Seasonal and intra-canopy fates of absorbed photons across microclimatic gradients in Central Amazonian forests

We assessed seasonal and intra-canopy variations in leaf energy partitioning in central Amazonian forests with extensive in-canopy sampling and pulse amplitude modulated (PAM) chlorophyll fluorescence measurements. In order to cover seasonal variation of leaf microenvironments and energy partitioning, we compared measurements between dry (Jul.-Dec.) and wet (Jan.-Mar.) seasons in the TNF K67 site. The dataset includes the pathways of photon utilization for photochemistry (ΦPSII), heat dissipation (ΦNPQ), and fluorescence re-emission (ΦNO). Dry season field campaigns were conducted in 2019, 2021, and 2022, and a wet season campaign was conducted in 2023. We conducted pulse amplitude modulated (PAM) chlorophyll-a fluorescence measurements and sampling of microenvironmental variation at the leaf level with the MultispeQ (V2.0).

Methods
The research was conducted at the Tapajós National Forest (TNF) site, located near km 67 (K67, 02°51′S, 54°58′W) of the Santarém-Cuiabá highway, south of the city of Santarém (Pará, Brazil). It is an evergreen tropical forest on a well-drained infertile oxisol plateau, with a mean canopy height of approximately 40 to 45 m and a sub-dominant layer ranging from 15 to 30 m (with a mean of 28 m) (Hutyra et al., 2007; Hunter et al., 2015). 

Individual leaf-level sampling approach employed advanced tree climbing techniques to access different canopy levels and measure in situ leaf-chlorophyll fluorescence with the MultispeQ.