Effects of different regeneration modes on understory plant functional group in Eucalyptus plantations
We evaluated the relationships between composition, distribution and regeneration modes of understory plant functional groups and environmental factors, through the combination methods of field investigation and analyzed experimental to elucidate the changing rules of understory plant functional group in two different regenerated Eucalyptus plantations and the related influencing factors. Our results indicated that the species richness of understory plant functional groups in forest generated after five years increased but not significantly ( P>0.05) compared to control plots ( cut-over land) except for forbs. The 5-year forest regeneration caused increasing of relative abundance of vines and ferns, but that of grass was significantly decreased ( P<0.05). The relative coverage had a great resemblance to relative abundance, which exhibited increasing in woody plants, vines and ferns in 5-year regeneration forest, but decreasing in grass ( P<0.05). Principal component analysis ( PCA) showed that the composition and distribution of understory plant functional groups significantly changed in sprouting regeneration forest and planting regeneration forest compared to control plots. Redundancy analysis ( RDA) revealed that canopy light transmittance, slope aspect, soil porosity and N/P ratios were key factors in regulating plant functional groups in Eucalyptus plantations, and the accumulative effects explained more than 75.0% of total variations in understory plant functional groups. The sequencing mode analysis suggested that canopy light transmittance was the most significant factor in affecting understory plant functional groups in Eucalyptus plantations. We found in short-term studies that sprouting and planting regeneration had limited effects on the understory plant functional groups in Eucalyptus plantations, and which may be caused by similar canopy structure and soil physicochemical properties.