Effects of three forest restoration approaches on plant diversity in red soil region,southern China

Plant diversity has important ecosystem function in forest ecosystem.Forest restoration approaches can impact plant diversity,especially the understory plant diversity.We studied the floristic characteristics,plant community structure and diversity of three forest restoration approaches in red soil region of southern China,which included introduced species slash pine(Pinus elliottii) plantations,native species Masson pine(Pinus massoniana) plantations and natural secondary forests.For each forest restoration approach,a total of 15 independent plots were surveyed.On each plot,three 10 m × 10 m subplots of area were surveyed for trees′ abundance,height and diameter at breast height.Within each tree subplot,one to two shrub quadrates(5 m × 5 m) and one to three herb quadrates(1 m × 1 m) were surveyed for plant species abundance.A total of 127 tree subplots,238 shrub subplots and 357 herb subplots were effectively surveyed for plant community structure.The results showed that:(1) 155 species(which belong to 160 genera and 86 families),137 species(which belong to 97 genera,59 families) and 226 species(which belong to 160 genera,86 families) were identified in slash pine plantations,Masson pine plantations and natural secondary forests,respectively.Dominant species in these 3 forest restoration approaches varied in tree,shrub and herb layers.Dominant species in Masson pine plantations were more similar to that of natural secondary forests compared with that of slash pine plantations.In tree layer,the dominant plant in slash pine plantations was only P.elliotti. Similarly,the dominant plant in Masson pine plantations was only P.massoniana. The dominant species in natural secondary forests belong to Fagaceae,Lauraceae and Theaceae.In shrub layer,the dominant plants were Verbenaceae,Gramineae,Hamamelidaceae,Theaceae and Euphorbiaceae for slash pine plantations;Hamamelidaceae,Verbenaceae,Theaceae,Fagaceae and Myrtaceae for Masson pine plantations;Fagaceae,Hamamelidaceae,Theaceae,Rosaceae,Rubiaceae and Myrtaceae for natural secondary forest.In herb layer,the dominant plants were Gramineae,Gleicheniaceae and Thelypteridaceae for slash pine plantations;Gleicheniaceae,Hamamelidaceae,and Dryopteridaceae for Masson pine plantations;Myrsinaceae,Gramineae,Dryopteridaceae,Cyperaceae and Rubiaceae for natural secondary forests;(2) natural secondary forests had more flora types(21 flora types) than Masson pine plantations(16 flora types) and slash pine plantations(18 flora types),and had higher ratio of temperate flora.Natural secondary forests had more unique flora types in comparison with Masson pine plantations and slash pine plantations;(3) forest restoration approach had significant effects on forest community diversity.In tree,shrub and herb layer,natural secondary forest had higher species richness and Shannon-Wiener diversity index than Masson pine plantations and slash pine plantations.There was no significant difference in these indexes between slash pine plantations and Masson pine plantations;(4) multivariate analysis showed that these three reforestation approaches differed significantly in their species composition.Moreover,compared with slash pine plantations,the community composition of Masson pine plantations was more similar to the natural secondary forests.In conclusion,natural restoration is an important forest restoration approach since it was better than artificial plantations of P.massoniana and P.elliottii,yet the native species of P.massoniana plantations were superior to the introduced species of P.elliottii plantations in maintaining plant community structure.