Black soils in the Northeast Plain of China are characterized by high organic carbon (C) density and storage, which can influence C sequestration in local cropland ecosystems. Using GIS, this study analyzed the temporal and spatial distribution and variation of cropland organic C density and storage in the arable layer (0-20 cm) of the major black soil regions in China's Northeast Plain (specifically across the study region of Hailun, Shuangcheng and Gongzhuling counties) over the past 30 years. The results indicate an overall downward trend in soil organic C (SOC) density (SOCd, mean decrease of 0.64 kg m-2) and storage (SOCs, decrease of 4.65 Tg )*1 for the major black soil regions tested during the study period. The mean decrease in SOCd for Hailun, Shuangcheng and Gongzhuling counties was 0.68 kg m-2, 0.18 kg m-2 and 1.05 kg m-2, respectively, with total SOC decreases of 2.30 Tg, 0.49 Tg and 1.86 Tg, respectively. SOCd decreased to a greater extent during the first twenty years in Hailun and Shuangcheng relative to Gongzhuling. Moreover, SOCd tended to stabilize and then slightly increase during the last ten years. There was a downward trend in SOCd and SOCs over the past 30 years for almost all soil types, but the most serious decline in SOCs was observed in black soils, which account for 57.92% of the cropland soil area in all study regions and which lost up to 2.91 Tg of SOC. Therefore, the major black soil region in Northeast China was presenting a C resource trend over the past 20-30 years.

Sichuan basin, situated in the west of China, is the fourth biggest basin in China. In order to describe a systematic study of the cry2-type genes resources from Bacillus thuringiensis strains of Sichuan basin, a total of 791 Bacillus thuringiensis strains have been screened from 2650 soil samples in different ecological regions. The method of PCR-restriction fragment length polymorphism (PCR-RFLP) was used to identify the type of cry2 genes. The results showed that 322 Bacillus thuringiensis strains harbored cry2-type genes and four different RFLP patterns were found. The combination of cry2Aa/cry2Ab genes was the most frequent (90.4%), followed by cry2Aa (6.8%) and cry2Ab alone (2.5%), and only one novel type of cry2 gene was cloned from one isolate (JF19-2). The full-length of this novel gene was obtained by the method of thermal asymmetric interlaced PCR (Tail-PCR), which was designated as cry2Ag1 (GenBank No. ACH91610) by the Bt Pesticide Crystal Protein Nomenclature Committee. In addition, the result of scanning electron microscopic (SEM) observation showed that these strains had erose, spherical, bipyramidal, and square crystal. And the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that these strains harbored about one to three major proteins. These strains exhibited a wide range of insecticidal spectrum toxic to Aedes aegypti (Diptera) and Pieris rapae Linnaeus, 1758 (Lepidoptera). Particularly, JF19-2 contained cry2Ag gene had the highest insecticidal activity. All these researches mentioned above revealed the diversity and particularity of cry2-type gene resources from Bacillus thuringiensis strains in Sichuan basin.