Crop characteristics and their temporal change on the Loess Plateau of China

Abstract

Crop characteristics with obvious seasonal changes strongly influence soil loss. The purpose of this study is to measure and analyze the plant characteristics and their seasonal change in the Loess Plateau. A small watershed, Danangou in the Loess Plateau of north China, was selected for this study. Crop characteristics including plant cover, plant height and leaf area index (LAI) were measured every 2 weeks in 1998, 1999 and 2000. In Danangou watershed, half of the lands used as cropland for maize, foxtail millet, pearl millet, potato, buckwheat and soybean. The remainder of the land included wasteland, fallow, shrub, woodland and orchard. The woodlands have high leaf area index (LAI) with the value of 3–7, and high cover of 40–80% in wet year and 30–50% in dry year. For shrub, the maximum height is about 1 m, 1–2 LAI, and cover 50–90% in wet year, 40–50% in dry year. The characteristics of fallow and wasteland were similar with the height of 30–50 cm in wet year and 10–20 cm in dry year. For wasteland, LAI was 1–2 in wet year and 0.3–0.5 in dry year, and cover was 30–40% in wet year and 20–30% in dry year. For fallow, LAI was 0.5–1 in wet year and 0.2–0.5 in dry year, and cover was 10–20% both in wet and dry years. For cropland, LAI, height and coverage changed greatly during the measurement season. For different crops, the range of height, LAI and cover was 0.5–2 m, 0–4.5 and 10–90%, respectively. For non-cropland, cover increased from April, reached maximum in May or June, and remained high until September or October. For croplands, cover increased later and slowly during spring, and reached highest in August. Annual precipitation has large influences on the crop characteristics, especially for crops. The individual rainfall event also has an important effect on crop characteristics. Because cropland comprises of half of the watershed, hence land use in the Danangou is not very good for soil and water conservation.