Population dynamics of Paratylenchus nanus in soil under pasture: 2. Biotic factors and population modelling

Abstract

AbstractSeasonal and monthly sampling of a Paratylenchus nanus population showed that trends in biomass were similar to those for abundance. A Population Age Index (proportional contribution of each life stage multiplied by stage biomass) showed population age increased from a minimum in spring to maximum in winter. From mid-spring to mid-summer, population age was greater in 0-10 than 10-20 cm depth; this may have been due to a greater proportion of juveniles developing over this period at the deeper depth. The populations at 10-20 cm deep included a greater proportion of fourth stage juveniles than those at 0-10 cm. This may reflect the smaller root resource at 10-20 cm depth limiting population development. Monthly sampling of patches of high vs low P.nanus density indicated that such patches retain their densities relative to each other in most months. Evidence is presented for density-dependence in the P. nanus population at 0-10 cm and density-independence at 10-20 cm depth. Multiple regression models were fitted, taking into account all factors (abiotic and biotic) which were significantly associated with P.nanus abundance, and results are discussed to highlight areas still requiring investigation before a complete model of the population dynamics of this nematode can be achieved.