Plant communities in the Loess Plateau’s artificial afforestation forests play an important role in fragile ecosystem restoration. Therefore, the composition, coverage, biomass, diversity, and similarity of grassland plant communities in different years of artificial afforestation in cultivated land were investigated. The effects of years of artificial afforestation on grassland plant community succession in the Loess Plateau were also investigated. The results showed that as the number of years of artificial afforestation increased, grassland plant communities grew from scratch, constantly optimizing community components, improving community coverage, and increasing aboveground biomass. The community diversity index and similarity coefficient gradually approached those of a 10-year abandoned community that had recovered naturally. After 6 years of artificial afforestation, the dominant species of the grassland plant community changed from Agropyron cristatum to Kobresia myosuroides, and the main associated species changed from Compositae and Gramineae to Compositae, Gramineae, Rosaceae, and Leguminosae. The α-diversity index accelerated restoration, the richness index and diversity index increased, and the dominant index decreased. The evenness index had no significant difference from CK. The β-diversity index decreased as the number of years of afforestation increased. The similarity coefficient between CK and grassland plant communities in various lands changed from medium dissimilarity to medium similarity at 6 years of afforestation. According to the analysis of various indicators of the grassland plant community, the grassland plant community had a positive succession within 10 years of artificial afforestation on the cultivated land of the Loess Plateau, and the threshold of the years from slow to fast was 6 years.

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Botanical pesticide is highly recommended for integrated pest management (IPM), due to its merits such as environmental friendliness, safe to non-target organisms, operators, animals, and food consumers. The experiment was conducted to determine the lethal and sub-lethal effects of allyl isothiocyanate (AITC) on eggs, third instar larvae, pupae, and females and males of Bradysia impatiens Johannsen (B. impatiens). Different concentrations of AITC under ambient CO2 by the conical flask sealed fumigation method were used for the experiment. The results showed that there was a significant linear relationship between different concentrations of AITC and the toxicity regression equation of B. impatiens. The sub-lethal concentrations of AITC had significant effects on the larval stage, pupal stage, pupation rate, pupal weight, adult emergence rate, and oviposition. The pupation rate, pupal weight, and adult emergency rate were significantly (p < 0.05) affected by AITC fumigation. The pupation rate was the lowest after fumigation treatment of AITC at LC50 (36.67%), followed by LC25 (41.94%), compared with the CK (81.39%). Female longevity was significantly (p < 0.05) shortened by fumigation at LC25 (1.75 d) and LC50 (1.64 d), compared with that of CK (2.94 d). Male longevity was shorter at LC25 (1.56 d) than at LC50 (1.25 d) and had no significant difference between these two treatments. The fumigation efficiency of AITC was significantly increased under high CO2 condition. Furthermore, detoxification enzyme activities and antioxidant enzyme activities were accumulated under high CO2 condition. The fumigation method in the application of AITC can be useful in areas where B. impatiens is a major concern.