Comparative study on tree seedling growth rate and diversity between a natural forest and a restored forest area in Mae Rim District, Chiang Mai

ABSTRACT: In 1967, Thailand had forest cover as high as 53.22 percent of the country's land area, but in 2021 the forest area was reduced to 31.68 percent, of which 63.99 percent was forested in the North. The forest area in Chiang Mai province was accounted for 69.29 percent. For Mae Rim District, from 2001 to 2020, 46 hectares of forest loss were caused by the exploitation of forests in agro-industry, changing the utilization of large areas, and small-scale shifting cultivation. These deforested areas can be regenerated naturally but can take a long time. Forest restoration is another way to accelerate the recovery of nature that has been destroyed. The objectives of this study were: 1) to compare the diversity and similarity of tree seedlings in the natural forest and the restored forest, and 2) to compare the growth of tree seedlings in natural forests and restored forests. This research consisted of 3 study areas in Mae Rim District, Chiang Mai Province. Data were collected using a Circular Sampling Unit (CSU) of 10 CSUs per plot with a diameter of 6 m. The results were recorded from seedlings with a height of 10 cm to 100 cm. Seedlings found between March and December 2021 were tagged to identify and record the growth.

The results showed that 310 seedlings from 30 species were found in the Mon Jam natural forest plot. While for the restored forest plots, 223 seedlings from 29 species and 223 seedlings from 36 species were found in the Mon Jam restored forest, and Mon Long restored forest plots, respectively. The number of seedlings species in the Mon Long restored plot was as high as 36 species because it is a plot that has been restored with some of the original trees remaining in the area. Additionally, the area has fewer weeds; thus, seedlings and seeds are not impeded in germination and growth. When measuring the Shannon's Diversity Index of all three areas, the Mon Long forest restored area has the highest diversity, equal to 2.858, indicating that the Mon Long restoration area has higher diversity than the other two areas. The similarity index of seedlings between the three areas shows that the Mon Jam natural forest and the Mon Long restored forest area have the highest similarity index, equal to 50.746. Because the physical characteristics of the Mon Long restored area is more similar to the Mon Jam natural forest than the Mon Jam restored forest. Therefore, the value of the similarity index is greater. Four types of seedlings can be found in all three areas; Gluta obovata Craib , Litsea glutinosa (Lour.) C.B. Rob., Phoebe lanceolata, and Syzgium fruticosum DC. It can be seen that restoring forests in areas where their physical characteristics are very close to natural forest areas will also increase diversity and similarity to natural forests.