Interspecific variation in leaf water use associated with drought tolerance in four emergent dipterocarp species of a tropical rain forest in Borneo

Abstract

By use of tree-tower and canopy-crane systems we studied variations in the water use, including transpiration, stomatal conductance, and leaf water potential, of the uppermost sun-exposed canopy leaves of four emergent dipterocarp species in an aseasonal tropical rain forest in Sarawak, Malaysia. Midday depression in stomatal conductance and leaf water potential was observed in all the species studied. Interspecific differences were clearly observed in the maxima of transpiration rates and stomatal conductance and the minima of leaf water potential among the four dipterocarp species. These interspecific variations were closely related to wood density and to factors affecting ecological patterns of distribution. Specifically, Shorea parvifolia and S. smithiana, both of which have a relatively low wood density for Dipterocarpaceae and are found on clay-rich soil, had a high transpiration rate in the daytime but had a large midday depression and a low leaf water potential. In contrast, Dryobalanops aromatica, which has a high wood density and is found in sandy soil areas, consumed less water even during the daytime.Dipterocarpus pachyphyllus, which has a high wood density and is found on clay-rich soil, stood intermediate between Shorea and D. aromatica in leaf water use. The two Shorea species had higher mortality than the others during the severe drought associated with El Niño in 1998, so daily pattern of leaf water use in each dipterocarp species might be correlated with its susceptibility to unusual drought events.

Relationship between leaf flushing phenology and defensive traits of canopy trees of five dipterocarp species in a tropical rain forest

“…Lamarre et al (2014) suggested that leaf flushing phenology in tropical rain forest trees might be closely related to soil resource availability; some species growing in poor soil under frequent drought stress might be favored to produce a large number of leaves all at once, which might represent lower cost than to produce leaves continuously. However, it seems that the species studied did not reflect any soil resource availability for their leaf flushing phenology, because they bore little relation to soil texture; species distributed over sandy soil, such as DrA, SB and DG, showed various leaf flushing patterns, and the same goes for those distributed over clay soil, such as DP and SF (Itoh 1995, Hirai et al 1997, Hiromi et al 2012, Lee et al 2002, Ashton 2004.…”

“…All the species are evergreen and dominate the canopy and emergent layers in the study sites (Table 1). DG, DrA and SB are distributed over sandy soil and, DP and SF over clay soil (Itoh 1995, Hirai et al 1997, Hiromi et al 2012, Lee et al 2002, Ashton 2004 (Table 1). But the distribution of these dipterocarp species is unrelated to soil pH (Lee et al 2002).…”

Impact of Severe Drought during the Strong 2015/2016 El Nino on the Phenology and Survival of Secondary Dry Dipterocarp Species in Western Thailand

“…Species with high wood density have a different strategy to cope with severe drought compared to stem succulent species, as they have a thicker cell wall and/or narrower conduits providing a high resistance to xylem embolism (air bubbles breaking the water column) [43]. For instance, tree species with high wood density were able to survive the severe drought event induced by the strong 1997-1998 El Niño whereas high mortality rate was observed in lower wood density species in Bornean tropical rainforest [62]. Furthermore, the size of DDF species has no effect on wood density, except S. obtusa Wall.…”

Comparison of Wood Density and Water Content Between Dry Evergreen and Dry Deciduous Forest Trees in Central Cambodia

“…We also conducted paired t-tests to determine the differences in wood traits of five tree species with high wood density were able to survive the severe drought event during 1997-1998 El Niño as compared with lower wood density species in Bornean tropical rainforest (Bebber 2000, Hiromi et al 2012. Further large datasets on community-level wood density and water content from broad climate zones in tropical Southeast Asia are needed to clarify the precise relationship between wood traits and environmental conditions, especially for precipitation and dry spell length.…”

“…The traits of stem woody parts, namely wood density and water content, have a strong relationship with their functional traits, such as drought tolerance, crown architecture, growth rate, survival, and photosynthesis, especially in tropical forests (Bucci et al 2004, Hiromi et al 2012, Inoue et al 2015, Ishida et al 2008, Kenzo et al 2011, Markesteijn et al 2011, Martin et al 2013, Santiago et al 2004. For example, trees with low wood density exhibit a faster growth rate compared with trees of high wood density, whereas trees with high wood density usually have a high survival rate due to their stronger resistance to physical stress, pathogens, and pest attacks (Curran et al 2008, King et al 2005, 2006, Kitajima 1994.…”