Deep soil flipping increases carbon stocks of New Zealand grasslands.

Sequestration of soil organic carbon (SOC) has been recognized as an opportunity to off-set global carbon dioxide (CO2 ) emissions. Flipping (full inversion to 1-3 m) is a practice used on New Zealand's South Island West Coast to eliminate water-logging in highly podzolized sandy soils. Flipping results in burial of SOC formed in surface soil horizons into the subsoil and the transfer of subsoil material low in SOC to the "new" topsoil. The aims of this study were to quantify changes in the storage and stability of SOC over a 20-year period following flipping of high-productive pasture grassland. Topsoils (0-30 cm) from sites representing a chronosequence of flipping (3-20 years old) were sampled (2005/07) and re-sampled (2017) to assess changes in topsoil carbon stocks. Deeper samples (30-150 cm) were also collected (2017) to evaluate the changes in stocks of SOC previously buried by flipping. Density fractionation was used to determine SOC stability in recent and buried topsoils. Total SOC stocks (0-150 cm) increased significantly by 69 ± 15% (179 ± 40 Mg SOC ha-1 ) over 20 years following flipping. Topsoil burial caused a one-time sequestration of 160 ± 14 Mg SOC ha-1 (30-150 cm). The top 0-30 cm accumulated 3.6 Mg SOC ha-1  year-1 . The chronosequence and re-sampling revealed SOC accumulation rates of 1.2-1.8 Mg SOC ha-1  year-1 in the new surface soil (0-15 cm) and a SOC deficit of 36 ± 5% after 20 years. Flipped subsoils contained up to 32% labile SOC (compared to <1% in un-flipped subsoils) thus buried SOC was preserved. This study confirms that burial of SOC and the exposure of SOC depleted subsoil results in an overall increase of SOC stocks of the whole soil profile and long-term SOC preservation.

Effects of climate change on the delivery of soil-mediated ecosystem services within the primary sector in temperate ecosystems: a review and New Zealand case study.

Future human well-being under climate change depends on the ongoing delivery of food, fibre and wood from the land-based primary sector. The ability to deliver these provisioning services depends on soil-based ecosystem services (e.g. carbon, nutrient and water cycling and storage), yet we lack an in-depth understanding of the likely response of soil-based ecosystem services to climate change. We review the current knowledge on this topic for temperate ecosystems, focusing on mechanisms that are likely to underpin differences in climate change responses between four primary sector systems: cropping, intensive grazing, extensive grazing and plantation forestry. We then illustrate how our findings can be applied to assess service delivery under climate change in a specific region, using New Zealand as an example system. Differences in the climate change responses of carbon and nutrient-related services between systems will largely be driven by whether they are reliant on externally added or internally cycled nutrients, the extent to which plant communities could influence responses, and variation in vulnerability to erosion. The ability of soils to regulate water under climate change will mostly be driven by changes in rainfall, but can be influenced by different primary sector systems' vulnerability to soil water repellency and differences in evapotranspiration rates. These changes in regulating services resulted in different potentials for increased biomass production across systems, with intensively managed systems being the most likely to benefit from climate change. Quantitative prediction of net effects of climate change on soil ecosystem services remains a challenge, in part due to knowledge gaps, but also due to the complex interactions between different aspects of climate change. Despite this challenge, it is critical to gain the information required to make such predictions as robust as possible given the fundamental role of soils in supporting human well-being.

Global Research Alliance N2 O chamber methodology guidelines: Design considerations.

Terrestrial ecosystems, both natural ecosystems and agroecosystems, generate greenhouse gases (GHGs). The chamber method is the most common method to quantify GHG fluxes from soil-plant systems and to better understand factors affecting their generation and mitigation. The objective of this study was to review and synthesize literature on chamber designs (non-flow-through, non-steady-state chamber) and associated factors that affect GHG nitrous oxide (N2 O) flux measurement when using chamber methods. Chamber design requires consideration of many facets that include materials, insulation, sealing, venting, depth of placement, and the need to maintain plant growth and activity. Final designs should be tailored, and bench tested, in order to meet the nuances of the experimental objectives and the ecosystem under study while reducing potential artifacts. Good insulation, to prevent temperature fluctuations and pressure changes, and a high-quality seal between base and chamber are essential. Elimination of pressure differentials between headspace and atmosphere through venting should be performed, and designs now exist to eliminate Venturi effects of earlier tube-type vent designs. The use of fans within the chamber headspace increases measurement precision but may alter the flux. To establish best practice recommendations when using fans, further data are required, particularly in systems containing tall plants, to systematically evaluate the effects that fan speed, position, and mixing rate have on soil gas flux.

Endovascular repair of nonruptured thoracic aortic aneurysms: systematic review.

Thoracic aortic aneurysms represent a major health problem. Untreated thoracic aortic aneurysms may rupture, which has a dismal outcome. The standard treatment for thoracic aneurysms is open surgical repair, but it is associated with high mortality and morbidity. Endovascular repair provides a less invasive and safer alternative. A systematic review was performed of all published literature on the above subject. Our primary objective was to measure 30-day mortality for nonruptured thoracic aortic aneurysms. Studies describing other pathologies, such as aortic dissection, mycotic aneurysms, penetrating ulcers, traumatic transactions, and pseudoaneurysms, and studies from which independent data for thoracic aortic aneurysm could not be separately extracted were excluded. Case series describing less than 10 patients and all case series describing ruptures or concealed ruptures were excluded as well. Twenty-six case series and one comparative study were identified. This formed a cohort of 1,038 patients. Technical success was possible in more than 97% of patients. The 30-day mortality was calculated to be 5.1% even though the group under study was mostly those who were refused surgery by a surgeon or had a higher surgical risk. The incidence of paraplegia and stroke was 3.1% and 4.7%, respectively. Early endoleak was seen in 16.7% of patients, whereas 11.7% of patients developed late endoleak, but most did not require any additional procedure. The rate of reintervention was 14.9%. The 12-month mortality rate was 14.2%. Endovascular repair shows encouraging short-term results. It is associated with significantly less mortality and morbidity, but long-term results need to be further investigated.