TY - JOUR

T1 - Seasonal and drought-related changes in leaf area profiles depend on height and light environment in an Amazon forest

AU - Smith, Marielle

AU - Stark, Scott C.

AU - Taylor, Tyeen C.

AU - Ferreira, Mauricio L.

AU - de Oliveira, Eronaldo

AU - Restrepo-Coupe, Natalia

AU - Chen, Shuli

AU - Woodcock, Tara

AU - Dos Santos, Darlisson Bentes

AU - Alves, Luciano F.

AU - Figueira, Michela

AU - Camargo, Plínio Barbosa de

AU - de Oliveira, Raimundo C.

AU - Aragao, Luiz E.O.C.

AU - Falk, Donald A.

AU - McMahon, Sean M.

AU - Huxman, Travis E.

AU - Saleska, Scott R.

PY - 2019/5/1

Y1 - 2019/5/1

N2 - Seasonal dynamics in the vertical distribution of leaf area index (LAI) may impact the seasonality of forest productivity in Amazonian forests. However, until recently, fine-scale observations critical to revealing ecological mechanisms underlying these changes have been lacking.To investigate fine-scale variation in leaf area with seasonality and drought we conducted monthly ground-based LiDAR surveys over 4 yr at an Amazon forest site. We analysed temporal changes in vertically structured LAI along axes of both canopy height and light environments.Upper canopy LAI increased during the dry season, whereas lower canopy LAI decreased. The low canopy decrease was driven by highly illuminated leaves of smaller trees in gaps. By contrast, understory LAI increased concurrently with the upper canopy. Hence, tree phenological strategies were stratified by height and light environments. Trends were amplified during a 2015–2016 severe El Niño drought.Leaf area low in the canopy exhibited behaviour consistent with water limitation. Leaf loss from short trees in high light during drought may be associated with strategies to tolerate limited access to deep soil water and stressful leaf environments. Vertically and environmentally structured phenological processes suggest a critical role of canopy structural heterogeneity in seasonal changes in Amazon ecosystem function.

AB - Seasonal dynamics in the vertical distribution of leaf area index (LAI) may impact the seasonality of forest productivity in Amazonian forests. However, until recently, fine-scale observations critical to revealing ecological mechanisms underlying these changes have been lacking.To investigate fine-scale variation in leaf area with seasonality and drought we conducted monthly ground-based LiDAR surveys over 4 yr at an Amazon forest site. We analysed temporal changes in vertically structured LAI along axes of both canopy height and light environments.Upper canopy LAI increased during the dry season, whereas lower canopy LAI decreased. The low canopy decrease was driven by highly illuminated leaves of smaller trees in gaps. By contrast, understory LAI increased concurrently with the upper canopy. Hence, tree phenological strategies were stratified by height and light environments. Trends were amplified during a 2015–2016 severe El Niño drought.Leaf area low in the canopy exhibited behaviour consistent with water limitation. Leaf loss from short trees in high light during drought may be associated with strategies to tolerate limited access to deep soil water and stressful leaf environments. Vertically and environmentally structured phenological processes suggest a critical role of canopy structural heterogeneity in seasonal changes in Amazon ecosystem function.

U2 - 10.1111/nph.15726

DO - 10.1111/nph.15726

M3 - Article

VL - 222

SP - 1284

EP - 1297

JO - New Phytologist

JF - New Phytologist

SN - 0028-646X

IS - 3

ER -