Growth and Understory Vegetation Characters of Mixed Plantation of Pinus massoniana and P. elliottii × caribaea and Pure P. massoniana Plantation

In March 2006, 1-year bare-root seedlings of different provenances of Pinus massoniana and P. elliottii × caribaea were planted under three group on the same slope in State-owned Tianhongling Forest Farm, Cangwu, Guangxi. Stand of pure P. massoniana (Tongmian provenance, TM), pure P. massoniana (Tugong provenance, TG), mixed TM and P. elliottii × caribaea (MIX) formed 3 groups. In 2018, quadrat investigations showed that height growth of MIX was significantly higher than that of two pure stands (P < 0.05). There was no significant difference of individual tree volume between MIX and TM, but obviously higher than that of TG. Growth of P. massoniana was better than that of P. elliottii × caribaea in the MIX. Shrub layer diversity under MIX had higher values than that under pure stands.