Effects of drought and fire on seedling survival and growth under contrasting light conditions in a seasonal tropical forest

Abstract

Question: How do tree seedlings differ in their responses to drought and fire under contrasting light conditions in a tropical seasonal forest? Location: Mae Klong Watershed Research Station, 100–900 m a.s.l, Kanchanaburi Province, western Thailand. Method: Seedlings of six trees, 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 (1) continuous watering during the dry season (W); (2) ground fire during the dry season (F); (3) no watering/no fire (intact, I). Seedling survival and growth were followed. Results: 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 rates for these two species. Watering during the dry season resulted in higher growth rates for five species. All seedlings of D. alatus and D. turbinatus failed to re‐sprout and died after fire. The survival rates during the dry season and after the fire treatment were 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 below‐ground parts than those under the closed canopy, which may support the ability to sprout after fire. Conclusions: The light conditions during the rainy season greatly affect seedling survival and resistance to fire during the subsequent dry season. Our results suggest differentiation among species in terms of seedling adaptations to shade, drought and fire.

Carbon Cycling in Teak Plantations in Comparison with Seasonally Dry Tropical Forests in Thailand

“…In terms of the recruitment of trees, forest fires and drought stress would control the survival rates of tree seedlings and seed germination as well (Marod et al, 2002). In addition, shading by bamboo leaves during the rainy season influences the survival rate of seedlings (Marod et al, 2004). Similar findings showing that abundance in terms of seedlings and species had declined under bamboo in the MDF were reported in the Loei province of Thailand (Larpkern et al, 2011).…”

Growth Performances of Three Indigenous Tree Species Planted in a Mature Acacia mangium Plantation with Different Canopy Openness under a Tropical Monsoon Climate

“…Although the DBH distribution pattern of X. xylocarpa var. kerrii was not clear, the survival rate and height growth of seedlings were higher in gap sites than under the canopy of a mixed deciduous forest 21 . Seedlings of X. xylocarpa var.…”

“…Seedlings of X. xylocarpa var. kerrii were found to be rather tolerant of drought and fire 21 , although seed production and seedling recruitment were rare in the forest 20 . Rapid growth in a Different letters to the right of the numerical value indicate significant difference at 5% level: a, b, c, d and e among plots in each species, and x, y, and z among species in each plot.…”

Seedling root morphology and biomass allocation of 62 tropical tree species in relation to drought‐ and shade‐tolerance

“…1995; Poorter & Hayashida‐Oliver 2000; Gilbert 2001). As seedling mortality rates increase exponentially with a decrease in rainfall (Marod et al . 2004; Poorter 2005), seedling size at the onset of the dry season is therefore an important, though often neglected, characteristic of species’ differentiation in response to drought.…”