Abstract:

We studied 50 years of change in the species composition, abundance, frequency, importance value, population structure and species diversity of secondary subtropical forests in Nanjing Spirit Valley by comparing data collected along the same belt transects in 1951, 1981 and 2002. In general, the amount of stumpage was relatively steady over time, but the spatial heterogeneity increased. The number of under-story seedlings, saplings and shrubs changed significantly, increased from 4 712 in 1951 to 44 130 in 1981, and then decreased to 7 372 in 2002. Both species richness and dominance changed greatly. The number of species decreased from 75 in 1951 to 50 in 1981 and increased to 73 in 2002. The species diversity indices varied but there was no obvious increase or decrease over time. During over 50 years of secondary succession, the dominant species in the masson pine forest, Pinus massoniana, declined over time because of poor regeneration. It was first replaced by intolerant broad-leaved species, such as Pistacia chinensis and Liquidambar formosana, which were then replaced by relatively tolerant species, such as Quercus variabilis. Some evergreen species invaded successfully and were increasing in dominance. Artificial coniferous forests succeeded to coniferous and deciduous mixed forests, then to deciduous forests, and gradually to zonal vegetation —— deciduous and evergreen broad-leaved mixed forests. Communities on good sites were found to have faster successional rates of change.