The degraded forests may increase their natural forest recovery if they were protected from the land utilizing, however, the success differed among the period of times and forest restoration patterns. This study aimed to clarify the forest structure and species composition between the forest restoration and natural forest. A 1-ha permanent plot,100 m ? 100 m, was established in each area, natural deciduous dipterocarp forest (DDF), natural succession of degraded DDF, restoration forest by Eucalytus camaldulensis and Eucalytus camaldulensis plantation, respectively. All trees with diameter at breast height (DBH) larger than 2 cm were tagged, measured and species identified during October to November 2020
The results showed that highest species rich was found in the Eucalytus camaldulensis plantation (40 species) and followed by natural succession of degraded DDF, DDF and forest restoration by Eucalytus camaldulensis, 28, 27 and 22 species, respectively. The diversity index based on Shannon-Weiner also showed the same tendency, however, low diversity was detected in all sites (H/= 1.69-2.55). Shrub and shrubby tree species had high established and became dominance species in the Eucalytus camaldulensis plantation, for instant, Microcos tomentosa, Rothmannia eucodon, and Morinda coreia. Contrasting within the DDF and forest restoration by Eucalytus camaldulensis, the native species mostly dominance such as Shorea obtusa, Pterocarpus macrocarpus, Dipterocarpus obtusifolius, Gluta usitata, and Irvingia malayana. Tree basal areas also showed the strongly different among the sites. The highest was found in the Eucalytus camaldulensis plantation (134.34 m2.ha-1). While, the similarity index showed that the similarity of forest restoration by Eucalytus camaldulensis and natural succession of degraded DDF into the natural DDF was almost the same, 55.81 and 50.98, respectively. Indicating that it may no need to plant Eucalytus camaldulensis, only allowed the natural process. However, large amount of basal area or large tree of Eucalytus camaldulensis may useful for further utilization.