Study on the influence of fire and simultaneous bamboo flowering on the regeneration and maintenance of tropical seasonal forests in Thailand

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Seedling survival and growth under contrasting light conditions were experimentally studied in combination with the effects of the drought and fire in a tropical seasonal forest. Seedlings of six tree species, Dipterocarpus alatus, D.turbinatus, Shorea siamensis, Pterocarpus macrocarpus, Xylia xylocarpa var. kerrii, and Sterculia macrophylla, were planted in a gap and under the closed canopy. For each light condition, we applied three treatments : continuous watering during the dry season (W), ground fire during the dry season (F), and no watering/no fire (intact, I). Survival and growth rate were greater in the gap than under the closed canopy for all species, most dramatically for S.siamensis and P.macrocarpus. Dipterocarpus alatus and D.turbinatus had relatively high survival under the closed canopy, and watering during the dry season resulted in significantly higher survival rate for these two species. Watering during the dry season resulted in the higher growth rate for five speci … More es. All seedlings of D.alatus and D.turbinatus, failed to resprout and died after fire. The survival rate during the dry season and after the fire treatment was higher for the seedlings grown in the canopy gap than in the shade for S.siamensis, P.macrocarpus, X.xylocarpa var.kerrii, and S.macrophylla. The seedlings of these species in the canopy gap had higher allocation to the belowground parts than those under the closed canopy, which may support ability to sprout after fire. The light conditions during the rainy season greatly affect seedling survival and resistance to fire during the subsequent dry season, and our results suggest differentiation among species in terms of seedling adaptations to shade, drought and fire.Synchronized flowering of the Gigantchloa albociliata and Cephalostacyum pergracile occurred simultaneously in 1998 and 2001, respectively. Almost all of the clumps died after the flowering, but the suppressed clumps did not flower and survived after the flowering event in case of G.albociliata, After the death of G.albociliata clumps, many clumps of Bambusa tulda emerged and stated to grow quickly. These suggest that these bamboo species can maintain sapling banks under the shade, and shaded individuals may behave differently at the flowering event. The relationship between the simultaneous death of bamboo and the regeneration process of trees and bamboos is not a simple story and need further investigation. Less