Standardized sampling from many sites worldwide was used to address an important ecological problem.

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Solar steam generation through heat localization is a new approach to efficiently utilize solar energy. Nanocomposites with noble metals and other porous materials have been employed to generate solar vapor at a high light intensity. However, large-scale applications of the nanocomposites based on noble metals are restricted due to their high cost, complex preparation, and low recycling stability. Herein, we report a simple method toward fabricating graphene aerogel (GA) from graphene oxides only by photoreduction, which is for the first time used to harvest solar energy. GA can not only convert almost the entire incident solar light to heat energy but can also self-float on the surface of water and pump the interface water forming a constant water steam. Solar steam generation efficiencies of 53.6 ± 2.5% and 82.7 ± 2.5% are achieved at light intensities of 1 and 10 kW m–2, respectively. Furthermore, this efficiency is still kept at a high value, and the morphology of GA is hardly broken after 10 cycles of testing. This technology of steam generation through efficiently harvesting solar energy is highly promising for sterilization of waste and seawater desalination.

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Summary1. Large variation in the size of individuals is a ubiquitous feature of natural plant populations. While the role of competition in generating this variation has been studied extensively, the potential effects of positive interactions among plants, which are common in high-stress environments, have not been investigated. 2. Using an individual-based 'zone-of-influence' model, we investigate the effects of competition, abiotic stress and facilitation on size inequality in plant monocultures. In the model, stress reduces the growth rate of plants, and facilitation ameliorates the effects of stress. Both facilitation and competition occur in overlapping zones of influence. We tested some of the model's predictions with a field experiment using the clonal grass Elymus nutans in an alpine meadow. 3. Facilitation increased the size inequality of model populations when there was no density-dependent mortality. This effect decreased with density as competition overwhelmed facilitation. The lowest size inequality was found at intermediate densities both with the model and in the field. 4. When density-dependent mortality was included in the model, stress delayed its onset and reduced its rate by reducing growth rates, so the number of survivors at any point in time was higher under harsh than under more benign conditions. Facilitation increased size inequality during selfthinning. 5. Synthesis. Our results demonstrate that facilitation interacts with abiotic stress and competition to influence the degree of size inequality in plant populations. Facilitation increased size inequality at low to intermediate densities and during self-thinning.

In grassland ecosystems, N and P fertilization often increase plant productivity, but there is no concensus if fertilization affects soil C fractions. We tested effects of N, P and N+P fertilization at 5, 10, 15 g m−2 yr−1 (N5, N10, N15, P5, P10, P15, N5P5, N10P10, and N15P15) compared to unfertilized control on soil C, soil microbial biomass and functional diversity at the 0–20 cm and 20–40 cm depth in an alpine meadow after 5 years of continuous fertilization. Fertilization increased total aboveground biomass of community and grass but decreased legume and forb biomass compared to no fertilization. All fertilization treatments decreased the C:N ratios of legumes and roots compared to control, however fertilization at rates of 5 and 15 g m−2 yr−1 decreased the C:N ratios of the grasses. Compared to the control, soil microbial biomass C increased in N5, N10, P5, and P10 in 0–20 cm, and increased in N10 and P5 while decreased in other treatments in 20–40 cm. Most of the fertilization treatments decreased the respiratory quotient (qCO2) in 0–20 cm but increased qCO2 in 20–40 cm. Fertilization increased soil microbial functional diversity (except N15) but decreased cumulative C mineralization (except in N15 in 0–20 cm and N5 in 20–40 cm). Soil organic C (SOC) decreased in P5 and P15 in 0–20 cm and for most of the fertilization treatments (except N15P15) in 20–40 cm. Overall, these results suggested that soils will not be a C sink (except N15P15). Nitrogen and phosphorus fertilization may lower the SOC pool by altering the plant biomass composition, especially the C:N ratios of different plant functional groups, and modifying C substrate utilization patterns of soil microbial communities. The N+P fertilization at 15 g m−2 yr−1 may be used in increasing plant aboveground biomass and soil C accumulation under these meadows.

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