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Summary 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 structuredLAIalong axes of both canopy height and light environments.Upper canopyLAIincreased during the dry season, whereas lower canopyLAIdecreased. The low canopy decrease was driven by highly illuminated leaves of smaller trees in gaps. By contrast, understoryLAIincreased 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.
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Measured and Predicted Turbulent Kinetic Energy in Flow Through Emergent Vegetation With Real Plant Morphology
Abstract Velocity and forces on individual plants were measured within an emergent canopy with real plant morphology and used to develop predictions for the vertical profiles of velocity and turbulent kinetic energy (TKE). Two common plant species,Typha latifoliaandRotala indica, with distinctive morphology, were considered.Typhahas leaves bundled at the base, andRotalahas leaves distributed over the length of the central stem. Compared to conditions with a bare bed and the same velocity, theTKEwithin both canopies was enhanced. For theTyphacanopy, for which the frontal area increased with distance from the bed, the velocity, integral length‐scale, andTKEall decreased with distance from the bed. For theRotala, which had a vertically uniform distribution of biomass, the velocity, integral length‐scale, andTKEwere also vertically uniform. A turbulence model previously developed for random arrays of rigid cylinders was modified to predict both the vertical distribution and the channel‐average ofTKEby defining the relationship between the integral length‐scale and plant morphology. The velocity profile can also be predicted from the plant morphology. Combining with the new turbulence model, theTKEprofile was predicted from the channel‐average velocity and plant frontal area.
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- Award ID(s):
- 1854564
- PAR ID:
- 10452365
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Water Resources Research
- Volume:
- 56
- Issue:
- 12
- ISSN:
- 0043-1397
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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