The effect of abrupt climatic warming on biogeochemical cycling and N2O emissions in a terrestrial ecosystem

The large, rapid increase in atmospheric N2O concentrations that occurred concurrent with the abrupt warming at the end of the Last Glacial period might have been the result of a reorganization in global biogeochemical cycles. To explore the sensitivity of nitrogen cycling in terrestrial ecosystems to abrupt warming, we combined a scenario of climate and vegetation composition change based on multiproxy data for the Oldest Dryas–Bølling abrupt warming event at Gerzensee, Switzerland, with a biogeochemical model that simulates terrestrial N uptake and release, including N2O emissions. As for many central European sites, the pollen record at the Gerzensee is remarkable for the abundant presence of the symbiotic nitrogen fixer Hippophaë rhamnoides (L.) during the abrupt warming that also marks the beginning of primary succession on immature glacial soils. Here we show that without additional nitrogen fixation, climate change results in a significant increase of N2O emissions of approximately factor 3.4 (from 6.4 ± 1.9 to 21.6 ± 5.9 mg N2O–N m− 2 yr− 1). Each additional 1000 mg m− 2 yr− 1 of nitrogen added to the ecosystem through N-fixation results in additional N2O emissions of 1.6 mg N2O–N m− 2 yr− 1 for the time with maximum H. rhamnoides coverage. Our results suggest that local reactions of emissions to abrupt climate change could have been considerably faster than the overall atmospheric concentration changes observed in polar ice. Nitrogen enrichment of soils due to the presence of symbiotic N-fixers during early primary succession not only facilitates the establishment of vegetation on soils in their initial stage of development, but can also have considerable influence on biogeochemical cycles and the release of reactive nitrogen trace gases to the atmosphere.

Factors controlling decomposition rates of fine root litter in temperate forests and grasslands

Background and aims Fine root decomposition contributes significantly to element cycling in terrestrial ecosystems. However, studies on root decomposition rates and on the factors that potentially influence them are fewer than those on leaf litter decomposition. To study the effects of region and land use intensity on fine root decomposition, we established a large scale study in three German regions with different climate regimes and soil properties. Methods In 150 forest and 150 grassland sites we deployed litterbags (100 μm mesh size) with standardized litter consisting of fine roots from European beech in forests and from a lowland mesophilous hay meadow in grasslands. In the central study region, we compared decomposition rates of this standardized litter with root litter collected on-site to separate the effect of litter quality from environmental factors. Results Standardized herbaceous roots in grassland soils decomposed on average significantly faster (24 ± 6 % mass loss after 12 months, mean ± SD) than beech roots in forest soils (12 ± 4 %; p < 0.001). Fine root decomposition varied among the three study regions. Land use intensity, in particular N addition, decreased fine root decomposition in grasslands. The initial lignin:N ratio explained 15 % of the variance in grasslands and 11 % in forests. Soil moisture, soil temperature, and C:N ratios of soils together explained 34 % of the variance of the fine root mass loss in grasslands, and 24 % in forests. Conclusions Grasslands, which have higher fine root biomass and root turnover compared to forests, also have higher rates of root decomposition. Our results further show that at the regional scale fine root decomposition is influenced by environmental variables such as soil moisture, soil temperature and soil nutrient content. Additional variation is explained by root litter quality.

Heuristic decomposition and LP-based scheduling in make-and-pack production

In this paper, we are concerned about the short-term scheduling of industrial make-and-pack production processes. The planning problem consists in minimizing the production makespan while meeting given end-product demands. Sequence-dependent changeover times, multi-purpose storage units with finite capacities, quarantine times, batch splitting, partial equipment connectivity, material transfer times, and a large number of operations contribute to the complexity of the problem. Known MILP formulations cover all technological constraints of such production processes, but only small problem instances can be solved in reasonable CPU times. In this paper, we develop a heuristic in order to tackle large instances. Under this heuristic, groups of batches are scheduled iteratively using a novel MILP formulation; the assignment of the batches to the groups and the scheduling sequence of the groups are determined using a priority rule. We demonstrate the applicability by means of a real-world production process.

Isotopic constraints on marine and terrestrial N2O emissions during the last deglaciation

Nitrous oxide (N2O) is an important greenhouse gas and ozone-depleting substance that has anthropogenic as well as natural marine and terrestrial sources. The tropospheric N2O concentrations have varied substantially in the past in concert with changing climate on glacial–interglacial and millennial timescales. It is not well understood, however, how N2O emissions from marine and terrestrial sources change in response to varying environmental conditions. The distinct isotopic compositions of marine and terrestrial N2O sources can help disentangle the relative changes in marine and terrestrial N2O emissions during past climate variations. Here we present N2O concentration and isotopic data for the last deglaciation, from 16,000 to 10,000 years before present, retrieved from air bubbles trapped in polar ice at Taylor Glacier, Antarctica. With the help of our data and a box model of the N2O cycle, we find a 30 per cent increase in total N2O emissions from the late glacial to the interglacial, with terrestrial and marine emissions contributing equally to the overall increase and generally evolving in parallel over the last deglaciation, even though there is no a priori connection between the drivers of the two sources. However, we find that terrestrial emissions dominated on centennial timescales, consistent with a state-of-the-art dynamic global vegetation and land surface process model that suggests that during the last deglaciation emission changes were strongly influenced by temperature and precipitation patterns over land surfaces. The results improve our understanding of the drivers of natural N2O emissions and are consistent with the idea that natural N2O emissions will probably increase in response to anthropogenic warming.

The Blinder-Oaxaca decomposition for linear regression models

The counterfactual decomposition technique popularized by Blinder (1973, Journal of Human Resources, 436–455) and Oaxaca (1973, International Economic Review, 693–709) is widely used to study mean outcome differences between groups. For example, the technique is often used to analyze wage gaps by sex or race. This article summarizes the technique and addresses several complications, such as the identification of effects of categorical predictors in the detailed decomposition or the estimation of standard errors. A new command called oaxaca is introduced, and examples illustrating its usage are given.

Decomposition studies of group 6 hexacarbonyl complexes. Part 1: Production and decomposition of Mo(CO)6 and W(CO)6

Chemical studies of superheavy elements require fast and efficient techniques, due to short half-lives and low production rates of the investigated nuclides. Here, we advocate for using a tubular flow reactor for assessing the thermal stability of the Sg carbonyl complex – Sg(CO)6. The experimental setup was tested with Mo and W carbonyl complexes, as their properties are established and supported by theoretical predictions. The suggested approach proved to be effective in discriminating between the thermal stabilities of Mo(CO)6 and W(CO)6. Therefore, an experimental verification of the predicted Sg–CO bond dissociation energy seems to be feasible by applying this technique. By investigating the effect of 104,105Mo beta-decay on the formation of 104,105Tc carbonyl complex, we estimated the lower reaction time limit for the metal carbonyl synthesis in the gas phase to be more than 100 ms. We examined further the influence of the wall material of the recoil chamber, the carrier gas composition, the gas flow rate, and the pressure on the production yield of 104Mo(CO)6, so that the future stability tests with Sg(CO)6 can be optimized accordingly.

An 'Ideal' Decomposition of Industry Dynamics: An Application to the Nationwide and State Level U.S. Banking Industry

This paper considers the aggregate performance of the banking industry, applying a modified and extended dynamic decomposition of bank return on equity. The aggregate performance of any industry depends on the underlying microeconomic dynamics within that industry . adjustments within banks, reallocations between banks, entry of new banks, and exit of existing banks. Bailey, Hulten, and Campbell (1992) and Haltiwanger (1997) develop dynamic decompositions of industry performance. We extend those analyses to derive an ideal decomposition that includes their decomposition as one component. We also extend the decomposition, consider geography, and implement decomposition on a state-by-state basis, linking that geographic decomposition back to the national level. We then consider how deregulation of geographic restrictions on bank activity affects the components of the state-level dynamic decomposition, controlling for competition and the state of the economy within each state and employing fixed- and random-effects estimation for a panel database across the fifty states and the District of Columbia from 1976 to 2000.

Foreign and Domestic Bank Performances: An Ideal Decomposition of Industry Dynamics

The aggregate performance of the banking industry depends on the underlying microlevel dynamics within that industry. adjustments within banks, reallocations between banks, entries of new banks, and exits of existing banks. This paper develops a generalized ideal dynamic decomposition and applies it to the return on equity of foreign and domestic commercial banks in Korea from 1994 to 2000. The sample corresponds to the Asian financial crisis and the final stages of a long process of deregulation and privatization in the Korean banking industry. The comparison of our findings reveals that the overall performance of Korean banks largely reflects individual bank efficiencies, except immediately after the Asian financial crisis where restructuring played a more important role on average bank performance. Moreover, Korean regional banks started the restructuring process about one year before the Korean nationwide banks. Foreign bank performance, however, largely reflected individual bank efficiencies, even immediately after the Asian financial crisis.

Decomposition Rates and Nitrogen Release of Turf Grass Clippings

Decomposition rates and N release patterns of turfgrass clippings from lawns are not well understood. Litter bags containing clippings were inserted into the thatch layer of a coolseason turf. The experiment was arranged as a 2 × 4 factorial in a randomized complete block design with three replicates. Treatments included four rates of N fertilizer (0, 98, 196, and 392 kg N ha-1 yr-1) and two clipping treatments (returned vs. removed). Litter bags were removed periodically over the growing season and samples were analyzed for biomass, N and C concentrations, and C:N ratio on an ash-free basis. Percentage N loss from the clippings after 16 weeks ranged from 88% to 93% at the 0 and 392 kg N ha-1 rates, respectively, and from 86% to 94% when clippings were removed (CRM) or returned (CRT), respectively. Percentage C loss from the clippings ranged from 94% to 95% at the 0 and 392 kg N ha-1 rates, respectively, and from 92% to 96% with CRM and CRT, respectively. Cumulative N release was similar across N fertilization rates, (ranging from 131 g N kg-1 to 135 g N kg-1 tissue) but was higher for CRT (151 g N kg-1 tissue) than for CRM (128 g N kg-1 tissue). Grass clippings decomposed rapidly and released N quickly when returned to the turf thatch layer. This indicates the potential for reduced N fertilization when clippings are returned. Such rapid decomposition also suggests that the contribution of grass clippings to thatch development is negligible.