[Effects of plant hedgerow on population dynamics of wheat aphid and its natural enemies].

This paper studied the effects of planting different kinds of plant hedgerow (Amorpha fruticosa, Vetiveria zizanioides, Eulaliopsis binata, and Medicago sativa) on the population dynamics of wheat aphid and its natural enemies in the hillside wheat fields in Ziyang City of Sichuan Province, Southwest China. On the 20 degrees hillside, A. fruticosa hedgerow inhibited the occurrence of wheat aphid in the wheat field significantly, and the parasitoid densities were equal to or significantly lower than those in the wheat field with V. zizanioides hedgerow. On the 12 degrees hillside, M. sativa and E. binata hedgerows delayed the peak time of wheat aphid occurrence, and E. binata hedgerow suppressed the wheat aphid population density significantly. In the wheat field with M. sativa hedgerow, the parasitoid densities were significantly higher than those with no hedgerow. An equal or significantly higher ladybird density was observed in the field with M. sativa hedgerow. The olfactory responses showed that E. binata volatiles had repellent effect on both Sitobion avenae and Rhopalosiphum padi, but attracted a spider species of oxyopidae. M. sativa volatiles attracted S. avenae, whereas neither M. sativa nor E. binata volatiles caused obvious behavior response of ladybird adults. Therefore, planting A. fruticosa and E. binata as the hedgerows in hillside wheat fields could not only prevent the soil erosion from seasonal rainfall, but also benefit the control of pest insects.

[Land cover classification of Four Lakes Region in Hubei Province based on MODIS and ENVISAT data].

Based on the differences of back scattering coefficient in ENVISAT ASAR data, a classification was made on the towns, waters, and vegetation-covered areas in the Four Lakes Region of Hubei Province. According to the local cropping systems and phenological characteristics in the region, and by using the discrepancies of the MODIS-NDVI index from late April to early May, the vegetation-covered areas were classified into croplands and non-croplands. The classification results based on the above-mentioned procedure was verified by the classification results based on the ETM data with high spatial resolution. Based on the DEM data, the non-croplands were categorized into forest land and bottomland; and based on the discrepancies of mean NDVI index per month, the crops were identified as mid rice, late rice, and cotton, and the croplands were identified as paddy field and upland field. The land cover classification based on the MODIS data with low spatial resolution was basically consistent with that based on the ETM data with high spatial resolution, and the total error rate was about 13.15% when the classification results based on ETM data were taken as the standard. The utilization of the above-mentioned procedures for large scale land cover classification and mapping could make the fast tracking of regional land cover classification.

[Anti-erosion effect of hedgerows in hillside croplands of Danjiangkou based on the evaluation with water erosion prediction project (WEPP) model].

Based on the data of field experiments on the hillside croplands of Danjiangkou, Hubei Province of China, the input files of crop characters, management measures, slope gradient and length, and soil properties for running WEPP model (Hillslope version) were established. Combining with the local weather data, a simulation study with the model was made on the runoff and soil loss of the croplands protected by four kinds of hedgerows (Amorpha fruticosa, Lonicera japonica, Hemerocallis fulva, and Poa sphondylodes) in Danjiangkou area. The resulted showed that WEPP model could accurately simulate the anti-erosion effect of hedgerows in hillside farmlands in the study area. Using this model not only reduced test number, but also saved time and effort, being able to provide scientific basis for the popularization and application of hedgerows. Among the four hedgerows, Amorpha fruticosa had the best anti-erosion effect. According to the simulation, the optimal planting density of A. fruticosa hedgerows in the farmlands was 1 m x 15 m at slope gradient 5 degrees, 1 m x 10 m at slope gradient 15 degrees, and 1 m x 3 m at slope gradient 25 degrees.