Temporal stability of productivity is associated with complementarity and competitive intensities in intercropping.

Year-to-year stability in crop production is a crucial aspect of feeding a growing global population. Evidence from natural ecosystems shows that increasing plant diversity generally increases the temporal stability of productivity; however, we have little knowledge of the mechanisms by which diversity affects stability. In fact, understanding the drivers of stability is a major knowledge gap in our understanding of biodiversity and ecosystem function in general. We varied resource inputs into crop monocultures and intercropping of maize/pea and maize/rapeseed for 3 years in field experiments to create a wide range of values for temporal stability, complementarity effects, selection effects, competition, and facilitation. We correlated whole-system temporal stability in productivity with these values and the stability of competitively subordinate species and competitively dominant species in the intercrops. We then used structural equation modeling (SEM), which combines complex path models with latent variables, to estimate how interspecific interactions for water, nitrogen, and phosphorus affected the relationships between stability and these values. Intercropping treatments did not increase stability, but the wide range of stability created by our experiments allowed us to explore the relationship of many factors with stability. Complementarity correlated positively with the temporal stability of grain yield and aboveground biomass, suggesting that either facilitative interactions or niche partitioning shifted over time in ways that promoted stability. Furthermore, the temporal stability of total productivity of intercropping relied most on the stability of more productive species. However, facilitation tested by relative interaction index independently did not correlate with stability, but the temporal stability of the whole system increased as the competitive effects of competitively dominant species (pea and rapeseed) on competitively subordinate species (maize) decreased and was highest when these competitive effects were virtually zero. SEM indicated that as competition for soil nitrogen from competitively dominant species on competitively subordinate species decreased, the overall temporal stability of whole-system aboveground biomass increased. This stability then led to greater stability in grain production. Our findings indicate that complex shifts in complementarity and competitive intensities are likely to be key mechanisms that maintain temporal stability in species-diverse agriculture and, potentially, in natural systems.

A neglected transport of plastic debris to cities from farmland in remote arid regions.

Although microplastics have been investigated in terrestrial environments, the occurrence and transport of microplastics in semiarid regions with serious wind erosion are still limited. We investigated plastic debris, including macroplastics (>5 mm) and microplastics (50 µm to 5 mm), from twenty semiarid farmlands and then developed a mass flux model to calculate the quantities of plastic debris transport by wind erosion. Finally, the spatial extent of microplastic deposition was estimated. The average abundance of macroplastics increased with duration of mulching film use, whereas the abundance of microplastics did not change significantly (p > 0.05). Moreover, the highest abundance of microplastics among samples was from the farmland using greenhouse, which suggests that wind erosion played an essential role in retention of plastic debris. Besides, the enrichment ratio (ER) which depends on the shape of microplastics is identified to be a key indicator of the mass flux model. The results showed that 6.91-38.11 kg/ha of plastic debris was released by wind in the 25th year after film application, with 6.14 n/m2 of microplastics settling in February in Xi'an, which is 690 km away from the source.

[Effects of no-tillage sowing with crop stubbles on seeding emergence and yield of spring wheat in Hexi Oasis Irrigated Area, Northwest China]. / ç•™èŒ¬å è€•æ’­ç§å¯¹æ²³è¥¿ç»¿æ´²çŒåŒºæ˜¥å°éº¦å‡ºè‹—å’Œäº§é‡çš„å½±å“.

We examined the effects of long-term no-tillage sowing with crop stubbles on seedling emergence quality and yield of spring wheat under the three typical spring wheat planting modes of single wheat, wheat-corn intercropping and wheat-soybean intercropping in a long-term field experiment in Hexi oasis irrigated area, aiming to provide theoretical support for the efficient and sustai-nable production of spring wheat. The results showed that, compared with traditional tillage, no-tillage sowing with crop stubbles significantly decreased seedling emergence rate and emergence evenness of spring wheat in wheat-corn intercropping and wheat-soybean intercropping by 3.3%-8.6%, 9.6%-20.5%, 2.9%-8.8%, and 10.7%-61.7%, respectively. Emergence evenness was significantly increased by 14.9% in 2019, while seedling emergence rate was significantly decreased by 4.2% in 2020 under the mode of single wheat compared with traditional tillage. Seedling uniformity of spring wheat seedling stage were reduced under the three typical planting modes, including single wheat, wheat-corn intercropping and wheat-soybean intercropping. Spike number of spring wheat were equal to that of traditional tillage at harvest under the three planting modes of no-tillage sowing with crop stubbles, and the differences were not significant. Effects of seedling emergence rate of spring wheat on yield was weakened by increasing grain number per spike and 1000-grain weight of spring wheat under the three planting modes. Grain yield was significantly increased by 10.3%-12.9% (single wheat), 10.5%-11.9% (wheat-corn intercropping), and 10.3%-22.5% (wheat-soybean intercropping) at harvest, respectively. Our results indicated that no-tillage sowing with crop stubbles was the feasible tillage mode in the production process of spring wheat in Hexi oasis irrigation area with extremely serious farmland wind erosion degradation.

The Theoretical Model, Method, and Applications of Scattering Photon Burst Counting Based on an Objective Scanning Technique.

Scattering photon burst counting (SPBC) is a single-particle detection method, which is based on measuring scattering photon bursting of single nanoparticles through a detection volume of <1 fL. Although SPBC has been used for bioassays and analysis of nanoparticles, it is necessary to establish its theoretical model and develop a new detection mode in order to further enhance its sensitivity and enlarge its application fields. In this paper, we proposed a theoretical model for the confocal SPBC method and developed a novel SPBC detection mode using the fast objective scanning technique. The computer simulations and experiments documented that this model well describes the relation between photon counts and experimental parameters (such as nanoparticle concentration and diameter, temperature, and viscosity). Based on this model, we developed a novel SPBC detection mode by using the fast objective scanning technique. Compared to the current confocal SPBC method, the sensitivity of this new method was significantly increased due to the significantly increased photon counts per sampling time, the linear detection range is from 0.9 to 90 pM, and the limit of detection is reduced to 40 fM for 30 nm gold nanoparticles. Furthermore, this new method was successfully applied to determine the enzyme activity of caspase-3 and evaluate the inhibition effectiveness of some inhibitors.

Magnetic Graphene Dispersive Solid-Phase Extraction for the Determination of Phthalic Acid Esters in Flavoring Essences by Gas Chromatography Tandem Mass Spectrometry.

In the present study, a sensitive, efficient and repeatable method for the simultaneous extraction and determination of 13 types of phthalic acid esters (PAEs) in flavoring essence samples using magnetic graphene solid-phase extraction coupled with gas chromatography tandem mass spectrometry was developed. Due to the unique structure of magnetic graphene, it has several advantages, such as large surface area and fast separation ability. This unique structure not only provided strong magnetic responsiveness for the separation but also prevented the self-aggregation of graphene. The large delocalized p-electron system of graphene can form strong π-stacking interactions with the benzene ring. Thus, graphene may be also a good candidate adsorbent for the adsorption of benzenoid-form compounds. Several magnetic soild-phase extraction parameters, such as elution solvents, amounts of sorbents, enrichment time and desorption time were optimized. The optimized procedures for this method were performed by ultrasonication using ethyl acetate as elution solvent for 5 min. Under the optimal conditions, the developed method provided spiked recoveries of 75.0-105.3% with relative standard deviations of ~5.6% and limits of detection were 0.011-0.091 mg/kg. Good linear relationships were observed with the coefficient of determination (R2) > 0.993 for all the analytes. Finally, the validated method was successfully applied to the analysis of PAEs in real samples.

[Long-Term Different Fertilizations Changed the Chemical and Spectrum Characteristics of DOM of the Irrigation-Desert Soil in North-Western China].

By using Ultraviolet-visible Spectrometry, Fourier Transform Infrared Spectrometer and Elemental Analyzer, spectrum and chemical characteristics of soil DOM affected by long-term different fertilizations were investigated in irrigation-desert soil in North-western China based on an experiment started from 1988. Four different fertilization treatments were included, i. e., organic fertilizer (OF), green manure (GM), chemical fertilizer (CF) and a control of no fertilization (CK). The results showed that fertilization could increase the contents of DOM. Compared to CK, the treatments of OF, GM, CF increased the dissolved organic carbon (DOC) by 37%, 29%, 16%; increased the dissolved nitrogen (DON) by 334%, 257%, 182%; increased the total carbohydrate (TCs) by 90%, 25%, 2%; and increased the total organic acids (TOAs) by 195%, 116%, 58%; respectively. Furthermore, DOC, DON, TCs, and TOAs in the OF treatment were significantly higher than those in CK, they were also significantly higher in the GM and CF treatments except for TCs. The ultraviolet-visible analysis showed that fertilizations enhanced the SUVA(254), SUVA(260), SUVA(272) and SUVA(280) of DOM, indicating that fertilizations increased the aromatic and hydrophobic percentage, humification degree, and average molecular weight, and thus resulting in more stability of DOM. Same trends were showed for all the 4 ultraviolet spectrum absorption values in different fertilizations, i. e., the strongest effect was found in the OF treatment, and then was the GM treatment and CF treatment successively. From the results by the Fourier Transform Infrared Spectrometry, the characteristic peak of aromatic in the OF treatment was observed shifting from 1 625 to 1 649 cm(-1), which was close to the characteristic peak of humin, suggesting that the aromaticity of DOM in the OF treatment was higher than the other treatments. The characteristic peaks of C-O at 1 260-1 000 cm(-1) belonging to sugar, alcohol, and carboxylic acid were highest in the GM treatment, showing that the green manure could increase rich oxygen radicals. The highest characteristic peaks of N-H at 3 559, 3 419 and 1 456 cm(-1) were observed in the CF treatment, indicating that the chemical fertilizer could increase amine substances. The contents of C, O and N in the OF, GM, CF treatments were also increased respectively according to the elemental analysis.