Weed Diversity of Arable Land in China

The purpose of this paper is to describe the basic status of the weed diversity of China. Weed diversity of the arable land in China could be outlined at the following three levels：the diversities of weed species, weed occurrence and infestation and weed vegetation. At the first level of diversities, there are about 1,486 weed species belonging to 105 families in the arable land of China. According to the occurrence-density and distribution-areas, these weeds are divided into four groups：37 species of the worst weeds, 105 species of the worst regional weeds, the others of the common weeds and the secondary weeds. According to the season and types of crop fields of weed occurrence, all weeds could roughly be classified into the paddy weeds, the weeds of summer crop fields, the weeds of autumn dry-land crops, and the weeds of orchard, tea plantation and tropical fruit plantation, which belong to the second level of diversity. Finally, weed flora and vegetation of the arable land in China might be regionalized into the five regions of weed flora and vegetation as follows：The northeastern humid temperate Echinochloa-Avena fatua-Setaria weed region; the northern warm temperate Digitaria-Descurainia-Galium weed region; the northern and western arid to semi-arid Avena fatua-Chenopodium weed region; the south central subtropical Echinochloa- Alopecurus-Digitaria weed region; the southern tropical Echinochloa-Digitaria weed region. The following principles are the main bases of the regionalization：1) weed community complex indicating combination of different real and potential weed communities in time and space; 2) the dominant species of weed communities and other main compositions of weed flora and communities; 3) biological characters and life forms of the main weeds; 4) the natural conditions of agriculture and cropping system in the region