hedge contained 9.7 t C km−1 more AGB C stock than a 2.6 m wide hedge (mean height 3.5 m). Below ground biomass (BGB) was 38.2 ± 3.66 t C ha−1 (11.5 t C km−1). Near horizontal stems, arranged by hedge laying, 12–18 years prior to sampling, accounted for 5.2 t C ha−1 (1.6 t C km−1) of AGB C. The empirical data demonstrated how changing management practices to wider/taller hedges sequestered C in AGB. These estimates of hedgerow C stocks fill a knowledge gap on C storage and identified the need for a more comprehensive biomass inventory of hedgerows to strengthen the national carbon accounting of agro-ecosystems in the UK

Failure mechanisms of graphene under tension

Recent experiments established pure graphene as the strongest material known to mankind, further invigorating the question of how graphene fails. Using density functional theory, we reveal the mechanisms of mechanical failure of pure graphene under a generic state of tension. One failure mechanism is a novel soft-mode phonon instability of the $K_1$-mode, whereby the graphene sheet undergoes a phase transition and is driven towards isolated benzene rings resulting in a reduction of strength. The other is the usual elastic instability corresponding to a maximum in the stress-strain curve. Our results indicate that finite wave vector soft modes can be the key factor in limiting the strength of monolayer materials

Gait, function and quadriceps strength after intraarticular hyaluronan injections in patients with symptomatic knee osteoarthritis

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn View/OpenIntroduction: Knee OA is a common cause of decline in function and is generally associated with joint malalignment and laxity, joint space narrowing, quadriceps weakness, as well as sclerosis and attrition of subchondral bone. Intraarticular (IA) injections of Hyaluronic Acid (HA) are indicated to palliate symptoms and improve function in patients with knee OA. Primary outcome measures in studies on the efficacy of this treatment are largely self reports of pain and function. The purpose of the study was to investigate the effects of HA injections on knee function and sagittal plane kinematics in patients with knee OA. Materials and Methods: Thirteen subjects with symptomatic knee OA and scheduled for 5, weekly, IA injections of HA were recruited. Each subject was tested for baseline data. Posttreatment testing sessions were conducted within 3 weeks of finishing the series of HA and again five months after treatment. Kinematic data were collected at 120 Hz using an eight camera motion analysis system (VICON, Oxford Metrics). Subjects walked along a 10 m walkway at self-selected pace. Ten walking trials were collected and averaged. Knee function was assessed with a knee specific questionnaire (Knee Outcome Survey (KOS)), goniometric range of motion (ROM) measures, a six minute walk (6MW) and a timed stair climbing task. Quadriceps strength was evaluated isometrically at 90° with a KinCom dynamometer (Chattanooga Group, Inc., Chattanooga, TN) and expressed as a ratio of the force output of the involved vs. uninvolved side (Quadriceps Index (QI)). Repeated measures analysis of variance (ANOVA) with pairwise comparisons, multivariate analysis, linear regression analysis and paired t-tests were used to analyze the data. Alpha was set at 0.05. Results: Multivariate analysis of knee flexion angles was used at two stages of weight acceptance; initial contact (IC) and peak knee flexion (PKF) between involved (INV) and uninvolved (UNINV) knees across the three testing times. The analysis showed an interaction between stage of weight acceptance and side (F=18.716; p=0.001). There were significant interlimb differences in knee excursion during weight acceptance (flexion angle from IC to PKF) for the first (5.3°; p=0.005), second (5.2°; p=0.001) and third (5.2°; p=0.001) testing times; the affected knee demonstrating less movement. Excursions of the INV and the UNINV knees did not change across testing times. Multivariate analysis of goniometric total knee ROM between the INV and UNINV knee across testing times showed an interaction by side (F=29.996; p<0.001) but not for testing time. The INV knee’s ROM was on average 8° less than that of the UNINV at the first testing session (p=0.003), 5.2° less at the second (p<0.001) and 7.2° less at the third testing session (p=0.001). Knee ROM of either knee did not change across testing times. Larger knee flexion ROM at baseline predicted greater improvement on KOS scores on the first post-treatment testing session (r2=.540; p=0.004). Larger knee flexion ROM at the first post-treatment predicted greater improvements on KOS scores at the later testing session (r2=.398; p=0.021). Significant within-subjects effects of testing times on KOS scores were found(F=4.65; p=0.02),on 6MW distance (F=12.010; p<0.001) and QI (F=5.903; p=0.013). Discussion: Subjects demonstrated significantly improved function after a series of intra-articular hyaluronan injections as evaluated with the KOS and functional testing. Kinematic interlimb differences were unchanged across testing times despite these improvements. Goniometric measures of total knee range of motion confirmed interlimb differences in available joint ROM. Although subjects demonstrated ample functional ROM, this was not utilized during weight acceptance. The truncated knee flexion may impede the shock absorbing mechanism of the knee and impact the progression of knee OA. While improvements in self reported scores were not maintained at the 5 month evaluation, walking distance continued to improve over time. This indicates that functional improvements persisted despite concurrently increasing symptoms

High resolution X-ray scattering studies of structural phase transitions in underdoped La2−x_{2-x}Bax_xCuO4_4

We have studied structural phase transitions in high quality underdoped La$_{2-x}$Ba$_x$CuO$_4$ single crystals using high resolution x-ray scattering techniques. Critical properties associated with the continuous High Temperature Tetragonal (HTT, $I4/mmm$) to Middle Temperature Orthorhombic (MTO, $Cmca$) phase transition were investigated in single crystal samples with x=0.125, 0.095, and 0.08 and we find that all behavior is consistent with three dimensional XY criticality, as expected from theory. Power law behavior in the orthorhombic strain, 2(a-b)/(a+b), is observed over a remarkably wide temperature range, spanning most of the MTO regime in the phase diagram. Low temperature measurements investigating the Low Temperature Tetragonal (LTT, $P4_{2}/ncm$) phase, below the strongly discontinuous MTO$\to$LTT phase transition, in x=0.125 and x=0.095 samples show that the LTT phase is characterized by relatively broad Bragg scattering, compared with that observed at related wavevectors in the HTT phase. This shows that the LTT phase is either an admixture of tetragonal and orthorhombic phases, or that it is orthorhombic with very small orthorhombic strain, consistent with the ``less orthorhombic" low temperature structure previously reported in mixed La$_{2-x}$Sr$_{x-y}$Ba$_y$CuO$_4$ single crystals. We compare the complex temperature-composition phase diagram for the location of structural and superconducting phase transitions in underdoped La$_{2-x}$Ba$_x$CuO$_4$ and find good agreement with results obtained on polycrystalline samples.Comment: 8 pages, 7 figures, 1 tabl

Drought-stressed, irrigated, and additive-treated corn silages for growing cattle

Cattle fed drought-stressed corn silage gained about 10% slower but were just as efficient as cattle fed irrigated corn silage. Because the irrigated corn out yielded the drought corn (17.4 VS. 8.2 tons per acre), the irrigated silage gave a much higher cattle gain per acre (1928 VS. 940 1b). Silo Guard II®-treated silage had an advantage in DM recovery and feed conversion over its control and produced 4.6 more pounds of cattle gain per ton of crop ensiled. Cattle fed H/M Inoculant®- treated silage gained significantly faster than cattle fed the control, however, the treated silage gave only slight improvements in DM recovery and gain per ton of crop ensiled

Magnetism of the LTT phase of Eu doped La_{2-x}Sr_xCuO_4

The ESR signal of Gd spin probes (0.5 at %) as well as the static normal state susceptibility of Eu (J(Eu^{3+})=0) doped La_{2-x-y}Sr_xEu_yCuO_4 reveal pronounced changes of the Cu magnetism at the structural transition from the orthorhombic to the low temperature tetragonal phase for all non-superconducting compositions. Both a jumplike decrease of \chi as well as the ESR data show an increase of the in-plane magnetic correlation length in the LTT phase. From the Gd^{3+} ESR linewidth we find that for specific Eu and Sr concentrations in the LTT phase the correlation length increases up to more than 100 lattice constants and the fluctuation frequency of the CuO_2 spin system slows down to 10^{10}- 10^{11}sec^{-1}. However, there is no static order above T ~ 8K in contrast to the LTT phase of Nd doped La_{2-x}Sr_xCuO_4 with pinned stripe correlations.Comment: 7 pages, RevTex, 3 eps figures. To appear in the Proceedings of the International Conference "Stripes, Lattice Instabilities and High Tc Superconductivity", (Rome, Dec. 1996

Soft phonons and structural phase transitions in La1.875_{1.875}Ba0.125_{0.125}CuO4_{4}

Soft phonon behavior associated with a structural phase transition from the low-temperature-orthorhombic (LTO) phase ($Bmab$ symmetry) to the low-temperature-tetragonal (LTT) phase ($P4_{2}/ncm$ symmetry) was investigated in La$_{1.875}$Ba$_{0.125}$CuO$_{4}$ using neutron scattering. As temperature decreases, the TO-mode at $Z$-point softens and approaches to zero energy around $T_{\rm d2}=62$ K, where the LTO -- LTT transition occurs. Below $T_{\rm d2}$, the phonon hardens quite rapidly and it's energy almost saturates below 50 K. At $T_{\rm d2}$, the energy dispersion of the soft phonon along in-plane direction significantly changes while the dispersion along out-of-plane direction is almost temperature independent. Coexistence between the LTO phase and the LTT phase, seen in both the soft phonon spectra and the peak profiles of Bragg reflection, is discussed in context of the order of structural phase transitions.Comment: 6 pages, 8 figure

Diagonal static spin correlation in the low temperature orthorhombic Pccn phase of La1.55Nd0.4Sr0.05CuO4

Elastic neutron scattering measurements have been performed on Nd, Sr co-doped La1.55Nd0.4Sr0.05CuO4, which exhibits a structural phase transition at Ts ~ 60K from the low temperature orthorhombic Bmab phase (labelled LTO1) to the low temperature orthorhombic Pccn phase (labelled LTO2). At low temperatures, well below Ts, elastic magnetic peaks are observed at the ``diagonal'' incommensurate (IC) positions (0, 1+/-0.055, 0), with modulation direction only along the orthorhombic b-axis just as in Nd-free La1.95Sr0.05CuO4. In the present study, the one-dimensionality of the IC modulation, which is naturally explained by a stripe model, is clearly demonstrated with our "single-domain" crystal. The temperature dependence of the IC peak intensity suggests a substantial contribution from the Nd3+ spins below ~3K. Consistent with this, the L dependence of the magnetic scattering is accurately accounted for by a model in which the contribution of the Nd3+ spins is explicitly included.Comment: 8 pages, 8 figure