Abstract
Flowering and fruiting phenology have been little studied in the ever-wet hyperdiverse lowland forests of northwestern equatorial Amazonia. These Neotropical forests are typically called aseasonal with reference to climate because they are ever-wet, and it is often assumed they are also aseasonal with respect to phenology. The physiological limits to plant reproduction imposed by water and light availability are difficult to disentangle in seasonal forests because these variables are often temporally correlated, and both are rarely studied together, challenging our understanding of their relative importance as drivers of reproduction. Here we report on the first long-term study (18 years) of flowering and fruiting phenology in a diverse equatorial forest, Yasuní in eastern Ecuador, and the first to include a full suite of on-site monthly climate data. Using twice monthly censuses of 200 traps and > 1000 species, we determined whether reproduction at Yasuní is seasonal at the community- and species-levels and analyzed the relationships of environmental variables to phenology. We also tested the hypothesis that seasonality in phenology, if present, is driven primarily by irradiance. Both the community- and species-level measures demonstrated strong reproductive seasonality at Yasuní. Flowering peaked in September-November and fruiting peaked in March-April, with a strong annual signal for both phenophases. Irradiance and rainfall were also highly seasonal, even though no month on average experienced drought (a month with < 100 mm rainfall). Flowering was positively correlated with current or near-current irradiance, supporting our hypothesis that the extra energy available during the period of peak irradiance drives seasonality of flowering at Yasuní. As Yasuní is representative of lowland ever-wet equatorial forests of northwestern Amazonia, we expect that reproductive phenology will be strongly seasonal throughout this region. This article is protected by copyright. All rights reserved.
| Original language | English |
|---|---|
| Article number | e4133 |
| Number of pages | 15 |
| Journal | Ecology |
| Volume | 104 |
| Issue number | 9 |
| Early online date | 27 Jun 2023 |
| DOIs | |
| Publication status | Published - 1 Sept 2023 |
Bibliographical note
We thank Pablo Alvia, Alvaro Pérez, Zornitza Aguilar, Paola Barriga, Matt Priest, Caroline Whitefoord, and Gorky Villa for assistance in collecting data or identifying species; Elina Gomez for entry of trap data; Hugo Navarrete, Katya Romoleroux and the QCA herbarium staff, and David Lasso and the ECY staff for help with logistics and needed permitting; Rick Condit, Elizabeth Losos, Robin Foster, and Henrik Balslev for initial encouragement to work within the Yasuní Forest Dynamics Plot; Hugo Romero for initially summarizing the YFDP and SSP weather data sets; Pablo Jarrin for setting up the TEAM weather station, and David Lasso and Carlos Padilla for maintaining that equipment and making the data available; and the Ecuadorian Ministerio del Ambiente for permission to work in Yasuní National Park [No 014-2019-IC-PNY-DPAO/AVS, No 012-2018-IC-PNY593-DPAO/AVS, No 008-2017-IC-PNY-DPAO/AVS, No 012-2016-IC-FAU-FLO-DPAO-PNY, No 594-014-2015-FLO-MAE-DPAO-PNY, and earlier permits]. The Forest Dynamics Plot of Yasuní National Park has been made possible through the generous support of the Pontifical Catholic University of Ecuador (PUCE) funds of donaciones del impuesto a la renta, the Government of Ecuador, the US National Science Foundation, the Andrew W. Mellon Foundation, the Smithsonian Tropical Research Institute, and the University of Aarhus of Denmark. The phenology project began while NCG was at the Natural History Museum, London, with funding (2000–2004) from the Department of Botany (NHM), the Andrew W. Mellon Foundation, British Airways, and the Natural Environment Research Council (GR9/04037). It continued with NCG at Southern Illinois University Carbondale (2005–2023). We thank the Center for Tropical Forest Science for transitional funding (2006–2008, 2017–2018) and the National Science Foundation LTREB program for long-term funding (2006–2020; DEB-0614525, DEB-1122634, DEB-1754632, DEB-1754668).Data Availability Statement
Phenology data and monthly climate data collected at the field site (Garwood et al., 2023) are available in the Environmental Data Initiative (EDI) Data Portal: https://doi.org/10.6073/pasta/5e6cb3d7ff741fd9d21965c4a904bc1f. Meteorological data from other Amazonian regions of Ecuador were obtained from the following, as described in Appendix S1: Section S3.4: The Instituto Nacional de Meteorológico e Hidrológico of Servicio Meteorológico e Hidrológico Nacional del Ecuador (INAMHI); University of East Anglia Climatic Research Unit, et al. (2020); Snodderly et al. (2019). To calculate solar data at our research site, spreadsheets from the Global Monitoring Laboratory, Earth System Research Laboratories of the National Oceanic and Atmospheric Administration (NOAA) were used; spreadsheets were obtained from https://www.esrl.noaa.gov/gmd/grad/solcalc/calcdetails.html.Keywords
- daylength
- flowering
- fruit development
- neotropical
- Phenology
- rainfall
- seasonality
- seed dispersal
- solar irradiance
- synchrony
- tropical forest
- Yasuni National Park