Seedling growth responses to phosphorus reflect adult distribution patterns of tropical trees

Abstract

Soils influence tropical forest composition at regional scales. In Panama, data on tree communities and underlying soils indicate that species frequently show distributional associations to soil phosphorus. To understand how these associations arise, we combined a pot experiment to measure seedling responses of 15 pioneer species to phosphorus addition with an analysis of the phylogenetic structure of phosphorus associations of the entire tree community. Growth responses of pioneers to phosphorus addition revealed a clear tradeoff: species from high-phosphorus sites grew fastest in the phosphorus-addition treatment, while species from low-phosphorus sites grew fastest in the low-phosphorus treatment. Traits associated with growth performance remain unclear: biomass allocation, phosphatase activity and phosphorus-use efficiency did not correlate with phosphorus associations; however, phosphatase activity was most strongly down-regulated in response to phosphorus addition in species from high-phosphorus sites. Phylogenetic analysis indicated that pioneers occur more frequently in clades where phosphorus associations are overdispersed as compared with the overall tree community, suggesting that selection on phosphorus acquisition and use may be strongest for pioneer species with high phosphorus demand. Our results show that phosphorus-dependent growth rates provide an additional explanation for the regional distribution of tree species in Panama, and possibly elsewhere.

Nutrient acquisition strategies augment growth in tropical N2‐fixing trees in nutrient‐poor soil and under elevated CO2

“…For example, Cernusak et al (2011) showed variation in the capacity for nodulation among tropical N 2 fixers, Nasto et al (2017) showed that differences in nutrient acquisition strategies between non-N 2 and N 2 fixers were driven by individual species belonging to each functional group, Zalamea et al (2016) and Png et al (2017) suggested that root phosphatase activity is phylogenetically constrained and not related to functional group or N 2 fixation, and Soper et al (2018) demonstrated a lack of a relationship between N 2 fixation, foliar N, and P acquisition among a variety of N 2 -fixing legumes, non-N 2 -fixing legumes, and non-legumes. For example, Cernusak et al (2011) showed variation in the capacity for nodulation among tropical N 2 fixers, Nasto et al (2017) showed that differences in nutrient acquisition strategies between non-N 2 and N 2 fixers were driven by individual species belonging to each functional group, Zalamea et al (2016) and Png et al (2017) suggested that root phosphatase activity is phylogenetically constrained and not related to functional group or N 2 fixation, and Soper et al (2018) demonstrated a lack of a relationship between N 2 fixation, foliar N, and P acquisition among a variety of N 2 -fixing legumes, non-N 2 -fixing legumes, and non-legumes.…”

Plant responses to fertilization experiments in lowland, species‐rich, tropical forests

“…In the growing house experiment, species-specific growth responses to +P increase steadily with the strength of species-level associations with P-rich soils (Zalamea et al 2016). In the growing house experiment, species-specific growth responses to +P increase steadily with the strength of species-level associations with P-rich soils (Zalamea et al 2016).…”

Species‐specific effects of phosphorus addition on tropical tree seedling response to elevated CO2

“…The CO 2 concentration was prevented from overshooting by providing CO 2 in multiple pulses of 2 s interrupted by 5 s without CO 2 injection. Seedlings were watered daily and received 150 ml of a liquid fertilization treatment weekly (as in Zalamea et al, ). All seedlings received a full nutrient treatment including 4 mM KNO 3 , 1.5 mM MgSO 4 and 4 mM CaCl 2 , micronutrients and Fe as ethylenediaminetetraacetic acid iron (III) sodium salt.…”

“…While increasing P appears to stimulate growth rates for most tree species in lowland forests in Panama (Turner et al, ; Zalamea et al, ), low‐P levels do not necessarily imply a community‐wide limitation on productivity; rather, some species thrive on low‐P soils, while others dominate soils with higher P levels (Turner et al, ). In fact, Zalamea et al () showed that the growth of species naturally distributed in sites with high‐P availability was stimulated by P addition in a pot experiment, while species from low‐P availability sites have little or no change in growth when P was added. Furthermore, species distributional associations with soil P did not predict biomass allocation or foliar P when plants were grown at either low ‐ or high‐P (Zalamea et al, ).…”

“…In fact, Zalamea et al () showed that the growth of species naturally distributed in sites with high‐P availability was stimulated by P addition in a pot experiment, while species from low‐P availability sites have little or no change in growth when P was added. Furthermore, species distributional associations with soil P did not predict biomass allocation or foliar P when plants were grown at either low ‐ or high‐P (Zalamea et al, ). Although it is still unclear how some species maintain high growth rates on low‐P sites, this most probably involves mechanisms that promote efficient use or uptake of P (Turner et al, ).…”