Processes of Secondary Succession on Fallow Land in Relation to Management Systems

Abstract

Processes of secondary succession were studied in a field where several management practices were applied in terms of cultivation methods and the amount of fertilizer applied for 5 years from 1984 to 1988.
The results obtained are as follows:
1. In the untreated field where tilling was carried out in the spring of 1984 and thereafter no more tilling was applied, herbaceous annuals, such as Digitaria ciliaris, Polygonum lapathifolium and Chenopodium album, dominated for 2 years. After the 3rd year following the final tilling, herbaceous perennials, such as Solidago altissima, Phytolacca americana, Pueraria lobata and Robinia pseudo-acacia, dominated while the number of annuals and small herbaceous perennials decreased. During the 5 year period of investigation, the proportion of the number of annual species to that of all the species which emerged decreased rapidly while the degree of succession (DS) increased markedly.
2. In the field where dead plant parts grown in the previous year were removed every spring, the composition of the plant species was similar to that in the untreated field, while the proportion of the number of herbaceous annuals was generally higher than that in the untreated field and the degree of succession lower.
3. In the field where dead plant parts were removed and at the same time the soil was cultivated through rotary tilling every spring, invasion and establishment of perennials were prevented, and herbaceous annuals dominated even in the 5th year after the onset of the investigation.
4. A high degree of succession was observed in the field where the amount of fertilizer applied was low. The ecological characteristics of the various weed species were unaffected by the amount of fertilizer applied.