title: Allocation trade-offs dominate the response of tropical forest growth to seasonal and interannual drought.
abstract: What determines the seasonal and interannual variation of growth rates in trees in a tropical forest? We explore this question with a novel four-year high-temporal-resolution data set of carbon allocation from two forest plots in the Bolivian Amazon. The forests show strong seasonal variation in tree wood growth rates, which are largely explained by shifts in carbon allocation, and not by shifts in total productivity. At the deeper soil plot, there was a clear seasonal trade-off between wood and canopy NPP, while the shallower soils plot showed a contrasting seasonal trade-off between wood and fine roots. Although a strong 2010 drought reduced photosynthesis, NPP remained constant and increased in the six-month period following the drought, which indicates usage of significant nonstructural carbohydrate stores. Following the drought, carbon allocation increased initially towards the canopy, and then in the following year, allocation increased towards fine-root production. Had we only measured woody growth at these sites and inferred total NPP, we would have misinterpreted both the seasonal and interannual responses. In many tropical forest ecosystems, we propose that changing tree growth rates are more likely to reflect shifts in allocation rather than changes in overall productivity. Only a whole NPP allocation perspective can correctly interpret the relationship between changes in growth and changes in productivity.
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Doughty
authors.forename: Yadvinder
authors.initials: Y
authors.lastname: Malhi
authors.forename: Alejandro
authors.initials: A
authors.lastname: Araujo-Murakami
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Metcalfe
authors.forename: Javier E
authors.initials: JE
authors.lastname: Silva-Espejo
authors.forename: Luzmila
authors.initials: L
authors.lastname: Arroyo
authors.forename: Juan P
authors.initials: JP
authors.lastname: Heredia
authors.forename: Erwin
authors.initials: E
authors.lastname: Pardo-Toledo
authors.forename: Luz M
authors.initials: LM
authors.lastname: Mendizabal
authors.forename: Victor D
authors.initials: VD
authors.lastname: Rojas-Landivar
authors.forename: Meison
authors.initials: M
authors.lastname: Vega-Martinez
authors.forename: Marcio
authors.initials: M
authors.lastname: Flores-Valencia
authors.forename: Rebeca
authors.initials: R
authors.lastname: Sibler-Rivero
authors.forename: Luzmarina
authors.initials: L
authors.lastname: Moreno-Vare
authors.forename: Laura Jessica
authors.initials: LJ
authors.lastname: Viscarra
authors.forename: Tamara
authors.initials: T
authors.lastname: Chuviru-Castro
authors.forename: Marilin
authors.initials: M
authors.lastname: Osinaga-Becerra
authors.forename: Roxana
authors.initials: R
authors.lastname: Ledezma
mesh_terms: D000818:Animals; D001838:Bolivia; D055864:Droughts; D017753:Ecosystem; D004784:Environmental Monitoring; D008954:Models, Biological; D011891:Rain; D012621:Seasons; D013997:Time Factors; D014197:Trees; D014329:Tropical Climate