Non-microbial methane emissions from soils

Traditionally, methane (CH4) is anaerobically formed by methanogenic archaea. However, non-microbial CH4 can also be produced from geologic processes, biomass burning, animals, plants, and recently identified soils. Recognition of non-microbial CH4 emissions from soils remains inadequate. To better understand this phenomenon, a series of laboratory incubations were conducted to examine effects of temperature, water, and hydrogen peroxide (H2O2) on CH4 emissions under both aerobic and anaerobic conditions using autoclaved (30 min, 121 degrees C) soils and aggregates (>2000 inn, A1; 2000-250 mu m, A2; 250-53 mu m, M1; and A2 > A1 > M2 and C-based emission an order of M2 > M1 > A1 > A2, demonstrating that both organic carbon quantity and property are responsible for CH4 emissions from soils at the scale of aggregate. Whole soil-based order of A2 > A1 > M1 > M2 suggests that non-microbial CH4 release from forest soils is majorly contributed by macro-aggregates (i.e., >250 mu m). The underlying mechanism is that organic matter through thermal treatment, photolysis, or reactions with free radicals produce CH4, which, in essence, is identical with mechanisms of other non-microbial sources, indicating that non-microbial CH4 production may be a widespread phenomenon in nature. This work further elucidates the importance of non-microbial CH4 formation which should be distinguished from the well-known microbial CH4 formation in order to define both roles in the atmospheric CH4 global budget. (C) 2013 Elsevier Ltd. All rights reserved

Interactive impacts of nitrogen input and water amendment on growing season fluxes of CO2, CH4, and N2O in a semiarid grassland, Northern China

Nitrogen and water are two important factors influencing GHG (primarily CO2 - carbon dioxide; CH4 - methane, and N2O - nitrous oxide) fluxes in semiarid grasslands. However, the interactive effects of nitrogen and water on GHG fluxes remain elusive. A 3-year (2010-2012) manipulative experiment was conducted to investigate the individual and interactive effects of nitrogen and water additions on GHG fluxes during growing seasons (May to September) in a semiarid grassland in Northern China. Accumulated throughout growing seasons, nitrogen input stimulated CO2 uptake by 33 +/- 1.0 g C m(-2) (g N)(-1), enhanced N2O emission by 1.2 +/- 0.3 mg N m(-2) (g N)(-1), and decreased CH4 uptake by 5.2 +/- 0.9 mg N m(-2) (g N)(-1); water amendment stimulated CO2 uptake by 0.2 +/- 0.1 g Cm-2 (mm H2O)(-1) and N2O emission by 0.2 +/- 0.02 mg N m(-2) (mm H2O)(-1) , decreased CH4 uptake by 0.3 +/- 0.1 mg C m(-2) (mm H2O)(-1). A synergistic effect between nitrogen and water was found on N2O flux in normal year while the additive effects of nitrogen and water additions were found on CH4 and CO2 uptakes during all experiment years, and on N2O-emission in dry years. The nitrogen addition had stronger impacts than water amendment on stimulating CH4 uptake in the normal year, while water was the dominant factor affecting CH4 uptake in dry years. For N2O emission, the N-stimulating impact was stronger in un-watered than in watered plots, and the water-stimulating impact was stronger in non-fertilized than in fertilized treatments in dry years. The interactive impacts of nitrogen and water additions on GHG fluxes advance our understanding of GHG fluxes in responses to multiple environmental factors. This data source could be valuable for validating ecosystem models in simulating GHG fluxes in a multiple factors environment. (C) 2016 Elsevier B.V. All rights reserved

Interactive impacts of nitrogen input and water amendment on growing season fluxes of CO2, CH4, and N2O in a semiarid grassland, Northern China

Nitrogen and water are two important factors influencing GHG (primarily CO2 - carbon dioxide; CH4 - methane, and N2O - nitrous oxide) fluxes in semiarid grasslands. However, the interactive effects of nitrogen and water on GHG fluxes remain elusive. A 3-year (2010-2012) manipulative experiment was conducted to investigate the individual and interactive effects of nitrogen and water additions on GHG fluxes during growing seasons (May to September) in a semiarid grassland in Northern China. Accumulated throughout growing seasons, nitrogen input stimulated CO2 uptake by 33 +/- 1.0 g C m(-2) (g N)(-1), enhanced N2O emission by 1.2 +/- 0.3 mg N m(-2) (g N)(-1), and decreased CH4 uptake by 5.2 +/- 0.9 mg N m(-2) (g N)(-1); water amendment stimulated CO2 uptake by 0.2 +/- 0.1 g Cm-2 (mm H2O)(-1) and N2O emission by 0.2 +/- 0.02 mg N m(-2) (mm H2O)(-1) , decreased CH4 uptake by 0.3 +/- 0.1 mg C m(-2) (mm H2O)(-1). A synergistic effect between nitrogen and water was found on N2O flux in normal year while the additive effects of nitrogen and water additions were found on CH4 and CO2 uptakes during all experiment years, and on N2O-emission in dry years. The nitrogen addition had stronger impacts than water amendment on stimulating CH4 uptake in the normal year, while water was the dominant factor affecting CH4 uptake in dry years. For N2O emission, the N-stimulating impact was stronger in un-watered than in watered plots, and the water-stimulating impact was stronger in non-fertilized than in fertilized treatments in dry years. The interactive impacts of nitrogen and water additions on GHG fluxes advance our understanding of GHG fluxes in responses to multiple environmental factors. This data source could be valuable for validating ecosystem models in simulating GHG fluxes in a multiple factors environment. (C) 2016 Elsevier B.V. All rights reserved

Physiological and proteomic analyses for seed dormancy and release in the perennial grass of Leymus chinensis

Seed dormancy is an important trait determining seed germination and seedling establishment of plants. Despite extensive studies on seed dormancy, relatively few studies have specifically focused on mechanisms underlying seed dormancy in wild perennial species. Leymus chinensis is a perennial grass forage with excellent nutritional value and one of the dominant species in the Eurasian steppe. In this study, the proteomic features for seed dormancy and release in the wild germplasm after ripening were analyzed by iTRAQ technology. Based on the wheat (Triticwn aestivum) protein database, a total of 281 differently expressed proteins were identified in L. chinensis non-dormant seeds versus dormant seeds, with 188 differentially decreased (fold change 1.2, P < 0.05). Based on the COG annotation, the proteins involved in chromatin structure and dynamics, intracellular trafficking, section, and vesicular transport, cytoskeleton were all increased differentially. In contrast, the proteins involved in RNA processing and modification, cell wall/membrane/envelope biogenesis, and signal transduction mechanisms were all decreased differentially. Based on the Mapman annotation and function enrichment, the decreased proteins mainly participated in photosynthesis and TCA cycle, while the increased proteins were involved in protein targeting, degradation, and synthesis, amino acid metabolism, lipid metabolism, redox, cell cycle, and DNA synthesis/ chromatin structure. After-ripening of L. chinensis dormant seeds was the transition from maturation to storage. Our proteomic analyses revealed that the dormancy release of L. chinensis seeds was related to the increases in tubulin, histone, and thioredoxins, and the decrease in L- ascorbate peroxidase. Based on these results, we proposed that an increase in reactive oxygen species (ROS) during after-ripening is an important driver to regulate dormancy release in L. chinensis seeds by modulating cytoskeleton and chromatin. These findings provide new insight for our mechanistic understanding of dormancy control in perennial grass forage

Effects of grazing on CO2, CH4, and N2O fluxes in three temperate steppe ecosystems

Terrestrial ecosystems play a critical role in regulating the emission and uptake of the most important greenhouse gases (GHGs) such as CO2, CH4, and N2O. However, the effects of grazing on these GHG fluxes in different steppe types remain unclear. Here, we compared the effects of grazing on seasonal CO2, CH4, and N2O fluxes in the meadow (MS), typical (TS), and desert (DS) temperate steppe ecosystems in northern China. CO2 emission rates increased from 311.4 +/- 73.2 to 349.6 +/- 55.4 mg.m(-2).h(-1) in MS, but decreased in TS (from 341.3 +/- 93.0 to 239.5 +/- 81.9 mg.m(-2).h(-1)) and DS ( from 212.1 +/- 53.7 to 163.0 +/- 83.4 mg.m(-2).h(-1)) in response to summer grazing (SG). N2O emission rates increased in MS from 4.7 +/- 2.2 to 8.1 +/- 3.4 mu g.m(-2).h(-1), but not significantly changed in TS (9.2 +/- 4.2 vs. 8.4 +/- 2.4 mu g.m(-2).h(-1)) and DS (6.3 +/- 1.5 vs. 5.7 +/- 1.6 mu g.m(-2).h(-1)) by SG. CH4 uptake rates increased in MS from 33.0 +/- 11.7 to 47.1 +/- 10.4 mu g.m(-2).h(-1) and decreased from 64.4 +/- 7.6 to 56.2 +/- 5.9 mu g.m(-2).h(-1) in TS in response to SG. In MS and DS, N2O emissions were positively related to seasonal CO2 emissions and negatively related to CH4 uptakes. No significant relationships were found between GHG fluxes in TS. Summer grazing did not affect the relationship between CO2 and N2O emissions in MS, but reduced the relationship by enhancing the effect of aboveground biomass (AGB) on N2O emission in DS. The significant negative relationship between CH4 uptake and N2O emission in MS and DS could be attributed to the significant relationship between soil temperature (ST) and AGB in MS and to the significant effects of soil moisture on both CH4 uptake and N2O emission in DS. The decrease in the magnitude of the correlation coefficients between CH4 uptake and N2O emission by SG was due to the negative relationship between ST and AGB simultaneously in MS and DS. Our results suggest that effects of SG on GHG fluxes varied in different steppes and the relationship among GHGs was steppe-dependent and SG also changed the relationship by affecting GHG fluxes induced by varied soil and environmental factors

Seasonal distribution of increased precipitation in maternal environments influences offspring performance of Potentilla tanacetifolia in a temperate steppe ecosystem

Aims Precipitation is predicted to increase in arid and semiarid regions under climate change, with greater changes in intra- and inter-annual distribution in the future. As a major limiting factor in these regions, changes in precipitation undoubtedly influence plant growth and productivity. However, how the temporal shifts in precipitation will impact plant populations are uncertain. Methods A 3-year field experiment and a greenhouse experiment were conducted in a temperate grassland in northern China to examine the impacts of seasonal (spring and summer) increased precipitation on offspring performance of a common species, Potentilla tanacetifolia. Important Findings Our results showed that the amounts and timing of increased precipitation both played important roles in regulating offspring performance of P. tanacetifolia in the temperate steppe ecosystem. Increased precipitation in spring at maternal stage stimulated seed production, germination percentage and seedling biomass, whereas increased precipitation in summer at maternal stage stimulated seedling biomass. The timing of increased precipitation influenced seed attributes, whereas the amount of increased precipitation influenced offspring seedling biomass. Our results indicate that population development of P. tanacetifolia may be underestimated under future increased precipitation regime, if the transgenerational effect is not taken into account