Effects of Stand Regeneration Management Regimes and Age on Genetic Structure of Quercus aquifolioides (Sclerophyllous Oak) in Southwestern China

As a representative relict forest type, the sclerophyllous oak (Quercus aquifolioides Rehd. et Wils.) forests in the Himalayas-Hengduanshan Mountains of China have been either nearly completely destroyed or heavily fragmented, mostly due to the long-lasting overexploitation by local human population. To evaluate the effect of current silvicultural treatments on regeneration of sclerophyllous oak, we compared inter simple sequence repeats, measures of genetic variation of this species regenerating in three types of stands: natural old-growth oak forest, clearcut spruce plantation, and clearcut naturally regenerated stands in the Miyaluo area, western Sichuan Province of China. Results showed that populations of Q. aquifolioides in the old-growth stands displayed the highest level of genetic diversity, whereas populations in the clearcut naturally regenerated stands had the lowest. In addition, we found that populations in the older spruce plantations (e.g., stands ≥50 years old) were genetically more diverse than those in the younger sites. These findings had the following immediate implications: forest clearcuts had significantly reduced genetic variability within populations of Q. aquifolioides; artificial reforestation of spruce after clearcut could promote the recovery of genetic diversity in Q. aquifolioides, especially in the older stands; and severe human and livestock disturbances hindered the recovery of genetic diversity of Q. aquifolioides in the naturally regenerated stands. We recommend active thinning in spruce plantations (at approximately age 30-40 years) via selective logging at times of rapid height growth and crown closure to promote multistoried stand structures and canopy gaps suitable for the survival and growth of Q. aquifolioides. Finally, we recommend strict management control in the naturally regenerated stands to limit the utilities of these stands by humans and their livestock to facilitate the recovery of Q. aquifolioides genetic diversity.