Zhang XiaoXi

The long‐distance migration of Nilaparvata lugens (Stål) (Delphacidae) in China: radar observations of mass return flight in the autumn

Abstract. 1 A case study is presented of the autumn migration of the brown planthopper, Nilaparvata lugens (Stål), in the area of Nanjing in the Peoples Republic of China. The study was made using a high frequency (8 mm wavelength) radar and a net suspended from a kytoon. 2 The observations confirmed that long‐distance return migrations occur in China in mid and late September, with N.lugens being carried on the prevailing north‐easterly wind towards the autumn infestation and overwintering areas of the species. 3 After mass take‐off in the late afternoon or at dusk, the migrants flew for several hours during the evening, often in a dense layer which formed at heights between about 400 and 1000m above ground. These layers often had well‐defined ceilings corresponding to an air temperature of about 16°C. The migration height was above the top of the surface temperature inversion, i.e. the migrants did not fly at the height of the warmest air. 4 The dense layer concentrations overflying the radar were backtracked to source areas up to 240 km away in the north‐east of Jiangsu Province. Planthoppers observed emigrating from the Nanjing area would reach areas in south Anhui Province or north Jiangxi Province if they flew for 12 h. 5 There was a second period of mass take‐off at dawn. Insect layers sometimes formed but did not last longer than 1–2h. 6 The present results were strikingly different from those previously observed in the dry season in the Philippines, where migratory flight durations were largely confined to periods of about 30min at dusk and dawn. 7 Our observations are discussed in relation to the equator‐wards return migrations undertaken in autumn by other insect species, and the importance of these migrations for the maintenance of long‐flying genotypes in the overwintering populations is considered.

KARYOTYPE POLYMORPHISM IN DIFFERENT GEOGRAPHIC POPULATIONS OF GREEN PEACH APHID MYZUS PERSICAE (SULZER) IN CHINA

Abstract  This paper deals with the karyotype of green peach aphid, Myzus persicae (Sulzer), with three different life cycles in different regions of China. The results showed that four types of karyotype were found in the natural populations of red form and brown form aphids. Four types of karyotype are as follows: 2n = 12 with autosomes 1, 3 translocated (T1–3); 3n = 18 normal triploid; 3n = 18 with T1–3 translocation; and 2n = 11.

Dissimilation of soil humus in forest with pure stands and its relationship with other bio-chemical properties in the semi-arid windy region of the Loess Plateau, China

Abstract Dissimilation of soil humus in 7 typical forests with pure stands in the semiarid windy region of the Loess Plateau in China was investigated. In addition, its relationships with other bio-chemical characteristics were assessed by canonical correlation analysis. The results was as follows: (1) Pinus tabuliformis Carrière forest had the lowest humus content and the worst stability among 7 forests with pure stands; Populus simonii Carrière forest had low humus content and worse stability; Robinia pseudoacacia L. forest had moderate humus content but the best stability; Salix matsudana Koidz. forest had moderate humus content and bad stability; Hippophae rhamnoides L. forest had high humus content and the best stability; Caragana microphylla Lam. forest had high humus content and moderate stability; Amorpha fruticosa L. forest had the highest humus content and benign stability; (2) Large microbial biomass and sufficient available P would accelerate the formation of humic acid and fulvic acid, respectively. High available N, P and Fe contents and high urease and protease activity were conducive to increase the humus stability. The particularity of community environment and litter properties of pure stands were identified as the key reasons for the humus dissimilation, thus mixed-reformation or establishing ground vegetation would be feasible ways to improve humus properties in forest with pure stands.

Using forage litter to improve soil degradation of pure Betula platyphylla forest in the Loess Plateau, China

Abstract The long-term growth of pure forest is an important issue that affects stability and sustainable development of ecosystem, while using forage litter as fertilizer or directly establishing tree-grass complex vegetation may be the most effective prevention way. This study took the artificial pure forests of Betula platyphylla, which were widely distributed in the Loess Plateau of China, as the object and conducted a 120-day decomposition incubation experiment of forest humus soil mixed with seven common leguminous forage litters to study the effects of forage litters in controlling the degradation of soil biological and chemical properties of pure forests. The results showed that: by adding forage litter to the soil of pure B. platyphylla forest, litters of Lespedeza bicolor and Onobrychis viciaefolia improved the soil quality obviously, followed by Astragalus adsurgens and Melilotus officinalis, while Medicago sativa lead to obvious deterioration, followed by Vicia villosa and Coronilla varia.

RAPD-PCR DETECTION OF DNA POLYMORPHISM OF COTTON APHID

Abstract  The RAPDPCR technique was used to determine the DNA polymorphism of the aphid Aphis gossypii(Glover) collected from different host plants and in different seasons. Three primers were selected from 20 primers and used for cluster analysis based on the data of Neis genetic distance (D). The results showed that the aphids on Chinese prickly ash differentiated obviously from the aphids on the other four host plants at DNA level. The seasonal population of cotton aphid might be clustered into three groups, i.e. the spring and autumn yellow colored aphids, the spring and autumn green colored aphids and the yellow dwarf form aphid in summer.