การใช้ลักษณะกล้าไม้ยืนต้นผลัดใบเขตร้อนบ่งชี้ความทนทานต่อภาวะแห้งแล้ง

Abstract

Drought is one of the big challenges of forest restoration today. Drought stress affects plant growth and their survival after planting. Plant functional traits play an important role in selecting suitable tree species for forest restoration under extreme environments. The objectives of this study are 1) to examine factors that affect the survival of seedlings in restoration plots, 2) to compare seedling performance under drought experiment, and 3) to explore relationships between functional traits and seedling survival in restoration plots. Nine studied species of deciduous trees were Afzelia xylocarpa, Bombax ceiba, Careya arborea, Chukrasia tabularis, Gmelina arborea, Irvingia malayana, Oroxylum indicum, Phyllanthus emblica and Spondias pinnata. The survival of one-year-old seedlings after planting was influenced by planting sites and species. The species with top five highest survival percentages were C. arborea, S. pinnata, P. emblica, B. ceiba and G. arborea. All nine species, 42 seedings each, were studied under drought experiment. Half seedlings were assigned to water treatment and another half to no water treatment under a randomized complete block design experiment. Wilting stages were evaluated by 0-5 scores, once every 2 days for the first 36 days, and once every 2 weeks till the end of the study (a total of 120 days). A. xylocarpa and B. ceiba were two species that their aboveground parts were still alive (score number 4) at the end of the study. Their leaves were wilting very gradually which represent a drought tolerant strategy. Thirteen functional traits including leaf, root, and stem traits were measured and calculated from seedlings of all studied species. The results showed that when including survival data from both the nursery and the field, studied species could be classified into 4 groups based on their functional traits. The species that showed high survival percentages in the field tend to have high values of root traits; there were root:shoot ratio, root length, and specific root length. These traits contribute to seedling competitive ability to acquire water and essential resources. This study did not find any relationships between studied functional traits in the seedling stage and the survival in the plots. Root traits can be used as a criterion for selecting plant species for forest restoration in drought prone areas. However, drought tolerance alone may not be the only factor towards the success of forest restoration. Restoration practitioners should consider suitable seed source and quality of seedlings, seedling preparation and planting processes, maintenance after planting, and environmental conditions of target planting sites.