The development of chemically recyclable polymers presents the most appealing solution to address the plastics' end-of-use problem. Despite the recent advancements, it is highly desirable to develop chemically recyclable polymers from commercially available monomers to avoid the costly and time-consuming commercialization. In this contribution, we achieve the controlled ring-opening polymerization (ROP) of biosourced δ-caprolactone (δCL) using strong base/urea binary catalysts. The obtained PδCL is capable of chemical recycling to δCL in an almost quantitative yield by thermolysis. Sequential ROP of δCL and L-lactide (L-LA) affords well-defined PLLA-b-PδCL-b-PLLA triblock copolymers, which behave as thermoplastic elastomers with excellent elastic recovery, tensile strength and ultimate elongation. The upcycling of PLLA-b-PδCL-b-PLLA to recover ethyl lactate and δCL with high yields is achieved by refluxing with ethanol and then distillation under reduced pressure.

Aboveground biomass is a key indicator of a grassland ecosystem. Accurate estimation from remote sensing is important for understanding the response of grasslands to climate change and disturbance at a large scale. However, the precision of remote sensing inversion is limited by a lack in the ground truth and scale mismatch with satellite data. In this study, we first tried to establish a grassland aboveground biomass estimation model at 1 m 2 quadrat scale by conducting synchronous experiments of unmanned aerial vehicle (UAV) and field measurement in three different grassland ecosystems. Two flight modes (the new QUADRAT mode and the commonly used MOSAIC mode) were used to generate point clouds for further processing. Canopy height metrics of each quadrat were then calculated using the canopy height model (CHM). Correlation analysis showed that the mean of the canopy height model (CHM_mean) had a significant linear relationship with field height (R 2 = 0.90, root mean square error (RMSE) = 19.79 cm, rRMSE = 16.5%, p < 0.001) and a logarithmic relationship with field aboveground biomass (R 2 = 0.89, RMSE = 91.48 g/m 2 , rRMSE = 16.11%, p < 0.001). We concluded our study by conducting a preliminary application of estimation of the aboveground biomass at a plot scale by jointly using UAV and the constructed 1 m 2 quadrat scale estimation model. Our results confirmed that UAV could be used to collect large quantities of ground truths and bridge the scales between ground truth and remote sensing pixels, which were helpful in improving the accuracy of remote sensing inversion of grassland aboveground biomass.

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It is highly desirable to develop chemically recyclable polymers to address the challenge in establishing a sustainable circular polymer economy. Despite the mass production and widespread applications, there are limited reported examples for the polyurethanes capable of chemical recycling to monomers with high efficiency and purity. In this contribution, we report the “living”/controlled ring-opening polymerization (ROP) of bio-renewable δ-caprolactone (δCL) at room temperature in bulk using an organobase in combination with urea as a catalyst. The telechelic PδCL diol precursor with well-defined terminal groups can be prepared using catalyst loading as low as 0.05 mol %. A one-pot strategy by cascade ROP of δCL and step-growth polymerization of PδCL diol precursors with diisocyanate under solvent-free conditions produced thermoplastic polyurethane elastomers with excellent elastic recovery, tensile strength, ultimate elongation, and low residue strain. Remarkably, the polyurethanes can be chemically recycled to recover δCL with high purity and excellent yield (∼99%) by simple thermolysis.

Aims Quantitatively assess the foraging and burrowing effects of plateau pikas (Ochotona curzoniae, hereafter pikas) on vegetation biomass and soil organic carbon at plot scale. Methods Combining field surveys and aerial photographing, we investigated pikas density, vegetation biomass, soil organic carbon and total nitrogen at quadrat-scale in 82 grassland sites of the Qinghai-Tibetan Plateau. We then upscaled these variables to plot-scale and eventually quantified pikas' foraging and burrowing effects on aboveground biomass and soil organic carbon.Results Pikas have a wide distribution, with densities ranging from 40.29 to 71.40 ha −1 . Under this density level, pikas consume approximate 21% to 40% of the total vegetation biomass, while their burrowing activity causes less than 1% vegetation biomass reduction. However, pikas burrowing transfers 1 to 5 T ha −1 of soil to the ground surface, which contains approximate 20 to 70 kg ha −1 of soil organic carbon and 2 to 5 kg ha −1 of total nitrogen. Conclusions Vegetation biomass is susceptible to the foraging influence of pikas. Pikas burrowing activity has a potential impact on soil organic carbon loss and thus vegetation growth. These results are conducive to

Plateau pika (Ochotona curzoniae, hereafter pika) is considered to exert a profound impact on vegetation species diversity of alpine grasslands. Great efforts have been made at mound or quadrat scales; nevertheless, there is still controversy about the effect of pika. It is vital to monitor vegetation species composition in natural heterogeneous ecosystems at a large scale to accurately evaluate the real role of pika. In this study, we performed field survey at 55 alpine grassland sites across the Shule River Basin using combined methods of aerial photographing using an unmanned aerial vehicle (UAV) and traditional ground measurement. Based on our UAV operation system, Fragmentation Monitoring and Analysis with aerial Photography (FragMAP), aerial images were acquired. Plot-scale vegetation species were visually identified, and total pika burrow exits were automatically retrieved using the self-developed image processing software. We found that there were significant linear relationships between the vegetation species diversity indexes obtained by these two methods. Additionally, the total number of identified species by the UAV method was 71, which was higher than the Quadrat method recognition, with the quantity of 63. Our results indicate that the UAV was suitable for long-term repeated monitoring vegetation species composition of multiple alpine grasslands at plot scale. With the merits of UAV, it confirmed that pika’s disturbance belonged to the medium level, with the density ranging from 30.17 to 65.53 ha−1. Under this density level, pika had a positive effect on vegetation species diversity, particularly for the species richness of sedge and forb. These findings conclude that the UAV was an efficient and economic tool for species monitoring to reveal the role of pika in the alpine grasslands.

Salinity adversely affects plant growth and production. Oat is a moderately salt-tolerant crop and can contribute to improving saline soil. The physiological and molecular responses of the oat plant to long-term salinity were studied. After a 16-day salt treatment (150 mmol LNaCl in Hoagland's solution), photosynthetic rate, maximum photosystem II photochemical efficiency, and actual efficiency of photosystem II decreased. The activities of superoxide dismutase, peroxidase, and catalase significantly increased. We also investigated the protein profiles of oat leaves in response to salinity and detected 30 reproducible protein spots by two-dimensional gel electrophoresis that were differentially abundant. Specifically, one protein was up-regulated and 29 proteins were down-regulated compared with the control. These 29 proteins were identified using MALDI-TOF mass spectrometry, and 19 corresponding genes were further investigated by quantitative real-time PCR. These proteins were involved in four types of biological processes: photosynthesis, carbohydrate metabolism and energy, protein biosynthesis, and folding and detoxification. This study indicates that the lower levels of Calvin cycle-related proteins, 50S ribosomal protein L10 and adenosine-triphosphate regulation-related proteins, and the high levels of antioxidant enzymes play important roles in the response of oat to long-term salinity stress.

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