Effects of fertilization and clipping on carbon, nitrogen storage, and soil microbial activity in a natural grassland in southern China.

Grassland managements can affect carbon (C) and nitrogen (N) storage in grassland ecosystems with consequent feedbacks to climate change. We investigated the impacts of compound fertilization and clipping on grass biomass, plant and soil (0-20 cm depth) C, N storage, plant and soil C: N ratios, soil microbial activity and diversity, and C, N sequestration rates in grassland in situ in the National Dalaoling Forest Park of China beginning July, 2011. In July, 2012, the fertilization increased total biomass by 30.1%, plant C by 34.5%, plant N by 79.8%, soil C by 18.8% and soil N by 23.8% compared with the control, respectively. Whereas the clipping decreased total biomass, plant C and N, soil C and N by 24.9%, 30.3%, 39.3%, 18.5%, and 19.4%, respectively, when compared to the control. The plant C: N ratio was lower for the fertilization than for the control and the clipping treatments. The soil microbial activity and diversity indices were higher for the fertilization than for the control. The clipping generally exhibited a lower level of soil microbial activity and diversity compared to the control. The principal component analysis indicated that the soil microbial communities of the control, fertilization and clipping treatments formed three distinct groups. The plant C and N sequestration rates of the fertilization were significantly higher than the clipping treatment. Our results suggest that fertilization is an efficient management practice in improving the C and N storage of the grassland ecosystem via increasing the grass biomass and soil microbial activity and diversity

Oligo(3,6-phenanthrene ethynylenes): Synthesis, Characterization, and Photoluminescence

A series of highly fluorescent, oligo­(3,6-phenanthrene ethynylenes) (<b>F1</b>–<b>F7</b>) were synthesized, and their photophysical behavior was systematically investigated. They emitted light with highly emissive quantum yields, up to 0.92. Emissive wavelengths of these compounds relied on the number of phenanthrene blocks existing in the oligomers. Red-shifted emissions were observed as the number of phenanthrenes increased. On the basis of theoretical calculations, helical structures could be formed for <b>F4</b>–<b>F7</b>, indicating that the excimer emissions might be observed for <b>F4</b>–<b>F7</b> due to the intramolecular π–π stackings of phenanthrenes in the helical structures. However, excimer emissions were only observed for <b>F5</b>–<b>F7</b> in dilute cyclohexane and for <b>F6</b> and <b>F7</b> in dilute methylene chloride, respectively. No excimer emission was observed for <b>F4</b>–<b>F7</b> in dilute tetrahydrofuran due to the degree of solvation

Spectroelectrochemistry of water oxidation kinetics in molecular versus heterogeneous oxide iridium electrocatalysts

Water oxidation is the step limiting the efficiency of electrocatalytic hydrogen production from water. Spectroelectro-chemical analyzes are employed to make a direct comparison of water oxidation reaction kinetics between a molecu-lar catalyst, the dimeric iridium catalyst [Ir2(pyalc)2(H2O)4-(µ-O)]2+ (IrMolecular, pyalc = 2-(2’pyridinyl)-2-propanolate) immobilized on a mesoporous indium tin oxide (ITO) substrate, with that of an heterogenous electrocatalyst, an amorphous hydrous iridium (IrOx) film. For both systems, four analogous redox states were detected, with the for-mation of Ir(4+)-Ir(5+) being the potential-determining step in both cases. However, the two systems exhibit distinct water oxidation reaction kinetics, with potential-independent first-order kinetics for IrMolecular contrasting with poten-tial-dependent kinetics for IrOx. This is attributed to water oxidation on the heterogenous catalyst requiring co-operative effects between neighboring oxidized Ir centers. The ability of IrMolecular to drive water oxidation without such co-operative effects is explained by the specific coordination environment around its Ir centers. These distinc-tions between molecular and heterogenous reaction kinetics are shown to explain the differences observed in their water oxidation electrocatalytic performance under different potential conditions

Effects of fertilization and clipping on microbial functional diversity as evaluated by substrate richness (<i>S</i>), Shannon's diversity index (<i>H</i>′), Shannon's evenness index (<i>E (S)</i>), McIntosh diversity index (<i>U</i>) and McIntosh evenness index (<i>E (M)</i>) in July, 2012 (72 h).

<p>The data represent means ± SE (<i>n</i> = 5). Letters a, b, c in a column indicate statistical significance base on Fisher's protected LSD test (<i>p</i><0.05) among the three different treatments.</p

The shoot (a), root (b), litter (c) and total biomass (d) variation under the different treatments over time. Vertical bars represent standard error (SE). <i>n</i> = 5.

<p>The shoot (a), root (b), litter (c) and total biomass (d) variation under the different treatments over time. Vertical bars represent standard error (SE). <i>n</i> = 5.</p

Spectroelectrochemistry of Water Oxidation Kinetics in Molecular versus Heterogeneous Oxide Iridium Electrocatalysts.

Funder: bp International Centre for Advanced MaterialsWater oxidation is the step limiting the efficiency of electrocatalytic hydrogen production from water. Spectroelectrochemical analyses are employed to make a direct comparison of water oxidation reaction kinetics between a molecular catalyst, the dimeric iridium catalyst [Ir2(pyalc)2(H2O)4-(μ-O)]2+ (IrMolecular, pyalc = 2-(2'pyridinyl)-2-propanolate) immobilized on a mesoporous indium tin oxide (ITO) substrate, with that of an heterogeneous electrocatalyst, an amorphous hydrous iridium (IrOx) film. For both systems, four analogous redox states were detected, with the formation of Ir(4+)-Ir(5+) being the potential-determining step in both cases. However, the two systems exhibit distinct water oxidation reaction kinetics, with potential-independent first-order kinetics for IrMolecular contrasting with potential-dependent kinetics for IrOx. This is attributed to water oxidation on the heterogeneous catalyst requiring co-operative effects between neighboring oxidized Ir centers. The ability of IrMolecular to drive water oxidation without such co-operative effects is explained by the specific coordination environment around its Ir centers. These distinctions between molecular and heterogeneous reaction kinetics are shown to explain the differences observed in their water oxidation electrocatalytic performance under different potential conditions

The relationships of AWCD of soil microbial community with soil C: N ratio (a) and plant C: N ratio (b) in July, 2012.

<p>The relationships of AWCD of soil microbial community with soil C: N ratio (a) and plant C: N ratio (b) in July, 2012.</p

Carbon and nitrogen storage and C: N ratio among plant parts under different grassland treatments in July, 2012.

<p>The data represent means ± SE (<i>n</i> = 5). Letters a, b, c in a column indicate statistical significance base on Fisher's protected LSD test (<i>p</i><0.05) among the three different treatments.</p

Carbon and nitrogen storage and C: N ratio of soils at the 0–5, 5–10, and 10–20 cm depths under different grassland treatments in July, 2012.

<p>The data represent means ± SE (<i>n</i> = 5). Letters a, b, c in a column indicate statistical significance base on Fisher's protected LSD test (<i>p</i><0.05) among the three different treatments.</p