Effects of nitrogen and phosphorus availability on the early growth of two congeneric pairs of savanna and forest species

Abstract

In the tropical region, savannas and seasonal forests, both highly diverse biomes, occur side by side, under the same climate. If so, that mosaic cannot be explained solely by climatic variables, but also by fire, water availability and soil status. Nutrient availability in the soil, especially nitrogen and phosphorus, has been postulated to explain the abrupt transitions between savannas and seasonal forests in tropical regions. Plants from these two biomes may present different nutritional strategies to cope with nitrogen and phosphorus limitation. We used two congeneric pairs of trees — each pair with a species from the savanna and another from the neighboring seasonal forest — to test whether savanna and forest species presented different nutritional strategies during their early development. We cultivated 56 individuals from each of these species in a hydroponics system with four treatments: (1) complete Hoagland solution, (2) Hoagland solution without nitrogen, (3) Hoagland solution without phosphorus, and (4) Hoagland solution without nitrogen and phosphorus. After 45 days, we harvested the plants and measured total biomass, root to shoot ratio, height, leaf area, and specific leaf area. Overall, savanna species were lighter, shorter, with smaller leaves, higher specific leaf areas, and higher root to shoot ratios when compared to the forest species. Nitrogen increased the performance of species from both biomes. Phosphorus improved the performance of the forest species and caused toxicity symptoms in the savanna species. Hence, savanna and forest species presented different demands and were partially distinct already as seedlings concerning their nutritional strategies.

Dark diversity at home describes the success of cross‐continent tree invasions

“…Functional attributes that promote efficient growth are usually the same that increase invasion success (Lamarque et al, 2011). Indeed, in forest environments, taller trees with small but nitrogen‐rich leaves allow a high metabolic efficiency by sustaining high photosynthetic rates and low water loss (Paganeli & Batalha, 2021; Paganeli et al, 2020). These nitrogen‐rich leaves may be connected to the mycorrhizal association (Gorzelak et al, 2015).…”

Intraspecific variation in fine-root traits is larger than in aboveground traits in European herbaceous species regardless of drought

“…Furthermore, when considering analogous traits, Weemstra et al (2022) reported that intraspecific variation was greater in root traits compared to leaf traits. Higher ITV in fine-root traits compared to aboveground traits could be due to the heterogeneity in soil conditions and microbial interactions that promote a greater variation within species as individuals uniquely adapt to their immediate soil environment (Paganeli and Batalha, 2021;Weemstra et al, 2022;Spitzer et al, 2023). This also leads to a stronger below-than aboveground competition among conspecifics, arising from differential responses to the heterogeneous belowground conditions over time (Read et al, 2017).…”