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Effects of 12 Years of Water Deficit on Tropical Rainforest Trees

Paper Reviewed
Rowland, L., Lobo-do-Vale, R.L., Christoffersen, B.O., Melem, E.A., Kruijt, B., Vasconcelos, S.S., Domingues, T., Bnks, O.J., Oliveira, A.A.R., Metcalfe, D., Da Costa, A.C.L., Mencuccini, M. and Meir, P. 2015. After more than a decade of soil moisture deficit, tropical rainforest trees maintain photosynthetic capacity, despite increased leaf respiration. Global Change Biology 21: 4662-4672.

Noting that "one of the key changes that tropical rainforests may experience under future climate change scenarios is reduced soil moisture availability," Rowland et al. (2015) studied how both leaf photosynthesis and leaf dark respiration might acclimate after more than a dozen years of experimental soil moisture deficit, which they did via a through-fall water-exclusion experiment they conducted in an eastern Amazonian rainforest.

In a rather amazing finding, the 13 scientists -- hailing from 8 different countries -- found that "experimentally drought-stressed trees and taxa maintain the same maximum leaf photosynthetic capacity as trees in corresponding control forest, independent of their susceptibility to drought-induced mortality." This ability, they hypothesized, was due to the fact (as they described it) that "photosynthetic capacity is maintained across all treatments and taxa to take advantage of short-lived periods of high moisture availability, when stomatal conductance and photosynthesis can increase rapidly, potentially compensating for reduced assimilate supply at other times."

In light of these observations, Rowland et al. concluded that since "even after a severe and prolonged reduction in soil moisture availability" the trees they had studied were "able to maintain the same photosynthetic capacity, despite increasing leaf dark respiration," such may also be the case with other trees of the tropics.

Posted 30 March 2016