Population changes of early successional forest species after shifting cultivation in Northwestern Vietnam

Abstract

The population changes of early successional forest species, Wendlandia paniculata, Schima wallichii, Camellia tsaii, and Lithocarpus ducampii, were described and analyzed in a chronosequence of 1–30 year-old secondary forests representing regrowth after shifting cultivation in northwestern Vietnam, utilizing 51 temporary plots for stem census. Another five temporary plots were used for stem census in surrounding old-growth forest for comparison. In the first year after land abandonment, seedling stem density (H < 2 m) was 65,800/ha, increasing to 161,200/ha by third year, then sharply decreasing to 2,500/ha in 21–30 year-old forests. The sapling stratum (H ≥ 2 m and DBH < 5 cm) started to be recruited in the fifth year, increasing to reach a peak density of 4,530 stems/ha at year ten, then decreased to 580 stems/ha at year 21–30. The tree stratum (DBH ≥ 5 cm) achieved the maximum density of 600 stems/ha at year ten. Meanwhile, the density of all strata in the old-growth forest was 2,980 stems/ha. Sprouts played an important role, accounting for 34% at the first year then increased gradually to 73% at year 21–30. Total basal area attained a peak at 5.43 m2/ha at year ten; it was 4.9 m2/ha in the old-growth forest. These four species played an important role in providing ecological services for recruitment of other species during the first 10 years of fallow stand development, which increased to 35 species in 21–30 year-old secondary forest.