UNASSIGNED: Global climate change is expected to increase the length of drought periods in many tropical regions. Although large amounts of @entity972 (K) are applied in tropical crops and planted forests, little is known about the interaction between K nutrition and water deficit on the physiological mechanisms governing plant growth. A process-based model (MAESPA) parameterized in a split-plot experiment in Brazil was used to gain insight into the combined effects of @entity14423 and water deficit on absorbed radiation (aPAR), gross primary productivity (GPP), and light-use efficiency for @entity505 assimilation and stem biomass production (LUEC and LUEs ) in @entity38242 plantations. The main-plot factor was the water supply (undisturbed rainfall vs. 37% of throughfall excluded) and the subplot factor was the K supply (with or without 0.45  mol K  m(-2  ) K addition). Mean GPP was 28% lower without K addition over the first 3  years after planting whether throughfall was partly excluded or not. @entity14423 reduced aPAR by 20% and LUEC by 10% over the whole period of growth. With K addition, throughfall exclusion decreased GPP by 25%, resulting from a 21% decrease in LUEC at the end of the study period. The effect of the combination of @entity14423 and water deficit was less severe than the sum of the effects of @entity14423 and water deficit individually, leading to a reduction in stem biomass production, gross primary productivity and LUE similar to @entity14423 on its own. The modeling approach showed that K nutrition and water deficit influenced absorbed radiation essentially through changes in leaf area index and tree height. The changes in gross primary productivity and light-use efficiency were, however, driven by a more complex set of tree parameters, especially those controlling water uptake by roots and leaf photosynthetic capacities.

Measured and modeled interactive effects of @entity972 deficiency and water deficit on gross primary productivity and light-use efficiency in XXXX plantations.

@entity505 :: ('MESH:D002244', 'Chemical') :: ['carbon'] @entity38242 :: ('71139', 'Species') :: ['Eucalyptus grandis'] @entity14423 :: ('MESH:D014813', 'Disease') :: ['K deficiency'] @entity972 :: ('MESH:D011188', 'Chemical') :: ['potassium']
@entity38242 :: (71139,Species) :: ['Eucalyptus grandis']
