Effects of nitrogen inputs and mowing on the abundance and species richness of herbivorous insects in a meadow steppe.

To reveal the effects of nitrogen (N) inputs and mowing on the abundance and richness of insect community in meadow steppe, we investigated the abundance and diversity of herbivorous insects under four treatments in Inner Mongolia meadow steppe in August 2022, including control, N addition, mowing, and combined N addition and mowing. At a long-term control experimental platform, we collected insects using the vacuum sampling method. The results showed that N addition significantly increased the abundance of herbivorous insects, and mowing significantly decreased the abundance of herbivorous insects. Nitrogen addition significantly increased insect abundance in unmown condition but not in the mown condition. The responses of insect abundance at the community level to N addition were mainly driven by the dominant groups, Cicadellidae and Lygaeidae, which was affected by the abundance of Gramineae species. In contrast, their responses to mowing were the opposite. Both N addition and mowing did not affect the diversity of herbivorous insects. Our results indicated that the responses of herbivorous insect abundance to N inputs and mowing were directly regulated by food resources. With increasing food resource availability, the abundance but not the diversity of herbivorous insects increased, with stronger responses of dominant groups than subordinate ones.

Stamp-Like Energy Harvester and Programmable Information Encrypted Display Based on Fully Printable Thermoelectric Devices.

Thermoelectric (TE) devices exhibit considerable application potential in Internet of Things and personal health monitoring systems. However, TE self-powered devices are expensive and their fabrication process is complex. Therefore, large-scale preparation of the TE devices remains challenging. In this work, simple screen-printing technology is used to fabricate a user-friendly and high-performance paper-based TE device, which can be used in both stamp-like paper-based TE generators and infrared displays. When used as a paper-based TE generator, an output power of 940.8 µW is achieved with a temperature difference of 40 K. The programmable infrared pattern based on the TE array display could be used to realize encryption and anti-counterfeiting properties. Moreover, a visual extraction algorithm is used to develop a mobile application for processing and decoding the infrared quick response code information. These findings offer an exciting approach to using paper-based TEGs in applications such as energy harvesting devices, optical encryption, anti-counterfeiting, and dynamic infrared display.

Extreme drought exacerbates plant nitrogen­phosphorus imbalance in nitrogen enriched grassland.

The nitrogen­phosphorus (N-P) imbalance induced by N enrichment has received increasing concerns, because N:P ratios play a critical role in driving many fundamental ecological processes. Given the simultaneous occurrence of different global change drivers, it is important to understand whether and how would such N-induced N-P imbalance would be mediated by other global change factors. We examined the interactive effects of N addition (10 g N m-2 yr-1) and extreme drought (-66 % rainfall during the growing season) on species- and community-level N:P ratios in both green and senesced leaves in a temperate grassland of northern China. Extreme drought did not alter soil available N:P ratio under ambient N conditions, but increased that under N enriched conditions. Further, extreme drought did not alter the community-level N:P in both green and senesced leaves under ambient N conditions but significantly enhanced that under N enriched conditions. The drought-induced species turnover made a significant positive contribution to the changes in the community-level N:P ratio under N enriched conditions, but not under ambient N conditions. Our results suggest that the N-induced ecosystem N-P imbalance would be exacerbated by extreme drought event, the frequency of which is predicted to increase across global drylands. Such N-P imbalance would have consequences on litter decomposition, nutrient cycling, and the structures of above- and below-ground food webs. Our findings highlighted the complexity in predicting ecosystem N-P imbalance given the interactions between different global change drivers.

Effects of extreme drought on plant nutrient uptake and resorption in rhizomatous vs bunchgrass-dominated grasslands.

Both the dominance and the mass ratio hypotheses predict that plant internal nutrient cycling in ecosystems is determined by the dominant species within plant communities. We tested this hypothesis under conditions of extreme drought by assessing plant nutrient (N, P and K) uptake and resorption in response to experimentally imposed precipitation reductions in two semiarid grasslands of northern China. These two communities shared similar environmental conditions, but had different dominant species-one was dominated by a rhizomatous grass (Leymus chinensis) and the other by a bunchgrass (Stipa grandis). Results showed that responses of N to drought differed between the two communities with drought decreasing green leaf N concentration and resorption in the community dominated by the rhizomatous grass, but not in the bunchgrass-dominated community. In contrast, negative effects of drought on green leaf P and K concentrations and their resorption efficiencies were consistent across the two communities. Additionally, in each community, the effects of extreme drought on soil N, P and K supply did not change synchronously with that on green leaf N, P and K concentrations, and senesced leaf N, P and K concentrations showed no response to extreme drought. Consistent with the dominance/mass ratio hypothesis, our findings suggest that differences in dominant species and their growth form (i.e., rhizomatous vs bunch grass) play an important nutrient-specific role in mediating plant internal nutrient cycling across communities within a single region.