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Globally, soils store two to three times as much carbon as currently resides in the atmosphere, and it is critical to understand how soil greenhouse gas (GHG) emissions and uptake will respond to ongoing climate change. In particular, the soil-to-atmosphere CO2 flux, commonly though imprecisely termed soil respiration (RS ), is one of the largest carbon fluxes in the Earth system. An increasing number of high-frequency RS measurements (typically, from an automated system with hourly sampling) have been made over the last two decades; an increasing number of methane measurements are being made with such systems as well. Such high frequency data are an invaluable resource for understanding GHG fluxes, but lack a central database or repository. Here we describe the lightweight, open-source COSORE (COntinuous SOil REspiration) database and software, that focuses on automated, continuous and long-term GHG flux datasets, and is intended to serve as a community resource for earth sciences, climate change syntheses and model evaluation. Contributed datasets are mapped to a single, consistent standard, with metadata on contributors, geographic location, measurement conditions and ancillary data. The design emphasizes the importance of reproducibility, scientific transparency and open access to data. While being oriented towards continuously measured RS , the database design accommodates other soil-atmosphere measurements (e.g. ecosystem respiration, chamber-measured net ecosystem exchange, methane fluxes) as well as experimental treatments (heterotrophic only, etc.). We give brief examples of the types of analyses possible using this new community resource and describe its accompanying R software package.

Despite the fundamental importance of soil temperature for Earth's carbon and energy budgets, ecosystem functioning, and agricultural production, studies of climate change impacts on soil processes have mainly relied on air temperatures, assuming they are accurate proxies for soil temperatures. We evaluated changes in soil temperature, moisture, and air temperature predicted over the 21st century from 14 Earth system models. The model ensemble predicted a global mean soil warming of 2.3 ± 0.7 and 4.5 ± 1.1 °C at 100-cm depth by the end of the 21st century for RCPs 4.5 and 8.5, respectively. Soils at 100 cm warmed at almost exactly the same rate as near-surface (~1 cm) soils. Globally, soil warming was slightly slower than air warming above it, and this difference increased over the 21st century. Regionally, soil warming kept pace with air warming in tropical and arid regions but lagged air warming in colder regions. Thus, air warming is not necessarily a good proxy for soil warming in cold regions where snow and ice impede the direct transfer of sensible heat from the atmosphere to soil. Despite this effect, high-latitude soils were still projected to warm faster than elsewhere, albeit at slower rates than surface air above them. When compared with observations, the models were able to capture soil thermal dynamics in most biomes, but some failed to recreate thermal properties in permafrost regions. Particularly in cold regions, using soil warming rather than air warming projections may improve predictions of temperature-sensitive soil processes.

Multiphasic studies were conducted to quantify how sulfur fertilization influences nitrate levels in hops, and how nitrogen and sulfur fertilizer dose jointly affect hop yield, brewing chemistry, and aroma of hops and beer. In an observational study of commercial lots of Simcoe® hops, a weak positive correlation was found between sulfur and nitrate concentrations. In field studies with Simcoe® in Washington, factorial combinations of representative low and high rates of nitrogen and sulfur fertilizer revealed that nitrate content of cones increased 13 to 22% with increasing nitrogen dose yet declined 8 to 8.7% with an increasing sulfur dose. Yield was unaffected by the lower dose of nitrogen when sulfur dose was high; effects on α-acids, total oil, and hop and beer aroma were not detected. Cysteine-3SH and cysteinylglycine-3SH were reduced 19% and 23%, in cones that received the higher sulfur dose in one year; other thiols and precursors were unaffected. In cultivar Willamette in Oregon, increasing sulfur dose over an 11-fold range by varying nitrogen fertilizer form from urea to ammonium sulfate had small to non-detectable effects on yield, α-acids, or nitrate concentrations. Hop aroma and brewing characteristics appear largely invariant to sulfur fertilization; increased sulfur fertilization may reduce hop nitrate levels modestly in certain situations. [ABSTRACT FROM AUTHOR]

Irrigation is essential for hop production in the Pacific Northwestern United States, the primary growing region in the U.S. Irrigation water supplies can be inadequate in drought years and may become more variable in the future due to climate variability and increasing non-agricultural demand. In this research, the impact of delayed timing of the first irrigation of the season on hop yield and cone quality metrics in the cultivars Cascade and Zeus over three years was evaluated. The impact of delayed irrigation depended on year and cultivar, with larger impacts on yield of Cascade as compared to Zeus in this study. In Cascade, yield decreased 10.8% to 16.2% when the timing of the first irrigation was delayed by 10 or 18 days after training, respectively. However, cone quality factors were statistically similar when data were aggregated over all three years. In Zeus, delaying the first irrigation did not have detectable effects on brewing quality or yield in any individual year or when data were aggregated over all years. Thus, while even a brief delay in irrigation may substantially reduce yield in some cultivars such as Cascade, these effects were cultivar-dependent and impacts on brewing quality appeared small or undetectable. [ABSTRACT FROM AUTHOR]

Increasing use of automated soil respiration chambers in recent years has demonstrated complex diel relationships between soil respiration and temperature that are not apparent from less frequent measurements. Soil surface flux is often lagged from soil temperature by several hours, which results in semielliptical hysteresis loops when surface flux is plotted as a function of soil temperature. Both biological and physical explanations have been suggested for hysteresis patterns, and there is currently no consensus on their causes or how such data should be analyzed to interpret the sensitivity of respiration to temperature. We used a one-dimensional soil CO and heat transport model based on physical first principles to demonstrate a theoretical basis for lags between surface flux and soil temperatures. Using numerical simulations, we demonstrated that diel phase lags between surface flux and soil temperature can result from heat and CO transport processes alone. While factors other than temperature that vary on a diel basis, such as carbon substrate supply and atmospheric CO concentration, can additionally alter lag times and hysteresis patterns to varying degrees, physical transport processes alone are sufficient to create hysteresis. Therefore, the existence of hysteresis does not necessarily indicate soil respiration is influenced by photosynthetic carbon supply. We also demonstrated how lags can cause errors in Q values calculated from regressions of surface flux and soil temperature measured at a single depth. Furthermore, synchronizing surface flux and soil temperature to account for transport-related lags generally does not improve Q estimation. In order to calculate the sensitivity of soil respiration to temperature, we suggest using approaches that account for the gradients in temperature and production existing within the soil. We conclude that consideration of heat and CO transport processes is a requirement to correctly interpret diel soil respiration patterns. [ABSTRACT FROM AUTHOR]