In Situ-Grown Ultrathin Catalyst Layers for Improving both Proton Exchange Membrane Fuel Cell and Anion Exchange Membrane Fuel Cell Performances.

The mass transport and ion conductivity in the catalyst layer are important for fuel cell performances. Here, we report an in situ-grown ultrathin catalyst layer (UTCL) to reduce the oxygen mass transport and a surface ionomer-coated gas diffusion layer method to reduce the ion conducting resistance. A significantly reduced catalyst layer thickness (ca. 1 µm) is achieved, and coupled with the ionomer introduction method, the ultrathin catalyst layer is in good contact with the membrane, resulting in high ion conductivity and high Pt utilization. This ultrathin catalyst layer is suitable for both proton exchange membrane fuel cells and anion exchange membrane fuel cells, giving peak power densities of 2.24 and 1.11 W cm-2, respectively, which represent an increase of more than 30% compared with the membrane electrode assembly (MEA) fabricated by using traditional Pt/C power catalysts. Electrochemical impedance spectra and limiting current tests demonstrate the reduced charge transfer, mass transfer, and ohmic resistances in the ultrathin catalyst layer membrane electrode assembly, resulting in the promoted fuel cell performances.

Spatial Distribution and Sustainable Development of Living Woody and Coarse Woody Debris in Warm-Temperate Deciduous Broadleaved Secondary Forests in China.

The investigation into the spatial patterns of living woody (LWD) and coarse woody debris (CWD) in warm-temperate deciduous broadleaved secondary forests serves as a foundational exploration of the mechanisms governing coexistence and mortality in forest ecosystems. The complete spatial randomness null model (CSR) was employed to analyze spatial distribution patterns, with the independent component null model (IC) and canonical correspondence analysis (CCA) utilized to elucidate spatial correlations and topographic influences. All three models were applied to LWD and CWD across various size classes within a 20-hectare plot in the Dongling Mountains. The study's findings indicate that both LWD and CWD predominantly exhibited aggregated patterns, transitioning to a random distribution as the size class increased. Both increasing abundance and maximum diameter at breast height (DBH) also have a significant influence on the distribution of species. Notably, rare species exhibited higher aggregation compared to common and abundant species. The spatial correlation results between LWD and CWD across various size classes predominantly showed positive correlations and uncorrelated patterns within the sampled plots. CCA analysis further revealed that elevation, convexity, slope, and aspect significantly influenced the spatial patterns of LWD and CWD across different size classes. Within the sample site, trees display a tendency to grow and die in clusters. Biotic factors have a more significant influence on species distribution than abiotic factors.

Diversity patterns of ground beetles and understory vegetation in mature, secondary, and plantation forest regions of temperate northern China.

Plantation and secondary forests form increasingly important components of the global forest cover, but our current knowledge about their potential contribution to biodiversity conservation is limited. We surveyed understory plant and carabid species assemblages at three distinct regions in temperate northeastern China, dominated by mature forest (Changbaishan Nature Reserve, sampled in 2011 and 2012), secondary forest (Dongling Mountain, sampled in 2011 and 2012), and forest plantation habitats (Bashang Plateau, sampled in 2006 and 2007), respectively. The α-diversity of both taxonomic groups was highest in plantation forests of the Bashang Plateau. Beetle α-diversity was lowest, but plant and beetle species turnover peaked in the secondary forests of Dongling Mountain, while habitats in the Changbaishan Nature Reserve showed the lowest turnover rates for both taxa. Changbaishan Nature Reserve harbored the highest proportion of forest specialists. Our results suggest that in temperate regions of northern China, the protected larch plantation forest established over extensive areas might play a considerable role in maintaining a high biodiversity in relation to understory herbaceous plant species and carabid assemblages, which can be seen as indicators of forest disturbance. The high proportion of phytophagous carabids and the rarity of forest specialists reflect the relatively homogenous, immature status of the forest ecosystems on the Bashang Plateau. China's last remaining large old-growth forests like the ones on Changbaishan represent stable, mature ecosystems which require particular conservation attention.

[Relationship between tree-ring chronology of Larix olgensis in Changbai Mountains and the climate change].

The relationship of larch (Larix olgensis) radial growth in Changbai Mountains with climate change was assessed by dendrochronological techniques including correlation functions and single-years analysis. The results showed that larch growth was sensitive to environmental change, and temperature was the primary factor affecting larch growth. The larch growing in high and low elevations had a significantly different response to temperature. In high elevation, larch growth was significant correlated to the mean temperature of June, but in low elevation, it had a more complicated relationship to the environment. Besides the mean temperature of April and May, the temperature of last June and September and the humid index of last September significantly correlated with the larch tree ring-width. Therefore, it was not the same relationship of the same tree species with different environmental gradients.

[Interrelation between plant species diversity and soil environmental factors in bird island of Qinghai Lake].

The study on the relationship between plant species diversity and soil factors in the bird island of Qinghai Lake indicated that this island was a low diversity district, its Shannon-Wienner index and species richness decreased with the increasing soil available K, water soluble salt concentration and pH, and there were significant linear and quadratic correlations between them. Stepwise linear regressions showed that soil available K and water soluble salt were the key factors to estimate Shannon-Wienner index and species richness in this island, respectively, and no correlation was found between species evenness and soil factors.

[Quantitative methodologies for ecotone determination on north slope of Changbai Mountains].

Based on the community important values and present-absent data along elevation gradient on the north slope of Changbai Mountains and using moving split-window techniques, the width and location of vegetation ecotone were discussed in this article. The results showed that the methods of Bray-Curtis Percent Dissimilarity (PD) and Squared Euclidean Distance (SED) introduced in the analysis gave the similar results. Among the methods used in the moving split-window analysis, the SED method was the best in showing the variation of ecotone. According to the results of moving split-window techniques analysis, the ecotone between broad leaved-pine forest and dark conifer forest was gradual type, located in 1120 m a.s.l., spanned 200 m.; that between dark conifer forest and Betula ermanii forest was sharp type, located in 1790 m a.s.l., spanned 50 m; and the timberline was a sharp line, located in 2000 m, spanned 40 m.