DYNAMICS OF BURIED SEED POPULATION AND SEEDLING COHORTS OF TWO DOMINANT WEEDS IN A HILL AGROECOSYSTEM OF THE HUMID SUBTROPICS OF INDIA

摘要

Dynamics of the buried seeds and plant population of two dominant weeds, viz., Emilia sonchifolia (Linn.) DC. and Richardsonia pilosa HBK were studied in the crop fields of Meghalaya, north-east India during radish and maize cropping and intervening fallow periods. The total buried seed population of R. pilosa was always larger than that of E. sonchifolia, but the germinable fraction was invariably greater in the latter. A major portion (39-41%) of the viable (germinable + dormant) seed population in both weeds was confined to the surface soil layer (0-5 cm). The viable seed population of E. sonchifolia peaked during April, while that of R. pilosa showed two peaks (during August and December). The survival pattern and half-lives of seedling cohorts showed some differences in the two weed species, but both being summer annuals, their populations behaved in a similar manner by showing higher seedling recruitment (K) and survivorship (p) rates in the summer crop (maize) than in the winter crop (radish). However, the density of plants that could attain adulthood was significantly higher in E. sonchifolia than R. pilosa which might have resulted in greater seed input of the former to the soil leading to its greater abundance in the crop fields.