Vertical profiles of leaf photosynthesis and leaf traits and soil nutrients in two tropical rainforests in French Guiana before and after a 3-year nitrogen and phosphorus addition experiment

Abstract

Abstract. Terrestrial biosphere models typically use the biochemical model of Farquhar, von Caemmerer, and Berry (1980) to simulate photosynthesis, which requires accurate values of photosynthetic capacity of different biomes. However, data on tropical forests are sparse and highly variable due to the high species diversity, and it is still highly uncertain how these tropical forests respond to nutrient limitation in terms of C uptake. Tropical forests often grow on soils low in phosphorus (P) and are, in general, assumed to be P rather than nitrogen (N) limited. However, the relevance of P as a control of photosynthetic capacity is still debated. Here, we provide a comprehensive dataset of vertical profiles of photosynthetic capacity and important leaf traits, including leaf N and P concentrations, from two 3-year, large-scale nutrient addition experiments conducted in two tropical rainforests in French Guiana. These data present a unique source of information to further improve model representations of the roles of N, P, and other leaf nutrients in photosynthesis in tropical forests. To further facilitate the use of our data in syntheses and model studies, we provide an elaborate list of ancillary data, including important soil properties and nutrients, along with the leaf data. As environmental drivers are key to improve our understanding of carbon (C) and nutrient cycle interactions, this comprehensive dataset will aid to further enhance our understanding of how nutrient availability interacts with C uptake in tropical forests. The data are available at https://doi.org/10.5281/zenodo.5638236 (Verryckt, 2021).

Phosphorus scarcity contributes to nitrogen limitation in lowland tropical rainforests

“…They observed a clear rhizosphere effect for P, but not for N. The fact that the rhizospheres rapidly took up P, but not N, supports the assumption that trees growing in these study sites are primarily P limited. Soil P availability estimates (Bray‐P), determined before the start of the nutrient addition experiment, suggest very low P availability, typically ranging between <1 and 3 ppm (Verryckt et al, 2022). Reactive N (nitrate + ammonium) availability in these soils exhibited values of 5–25 ppm (Verryckt et al, 2022).…”

“…Soil P availability estimates (Bray‐P), determined before the start of the nutrient addition experiment, suggest very low P availability, typically ranging between <1 and 3 ppm (Verryckt et al, 2022). Reactive N (nitrate + ammonium) availability in these soils exhibited values of 5–25 ppm (Verryckt et al, 2022).…”

“…Adapted from Verryckt et al (2022). Situational map: (A) northeastern part of South America; (B) northern French Guiana with its main cities (circles), and the experimental sites of Paracou and Nouragues (squares); (C) the twelve 50 × 50 m plots of this study at Nouragues–Inselberg, and (D) the twelve 50 × 50 m plots of this study at Paracou.…”

Contrasting responses of fine root biomass and traits to large‐scale nitrogen and phosphorus addition in tropical forests in the Guiana shield

“…Total P concentrations were determined by acid digestion followed by ICP-MS analysis (7500ce model, Agilent Technologies). A complete description of soil chemical analysis can be found in Verryckt et al (2022).…”

Modeling demographic-driven vegetation dynamics and ecosystem biogeochemical cycling in NASA GISS's Earth system model (ModelE-BiomeE v.1.0)

“…The new leaves that are usually measured have much higher V cmax than the mean of the canopy. If the leaves were not specifically chosen, then the mean of measured V cmax is much lower than those used in models, as shown in Verryckt et al (2022). This also indicates that V cmax in current vegetation models is overestimated.…”